ZZSPIRAL1 wrote:
Okay, if I understand correctly:
2. If we assume the generator provides 7.5 amps of power into the converter, then simple math says the converter will provide 10 times that (75 amps) into the battery. This is because the generator provides 120 volts and the converter converts it to 12 volts.
5. If I understand this correctly, considering I have a 85ah of battery and a converter with a maximum output of 13.6 to 14.4 Vdc, if I'm not using much power when the generator is on (i.e. not using the microwave), then it doesn't matter whether I use a 1000W generator or a 2000W generator, because they both provide more power than the output of the converter.
There's more to it. Most generator advertising unfortunately (and deceptively) advertises the generator ratings in watts, when it's actually rated in VA. Assuming you don't have a power-factor-corrected converter (applies to most converters), here's the math:
120 volts * 7.5 amps = 900 VA
* 0.7 power factor = 630 watts on the AC side
* 80% converter efficiency = 504 watts DC output
= 37 amps DC at 13.6 volts, or 35 amps DC at 14.4 volts
A 45 amp converter is at the borderline and can overload a 1,000 VA inverter generator, and the same situation exists with an 80 amp converter and 2,000 VA inverter generator. A non-inverter generator can drive a bigger Progressive Dynamics converter because it operates at reduced output. A WFCO converter on one hand is more likely to operate at its full power with any generator, but on the other hand is less likely to ever go into boost mode. With your small battery it's possible you will never overload a 1,000 VA generator with any converter, but if the converter is bigger than about 40 amps, the possibility exists.
The simple math fails for 3 reasons: 1) Doesn't account for power factor, 2) Doesn't account for converter efficiency, 3) Assumes a 10-to-1 voltage ratio, which is not the case for 120 volts to 13.6 or 14.4 .
