Another Dual Battery Project

[Justinwht]

I've read over a dozen posts for ideas for dual batteries, some going back over ten years.

I'm looking at my options to install two batteries in my 2000 Explorer using two completely different ideas.

In past few months I've had the battery drain too low from overnight charging my phones, tablet, power banks and a pair of .3 amp fans for circulation. A lifesaver was the EverStart Maxx EL224 lithium jump starter for $64 from Walmart, little larger than pack of cigarettes.

Moving forward with my two options for second battery.

Install a 12 volt LiFePO 30 aH battery ($89) mounted behind driver's seat and feeding dedicated power ports mounted on rear door frames using 14 ga wires. The battery weights only 8# and can be stuck in a gym bag and carried inconspicuously into a fast food place, and recharged in two hours with a 20 amp charger ($69).

My second option is a matching 65 / 650 CCA lead acid battery again mounted behind driver's seat with some sort of venting to outside or crack rear windows open. Connect the alternator to a 400 amp waterproof two-position switch inside engine compartment, and 0 ga wire. The advantage is I'll have a second starter battery that I'll alternate once a week running either battery while driving around.

Shameless endorsement for the EverStart Maxx EL224 jump starter battery. Says dead battery should be at least 50% charged and with all four blue lights on jump starter. I've started a fully dead battery from headlights left on overnight and only two blue lights. Started slow but at least started. Tip: let the jump starter charge the vehicle battery five to ten minutes first if engine not start on first try. I get several jump starts from it. Recharges in 4-6 hours with 3.0 USB charger using a micro USB cable.

 

[toypaseo]

Why such huge wiring for the second option?

A buddy of mine had a four Alpine amplifier system, around 2000 watts I think, in his 91(?) GMC extended cab Sonoma. He had a battery in the stock location under the hood, and one inside the cab in a battery box. Not sure on exactly he had them wired together, but he did use 4ga cable from Parts Express. Below, is the wire he used, although discontinued now…

Home

JSC Wire 4 AWG Red High Current Power Cable 1 ft. USAThis power distribution cable is the premium choice for your car audio amplifier or accessory. Features multi-stranded rope lay bare copper construction for lower resistance with optimum current flow and an ultra-flexible, chemically...

www.parts-express.com

 

[Justinwht]

You're right, 0 ga is overkill for ten feet, I'll use 4 ga.

I think I'll go with second option because of inconvenience of first option where I have to find a restaurant where I can sit two hours and carry in the spare battery.

Mounting another 65 battery in engine doesn't look feasable so I'll place it behind driver's seat (I'll be removing rear seats for more storage space and cover area with hinged plywood). I'll run a single ten foot #4 gauge fused (?) positive cable to behind driver's seat and ground negative return to frame.

(?) I'm reading the Explorer 4.6 Liter engine starter pulls 250 amps but engine compartment starter fuse is only 30 amps.
What fuse should I use for my #4 gauge wire?

I've read where some users connect spare battery to engine battery with jumper cables to jump start engine.
I found a 3-position 300 amp switch - battery 1, off, battery 2 for battery use/charge select, and a 2-position switch - on, off for dual battery jump starting (drawing attached).

 

[Justinwht]

 

[Justinwht]

Switch #2 and #1

 

[Justinwht]

I could find room for a size 34 or 35. Since I'm not using a solenoid or electronic dual charger, the batteries don't have to match.