Battery's drained after one night

[maggie blair]

I have a 32 foot class C with two house batteries under the step. I had them tested and the liquid inside was all right and they tested at over 13.10. When I try to park overnight without starting the engine the batteries are down to 50% by morning. My generator will not start unless I start the engine and run it for a while. Could anyone help me with these problems? Thanks so much in advance.

[SWharton]

I assume you are boondocking. You must have a phantom battery drain someplace. Try disconnecting the battery for overnight and see what happens. If batteries are OK you have a big time drain, if not, probably the batteries are gone.

 

How old are the batteries?

[Chief 62]

Did you have the batteries load tested when they had a full charge? I am willing to bet you have at least one and maybe two bad batteries. How old are they? Usually you can get about 3 years out of a set of house batteries. Other thing to consider is how much power drain you are having from running lights, tv, etc. Once you get the battery situation taken care of you should switch all your interior lighting over to LED. Much less power usage. Let us know what you find out.

[Biker56]

I have never seen my house batteries at 13.1V unless they were being charged via engine, generator or shore power. Fully charged battery is 12.73V

 

For best accuracy when measuring battery voltage, the battery must be in ‘open circuit’ condition (at rest). This means that the battery must NOT be under load and it must NOT be charging. To be somewhat accurate, the battery should be in that condition for an hour or two before taking a measurement, while for a more accurate measurement you should wait 6 hours up to 24 hours.

[Devilishjim]

Are you running the furnace during the night ? The blower will suck the battery down fast.

[dartmouth01]

Most likely something draining your battery. How much are you using the battery overnight? heater, tank heaters, etc? Is there a light on somewhere in the basement?

 

Alot of RVers use a Trimetric battery usage meter to see exactly how much power is being used at that exact time. This helpful in giving you an idea immediately if there is something running. Bogart, the manufacturer is well trusted and the Trimetric is feature packed, though you can get something cheaper on Amazon that will give you the basics, like this:

 

https://www.amazon.com/Voltmeter-Ammeter-Digital-Voltage-Measurement/dp/B00V7YUNFA/ref=sr_1_1?ie=UTF8&qid=1488200972&sr=8-1&keywords=amp+meter+shunt

 

Another test I would do, after the batteries are fully charged, is a specific gravity test of each cell using a hydrometer. Bit more involved and pain in the ass, but it will give you a very good indication to the health of the batteries.

[Kirk W]

The chart above lists both voltages and specific gravity for flooded cell batteries at various states of charge. If the person who tested your batteries got 13.1V that tells me that either the batteries were in the circuit, they were tested soon after you stopped driving(thus having been under charge as you drove there), you had just been connected to shore power (they are under charge then too), or did something else that was not proper. To get accurate information when a battery is tested, it should be fully charged and then the battery connections lifted and the battery allowed to sit in open circuit condition for a minimum of 1 hour and 2 hours is preferred. I had them tested and the liquid inside was all right and they tested at over 13.10.

I had them tested and the liquid inside was all right and they tested at over 13.10.

By saying that the liquid inside was "all right" am I correct to assume that the person just looked inside of the top of each battery and checked the liquid level? That is important to check but his voltage readings are pretty near useless if he didn't do the entire job. I have found that if he did as I suspect and you had just been driving, a much more common voltage reading for a good battery is more like 13.5V or above. In order to fully charge the batteries in your system, the alternator/voltage regulator will apply about 14V to top off the batteries as they reach full charge and once that is removed, you should see well above the 13.1V that your person saw, which is the reason for allowing the battery to sit, in open circuit condition for 2 hours. I'll not go into the reason that is needed, although our resident engineers love to get into those discussions. For a lay person, all you need know is to lift the negative battery cable and let the battery sit for at least and hour before you check voltages. Doing specific gravities is far more accurate for many reasons, and that allows you to check each cell to make sure that all of them are good, or at pretty much the same condition.

 

Here is a very good article on how to care for your batteries.

[Al F]

For a quick and simple test.

 

-- Start with the batteries charged. Be sure they are fully charged by being connected to shore power for a day or so.

 

-- Disconnect from shore power.

 

-- Put the meter on the batteries.

 

-- Make sure everything in the RV is turned off. Lights, furnace, etc. You can leave the fridge on. If you have an inverter, be sure it is off.

 

-- Come back in an hour. Using the chart Kirk supplied above, the voltage should show the batteries at about 100%. If not you may have a phantom load or a weak or bad battery.

 

-- If the batteries show close to 100% then do the following

 

-- Assuming you have not replaced the light bulbs in the RV with LED bulbs, turn on enough light fixtures to power 10 light bulbs. Some light fixtures have 2 bulbs. This will put a load on the battery of around 15-20 amps.

 

-- Leave the lights on for an hour then turn them all off and check the voltage with the meter you attached earlier. Use the chart Kirk supplied above. If the voltage shows the batteries are much below 90% then you probably have weak or bad batteries and you need to do additional testing with a hydrometer. That is more technical than I want to get into here.

 

BTW, you can buy the volt meter for testing at Walmart, or Amazon, for under $20 and do this testing yourself.

[Yarome]

All good general ideas, but without knowing the type and size (capacity) of your battery bank it's very difficult to give you any type of informed help.

[Daveh]

Off topic but Yarome you either just added a new tagline or I just read it for the first time. Either way: Ha!

[NoDirectionHome]

So you seem to think your batteries are OK. 1st thing I would do is measure the voltage at the generator's starter. Could be just a corroded or loose cable.

[Yarome]

Off topic but Yarome you either just added a new tagline or I just read it for the first time. Either way: Ha!

 

Changed it awhile back, but yeah... some times the truth hurts.. don't it! Literally!