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dontreignoorme
Member
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# Posted: 21 Nov 2018 13:08
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Hi all, and thanks in advance for any suggestions,
I'm building an outdoor solar/battery box. It'll be 4 @ 100 watt panels charging 2 deep cycle batteries.
It will be cold and outside unheated, in Mass. I gather cold is the enemy of battery efficiency. It will only be used for two months in the winter, from Thanksgiving to the feast of the Epiphany.
So, the questions are four:
1 - How should I insulate the box? I've seen bubble wrap mentioned, and regular household insulation. I also wondered about using sand. Thoughts? Suggestions?
2 - How much air space I need to leave above the batteries? I read you need some space, but couldn't find out min requirements.
3 - Would be useful/OK to placed the inverter _below_ the batteries? It seems they give off heat which is an issue in the summer but I'm wondering if I can harness that for my benefit in the winter.
4 - I've seen mention of needing to vent the battery box, but I can't find guidance on how much venting is needed and I'm kinda wondering if I really need to drill holes in the box which will let heat out/cold in. It won't be absolutely airtight, so I'm kinda wondering if it's really needed since most of the guidance I've read is mainly talking about safety for inside-the-home setups.
Thanks for any thoughts,
 b
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beachman
Member
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# Posted: 21 Nov 2018 13:49
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We have an outside battery box and normally take the batteries home for the winter (Canada). I know it gets about as cold in Mass as I spent many years there. The panels should charge the batteries fine and as long as they are charged (LA I assume - LIPO must be heated to charge properly), they should be OK and I do not think you need to insulate the box (others may have opinions), especially only for limited use. I would suggest putting the inverter inside as usual as no battery heat should be needed. The venting of the batteries is to ensure no harmful vapors enter the dwelling. So, if you have provided venting to protect the dwelling, then you should be good to go.
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ICC
Member
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# Posted: 21 Nov 2018 14:25
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You don't specify but are the batteries flooded lead-acid or asealed, like AGM, lead-acid or something else?
If a flooded lead acid type (ones you add water to periodically) then I would not place the inverter under, over ar anywhere near the batteries. Flooded batteries bubble and with most factory caps they also will release a fine mist. That is acidic and you don't want electronics to share that air. Flooded also should be washed, rinsed every so often and if the inverter was under the batteries that makes for a lot more work disconnecting and moving, etc.
For the little cold weather use insulation is more work than it is worth, IMO. Lead acid do not perform as well when cold, it is true. For limited use I would just be careful to not ever discharge more than 50% because there is great danger of freezing a partially depleted battery.
If they are flooded lead-acid they need to be vented for safety. That makes it harder to have good insulation, IMO.
LiFePO4 are the better choice than lead acid. They can be placed inside the cabin. When the cabin warms up the LFP can be charged safely.
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rockies
Member
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# Posted: 21 Nov 2018 21:18
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You might consider replacing your battery caps with these to reduce the number of times you have to top up the batteries.
https://www.flowsystemsusa.com/water-miser-vent-cap.html
Or you could get a kit that makes watering regular batteries easier.
https://www.amazon.ca/Flow-Rite-RV2000-Pro-Fill-Battery-Kit/dp/B001FCAXT0
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spoofer
Member
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# Posted: 21 Nov 2018 21:54
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This is what I have used for years in the Brutal winters of the Tug Hill in northern NY... An old plastic cooler that 2 golf cart batts fit in.. It's insulated already so I drilled holes in the side for venting. I use it inside the cabin with the voltage inverter screwed to the top of the cooler. Works great using a 100 watt panel on weekends etc.
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creeky
Member
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# Posted: 22 Nov 2018 10:57 - Edited by: creeky
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I'm off grid full time so my battery box has the inverter inside the box. I use 6" of rockwool and 2 to 4" of polyiso. I have an insulated floor with 4" of xps.
Yup. Overkill.
I have lithium batteries: no offgassing.
I use battery warmers on a remote switch. I could put it on a temp controlled switch. Just haven't bothered.
I do have a good solar system with 2kw of solar and 9kw of lithium storage.
Do not put anything in the box with vented lead acid.
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