Battery 18 volts ???

[billyfish]

So...my starter battery is suddenly started showing between 15 and 16 volts on the boats volt meter. Put a multimeter on it and got 18 volts . So disconnected it and started puzzling. Only thing I can think of is the solar controller got a bit rusty, I did clean it up and looked fine...only a 10w panel so not getting overcharged from there. But is it taking power from the house bank 2x120

 

[VicS]

So...my starter battery is suddenly started showing between 15 and 16 volts on the boats volt meter. Put a multimeter on it and got 18 volts . So disconnected it and started puzzling. Only thing I can think of is the solar controller got a bit rusty, I did clean it up and looked fine...only a 10w panel so not getting overcharged from there. But is it taking power from the house bank 2x120

It cannot take power from something that's at a lower voltage but the open circuit voltage of the solar panel is around 22 volts and could do if the regulator is stuffed

 

[billyfish]

It cannot take power from something that's at a lower voltage but the open circuit voltage of the solar panel is around 22 volts and could do if the regulator is stuffed

Arh

 

[andsarkit]

A 10W panel is very unlikely to raise the battery voltage to 18V on a healthy battery especially at this time of year. It would be doing well if it could maintain 13V in the recent overcast conditions. I have perfectly aligned solar panels on my house roof and if I scale down the recent weeks output to a 10W panel it will be producing less than 40mA (1Ah/day) averaged over the day. Something is not right.
Can you check the voltage after it has been standing completely disconnected for a few hours?
Can you check the voltage on the house batteries. If they are also high you could have a faulty meter.
The battery could have failed internally and have a high resistance or a bad connection. You could then be measuring the solar panel voltage with the battery drawing negligible current.
If you can put the battery under load of at least a few amps and monitor how the voltage holds up, this will indicate if it has failed.

 

[Gsailor]

Yes, sounds most odd on a tiny solar panel.

Disconnect battery from everything, test voltage again.

Check fluid levels if not a sealed battery.

Test specific gravity with one of those hydrometers.

Let us know how you get on; wisdom shared etc...

 

[VicS]

A 10W panel is very unlikely to raise the battery voltage to 18V on a healthy battery especially at this time of year. It would be doing well if it could maintain 13V in the recent overcast conditions. I have perfectly aligned solar panels on my house roof and if I scale down the recent weeks output to a 10W panel it will be producing less than 40mA (1Ah/day) averaged over the day. Something is not right.
Can you check the voltage after it has been standing completely disconnected for a few hours?
Can you check the voltage on the house batteries. If they are also high you could have a faulty meter.
The battery could have failed internally and have a high resistance or a bad connection. You could then be measuring the solar panel voltage with the battery drawing negligible current.
If you can put the battery under load of at least a few amps and monitor how the voltage holds up, this will indicate if it has failed.

My 5 watt panel will get my 60 Ah leisure battery up to that sort of figure, but perhaps not at this time of year.. No regulator.

 

[billyfish]

Yes thanks all. The house batteries were fine. Disconnected the positive on the start one and cant get back till Thursday but will check that before reconnecting

 

[William_H]

I would suspect that you are measuring solar panel output with battery disconnected as in a bad terminal. Or possibly a bad battery but perhaps less likely. ol'will

 

[QBhoy]

How many batteries do you have ?

 

[Boater Sam]

Shot or disconnected battery, and solar controller US
Time to spend.