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# Posted: 21 Jul 2019 01:34am
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Hello all. I'm new to the forum and new to off grid living.
So my question is: if I have a 4000 watt generator and I'm only using 2000 watts is the excess power wasted?
Should I be trying to store the excess power in a battery bank?
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Piketeeth
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# Posted: 21 Jul 2019 08:42am
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You can use the excess generated power to charge batteries. When the generator isn't in use you can access that stored power. That's what we do, especially in winter when we have less daylight hours to charge our batteries by solar panels.
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Brettny
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# Posted: 21 Jul 2019 09:52am
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It really depends on the generator. Some burn alot more fuel when at max output some dont.
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Atlincabin
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# Posted: 21 Jul 2019 10:43am
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My experience has been that you can get two types of generator. One type will idle down automatically if there is no load on it and ramp up to full rpm when there is demand. The other runs continuously at full rpm. In either case, if there is any power draw, you will use more fuel than at idle. But like a car, you can go 60 mph on the flat and use somewhat less fuel than you use going up an incline. Generators are similar. Using 2000 watts of a 4000-watt generator will save you a bit of fuel, but not a huge amount. Better to have it running at near capacity and store the excess in batteries. Assuming you are running a solar or wind system already, then it is fairly simple to incorporate the generator. If you are only using a generator, then you might need to buy a set of batteries (+ an inverter if you want 120v power from the batteries) and some wire.
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toyota_mdt_tech
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# Posted: 21 Jul 2019 09:09pm
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Its not wasted as its not producing it, but its available on demand. If you did load it to full max, you would be using lots more fuel and really loading the generator.
An inverter type generator with an idle or eco feature is the ticket. I think everyone in here knows where i am going with this. HONDA is your friend. 
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AffordableDCGenerators
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# Posted: 25 Jul 2019 08:50pm
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You have two basic types, inverter and traditional. A traditional runs at 3600 rpms no matter the load whether it is a small lightbulb or a pump or a stove, etc. From 1 watt right up to the limit of the generator it runs full speed. Now these do have the ability to idle down if no load is present but they are not making usable power. This is a feature more for a jobsite like if it was running an air compressor or saw. Generator idles down until something calls for power.
Inverter generators kind of act like this but they are actually making usable power at all speeds. So if you have a small load the inverter generator runs very slow basically idling until you put more load on it. It matches the engine rpm to what your load demand is. This obviously saves lots of fuel and cuts the noise down.
These are preferred and the Honda seem to be the golden standard in inverter generators.
They do come with a higher price tag and increased complexity. Not much to fail on a plain jane full speed genset compared to the inverter genset but of course everything has pros and cons.
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toyota_mdt_tech
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# Posted: 26 Jul 2019 08:44am
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Wow, great information A/DC Generators. I was sure you were going to hit us with spam. All good info and dead on too.
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AffordableDCGenerators
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# Posted: 26 Jul 2019 08:26pm
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I'm a generator technician by trade, own a Chevy M1031 CUCV generator truck, and make dc generator kits as a hobby. I like generators 
I think in this type of scenario personally, I would run a plain jane generator and use it to power AC loads while charging batteries. That way you utilize the maximum output while its running. Then shut it down and use the batteries for smaller loads.
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Atlincabin
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# Posted: 27 Jul 2019 12:05am
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Just a note of caution - if you are planning to run appliances. I bought a new washing machine and the thing refuses to run properly on my old generator (a Champion, non-inverter). Does fine on the solar system. So some things do not play well with some generators - best to check this out before buying the appliance.
My two cents.
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paulz
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# Posted: 28 Jul 2019 11:04am
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On my non inverter if you push it hard, theoretically it doesn't burn any more fuel since rpm stays constant but I can tell its working hard and must be harder on at least the engine.
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paulz
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# Posted: 16 Sep 2019 06:30pm - Edited by: paulz
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Just bought this old Honda off a pal to use in the carport I'm building 300' from the cabin. Runs great, kinda heavy for 1,400 watts. Probably pretty rugged I'm thinking. 1986 model. Anyone remember these dinosaurs?
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AffordableDCGenerators
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# Posted: 16 Sep 2019 07:45pm
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Nice vintage genny
Any other photos?
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paulz
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# Posted: 16 Sep 2019 09:27pm
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Just realized it has a built in 12v charger, hooked it into my battery bank. I guess they all have that.
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duster
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# Posted: 24 Sep 2019 04:04pm
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I have a 3000 watt Champion generator that I bought new in 2014. It has always run my power tools (drills, grinders etc. without a problem)
Last Saturday though I tried to use my 15 amp Skilsaw with it and it almost immediately burned out the saw.
