I use about a 7.5v spoof on 25s lifepo4.
Discrete balance boards for those that will protect your investment.
$5 each cell
Do you have a link. All the ones I found, shipping was a killer. Total cost near $3k
your not running a balancer? what are you charging with ?
No balancers yet, wondering weather to get BMS or balance boards. Using the standard DeltaQ charger. Batteries charge up to between 3.5V and 3.7V, but after a minute of driving they are all at 3.3V. Also need a SOC meter, any recommendations? I built a simple voltage divider to get the voltage down about 78V at pin one to get rid of the “error 16”, but now I get an error 45 and error 15. I set pin one back to factory and bypassed one cell. Drove 22 miles today and still felt like full charge when I got home. I’m new to this so any info is appreciated!
What exactly is a “spoof”? My simple voltage divider worked in theory but not on the Gem. I could get it to register about 75-78V but when connected to pin one the voltage would jump all over the place.
I PM a seller on eBay who was selling a similar battery and asked if he could get a bigger Ah battery. He put together a deal that was posted directly to me on eBay. His English is very broken but the batteries got here. Many of them had test data written on them with over 140Ah.
Spoof is a device that drops voltage a specific amount, no matter the voltage or load.
A bms doesn’t do much for you unless it displays cell voltages. I like the shunt balance boards best.
How did you balance cells to start? Bottom or top balance? If you ran with one cell disconnected you will need to start over.
Lifepo4 are near the same voltage full to empty. So there is no way to know soc from voltage alone.
So I need a spoof. Do you make them or sell them? Or have directions to make them? I initially top balanced but I’ve disconnected two different cells for different reasons so need to redo. I think bottom balancing would be better anyway and then use balance boards to avoid overcharging? Balancing is no fun. I’ve got a 800w resistor load I can discharge with to a set voltage. I was thinking 3v ? Thanks
I use a 7.5v 5w zener in p1.
Bottom balance when using bms or no bms. Imo
My balance boards have two led indicators.
Power led comes on 2.5v to show cell is not over discharged.
Balance led comes on about 3.6v and loads cell until below 3.5v.
Makes balancing easy. Slow, if way off, but easy. Stop charging when a few leds come on. Wait repeat.
A single cell charger or loading high cells with 12v bi-pin lamps, speed things up.
These are elite power acquisition boards that I use stand alone.
If interested, I have a few cpu boards with can and video out. Gave out a few samples, but nobody has taken the time to connect them.
"If you have cells going above 3.5v you need to have a balancer/shunt on them . They will get more and more out of balance on every cycle . In a short period of time some cells will go over 4.0v . Looks like you have a nice setup . protect it .
Do those balance boards need any interface with anything or are they stand alone? It looks like a small ribbon cable coming off. Here is my homemade discharge rig. Ugly but works!
They work stand alone. I cut all the ribbon cables off.
I have 40 of the that clip on. That way I can test 40 at a time. As they were all empty to start, I can mark the capacity of each cell as the balance led comes on.
Then bypass that cell and continue. Mine are new old stock with 80-90% over spec.
70ah get sold here and ebay.
Any over 40ah are useful the rest are scrapped.
What is your c to c distance? I can send you some to balance your pack. Send them back when your done.
I can also send a zener if you want.
This is my balance tool . Have a handful of these . Most balances and shunts cant hold back a DQ charger on a cell level . I clip these on if a cell starts getting to high . IF the balancer and this cant stop it . Unplug charger , wait 30 min and plug back in . Works great .
So one the pack is balanced, is it balanced forever? (As long as you don’t mess with it). I’ve been knocking down the higher voltages with my resistor bank but it’s a pita. It’s 105 mm between terminals. Those balance boards look tempting!
NO Lifepo4 cells will continue to go out of balance if you are fully charging them (above 3.4v) .
Send them back if you don’t like them.
Thanks for all y’alls help. I’m bringing all the batteries down to 2.6v to bottom balance. If I put balance boards on them that balances them at ~3.6v, wouldn’t that be top balancing? Also, I got 22 miles out of these in hilly terrain on my first charge. Then I discharged them down to 3 volts and while checking capacity. Even after 22 miles I still pulled about 45 Ah out of the batteries.