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RV 60P4S battery pack for memorial Day Weekend1
#1
Hi All,

While I am eventually going to have a 80p7s+solar for my sprinter van, right now I have enough kit for a long weekend battery at 60p4s.  I'd like comments on my temporary design!

Goals:
- Run a CPAP (0.19KWH per evening(~8hrs))
- Evening lights 14watts for ~6hrs
-3.7 inth eimage is just the nominal voltage. They are charged at 4.15 or so.

I have the parts and pieces in my kit already and the weekend is approaching!
Thanks for your comments and suggestions.

Paul
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#2
Nice layout. Sucks that the inverter can't handle up 16V. That'd get rid of the buck converter for that portion.
I'm assuming you are using multiple buck converters (possibly even several for inverter or one large one that can handle 15A or more)

What's the purpose of the relays? I see you are trying to capture some of the inefficiency of the buck converter once the voltages get low enough. With that, I'd say just use 1 relay at that point. No sense in making it more complicated than it needs to be.
The BMS should cut the power once the voltage drops too low. So no need for a second relay to do that.
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Proceed with caution. Knowledge is Power! Literally! Cool 
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#3
Thanks Korishan. I appreciate the feedback.

I double checked the inverter rating and lo! it does go up to 16v max ! So I can lower my max charge to 4v/cell and then pull the buck right out - Good call :-)

I'm not sure if the cheap BMS only balances or if it will actually cutoff, so I'll leave in a single relay for th elow voltage cutoff just the same.

Thanks!
Paul
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#4
Most of the BMS boards will cutoff. Usually the balancing portion is the added costs. If it has 2 good sized FETs on it, then it's over/under-voltage protection.

Nice that ya found out that it's 16V. That's gonna save a lot of headache down the road Wink
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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