Lifepo4 voltage?

[Bohh]

Hiya,

How many volts does a fully charged 36v lifepo4 put out? I just tested my setup and the battery was reading 40.2volts but it seemed really weak. (I didn't get on it.) the battery hasn't been charged yet. But I'm wondering what fully charged voltage is?

Thanks!

 

[Johnbear]

The charger charges the battery to 43.8v right of the charger= 3.65v times 12cells. Usually after a short run the battery will level off to 40ish volts.

 

[Bohh]

Thank you for the response! Hopefully that 3 volts will make a difference!

It's charging now, are all these charges pretty much the same? It goes red when I plug it in, and after a big goes green then red. and now it's solid green but the battery reds 42.6v.

Will the charger stop charging when the battery is fully charged or do I need to stay on top of it?

 

[Link]

You can leave it plugged in. The red/green cycling thing is the BMS balancing the cells. It probably won't do that after a few cycles.

 

[dogman dan]

FWI the charger is shutting off, then the bms will let some watts out of the highest charged cells which makes the charger start up again, charging the weak ones some more. This may make the bms get warm when the charge light is green, so if you notice this, its normal. My battery , when new, took a few cycles to develop it's full range. Who's battery? We want all details on sellers and their product and service.

 

[Bohh]

Thank you for the replies. Is it normal for it while on the charger, and testing through the other lead to read at and above 45v?

The battery is from CammyCC. I'm impressed so far!

 

[dogman dan]

Yeah, it will tend to read whatever the charger is putting out. somewhere around 44-46 volts.

 

[Bohh]

Do these chargers alert you when they are done somehow?

 

[Link]

The chargers are usually just SLA chargers modified to have a higher output voltage (LiFe and SLA has the same charging profile), so the only indicator they give is the red/green light. The BMS doesn't have any way of notifying you that it's done balancing.

Shouldn't really matter, anyway. The BMS cuts out on a per-cell basis, so the it won't over-discharge any imbalanced cells. After a while, they should be and stay balanced enough to where the charger won't even cycle like it does now.

 

[Bohh]

How would I know when It's fully charged then? I've had ito n the charger today for 6 hours and it still sporadically goes red for a few seconds.

 

[Link]

It's charged, but not balanced. You can use it, you just won't see quite the full capacity out of it.

FWIW, I left mine in for about two days and it was still doing that before it balanced out.

 

[Bohh]

Thanks for the response. I just went for a 5 minute test ride. Before riding the voltage read 45.1 on the battery. After that short ride it reads 39.8. Should it be that low that quick? The battery is 12 AH.

Thanks!

 

[Johnbear]

That's pretty much how mine are, there is a "surface charge" that bleeds off very quickly after load. The voltage stabilizes after that. What range are you getting?

 

[dogman dan]

Gee I hope it's not 5 minuites range I doubt he knows yet. I just charged my new lifepo4 overnight, and after a week, it stopped doing the balancing. Still tend to leave it plugged overnight, I'm usually in bed before it finishes.