01-30-2023, 07:45 AM | #21 |
Gone Wild
Join Date: Sep 2022
Location: Minnesota
Posts: 1,289
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Looks like some good progress!
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01-30-2023, 07:49 AM | #22 | |
Gone Wild
Join Date: Apr 2008
Posts: 2,226
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Quote:
That device is an active balancer. when the cells are either at a high or low state of charge I turn that on if the pack is out of balance and it will take up to 5amps from the high voltage cells and transfer to the lower voltage cells if needed. It can also get a pack that drops below my 3v per cell if one or 2 drop threshold working again to get me back to the campsite. |
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01-30-2023, 08:50 AM | #23 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Nice job! Where did you get the active balancer? How do you control when it can balance?
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01-30-2023, 08:54 AM | #24 |
Gone Wild
Join Date: Apr 2008
Posts: 2,226
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Amazon and eBay has them but I bought this one on aliexpress.They all have a little soddered jumper that's closed. I opened it up and soldered a couple wires to control it Through a switch. I thought about hooking it up to a voltage switch so it would come on automatically but it was more work than it was worth. Hopefully, I don't need it all too often
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01-30-2023, 09:15 AM | #25 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
The balancer that I built into my Leaf pack is manually controlled from my display. (with a minimum voltage to operate because I top balance) I find that I don't have to balance very often. I look at cell voltage after charging every so often and if it needs it, I turn on my balancer. It turns off when all cells are within 10mV.
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01-30-2023, 09:23 AM | #26 | |
Gone Wild
Join Date: Apr 2008
Posts: 2,226
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Quote:
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01-30-2023, 09:50 AM | #27 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
For me, passive is fine. It does waste energy but so little that I would never notice it. I built my own - it has an LED for each cell and it discharges high cells at about 1 amp which is enough to do the job if the cells start out reasonably balanced. (which they were)
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01-30-2023, 09:53 AM | #28 | |
Gone Wild
Join Date: Apr 2008
Posts: 2,226
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
Quote:
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01-30-2023, 09:56 AM | #29 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,125
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
My only concern with any balancer circuit is that if it fails, it can kill a cell since the BMS can't protect against it discharging.
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01-30-2023, 09:59 AM | #30 |
Gone Wild
Join Date: Apr 2008
Posts: 2,226
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Re: Budget 90ah 48v lifepo4 battery build (under a grand)
So the positive terminal is switched on this balancer so when it's off the circuit It is incomplete but it is something to be mindful of Because the right type of short could still cause what you're describing being the negative is also the positive of the next cell
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