Voltage too high with shore power

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Voltage too high with shore power

May 09, 2021, 08:17:05 pm

We installed two new 6v batteries. When we operate on battery power, we have 12 volts. However, when we plug into shore power, we are getting 19 volts. This additional voltage is causing problems for us, our Maxxfans won't operate, for one example. What could be causing this overage and how might I resolve it? Any ideas?

Re: Voltage too high with shore power

Reply #1 – May 09, 2021, 08:27:16 pm

If you are sure you got the battery wiring correct, then I'd have to guess that your converter is bad.

Art

Re: Voltage too high with shore power

Reply #2 – May 09, 2021, 08:39:03 pm

Bad converter, kind of what we were thinking too.☹️

Re: Voltage too high with shore power

Reply #3 – May 09, 2021, 08:58:48 pm

If you turn off the converter will the voltage drop back to normal 12v?

Re: Voltage too high with shore power

Reply #4 – May 09, 2021, 11:10:30 pm

I’m not sure I understand the question. When the converter is off, doesn’t that mean we are on batteries only? Because when we are on battery power, our power is normal voltage range.

Re: Voltage too high with shore power

Reply #5 – May 10, 2021, 02:16:36 am

When you measure 19V, is that at the battery terminals? If not, measure the voltage there and see what you get. If 19V, then replace the converter. If 12V, then the converter charger is blocked from reaching the batteries. Bad fuse or circuit breaker.

Steve

Re: Voltage too high with shore power

Reply #6 – May 10, 2021, 08:55:28 am

Quote from: SoCal-girl - May 09, 2021, 11:10:30 pm

I’m not sure I understand the question. When the converter is off, doesn’t that mean we are on batteries only? Because when we are on battery power, our power is normal voltage range.

Maybe I did not make my question clear. A better way to ask is when you switched off your converter would the displayed voltage dropped back to 12v? If the displayed voltage drop back to 12v, it is likely the converter is at fault or the converter is NOT reaching the battery pack for some reason. Typically the open circuit voltage of a converter could be as high as 19v (like an unregulated solar panel). Just as Steve said, please measure the battery pack voltage at its two terminals to figure out what is the "true battery voltage".

If the battery terminal voltage is 12v but the displayed voltage is still at 19v, the cables from the converter are not reaching the battery pack and batteries are continued to be drained. In this case, check if there is any fuse or circuit breaker that tripped. Also check if the converter charging cables are still wired correctly when you changed the batteries.

Best of luck trouble shooting...

Re: Voltage too high with shore power

Reply #7 – May 10, 2021, 09:26:34 am

Just poking my nose in... If you actually are at 12v with the batteries, that is low. A charged battery bank should read more like 13.4 volts. If you are actually getting 12, that would indicate that they are not getting charged.

Ken F on the road

Re: Voltage too high with shore power

Reply #8 – May 10, 2021, 10:48:13 am

A few questions are in order...

Is the coach electrical system original. or has a previous owner modified things?
Where and how are you reading the coach battery voltage?
Precisely what voltages are your reading, with and without shore power applied? (a multimeter reading across the battery posts is best)

Art

Re: Voltage too high with shore power

Reply #9 – May 10, 2021, 01:05:00 pm

Quote from: Older_Fossil - May 10, 2021, 10:48:13 am

A few questions are in order...
Is the coach electrical system original. or has a previous owner modified things?

If your rig still has the original converter, it should be replaced due to its lack of intelligent charging. the old converters were not solid state, instead using old-school transformers. They tended to overcharge batteries and charge at much slower than newer, “smart” converters”.
Waiting on the voltage measurements.

Larry

Re: Voltage too high with shore power

Reply #10 – May 10, 2021, 02:40:43 pm

Quote from: Kenneth Fears - May 10, 2021, 09:26:34 am

Just poking my nose in... If you actually are at 12v with the batteries, that is low. A charged battery bank should read more like 13.4 volts. If you are actually getting 12, that would indicate that they are not getting charged.

Ken F on the road

To clarify, a fully charged "12 volt" Deep-Cycle Flooded/Wet Lead-Acid Battery (or bank) resting open circuit voltage is 12.74. If the same battery is being charged and is at float charge it would be at about 13.5 volts. A battery at 12.0 volts is at 50% state of charge.

Charles

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