Solar Starter System

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Solar Starter System

December 24, 2018, 02:30:24 pm

In order to supplement my new 300ah of LiFePO4 batteries I've added 710 watts of solar, with room to easily add a 3rd panel for 1065 watts. I'm not looking to eliminate my generator, only to stretch the time between charges a little bit. Testing so far, on a sunny winter day with the panels flat, suggests that they will roughly replace what the refrigerator uses during the day. Starting in the morning with 62% SOC, I ended the day with about the same 62%. So I can go 2 full days between generator charging, maybe a little more or less depending on other loads. If I tilted the panels I'd have probably ended the day a little on the positive side.

I bought Mission MSE355SQ6S 355 watt Perc panels from a local Craigslist seller for $225 each. Assembled in San Antonio, they are 18%+ efficient, mono panels capable of a little over 9 amps at 39 volts each.

MSE PERC 72 - Mission Solar

The panels are wired in parallel with 10 AWG solar wire on the roof & 6 AWG marine cable, through cable glands at the fridge vent, to the charge controller in the battery bay. Connectors are all MC4.

AM solar sells nice tiltable brackets but these panels are too thick for them. I debated permanently flat mounting them with unistrut but decided to make my own brackets and it wasn't much extra cost or effort to make them tiltable. They may not get tilted often but I'll have the option. The brackets are 6" long 2x2x1/8 aluminum angle, stuck to the roof with 12sq inches of VHB tape per corner. I'll come back later with Dicor over the brackets. The bolts are 1/4" stainless. The tilt supports are 1x1 square tubing, pre-drilled at 5 degree increments for angles between 25 to 50 degrees, and they bolt to the brackets for storage. Star knobs keep it all tool-free. The front edge of each bracket runs the full width of the panel in order to limit wind under the panel while driving, with about 1/4" clearance at the middle of the roof and slightly more at the edges.

I chose the Victron 100/50 solar charge controller. If I add more panels later this charger may occasionally limit my output to 50 amps but my theory is that this won't happen very often. If I'm losing a few amps at noon on a perfect day then I'm probably more than topped off by the end of the day anyway.

This is not directly related to the solar but I added a sterling 30 amp DC-DC charger between the batteries and the alternator. This will reduce the load of the lithium batteries on the alternator, which was running at about 130 amps. Adding the load of the chassis batteries brings the total too close, for me, to the 160 amp rating of the alternator. Maybe it could handle it but I'd rather not push it that far for hours at a time. The battery boost switch can still be used to combine the battery banks if faster alternator charging is needed.

Everything on the equipment board was purchased from Bay Marine. Alan & Ron were both very helpful. I didn't create a wiring diagram but the board is laid out and labeled so that anyone can follow it. Everything was bench mounted & prewired on the board, then the board mounted in the battery bay with only a couple of wires to connect.

Overall, this was a fairly simple upgrade. It took time but nothing was particularly complicated or difficult. Total cost of all materials & equipment, excluding the batteries, was about $1400. Deduct the optional DC-DC charger and the solar portion is under $1200. That's still a LOT of generator fuel, which I've never minded using, but it will be nice to have the solar.

Re: Solar Starter System

Reply #1 – December 24, 2018, 03:09:21 pm

Nice job. Glad to see a breaker in your circuit, something that gets overlooked often. I thought about tiltable panels but I just don't want to get on the roof to do it. A third panel will make a big difference in time available especially when solar is less than perfect (most of the time).

Re: Solar Starter System

Reply #2 – December 25, 2018, 01:37:41 pm

Nice, neat installation. If running a residential fridge, you can't have too many panels up top. Minimizing the battery discharge percentage insures a longer life.

For newbies, buying a controller that will handle future expansion will save money in the long run. A controller that will handle around 100 amps doesn't cost much more than models with less capacity. Ours has given no problems in almost 10 years. Good to purchase one made in the U.S. for quick turnaround in case of a problem. Less than $600 will deliver a model that will work with solar, wind and hydro. A little extra for a remote panel.

