Solar Panels and the Concept of Separate Chassis/House Batteries

Topic: Solar Panels and the Concept of Separate Chassis/House Batteries (Read 1156 times) previous topic - next topic

Solar Panels and the Concept of Separate Chassis/House Batteries

August 28, 2014, 01:43:42 pm

I've been giving some thought to the issues surrounding solar panels, battery banks, generators and the way we've "always done things".

On our little 36' U225 battery space is at a premium. We have room for two "house" D8 batteries wired in parallel and at the present time we have two "red top" starting batteries (also wired in parallel). These two battery banks can be connected together by the boost switch (and associated solenoid) but in general they are kept separate to protect the starting batteries from becoming depleted and being unable to start either the engine or the generator.

But with solar panels the necessity to be able to start the engine and/or generator just to recharge the batteries disappears. Wait 'til the sun comes up, connect the solar system to the start battery, and in a few hours the generator can be started to augment the charging.

But real world with solar generally means that unless you have a defective battery there is really little danger of having no power left in the battery bank. Those little solar thingies just keep on keeping on as long as there are photons to work with.

I'm starting to think that I could simply use three 8D batteries and use them in parallel for whatever I need the power for. Starting, refrigerating, reading, etc.

The boost solenoid might be an issue but I remember that Brett used marine-type battery switches to shuffle the power around instead of (or maybe in addition to) the boost switch. I think I'm going to approach the system in this way rather than in the classic way. I think it will better maximize the space on the unit as well as increase potential power usage.

Craig

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #1 – August 28, 2014, 01:51:42 pm

Craig, Wyatt has already done the getting rid of one bank of batteries and uses the one for all systems on his coach. I do not think he has solar either. Check his posts out so you can see what he did.
John H

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #2 – August 28, 2014, 02:04:16 pm

Quote from: John Haygarth – August 28, 2014, 01:51:42 pm

Craig, Wyatt has already done the getting rid of one bank of batteries and uses the one for all systems on his coach. I do not think he has solar either. Check his posts out so you can see what he did.
John H

Wyatt has every inch of his roof in solar panels.

I only slightly exaggerated.

By the way, the towed vehicle and jumper cables are always available...just in case.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #3 – August 28, 2014, 02:21:03 pm

I stand corrected on Wyatt's solar then
JohnH

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #4 – August 28, 2014, 02:38:12 pm

Remember, the alternator we have is not a truck alternator as it has a higher voltage for the isolator. It has a small sticker (if still there) that identifies it. Good to clean the top of the alternator and take a digital photo of the part number/specs to keep on the iPad, laptop so you have the right part number if necessary. A good electrical shop should be able to modify/set other alternators to work.

If anyone is not using the dash air, it would be very easy to just install another alternator where the compressor is and make a short run to the engine batteries. Could have two systems with a switch or solenoid to link them in case of a failure. On a side radiator Detroit, you could also make a mount off of the HD bracket that is used for a rear fan assembly and use the crank pulley with it's many V belt grooves.

Pierce

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #5 – August 28, 2014, 02:48:03 pm

Quote from: Pierce & Gaylie Stewart – August 28, 2014, 02:38:12 pm

Remember, the alternator we have is not a truck alternator as it has a higher voltage for the isolator.

That's a good point. Another issue is that the voltage regulators on the alternators is not very sophisticated. An entirely different alternator/regulator system would be a good idea; especially for those days where your driving a lot.

I've given some consideration to having the alternator only charge the start batteries and simply letting the Classic 150 take care of the house bank. But a better "smarter" regulator for that system makes more sense.

Craig

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #6 – September 06, 2014, 11:55:37 am

Craig, I just bought Bill & Sue's 1993 U225 and am about to install a couple 250 watt solar panels and a 40 am MPPT controller on my coach. Where did you mount your solar controller and how did you route the cables coming from the panels?
My coach currently has only two 8D's which I was told are two years old and I am considering whether to simply add another 8D to the existing battery compartment or put in a new bank of house batteries on the Joey Bed cargo tray on the opposite side of the coach. Any thoughts or comments from anyone on this would be appreciated.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #7 – September 06, 2014, 12:41:20 pm

Dakota, (love name and icon)

Unless you have a lot 200ah+ overnight like some do with cpap machines you may want to consider the following.

