Battery Updates and Charging - Solar - Inverters

Topic: Battery Updates and Charging - Solar - Inverters (Read 6272 times) previous topic - next topic

Re: Battery Updates and Charging - Solar - Inverters

Reply #75 – June 18, 2021, 09:43:20 am

Peter,

I like your idea.

For the short term, I'm looking to set up the new 48V House bank with 1 Quattro to just be a replacement for the old House bank and Prosine 2.5 inverter. This will allow me to finally get on the road next month.

But, absolutely. Two 48/5000 Quattro split phase 240V is a nice upgrade. But to get there, I need to do a lot more research. One thing I could do with a second Quattro is to have the option to connect that one to a Lithium battery bank if I wanted to. I would just keep the other one with the charge profile for the AGM Firefly bank. Or, most likely, I will just buy another 8 Firefly batteries. Lithium is nice but at half the cost, the Firefly Oasis are a nice alternative.

If I had gone with Lithium for the House batteries, I probably would have never taken them below 20% SOC, even though it is possible. With the Firefly AGMs, I won't take them below 30% SOC. So a Lithium bank would have only provided me an additional 10% DOD. Because of that, I could not justify paying twice the cost for lithium. But, if I were to expand on the current 928 AH Firefly house bank, then the form factor possible with a Battleborn BBGC3 would make it easier to add more batteries. You're limited with where you can mount Group 31 size, as with the Firefly. Those fit nicely in the battery compartment where the 8Ds used to live, but they would take way too much space any other place in the coach. The weight for a Firefly based battery bank per amp is also almost triple that of an equivalent BBGC3.

So, for now and my planned travels, regular Battleborns 100 AH or 270 AH BBGC3 lithiums would have to come down to about $700 for 100 amp-hr battery and about $2500 for BBGC3. They're a long ways from coming down to that price. That probably won't happen for another 5 years as new solid state and other technologies get introduced.

While expanding the House bank, I do have to worry about the GAWR on the front axle. The weight is not going to be a problem with this first bank of 8 OASIS Firefly and one Quattro 48/5000. But, I will need to weigh the coach and see if I can put a second Quattro and second bank of Oasis batteries before I go there.

If it's okay, I would like to reach out to you at a future time and discuss this idea of a 240V split phase system some more.

Re: Battery Updates and Charging - Solar - Inverters

Reply #76 – June 18, 2021, 10:07:11 am

Look at sokbattery.com their price for a 12 volt 100 amp is $570. There is a dealer in Buckeye, AZ that has sold some and has good feedback.

Re: Battery Updates and Charging - Solar - Inverters

Reply #77 – June 18, 2021, 11:16:57 am

If I was going to do it today I think I would look at the new AIMS 12kw, this is UL and CSA listed, 120 amp charge, 63 amp transfer switch, 40 watt power saver. One unit, easy install.

12000 watt inverter charger - 12kw 48 volt inverter | AIMS Power

Re: Battery Updates and Charging - Solar - Inverters

Reply #78 – June 18, 2021, 04:21:22 pm

Quote from: prfleming – June 18, 2021, 11:16:57 am

If I was going to do it today I think I would look at the new AIMS 12kw, this is UL and CSA listed, 120 amp charge, 63 amp transfer switch, 40 watt power saver. One unit, easy install.
12000 watt inverter charger - 12kw 48 volt inverter | AIMS Power

That's a nice unit. But, as you'll read below, the size of that unit may be a problem for mounting into the bay I have selected for an inverter/charger. Also, having just one inverter/charger, instead of two separate units would not make it possible for me to have two different types of battery banks. With two separate inverters, I could have one with an AGM charge profile and the other driving a lithium profile.

Here is another unit I'm currently investigating. The Quattro 48/10000/140 100/100 120V. Yep, overkill for rving. But, here are my plans:

I'll be building a home base in Florida. Hopefully a place with a garage for the bus. I'm thinking that 2 of the 10KW Quattros and batteries in the RV and sticks-and-bricks, along with the 10 KW diesel generator in the bus would serve nicely as backup power for the house in case of grid down. Also, if a future buyer of the RV does not care for all that power and/or weight in the RV, I could move the inverters and some of the batteries into the sticks and bricks.

I'm constrained with the dimensions of the bay where I plan to install the inverters. I would like to install the inverter/charger in the small compartment behind the pass-thru bay. The passenger side compartment on the other side of the wall from were the compressors, inverter and air valves are currently installed. The 8 House batteries are in the storage accessible from that bay.