Best MPPT Charge Controller (2018) - Solar Charge Controller Reviews

Pierce

Re: Solar Starter System

Reply #3 – December 25, 2018, 02:34:25 pm

Nice write up. Wondering if you considered another brand of panel, and if you have any way to measure the output of your panels. IF so you could try to position the panels perpendicular to the sun rays and check the output. Some sunny days are better than others, depends on temperature, dust, smoke, and humidity.

Re: Solar Starter System

Reply #4 – December 25, 2018, 02:44:19 pm

Quote from: Pierce & Gaylie Stewart – December 25, 2018, 01:37:41 pm

Nice, neat installation. If running a residential fridge, you can't have too many panels up top. Minimizing the battery discharge percentage insures a longer life.

For newbies, buying a controller that will handle future expansion will save money in the long run. A controller that will handle around 100 amps doesn't cost much more than models with less capacity. Ours has given no problems in almost 10 years. Good to purchase one made in the U.S. for quick turnaround in case of a problem. Less than $600 will deliver a model that will work with solar, wind and hydro. A little extra for a remote panel.

Best MPPT Charge Controller (2018) - Solar Charge Controller Reviews

Pierce

Actually, at least in the Victron controllers, the 100 amp version is quite a bit more $ than the 50 amp...more than double. I can add another 50 amp later if I need it and still come out $100 less, including wiring, than buying the 100 amp now and possibly never needing it. That was part of the planning that Bay Marine helped me understand. They would have been happy to sell the larger unit but agreed that this is also a good way to go. I may add a 3rd panel but I really doubt if I'll need more than the 50 amps unless I go to 4 panels.

The LifePO4 batteries don't suffer from the same discharge issues as wet lead acid batteries, including AGM or Gel. They can be discharged much further and stay there indefinitely without damage so minimizing discharge % isn't really a concern. They also recharge to 100% much quicker without having to go through a float stage. They have their own issues (temp sensitivity, initial cost) but they have lots of benefits.

Re: Solar Starter System

Reply #5 – December 25, 2018, 02:51:30 pm

Victron 150/60 mppt controller on an overcast day.

Re: Solar Starter System

Reply #6 – December 25, 2018, 03:32:21 pm

Quote from: Jerry Whiteaker – December 25, 2018, 02:34:25 pm

Nice write up. Wondering if you considered another brand of panel, and if you have any way to measure the output of your panels. IF so you could try to position the panels perpendicular to the sun rays and check the output. Some sunny days are better than others, depends on temperature, dust, smoke, and humidity.

I didn't spend a lot of time researching different panels. I knew that I wanted to go with a few large panels rather than lots of smaller ones. I tried to select the best large panel that was offered by my local Craigslist solar dealer, which pretty much came down to the Mission that I chose and a Trina panel. The Mission seemed to offer good power/sf and the Perc technology was a benefit as well. After I bought them, Alan at Bay Marine read the specs and said it was a really good panel that isn't common outside of solar farms yet.

Unless it can be tested with a multimeter, I don't have anything to measure output other than the standard readings from the Victron controller. My testing was with the vehicle parked almost perpendicular to the sun, although that's not always going to be possible. I also have not tested with them tilted, which I expect would make a big difference but I won't be tilting them often. I will test that soon though.

Re: Solar Starter System

Reply #7 – December 25, 2018, 03:52:24 pm

I have a magnum pt-100. It will accept 240 volts from the newer residential self contained higher efficiency inverted panels and can output 100 amps to the battery banks..

I have no idea if any solar can put out the 100 amps but if a number of panels can produce that much 12 volt it would seem to match the mk gel batteries suggested 1/5th C charging rate?

The gels are not as affected as much by charging at a lower rate versus non lifeline agm's.

Slow charging agm's and/or not returning them to 100% SOC leads to permanent loss of capacity as far as I know..

My suggestion is when you need to acquire new batteries and do not have the ability to recharge your bank at the same rate as the alternator and inverter/charger put out the use of gel batteries would seem necessary?

Gels are the lowest cost per cycle available and have the ability to not sulphate from not being charged at the 1/5 th C.

