Is it time for new batteries?

[Spotman]

I have had two (2) Interstate deep cycle RV batteries in my teardrop for about 4-5 years now. I haven't really used them for the purposes ie; ceiling fan, several Led lights or usb/cig plugs. Most of the time always running off campground power. This Teardrop is always plugged in and garaged so the only time off power is traveling. I just recently installed a 100 watt solar panel and Renogy hook ups. Problem when testing outside in direct sunlight, just having fan on draws battery down within minutes! I have attached several pictures that were taken today in a 10 minute period. I need some expert experience advice. The pictures are in the steps on the Renogy control. The first picture is when plugged in.

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[Spotman]

Oh yeah, this is my Teardrop.

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[John61CT]

Yes, the only way you get more than that from consumer grade batteries is meticulous care, which takes better gear as well as the knowledge.

Without those factors, even spending 5x more on top industrial deep cycling units is wasted

but put the two together, and you might get a dozen years.

All this assuming EoL replacement at 70-75% SoH.

Short answer yes, plan on replacing a House bank every 3-5 years, depending...

[Tom&Shelly]

Looks like you are going from 13.5 volts down to 12.8 volts in "minutes" once you switch on a load? That sounds normal to me. 12.8 volts is a good operating voltage for lead acid batteries.

How long does it stay at 12.8 volts? Your batteries may still be perfectly healthy.

Tom

[Spotman]

Tom, tomorrow I will test it a little longer and plug in the 12 volt fridge and see if I can stay at a good level. Temps are down in the 40's right now.



Bob

[tony.latham]

Problem when testing outside in direct sunlight, just having fan on draws battery down within minutes!

The only way to use voltage as a measure of battery health is to give it 45 minutes or so at rest with zero consumption. It's called resting voltage.



I suspect you're okay.

Tony

[Spotman]

Do you mean once you unplug from shore power wait about 45 minutes? Then check voltage and power up some things.

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[MtnDon]

Disconnect the loads and the charging system. See what the volt is after an hour or so. Using a voltage reading shortly after discontinuing a charge or shortly after turning off a load can give false values. Too high or too low.

You don't say if the batteries you have are sealed or flooded types. If they have removable caps a hydrometer, with the proper electrolyte temperature correction applied is the absolute best method to determine the battery state of charge.

[edgeau]

I have a similar Renogy charge controller. I can see you have it set for a sealed lead acid. I find the battery % is misleading while there is any charge or load current. As has already been mentioned leave it rest for a bit to get a reasonable reading.

Also I saw you were not getting much from the solar for full sun only .2 of an amp. Depending on the wattage of you panel you should be getting much more, eg my 200 watt will translate to 8 or 9 Amps on the controller in full sun. I even get 2 on heavy overcast days.



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[Spotman]

My batteries.

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[John61CT]

Those are for Starter use only.

When you replace, go *or true deep cycling, 99% of the auto/ consumer market is fraudulently labeled.

Specify between GEL, AGM (sealed) or FLA which type you want. FLA best value - Ah per year - by far.

[RJ Howell]

I do agree with the advise being given. Disconnect from source (s) and let it rest. I was taught that resting less than 12hrs is inconclusive results. Yet, if you do check in an hour and you dropped 12.8v to 11.8v, you know you have an issue. If you only drop 12.8v to 12.79v in that hour, inconclusive result.

With this in mind, plan to let it rest overnight before testing with a draw.

Maybe you stated it and I just missed it, but, what is the AH of the battery? I see it's a Group 27 so that could be anywhere from 50-100ah (C20 value).

[mtbikernate]

When my AGM battery died, the voltage went absolutely nuts. It spiked and plummeted and back again within seconds. Damaged the control board on my MaxxFan in the process. I still wonder if my overhead light needs to be replaced because it occasionally behaves oddly ever since then.

I went LiFePO4 when I replaced the battery. I ran some numbers and found that it was at least as cost effective as AGM (11yr warranty on the LiFePO4 vs. 3yr actual lifespan on the AGM), and with more useable capacity per unit weight.

[Tom&Shelly]

Tom, tomorrow I will test it a little longer and plug in the 12 volt fridge and see if I can stay at a good level. Temps are down in the 40's right now.



Bob

Hi Bob,

I suggest going ahead with what Tony and Don suggest. They know what they are talking about (Don has an off-grid cabin and uses batteries). Particularly, check the fluid levels in the cells and PH with a hygrometer.

after that, what you are suggesting--running the 12 volt fridge while monitoring the voltage from the battery--seems sound to me. After all, that's how you plan to use the battery. If the voltage doesn't drop down past 12 volts fairly quickly, I'd call it good.

Tom

[Spotman]

Thanks for all the great advice. Been running Alpicool fridge couple of hours now at 12.8+. I'll see how it goes when sun decreases.

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