dgk02

I want a second charger, Currie wants $190 for one. I think the correct one is 24V 2amp but this one is $60 and 4 amp. It also doesn't specify Li-Ion. This one is 2 amp and $8 but also says nothing about Li-Ion. What charger can I use that is reasonably priced and won't hurt the battery?

Sangesf

You need to find a charger that's set for 24v Lifepo4.

dgk02

Ah, rack-mounted battery. Lithium Ion, 3.7*7 so 25.9 volt. I don't see anything about Lifepo4 though. Is there a difference?

This looks like the right one (even says Ecoride) but it's still $160.

Sangesf

3.7 is nominal (normal during riding).
Fully charged is 4.1v - 4.15v.
28.8v (normal 8 cell lifepo4 is 3.6 per)
28.8v / 7 cell = 4.11v per cell which is just where you want each cell to be at full charge.
(I'm expecting that you have a BMS)
EDIT: Just read up on it.. Battery pack has a BMS on it...
A 24v (28.8v) LiFePo4 charger at 2.5a-5a will work for you.
(You may just have to change out the charger plug.)

jethro56 

Yes LIPO is 3.7V nominal per cell LiFePO4 is 3.2V. There's a bunch more: https://en.wikipedia.org/wiki/Lithium-ion_battery

dgk02

Ok, could you please point out a charger somewhere that would be good? I'm looking at Amazon and Ebay and am not doing well. Would I be able to get the proper connector and get it wired up? The thing looks like an old microphone connector - three large pins.

Sangesf

I just looked up eBay and there is a bunch... Look up 24v lifepo4 charger
Radio shack sells the XLR connectors.

dgk02

Ok, so this thing and I can somehow get the wiring correct when attaching the XLR connector. Seems right?

Sangesf

Yep...
FYI.. If you haven't invested in one yet, buy a multimeter/voltmeter.

dgk02

Just one more thing. This nice Tenergy charger specifically states 9 cells but I have 7. So, no good? The other one didn't say anything about number of cells.

Sangesf

It's set (at the factory) for 9s cells..
The info shows a variable output.. (Maybe you can tell them what output you want?)

For the price / amp rating, a Vpower 24v lifepo4 5amp charger works well.
Ive been using one for over 3 years with no issues.
The main thing to watchout for is the polarity of the wires...
If you mix them up backwards you WILL blow up most chargers.

dgk02

Charger has arrived, not as pictured but 24 volt lifepo4 5amps. It has a computer power type output (flatish 3 prong). I guess I need to use the multimeter/voltmeter to figure out what the exisitng charger does and copy it to the XLR connector? It would be nice if the XLR connector had that type of plug on the input side but it seems to be an audio connector normally so that's unlikely.

Sangesf

Make sure of polarity and voltage output..
And let us know how it goes..

dgk02

Ah, if only I knew how to check polarity and voltage. I guess that's where the multimeter comes in.

Sangesf

You put the red and black from the meter and look at voltage reading..
If it reads positive, then you have the polarity correct..
If it shows you negative voltage, you have polarity backwards, switch red and black probes and check voltage again.. It should be positive.
Then you know which is red and which is black.

dgk02

I couldn't get the XLR connector at any local Radioshack, so I ordered it from monoprice.com - $2.27 plus $1.71 shipping. It will arrive in a few days. So I opened the XLR connector on the existing charger and indeed there are only two wires connected, red and black. I sliced off the end of the Vpower charger and it has two wires, blue and brown. So I just need to find out which is the hot one and connect it to the same pin that the red wire is connected to on the existing charger. That should be easy enough.

Will the charger know when the battery is fully charged? The existing charger specifically says 10ah and 2amp, the Vpower says 5 amp but nothing about 10ah. There is also only a sticker on it that says 24 volt which makes me a bit nervous. I'll see if I can get a Chinese friend to read what it says.

dgk02

I put it all together and it seems ok but I'm not convinced that it just did a full charge on the battery. When I took it to work this morning it took about 2 hours to recharge to full (on the original charger). I got home, put it on the new charger, and it was done in an hour. I guess maybe it charges faster since it's 5 amps instead of 2? Is that ok for the battery?

Sangesf

Yep, exactly what it's supposed to be...
Although the old one says 2a, it's prolly closer to 1.4-1.6v.
The 5a one is closer to 4.5a.
(all of this is under load).

dgk02

As long as the battery is ok with the faster recharge, so am I. Thanks for all your help.

Sangesf

Not a problem. Anytime!