The alternative charge rate from most battery makers is 1/20th C.

Which would take forever.

That's why I sourced the pt-100 for its possible charge rate. Have not gone the next step and seen how many panels can be fit to our roof yet and how many amps they can put out.

If my future solar cannot put out the 1/5th C then no problem as the gels live fine charged at lower rates.

If my info is incorrect I hope some one here with more direct knowledge will help here?

Yes I understand the PT-100 is more money but the ability to accept the 72 cell more efficient smaller 240 volt panels was a idea.

Re: Solar Starter System

Reply #8 – December 25, 2018, 04:58:32 pm

Quote from: Caflashbob – December 25, 2018, 03:52:24 pm

I have a magnum pt-100. It will accept 240 volts from the newer residential self contained higher efficiency inverted panels and can output 100 amps to the battery banks..

I have no idea if any solar can put out the 100 amps but if a number of panels can produce that much 12 volt it would seem to match the mk gel batteries suggested 1/5th C charging rate?

The gels are not as affected as much by charging at a lower rate versus non lifeline agm's.

Slow charging agm's and/or not returning them to 100% SOC leads to permanent loss of capacity as far as I know..

My suggestion is when you need to acquire new batteries and do not have the ability to recharge your bank at the same rate as the alternator and inverter/charger put out the use of gel batteries would seem necessary?

Gels are the lowest cost per cycle available and have the ability to not sulphate from not being charged at the 1/5 th C.

The alternative charge rate from most battery makers is 1/20th C.

Which would take forever.

That's why I sourced the pt-100 for its possible charge rate. Have not gone the next step and seen how many panels can be fit to our roof yet and how many amps they can put out.

If my future solar cannot put out the 1/5th C then no problem as the gels live fine charged at lower rates.

If my info is incorrect I hope some one here with more direct knowledge will help here?

Yes I understand the PT-100 is more money but the ability to accept the 72 cell more efficient smaller 240 volt panels was a idea.

Bob, must be missing something. Are you saying take a 72 cell 40 volt dc panel and using the micro inverter on the panel, to change it to 240 volt ac and send it to your inverter/charger which then converts it down to 12 volts to charge the batteries. Is this more efficient than taking that 40 volt dc from your panel and use your solar controller to convert it to the 12 volts to charge your batteries?
I can see this working in a grid tie system where you were selling back power and you wanted to store some electricity in case of an outage, but why on an rv?
By the way lithiums do not ever need to be charged to 100% SOC

Re: Solar Starter System

Reply #9 – December 25, 2018, 05:13:35 pm

Jim I understand that your description is correct? 240 to the controller then to 12 volt.

Love to have a Tesla power wall someday in my house that mysteriously ends up in the coach. They require 240 as far as I know. They use a control box with internet hookup. Have not done all the homework but this is a long term deal anyway. Sent my guru buddy the pt info and the panel info and the power wall info.

Not on the front burner as the cost is very high.

Re: Solar Starter System

Reply #10 – December 26, 2018, 04:04:12 pm

This isn't intended to start a Cost per Cycle debate, which really deserves it's own thread, but the statement that "Gels are the lowest cost per cycle available" is potentially misleading to someone that might be trying to make a decision on new batteries. By all of the research that I've seen, Gel is the lowest cost per cycle among the wet lead acid battery options (FLA, AGM & Gel). It is not the lowest available cost per cycle when you look outside of those options. Lithium Iron (LiFePO4) is commonly estimated at less than 1/2 the cost per cycle of GEL. It does not sulphate under any charge condition, and can be charged at a much faster 1/2 C rate. It's clearly not the choice for everyone or every situation but it should be given fair representation when such statements are made as fact.

Lithium VS Lead-Acid Batteries: Comparing Total Cost of Ownership - Just...
Batteries: Lithium-ion vs AGM - Victron Energy | Victron Energy

Re: Solar Starter System

Reply #11 – December 26, 2018, 07:59:14 pm

No problem I inadvertently left off my normal li-ion disclaimer. Li-ion kept within their temp envelope should last longer.

