Giant Suede Battery Charging Problem

[amberwolf]

If the packs haven't been used in a while, a few charge discharge cycles may be needed to bring them back to normal.

[rickhoover]

Well the new pack charged in about 40 minutes, opposed to the nearly 3 hrs of the old pack. We'll see how she does on a ride.

[dnmun]

i doubt if the pack is balanced, so be careful riding it to exhaustion since you may end up reversing a buncha cells. too bad you can't measure them beforehand.

[docnjoj]

For that new NiMh pack you really need to charge it at a low rate, say C/10 or about one amp or less for a day or two. Half an amp is even better.If the cells are any good they do self balance and then you can charge it with the regular charger. Otherwise, as state by others they will probably be reversed at the end of the miles you travel and damaged.
otherDoc

[rickhoover]

The only charger I have is the Giant's 2 Amp, and I certainly don't want to damage the new pack. Any advice? Don't ride it 'til full discharge?

[dnmun]

you don't seem to understand what we were talking about. imagine that you charge the pack up, adding about 4Ah until the charger detects endpoint. so imagine you have 29 cells that are full and measure 1.4V each because they are full and one cell is at 1.1V and is only holding about 4Ah of charge that you just stored in it.

then you run the battery down to LVC on the controller using about 6Ah of charge.

30.5V is the total voltage. 29 of the cells are measuring 1.05V and have about 4Ah of capacity left 1.05x29=30.4V.

the cell that had the 4Ah stored now has been reversed while large amounts of current flowed through it. after that, it will not take charge, and you no longer have a functional battery. that may be what has already happened to the first pack you said was dead, just no way to know without ever measuring.

[rickhoover]

About a week ago 2 of the cells on the pack I made measured almost nil after I accidentally shorted them (they sparked). I thought they were ruined but later the pack measured about 37V and the cells each measured around 1.2V.

[rickhoover]

I haven't ridden on the new pack yet; just put the 40minute 2Amp charge on it. I charged up the old pack and it took less than an hour this time. i will only ride on the old pack until I know that I won't be hurting the new one.

[dnmun]

ok, with nicad the voltage is related to charge stored so if they are all at the same voltage, then they are as close to balanced as you can get them. but some assume that 36V over 30 cells means that each is at 1.2V, which may not always be the case, but the nicads will tend to balance themselves with multiple charging cycles because the first to fill with charge will just get hot as the others catch up.

[rickhoover]

These are NiMH, does that matter?

[dnmun]

nope, same thing. a little harder for the charger to see endpoint is all.

[rickhoover]

So I should be all clear to ride them w/o hurting them?

[dnmun]

they seem as balanced as you can make them, and should get closer if you keep the discharge to a minimum as the pack balances more with each charging cycle.

then you have to do just the opposite, and try to get them all to discharge as low as possible to stop the memory effect from reducing the capacity. but that is for later.

[rickhoover]

okay, TY!

[ambroseliao]

Hey rickhoover,

Any news? Is the pack good?

Ambrose

[rickhoover]

The pack appears to be a dude, as it will only get me a mile or less get me a mile at best before the bike beeps and shuts down (I think it overheats). I can then restart it and ride a bit more before it does the same thing again. The 3 LED charge indicators move to 2, and pretty soon thereafter to 1. The little cruise indicator is much slower on 1 as if the system is trying to conserve energy. The battery seems no better than its predecessor, maybe worse, and I am currently working on getting some sort of a refund from Hong Kong!

[rickhoover]

I meant dud, not dude, dude.

[rickhoover]

Greetings folks, R U still reading this forum? I've had to give the eBike project a break for a month but now I'm back on it. If U R reading, could you please advise me on whether converting to a LiFePO4 might be great or terrible idea. There is an eBay seller in China who will build me a 36V 10Ah pack that will fit inside the original Ni-mh battery's case (and I presume would be much lighter an more efficient). Would you recommend this route, or should I continue to look for a reputable Ni-mh set. I had to get a refund for the last Ni-mh set mentioned in this thread. It was advertised at 10Ah but ended up running more like 1Ah or less. It seems like the cost of the LiFePO4 won't be much more than the pricier Ni-mhs, and I won't have to build it either as the seller will do so; and it comes w/ charger too. Any suggestions?

[dnmun]

why do you need to make a pack that would fit in the old nimh case? you can buy a 48V20Ah pack for $500 delivered from sun-thing on ebay.

http://stores.ebay.com/sun-thing28/LiFe ... 34.c0.m322

[rickhoover]

Well first off it's a 36V motor/controller set-up, so I think I'll stay in the 36V range. Secondly, keeping the pack mounted inside the original case means added security to the pack whenever I leave the bike locked up at the mall, store, etc., as the case locks into the frame of the bike. Thank you for your suggestion.