Batteries not charging

[dave14117]

05 Cougar fifth wheel, 2 year old Costco batteries.

Today tried to fix problem battery not charging when on AC power. Seems to charge ok when connected to truck; not sure. DC lights do brighten when on AC or truck, dim when no AC or truck.

I think the converter gets AC power, converts to 12v DC for the panel, and somehow also then sends 12v (@ ? amps) to charge the battery. So given that the lights brighten and its fan works, I think the converter must be getting AC power. But somehow the batteries aren’t being charged. Not sure if the charging ckt goes through the panel; if it does, all the fuses are ok, so maybe chewed wiring?

So far:
Checked auto fuses, all ok
Checked ground in basement and in panel area
Added water to batteries

Solution attempts
Removed TV/Stereo 12v fuse (disconnected it a month ago because it was making constant alarm; might still be drawing power)
Removed GFCI and replaced with regular outlet
Added tape to mice-chewed ground wire going from basement to panel

Any ideas appreciated

[mr__ed]

dave14117 wrote:

mr. ed wrote:
I assume you've removed the cables and cleaned the battery posts and cable clamps. Corroded terminals are a common source of battery problems.

Good news maybe - have batteries on separate battery charger, so far for 7 hrs. Voltage with charger disconnected is now 13.3v

Are both batteries still connected in parallel? If both are holding a charge for a decent time it appears they're good and your onboard charging system has some sort of issue which hasn't been found yet. OTOH, if the batteries are connected back to your RV's electrical system without the RV connected to shore power and you find the charge dissipating without any 12 volt items turned on, there is a parasitic draw somewhere that's taking a small amount of current. The fridge is one possibility as well as other electronic devices. I'm assuming your water pump is turned off, since it may run briefly when water pressure drops a certain amount.

[dave14117]

mr. ed wrote:
I assume you've removed the cables and cleaned the battery posts and cable clamps. Corroded terminals are a common source of battery problems.

Good news maybe - have batteries on separate battery charger, so far for 7 hrs. Voltage with charger disconnected is now 13.3v

[dave14117]

mr. ed wrote:
I assume you've removed the cables and cleaned the battery posts and cable clamps. Corroded terminals are a common source of battery problems.

Batteries and posts are clean.

[mr__ed]

I assume you've removed the cables and cleaned the battery posts and cable clamps. Corroded terminals are a common source of battery problems.

[Artum_Snowbird]

If you have been connected to A/C and your battery measures 13.6, then disconnected you only show 12.5 it's evident that your battery cannot take the charge. If you can but an external battery charger onto the battery for awhile, then take it off and it still measures 12.5 and does not go higher, then you battery is done. An old battery just cannot hold a charge, it's likely worn out.

[pianotuna]

At 13.6 volts it may take 3 or more days for the battery to become fully charged.

Here is a graph. The middle line is 13.6 volts, the converter is a 55 amp and the battery is 125 amp-hours of capacity:



The existing battery bank may be sulphated from chronic under charging and it may take some effort to get most of the capacity back.

[Sandia_Man]

With converter on and you measured 13.6 Vdc at the battery, your converter is indeed providing a charge to your battery. With 12.5Vdc measured when converter is off indicates charging circuit is intact although battery is not fully charged. If you don't have a smart converter that 13.6 Vdc will take some time to get the job done, single stage converters will shorten the longevity of any battery.

[dave14117]

dave14117 wrote:

Artum Snowbird wrote:
Easy fix. Either your positive to the battery, or your negative to the battery both from the converter has a loose connection.

Cut a short wire and screw it into the negative terminal on the converter, then use your jumper cable to connect to that, and to the negative on the battery. Plug in to power. Do the lights get bright. It's the negative side that has a loose connection.

If not, do the same, by itself, with the positive side at the converter, and to the positive side of your battery. Do the lights get bright. It's the positive side that has a loose connection.

In my case, I found the main negative terminal at the converter to be loose, my batteries went down when I was plugged in, and came up when I drove. I wiggled the wire, and bingo, found the problem just like that.

Start there, at the converter with the main positive and negative feed screw terminals to the battery.

Your idiot lights on the charging terminal should show full lights when plugged in. When my cable was loose, the idiot lights kept going lower and lower.

I'll try this tomorrow p.m. Thanks

Not sure I'm following this...lights are bright when on power now.

[dave14117]

pianotuna wrote:
Another way to check is to use a volt meter.

Measure the batter voltage.

Then plug into shore power.

Measure again. The voltage should be higher.

How many times have you deep cycled the jars?

Voltage is 13.6v when on power; 12.5v when not on power. Deep cycled count is maybe 10?

[pianotuna]

Another way to check is to use a volt meter.

Measure the batter voltage.

Then plug into shore power.

Measure again. The voltage should be higher.

How many times have you deep cycled the jars?

[dave14117]

Artum Snowbird wrote:
Easy fix. Either your positive to the battery, or your negative to the battery both from the converter has a loose connection.

Cut a short wire and screw it into the negative terminal on the converter, then use your jumper cable to connect to that, and to the negative on the battery. Plug in to power. Do the lights get bright. It's the negative side that has a loose connection.

If not, do the same, by itself, with the positive side at the converter, and to the positive side of your battery. Do the lights get bright. It's the positive side that has a loose connection.

In my case, I found the main negative terminal at the converter to be loose, my batteries went down when I was plugged in, and came up when I drove. I wiggled the wire, and bingo, found the problem just like that.

Start there, at the converter with the main positive and negative feed screw terminals to the battery.

Your idiot lights on the charging terminal should show full lights when plugged in. When my cable was loose, the idiot lights kept going lower and lower.

I'll try this tomorrow p.m. Thanks

[dave14117]

corvettekent wrote:
Put a volt meter on the batteries with the converter turned off, what is the voltage?
Now turn on the converter, what is the voltage?

Converter on (AC power on) - 13.6v
Converter off (AC power off) - 12.5v

[dave14117]

ScottG wrote:
Could be the battery is kaput.
Or, is there any chance it was hooked up backwards recently? If so then the reverse polarity fuses would be blown. (usually 3 fuses away form the others)

No changes recently. New batteries 2015.

[Old-Biscuit]

IF battery hooked up backwards...reverse polarity fuses ON converter BLOW....BUT if they are blown the converter has NO DC output.
Lights work so reverse polarity fuses OK

Battery in-line FUSE (or a DC circuit breaker) on Battery POS cable to converter.
If BLOWN.no DC from battery and No charging from converter to battery
Measure DC Voltage at converter where battery wires connect......with converter OFF and then with converter ON.
In-line fuse blown...no DC Voltage at converter with converter OFF (S/B 13.2V with converter ON....or converter failing)

Battery NEG cable not making good ground connection on frame