no charge at batteries

11.7 is a dead battery. 13.8 sound like you have a charge voltage on the battery.

Did you put a voltmeter on the battery with/without the charger plug in. Build in volt meters usually are not very accurate.

If you have a different charge, pull the neg. cable and charge the batters at 2 to 10 amps till they show they are charge. This can be from 6 to 24 hours. Write down that voltage. Should be around the 13.8 for a good battery. Wait two hours plus and connect the neg. cable back and put a load on the battery for a while. Do not take it down more than 12.4 volt.

Did you take a battery hydrometer test since you said you water level is good? Write down each cell before you charge and 2 hours after your charge and before you put a load on the battery.

Last take a battery volt reading and then plug in your charge and take a reading. You should see close to 13.8 if it is working.

MountainAir05's advice is great.

How old are the batteries?

11.7 volts is funeral time…dead, dead, dead. Think about Lithium when (not if) replacing.

Yes! Do this…”Last take a battery volt reading and then plug in your charge and take a reading. You should see close to 13.8 if it is working.”

What was the voltage before you put it on the charger? Lead acid batteries are just over 2 volts per cell. If you read 10 volts you have a dead cell in the battery. If it has a dead cell it's time to replace the battery.

The batteries are one year old.. When The cables from the converter back to the batteries are disconnected, the converter puts out 12.7 volts.
The volts at the batteries before the charger was put on was 2.8

2.8 or 12.8? If actually 2.8 you had a drain that dragged them way down. You might be able to recover them with a charger, but they are damaged. How much they are damaged will depend on how long they sat discharged. If you mainly go from electric hookup to electric hookup i wouldn't worry about it much. If you do dry camping or boondocking I would replace them.

12.7 is not enough. Maybe the converter needs to see a battery before it goes full charge. Try disconnecting shore power and then hook up the battery. Take a voltage reading across the battery terminals and write it down. Then plug in shore power and take another voltage reading. You should be seeing at least 13.2 volts if the batteries are fully charged.

Check the voltage of the starting battery or the starting battery of your car to make sure your meter is working.

Give us the readings and we can tell you if it looks like anything is wrong.

12.7 is a float. You need new batteries.

2.8 volts is dead, as in dead, dead.

Do you have the Magnum Inverter/charger or just a converter/charger?

If you have the Magnum run the batteries through an equalization cycle and you might save them, maybe. I do that about every 6 months (maybe a year?), we got around 9 years out of our original batteries.

If it is the Magnum Inverter/charger, to do an equalization cycle you push and hold the charger on/off button until "Equalization" shows up on the screen.

It would seem the converter is good. 13.8 volts. The batteries are shot