Invertor/charger drawing too much current from generator

[robind187]

I have a Sterling Combi S invertor/charger to charge our batteries from the engine when moving. I have just bought a second-hand Honda EU20i generator (2kW) as a back-up for charging the batteries. The generator starts up ok, but when I have let it run for a minute then connect it up to the invertor/charger using a fly lead socket converter and a fly lead it charges for a couple of mins at 70A then the generator starts struggling, pulsing then cuts out. I have read that the 70A continuous draw may be too much for this generator. Is there a way to limit the current coming into a Sterling Combi S inverter/charger? I can't see anything in the manual about this. Thanks in advance

[nicknorman]

70A is only around 1kw and so shouldn't be a problem for the genny. It sounds to me more like a fuel starvation issue - when the genny is working hard it is pulling more fuel through and perhaps not enough can flow, or the tank vent is blocked and a vacuum develops in the tanks. From an electrical point of view, if the engine can run the genny for 2 mins it should be able to do so indefinitely. If the electrics were overloading they would just cut out, without making the engine run badly.

Edited May 17, 2017 by nicknorman

[Alan de Enfield]

23 minutes ago, robind187 said:

I have just bought a second-hand Honda EU20i generator (2kW

That generator is actually 1600w continuous rated.

 

Are you trying to run something via the inverter at the same time ?

[MtB]

Sounds to me as though the manually closeable air admittance valve on the fuel filler cap is closed!

[robind187]

There's nothing else running off it (it's in charge only mode) and the air admittance valve is open.

[rusty69]

Just now, robind187 said:

There's nothing else running off it (it's in charge only mode) and the air admittance valve is open.

Dirty spark plug/incorrect gap? 

[nicknorman]

4 minutes ago, robind187 said:

There's nothing else running off it (it's in charge only mode) and the air admittance valve is open.

Maybe a blocked fuel filter?

[WotEver]

Definitely sounds like the Honda needs a service. 

[robind187]

Seems like it. How much is a typical service? I'll have a go at cleaning the carb over the weekend and see if that helps

[smileypete]

To add to the suggestions try fresh fuel if the existing has been standing around for long.

A way to confirm the genny is at fault could be to try running a 1500W heater (just under the max 1600W load.)

If the charger is running near max output eg 70A, some chargers need a much bigger geny due to 'poor power factor' but that doesn't sound like the case here.

[robind187]

I've re-checked my maths and 70A at 13ish volts should only be 910W, so the generator should be able to handle that, no? Fresh fuel is a good suggestion as it may have been sitting around for a while. The air filter looked clean but the pre filter was missing. Is cleaning the fuel filter worth a try? I see there's a 15-minute tutorial for how to do that on YouTube.

[nicknorman]

7 minutes ago, robind187 said:

I've re-checked my maths and 70A at 13ish volts should only be 910W, so the generator should be able to handle that, no? Fresh fuel is a good suggestion as it may have been sitting around for a while. Is cleaning the fuel filter worth a try? I see there's a 15-minute tutorial for how to do that on YouTube.

There is a thing called Power Factor which means that extracting 910w out of a mains supply can use a lot more than a voltage and current product that gives 910w. However unless the Sterling unit is a complete pile of junk it will have "active power factor control" which will keep the power factor near unity, thus the genny should easily be able to cope.

If it starts and runs OK under load for 2 mins, I doubt the issue is old fuel.

Yes as I said before, it sounds like a fuel starvation issue, check and clean the fuel filter. Also even though you say the air admittance valve is open, might be worth trying it with the fuel tank cap loosened right off and/or check that the valve isn't blocked.

Edited May 18, 2017 by nicknorman

[Alan de Enfield]

5 minutes ago, robind187 said:

I've re-checked my maths and 70A at 13ish volts should only be 910W, so the generator should be able to handle that, no? Fresh fuel is a good suggestion as it may have been sitting around for a while. The air filter looked clean but the pre filter was missing. Is cleaning the fuel filter worth a try? I see there's a 15-minute tutorial for how to do that on YouTube.

But - you are not allowing for the Power Factor.

When I was looking to replace a battery charger I contacted most of the major manufacturers / distributors asking what the Pf was for their  charger some of the results were horrifying and where a low as 0.65.

This mean that you need an awful lot more  'oompf' - so - at 0.65Pf and 70 amps you would need 1400 watts

[nicknorman]

6 minutes ago, Alan de Enfield said:

But - you are not allowing for the Power Factor.

When I was looking to replace a battery charger I contacted most of the major manufacturers / distributors asking what the Pf was for their  charger some of the results were horrifying and where a low as 0.65.

This mean that you need an awful lot more  'oompf' - so - at 0.65Pf and 70 amps you would need 1400 watts

Isn't there a CE limit on power factor for stuff taking more than 70w these days? Stuff with a switch mode type of power supply surely has active power factor control unless it's archaic? Our Mastervolt Combi has a power factor better than 0.98

 

Anyway, an electrically overloaded inverter genny doesn't cause the engine to run rough and cut out.

Edited May 18, 2017 by nicknorman

[robind187]

From a quick search, this generator has a power factor of 1. I'll check the fuel filter when I'm back at the boat next week.

[nicknorman]

Just now, robind187 said:

From a quick search, this generator has a power factor of 1. I'll check the fuel filter when I'm back at the boat next week.

No, the generator doesn't have a power factor. It is the power factor of the load (ie the charger) that is relevant.

[mross]

1 minute ago, robind187 said:

is generator has a power factor of 1

Until you connect a load that's probably true  

[Alan de Enfield]

2 minutes ago, nicknorman said:

Isn't there a CE limit on power factor for stuff taking more than 70w these days?

No idea.

Matervolt (the best) and Victron (2nd best)where both 'high' - much of the 'others' were around the 0.75 area.

As usual its pretty much down t you get what you pay for.

There are reasons why a Victron 50A charger s £600, and an 'ebay special' s £100

[WotEver]

Just now, nicknorman said:

No, the generator doesn't have a power factor. It is the power factor of the load (ie the charger) that is relevant.

But either way, as already stated, if the genny runs for 2 mins then the problem isn't too big a load, it's fuel starvation (or something very similar). 

[robind187]

Right ok. The charger has a power factor of between 0.9 to 1 so should still be fine.

[nicknorman]

Just now, mross said:

Until you connect a load that's probably true  

Well not really. Power factor is the degree by which the current is out of phase with the voltage, but if there is no current (because there is no load), there can't be a power factor. But I know what you mean!

[mross]

A volt meter or 'on' led would be enough !  Probably some voltage regulator or overload coil also.  

[Dinz]

1. If oil in EU is old or low the symptoms you are describing can occur. Watch genny & see if red oil [level] light flickers.

2. You are 12V & not 24V?

Edited May 19, 2017 by Dinz