Lithium 12v accessory battery
 

Question for you electrical gurus. Looking at options for replacing my 12v accessory battery (since I don't have room for it now). Lots of 12v lithium batteries that have a small footprint (wheelchair batteries that are 12 - 26 amp hours and many other lithium batteries that are 10 amp hours or less). I only use my accessory battery to power my headlights on the drive home from the golf course (1.5 miles) and to charge my cell phone and Bluetooth speaker. Any idea how many amp hours a battery would need for this application?

Thanks.

Re: Lithium 12v accessory battery
 

It depends on how many amps your headlight (and other accessories) draw.

If you have the typical 55W halogen bulbs, they draw about 5A each and two of them would be 10A, so it take 10AH to run them an hour.

You cam only use about 50% of the storage capacity of a lead-acid battery, but you can use about 80% of the storage capacity of a lithium battery, so to run your 55W (110W total) headlights for one hour, you'd need at least a 20AH lead-acid battery or a 12.5AH Li battery.


I don't know how many amps you cell phone charging and Bluetooth speakers draw, but they have to be add to the total amps used.

Personally, I'd add up the total amps for the maximum foreseeable time and at least double it, just in case I forgot to plug in the separate charger for the Li battery.

Re: Lithium 12v accessory battery
 

Thanks, Johnnie B.

Re: Lithium 12v accessory battery
 

Lithium batteries will work here if properly sized. You need Undervoltage protection AND you need the proper charger for them. One time discharging too far will kill the battery DEAD.

If you are short on room, a DC voltage reducer could solve that problem. Probably cheaper and easier than dealing with low voltage cut-off and charger for Lithium.

Re: Lithium 12v accessory battery
 

Since I already had a 12v onboard charger for my old "big" 12v marine accessory battery, I just bought a 12v (22AH) wheelchair lead acid battery. Small enough footprint (6 X 7 X8) to fit in the space next to my onboard 48v charger. I'll post pictures when it is installed.

Re: Lithium 12v accessory battery
 

22 AH 12V battery fit perfectly. A couple of big zip ties secured it. Now I've just got to move the onboard 12V battery charger.

Re: Lithium 12v accessory battery
 

All done!