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!

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

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.

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.

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.

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

24 Replies

coolmom42
Explorer II
Oct 22, 2014
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
Nomad III
Oct 22, 2014
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
Explorer
Oct 22, 2014
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
Moderator
Oct 22, 2014
Moved from Technology Corner

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

24 Replies

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