How long to recharge RV battery while driving?

Generally, charging via the umbilical cord will take forever. You're looking at maybe 10amps through that little wire.

What sort of an RV are you talking about? What size battery bank? Obviously a larger battery bank will require longer to recharge, all other things being equal.

For a trailer relying on the power feed from the 7 pin connector, it may take a very long time indeed, and partly depends on how beefy the wiring is on the tow vehicle to the seven pin connector. Likewise, you have to consider how large or small the continuing loads are that must be simultaneously powered (fridge, LP detector, any lights or fans that are on, the furnace if you leave it on to keep things from freezing, ....)

For a motorhome with good wiring between the isolator and the house battery, it is a good bit faster, possibly on the order of a few hours to mostly recharge the battery. The quality of this wiring and setup can vary.

The best way to find out is to actually measure the charging current and voltage you're seeing at the house battery under the stated conditions, and get actual data for your rig. Otherwise you're pretty well in the "how long is a rope" sorts of questions and answers.

I have had that same question. I tested mine after I got back from a trip.

My 2 6-volt T-105's (225ah) were down to about 50 percent when we started driving down the road. I used my hand-held volt meter to test that percentage. I tested the rested batteries the next morning after a 10 hour drive. My volt meter tested them at 90 percent. Nothing but the parasitic draws while driving down the road. No fridge or TV. :)

Not scientific by any means but it satisfied my curiosity.

8-12 hours generally speaking

'Charge' line for tow vehicle is LONG and UNDER sized.
Best for maintaining a trailer battery vs charging one

Generally speaking......

korbe wrote:
I have had that same question. I tested mine after I got back from a trip.

My 2 6-volt T-105's (225ah) were down to about 50 percent when we started driving down the road. I used my hand-held volt meter to test that percentage. I tested the rested batteries the next morning after a 10 hour drive. My volt meter tested them at 90 percent. Nothing but the parasitic draws while driving down the road. No fridge or TV. :)

Not scientific by any means but it satisfied my curiosity.

A voltmeter can not determine the state of charge of a battery. Only a load tester can do that. You were probably well below the 50 and 90 percent that you stated.

sgrizzle wrote:
If you are camping without shore power and you basically drain your battery...how much driving (hours) would you need to go to recharge them for the next stay?

Generally speaking, just rough guestimates....thanks!

Assuming you have a Tow Vehicle, then it can supply about 10amps while driving. So if a 200AH battery is totally dead, you'll need to drive about 20 hours. Of course there are lots of variables to consider such as age and condition of the battery and the actual current delivery.

JWRoberts wrote:

korbe wrote:
I have had that same question. I tested mine after I got back from a trip.

My 2 6-volt T-105's (225ah) were down to about 50 percent when we started driving down the road. I used my hand-held volt meter to test that percentage. I tested the rested batteries the next morning after a 10 hour drive. My volt meter tested them at 90 percent. Nothing but the parasitic draws while driving down the road. No fridge or TV. :)

Not scientific by any means but it satisfied my curiosity.

A voltmeter can not determine the state of charge of a battery. Only a load tester can do that. You were probably well below the 50 and 90 percent that you stated.

Well, I have been using my volt meter and measuring the readings in volts for a lot of years. Doesn't the volt reading measure state of charge? I must be missing something.

korbe wrote:
Well, I have been using my volt meter and measuring the readings in volts for a lot of years. Doesn't the volt reading measure state of charge? I must be missing something.

It's good enough for me.. as long as that voltage stays there when the charger is removed.

I use a volt meter but agree that it takes an extremely long time to recharge. I'm in a class C and have beefed up the charging path, as well as doubling it.

Part of the problem is the engine controllers (ecu) "sees" the starter battery and reduces charging based on the voltage of it. There are ways around this but they require lots of effort as well as modifying the OEM alternator.

I've gone solar instead.

2oldman wrote:

korbe wrote:
Well, I have been using my volt meter and measuring the readings in volts for a lot of years. Doesn't the volt reading measure state of charge? I must be missing something.

It's good enough for me.. as long as that voltage stays there when the charger is removed.

You can read about SOC hereSmart Gauge and hereBattery FAQ. Bottom line, most of us use voltage readings after the battery has rested 4 to 6 hours under NO LOAD conditions. It is a ball park reading.S.G. readings that are temperature corrected under the same NO LOAD conditions will get you into the infield of the ball park.
Another link on SOCBattery University