diy solar

diy solar

Racking my brain

P

Ped

Solar Enthusiast
Joined
Nov 4, 2019
Messages
754
I need batteries. My old 6v's are toast. Im a full time vanner with 400w and can expand. Really want to get rid of generator.

Going in circles on what batteries to get. Valence is a bit small. Calb 200ah cells for $659. Or just some AGM. Im stuck in cold temps for a few months so thats an issue. Then do I need a BMS, if not do I rely on inverter LVC and controllers high voltage cutoff. Still got to cell balance. Then I hear the passive balancer suck. And all of it on aliexpress which is tough for fulltime Vdwelling and shipping.

Why is no one making a BMS with low temp cutoff?

Are diy lifepo4 too in their infancy for my pea brain? Should i just wait and make due with a 140ah valence? My loads should only be about 65-95A depending on season.
 
I have Calb batteries in Idaho they do not have low voltage charge protection and I have not as yet had a problem.that That being said I do not use a heavy load in winter and charging is minimal. Before I joined this forum I did not know it was an issue. So I'm not saying it's not an issue but I'm not so sure it's as big an issue as everybody makes it out to be.

I'm switching to LTO batteries anyhow since they charge fast and can go down to -50C charging and store at -20C
 
You can make a crude but effective heating for your LFP batteries to protect them in low temps: Put your new LFP batts in a cooler on top of a 12V heating pad (like a automotive dog bed heating pad).

Tape a temperature sensitive "snap disk" like this that activates at 35F and wire it in-line on the positive side between the battery 12v post and the heating pad. Do this in parallel with each battery in your pack, this will ensure that any one snap disk failing open will not allow your batts to get too cold. Use a bit of thermal transfer grease between the battery and your snap disks. If you want to get fancy you could even put a 12V pizeo buzzer in the circuit to let you know when the heating pad activates.

To guard against a snap disk failing closed I'd put a 12V adjustable temperature alarm to alarm if the batteries get too hot. It's unlikely though because snap disks are dead-simple devices and ultra reliable.

Batts get warm under use anyway and inside a decent cooler I'll think you'll find the heating pad very rarely activates.
 
Last edited:
Ped said:
What you think of this?

Amazon.com : Aiicioo Digital Thermostat Reptile Heating Pad - Hermit Crab Heater with Temperature Control 8 Watt Heat Source for Reptiles Terrarium : Pet Supplies

Amazon.com : Aiicioo Digital Thermostat Reptile Heating Pad - Hermit Crab Heater with Temperature Control 8 Watt Heat Source for Reptiles Terrarium : Pet Supplies
www.amazon.com
Click to expand...
That one is a straight 120V AC pad, it wouldnt work but this one: https://www.amazon.com/OFPUPPY-Pet-...rds=12v+pet+heating+pad&qid=1574138188&sr=8-5 would. Its a 12V pad that comes with a AC to DC adapter so you can use it indoors or in a vehicle. Just do a Amazon search for "12V pet heating pad" and you'll see dozens of examples.

And thinking about it, just two snap disks would be fine to provide redundancy. There's no way two disks would fail at the same time in our lifetimes.
 
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