CHARGING w/MULTIPLE CHARGERS

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Joined: 09/09/2008
Points: 33

Alittle birdy told me once that you could take the pos. out of a 36 volt charger, attach it to the negative of another 36 volt charger and achieve 72 volt charging...................................
TRUE OR FALSE?????????????????????????????????

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reikiman
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Joined: 11/19/2006
Points: 8444
Re: CHARGING w/MULTIPLE CHARGERS

True.. though Chas is going to pop in and say the chargers must be isolated. Not sure what "isolated" means. Every time I've tried this it works so maybe I've been lucky with my choice of chargers.

You're talking about a pseudo-bank charging system.

On my motorcycle it has a 60 v battery pack. The charger setup is a 24v, another 24v and a 12v charger. Pretty much the same idea as you say though done slightly differently.

I connect the charger + and - to the + and - of the batteries, rather than connecting the chargers together. Oh.. come to think of it the thing you're suggesting is probably a nonfunctional idea. Depends on precisely what you mean. If you mean to wire two chargers in series and connect the + and - of the resulting series chargers to + and - of the pack, I think that will not work. What will work is the bank charging approach where you connect one charger to a 36v substring and the other charger to the second 36v substring.

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- Electrified Electra Townie, 1971 Karmann Ghia (since sold), Kia Soul EV

garygid
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Joined: 12/19/2008
Points: 441
Re: CHARGING w/MULTIPLE CHARGERS

The birdie was only correct IF the outputs of the chargers are ISOLATED (from any common wiring). Connecting two non-isolated outputs + to - will be much like shorting one charger's "+" output to its OWN "-" output. In general, NOT a good idea!

If you do not know what "isolated" outputs are, or what an isolated series of batteries is, then you will probably short out chargers, battery strings, or both, and damage or destroy both, and possibly injure yourself gravely.

Isolated basically means not connected (wired, internally or externally) to other circuitry.

So, learn about this first. Six cells all in series, ... they are connected by wires, thus NOT isolated. Three cells in series and another 3 in series, with the first series NOT connected to the second series, and neither series connected to anything else, ... is two isolated 3-cell series.

An isolated string of cells in series can generally be charged by any charger that is suitable for that string of cells.

But, if strings of cells are NOT isolated, one MUST use chargers that have isolated outputs, or ... snap, crackle, and pop!!!

BIG DANGER, Will Robinson ...

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Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

Rodifications
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Joined: 09/09/2008
Points: 33
Re: CHARGING w/MULTIPLE CHARGERS

So chargers cannot be ran in series IE , two 36 volt chargers to charge a 72 volt pack.
OK then how can I limit the current on a 36 volt 25 amp charger so I dont burn up 6 20 amp hour SLA's?

garygid
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Joined: 12/19/2008
Points: 441
Re: CHARGING w/MULTIPLE CHARGERS

1. Isolated-output chargers can be run in series. Chargers with non-isolated outputs cannot.

2. Putting chargers in series does not change the charging current.
You should use chargers that are suited to the batteries that they will charge.

3. Get help with your project.

__________________

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

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