Voltage question

[sabasarge]

I run my teardrop on two Trojan 6v batteries and they’ve been great over the years for me. I keep them charged with a 100w solar panel during the day, and my question is this....on their own without solar help they stay at 12.7-12.8 consistently UNTIL the 12v fridge cycles and then it drops to 12.2-12.3 until the cycling is done and then it jumps back to the 12.7 or 12.8.
Should I be worried about it getting so low during the fridge recycling?
Much obliged for the help, and also for all the great tips I’ve gleaned from this forum over time.

[Socal Tom]

No, that is normal. It might be improved with larger wires, or if the voltage meter is directly attached to the battery and not on a wire shared with the fridge.

[sabasarge]

Thanks Tom. As 12.2 is basically a dead battery, hence my concern, even though it jumps back afterwards.

[Socal Tom]

Thanks Tom. As 12.2 is basically a dead battery, hence my concern, even though it jumps back afterwards.

There are 2 things pulling it down 1 is that the voltmeter is measuring the voltage in the wire, not the battery, so with the big draw it won't give an accurate result without a really big wire. The other is that the battery has to perform a chemical reaction to create the electricity. That will take a minute to catch up.

-edit, also most charts indicate that 12.2 volts is 50% of capacity for a lead acid battery.

[John61CT]

First off, use proper quality deep cycling batteries.

Next, size the bank to the power needed, IMO for a fridge 100Ah would be small, 200Ah plus better.

Under load, it is normal for voltage to sag.

Thus voltage while in use does not accurately show SoC%, get a coulomb counting meter

and ensure you do not deplete much below 50% except for emergencies.

At rest, isolated from loads and sources, 11V is harmfully low.

12V is less damaging to longevity.

[saltydawg]

You need to do a load test on the batteries, dropping that far even with it going back up does not sound good. Is it hooked to solar when doing this? if so they maybe weak and the solar is just hiding it.

Do you have a power meter on the batteries, and I dont mean a volt meter? You really should get one, it will tell you a lot.
https://www.amazon.com/AiLi-Battery-Mon ... 521&sr=8-5

[sabasarge]

Thanks guys, I really appreciate the responses. It is not hooked to solar when this happens. I will take a look at those power meters. The solar connection to the teardrop is SAE, and I need to replace the cable end (see pic) as for the second time it has busted on me. That’s a whole ‘nuther subject

57CFB30E-E6EA-4A25-A719-965495DC2535.jpeg (319.07 KiB) Viewed 555 times

Thanks again!