generator battery charging

elesaver · December 2014

In looking at a few generators online, I see only a 12V battery charger option. Certainly this would not work for a 24V battery bank so there has to be something more about these. Would someone explain how to charge battery banks larger than 12V with an external charger? Thank you.

Cariboocoot · December 2014

Re: generator battery charging

Get a 24 or 48 Volt charger:

http://www.solar-electric.com/batteries-meters-accessories/bach2/bach1.html

Quite often when you go up to a 24 or 48 Volt system you buy an inverter with the charger built in. They tend to work better than stand-alone chargers too.

elesaver · December 2014

Re: generator battery charging

OK. I have to back up. If there is no grid power due to outage, etc., and if you have solar panels/cc/battery bank/inverter, etc., how do you charge the batteries with a generator during times of little or no sun? The generators I have seen are showing 12V charging. It seems in the signature lines of posters on this board, many have generators so how are they used to keep batteries up? I hope this explains my confusion in the process of using a generator. OR, is the generator used to provide power to the inverter instead of the inverter drawing from the batteries during times of no/little sun?

Cariboocoot · December 2014

Re: generator battery charging

I don't know what generators you've been looking at but most of them put out 120 VAC power the same as any outlet. Some also have 12 VDC output, but it is low current and useless for charging.

One of the most popular, the Honda EU2000i: http://powerequipment.honda.com/generators/models/eu2000i

Note output of 120 VAC @ 13.3 Amps (1600 Watts) and 12 VDC @ 8 Amps (96 Watts).

elesaver · December 2014

Re: generator battery charging

So, then, the generator is used to power a battery charger which is to the voltage range of the bank, eh? OK. I see how that would/could work. But back to the concept, if I may. An Outback VFX has ac in for a generator, I presume? (Presumptions have killed me so far so why not one more? :-) ) So, you would wire the generator into the inverter and re-charge the batteries in that way? I know I have read that you have to remove the ground within the generators in order for them to work with the inverters somewhere. Apparently, the inverter converts the VAC to VDC somehow? This is getting more fascinating as I go. :-) I would feign ignorance but some things are too obvious.

Cariboocoot · December 2014

Re: generator battery charging

elesaver wrote: »

So, then, the generator is used to power a battery charger which is to the voltage range of the bank, eh? OK. I see how that would/could work. But back to the concept, if I may. An Outback VFX has ac in for a generator, I presume? (Presumptions have killed me so far so why not one more? :-) ) So, you would wire the generator into the inverter and re-charge the batteries in that way? I know I have read that you have to remove the ground within the generators in order for them to work with the inverters somewhere. Apparently, the inverter converts the VAC to VDC somehow? This is getting more fascinating as I go. :-) I would feign ignorance but some things are too obvious.

An inverter-charger such as the VFX does both jobs: when there is AC present on AC IN it switches to charging the batteries and the loads on AC OUT are run directly from the generator. The built-in charger is basically the inverter running in reverse.

Most generators do not have an N-G bond in them to remove as they are considered "portable devices" and as such have floating neutrals. You juts hook hot to hot, neutral to neutral, and ground to ground. It works.

elesaver · December 2014

Re: generator battery charging

Now I see the picture. It's wonderful thing.

oil pan 4 · December 2014

Re: generator battery charging

Go on ebay and search " ___ volt battery charger".
Chances are what ever voltage you could ever want there is a charger for you.

icarus · December 2014

Re: generator battery charging

Pay attention to qualtiy of charge, and charger, including efficiency, Power Factor, battery temp monitor etc. An typical automotive type charger is a bad idea for PV batteries. In short, to some great extent, you gt wht you pay for. For a stand alone, consider a Xantrex or Iota. Look at NAWS home site for mor info.

Tony

BoFuller · December 2014

Re: generator battery charging

I have a question on WHEN to charge with the generator. During December and January, when the sun is low and the days are short, I don't get a full charge. I have been running the genny for about an hour in the morning 8:00 am to 9:00 am to give the system a boost, then the solar panels finish it. When I left for a week, my friend, who stayed there, said it was better to run the genny about 6:00 pm, after dark. I told him I thought that was messing up the cycles, but he swears it's better. Any advice?

westbranch · December 2014

Re: generator battery charging

Did he run the gen and shut everything off when the gen shut down?
If so the battery would be reasonably well charged, maybe not 100% but OK, and if he did not use the power till the afternoon.... might be better . the way to know is record the numbers..

hth

mike95490 · December 2014

Re: generator battery charging

I would say YOU are right, and your friend is wrong. I do the same as you - so it's got to be right !!

But if you care about conserving fuel, and generator hours, run the generator in the am, and bulk the batteries up. When the charge rate starts to taper off, is when I shut down the genset. Any sun in the rest of the day, will complete absorb and then go to float.

Conversely, if sun arrives mid day, and the batteries are low, they may not get through the full bulk cycle or absorb, so the evening generator run will be less efficient, as you are burning fuel and only getting a partial charge rate.

BB. · December 2014

Re: generator battery charging

Generators are generally most efficient with 50% or more of rated load. Inverter generators can get down towards 25% of rated load and still be fairly fuel efficient (diesels are more efficient overall).

Lead acid batteries are most efficient when charging at less than ~80% state of charge, and least efficient when charging at 90% or higher (equalization is near zero percent efficient).

Running the genset early in the morning (before the sun hits the array fully), can be very fuel efficient (heavy charging low, batteries at less than 80% full).

Evening charging can be relatively efficient if the generator is supporting AC loads (cooking, lights, water pump, computer+TV+etc.) and/or a decent rate of charge (i.e., 50% or more of rated output). This is becoming common in regions that have "hybrid" generator+battery system--The house/small village runs from batteries during off peak hours and runs the generator to recharge and supply peak power (typically evening).

If the battery bank is near fully charged when the sun comes up the next day--They you are simply substituting fuel for "free" solar power... Something that is not great idea.

As long as you can run the genset in the morning (when needed), it seems like a good idea... And only run in the evening if battery power is seriously depleted (towards 50% state of charge) and/or bad weather is expected (low amount of solar power is expected).

-Bill

oil pan 4 · December 2014

Re: generator battery charging

Running a generator at no load compared to between 1/4 and 1/3 load makes little difference in fuel consumption.
So load them up.

generator battery charging

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