House Battery Discharge Question

[Sonic]

Originally Posted by CA puttin

Guys thanks for the informative threads. I have a similar problem with my 2011 Itasca 40 u. I have a residential refrigerator and a bank of 6 house (interstate,wet). My storage unit turns on the 110v power for 3 hours per night. On my 2nd set of batteries in less than 3 years. I do the main and also have a watering system on the batteries and check it every other month. Picked up my RV and put it on my 50 home plug for 2 days. Went out boondocking last weekend and with only the refrigerator running, I couldn’t get more than 5 hours before having to start the generator. I’d run the gen until 10 pm and by 7 am, it was down to 11.7, which I know is critical levels. I’ve researched about 20 hours of information and still have questions. First, I’ve asked numerous mechanics and Winnebago...when in storage, and on 110v, do I leave the battery switch off button engaged? Could this be my problem? I ran the generator so long that it actually dropped rpm (2x) and lost Electric power. I’m now concerned that it may also be a problem. Open to any ideas, thoughts. Thanks.

Have you run an equalization cycle?
What is the voltage of each battery when you consider the batteries fully charged?
Have you tested the specific gravity of each cell to see if you have any inconsistencies or bad cells?

[Dutch Star Don]

I think a pretty simple test is to turn the heater off, turn something like a TV on and see how fast they drain. Running an electric heater isn't much different than trying to run the roof A/C off the inverter.....too much of a load.

[CA puttin]

Thanks, and no I have not. Since these batteries are less than a year old, wasn’t sure if it was needed. I had scheduled an appointment with interstate batteries, but postponed the visit with considering current situation.

I was planning to focus on the magnum inverter tomorrow, but will also take a look at the batteries. Thanks...electrical is always an opportunity for me.

[CA puttin]

Yes, relative to the length of drain I am working to get them fully charged before testing. I’ve had them on 50 amp for 4 days and currently ay 13.3. As for an appliance, I’ve got the residential refrigerator.

[Sonic]

Originally Posted by CA puttin

Yes, relative to the length of drain I am working to get them fully charged before testing. I’ve had them on 50 amp for 4 days and currently ay 13.3. As for an appliance, I’ve got the residential refrigerator.

Just a note: the voltage can look ok, but that doesn’t necessarily mean the batteries are fully efficiently charged. An absorb time of 3-4 hours and a full equalization cycle to remove any sulfation will get you there. Test the specific gravity of each cell after those steps to ensure they are all equal or very close.
Then after letting the batteries rest for 12 hours you can do a proper rundown test as I detailed in an earlier post so you can see exactly where the batteries stand.

[creativepart]

I don't think you can trust your battery monitor... or even a multimeter.

Charging the batteries (via shore power, generator or driving) will seem to charge you all the way back up because you see 13+ volts in your meter. But turn off all charging and all draws and wait and hour and then take another look. I"d guess your voltage will be down near 12.3v or so. They are not dropping they just never really charged up regardless of what your meter said.

It can take a very long time to get those (now damaged) house batteries back up to a full charge. IF, and that's not really a sure thing, they can be charged all the way back up.

Turn off the heater - the nighttime temps may drop to 32 degrees but the mass of your RV will not have time to reach anywhere near a freezing temp before the daytime above freezing temps are back. You don't need the heater now. 48 or more hours of constantly below freezing... you need to take precautions. Overnight followed by above freezing you are good to go without precautions.

The next steps would be to check the specific gravity of each and every cell on the batteries to see if any are bad - make that, to see how many are still good.

Finally, install a shunt-based battery monitor so you can see your state of charge in percentages and track all power going into and out of your batteries - regardless of any charging or usage at the time of your readings.

[SGTrvlr]

What do you mean by "batteries at rest"?
Thanks

[creativepart]

Batteries that have not had any charge applied to them or any draw from them are resting batteries. For instance, when you plug into shore power and check the voltage of your battery bank you'll see something like 13.7v. You can unplug from shore power so no charge is being applied and you can still see 13+ volts showing on you battery bank. It looks like they are fully charged up.

But if you wait 20 mins, don't apply any charge or any draw then you'll see their true state of charge in volts. It's not that they have dropped or are not holding the charge, you were never seeing their state of charge just the surface charge voltage from charging.

This is why volt meters are so difficult to use to know your batteries real state of charge.

A similar thing happens when you draw power from them. The voltage drops and unless you wait for a period of time after you've stopped drawing from them you will see this lower voltage before it settles back to the actual voltage of the bank.

That's batteries at rest.

Most don't realize that it can take a very very long time to charge up your battery bank. So, if you are basing your state of charge on batteries that are not fully resting you will see an erroneous voltage reading and not even realize it.

A shunt-based battery monitor shows state of charge in percentages and it doesn't matter if you are actively charging them or drawing from them. The shunt tracks every amp going in and coming out.

In reality, the voltage meter in your RV is practically useless. And even when it is working correctly, the difference between fully charged and 50% discharged is only 0.5 volts. And it's only 0.8 volts between fully charged and fully discharged.

https://www.rvtechlibrary.com/battery/bat_volts.php

[CA puttin]

First, I want to apologize...I didn’t man to hijack this thread, but having a lot of similar problems. I just opened the link and printed all of the info from RV tech library. These test are pretty easy with 2 or 3 batteries, I have 6 that are located in the center of the coach below the slide out tray in the basement. I may have to pull all of them out and take them down to Interstate batteries for the proper testing. I have been a little reluctant to head into the high density areas with all of bad stuff happening. After reading your responses, I realize that I have using the volt meters that are built into the coach. I may be using totally , or at least partially incorrect data.
I am also assuming that to preform these test, that the batteries must be disconnected from the chain and measured individually. Appreciating all the feedback and ideas, thanks.

[Sonic]

Originally Posted by CA puttin

First, I want to apologize...I didn’t man to hijack this thread, but having a lot of similar problems. I just opened the link and printed all of the info from RV tech library. These test are pretty easy with 2 or 3 batteries, I have 6 that are located in the center of the coach below the slide out tray in the basement. I may have to pull all of them out and take them down to Interstate batteries for the proper testing. I have been a little reluctant to head into the high density areas with all of bad stuff happening. After reading your responses, I realize that I have using the volt meters that are built into the coach. I may be using totally , or at least partially incorrect data.
I am also assuming that to preform these test, that the batteries must be disconnected from the chain and measured individually. Appreciating all the feedback and ideas, thanks.

They don’t need to be disconnected. Just get a $12 hydrometer and test the specific gravity of each cell after letting the batteries rest for 12 hours. If all checks out, do the rundown test I posted above and you’ll know where they stand.
There’s a lot of noise around batteries, but it’s all pretty straightforward stuff.

[CA puttin]

Thanks for the info on keeping batteries connected, that will make this experience a lot simpler. Thanks to our stay at home, I’ve got the time. Been rereading all of my manuals and also planning to do the equalizer.