From the top lip of the back of the Joey bed to the ceiling in that compartment I have 12". From the top of the Joey bed lip to the floor of the bay, I have another 10". I could remove the Joey bed and have at least 22" vertically in that compartment. Alternatively, I could remove the back edge of the Joey bed and cut an appropriate section out of the floor of the Joey bed so the inverters can get to the floor of the bay. I would leave the front and two sides of the Joey bed so I can still use it as a slider. which is nice. I would probably insert a new "rib" in the Joey bed, towards the back, and in front of the installed inverters for rigidity, and to keep stored items away from the inverter section in the back, as needed. In any case, I would temporarily remove the Joey bed from the RV for now so I can finish the install and start using the RV. That modification to the Joey bed would be a future project. With a modified or removed Joey bed, I could mount the inverters vertically on the back wall. I could frame support for the inverters with some bracket that would rest where the Joey bed is currently finding its own support. The width of that bay is 45"

Quattro 48/5000/70-100/100 120V 17.5" X 13.0" X 9.6" 66 lbs
Victron Energy Quattro 48/5000/70-100/100 | Northern Arizona Wind & Sun

Quattro 48/10000/140-100/100 120V 22.6" X 19.2" X 13.6" 128 lbs
Victron Energy QUA483100100 - InverterSupply.com

AIMS 48V 12KW 240V 23.3 X 16.3" X 7.9" 174 lbs
12000 watt inverter charger - 12kw 48 volt inverter | AIMS Power

Re: Battery Updates and Charging - Solar - Inverters

Reply #79 – June 19, 2021, 10:19:26 am

So I still like the idea of a 48V system. I think I'll be able to mount a 48V inverter in the desired bay. In addition, the 8 Firefly Oasis Group 31 batteries will fit nicely into the battery compartment where the 3 size 8D Gel batteries used to live.

Next problem is the conversion from the 48V bank to 12V for the coach.

I could add multiple DC-to-DC 48V to 12V converters. But, the problem with that is that they take a lot of room, they're limited in their wattage, they generate heat and then I would have to worry about paralleling them to get the power that I need for the coach.

What I'm thinking of doing is the following:

1 - Remove the Prosine 2.5 inverter/charger in the coach to use at home with the 3 8D Gel batteries removed from the coach.

2 - In place of the Prosine 2.5, I will install a Victron Multiplus II 12/3000/120-50 2x120. That unit fits nicely in the same place as the Prosine.

Xantrex Prosine 2.5 20.1" X 15.2" X 6.1" 32 lbs

Victron Multiplus II 23" X 11" X 6" 48 lbs

3 - I will then install a relatively small 12V battery bank, either AGM or Lithium to be charged by the Multiplus II. The purpose for that bank would be to supply the 12V needs of the bus. This way, I won't need 48V to 12V conversion.

4 - Only use the Multiplus II to charge the 12V bank. I don't plan to use the Multiplus as an inverter. That 12V bank would be connected to the 12V distribution in the bus. With this setup, the Quattro would essentially just be responsible for the AC power loads of the bus. In addition, the Quattro would also do the pass-thru for the shore or generator 240V AC into the bus and the Power Assist. The Multiplus and 12V bank would just be responsible for the DC loads.

5 - Future Solar MPPT charging for both the 12V and 48V banks.

6 - I still have to figure out the AC power into the Multiplus. I would like the 12V bank to be charged by shore power when available or by the generator when not.

I will probably add a manual switch to connect the output AC from the Quattro to the AC input of the Multiplus as a last resort to charge the 12V bank at a penalty of loss in efficiency.

Question: How many amps minimum should I use for the 12V bank? I would like to boondock and Harvest Host on many days in a given year. I also don't want to have the generator running for more than an hour or two each day.

I'm thinking, at a minimum, 500 AH for the 12V bank? Worst case, I can always pipe the juice from the 48V bank to the 12V bank. Any ideas?

Re: Battery Updates and Charging - Solar - Inverters

Reply #80 – June 19, 2021, 11:39:35 am

For wiring the 48V bank, I'll use as large a cable as practical and select the length of cabling between the batteries so that I could always rewire the 48V bank into a 12V bank system. This way, I could connect the Multiplus II to it and remove the Quattro 48/10000 if a future buyer of the RV does not care for that expensive setup. Removing it from the RV would also make sense since the Quattro already has the additional purpose of serving as part of the sticks-and-bricks backup power.

But, I'm now thinking that I would just have 1 Quattro in the bus. I think that it makes more sense to have more batteries rather than use space and weight in the RV for a second Quattro. That one 10000 VA would be more than enough to satisfy the AC power needs while boondocking. The 140 Amps of charging from the 48V output of the Quattro, for 2 or even 3 strings of batteries from one Quattro should be plenty. Not sure yet what having a second Quattro in the bus and 240V AC would get me while rving.

I do plan to keep the propane refrigerator for now. Don't see a strong reason to replace it. I have a 2 burner propane stove that the DW prefers to electric. I have Aquahot so that will burn up diesel to take care of heat and hot water while boondocking. So one leg of AC power while boondocking to power at least 1 air conditioner, that should be fine. Time will tell.

A second Quattro setup at the home base, connected in a split phase with the one in the bus would take care of the 240V backup needs of the home base. That second Quattro in the home base may benefit from long lived Lithiums for its bank.