I realize you specifically addressed Craig and he by far has more knowledge than I. But, my PO might best even Craig, he did some extensive cost-vs-time calculations, # of charge cycles etc based on 900w of solar and 1 AGM.

Answer 8-9 years with 220 nights use. So with 2 batteries already, well you can do the math. Cost point with him was agm in 2000 was $280, so in 8 years his battery cost of replacement was $35/yr, since it is recommended to have matching (same time) batteries.

Take a look at your intended use and draw requirements, do some math it might surprise you and save you around $500 bucks.

Also consider the older amp draw tvs, microwaves, lighting changes to led, better inverters, etc.

Also look at a Solar Jedi Master postings from Wyatt Sabourin and Jon Twork they have parasitic draw down to less than 2amps

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #8 – September 06, 2014, 01:04:24 pm

Welcome to the U225 family.

I have a floor plan that does not include a full dinette (just a half dinette at the forward end of the kitchen sink counter) with a cabinet next (aft) of the entryway. So my refrigerator is on the co-pilot (curb) side of the rig with a cabinet that used to contain the built-in vacuum cleaner below the refrigerator.

The refrigator vent made it very convenient to route cables from the combiner box (where the panels connect on the roof) down and directly into the top of the clothes closet that is directly aft of the refrigerator. My breaker box is mounted at the back (outboard wall) of this closet) and the wires continue down into the false floor at the bottom of that closet. (The Wineguard TV amplifier is located under this false floor, by the way.)

From there the wires route directly forward into that vacuum cleaner cupboard where I have positive and negative busbars mounted on the outer wall. This cupboard also contains the inverter (mounted vertically on the aft bulkhead).

The MPPT charge controller (Classic 150) is mounted over the hole where the hose to the vacuum cleaner would be inserted. It is outside the cupboard because, really, that's the only place I could find that would let me route cables conveniently and also let me see the LCD screen of the controller (if I lay on the floor... it's no problem getting down there... I can just fall down; getting up is the issue).

This arrangement turned out to be convenient and allowed short cable runs. The vacuum cleaner cupboard is directly over the battery bank in its storage bin.

The inverter and the solar charge controller both connect (via #6 cables) to the the positive and negative busbars in the cupboard and then #4 cables connect to the house battery bank (via a 200-amp fuse). I did not install a breaker in that circuit... but might in the future.

I have two, 240-w 24vdc panels in series to the Classic 150 and two Unisolar panels in parallel that do not want to play nice in the circuit... probably because I might not understand everything I know. At any rate, I have a 20-amp MPPT controller I bought before Pierce clouded my.... er, changed my mind about the Classic 150 and I am seriously considering using that as a secondary controller just for the two Unisolar panels in parallel. This (he says hopefully) may mitigate some shadowing issues of the series-connected panels plus the acceptance angles of the Unisolars are said to be better than your average-sized panel.

So, that's it. Depending upon your floor plan you might come close. I have only two 8Ds in parallel for the house and two red-tops for the chassis. But I could simply throw another 8D into that space and just use all of them together for whatever. With solar working it seems unlikely that the start batteries would get too low what with the plethora of monitoring devices I have (Trimetric 2025 plus the Classic 150) and, anyway, I have a handy-dandy lithium power pack that would certainly start the generator if nothing else.

John's (fouroureye) thoughts on AGMs are interesting. I would love AGMs but we are at least 2 years from even snowbirding (and perhaps 4 - the downside of marrying a cute 18-year old when I was 30... I dunno what I was thinking.... oh, wait.... now I remember what I was thinking!) so I think I'll do two new wet-cell 8Ds for now and call it good. Who knows what will happen in two years?

Let us know how your arrangement works out.

BTW: I used 3m VHB tape for bonding the support stands for the solid panels to the roof. Have about 1,000 mostly-freeway miles on the rig and they look fine. I hope they stay fine.

