Battery issue

[BCBeaver]

48V 13AH Battery pack. When I hit the throttle hard on the bike the battery dies. The indicator lights at the top of the battery only show very dim and it will not opwer the bike. I remove the battery and reinstall it and it appears to work fine. If I ramp up the throttle it works at full throttle so I suspect it it pulling too much current and the battery BMS is shutting it down? Or maybe it is under volting? The battery shows 53V unloaded

 

[harryS]

This is for a BBS02, probably 750W? Is the battery fairly new, or is it something you've been riding for a while and this just started happening. If it's a new one, you probably got one that's not rated to pull 30A. That's what you need for a BBS02.

For an older battery, this sounds to me like cells that contribute to voltage sag, which shuts off the BMS when you're on hard throttle. With an accurate voltmeter, a 48V battery should be 54.6 volts fully charged

If your electrical engineering skills are up to it, measure all 13 cell groups at the balance connector. See if all of them are balanced.

 

[BCBeaver]

It's 1 yo. Unknown treatment history. Spinning a 750w bafang hub motor. Was "fully" charged (charger light turned green). I'll check it out. Thanks

 

[harryS]

A healthy battery would have all the cells within .1 volts. Sounds rigorous, but that's what they say.

 

[Gionnirocket]

48V 13AH Battery pack. When I hit the throttle hard on the bike the battery dies.

Try using it as designed.

 

[indianajo]

If you have a matching connector, you can test your battery sitting on the steps.
Load down with 10 ohm 450 w rated resistors. That is 5 amps. Will it hold >48 v there? Not? it is trash. (I bought 5 ohm 225 W Dale logs from apexsurplus of sun valley, 5 years ago).
Try again 5 ohm 750 W rating resistors. That is 10 amps. If holds > 48 v you should be able to get home.
Try again 2.5 ohms 1200 W rating. That is 20 amps. Collapse there? that is the max amps you can have. Good there? don't use more amps than that.
My luna battery was sold with 50 A rating (not AH, that was 17.5) and does produce 10 amps reliably at 2 1/2 years of age.

 

[harryS]

Try using it as designed.

It's best to drive defensively so it doesn't come up, but f you've ever been in a situation where a blast of throttle wouldn't hurt, having your battery reset at that point is bad news.

 

[BCBeaver]

Try using it as designed.

Oh, you're just so witty.

 

[tomjasz]

Oh, you're just so witty.

Almost true! An undersized cheap China battery getting hammered with full throttle is a recipe for poor performance.

 

[Gionnirocket]

It's best to drive defensively so it doesn't come up, but f you've ever been in a situation where a blast of throttle wouldn't hurt, having your battery reset at that point is bad news.

I agree, but with the facts given I'm not sure anything is worth doing other than suggested.
Please standby for Controller Issue and Drive Train Issue threads

 

[AHicks]

If you just got this battery, there's a chance it just needs some exercise to allow the cells a chance to balance properly. It may be a victim of the 50-80% charge thinking. The 53v reading at fully charged status reinforces this thought. That's a pretty low reading for a 48v battery that's just come off the charger.

If the cells are not balanced properly (for whatever reason) you WILL get a big voltage sag with a big load. In this case, maybe enough to cause the problem you have.

To balance, put like 5 miles on the battery, then charge fully. Repeat several times, letting the charger charge the battery fully each time. Take your time here. Don't try doing this in a day. See if that doesn't improve your wide open throttle performance.

Of course this is not going to help a really inexpensive battery, or one that's been assembled using un-matched cells. Just a thought..... Best of luck!

 

[Gionnirocket]

If you just got this battery, there's a chance it just needs some exercise to allow the cells a chance to balance properly. It may be a victim of the 50-80% charge thinking. The 53v reading at fully charged status reinforces this thought. That's a pretty low reading for a 48v battery that's just come off the charger.

If the cells are not balanced properly (for whatever reason) you WILL get a big voltage sag with a big load. In this case, maybe enough to cause the problem you have.

To balance, put like 5 miles on the battery, then charge fully. Repeat several times, letting the charger charge the battery fully each time. Take your time here. Don't try doing this in a day. See if that doesn't improve your wide open throttle performance.

Of course this is not going to help a really inexpensive battery, or one that's been assembled using un-matched cells. Just a thought..... Best of luck!

That thought had crossed my mind as well... But I don't believe that to be the case here.
That said isn't it better to do more of a full cycle to try and recondition a battery? Several 40% - 100% cycles?

 

[AHicks]

My opinion, nothing written in stone to back it up, is that you don't need to pull the battery pack down that far prior to charging. It's more about getting the low cells topped off, without overcharging the ones that are already there - extended amount of time during the balance cycle, which happens at the end of the charge cycle.

That said, if you want to pull them down to 40%, go for it! The end result likely the same to my way of thinking.

 

[Gionnirocket]

It's probably more dependant on the charger and BMS than what either of us think

 

[AHicks]

It's probably more dependant on the charger and BMS than what either of us think

Your guess, not mine.
I believe the frequent cycles through the balance cycle part of a charge, hopefully, does an end run on both the charger and BMS that are possibly shutting the charge down prior to the balance charge completing (due to total pack voltage). Giving the balance cycle some extra time to do it's thing is the objective of this exercize. That's why I don't beleive you need to discharge as low as what you are thinking. Right or wrong, my thoughts anyway. FWIW, -Al

 

[Gionnirocket]

The only thing I would add to that is to use the lowest amperage charger available. Long and slow charging can definitely help.

 

[BCBeaver]

I agree, but with the facts given I'm not sure anything is worth doing other than suggested.
Please standby for Controller Issue and Drive Train Issue threads

Aren't you just a ray of sunshine and positivity.

 

[BCBeaver]

Thanks for the input. I think I'll give it back to the owner and point him at this thread.

 

[Gionnirocket]

Aren't you just a ray of sunshine and positivity.

Lucky you... you caught me on a good day.
My meds must be working