Erratic Chassis Battery

[sixkilo]

I have a 2002 Minnie Winnie 430V with both coach[2 yrs old] and chassis batteries[1 yr old]. The chassis battery has taken to going dead overnite intermittently. I recently completed a 5K trip and as I said it was happened some days ad not others. Before I left I did install new back up camera and Ready Brake towing system with braking lite signal both of which I wired into the Parking brake switch hot wire. I have disconnected each one from system and it still goes dead at times. Shoreline keeps coach bats up just fine but not chassis.Thanks

[BFlinn181]

I'd first remove, clean, and inspect all battery connections, including those to ground. After batteries have all been charged, you can do a specific gravity test of each battery cell to see if you have a dead cell. Any battery seller or auto parts store usually will do a load test on the battery for free to determine if it needs replacement.

I don't think your RV had the wiring to charge the chassis battery from converter/charger, you might want to add a Trik-L-Start to keep battery charged.

If the battery checks out O.K., next you'll have to determine if your wiring modifications have set up a drain on the chassis battery. Measuring the amp draw with ignition off, then removing fuses, one at a time, to see which circuit has the heavy drain would be the way to track down the issue.

[sixkilo]

I did a quick online search for parasitic video and got a good idea of how to do that. I will go to basics as you suggest and see what happens. Thanks

[sixkilo]

The culprit was the radio memory circuit. It was drawing off .61milliamps. I didn't think that that was enough to draw down to completely dead overnite, but we will see tomorrow. The radio never gets used due to cd player defunct and I installed house receiver to use with shore power.

[jelag]

so, the .6 miliamp draw is not enough to draw down the batteries in a short time... almost all modern vehicles have some basic power draws... as an example the engine ECM is always powered up.. but needs to receive a key on signal to fully power up and do its job.... power door locks... or any item that is run with a remote also have full time power..

You have several choices.... there is what is called a 3 minute cell test.... using a digital volt meter you check the actual voltage of each cell... looking for more than .2 volt difference means a bad cell...

You can purchase a simple 10 amp meter that will install in the ground or 12+ lead... you can than see the actual amperage draw... and than pull fuses one at a time to find the circuit...

One thing I've found that really helps... is to find a u-tube or other text on understanding ohm's law... and how to measure voltage, amperage and wattage.. once you have a handle on ohm's law you'll be better able to attack your problems...

BTW - there is usually a set of diodes.... charging voltage/current from the engine or converter flows through these isolation diodes to prevent back flow from the chassis and coach batteries... if one of these diodes is bad... current can flow from one circuit (coach) to the other (chassis)..

[sixkilo]

I did the parasitic volt test via multimeter and found the radio memory circuit to be drawing .61 mv. Left fuse out and the drain dropped to .01mv. I did not think that .61mv was enough but as you suggested I did find video where the tester felt it was. I had seen another video where the presenter stated .50mv was the target thus my mistake. A drop from 13.47 to 13.1 volts day one. I will check again today. Thanks for the info on relationship between house and chassis.

[TQ60]

Any static voltage above about 12.6 is "float voltage".

The battery magic of charging...There is a bit of energy there that can be used and that is what yiu are measuring.

It can be a great amount...we once used the time to consume the float charge as a battery test procedure so it can be used.

In your case if you cannot measure a load more than 0.5 amps and yiu have a dead battery in the am either the battery is toast, the charge is not complete or there is something coming on that is loading the battery.

The measured voltage indicates full charge so skip worrying about that for now.

Fist actiin should be to test the battery.

Simple load test.

Charge it fully then just turn on headlights and monitor terminal voltage and see if it drops fast or holds up for a bit.

If yiu can measure amps then measure the load of the lights then divide the amp hour rating by that.

Starting batteries usually do not post amp hours but look at size then Google one of same size to see.

Example is a group 27 battery is often 100 ah to 125 ah so use the smaller then divide.

If lights used 25 amps in above then about 4 hours would be it.

If voltage drops to below 12 in a very short time the battery is toast.