Another Small Generator Question

[Lin]

This is again regarding my Honda eu1000.  As I remember it, it has a running capacity of 800 watts.  I use it to charge the house batteries.  By my logic, 800 watts at 120v should give me around 6.5 amps, which would translate to 65 amps at 12v.  The problem is that if I use to charge the batteries through the inverter, the generator overload protection kicks it out somewhere between 25 and 30 amps at 12v according to the inverter charge rate display.  Why that is?

[belfert]

Battery charger in the inverter is probably not 100% efficient.  My inverter in charge mode uses almost twice the 110 volt amps you would think it should to charge the batteries at 24 volts.

[pvcces]

Lin, I think that the inverter does not know what the power source is and it will only try to limit the recharge if the battery voltage climbs high enough OR it hits the power sharing limit. If you could get the inverter to limit the recharge to the maximum output of the generator, you ought to get something like 55 amps recharge at 13 volts.

You didn't mention which inverter you are running, but many of them have a setting that limits the draw on the shore cord so you don't keep blowing the breaker. You not likely to get a perfect match, but you should be able to find a setting that will be low enough to keep you from popping your generator breaker.

Good luck.

Tom Caffrey

[Lin]

Belfert-- I guess it would make sense if the inverter charger was that inefficient.

Tom-- It's an old Trace U2512 inverter/charger.  I will have to check since it's been a while since I set the inverter up, but I think there is an adjustment to set the maximum charge rate.  Anyway, I have a Ctek charger that does 25 amps max so I can use that if I am going to be limited to around that amperage anyway.  I had thought that I would be able to do 50-60 amps through the inverter and cut down on generator time.  I will experiment as you suggest to see what the max I can get is.  In any case, this is better than running a 7.5kw generator as a battery charger.

[boogiethecat]

It's because your inverter is not power factor corrected.  The honda generator is rated for it's full power going into a resistive load- getting somewhat technical a resistive load's current draw looks like a sine wave- same as the voltage, and in phase with it.  But a lot of electronic devices draw current in a manner that looks very distorted as compared to a sine wave- without getting into a lot of detail,  you can consider it this way- if you draw 1000 watts in a DC system say at 100 volts, you'd be drawing 10 amps.  You can get that same 1000 watts by rapidly turning the system on and off (for example at 60hz)-- on for 10% 0f the time and off 90% of the time, and drawing 100 amps for that time it's on.  Make sense? volts times amps = watts but chop it up in time and the on-to-off ratio is also part of the equation. Overall it's still 1000 watts but now the power supply for this example has to be able to supply 100 amps instead of 10 even though it's only for a short pulse each time the switch goes on...

Bottom line, most electronic stuff that is older draws power in a manner similar to the way of the DC example above.  It doesn't draw a thing until the instantanious voltage  of the sine wave is up to around 100 volts, then there's a heavy current draw that  continues as the sine wave crests and goes back down to 100 volts, then from there through zero and back up, nothing.  It compresses it's current draw into a smaller chunk of the sine wave making the actual peak draw larger than would happen if it was a resistive load.

Being that the honda inverter does not actually measure wattage; instead it measures the instantanious current it's putting out- and it faults if that value gets any higher than 8 amps or so, it won't allow a load like this to get anywhere near full power without throwing a fault.

In the past few years, electronics stuff has been required to have "power factor control" built in.... this is an entirely additional hunk of circuitry that makes any load  presented to the power line "look" like it's resistive.  This is done because (metaphorically speaking) loads like your old inverter beat the power line up whereas resistive loads don't and the power company likes to not get their lines beat up....

IF you get a charger or inverter that is "power factor corrected" you'll be able to utilize the entire 1000 watts of the gene
ramble ramble ramble.....

[luvrbus]

I thought those 900 watts at best then you factor in altitude,temps and the humidity they drop in a hurry ours is pretty much useless in Texas and Idaho

[Lin]

Boogie, thanks for the explanation.  I figured that there was something involved beyond that simple arithmetic I was using.  Since my Ctek 25 amp charger works, It will be good enough.

Clifford-- they call it a 1000 watt gen, but only rate it at 800 watts continuous.  I'm sure that is at optimum conditions too.  However, it is good enough for a battery charger. 

[luvrbus]

Not good enough for coffee pot I found out @ 8000 ft

[Lin]

Yeah, It looks like a 4 cup pot uses about 650 watts and a 10 cup pot uses about 1200 watts.  If I came across the 2000 at a great price, it would be better.  I got this one as a barter when trying to get rid of some stuff, so I'm pretty happy with it so far.  As mentioned before, running the 7.5 kw generator for an hour just to charge batteries seemed not only ridiculously wasteful, but also could not be that good for the generator.  This little generator is a good solution.  Theoretically solar would be ideal, but we generally like to be in the shade if we can.