HOW TO STORE THE CHASSIS BATTERY

[BartnSandra Cross]

I am getting ready to winterize by 2003 Contessa for the first time.  My biggest concern is the chassis battery as it will be stored in Oregon for 9 months, under cover but no electricity available.  How do I keep the batteries charged so when I come back I can start either the engine or the generator?  Any help would be greatly appreciated.

[Joel Ashley]

If you can't regularly start the genset to top up things, you'll need to at least disconnect the battery cables altogether - even with main switches off there can be minor parasitic drains that would add up over 9 months.  It would then be preferable to remove them to somewhere that they can have Battery Minders attached and kept optimized.  

If that's not practical, then when you do return be prepared with a portable device or long jumper cables, which may be needed to start the genset;  then let it run until the inverter panel reads at least Absorb Charge, a safe state of charge that won't stress your alternator when you subsequently start the engine.  Using jumper cables for the genset start may not be so easy depending on how the coach is parked and your ability to get another vehicle oriented alongside, so keep that in mind.

Joel

[Robert Mathis]

Also remember that a dead battery will freeze. I would remove the batteries and take them to a climate controlled environment, fully charged.

[LEAH DRAPER]

You also ought to be mindful of mouse (mice) invasion for an un-tended motorhome.

[Edward Buker]

If your batteries are in good shape and if when you disconnect them, they are fully charged, they should survive the storage. I would make a diagram and disconnect all of the positive cables from each battery. You can tie wrap a ziploc plastic bag to the end of each cable end that you removed if they have a tendency to settle back on the terminal. The reason you disconnect them all is that a bad cell in a battery will pull down the rest and discharge the others. Just be sure all of the positive cables have been removed. If it is easier to fully remove the short jumpers rather than zip lock them that is fine also. If you have a solar panel I would zip lock bag and tie wrap the positive cables that come from the coach to the house battery set also.

Given it is nine months, if at the mid point you could measure each battery voltage and check the charge status that would be a good idea. 6.22V and 12.45 volts is the 75% charge state DC values for lead acid batteries. If any are below that value consider reconnecting the cables, start and run the genset and inverter/charger for several hours and shut down and disconnect again.

I had a boat in Vermont for many years that would have a charged battery set disconnected for 8 months of winter storage and then the batteries would restart the boat engine in the spring.  The fact that it is cold actually reduces the discharge rate which is a big help in your case. This is a little test done by a boat owner that will provide a good example and some measurements in support of disconnecting and leaving batteries in place for storage. It is a good practice if you have good batteries that are fully charged.

http://www.pbase.com/mainecruising/self_discharge

Later Ed

[BartnSandra Cross]

Thanks so much for all the help.  I talked to a friend this morning and he asked about me using a NOCO 12v Battery Saver 5.5 Watt Solar Charger.  Do you know anything about this?  The cord would have to be about 12 feet long.

[Edward Buker]

That would not be sufficient power and it is best to just disconnect as described.

Later Ed