Anyone know why, and whether buying a lower amp saw could fix the problem? I'm off grid so the generator is the only power source I have.
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AffordableDCGenerators
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# Posted: 24 Sep 2019 07:50pm
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You may just be coming up close to what the generator surge can handle.
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hamish
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# Posted: 26 Sep 2019 08:03pm
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Much better off to use the ac to power a battery charger to charger your batteries. The dc charging output on generators is not very nice to batteries.
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darz5150
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# Posted: 26 Sep 2019 08:47pm
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Quoting: hamish The dc charging output on generators is not very nice to batteries.
I've only used the DC output a couple times to charge batteries.
It will definitely throw some DC volts out and charge a battery.
I have an extra solar charge controller laying around. I was thinking about hooking it up between the Genny/DC output, then to the battery to kind of calm it down a bit.
I can't think of any reason why it wouldn't work. Does anyone else have any thoughts?
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ICC
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# Posted: 26 Sep 2019 09:25pm - Edited by: ICC
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Quoting: hamish The dc charging output on generators is not very nice to batteries.
Not sure what you mean by that. Do you mean because the output is unregulated and can overcharge a battery?
For example, the Honda DC output is clean power, but very limited. 8 amps max on a Honda EU2000i at maybe 14.something volts. The main problem with battery charging off one of those is that the DC output is not regulated like a battery charger. left connected and charging a battery long enough the battery will overcharge.
However, charging a discharged battery back up to something in the 50 to 75% range will not harm the battery unless it is a very small capacity battery. Any normal auto/truck size battery can take the 8 amps easy until the charge level gets closer to full.
Charging at an 8 amp max rate is a waste of gasoline though, even with the generator running on eco mode. If recharging with a generator is to be done often it is much better to buy a good quality, multi stage charger and power that off the AC side of the generator. I have run 24 volt, 55 amp chargers off a Honda EU2000i with no problems. As the battery gets full the charge rate decreases and you know it as the generator slows down (on ECO mode).
Running the DC generator output through a charge controller may not work all that well. When connected to a solar panel or two the CC has a higher voltage than the generator is capable of supplying. It needs that 15 to 18 volts input in order to regulate down to what the battery gets. You probably won't hurt anything other than maybe use up a bunch of gasoline and getting very little charge into the battery.
Even with a generator supplying power to a 120 VAC battery charger the last 15% or so of the recharge is very slow, mostly a waste of gasoline.
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darz5150
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# Posted: 26 Sep 2019 09:58pm
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Quoting: ICC It needs that 15 to 18 volts input in order to regulate down to what the battery gets.
I just went and fired up one of the gennys. No load. 19.2 volts on the DC output.
I agree about the inefficiency about gas for recharge only.
I was just thinking about using the DC output to keep the solar batteries topped off while using the Genny to power the other ac things during a longer power outage.
I have 2 other gennys with DC ports. Maybe this weekend I will check the output.
Thanks for the input ICC.ðŸ‘
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ICC
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# Posted: 26 Sep 2019 10:19pm
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A useful tool would be a clamp meter so you can easily measure output current.'
Clamp meter example At the present $28 that is a very good deal
his one is usable on AC and DC, not all are. You close the clamp jaws around one wire and it can read the amps without having to disconnect and run the power thru the meter directly. Very handy device. ( does NOT work if clamped around two wires ) Also usable as a reg multimeter.
I suspect that as soon as a load is applied to the DC side the voltage will drop a lot.
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darz5150
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# Posted: 26 Sep 2019 11:03pm
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Quoting: ICC I suspect that as soon as a load is applied to the DC side the voltage will drop a lot
I am sure you are right. That's why I said no load. I have the clamp on meters. A snap on, a Sperry, and a fluke meter. But when I just tested it. I did just use the probes.
The reason I brought up the charge controller was because we recently had an outage that lasted about 10 hours. And I looked at the DC outlet and thought why not use it to top off the solar batteries at the same time since I was burning propane anyway.
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ICC
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# Posted: 27 Sep 2019 12:03am - Edited by: ICC
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Makes sense if the gen is running anyways. Interested in hearing how the CC works off that DC feed.
I point to that clamp meter often as it is a good deal, and accurate enough for most folks with their off grid equipment. I have a Fluke as my main meter.
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paulz
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# Posted: 29 Sep 2019 08:43pm
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Quoting: ICC Charging at an 8 amp max rate is a waste of gasoline though, even with the generator running on eco mode
The smallest gas generators I've seen are 900w. I've sometimes wondered why not a smaller unit, gas/diesel/propane, maybe a hobby engine, for smaller loads.
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