charging a battery with a battery

[canyonman]

For sake of discussion

If you had a very drained FJR size battery and hooked it to another fully charged FJR size battery and if the connecting wires did not limit the resulting current draw, what would the maximum current draw be?

Along the same lines what kind of current regulating circuit could be used in this scenario to limit the current draw to a desired level?

 

[ionbeam]

For sake of discussion

If you had a very drained FJR size battery and hooked it to another fully charged FJR size battery and if the connecting wires did not limit the resulting current draw, what would the maximum current draw be?

Along the same lines what kind of current regulating circuit could be used in this scenario to limit the current draw to a desired level?

Current flow initially could be on the order of 135 amps or more! Five or six 100 watt light bulbs in series would would make a good current regulator between the positive posts of the donor battery and the recipient battery. The bulbs can take the watts and limit the current to the 1 to 2 amp range :wacko:

Fred W?

Edited to add: This is what happens when ever you hook an electrically good vehicle up to a dead vehicle. It is almost always accompanied by lots of sparks and crackling noises. Even with a big set of jumper cables the current is usually limited by the wires. In the 'what if' the OP specifically stated the wires were not a limiting factor.

And with that little ditty, I'm on my way to the kitchen to make a fine New Years Eve supper --->

 

[Ignacio]

For sake of discussion

If you had a very drained FJR size battery and hooked it to another fully charged FJR size battery and if the connecting wires did not limit the resulting current draw, what would the maximum current draw be?

Depends on the wire size. 22 gauge....not so much. 8 gauge....probably more than enough.

We had an FJR rider last spring go from Montana to Washington without an alternator for about 1000 miles...by strapping a car battery to his pillion. Rode one headlight the last 200 miles.

Not ideal, but workable. As always a functional alternator is usually the more desirable than battery reserves.

 

[SLK50]

I may be electrically challenged but why would a "very drained battery" draw 135 amps?

Don't RVs often have batteries wired in tandem? ( parallel )

Wouldn't equilibrium eventually be reached, at which point available volts/amps

would be the total of both batteries?

Would the drained battery even place a load on the system?

 

[canyonman]

The idea behind the original question is I used a spare FJR battery last summer as a power source in camp and to power a portable shower that I rigged up.

The battery was good for maybe 15 showers (3 people) without charging laptop or other assorted crap I bring along. I would like to be able to plug the spare battery into the bike through my "fuze block" and charge it while riding without the initial current draw turning my auxillary wiring on the bike into a toaster or blowing the fuse.

I know there are commercially available portable battery/booster power supplies that I assume employ some sort of charge current limitation other than using the wires as a ballast resistor, however I already have the spare battery and it's nice knowing you have a spare with you.

I tend to camp as far off the beaten path as possible but still like to have most of the comforts of home.