Voltage on a fully charged 48V 20AH ping battery, what should it be?

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DT98
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Voltage on a fully charged 48V 20AH ping battery, what should it be?

I have a ping 48V 20AH battery I purchased over a year ago and have never used it yet...yaaa dumb I know.
But I did put it on the charger every several months.
The first time all the little LEDs lit.
This last time all of them lit up except for three of them.
I measured 57.3v after the charger kicked off.

What voltage should I measure on a fully charged battery?
Do you think I have some bad cells...could they possibly recover after discharge/charge cycles?
Thanks, DT98

Dennis
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Re: Voltage on a fully charged 48V 20AH ping battery, what ...

your battery has either 2 in parallel and 16 in series, made with a total of 32 10Ah pouches or 16 in series made of a total of 16 20Ah pouches. at peak charge 57.3V should be fine, each cell should be close to 3.58V per cell. you can test it with a multimeter. as long as you do not exceed 3.9V per cell, yes that means in a perfect world with perfectly matched cells, your LiFePO4 pack could have a peak voltage of 62.4V, hey but nothings perfect and based on your BMS LEDs, some of your cells have a higher capacity then others. the ones with lit up LEDs should be the lower capacity cells if ur wondering. with the LiFePO4 chemistry, ur batteries will last in excess of 1000/2000 full charge/discharge cycles before they loose about 20 percent of their capacity, as long as u don't abuse them too much by draining them continuously at their peak discharge rating.

here are a few recommended links to read: if u have not already done so, it's from Ping's website http://www.pingbattery.com/usrguide/Wiring%20Guide%20V2.5.pdf
& more importantly this http://batteryuniversity.com/learn/

colin9876
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Re: Voltage on a fully charged 48V 20AH ping battery, what ...

57.3v is good.

I dont agree with that statement 'In a perfect world all cells could be 3.9v, giving you 63v etc etc',
in fact 57v is just right.

The fact some LEDs didnt light just means some cells didnt need any topping up. Lifepos dont self discharge much, and anyway unlike SLAs they dont need to be stored full, so what you say all sounds fine.

DT98
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Re: Voltage on a fully charged 48V 20AH ping battery, what ...

Thank you both for the information!
I am going to connect two 48V 20AH pings in parallel. I ordered the diodes to wire in the circuit. As soon as I have figured out a way to mount the batteries to the bike (looking for saddlebag type system) I will be ready to roll.
Regards...

colin9876
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Re: Why?

Why are you thinking about using Diodes - where??

You certainly dont want or need any diodes between connecting two packs in Parallel

DT98
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Re: Why?

Mr. Ping said they are needed (or should be used) when running large paralled batteries. There is a wiring diagram on the website.
I assume it keeps the two batteries from trying to balance between themselves when or if one is at a different charge than the other for whatever reason...heck, I already have the diodes. I think they were four or five bucks a piece.

colin9876
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Re: Why?

ok, I just find that intuitively illogical.

After having thought about it I can see that if they were charged seperately they could have different voltages, but in an ideal world all the cells would be paralleled in pairs then there would never be an inbalance.

I guess parallel charging wouldnt be possible? Thats a shame if thats the case because it negates the biggest advantage of paralleling the packs.
Personally I would just stick to one pack if that was the case!

DT98
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Re: Why?

Yep...I think that is the down side...that I will probably have to unplug the batteries from the parallel config to connect each battery to their respective chargers.
I'm going to ride the bike to work and it is ten miles one way and I figure the batteries will not discharge so hard and fast if I use a parallel config. I read that sustained heavy discharge is one of the things you want to keep from doing to a LiFePO battery if possible...(my bike with me on it will be around 400 lbs...I'm a heavy guy) :-)

colin9876
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Re: Why?

That discharge rate issue (Peukert's law) is not so relevant to Lifepo4 as it was to lead acid.
How many watts is your bike?
even if you pull 20amps constant thats 1kw (at 50v) and thats only a 1c discharge rate!
Pings can easily cope with 3c discharge.

Id have one battery charging up at work, and one at home, then hot swap them - if you really want to have two packs!

Youll have even more weight as if youre always carrying 2packs, (that extra weight will more than negate the advantage you think you will get using the two cells in parallel rather than using one there and one home!

DT98
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Re: Why?

The motor is a Crystalyte 5305...I think that is the right number.
Those are some good ideas. I will probably try both configurations until I am positive I can make it to work and back with no problem. When I tried using 48V 12AH SLA batteries, they ran out a little short of making it to work. So one 48V 20AH LifePO4 may do the trick by itself. With all that extra juice, I probably will be tempted to not pedal as much LOL!!! :-)

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