Second battery charging question?

[saburai]

Hi Gang,

I'm planning out my second battery system and had a question about a stop gap solution I'm considering. I'm a bit under the gun for time so to speak but I would like to have my auxiliary power up and running before we head out.
I noticed that my 12v jumper/compressor box is provisioned to be charged via the 12v lighter plug from the in cab lighter plug. Would it be feasible *as a stop gap measure* to use this method to recharge my second battery?

Many thanks!

 

[proto]

I would think a little jumper would be OK, if it meets your needs.

You should be aware that those things are usually built around a 12V gel-cel type battery. They're fairly easy to overcharge so I'd keep a watch on that and not necessarily just leave it plugged into the cigarette lighter full time. Also, the battery's life can be reduced drastically if you pull it down to a completely discharged state every day. Might not be a problem since this is a stop-gap measure for you. Good luck!

 

[saburai]

I would think a little jumper would be OK, if it meets your needs.

You should be aware that those things are usually built around a 12V gel-cel type battery. They're fairly easy to overcharge so I'd keep a watch on that and not necessarily just leave it plugged into the cigarette lighter full time. Also, the battery's life can be reduced drastically if you pull it down to a completely discharged state every day. Might not be a problem since this is a stop-gap measure for you. Good luck!

Hi Proto, Thanks for the input!

Maybe I didn't state my plan clearly, let me try again.

The question I was asking is would it be o.k. to use a lighter plug charging jumper on my house battery, a group 34 die hard platinum. It's the same as my starting battery. I want to charge it with the jumper while under way so that I can keep it topped off between over nights. I just don't have the time before we hit the road to finish up with the install of charging cables and a separator...

 

[proto]

(D'Oh! I really misread that one! Sorry.) So you're saying you don't want to burn up the charging jumper by asking it to supply too much current to the house batt?

Does the jumper have a resistor or diode or something inline to keep the current to a manageable level? If so, then you're probably good to go. The only issue would be whether the house battery will fully charge at the reduced current rate.

The lighter outlet in most vehicles is usually set up to handle 15 or 20 amps. You could check the rating on the fuse and look at the jumper's wires. I'd probably want to see 14 gauge or thicker to handle that current. Thinner is OK, as long as the current is held to an appropriate level.

 

[saburai]

Thanks!

At this point the jumper is theoretical...

Do you know where I could get a heavy duty jumper with a current limiter?

If not, I guess I'll have to put one together.
Any advice or tips would really help out.

 

[Mike S]

The current draw from the house battery will probably spike when the battery is discharged. This will likely exceed the capacity of your cigarette lighter type power port. You could fry the wiring and plug receptacle.

If I was in a big hurry to hook up the second battery, I would wire it so that the two batteries 'look' like one large battery, and both will charge from the alternator. This is the way most desisel trucks are wired.

M

 

[saburai]

The current draw from the house battery will probably spike when the battery is discharged. This will likely exceed the capacity of your cigarette lighter type power port. You could fry the wiring and plug receptacle.

If I was in a big hurry to hook up the second battery, I would wire it so that the two batteries 'look' like one large battery, and both will charge from the alternator. This is the way most desisel trucks are wired.

M

Thanks Mike.

Unfortunately, I don't have the time to run a second circuit from the engine compartment to the rear seat area...

Any other suggestions?

 

[proto]

Do you know where I could get a heavy duty jumper with a current limiter?

What I had in mind when I saw your post was this gizmo I saw at the local MicroCenter (computer store).

Sima EZ-Jump Car Charger Cable Kit 18-Foot

Doubtless there are other similar products. What struck me was that the label indicates it limits current to 9 Amps (which is why I remembered it).

This one comes with a cigarette lighter-style plug on each end, which may not be exactly what you want -- but it's a step in the right direction. Good luck with your project and your trip!