Battery level low

[Funky]

We bought new batteries and a new converter. We thought it solved the problem but they only charge up to 2/3 and if we use the lights it drops to 1/3 battery.

 

[Kevin D Pem]

How do you know how full the batteries are?

 

[Funky]

How do you know how full the batteries are?

The lights will dim and fans are weak, the level indicator lights will say what level the batteries are at and we put a voltage meter on the batteries they will range from 7 volts to 11volts
(14 while the motor home is running.)

 

[AbdRahim]

alternator should be charging at 14 v.

 

[Funky]

alternator should be charging at 14 v.

The problem is when we are plugged into shore power the house batteries won’t hold a charge everything works fine when the motor home is running. We have been letting run to charge them up then they die a day later.

 

[Kevin D Pem]

12vdc is a dead battery at rest. That said most inverters shut down at 10.5vdc,because under load that is the magic number indicating 50%charge. With the same breath I will state, at rest a voltage of 10vdc indicates a dead cell, and 8vdc would indicate two bad cells.

Charge the batteries out of circuit for 24 hours. With batteries disconnected check voltage. That voltage after a couple of hours should read around 12.67vdc. In another day they should read much the same. If they don't record the voltage you just read, and measure again the next day. If they are down even further the battery has at least one maybe two shorted cells.

 

[AbdRahim]

Check to see what is happening at the pole. Problem could be outside your coach.

7v with the motor running is blow.

 

[Funky]

Check to see what is happening at the pole. Problem could be outside your coach.

7v with the motor running is blow

The pole is fine all 120 is working

 

[Funky]

12vdc is a dead battery at rest. That said most inverters shut down at 10.5vdc,because under load that is the magic number indicating 50%charge. With the same breath I will state, at rest a voltage of 10vdc indicates a dead cell, and 8vdc would indicate two bad cells.

Charge the batteries out of circuit for 24 hours. With batteries disconnected check voltage. That voltage after a couple of hours should read around 12.67vdc. In another day they should read much the same. If they don't record the voltage you just read, and measure again the next day. If they are down even further the battery has at least one maybe two shorted cells.

. After we replaced the converter we charged the batteries outside and they didn’t hold a charge they were 5 years old so we replaced them with new batteries and still having an issue

 

[Kevin D Pem]

Time to find the short!

Now for possible bad news! New means nothing, if the batteries were destroyed by over discharge.

Disconnect all loads, then use the multi meter and check for continuity (Batteries out of circuit). Alternate leads! By doing this you are looking for failed diodes, and shorts, in general. Replace each fuse one at a time, alternating leads as above, till all circuits are cleared.

A short need not be a complete failure, but will be quite obvious. Just curious, did you get sparks when you connected the new fully charged batteries?

 

[Funky]

Time to find the short!

Now for possible bad news! New means nothing, if the batteries were destroyed by over discharge.

Disconnect all loads, then use the multi meter and check for continuity (Batteries out of circuit). Alternate leads! By doing this you are looking for failed diodes, and shorts, in general. Replace each fuse one at a time, alternating leads as above, till all circuits are cleared.

A short need not be a complete failure, but will be quite obvious. Just curious, did you get sparks when you connected the new fully charged batteries?

Yes last night we took the battery cables off to clean them to make sure it was corrosion (they weren’t that bad) but when we were hooking them back up we put the cable on the negative post and it did give a little spark?

 

[Kevin D Pem]

Try again! It could have been a capacitor charging. Disconnect and immediately replace the cable. If it sparks again start looking for the reason.

 

[AbdRahim]

Btw, have you load tested the batteries. I had been wobdering why after driving all day (batteries charging at 14v) why they were only 80% charged and would seem to charge for days and never get to100%. These were relatively new good quality agms. It turns out ,even though all batteries show proper voltage at the battery, upon load testing, I found one battery completely dead under load. It got replaced under warranty.