matching power supply with DC charger

[DjSpaceGhost]

This is probably an idiotic question.. but when using a dc balance charger that requires an ac power source, does the AC power source have to match the DC chargers output current/wattage ? For example : a 600watt 25amp max balance charger - Does the AC power source also have to be capable of supplying 25 amps to get a 25 amp charge rate ? I have no desire to charge at that rate, just using those numbers as max theoretical output.

 

[amberwolf]

The PSU needs to be capable of more *output wattage* than the RC balancing charger will need, but the current need will be determined by the charger's max current draw at the voltage the PSU will be at.

If it doesn't say, then you can guesstimate:

If the PSU is 12V, and the RC charger is 600w output, then assuming say 80% efficiency (best guess, could be better or worse), 1 / 0.80 = 1.25. 600 * 1.25 = 750w. 750w / 12v = 62.5A max current draw to get the 600w output max of the RC charger (assuming 80% efficiency of the charger).

If the 12v PSU is only 25A, then you can only get 12 * 25 = 300w out of it.

If the PSU is instead a 24v unit, then you only need 31.25A to get the same wattage output.

 

[DjSpaceGhost]

What I was looking at is in fact 24v , but only 5amps max, I think . Thank you for that explanation. You saved me from buying some junk that would have been a waste of money.

 

[john61ct]

When the voltage of different components varies, converting to Watts helps keep things straight.

The power required from upstream will always be higher than the output desired.

10-15% loss at each step is usually a reasonable assumption.

Of course a higher available input is never a problem.

Just make sure if the downstream demand is higher than a source can produce, cheap components often do not handle overcurrent in an elegant way, or may even burn out.