Craig

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #9 – September 06, 2014, 01:15:50 pm

Craig, yes you knew what you were thinking-she can take care of your broken down body in a few years. Thought I was doing the same thing 30 years ago, I aske the questiong on my first date with her.. are you 18? Sheepish smile, yes. Oh I should say, she asked me out. After I was hooked, found out she was 22-too late, I was hooked and 6mths later married.

L O L great times!

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #10 – September 06, 2014, 01:31:10 pm

Quote from: fouroureye – September 06, 2014, 01:15:50 pm

Craig, yes you knew what you were thinking-she can take care of your broken down body in a few years.

John... 40 years by her count (I count from the day she moved in which is 41... women are sure funny about that stuff). Best part is that she can drive the RV (she's a school bus driver). So when I'm 80 I can just snooze in the co-pilot seat 'til she says that we're there.

In 1973 I knocked on a door to see if the owners of the two dirt motorcycles wanted to ride trails with me. A cute redhead answered the door, told me one of those dirt bikes was hers. That same day she knocked on *my* door with a hard hat in her hands and the rest is history. In 2003 she and I stood at the same door I had knocked on while we waited for our daughter to come out so we could walk her down the aisle at her garden wedding.

Ya gotta watch what doors you go knocking on....

Craig

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #11 – September 06, 2014, 02:25:44 pm

Craig, my 225 has the full dinette and the refrigerator is on the driver's side. It also came without an inverter which was a surprise. I guess I need to know more about this particular coach before I decide on batteries, mount the controller and run the wires.
I got along fine with 235 watts of panels, a 20 amp PWM controller, four 6 volt golf cart batteries and a 750 watt inverter in my old coach. Those batteries were 6 years old and still in good shape when I sold it.
John, in my case, I put up as much solar as the roof allows and I put in as many batteries as possible in my old coach. I can go a variety of different ways with this coach so I definitely appreciate your input. I was not happy with the constant care and feeding that the 6 volt lead/acid batteries required or with the corrosive aspect.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #12 – September 06, 2014, 03:01:10 pm

Quote from: Dakota Slim – September 06, 2014, 02:25:44 pm

Craig, my 225 has the full dinette and the refrigerator is on the driver's side. It also came without an inverter which was a surprise. I guess I need to know more about this particular coach before I decide on batteries, mount the controller and run the wires.

I looked at another FT with this layout but I don't recall it very well (over 3 years ago, after all). In '93 inverters were an "option" and that technology was not what you would call "developed". I show an inverter on the drawings but I would be amazed if any U225s or U240s rolled out of Nac with one.

Really, the only way in is via the refrigerator vent unless you're a lot more comfortable with drilling holes in the roof than I am. Just aft of your fridge is the bathroom, right?

Depending upon what your MPPT controller is capable of, your cables from the controller might be a LOT bigger than your cables from the combiner box. I have #10 wires from the combiner because the system only has to handle 8-amps (wired in series). If you have 40-amps you'll be fighting those cables all the way down.

And then, if you have your battery box on the curb-side you'll end up with a much longer run than I had. I didn't choose my coach for solar but it was serendipitous that the one I chose was perfect for the cable runs.

Quote

I got along fine with 235 watts of panels, a 20 amp PWM controller, four 6 volt golf cart batteries and a 750 watt inverter in my old coach. Those batteries were 6 years old and still in good shape when I sold it.

It's good that you are not a complete solar novice. Lots of people get lost in the details. But the latest idea is series wiring for higher voltage (and, as a consequence, much lower current in the panel loop) and not many people are thinking about this. Pierce was the first one and once I clued in on what he was talking about I jumped onto the bandwagon. You might want to rethink your system... or not. 500 watts would be plenty for everything except, maybe, residential refrigeration.

Quote

I was not happy with the constant care and feeding that the 6 volt lead/acid batteries required or with the corrosive aspect.

Automatic watering is, I think, the antidote for that.

