But let's do some bogus math. We'll assuming 100% efficiency, which is not going to happen by the way. We are also assuming a linear charging scheme, which is not the case. Lets also assume that the mx60 will charge a 48v system with a 12v input. Normally an MPPT charge controller is used to accept a higher voltage source for a lower voltage battery, not the other way around.
So you are at 80% of 220AH, which is to say you are down 44AH. 44AH at 48VDC is 2112 watt hours or 2.112Kwh. Your Generator is going to provide 100 watts per hour, so you'd need 10 hours to get 1 Kwh. You'd need 20.1 hours to provide the 2.112Kwh you need. In real life, it will take much longer.
If you have the above scenario, it will take you twice the time if you double your battery capacity, assuming 80% of 440AH @48VDC.
Many inverters (Prosine, Trace, Outback etc) have built in chargers that accept 120v AC and allow you to charge your batteries with a gas/diesel generator with much greater efficiency than the above scenario.
As with any charger, the amount of time this requires will depend on the charging algorithm of the charger, the size of your battery bank, the temperature and the state of the batteries.
My generator (also 5kw rated) has 20 amp breakers, so I can't supply more than 20 amps anyway, and that includes what I'm using while it's charging the battery. So I usually set it to provide about 16 amps for charging.
Your calculations will have to take into account the settings in the charger. A decent charger will allow you to specify things like the type and size of battery, high (bulk) voltage settings, temperature sensor (or not) and so on. This will prevent overcharging the batteries.
Every charger has an algorithm (Outback has a 5 stage charging algorithm) which limits the input depending on time and the voltage at the battery. So you may be putting 16 amps in for 10 minutes. It then ramps down to float voltage, where it stays or possibly drops down, while you waste gas, until it hits a set point and then charges up to bulk again, etc. You could be idling for hours.
I usually run it for a few hours to make sure I'm at float and turn off the generator. Most decent chargers have LCD panels that will tell you the voltage and amperage going into the batteries. If it's extra, pay the money. It's worth it. The temperature sensor too.[ Parent ]