Re: Battery Updates and Charging - Solar - Inverters

Reply #81 – June 21, 2021, 07:23:45 pm

If you do a search you might find the posts of Tim who did the 48 volt set up. The bad news was in the end he couldn't sell the coach as it was too complicated. He listed it for months on the forum.

Follow this thread

48 VOLT SOLAR LITHIUM SYSTEM

Re: Battery Updates and Charging - Solar - Inverters

Reply #82 – June 21, 2021, 09:30:17 pm

Quote from: craneman – June 21, 2021, 07:23:45 pm

If you do a search you might find the posts of Tim who did the 48 volt set up. The bad news was in the end he couldn't sell the coach as it was too complicated. He listed it for months on the forum.

Follow this thread

48 VOLT SOLAR LITHIUM SYSTEM

I read Tim's thread. I wonder how Tim is doing or if he is still out there enjoying the RV life?

But, absolutely, the only reason that I'm considering a battery bank for the RV with more than 20 KW-hr and a 48V 10000 VA inverter is because I want the dual use as a backup power system for the home base.

So, yes, most likely, I would remove the 48/10000 Quattro and about 10 KW-hr of batteries before selling the coach. Most people don't need or want that much weight or expense. But, if a future buyer of the coach wants it with all the goodies, I could leave it all in the coach. But, most likely, the 928 AH from the 8 OASIS Firefly and the Multiplus II 12/3000/120 2x 120 to be left with the coach would be fine for a resale. In that case, I would just need to rewire the Fireflys for 12V operation and connect the Multiplus II and AC pass-thru to the coach.

My planned battery changes may have to wait about a month or two. It turns out Victron and all inverter suppliers that I have checked have the Multiplus II on back order. Worst case, I could continue to operate with the 2 8D Gel batteries still in the coach and with the Xantrex 2.5 for now. Those old 8Ds are not good enough anymore for boondocking, so I will just need to find some local parks with power hookups for now.

Re: Battery Updates and Charging - Solar - Inverters

Reply #83 – June 22, 2021, 08:36:20 pm

Peter well I admire your dedication I really think you're overthinking it a bit. Or should I say overcomplicating it. I understand exactly where you're coming from and what's your wants and needs are. Or at least I think I do. I think your choice of the Firefly batteries is top. I love those batteries or at least the idea of them never having used them myself. On my last sailboat I thought about using those but I used a thin plate pure LED batteries instead using the version at Sears had on their DieHard Marine series. And I do agree that lithiums on for everybody. I'm just not really sold on the 48 volt thing. I'm not even sold on 24 volt. I think it just makes things a little bit too complicated. I have a victron multiplex 3 kw inverter along with 600 amp hours of victron lithium batteries. Along with 1400 watts of solar on the roof and a victron mppt controller I'm able to go 2 to 3 days with normal use and for if I really push it with a little to no sun. That's on a propane less coach. So I use either diesel or electric for everything. Right now I did start the generator because I wanted to run both air conditioners for a couple hours before it cooled off a bit. And I figured I would top the batteries up to around 80% while I was at it. And it's good to run the generator once in awhile to exercise it anyway. I would have liked the Quattro 5K inverter charger but don't usually find that I have a need for it. And at the cost of that baby I think it's Overkill for me.
Anyway I will follow your thread with interest. Good luck and hope you get it worked out. By the way my lithium ion batteries are in the compartment where the splendid washer dryer used to be. It's not where I would have put them, but where are previous owner told AM solar to put them. But they are in a good spot there out of the way of the Bay. I don't have to worry about it being too cold although the heat generated from them sometimes can be a warm. I do have an AC duct that cools that area very nicely.
Bob

Re: Battery Updates and Charging - Solar - Inverters

Reply #84 – June 22, 2021, 11:42:00 pm

Hi Bob,

There are 2 appealing ideas that are possible with the battery setup that I'm thinking about implementing:

1 - I like the idea expressed by many in this forum of having the option of running at least 1 AC while rolling down the road.

2 - A backup power system for my home base in Florida is a must. Sure, a house could always have a diesel or propane generator as well as a tank full of fuel and maybe a Tesla Powerwall setup. But, with the RV parked at the house; the generator, the tank for the diesel and the batteries are already inside the bus. Very convenient. You would just need to add another 48/10000 Quattro and give it its own battery bank at the house to complete a 240V split power backup system for the homestead. That would be almost the equivalent of having 100 Amp 240V split service from the power company into your house.

