Battery Charger OCP

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Little Bill

Little Bill

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Fork lift battery charger nameplate says "In AC- 240V, 8.0 KVA, 33.3A
What if the voltage is 208V?
Would this be considered a continuous load?
 
Little Bill said:
Fork lift battery charger nameplate says "In AC- 240V, 8.0 KVA, 33.3A
What if the voltage is 208V?
Click to expand...
Presumably the question is whether a battery charger generally behaves as a constant power load (I goes as V-1), a constant current load (I goes as V0), or a constant resistance load (I goes as V1).

masterinbama gave you the constant power answer, but my minimally informed guess would be constant current.

Cheers, Wayne
 
Little Bill said:
Fork lift battery charger nameplate says "In AC- 240V, 8.0 KVA, 33.3A
What if the voltage is 208V?
Would this be considered a continuous load?
Click to expand...
does the NP allow for 208 V input?

my inclination is that the battery charger will pull no more than 33.3 A RMS regardless of the voltage.
 
While the charger is left connected to the forklift overnight (and lunch break, but that is clearly less than 3 hours!), the charging current falls back as the batteries are charged, so most likely not pulling 8 KVA for more than three hours.

Now if it is one charger for many forklifts, maybe they do keep cycling forklifts onto the one charger so it is a continuous load.
 
wwhitney said:
Presumably the question is whether a battery charger generally behaves as a constant power load (I goes as V-1), a constant current load (I goes as V0), or a constant resistance load (I goes as V1).

masterinbama gave you the constant power answer, but my minimally informed guess would be constant current.

Cheers, Wayne
Click to expand...
Should have phrased it that way. I know Ohm's law but sometimes you have to figure it different, such as constant resistance or not.
 
Frank DuVal said:
While the charger is left connected to the forklift overnight (and lunch break, but that is clearly less than 3 hours!), the charging current falls back as the batteries are charged, so most likely not pulling 8 KVA for more than three hours.

Now if it is one charger for many forklifts, maybe they do keep cycling forklifts onto the one charger so it is a continuous load.
Click to expand...
how can it be continuous if they have to unplug one forklift to plug another one in.
 
The Exide system 3000 charger I am familiar with has transformer taps for 208 service. It is a three phase input charger. So input current on 208 is higher than the 240 input on the nameplate. Since it is transformer derived internally, I would think a unit wired for 240 would pull less amps on 208 input. That is my SWAG. ;)
 
230710-1357 EDT

Think about the circuit for a simple battery charger. But keep in mind a much more complex circuit can be designed.

A simple AC supplied battery charger is a transformer with some internal impedance, a rectifier, and possibly some additional resistance connected to the battery being charged. The internal impedance may be highly inductive in the transformer.

The load current on the charger will be a function of all these parameters and the characteristics of the battery. As the battery is charged its internal voltage will rise some.

Thus, you figure out, measure, the characteristics of the battery as it is charged. Most chargers are designed to use a way over charge rate to quickly charge a battery, and a timer to terminate how long this high charging rate is supplied.

In an automotive charging system two regulating functions are applied via a pair of relays.

.
 
The old forklift chargers were usually multi volt, 208,240 and 480. Required changing taps and fuses. The new ones are not that way anymore, they have to be ordered for the exact voltage, so it is looking like you will need to boost it.
 
If the charger is regulated on the DC output side, there is a question is whether 208V AC input through a simple rectifier circuit will deliver a high enough DC voltage for the charger to work properly.
If designed for the nominal 240 AC voltage tolerance it may work well if the 208V is on the upper side of the band, but not at the lower end.
Depending on the system design, a voltage tap on a control transformer may not be enough to make the system work.
 
GoldDigger said:
If the charger is regulated on the DC output side, there is a question is whether 208V AC input through a simple rectifier circuit will deliver a high enough DC voltage for the charger to work properly.
If designed for the nominal 240 AC voltage tolerance it may work well if the 208V is on the upper side of the band, but not at the lower end.
Depending on the system design, a voltage tap on a control transformer may not be enough to make the system work.
Click to expand...
The last new one I installed was non-adjustable. They sent the wrong one, and they returned it for the correct voltage. The manufacturer said it had to be the rated voltage because of the electronics they now use for efficient charging rates.
 
Here is the nameplate on the charger. It is not a new charger. They want it moved to another building and I'm thinking it was on 208V but not sure since the building has two services.

 
So it has jumpers and taps; you're golden.

I would use constant-power calculations for the current.
 
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