Generator running rough while charging

[agagescu]

I got a cheap generator from a friend (Hoteche). It runs fine with even a large load but whenever I try and charge off of it, the RPM starts varying up and down about once a second. Full RPM to idle back to full RPM and so on.

I put an electric grill on the genny just to see whether it would handle the load and it was perfectly fine. The RPM went up and stayed there.

So I'm wondering whether the circuitry in the DPS-600PBs I'm using in series (AC float) is doing anything to mess with the inverter or the governor on the genny. The load I put on the chargers doesn't matter. It does the same thing at 100W or 750W. The only thing that changes is the top RPM.

Anyone run into this or seen similar?

Thanks,
Alex

[Gregor99]

What charger is this? Are you charging 6s packs?

[Slyster]

What generator (got a link?) showing specs etc?

[desertstalker]

Switch mode power supplies draw power in short bursts (to keep the capacitors topped up), this will often drive a non-inverter type generator mad as it keeps trying to adjust for load.

This is not likely good for your PSUs either as the AC input will be all over the place.

[agagescu]

The generator is Hoteche 1200W. There is no other model number on it. Had a look at their site (http://www.hoteche.com/) but this model is not there and seems older than anything listed. It does seem to have an inverter on it as it varies the RPM according to load. My understanding was that the old school generators ran at a fixed RPM to produce 120v / 60 hz. Is that wrong?

The charger is a 3010 or 720i duo. Doesn't really matter. Once the load goes up on the PSUs it does the same.

As for what I'm charging, ideally I'd like to do 6 x 6s 5300s at a time at about 1C or 800W with some room left over for a RX pack here and there. But that doesn't matter either because the genny does the same thing no matter the size of the load on the PSU. I've tried 1x 3s 2200 @ .5C i.e. ~15w

I think Desertstalker hit the nail on the head where the SMPS is topping off the capacitors every second or so and the genny is trying to keep up with the changes. Amazingly the PSUs did a very good job of keeping the DC side very clean even though the AC voltage was fluctuating a lot.

So what are my options? Spend $$$ on a eu2000i? Put a 24v deep cell in between this genny and chargers? Try to control the generator RPM directly?

Thanks for the input guys!

[desertstalker]

Originally Posted by agagescu

I think Desertstalker hit the nail on the head where the SMPS is topping off the capacitors every second or so and the genny is trying to keep up with the changes. Amazingly the PSUs did a very good job of keeping the DC side very clean even though the AC voltage was fluctuating a lot.

So what are my options? Spend $$$ on a eu2000i? Put a 24v deep cell in between this genny and chargers? Try to control the generator RPM directly?

Thanks for the input guys!

Its not every second its 60 times a second, whenever the AC waveform rises above the capacitor voltage there is a large current spike. The result is a drop in generator RPM (more load) and then the governor increases throttle to compensate, by this time the spike is gone and so the gen overshoots and so the cycle repeats.

The PSUs will compensate, but it is possible that the output voltage of the gen will exceed the input specs on the PSUs (less likely if the PSUs are 240V capable) and damage them (specifically the caps that are causing the issue to begin with).

You have 2 options, the first is to put buffer between generator and PSUs (a PC UPS will work for this), the 2nd is an inverter generator.