# Battery Charging Issue - Perplexing



## daslobo777 (Mar 24, 2007)

Can a weak TV battery cause an issue with TT battery charging?

On our recent Thanksgiving trip to Durango CO - I saw some low charges occurring with the TT batteries. <----- Based upon a check of the intenal power meter - saw 2/4 LEDs light up. We were plugged in every night so I was not worried - just curious. Upon our arrival back home I removed the TT batteries and cleaned them and fully charged them up (2x6V). They took a good charge up to 12.7 VDC. The SG of all 6 cells was good. One battery was 3x 1.285 and the other batteyr was 3x 1.290. This tells me I have healthy TT batts.

So now I am looking at two scenarios: 1) Degraded TV charging while in tow, or, 2) A high current draw while under tow. Anything else?

Number 1: I checked the TV connector with engine off and read 11.9 VDC (low) from the +12VDC connector. I started the TV up and saw 13.7 VDC (normal). This tells me that I was getting good charging on the TT batts will in tow.

Number 2: Only loads on the TT batts while in tow was the fridge - which was on propane - but still uses small amounts of DC while on propane. No other power should have been on in the TT while towing.

So I have discovered that I may need a new TV battery - the current one is a Optima Red Top (~ 3 yrs old - which in the high heat of AZ is near the max life). But could the low TV batt have caused low TT batteries at any time? I will be taking the OB out after Christmas so will have to keep a close eye on this one. Any thoughts from the collective OB electrical brain bucket would be appreciated.


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## CamperAndy (Aug 26, 2004)

Don't trust the LED meter in the trailer for starters.

Check the actual voltages with everything connected, check at the battery and at the converter with shore power disconnected. I suspect a high resistance connection and it is most likely the auto reset thermal breaker mounted next to the battery. If the voltage is different at the two locations let us know.


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## thefulminator (Aug 8, 2007)

It could be nothing more that an bad connection somewhere between the meter and the batteries. If you have a wire or connector with oxidation or gunk, that would increase the resistance and show low voltage on the meter. Did you check the LEDs after you charged the batteries? If they show 4/4 without the TV connected then I would not suspect a problem on the trailer end of things. I assume you have an isolator in the TV? That should keep the TV battery from pulling off the trailer batts.


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## Ghosty (Jan 17, 2005)

CamperAndy said:


> Don't trust the LED meter in the trailer for starters.
> 
> Check the actual voltages with everything connected, check at the battery and at the converter with shore power disconnected. I suspect a high resistance connection and it is most likely the auto reset thermal breaker mounted next to the battery. If the voltage is different at the two locations let us know.


X 2 ...

You need to be checking the voltage wiht a VoltMeter and not trusting that the Chinese working the midnight shift who made the tester for the trailer actually made the LED reader within Tolerances...


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## outback loft (Sep 22, 2008)

I would check with a good voltmeter. Check the at the battery, then check inside at the converter/charger. If there is a big difference in the readings than you are getting some resistance somewhere, which would most likely be the auto reset breaker right by the battery.

I never go by the meter that came with the trailer, I have a digital meter in for the solar panels, and when I am unplugged, and have a complete charge I will be at 13.4, the point where the heat will no longer start-up is about 10.5. When I am at 12.0 the built in meter will say that the batteries are dead, but in reality there is a lot more time left.


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## Ridgway-Rangers (Apr 18, 2008)

I installed a Voltminder and monted it near the powere panel. Now I know what kind of charge the batteries are taking an exactly were they are as far as remaining power. I also discovered my charger/converter was only charging at 13.6 volts. I upgraded to a Progressive Dynamics 9200. Now I'm charging at 14.4 volts reaching 90% charge in 2-3 hours. It throttles down to 13.6 to top off the charge with a lower volt for maintaining a charge. It made all the differance.


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## daslobo777 (Mar 24, 2007)

Thanks everyone for the great notes. It has been on my list to add "voltminder" type device. I will move it up the mod list a few notches. I installed a Progressive Dynamics Inverter in my SOB RV before the OB. They are great units. I was under the impression the the WFCOs in the OB are 3-stage invertor/chargers (13.2/13.6/14.2)? Can anyone confirm/deny/comment to this?


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## CamperAndy (Aug 26, 2004)

Not sure what you want to confirm but the WFCO is a 3 stage auto charger/converter. Some do not like the fact you can not override the controls and force it to fast charge like the can on the PD with charge wizard. That said it normally does the job it is built to do.


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## hautevue (Mar 8, 2009)

Also--you noted that nothing else was "on" except the propane reefer. Remember that the propane detector runs on 12v and is "hot wired" so you can't shut it off. Also, some units have CO monitors that are hot wired. Our smoke detector uses a 9v battery so that's ok. But even with everything "off" you still have a small current drain. That's why the batts can die over a 2 or 3 month layover with no external help to charge them.

Also, look for some weird power drains--the stereo might have a nixie light or two, the television might have a small indicator light when it's "off" and so forth. And we found that the anti-sweating heater strip on the reefer door actually draws a not trivial amount of power. Good luck!


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