Mismached AGM batteries?

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eNaught
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Last seen: 9 years 5 months ago
Joined: Tuesday, June 15, 2010 - 10:23
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Mismached AGM batteries?

I have to replace one of the batteries in my 8 battery 96v system and I am wondering how important it is to get the same brand and model number as the the rest of the batteries in the pack? Can I just match the specs with a different brand/model and be okay? These are AGM batteries.

A little background info: This is my first EV and I just got it driving about one year ago so I am new to this stuff. I have a PakTrakr BMS installed and all seemed to be going well until about three months ago when I got in the car for the first time in about a week and noticed that the PakTrakr display would not turn on. I found that the voltage of the most positive battery in the front pack (the one that the PakTrakr system draws power from) was down to about 5 volts (bad, I know) although the other 7 where fine. I had no time to deal with it at the time so I disconnected the drained battery from the rest of the system and put the car on hold until now. At this point, the drained battery is down to a terminal voltage of about 1v and I believe there is no saving it. If anyone has an idea of why this battery drained so fast I would love to hear it. Thanks.

colin9876
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Joined: Thursday, October 23, 2008 - 11:37
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Re: Mismached AGM batteries?

How many amp hours are the batts?
Fine to use a different brand as long as similar Ahr capacity

Just make sure its at the same SOC (state of charge) when u add it in.
e.g top up all 7, then add ur new one in fully charged so they all read similar voltage at start.

Oh and that PK TRK is whats messed it up, not the first time Ive heard that, crazy design draining one bat. Just use a cheap voltmeter to assess the battery level!

eNaught
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Last seen: 9 years 5 months ago
Joined: Tuesday, June 15, 2010 - 10:23
Points: 4
Re: Mismached AGM batteries?

How many amp hours are the batts?
Fine to use a different brand as long as similar Ahr capacity

Just make sure its at the same SOC (state of charge) when u add it in.
e.g top up all 7, then add ur new one in fully charged so they all read similar voltage at start.

Oh and that PK TRK is whats messed it up, not the first time Ive heard that, crazy design draining one bat. Just use a cheap voltmeter to assess the battery level!

Thanks colin9876 for the quick reply. The batteries are 105A.H. The PK TRK design does seem unreasonable... The instructions say not to switch the power because the module must go through its initialization procedure every time the power is toggled and this is only supposed to be done once when the batteries are at full charge. Not switching it however creates a constant drain on just one of the batteries in the pack which is obviously not a good idea either.

-eNaught

antiscab
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Last seen: 2 weeks 4 days ago
Joined: Saturday, July 7, 2007 - 23:55
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Re: Mismached AGM batteries?

I would suggest charging the first battery in the string separately to the rest of the pack.

Ideally, install an extra battery to be the first battery in the string, so that you don't have to change your charger aswell.

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion

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