diy solar

diy solar

Sailboat addict here-new energy storage for my boat

roly1

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Joined
Mar 7, 2022
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Auckland , NZ
I have just received my first shipment of LiFePO4 cells to update my bank.
They seem to spec with a 0.002 max difference in voltage.
They are CALB 230Ahr contained in an aluminium case covered in thin plastic
insulator with rather large aluminium terminals lasered to a flat round terminal stud from battery.

I am concerned that insulation between the square terminal (-ve) and the aluminum case is <1mm thick plastic and could imagine it could easily be a point of failure.
The AL case seems to have positive polarity relative the negative terminal and voltage same as battery. Is this normal; seems like this is not right to me?
I'm tempted to run a 50ohm resistor from case to negative and measure the current.
Even if it is not capable of moving significant current, the prospect of leakage doesn't thrill me.

Edit: On a search I found this is is normal MO for LiFePO4. Not what I would have expected!
I will be doing a rather elaborate insulating FG pouch for each cell and maybe a supa sealant under the
edge of each cell neg terminal. (Or try an swap out for plastic cases with the vendor)
Plus an enclosure to keep out sea elements.
 

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Yes, the connection between the aluminum shell and the positive terminal is expected. When you build up your battery, you should add extra mechanical protection between the different groups of cells in the battery so they don’t short out due to rubbing over time. I’m using heavy duty plastic binder covers. Other people use bare FR4 fiberglass sheets.

In my case, the 8 cells (2p4s configuration) will be in a fixture (light compression) with the plastic sheet between each pair of cells. The whole fixture, in turn will be strapped down in a fiberglass and painted covered plywood box, and a clear, screwed down lexan cover.

It should be adequately protected in that situation. Especially important as the whole thing is in a space under the berth i sleep in!

So yeah, you do have to design and build things carefully when dealing with these cells, but it’s entirely possible to have a safe installation on a boat.
 
I have just received my first shipment of LiFePO4 cells to update my bank.
They seem to spec with a 0.002 max difference in voltage.
Do not let a 0.002 difference in voltage lead you to believe you don't need to top balance. Lots of newcomers make that mistake, and later wonder why the battery doesn't work as well as they expected.

They batteries could ship at 0.002 difference in voltage, but still be very far out of balance. The only way to know for sure they are balanced, is to balance them yourself.

Congratulations on beginning your journey! Upgrading to LFP has been the single biggest game changer upgrade to my full time live-aboard lifestyle.
 
I have just received my first shipment of LiFePO4 cells to update my bank.
They seem to spec with a 0.002 max difference in voltage.
They are CALB 230Ahr contained in an aluminium case covered in thin plastic
insulator with rather large aluminium terminals lasered to a flat round terminal stud from battery.

I am concerned that insulation between the square terminal (-ve) and the aluminum case is <1mm thick plastic and could imagine it could easily be a point of failure.
The AL case seems to have positive polarity relative the negative terminal and voltage same as battery. Is this normal; seems like this is not right to me?
I'm tempted to run a 50ohm resistor from case to negative and measure the current.
Even if it is not capable of moving significant current, the prospect of leakage doesn't thrill me.

Edit: On a search I found this is is normal MO for LiFePO4. Not what I would have expected!
I will be doing a rather elaborate insulating FG pouch for each cell and maybe a supa sealant under the
edge of each cell neg terminal. (Or try an swap out for plastic cases with the vendor)
Plus an enclosure to keep out sea elements.
This is why I bought the older plastic Calb 180 ah cells. Just seemed tougher and a little easier to deal with on my sailboat!
 
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