charging battery from generator---how long does it take?

[coolmom42]

In 2-3 years, I'm planning to convert a van to a minimalist RV, and estimate that I'll need about 100 amp-hours of power every couple of days, absolute max. (LED lighting, fan, water pump, charging electronics, maybe at some point a 12 V fridge.) So that means a 200 amp-hour battery bank at 50% or less discharge level.

I recently purchased a Honda EU1000 generator, with the intent of running home fridge/freezer in a power outage, plus the long-term intent of using it to charge a future camper battery.

My understanding is that this will require a good quality battery charger between the generator & battery bank.

Battery chargers come in different amp ratings, so how do I choose the most useful amp rating for my needs?

Is the amp rating calculated at 12 V DC output?

With the generator running at say 800 watts/12 V = 67 amps x 90% charger efficiency that gives 60 amps possibly going to a battery bank. Correct me if that's wrong, please.

So given the 60 amps possible from the generator, does the charger then become the limiting factor?

With a 20 amp charger.... does that mean it would take 5 hours to restore 100 amp-hours to the battery bank?

Just trying to figure this out. My plan is to gradually acquire smaller components and then pull the trigger on the van in 2-3 years, depending on lots of factors.

Any input appreciated!

[coolmom42]

pianotuna wrote:
Hi Coolmom,

The recharging of lead acid batteries is not linear. As the the battery reaches 90% charging rate drops off dramatically.

Boost is 14.4 volts, normal is 13.6 and storage is 13.2.



I would recommend looking at solar panels when the time comes to design the rv.

OK this makes sense. Now I remember seeing this curve but didn't really comprehend it until now.

[SteveAE]

coolmom42,

I have nothing of substance to contribute to this thread, but I do want to congratulate you on how well you have researched your upcoming project and verbalized your questions. Good job.

Steve

[mena661]

45A charger on the Honda 1000W generators is about the max it will do.

[MEXICOWANDERER]

A question is, with one thousand watt limit what are the options in a power factor corrected charger dept? Trying to recharge 100 amp hours at 30 amps is dooming the user to listen to the generator for four hours at a stretch to charge to 75-80% with regular batteries and perhaps 80-85% with AGM. I would be -mighty- tempted to fit a 140 amp alternator to that van and let it whack the AGM's for a half hour while concurrently running the Honda. But there is a finite amount of amps that a Honda 1000 will ignite and if memory serves me correctly that figure is 50 amperes or less

[darsben]

60 amp will be fine on your genny 60x120 = 720 watts your genny is probably 800 - 900 watt continous.

[pianotuna]

Hi Coolmom,

AGM are faster to charge and can accept current faster, but recharging any lead acid chemistry to 100% will still require MANY hours of generator run time. The trade off comes with lower total capacity. A group 27 is probably not going to be 100 amp-hours.

Mostly folks settle for 50% to 90%. If that takes say 3 hours, then getting from 90% to 97% will take an additional 3 hours. Probably 97% to 100% takes yet another 3 hours.

[coolmom42]

My plan is to start out with all 12 V inside, and just use a small portable car-style inverter for charging electronics. A lot of that will be done while driving, anyway.

What my question boils down to is this: How does one determine the size charger to get?

Solar is not in the plan; the expense does not seem justifiable, given that I already own a quiet generator. A lot of my travels will be in the Southeast US, with frequent cloud cover and shady sites preferred. Solar doesn't seem like much bang for the buck under those circumstances.

I'll probably go with 2 x group 27 AGM batteries, to get the 200 amp-hour bank. No maintenance and no need to vent.

[pianotuna]

Hi Coolmom,

The recharging of lead acid batteries is not linear. As the the battery reaches 90% charging rate drops off dramatically.

Boost is 14.4 volts, normal is 13.6 and storage is 13.2.



I would recommend looking at solar panels when the time comes to design the rv.

[PapPappy]

The general consensus is that you will do better with an actual battery charger, as compared to a battery charging Inverter/converter. You will want one of those for the conversion too, but for charging batteries, get a good quality charger. You really don't want to get to large a charger, and much above 30A will be more than you need for a 3-4 battery bank.
You may want to check into solar charging too. A couple of panels on the roof, or even these newer portable packs that you lay out when you get to a CG will do a nice job of getting the batteries back up to full charge. (I'm not talking about one of those little laptop size panels, which are really just for battery maintenance/trickle charge).

Depending on what you plan to do with the RV, you may find that installing a slightly larger Alternator on the Engine, which is wired up to your "house" batteries too, will charge those batteries when you are on the road....but it is not a very efficient method for charging when you are camping.

You will probably find several other threads about batteries, and they should be helpful.

Oh, on edit, and reading the original question...how long does it take to charge the battery? It will depend on the battery, and how discharged it is. It will also depend on the age and condition of the batteries, as well as the charger...so it could take a few hours, or it could take all day.

Good luck

[1492]

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