Two chargers on one circuit.

DJD

Hi.

I work at an airport FBO where we use three EZGO golf carts throughout the day to chase airplanes, carry bags, and transport customers.

Before today we had a single charger for all three carts, but I managed to fix our old one so now we have two.

Our garage we keep the carts in only has what I figure to be 1 20 or 30 amp circuit. When I plug in one dead cart I get charging starting at around 17 amps or so, then it trickles down over night as it should. When I plug in 2 chargers and 2 carts, each charger only seems to show a max current of about 12 amps.

Getting to the question...

Will the longer charge at the lower current be harmful to the golf cart batteries? I'd much rather be able to charge 2 carts at a time over a longer period vs. one at a time.

Thanks!

BGW

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bigstik40

There was a very, very, long thread here recently addressing this question and I think the bottom line answer (from Trojan) was that the lower initial current was ok but total time would be longer. I don't think everyone agrees with that answer. I'm really not sure myself.

If you could manage it, one solution would be to stagger when you plug in the chargers. If you can wait until the first charger drops to a lower current before you plug in the second one may allow you to get to the higher initial charge current on both chargers. I'm sure others with more knowledge than me will be along. - RAY

yurtle

I'm not sure how sharing a single 20 amp circuit could possibly affect charging current. The charging current is for 36 or 48 volts DC, and the 120 volt current is much lower.

A circuit breaker doesn't limit the current, it simply opens if that current is exceeded. It's possible you may be slightly current limited by the conductors, but if they were sized correctly, that shouldn't be the case. If the conductors were way undersized, any voltage drop results in heat, I^2R. I suspect you'd be smelling it if this were the case.

JohnnieB

I agree with both replies.

The modestly lower charging rate won't adversely affect the batteries as long as they are allowed to charge long enough to be fully charged.

Unless something else is plugged into the 20A 120VAC branch, or the shop wiring is bad, two chargers shouldn't drop the voltage enough to lower either chargers output amps.

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I'm speculating, but I suspect the two chargers are setting next to each other.
If they are, try moving them about two feet apart.

(The ferroresonant transformers put out huge magnetic fields and they can cross couple)

yurtle

Please report back if this is the case. That would be kewl!

TerryH

Hmmm... I will have 5 chargers in series on 1 cart for our drag cart. I guess it could get really interesting.

yurtle

How do you connect five chargers in series? 120*5=600???

TerryH

Sorry. Should have clarified. The outputs are connected in series. 204 volts total output.

yurtle

Kewl.

I've done this with AC step up transformers (up to 25 kV each), and worry about secondary to core stresses. Proper phasing is important,wrt innermost winding, but with step down transformers, this shouldn't be an issue.

204/5=40.8 vdc each. I assume these are 36 volt chargers?

JohnnieB

Maybe a typo?
5 X 48 = 240

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I accidentally discovered the magnetic field thingy when I was playing with a PW-II charger.
I had the relay bypassed and heard the magnet in the output plug start singing when I laid in down on the workbench next to the charger. The charger's case was off at the time, but I later tried it with the case on and I could get the magnet to vibrate from about a foot away from the case.

I'm not sure of the net effect of operating two (or five) ferroresonant transformer type chargers setting next to each other would be, but the output amps is determined by core saturation, so reduced amps in the output is a possibility.