I have a Yamaha 1000w generator that's been having carburetor problems and wouldn't run anything without stalling. I finally took it in and had it fixed, so it was time to test my battery charger to see if the generator would run it. I have an Iota DSL-45 charger with the IQ4 LiFePO4 charge controller. 45amps X 13.8V=621 watts so my guess was that the generator would be right at it's capacity by the time you figure in losses and power factor. The Yamaha is rated at 900 watts continuous. I ran the battery down to 55% capacity, about 80 amp-hrs, to make sure the charger would be in bulk mode. I started the generator and plugged in the charger. The generator lugged a bit, then stabilized but the charger rolled back its output to around 30 amps rather than the 45 amps at full output. Then it continued to roll the output down till it was at 17 amps. Here's a graph showing the amps starting to roll off from 30A.
I unplugged from the generator and plugged it into utility power, and the same thing happened. WTF? I unplugged the charge controller and plugged it back in and boom, 46 amps. The charger maintained 46 amps till the battery was charged. You can see where I unplugged-plugged the controller as the current jumps up to 46 amps This is the entire charge cycle:
Interestingly, the voltage jumped up from 13.5 to around 13.8V with the current bump, which is in the recommenced range for LiFePO4 charging. I like how the charger changes mode at about 14V and tapers the current down to nothing until the battery is at 100% charged. Here's a close up of the charger finishing up:
I used a Kill a Watt to measure some AC electrical parameters while the charger was full output:
Drawing 8.8 amps at 120V:
796 watts output the generator with 634 amps going into the battery. That's about 80% efficiency while charging at full output:
Power factor is awful, as low as 0.6 when the charger was at 20 amps, rising to 0.7 when loaded:
The real surprise was the Volt-Amp load; I wouldn't have guessed the generator would carry this since the power factor is so low. A 0.8 power factor is what most commercial generators are rated at:
So here's some conclusions I've drawn from this test.
-I'll keep my 1000w generator, I was considering trading up to a 2000 but I don't need one yet. The generator won't run the A/C so if I do upgrade it will be to run that.
-The generator wouldn't run in eco mode, it needed to be at full RPM to carry 46A.
-The Iota IQ4 Charge controller has a float mode that holds the battery at 13.5V for 15 days without charging. Then it will switch to bulk mode, charge it back up and return to float mode. I think the reason it wouldn't charge at full output was because it was stuck in float mode. Unplugging the controller reset it. I need to do some reading and see if anyone else has noticed this. Other than that, I like the charge profile of the Iota.
-45A is definitely the largest charger I would run on a 1000watt generator. Its also about the largest charger I can use with my battery. 180 amp-hrs X 0.3C= 54A is the maximum recommended charge rate.
-It's really cool that I can replace 90 amp-hrs of capacity by running the generator two hours. I would have needed a full day to charge lead acid batteries back from that level.
-I use Victron Venus software running on a Raspberry Pi to track the battery voltage and current. I'd never know what was going on without it.
-I haven't had to run my generator while camping for a couple of years now, the PV array usually takes care of what we use. I like to have a backup power source since our fridge is electric.
Bruce