Put truck and car on same trickle charger for a month?

[joshuabardwell]

I am about to go on a trip, and will be leaving my car (VW Jetta) and truck (Ram 2500) parked for about a month. I want to leave them on a trickle charger so that I don't get a disappointing surprise when I get home. I only have one trickle charger, though. If I were to use jumper cables to put the batteries in parallel, would there be any pitfalls to putting them both on the same charger? I know that, when you wire batteries in parallel, they exchange current until they balance out each other's voltage. I'm worried that if, for example, one of the batteries didn't reach the same voltage as the other for some reason, it might constantly be drawing current from the other, and run it down or something. The Ram has two huge batteries in it, that are pretty expensive to replace, so if it comes down to it, I'll leave the Jetta off the charger and put the Ram on the charger. But I'd rather do both.

 

[mbohuntr]

You already understand the problem.... Buy another inexpensive Schumaker trickle at wally world and do both.

 

[joshuabardwell]

You already understand the problem.... Buy another inexpensive Schumaker trickle at wally world and do both.

So it's not just in my imagination, then?

 

[Gary Fowler]

You shouldn't need anything on for only a month. I spent 8 month away and both my truck and wife's SUV were just left setting in the garage. Her's had an alarm system active and the battery was a bit weak but still cranked and truck cranked up as well as if I just left it a week ago. My truck was almost new (about 4 month old) but wife's car was 4 years old with original battery. I wouldn't worry about putting anything on if you don't have it available. Overcharging a battery is worse than no charge and some of the cheaper trickles will keep pumping juice to a battery till it boils out all the electrolyte.

 

[joshuabardwell]

I wouldn't worry about putting anything on if you don't have it available. Overcharging a battery is worse than no charge and some of the cheaper trickles will keep pumping juice to a battery till it boils out all the electrolyte.

I guess you're probably right. Especially the truck, with its massive two batteries, should do okay even if it's got a little drain on it. I'm just trying to cover my bases. Going away for so long makes me nervous.

 

[mrmikey]

if you're worried about residual draw why not just unhook them all....Mike

 

[Jim Nelson]

When I have a battery sitting for any length of time I put a cheap HF float charger on it. They will not charge a low bat. but will maintain a charge. You do need to coat the posts with a dielectric grease or they will corrode.

 

[MortalWombat]

For only a month I would just disconnect the battery cables and maybe put a shot of Stabil in the gas tank.

 

[JMER817]

Leave as is No need to do anything

 

[bumperm]

In general, lead acid batteries self-discharge (assuming no "phantom" loads), about 3 to 5% per month, less if colder and more if warmer. As others have posted, not much worry either way. If it'll make you feel better, charge the tractor for several days, then switch it to the truck before you leave.

A good trickle charger (of which Harbor Freights offering is *not*) will not boil the electrolyte out of any regular sized lead acid battery. Why dis the HF offering? Check the voltage . . . the several I purchased were putting out less than 13 volts. A trickle charger should, at room temperature, put out more like 13.7 to 13.8 volts - an appropriate "float" charge.

BTW, there are many "intelligent" battery maintainer chargers out there. Good ones will put out an amp or two, then as the battery voltage rises and charge current drops, they will switch over to a lower, maintenance charge mode. More better than the older, constant voltage trickle chargers like HF and others sell.

bumper