Quick charging onboard battery while providing AC power

[ShinyTwinkie]

I'm sure a lot of you have realized that if you connect a generator to your trailer, you get AC power, but you may only end up slow charging your battery (depending on the converter and/or battery charger combo you have).

Today's inverter generators output both AC and DC power. The thought occurred to me to hook the AC ouput to the trailer via the shore power cord, and to hook up the DC output directly to the onboard battery (via the tow vehicle cable for instance, since it has a 12v charging pin).

Questions:
1. Has anyone tried this, and does that work well (can these generators handle outputting AC and DC at the same time if the overall wattage stays below the output capacity of the generator)
2. Are there any electrical reasons not to do this? It should be equivalent to having your tow rig hooked up with engine on (charging) while having AC shore power hooked up. I would hate to see my univolt blow up

Thanks.

[purman]

There is a thread on this and I think it was decided it was a bad idea... Someone will post it, sorry i can't find it......

[overlander63]

The way electricity and chargers work, is the one that puts out the most amperage does almost all the work. So, while it may not hurt anything, it won't help much, if at all.

[ShinyTwinkie]

So it sounds like the best thing is to have a "fast charge" feature that you can turn on that's based on 110VAC input. (toggle between fast and trickle charge for the onboard battery trough the shore power input).

[RoadKingMoe]

If you have a factory single-stage converter and/or you don't discharge the batteries very much, it probably makes no difference (and is hence not worth the trouble to use the generator's DC output). Neither the converter or the generator's DC output provide the voltage level that would cause the batteries to draw as much charge as they can with a higher "bulk" charge voltage.

If you discharge deeper than 80% or so charge, say down to 50-60% charge, the best route is to use a 3-stage converter drawing AC from the generator. The higher bulk mode voltage recharges the deeper discharge much faster. The 3-stage converter also doesn't overcharge the batteries when hooked up to shorepower like the single-stage can because it has a lower voltage "float" mode.

[ShinyTwinkie]

Originally Posted by RoadKingMoe

If you have a factory single-stage converter and/or you don't discharge the batteries very much, it probably makes no difference (and is hence not worth the trouble to use the generator's DC output). Neither the converter or the generator's DC output provide the voltage level that would cause the batteries to draw as much charge as they can with a higher "bulk" charge voltage.

If you discharge deeper than 80% or so charge, say down to 50-60% charge, the best route is to use a 3-stage converter drawing AC from the generator. The higher bulk mode voltage recharges the deeper discharge much faster. The 3-stage converter also doesn't overcharge the batteries when hooked up to shorepower like the single-stage can because it has a lower voltage "float" mode.

Thanks, that's exactly the info I was looking for.

[JimGolden]

RKM,

Would you give an example of a 3-stage converter? Would that be one of the intelipower units?

I've been looking to rewire my 34 footer to 50amp so I can add a second a/c and also run the new electric water heater at the same time as the a/c and microwave. I would certainly want to make sure that the new converter I get would be one that would help to quickly recharge the batteries.

Which one do you recommend?

I'm also debating the two EU2000's (I only have enough money for one right now) vs. waiting and getting the EU3000....I know that one has been kicked around a lot on here

[FreshAir]

Originally Posted by purman

There is a thread on this and I think it was decided it was a bad idea... Someone will post it, sorry i can't find it......

This is the similar thread. http://www.airforums.com/forums/f448...not-45030.html
Neil

[RoadKingMoe]

A 60A IntelliPower with Charge Wizard is the one I use. There's another one since I bought it that's said to be better, but I can't remember the name off-hand. I have two Group 27 Lifelines in the front battery compartments.

If you upgrade to 50 amp service, you'll go from a 3-wire 10AWG cord to a 4-wire 6AWG cord because it's split 240VAC. Need a new breaker box as well. Don't know how to get power up to the bedroom vent. If Airstream didn't run a line up there, I might have to use wiremold on the inside skin.

[JimGolden]

Thanks for the advice Moe! I was leaning toward that one but honestly hadn't delved that deeply into the specs yet.

Yep, I can't see removing the interior skins to run a second a/c. I'll run it under the floor, up a clost, and then two or three feet through a conduit to the new a/c. If I need it. I am in the process of painting the roof white and plan to get a new 15,000btu this spring. If that doesn't cut it, then I get radical