I still would not run a non UL stickered appliance in our coach.

DW wants to take off maybe into the winter. As we may not be above zero depending on how our whims go we would have to alter our route potentially because of li-ion batteries. No. Removes some of the true four season dry camp no gen design of the coach.

Tesla powerwall is good for -4 degree F. To 122 degree.

The battle borns to end up with 400 amp hours are nearly $4k. Sale $3,200.

37 degrees low limit certified

50% SOC 350 amp hours gels are one half of that price.

Based on pricing IF it lasts twice as long the cost per cycle may be even.

latest model mk's may be much longer lived than the current chart shows according to their engineer I talked to

Not sure if li-ions can be damaged from long term winter storage below zero.

I would pull them myself

Tesla can be mounted flat on our compartment floor and includes a 5k inverter and is eligible for a large rebate from Edison here it would be tempting to remove it from my garage wall and slip it into the coach.

It could easily run both roof airs. I think the gen could be rewired for 240 volt?

Just dreaming but that and a set of sunpower equinox 240 volt inverted solar panels would be neat.

If I had purchased the Northstar li-ions 6 years ago my wallet would still be empty.

Obviously the technology is better. I have Tesla cells in our Prodeco electric bikes. Work great.

The projected lower cost per cycle is dependent on perfect care and feeding.

Hope it works well for everyone.

Re: Solar Starter System

Reply #12 – January 13, 2019, 12:59:41 pm

Rather than waiting until I find out that I want a 3rd panel and that my vendor is out of the matching Mission 355 watt panels, I went ahead and added it now. This uses all of the roof space that I'm willing to provide at this time, while providing a total of 1065 watts. I don't plan to rely on the solar for any long term needs and I want to keep easy access to walk around my roof. If I ever decide that more solar is needed I can easily relocate a couple of panels, or use smaller panels on a new controller. So, for now, this is probably my final configuration.

Re: Solar Starter System

Reply #13 – January 13, 2019, 02:39:14 pm

Three panels for more than 1000 watts is a great size. It leaves you the walk around room you need for maintenance and service on the roof and is enough to charge batteries on most days. Nice job.

Re: Solar Starter System

Reply #14 – January 13, 2019, 07:08:43 pm

I love your write up. Good info, but I have a question. It looks that your panel mounts are glued to the gel coat, what with? I have plans to install panels my self but didn't like the idea of adding holes.
Thanks for your time

Re: Solar Starter System

Reply #15 – January 13, 2019, 07:37:24 pm

I did not want any new holes in the roof either. They're stuck down with 3m VHB tape.

Genuine 3M VHB #5952 Double-Sided Mounting Tape 10.5M / 35FT / 420 Inches...

4x2"x6" brackets per panel, for 12 SqIn of adhesive surface area each. 48 SqIn total. Should hold about 90 lb/SqIn.....more than 4k pounds per panel. Clean the surfaces well and they will not come off. Most installations are done this way.

Re: Solar Starter System

Reply #16 – January 13, 2019, 09:31:06 pm

There is a 3M cleaner/adhesion enhancer you can use.

Amazon.com: 3M 111 Clear Tape Primer - Liquid Bottle - For Use With 3M VHB...

Comes in small single use wipes as well.

You want the mounts to fit tight to the roof. Clean both parts. Press the mounts into place. Add some weight if you can and let it sit overnight before mounting the panels. Make sure the panels do not pull one edge of the mount up when you tighen it up. A 90Â° mount on opposite sides will not be parallel to the sides of the solar panel frame. They need to be about 92Â° to fit well or you should use some shims to make them fit well. I made my mounts 12" long. Can't be too big. Once the tape is set up use 3M 4000UV caulk on all four edges of the mount along the roof.

I attached the mounts to my panels and placed them on the roof and put blue painters tape around the mounts on the roof. Then moved the panels, cleaned the roof and the bottom of the mounts. I put the VHB tape on the roof where the blue tape marks were and rolled it out with a laminate roller. Then I pulled off the plastic cover tape off the VHB tape, moved the panels into place and pressed them into the VHB tape. The next day I removed the panels, caulked, attached the wiring and reattached the panels. Get a helper, be very careful on the roof.

