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Battery/Starting Problem

Question:

Recently returned from a trip where I experienced a starting problem.  Unit is a Class A Southwind with two 6 volt Batteries in series for the coach and one 12 volt for chassis.  The Chassis battery which was 10 months old failed to start even with Aux battery boost. This was after several days parked and plugged into shore power.  Cleaned all of the cable connections I felt appropriate including block to frame and starter connections.  Finally concluded that the relatively new chassis battery was defective and took it back to Wally World where they said the battery was bad and gave me a new one.  All is fine and I proceed on my way. Engine cranks great and  I arrive home after about a week with no problems.  I plug into shore power again at home to unload etc and after about 48 hours I go out to move the unit and all the chassis battery will do is Grunt. Acting exactly the same as before I replaced  the battery.  It will start IF I apply the Aux batteries to boost the chassis battery.    Before I replaced the battery I had driven the unit for 4 hours and stopped and had to jump the battery to get going again. A volt meter I have installed to monitor the alternator output indicates 12 volts static and 13.5+ with the engine running.  This leads me to believe the alternator is OK. With engine off, voltage at the battery is about 12.7 volt and a cheap specific gravity tester indicates that the battery is OK. I haven’t found battery Isolation diodes in the system if they are there. I am beginning to suspect the converter is draining the battery and/or the disconnect relay’s are not making a good contact ( thus providing reduced voltage from the battery. Aside from the obvious ie: checking the connections and testing the new battery under load. Would be interested in any input particularly in regard to testing the converter.

Response:

I would measure the current in the batterey circut when the vehicle is "off". Remove the the negative cable and put an amp meter between the batterey and the cable. Then plug in shore power (or unplug it) to see if there is any difference.  Your vehicle batterey should have only a very small discharge if any. Sorobon

Response:

Checking the current drain on the battery with and without being plugged into shore power is a good plan.  Current drain with everything off should be very small, I would say 50 ma (0.05 amp) or less. Watch for the direction of current flow (plus or negative), not just the number. Checking the battery voltage with and without being plugged into shore power should also be instructive.  A decent Digital Volt-ohm-meter with a 10 amp ammeter would be useful, but it is possible that the current could exceed 10 amps through the converter.  You might want to buy a 50-0-50 ammeter, but don’t try to start the engine through the ammeter. Some converters will charge the chassis battery, but it is possible that part of the converter circuit is defective. Richard – Hide quoted text — Show quoted text – Recently returned from a trip where I experienced a starting problem.  Unit is a Class A Southwind with two 6 volt Batteries in series for the coach and one 12 volt for chassis.  The Chassis battery which was 10 months old failed to start even with Aux battery boost. This was after several days parked and plugged into shore power.  Cleaned all of the cable connections I felt appropriate including block to frame and starter connections.  Finally concluded that the relatively new chassis battery was defective and took it back to Wally World where they said the battery was bad and gave me a new one.  All is fine and I proceed on my way. Engine cranks great and  I arrive home after about a week with no problems.  I plug into shore power again at home to unload etc and after about 48 hours I go out to move the unit and all the chassis battery will do is Grunt. Acting exactly the same as before I replaced  the battery.  It will start IF I apply the Aux batteries to boost the chassis battery.    Before I replaced the battery I had driven the unit for 4 hours and stopped and had to jump the battery to get going again. A volt meter I have installed to monitor the alternator output indicates 12 volts static and 13.5+ with the engine running.  This leads me to believe the alternator is OK. With engine off, voltage at the battery is about 12.7 volt and a cheap specific gravity tester indicates that the battery is OK. I haven’t found battery Isolation diodes in the system if they are there. I am beginning to suspect the converter is draining the battery and/or the disconnect relay’s are not making a good contact ( thus providing reduced voltage from the battery. Aside from the obvious ie: checking the connections and testing the new battery under load. Would be interested in any input particularly in regard to testing the converter.