True, you don't have to go with 48V. A watt-hr is a watt-hr, whether it comes from 12V or 48V. But, the first obvious consequence is that you'll be moving 4 times the current through some of the RV cabling for 12V compared to 48V. The not so obvious is that the 48V Quattro is charging at 140 amps. The 12V Quattro is doing 220 amps while charging. That is 6720 watts of charging for the 48V charger vs. 2640 watts for the 12V unit. That is, it will take you 2.5 times longer to charge the 12V bank than the 48V bank. And, if you were using a Multiplus II 12/3000/120-50 2x120 to charge a similarly sized 12V bank, it would take about 4.5 times as long as with the 48V 10000 VA Quattro. So, charging 12V banks may not be a big deal while on shore power or solar, but annoying and expensive with a generator. Another important and not so obvious fact is that you're not going to get 10000 VA with a 12V inverter. Only a 48V inverter like the Quattro 48/10000 will do that. The reason that is important is because now you could pump both 120V legs of your RV breaker panel with 5000 VA each. You would just be limited with what you can do by the size of the battery bank in the bus and not by the power from the inverter.

Side Note: With the above Quattro feeding both legs of the AC panel you don't have a split setup. In this case, you will have to concern yourself with the sizing for your neutral wire going back to the inverter, since in a non-split system, at worst case, the neutral will be carrying the current of both L1 and L2 hot wires.
DISCLAIMER: I'm not an electrician. I don't even play one on TV. So before following any advice from anyone in here, for any of the entries in this thread, please consult with an actual electrician!.

Here is a quick calculation for the first idea of running at least 1 of the 15000 BTU airs in the bus while driving. Note: I haven't actually connected a watt-meter to the air conditioner to verify this. This is just from past experience with other ACs.

A 15000 BTU air will most likely operate with less than 1700 watts. That's just over 15 amps at 110V. The 1700 watts turns into about 1800 watts because of the efficiency losses through the system. That turns into less than 40 amps out of a 48V battery bank.

One possible setup: A 270 AH 48V bank, taken down to 20% SOC will run that 15000 BTU air for at least 5 hours. Five hours of comfortable temperature and relatively quiet driving. Also, with some solar on the roof you could be very comfortable at Quartzite overnight, without having to run the generator much. I could see running the 10 KW generator early in the morning to pump the batteries in bulk mode for about an hour. The Quattro 48/10000/140 can pump that 48V bank with 140 amps in just 1 hour. Then, for the rest of the day, you would just let the sun take care of absorption charging for the next sunny 5+ hours.

Now, all of this does not come cheap. Unfortunately, to have a battery bank with 270 AH at 48V, which is consistently taken down to 20% SOC means Lithium. That bank (4 BBGC3) and a 48/10000 Quattro will set you back 13+ coach bucks (6/23/2021 pricing).

Update (7/1/2021): I have decided to actually implement and try this 1 AC on while driving. But, not with Battleborn Lithiums, which are about double the price. Instead, 8 Firefly OASIS, set up as 2 strings of 48V and driven by the Quattro 48V/10000/140. That setup is about $10,000 total. About $5000 in just batteries. That is 232 AH at 48V. Taken down to 30% SOC, it means about 4 hours of one of the15000 BTU ACs running while off grid.

Re: Battery Updates and Charging - Solar - Inverters

Reply #85 – June 23, 2021, 10:26:03 am

While we never run the generator at campsites, if we happen to be traveling where it's hot, the generator might run all day for the ACs while going down the road. For those with dash air, it produces more BTUs that one roof air. Think it's rated at 17K BTU.

Since Q is in January, a little heat at night might be needed rather than AC in the day.

$13K for batteries seems like a bad fantasy to me. We paid $210 total for all six of our AGMs. You can buy a decent Foretravel for $13K.

I noticed last week at June Lake that the only generators running were low noise gasoline generators. The parks are enforcing the 60db limit in some locations, 68db in others (at 50 feet). Our 10Kw is well over 80db at 50 feet.

We have enough solar to run an evaporative cooler and since we live in the West where the humidity is low, the efficiency would be pretty good. Running at night is not possible but most of our summer campgrounds are at high elevation so never hot once the sun goes down. Scott is stuck with oven like temps at LV even at night in summer. No envy here.

Pierce

Re: Battery Updates and Charging - Solar - Inverters

Reply #86 – June 24, 2021, 07:41:42 pm

I was poking around the interwebs and here is a very interesting article regarding discharge of AGM batteries that I think ties into this discussion.

AGM battery Depth of Discharge myth busted

Re: Battery Updates and Charging - Solar - Inverters

Reply #87 – June 25, 2021, 07:23:15 am

Quote from: prfleming – June 24, 2021, 07:41:42 pm

I was poking around the interwebs and here is a very interesting article regarding discharge of AGM batteries that I think ties into this discussion.

AGM battery Depth of Discharge myth busted

Re: Battery Updates and Charging - Solar - Inverters

Reply #88 – June 25, 2021, 07:24:52 am

Quote from: prfleming – June 24, 2021, 07:41:42 pm

I was poking around the interwebs and here is a very interesting article regarding discharge of AGM batteries that I think ties into this discussion.