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Re: Solar Starter System

Reply #17 – January 15, 2019, 09:00:20 am

Nice Roger,
Does the dark shower roof keep it cool? I have thoughts of misting some soft red paint over my clear skylight to reduce the
solar gain.

Re: Solar Starter System

Reply #18 – January 15, 2019, 09:26:26 am

Roger,

Just estimating from your pictures, it looks like your 12" long brackets are about 1" wide, for 12" SqIn of tape surface area? By using 2"x6" I got the same 12 SqIn but I rotated them 90deg and placed them on the short side of the panels. 12" would have been too long to make full contact with the roof curvature on that side but 6" worked fine, at least in the middle of the roof where my panels are mounted. Maybe not for panels mounted at the outside edge. You don't need to worry about the 92 deg bends that way. The added benefit is that the pivot points on the short side allow for easy removal or tilting. As always, many ways to achieve good results.

Re: Solar Starter System

Reply #19 – January 15, 2019, 11:09:49 am

The bottom legs on my brackets are 1-3/4" wide. I used 1.5" VHB tape. 18 sq in each, 72 sq in per panel. At 91 psi that is 6500 lbs assuming perfect adhesion, contact and all the other uncontrollable things. The bottom edge of the panels at the edges are about 2" above the roof.

The roof has the same curvature across from side to side no matter where you put the panels. If you attach the brackets to the panel on the sides and set it on the curved roof the 1-3/4" leg will contact the roof at the inside edge and be about 1/32" off the roof at the other edge. To get the best and most uniform contact (and strength) uniform contact is important. The VHB tape has some thickness to it and will accomodate some variations but that seemed too much to me.

Roof Curvature

A 6" long bracket set going across the roof will have about 1/16" off the roof at each end when the center makes contact with the roof. I was going for the best fit I could do. If you can make it better why not. I had to move a panel and the VHB tape is very strong and tough to to remove.

I thought about tilting panels and for some that works. I just didn't want the risk of getting on the roof to tilt them and then putting them back down. I just added an extra panel. 1200 watts meets our needs on most days in the way we use our coach. There are lots of ways to do that and lots of good solutions to meet your situation.

The shower skylight cover is original. Maybe makes is cooler inside. It probably doesn't matter much.

Re: Solar Starter System

Reply #20 – January 15, 2019, 12:35:13 pm

"I had to move a panel and the VHB tape is very strong and tough to to remove."

I also had to move a panel that I didn't get mounted quite as straight as I wanted it to be. It had been stuck for several weeks so I'm sure it was fully bonded at the time. Using this oscillating tool with the cutting blade and a little isopropyl alcohol, it took less than 2 minutes per bracket to cut through the tape, then another minute or so to clean the surfaces and prep for new tape.

Oscillating Tools - Oscillating Multifunction Power Tools

No damage to the fiberglass. It was surprising easy. It can also be done with a putty knife but it's more work.

Re: Solar Starter System

Reply #21 – January 15, 2019, 01:05:14 pm

When I attached my 4 100 watt Renogy panels I used 3M 5200 under each leg, 4 to a panel. I bought these legs: Amazon.com : Renogy 3in 4 Sets of Tail L Foot for Flat Surface Solar Panel...

But I also put a #10 or 12 stainless screw through the center of each. I was going to use VHB tape but figured since I'd have to coat the tape with caulk anyway I'd just as soon use 5200. I also added a glob to seal the screw head.

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Re: Solar Starter System

Reply #22 – January 15, 2019, 04:14:34 pm

I cut through the 3M 4000UV caulk so that I could get a wire saw (like the cut pvc pipe with) under the edge and then back and forth to cut through the 18 square inches of tape and caulk on each corner. It took some time to cut and clean up. My 12" bracket are overkill but it lets me get 2 bolts in each corner into the bottom edge of the panel frame where holes already exisited. They are not going anywhere.

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