Response:

– Hide quoted text — Show quoted text – Recently returned from a trip where I experienced a starting problem. Unit is a Class A Southwind with two 6 volt Batteries in series for the coach and one 12 volt for chassis.  The Chassis battery which was 10 months old failed to start even with Aux battery boost. This was after several days parked and plugged into shore power.  Cleaned all of the cable connections I felt appropriate including block to frame and starter connections.  Finally concluded that the relatively new chassis battery was defective and took it back to Wally World where they said the battery was bad and gave me a new one.  All is fine and I proceed on my way. Engine cranks great and  I arrive home after about a week with no problems.  I plug into shore power again at home to unload etc and after about 48 hours I go out to move the unit and all the chassis battery will do is Grunt. Acting exactly the same as before I replaced  the battery.  It will start IF I apply the Aux batteries to boost the chassis battery.    Before I replaced the battery I had driven the unit for 4 hours and stopped and had to jump the battery to get going again. A volt meter I have installed to monitor the alternator output indicates 12 volts static and 13.5+ with the engine running.  This leads me to believe the alternator is OK. With engine off, voltage at the battery is about 12.7 volt and a cheap specific gravity tester indicates that the battery is OK. I haven’t found battery Isolation diodes in the system if they are there. I am beginning to suspect the converter is draining the battery and/or the disconnect relay’s are not making a good contact ( thus providing reduced voltage from the battery. Aside from the obvious ie: checking the connections and testing the new battery under load. Would be interested in any input particularly in regard to testing the converter.

I have a similar problem with a new Chinook on the Ford 450 chassis.  After two days of sitting without shore power, the chassis battery would not crank the engine.  It started fine using the aux boost switch to connect the coach batteries. A DC current meter in series with the chassis battery indicates an excessive and variable parasitic current flow – as much as 800 milliamps at times – except it randomly goes both negative and positive.  Finally determined that the polarity and amplitude swings were related to clouds passing and blocking the sun. Seems somehow the chassis battery is connected to the solar panel (it shouldn’t be).  I verified this by having my wife monitor the meter while I alternately covered and uncovered the solar panel with a black plastic trash bag, producing dramatic changes in the amount and polarity of the current flow. The dealer’s service department hasn’t a clue.  The manufacturer at first said this was impossible, but now has speculated that the aux boost switch is wired backwards.  I asked them to fax a wiring diagram so I could check it, but have not heard from them.  I was told it was a "proprietary device". I’ll figure it out eventually. Eisboch

Response:

Something in your coach is using the chassis battery. For examply, we have a "map light" under the tv which uses the chassis battery, as well as the dash "lighter" plug. Lon

If you have mirror heaters, check them occasionally.  I could tell by my dash battery meter that I had a significant load and couldn’t figure out what it was.  My knee must have hit the rocker switch at some point and turned them on.  It’s not a very noticeable indicator when it’s on. LZ

Response:

I had this very same problem in that the chassis battery was dead after sitting for 3 days & plugged into shore power.  I had to use the aux. batt switch (House battery bank) to start the unit.  Found out that I had hit the heater swich for the mirrors.  The indicator light on the switch is not at all bright during the daylight hours.  I now check frequently when I am near this switch to make sure it is in the off position.  Switch is right next to my hydraulic leverers.  My unit has a switch on the dash so that I can have the chassis battery on charge (via shore power) or not depending on the position of the switch. Burt

– Hide quoted text — Show quoted text – Something in your coach is using the chassis battery. For examply, we have a "map light" under the tv which uses the chassis battery, as well as the dash "lighter" plug. Lon If you have mirror heaters, check them occasionally.  I could tell by my dash battery meter that I had a significant load and couldn’t figure out what it was.  My knee must have hit the rocker switch at some point and turned them on.  It’s not a very noticeable indicator when it’s on. LZ

Response:

I am beginning to suspect the converter is draining the battery and/or the disconnect relay’s are not making a good contact ( thus providing reduced voltage from the battery.

Something in your coach is using the chassis battery. For examply, we have a "map light" under the tv which uses the chassis battery, as well as the dash "lighter" plug. Lon

Response:

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