Full time camper system: shade tolerance and designing for bad weather

[all]

Hi! I'm setting up a power system for my camper so I can full time in it. My energy budget comes out to 500Wh per day, of which about half is needed off-peak/at night. I have a 80Ah 12V lead acid deep cycle on there now, so using the 50% discharge rule that's about 500Wh of usable storage. I'd prefer more but don't have room for anything more than a group 24 or 27 battery. I'm thinking I should oversize the panels so that they can still perform ok on overcast days or when camped in the forest, but have not been able to find much concrete information as far as what kind of factor is necessary for these situations.

1) Is there any way to improve battery capacity within a group 24/27 form factor by upgrading to lithium? To some extent I can shift usage by getting extra batteries for my devices and charge those when it's sunny, but it would be even better to have a 2 day energy supply built in to the camper to smooth out the curve.

2) Looking at panels, ebay has 32-cell flexible mono panels for about $95 and 36-cell panels for about $115. I was also considering unisolar panels because they are supposedly shade tolerant but I don't have the space for such a long panel (my area constraint is a 61"x85" surface plus a 52"x85" surface). Let's frame the problem this way: I want 500Wh on an overcast day or in a forest with mixed sun/shade. Which panel/converter combo would you choose to satisfy that requirement while minimizing cost?

There's a $475 kit on ebay with 400W in 36-cell panels, a barebones 30A controller, and an MC4 cable and 4-way splitter. Might this be up to the task, or are these panels not shade tolerant enough?

I'm an electrical engineer so I'm not afraid of tinkering if that gets me the best solution. I see some people have cut and rewired the unisolar panels so that is an option if that's the best way forward.

[Mike90250]

Please, stick with conventional Lead Acid, for your first learning system. Learn how to adjust the programming on the charge controller and inverter, so you can practice on a cheap lead acid battery that is resistant to exploding and burning your rig down.

Just got a new HP laptop today, the graphic on 1/4 of the box, was of a stack of Li batteries on fire.

Stay clear of kits, there is no all-purpose kit. It might work for 10% of the folks that buy it, the rest are in for a rude surprise when they discover it won't run the spa tub and the air conditioner.

[LETitROLL]

Hi! I'm setting up a power system for my camper so I can full time in it. My energy budget comes out to 500Wh per day, of which about half is needed off-peak/at night. I have a 80Ah 12V lead acid deep cycle on there now, so using the 50% discharge rule that's about 500Wh of usable storage. I'd prefer more but don't have room for anything more than a group 24 or 27 battery. I'm thinking I should oversize the panels so that they can still perform ok on overcast days or when camped in the forest, but have not been able to find much concrete information as far as what kind of factor is necessary for these situations.

1) Is there any way to improve battery capacity within a group 24/27 form factor by upgrading to lithium? To some extent I can shift usage by getting extra batteries for my devices and charge those when it's sunny, but it would be even better to have a 2 day energy supply built in to the camper to smooth out the curve.

2) Looking at panels, ebay has 32-cell flexible mono panels for about $95 and 36-cell panels for about $115. I was also considering unisolar panels because they are supposedly shade tolerant but I don't have the space for such a long panel (my area constraint is a 61"x85" surface plus a 52"x85" surface). Let's frame the problem this way: I want 500Wh on an overcast day or in a forest with mixed sun/shade. Which panel/converter combo would you choose to satisfy that requirement while minimizing cost?

There's a $475 kit on ebay with 400W in 36-cell panels, a barebones 30A controller, and an MC4 cable and 4-way splitter. Might this be up to the task, or are these panels not shade tolerant enough?

I'm an electrical engineer so I'm not afraid of tinkering if that gets me the best solution. I see some people have cut and rewired the unisolar panels so that is an option if that's the best way forward.

Good solar panels produce about 10-15% max. on a full cloudy day, so it is hard to go all the way, but oversizing some within reason will help quite a bit on bad days. Trojan makes a couple of very good group 27 batts. should gain you some extra energy over most anything else you would buy and they are not too expensive. You will need a good MPPT controller,they do quite a bit better in less than perfect conditions, and most have adjustable current output limit so that when full sun comes out you dont overcook your batt.

[Mike90250]

When you replace your battery bank, consider 2, 6V 200ah Golf Cart batteries in series, to yield 12V 200ah
Batteries in parallel, are generally best avoided

[zamboni]

I second not using LFP for a starter system both for what Mike said and because at your scale, the benefits aren't so large that they are worth the expense/risk/extra equipment. Also, you may simply find you can't do what you want with solar at all, and then you'll be pissed at the money and time you put into LFP. Flexible panels are cute but won't perform.

I've never gotten any kind of power out of my array "in the forest". Due to MPPT I see a couple hundred Watts on overcast days, but that still requires being parked in the open. Every time i've parked in trees it's no bueno on sun-juice. Perhaps my definition of "forest" is denser than yours...but i'm having a hard time imagining any panel - even "shade tolerant" ones - performing while parked under trees.

You have the roof space for two 24V panels like mine at about 300W each, with perhaps a little overhang at the sides. In series that gives you 48V nominal array w/ 12V batteries. Based on my numbers, you could expect 50-100W in overcast conditions with a clear sky. That can probably get you to 500Wh after a full day. But i'm still talking about clear sky, not forest.

Ground deploy panels seem to be more popular with smaller rigs and especially when parking in shade, since roofspace is too limiting. They ride on the bed while driving and can be moved to chase the sunny patch through the trees. Remember that cables are never as long as you wish they were, just like extension cords. If you're chasing sun bunnies thru the forest probably at least 50' leads will be needed - do the Vdrop math on that.

- Jerud
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1220W array / 1000Ah LFP house bank
MidniteSolar Classic, Magnum MS2812
ME-RC, Trimetric, and JLD404
2001 Fleetwood Prowler 5th wheel 25 foot, self-rebuilt
Full-time 100% electric boondocking (no propane, no genny) since 2015

https://www.livesmallridefree.com