AGM battery Depth of Discharge myth busted

The "how to lie with statistics" from above leaves out one fact. That fact is as your AGM battery ages with increased cycles, the available ah also decreases. So the articles conclusion is false. If you want best wet deep cycle life total ahs, maybe use BK or Lifeline gel as the FT came with.

The best source I've found over the years is the Lifetime Tecnical manual, I've linked below.

For many now Lifepo4 will be their answer to budget, needs, and experience. I'm generally plugged in and have 1800 watts of solar, so O'Reillys AGMs still meet my needs.

https://www.oreillyauto.com/detail/c/fleet-heavy-duty/battery-accessories/deep-cycle---marine-batteries/220f7dcd7121/super-start-fleet-heavy-duty-battery-group-size-8d/ssbl/agm8dt975

8G8D | MK Battery 12v 225 AH Deep Cycle Gel Cell Battery with Automotive Post

Half of what you read on the web is not true. For you, other than this false use of facts, do your own research, do not rely on one post or repeated myths, only you know your budget, needs, and experiences.

6-0101F (Lifeline Technical Manual) Final 5-06-19 - Lifeline

Re: Battery Updates and Charging - Solar - Inverters

Reply #89 – June 29, 2021, 03:28:19 pm

Making Progress:

1 - I removed the 57.5" X 43.25" X 8" Joey Bed from the bay where the battery compartment is. That Joey Bed is 81.5 lbs.

2 - I removed the left metal framing rib that the Joey Bed was riding on so I could get the remaining 2 8D batteries out.

3 - Using some pry bars purchased at Harbor Freight I pulled the 2 8D batteries out of the lower shelf in the battery compartment. I got one of them charging and powering the bus while parked. Both of them will stay in there for now so I can make it to a campground on my maiden voyage with the bus, while I wait for the Multiplus II. ETA on the Multiplus is end of July. The Xantrex 2.5 will not properly manage the Firefly Oasis charging profile.

NOTE: It goes without saying, make sure you look after your fingers and hand while trying to get those batteries out of the battery box. Too easy to crush them. I came close to doing some damage.

The next thing for me is to clean the battery compartment, rustoleum it and manufacture some frame so I can put a second shelf in there. The one shelf in there will not work for 4 Group 31 batteries. So eventually there will be two shelves of 4 Firefly Oasis AGM batteries on each for a total of 8 AGMs and 232 AH at 48V. They will be connected in two strings of 48V each and driven by the Quattro 48/10000/140-100/100 120V. But, before the Quattro, four of those batteries will be wired as a 12V bank to be driven by the Multiplus. Quattro comes later.

Re: Battery Updates and Charging - Solar - Inverters

Reply #90 – July 01, 2021, 10:24:26 am

Took the metal 8D battery shelving out of the battery box. That shelving is held in place inside the battery box by 8 Torx screws. The inside of the bottom floor of that shelving is 21.75" (L) X 19.25" (W) with room for 11.5" in height. The top shelf is 20.5" (L) X 10.5" (W) with room for 11.5" in height.

The OASIS Firefly batteries are 13.6" X 6.75" X 9.4".

I put 2 of the 8D batteries back into the now empty battery compartment. Each of them are getting charged by Deep Cycle Chargers. The empty battery compartment is 23.5" (L) X 23.5" (W) X 24.5" (H)

I'll have to build an appropriate 2 shelf box so I can fit 8 OASIS batteries inside that compartment.

Re: Battery Updates and Charging - Solar - Inverters

Reply #91 – July 07, 2021, 01:12:54 pm

I continue to work on my battery setup. Some discussion points:

1 - I have read the manual for the Firefly OASIS G31 batteries in detail. Here are some things that I will be worrying about.

- Manufacturer says a fully charged OASIS has a voltage of about 12.90V.
- They require that the OCV (Open Circuit Voltage) of the battery be above 12.70V before putting them to use in a bank.
- If not at > 12.70V, charge at 14.40 V for 12 hours.
- Obvious recommendations for restraining the batteries and putting boots on at least the "+" terminal. They also recommend at least 0.6" but optimum of 1" of breathing room between batteries. They also recommend mounting the batteries so air can flow underneath them.
- 16 ft-lbs of torque for cabling. Terminals are 3/8-16 UNC.
- It is normal for batteries to gas for first few charging cycles.
- If vents leak acid, wipe with alcohol and torque vent caps to about 1.5 ft-lbs.
- Max. Discharge Current: 0.7 C. Batteries are 116 AH, so about 80 A.
- Max. Charge Current: 0.5 C. So about 58 A. I plan to charge the 48V bank at about 0.4C. The 12V bank will need some more TLC, as per discussion below.
- Bulk phase: 14.4V with temperature compensation until charge current is 0.5A
- Float phase: 13.4V - 13.5V
- The charging profile needs to "reset to bulk phase" if charge voltage is < 12V for 1 minute.
- Periodic fast charging recommended, once per week or at least once a month, if deep discharges have occurred or if the charging has been at less than 0.2C. The recommended fast bulk charge is at 0.4C followed by a 24 hour float at 13.5V.
- Peukerts Constant: 1.07 - 1.12
- Temperature coefficient: 24 mv / degrees C.
- Operating Recommendations
- Battery parameters specified at 77 degrees F.
- If charging below freezing, limit charge current to 0.1 C
- If temperature is about 15 degrees F above 77 consistently it may cut the life of the batteries in half. This is a common problem with lead acid batteries and something I will do something about, if possible.
- Batteries do not have to be fully charged on each cycle for batteries to be protected. This is one of the nice things about the Firefly Carbon mesh technology. But they do need " restoration" now and then.
- Restoration process: From a deeply discharged state, charge at 14.4 V until the charge current gets down to 0.5 A. Then, run a Float charge at 13.5 V for 24 hours. Then, fully discharge to 10.5V and repeat the bulk and float charge cycle once more.