Craog

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #13 – September 06, 2014, 07:14:09 pm

Thanks Craig. I, for one, would never expect to run the refrigerator on solar. I never had an inverter powerful enough to run the coffee pot or microwave in my old coach but my old house batteries were always full by noon and in an average day I had plenty of excess solar power to do so. I used to run a swamp cooler that used 12 amps on solar.
I was planning on putting 2 or 3 inverters in this coach, one of which would be 1500 watts so I could power the coffee pot and microwave, but I will check out the latest inverters to see what advancements have been made. I was always under the impression that high watt inverters wasted lots of current.
I just checked and the 2 batteries that came with this coach are NAPA 7271's. They are both 8D starting batteries and my guess is that the house battery's day are numbered. I will most likely get rid of it of it and then fill the existing compartment with deep cycle batteries. Because my panels and batteries are both on the passenger side I will probably go through the roof and straight down through the closet. I can mount the controller in the closet and put the remote meter on the wall.
Keep in mind that I haven't even finished moving into this coach yet. I hope that someone with this floor plan chimes in with some input.
Automatic watering devices would make caring for lead acid batteries less of a chore but this coach is spotless except for some visible corrosion in the battery compartment. Adding more lead acid batteries and working them every day would probably make that situation worse.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #14 – September 06, 2014, 07:30:32 pm

Quote from: Dakota Slim – September 06, 2014, 07:14:09 pm

I was always under the impression that high watt inverters wasted lots of current.

This is still true.

Craig

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #15 – September 06, 2014, 07:49:15 pm

All batteries need to the exact same age and condition. Move the batteries in their mounts occasionally to change the ends to be in the middle. if three batteries equalize the battery cable lengths exactly and draw the power from a common position IMO.

The closer any system is to a equal draw and recharge the longer each battery lasts and the power out of the system improves.

My guru buddy moves the batteries yearly while servicing the cables if not exactly equal.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #16 – September 06, 2014, 08:41:48 pm

Quote from: Caflashbob – September 06, 2014, 07:49:15 pm

All batteries need to the exact same age and condition....

Hi Bob. I presume you mean "all the "house batteries" *should* be the same age and condition.".
If someone has 6 or 8 T105's and one goes bad in 6 or 12 months do all the batteries need to be replaced?

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #17 – September 06, 2014, 08:44:00 pm

You would need to separate all the batteries and check their resting voltages. If the voltages were all close to the same, you could get away with changing out only the bad one. If not, then yes.

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #18 – September 06, 2014, 08:47:13 pm

Quote from: Dakota Slim – September 06, 2014, 08:41:48 pm

Hi Bob. I presume you mean "all the "house batteries" *should* be the same age and condition.".
If someone has 6 or 8 T105's and one goes bad in 6 or 12 months do all the batteries need to be replaced?

Ah the bad(expensive) side of perfection.

A load test on every separated battery in the system might be a guide. Then check the replacement. If normal cabling(not equal lenght) maybe put the new one on either end to get used harder?

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #19 – September 06, 2014, 09:00:00 pm

No, applies to engine batteries in my opinion. With batteries several years old, if one goes bad, put the other one (or two) in a car/truck. This is why I go with Duralasts. At $90 back when we bought our coach, no big deal to replace the other two if one goes bad after 3-4 years. Duralast will have a long warranty so you really only have to pay for two out of three (or 1 out of 2). They are about $120 today so not much of an expense.

With summer almost gone, cold weather starting requires all batteries in excellent health not a brother or two in so-so condition. Fast cranking can mean the difference between a quick start and extended starter use and wear. With house batteries, you may lose a little inverter time as they age but that's about all.

T-105s should last a long time. If one went bad, I would load test the others to make sure this was an isolated case and then just replace the bad one.

Pierce

Re: Solar Panels and the Concept of Separate Chassis/House Batteries

Reply #20 – September 06, 2014, 10:22:58 pm

The use of solar panels and battery bank needs really depends on what one is doing and how many people are using the solar equipment. If you are a full time boondocker like some of us, you will cycle your house batteries daily, 365 days a year. Starting batteries, be they D8's or any other size, were not designed for this purpose and will not last. If one uses more that 50% of a battery's capacity on a regular basis it will not last as long as it could.
If you are in a cold climate, your needs will be different that someone who is in a warm climate but regardless of where you are, how many solar panels you have and how many batteries you have, the shorter daylight hours of winter mean less solar output.
IMHO, the house batteries should definitely be deep cycle and operate separately from the starting battery

Affiliate Notice