Why aren't batteries charging?

[Beetle]

We have two 6-volt, maintenance free (golf cart) batteries wired in series on our 19' 2014 Airstream International. When we checked them today with a volt meter, the reading was 6.5. We tried powering the batteries using our solar charger, but the reading didn't change after 2 hours. Then we hooked up to 30 amp shore power (briefly having both the solar and shore power connected at the same time). Now, about 10 hours later, the volt meter reading is still 6.5. What is happening? (Or should I ask why nothing is happening?) What should we do? Thank you for your help.

[TG Twinkie]

Where are you reading the voltage?
At each battery?

[SilverHouseDreams]

I think you need to share more info, I assume you are measuring 6.5 on the battery terminals directly and 6.5*2 would be 13V...which from what I know of AGM batteries would be 100% SOC. So what do you expect to be happening? What converter and solar charge controller are you using?

[carl2591]

6.5 for a 6 volt battery is FULL CHARGED.. check from one positive to other battery neg to get 12 volts and you should be at 12.8 12.7 again is FULL CHARGE.. carry on.

[uncle_bob]

Hi

If you are getting 6.5V on the 12V bus, there are a few likely possibilities:

1) You have a wiring error and the batteries are in parallel

2) You have a wiring error and the bus is hooked to the junction of the two batteries

3) One battery is completely shorted

The third one is a near zero probability so the first two are by far the most likely cases.

Bob

[OTRA15]

Originally Posted by Beetle

We have two 6-volt, maintenance free (golf cart) batteries wired in series on our 19' 2014 Airstream International. When we checked them today with a volt meter, the reading was 6.5. We tried powering the batteries using our solar charger, but the reading didn't change after 2 hours. Then we hooked up to 30 amp shore power (briefly having both the solar and shore power connected at the same time). Now, about 10 hours later, the volt meter reading is still 6.5. What is happening? (Or should I ask why nothing is happening?) What should we do? Thank you for your help.

Would you please update us, in light of the earlier comments/questions?

Thanks,

Peter

[Beetle]

The batteries are wired in series — and (the last time I checked) the reading was almost 13. I put the red test wand of the volt meter on the positive terminal on one battery and the black end on the negative terminal of the other battery. I am worried that I have let the batteries run down too far, and now they are damaged. How low a reading is ok for two batteries wired like this? Thank you.

[TG Twinkie]

If they read much below 12 volts. You have a problem.
If you are plugged in to shore power and the converter is working you should read something north of 13 volts at the batteries.
I would disconnect the batteries then read the output of the converter.
Also read the battery voltage while disconnected.
You may have bad batteries.

[OTRA15]

Be sure to wait a couple of hours, after you have removed all sources of charging, before you check the voltage of each battery separately [disconnect them entirely IMO].

[uncle_bob]

Hi

With series batteries and a multimeter, check each battery and see what you get. Next check the top of the stack with the negative disconnected and the converter running.

Possible outcomes:

1) Both batteries read 3.25V = your batteries have run down and need to be charged.

2) One battery reads 6.5V and the other reads 0V = You have a really strange dead battery.

3) Top reads > 12V with negative pulled and converter on = converter works to some degree

4) Top reads zero with negative pulled and converter on = converter is not on / connected / working and needs troubleshooting

If the batteries really are down around 3V, the converter may not kick in with the batteries connected. Many converters need to see some minimum voltage on the output before they will do their thing. (yes, it's weird that they also run into an open circuit, but most do).

If you have solar, be careful that it does not come on and confuse things ...

Bob

[68 Overlander]

Beetle, if you have the stock converter, it is a parallax and outputs a constant 13.8 VDC Many complain of overcharging because it does not vary the voltage like the 3 and 4 stage units do. If your converter hasn't overcharged and damaged your batteries, you should have 6.9 on each battery while connected to shore power and a resting OCV of 6.5 or so like you are reading, maybe a little less. Measured as a 12 volt, 12-7-12.9 resting OCV and ~13.8 connected to shore power.