Lots of things above to worry about.

2 - I will have pictures later, but for this discussion, here is what I'm doing to care for those expensive batteries:

For 48V bank:

- I plan to have 1" of plywood (2 pieces of 1/2" plywood), sized 30" (L) X 41" (W) resting on top of the bottom of the 2 metal "L" supports for the two side railings the Joey bed used to slide on. This way I won't need to find any new support points for the weight of the batteries in that bay. A 3/4" piece of plywood resting underneath the 1" plywood and on top of the carpeted floor of the bay will limit the range of the flexing of the 1" plywood while driving. The flexing of the 1" support plywood will be good for absorbing some of the shock while rolling over potholes. The 3/4" plywood just held in place with some Velcro. No need to drill the bottom of the bay for that. The 1" plywood held in place with appropriate bolts, washer/lock washers and nuts, at 4 corner points. The bolts installed through the metal "L" side rails. All plywood will be sealed with MinWax sealer and painted black with some low VOC paint.
- I plan to have a 1/2" standoff underneath the 4 corners of each battery to provide for ventilation under the batteries. Three batteries fit across the 41" width of the plywood when placed end to end. Batteries are 13.6" (L) X 6.75" (W) X 9.4" (H). I will then leave 1" of spacing between two strings of 3 batteries. For now, there will be a total of two string of 4 batteries each for 232 A at 48 V. The Quattro will fit nicely in front of that setup.
- I will buy eyelet screws to go into the plywood and use them with appropriate straps to secure each battery in place.
- Note that the 48/10000/140 Quattro will have no problems supplying a 0.4C of charge to each string of 48V. I have planned for a possible third string in the future.
- I will cover the battery terminals with boots. Good quality marine 4/0 tinned copper cabling and copper lugs will be used throughout.
- I'm still researching the selection of appropriate bus bars, fuses, switches, and Victron family of Smart Shunts, Cerbo GX and Color display.
- For the issue of bay temperature control, I'm looking at something like a Flair Smart Vent and their wireless hockey puck thermostat. The vent could be installed under the sink area in the kitchen and provide a way to maintain the air in the battery bay underneath, as close to 77 degrees as possible, assuming that is what the cabin is running at. A better alternative to the Flair Vent may be simply a unit with built in fans and a thermostat. Something like the $60 AC Infinity AIRTAP T4. I would install that with the finished vent and built in thermostat into the battery compartment. I would then wire that under the kitchen counter, as appropriate.

3 - For 12 V bank

The 6 batteries for the 12 V bank have some unique issues.

- The charger for that bank will be a Multiplus II 12/3000/120-50/50 2x 120V.
- Because that charger is limited to 120A of charging, I will break the 6 batteries into 2 battery banks, each with 3 batteries. Both banks to be isolated from each other by switches, to either combine them or just charge one bank at a time during a "restoration" charge cycle.
- The option to be able to isolate the 2 12V banks is so I can provide a solid 40A of charge to each battery during "restoration" battery charging. Now and then, I could connect an AC to the Multiplus while driving, deeply discharging that bank. So I suppose, sometimes, I could be driving with both ACs on. Once I'm on shore power, I would start the restoration process. I would set the switches so the Multiplus deeply charges just one of the string of 3 batteries. Then do the same for the other 12V bank.
- While restoring one of the 12V battery banks, the other bank is switched so it continues to provide for the 12V needs of the coach. Then, I can switch things so the other bank can be restored. I plan to write myself a check list so I can consistently and correctly complete this process of battery management.
Note: All this is a lot of work in an attempt to give the Firefly batteries a long and healthy life. I suppose Battleborn Lithiums with their built in BMS do not need all this hands on, although they do need some. But then, Battleborns are about twice the cost of the Firefly for similar practical performance. In the end, it's all about doing whatever makes each one of us happy. We all have a budget and priorities on what projects need funding.
Sidenote: Is anyone here planning to go hybrid with a toad? I just found out that Jeep may be releasing a Hybrid version of their Gladiator truck for 2022. Jeep already has a hybrid Jeep Wrangler, their model 4xe. But, I'm looking at the Gladiator truck to use as the toad for better towing capacity and payload with the Gladiator. My current toad, a Jeep Wrangler is getting old and could use replacing. A Rubicon Hybrid Gladiator will not be cheap. So replacing the current toad is an important project needing funding. No need to use some of the limited budget on super expensive Lithiums for now. DWMYH.
- The 6 batteries for the 12V bank will provide a total of about 700 AH for the 12V distribution. They will be mounted in the battery compartment used by FT for the 8D batteries. I will probably remove the access panel from that compartment so those batteries can also live in a cool 77 degree environment.
- Batteries to be strapped, separated by about 0.5" and on standoffs.

