Odd lengths of wire between batteries.

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carbon.nanotube.capacitor   10 W

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Odd lengths of wire between batteries.

Post by carbon.nanotube.capacitor » Dec 01 2008 9:05pm

Hello fine feathered friends, and tarred friends. And you,

I've got this issue see... Instead of running my electric Kaishan e-scooter on the regular 48 volt SLA battery pack, I'm running it on that and a fifth 12 volt SLA battery to make it a 60 volt system. I've made sure that all the batteries are the same capacity via a CBAII battery load tester, within about 0.8 Amp-hours... But the thing that troubles me is that the all-important fifth battery is under the seat of the bike, whereas the 48 volt battery pack is in the floor of the bike. All told there are about three feet of wire and two connecting Anderson clips between the 48 volt pack and the fifth battery. In theory, could this extra length of wire between two of the batteries cause them to become un-balanced when they are charged or discharged? And yes - I'll actually be using a 60 volt charger this time round, rather than the 48 volt and 12 volt chargers I'd tried to use before.

I swear if this doesn't work I'll move to a Mr. Fusion or something. And stuff.

-C
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johnrobholmes   1.21 GW

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Re: Odd lengths of wire between batteries.

Post by johnrobholmes » Dec 01 2008 9:19pm

It should pose no problem, other than resistive losses and possible voltage ripple if the load is high enough.

Are you charging them as one 60v pack?

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carbon.nanotube.capacitor   10 W

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Re: Odd lengths of wire between batteries.

Post by carbon.nanotube.capacitor » Dec 01 2008 10:10pm

That's good. Yeah, they are being charged with a 60v charger. Just want to make sure the extra cable length wont adversely affect any of the batteries when charging or discharging. If this works this will be a groovy upgrade for customers at our shop. You know how it is. By the way, 40km/hr with a silent direct drive hub motor is really enjoyable.

Tee-Hee!
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fechter   100 GW

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Re: Odd lengths of wire between batteries.

Post by fechter » Dec 01 2008 11:32pm

If the batteries are all in series, then the current in all of them will be the same. Longer wire increases total resistance, but won't cause any kind of inherent imbalance.
"One test is worth a thousand opinions"

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carbon.nanotube.capacitor   10 W

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Re: Odd lengths of wire between batteries.

Post by carbon.nanotube.capacitor » Dec 02 2008 12:44am

Thanks Fechter. :wink:
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cerewa   100 W

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Re: Odd lengths of wire between batteries.

Post by cerewa » Dec 02 2008 5:18pm

If it seems like the long wire is eating more energy than you want it to, all you need is a wire that is fatter than necessary...

Like fechter says, the wire will drop the voltage some, (under load only) but not the current. If the total voltage of the pack is dropped too much across the wire then you can always parallel it with another wire (or replace with fatter wire, or both)

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carbon.nanotube.capacitor   10 W

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Re: Odd lengths of wire between batteries.

Post by carbon.nanotube.capacitor » Dec 03 2008 2:45am

Thanks for the tip Cerewa, but not to worry as the gauge of the wire is substantial enough at 10. I was just concerned that the voltage drop across the one wire would mean a difference in voltages between the batteries, similiar to the effect of having batteries of varying capacities in a pack.
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