How long to charge batteries on 15 amp circuit?

[menguess]

My batteries are pretty low in my 2011 AS 23ft. International. They are almost new, strong batteries. Rather than go through the hassle of taking them out and bringing them home to charge (it is stored offsite), I would like to tow it to the house and plug it into the 15amp garage outlet, with an adapter, while we get it ready for travel. I won’t be using any appliances or even lights. Can anyone guess how long it might take to get the batteries up to full charge?

[NoResults]

What do you mean by pretty low? Below 12.2? If so you have damaged the batteries.


You should be able to bring your batteries up over nite if they are in good shape.


Dave

[A W Warn]

Depends on the output of your converter and the state of charge of the batteries. I'm guessing overnight should do it.

[tbrowne]

It depends. If the batteries are low because you've had it in storage and you will be plugging the trailer into shore power at you're camp site, then a few hours will probably be enough of a charge to get you where you're going. They can charge fully at the camp ground. If you're boon docking then It could take eight hours or so to fully charge them. Again it depends on the state of charge when you start charging. Buy a multimeter if you don't have one so you can check the voltage at the battery. A 12 volt battery is fully discharged at 12 volts. A fully charged battery should read 12.6 to 12.7 volts when fully charged. You have to disconnect the batteries and let them rest for about 30 minutes after charging to get an accurate voltage reading. Unplug from shore power and use the battery disconnect switch to let the batteries rest before taking a voltage reading. A voltage reading taken immediately after charging will be high and it will drop after the battery rests for a bit. You can buy a reliable multimeter at any big box or auto parts store for around $25.00. It's an essential tool when dealing with batteries and trailer electrical systems.

[wulfraat]

Your airstream has a 45-55 DC amp converter. It will take about 3-4 hours to get them back to 90%, then another 8-12 to top them off to 100%.

[OTRA15]

Originally Posted by menguess

My batteries are pretty low in my 2011 AS 23ft. International.
. . .
[4/24/21 edit -- see note below]
. . .
They are almost new, strong batteries.

Welcome to the forum.

Per earlier comments, if you allowed standard wet cell lead acid batteries to go below a 12.2 volt state of charge, they are no longer "new, strong batteries." If the voltage went below 12 volts, you might as well buy new ones, especially with your stated goal of being "ready for travel" IMO. [Wait an hour after shore power is removed to get an accurate voltage reading on your AS monitor.]

FYI a good "Battery School" source for general reading on RV batteries:

http://www.batteriesnorthwest.com/ba...hool.cfm?TID=0

Good luck.

[menguess]

We just picked up the Airstream from a repair shop that was fixing the fresh water tank leak. Apparently they kept the lights on, etc. because when we picked it up, I could tell the jack was running slower. I didn’t have my multimeter with me, but I don’t believe the battery is damaged.

[menguess]

Thanks for all your wonderful help. Knowing that it can be charged overnight rather than days is what I needed to hear. We can do that. We will be boondocking the first 2 nights then connected 30amp shore power. Thanks again.

[OTRA15]

How will you boondock for 2 nights if your batteries have already been silently destroyed by improper usage? [especially in Colorado with nights still very cold]

They may seem fine, but please read all the posts, and consider the worst-case-scenario for what the shop might have done, before you rely on batteries in an unknown state.

Yes, you might charge them overnight and "think" that a good voltage reading in the morning solves things, but battery strength is more complicated than that IMO. The "charge overnight" advice assumed that you have strong healthy batteries.

Good luck.

[uncle_bob]

Hi

Best approach:

Plug them in at noon and come back the next day at noon. That way you can be pretty darn sure they are charged. Before you do any charging, check the water level in each of the cells.

The only way to know if the batteries are any good is to check them. Without a test of some sort, you are flying blind. Without a shunt based meter, even testing them is going to be a bit of a challenge.

Test approach 1:

Come up with a family large load ( like a 10A load). Put it on the batteries and monitor the voltage at the battery posts with your multimeter. When they get to 12V, pull the load and let the cells rest. Check the voltage again. If it's above 12V, put the load back on for a bit and repeat "pull off / rest / check" process.

Test approach 2:

Come up with something like a 1A load and don't worry about the "pull it off" stuff.

If your batteries are good, they should make it through 8 to 10 hours of test 1. I'd check the voltage every 15 minutes or so on test 1. On test 2, they should run for 80 to 100 hours. You probably are ok only checking every hour or two on test 2.

If both of those sound like a PIA, yup, you got that right.

Bob

[menguess]

Thanks for all the advice, and we will certainly use it. My husband is definitely a “worse case scenario” kind of guy, so he’ll check everything out. Uncle Bob, you’re a gem, and so are the rest of you! We store the batteries in our home over the winter and periodically check on them and we fully charged them before putting them back and taking the AS to a couple repair places for maintenance and repairs. All seemed fine till the last place which had it for 6 or 7 days and ran them down somehow. When we go back to the AS today, we’ll take the multimeter and evaluate what to do next. Thanks again!

[Bill M.]

My advise is to charge them and then go camping. Monitor the voltage as you use them. If they are good, good. If they are bad you can replace them when you are almost anywhere. This is probably as good a test as you can devise anyway. And you probably already have a feel for how they should perform.

[tjdonahoe]

1 1/2 days your good to go...

[brick1]

Have the batteries load tested..