The Firefly OASIS batteries are specified for 3600 cycles at a 50% DOD and 1000 cycles at a 20% DOD. I plan to keep both banks above a 30% DOD daily. That should give me about 1500 charge cycles. That's 4 years of daily cycling. Most likely, since I will have relatively large banks, I may get 6 to 8 years out of them. By then, who knows where battery technology will be.

Note: By installing the 48V bank for the 120V needs of the bus inside one of the bays, I could always expand the 48V battery bank. This is because the Quattro 48/10000/140 can handle a lot of charging. The 12V bank with 6 batteries, at about 700 AH should be plenty for the low voltage needs in the bus.

Article on Firefly OASIS: Firefly Carbon Foam Batteries Are Great, But Read The Fine Print

Firefly OASIS Battery Manual: https://www.emarineinc.com/Shared/pdf/Battery/Firefly-Oasis-12V-G31-Users-Manual.pdf

Yep, lots of work. Is it all worth it? Only someone like Socrates could answer such deep questions. Unfortunately, he is still dead!

Re: Battery Updates and Charging - Solar - Inverters

Reply #92 – July 11, 2021, 10:26:04 pm

Preliminary design of custom framing for installation of 6 battery 12V bank. The two 12V banks to go inside the old battery compartment. That compartment at 23.5" X 23.5" X 24.5"

I put enough of the design into a 3D CAD package so I could visualize it and get a list of items to purchase for the build.

1 - The wood battery box will rest on 2 pieces of 22.5" 1 X 2 lumber at the same spot as the support provided for the welded metal box from FT and using the same 8 TORX machine screws (1/4" -by 1") provided by FT. The screws recessed so only 3/8" of thread comes out the bottom of the 1X2 board. This 0.75" vertical offset from the floor of the battery box will keep all the weight on the framing of the RV and not on the in-between RV framing pieces at the bottom of that battery bay.

2 - On top of that will rest a solid wood floor of 1.25" X 5.5" lumber. Four pieces mounted on top of the 1 X 2.

3 - Three batteries will go on top of the 1.25" X 5.5" boards, loaded towards the right of the wood box.

4 - 2 X 4 framing, used as columns for the upper shelf decking, at a height of 10.5" tall will rest on top of the 1.25" X 5.5" flooring. Batteries are 9.4" tall. On top of the 8 columns of 2 X 4 framing there will be 1" plywood for the other 3 batteries. Those 3 batteries will be loaded towards the left wall of the box. This is so I will have room on the right wall, 2nd shelf, for fuses, bus bars, 2 selector switches, shunts, etc.

5 - The 2 X 4 support pieces for the 2nd shelf decking will be reinforced by an "X" pattern of 1 X 2 cross pieces to give the second shelf rigidity (see one sample in one of the 3D pictures). A picture of the empty battery compartment is also attached.

6 - I'm leaving 0.5" along the perimeter of the inside of the battery compartment so air can circulate.

7 - There will be spacing between the batteries for air circulation. There is also space between the 1.25 X 5.5 board pieces. The RV flooring of the battery compartment already has two breathing holes provided by FT. Batteries will be strapped individually by attaching straps to stainless Eyelet screws into the wood flooring.

8 - All lumber will be sealed from moisture and painted with low VOC latex paint.

9 - Other details to be described later.

Some visualization pictures from the 3D CAD attached. The RED surface in one of the pictures represents the flooring in the now empty battery compartment.

Re: Battery Updates and Charging - Solar - Inverters

Reply #93 – July 12, 2021, 01:07:54 pm

Just use treated, ground contact rated lumber and treated deck boards. No need for paint or sealing.

Deck boards are nominal 5/4" but are about 1-1/16". 1" plywood is rare. If the second level is 7/8" 48/24 rated waterproof floor sheathing, on 24" centers you are approaching load limits with 3 - 75 lb batteries and an unsupported front edge, even worse with ony the sides supported. I recall the box is wider than the 22.5 inches between supports at 24" on center. This is not just a static load situation but dynamic loads driving down the road increase stress and deflection. You have to provide a battery hold down as well

Maybe a steel solution would be better.

