Charging AC500 from a gas generator not working

I can’t get my battery to charge when using my portable gas generator. The status page shows AC voltage and frequency but zero amps.
The gas generator does fine powering other AC loads and the battery charges when connected to AC power at home. The AC500 did throw a couple faults that I did clear to no effect (012. BUS Voltage High and 068. Grid Flicker). I also adjusted the mmax AC amps to 5, 10, 13, and the default 15A. I did get a quick glimpse of the status page showing 5 amps of charge when the max was set at 10 amps but it dropped back to 0 amps immediately.

Any ideas on what’s going on? Could this be a power quality problem with the gas generator (Harbor Freight Predator 4000)?
Any inputs welcome.

You may havr the same problem I have which is a higher AC frequency. My 7.2 kW Firman tri-fuel (propane, NG, gasoline) generator can charge my 240 VAC dual AC300 setup and supply my home, but the AC300 did not accept any current to charge its B300 batteries. I check the generator output and the AC frequency was 72 Hz unloaded. The AC300 user guide specifies a maximum of 65 Hz. I wrote to Firman and asked how to adjust the throttle linkage from the governor inside the engine. They told me to adjust a small screw near the air filter body, but I could only make it run faster, increasing the frequency, so I had to abandon any attempt to recharge by the generator.

Get a frequency meter and measure your output. If it is not between 55 and 65 Hz, try to adjust it. You may have better luck than I did.

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Its probably your generator. I’ve had the grid flicker fault when the AC500 switches from straight grid power (generator) to inverter mode when using my smaller generators (a 2000w and a 4000w) even though I had the max power set way low like you described. But it works fine with my larger Honda 7000w inverter generator even at 30 amps so I’m guessing the AC500 likes lots of clean power when in UPS grid mode. When using my smaller generators for lighter loads and better fuel economy I charge the AC500 with my T500 chargers which work well since they bypass the AC input.

Here is a photo of what the AC500 was getting at one point: 123.2V and 60.62HZ (and the 0 Amps as I mentioned above). These values would vary a bit as you watched. Frequency looks pretty good for the 55-65 Hz requirement. What is the voltage tolerance?

I pulled up the manual for Predator 4000 at
I found this interesting note:

NOTICE: This Generator is not intended to power sensitive electronic equipment without the addition of an appropriate line conditioner and surge protector (both not included). Sensitive electronic equipment includes, but is not limited to, audio/video equipment, some television sets, computers, and printers. Sensitive electronic equipment should be operated on approved inverter-type generators or pure sine wave generators

Unfortunately, it seems like you’ll need a pure sine wave generator (inverter generator) for things to work smoothly. I can attest that Honda EU series generators work well with my EP500P units.

I suppose another alternative may be to use the AC to DC adapters - such as T500, or multiple compatible chargers using solar input.

OK, sounds like the problem might be with the less then ideal AC output from the Predator generator that the AC500 is not able to process.

My options are to 1) get a better generator (like one of the Honda models as suggested above) that the AC500 will work with or 2) buy aT400/T500 Bluetti AC brick charger, as suggested above, to bypass the AC500 and charge the battery directly or 3) use the DC output of the Predator generator to charge the battery (either through the AC500 or direct to the battery). Options 1 & 2 seem to have some risk that they will also have problems. As far as the T400/T500 charger option goes, I have not had any problems using the Predator generator to charge a whole host of Lithium batteries (iPhones, iPads, computers, lights, jump start packs, power tool batteries…) so maybe the T400/T500 would work with the Predator also. Perhaps the AC500 charging logic for integrating multiple simultaneous inputs sources puts some additional constraints on the AC inputs. I haven’t explored the DC output option yet.

My application is an off grid cabin so I do believe I need this option.

No response from Bluetti yet to my tech support requests via phone and email.

Using option 3 is going to be very slow to charge, looking at the specs of the generator you have 12v 8A DC outlet (96 watts). Whilst the T500 provides up to 500w, allowing for relatively much quicker charging, you may be able to double with two adapters. Of course none of these compare to the 15A+ of the AC charger (1800 watt+).

I first ran a gas generator and my AC500 would not charge. I spoke to an electrician and gas generators produce erratic power levels and a modified sine wave and the Bluetti only wants clean power with pure sine wave flow. I switched to an inverter generator and everything works fine now.

I suggest you to use inverter generators because these gasoline inverter generator will supply exact 50Hz frequency that will help to work with the devices that are sensitives to exact 50Hz AC. also choose generators with at least 4KW

here are some sample gasoline generator that you can study about it
Gasoline inverter generators

I charge ac300p routinely with firman inverter generator 2000W gasoline powered, no issues after many hours and refuelings and oilings! The generator didnt cost alot more than a bluetti 500W power supply in fact.

Here is a update on my situation. I did get a response from Bluetti tech support and they have been helpful. Bluetti sent me a firmware update that did help some with keeping the AC charger from cutting out when run at lower amps but it still wasn’t acceptable. After about 30 min of charging I was able to get about a 20% charge delta with a single B300E battery. I did get the T400/500 DC charger and when plugged into one circuit of my gas generator and the AC500 on the other circuit (and the AC500 charger set at 5A) it will charge at about 800-1000W between the two chargers. It’s not the 1500W that the AC500 should be able to do but it is functional for me for now. I actually think that with the DC charger on one circuit of the gas generator that the power quality is better. With the AC500 AC charger set at 5A it charges pretty consistently but does drop out and reset occasionally. At any setting higher then 5A (7, 10, 13, or 15A) it won’t charge consistently. So for any others having this problem with a non inverter gas generator you can probably consider my case the lower end of what to expect. If I ever get a nice Honda generator and try it, I’ll post some results here.

I just purchased a AC500 3 months ago for our off grid property, same issue i have several gennys but none would work due to them not being in inverter genny, purchased a WEP 4500 at it works great .

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I’ve had my AC500 since last December. In March of this year we had a 50 hour power outage and the AC500 +B300S batteries did fine. I was able to charge the batteries with PVC and a Honda EU2200i inverter generator.
Today, we have another power outage and the AC500 will not accept a charge from the inverter generator.
It shows there is voltage and Hz but no watts. I suspect the generator is malfunctioning because the Hz varies from 59 - 60 and I don’t think it’s supposed to do that. Any ideas?