Or use the box for something else and shorten up the joey bed by a foot or so and put your batteries where the end of the joey bed would have been. This is not an uncommon solution and gets your batteries closer to power connections on the other side of the wall.

All of this would be better done after a year or more of real world experience.

Re: Battery Updates and Charging - Solar - Inverters

Reply #94 – July 12, 2021, 01:54:42 pm

Got to agree with Roger. Steel would be my choice but I also think experience over time is a good teacher.

Pierce

Re: Battery Updates and Charging - Solar - Inverters

Reply #95 – July 12, 2021, 04:53:26 pm

Quote from: Roger & Susan in Home2 – July 12, 2021, 01:07:54 pm

Just use treated, ground contact rated lumber and treated deck boards. No need for paint or sealing.

True, except I already had a lot of other lumber around. Have you priced lumber lately?

Quote from: Roger & Susan in Home2 – July 12, 2021, 01:07:54 pm

1" plywood is rare. If the second level is 7/8" 48/24 rated waterproof floor sheathing, on 24" centers you are approaching load limits with 3 - 75 lb batteries and an unsupported front edge, even worse with only the sides supported.

I'm planning on stocking two pieces of 1/2" plywood. The drawing does not show the complete design. There will be 6 of 2 X 4 on the left side supporting the 3 batteries on the top shelf, about 6" on center. 1 X 2 cross braces will be used to stiffen the deck.

Quote from: Roger & Susan in Home2 – July 12, 2021, 01:07:54 pm

This is not just a static load situation but dynamic loads driving down the road increase stress and deflection. You have to provide a battery hold down as well

Yes. Batteries will be secured from moving. Front of box will have multiple 2 X 4 dropped in front of the batteries to provide a cage to prevent catastrophic ejecting of batteries into the bay in case of crash.

Part of the bay in front of that battery compartment is already set aside for a 48V bank and Quattro inverter.

Quote from: Roger & Susan in Home2 – July 12, 2021, 01:07:54 pm

All of this would be better done after a year or more of real world experience.

The time to plan to enjoy life is Now. Unfortunately, a lot can change in life in a year when you pass the age of 60.

Re: Battery Updates and Charging - Solar - Inverters

Reply #96 – July 12, 2021, 05:46:24 pm

I still plan a lot for today and lots of tomorrows and I'm 78. I figure the fountain of youth vaccine is just around the corner so keep on planning/doing and will keep going to at least mid century.

Pierce

Re: Battery Updates and Charging - Solar - Inverters

Reply #97 – July 12, 2021, 06:51:53 pm

I'm changing how I plan to strap down the batteries. I was going to do ratchet types of straps, but with those straps, it may be required to check them now and then in case they need adjusting.

I have ordered a regular metal battery holder to try out and see how well it may work. An adjustable one so it fits the Group 31 battery. I may have to cut the thread end so it fits in that compartment. The anchor points in the attached picture below, screwed to the wood by the batteries could be used with the straps.

Amazon.com: Uriah Products UV002500 Adjustable, Universal Crossbar, Battery...

The rubber bumpers in the picture may work well placed under the 4 corners of the batteries to raise it and help with their cooling.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Battery Updates and Charging - Solar - Inverters

Reply #98 – July 13, 2021, 10:26:22 am

Roger and Pierce,

Yes. You guys are right. After more thinking about this, steel will indeed be needed for some of the parts in the assembly. The two 0.5" thick support pieces that sit on the RV framed section of the battery bay floor will have to handle about 450 lbs. I would like to make those two bars out of stainless steel.

I'll get in touch with an online machine shop and see if they can manufacture what I need.

I think I'll size the stainless steel bars at 0.5" thick X 1.25" wide X 22.5" long.

Each of those bars will need 5/16 through holes for the 4 Torx screws and 4 threaded holes for mounting the wood flooring. I will also like to recess the Torx screws so the weight from above is on the bars and not the screw heads.

Where do you guys get your machining done?

Until I can get those bars made, I'll install the 12 V banks where the 48V bank will eventually go. It looks like I'll have to get into welding and purchase better metal working tools.

Re: Battery Updates and Charging - Solar - Inverters

Reply #99 – July 13, 2021, 10:50:28 am

Plain steel either painted or powder coated would be fine. Stainless is great for the fasteners. Stainless is tough to saw, drill, etc.

I do all my drilling, cutting, welding here at home. A HF 64 1/2" metal cutting band saw is not expensive and does a great job. Same with a drill press. I did toss the chuck and replaced with a Jacobs chuck.
I bought but tossed a HF powder coating gun and bought a 100Kv unit direct from China for about $350 delivered. Made 3 ovens, one small electric, one out of an RV oven and one is a recycled golf clubhouse stainless commercial range. The powder is really cheap. Easy and fun to do.

Pierce

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