Matt G
Member
This post is an edited version of the original, which appears in my ongoing project thread At what's now the binder planet site. I've received several inquiries about this dual battery setup from guys wanting to do something similar, so I re-post it here for everyone's info. Mike mayben is the brain behind this system, so any questions should be posted here and I'm sure Mike would be happy to answer them. This setup would be very useful for anyone doing heavy winching, pulling a trailer with a battery of its own, or if you just want a backup power source.
Goodies list: sure power isolator & install kit, marine grade battery switch, 6 circuit fuse panel (for later accessories) and the much-discussed Ford style 4-post starter relay. The battery switch was the real gem of this lot: I sourced it from a boat dealership. It's a very well-made blue sea marine-grade switch which cost me $24.
First step, done at home before the install weekend at Mike's place, was to clear some under-hood space for all these goodies and the addition of a 2nd battery. To do this I relocated the windshield washer fluid tank to the center of the firewall, and extended the squirter motor wire to reach the new location:
That created a nice hole for the additional battery, isolator, and switch:
Once at Mike's place, we scoped out component locations and planned the cabling runs.
I opted to replace all the primary battery hold-down hardware while I was at this since it was so old and grungy - brand new trays under both batteries with new clamping hardware. Then a final check of component locations before we began wiring:
Next up was installation of the starter relay. In some ways this was the most intriguing part to me, because the Scout had stopped charging about 6 months ago. A good mechanic friend of mine bypassed the charging circuit by running a 8 gauge jumper from the charging post on the back of the alternator directly to the "+" post of the battery. This kept me on the road, but being the anal do-everything-right type I tend to be, I wanted to locate and rectify the culprit in the charging circuit.
My bulkhead connectors (surprisingly) are in fine shape. But we did find two likely culprits: first, the fusible link wire running into the b.c. From the alternator had blown. There was still some contact, but that seemed to be the clear problem. Also, when I got down low to relocate the wires from the starter motor we discovered that the ammeter-to-starter-post length of the charging circuit was partly melted and moderately corroded at the ring terminal end. Surely these combined were my problem, so we replaced both problem areas with all new wire, jumpered the starter posts properly for the new relay, and wired the relay up:
Now the real fun began as we began routing, measuring, cutting, and terminating wires. I replaced all battery cables with new 2 gauge cabling. We also completed a "bonded ground" system, running additional 2 gauge cable from the block to the frame (visible in the second pic below) - something Mike regularly preaches the value of doing. By the end of it we had estimated almost perfectly: every connection was made and almost no heavy cabling was left over.
I put a new optima red top in the primary position, and moved my 6-month-old napa battery into the auxiliary position.
Finally, this shot shows the new 6-circuit fuse panel - 2 circuits currently used: 1 for my cb and 1 for a 12-volt auxiliary power outlet in the dash for charging my laptop computer. It also shows the new charging circuit wiring & maxi fuse - note that I bypassed the bulkhead connector completely. The charging circuit now works like a charm.
Goodies list: sure power isolator & install kit, marine grade battery switch, 6 circuit fuse panel (for later accessories) and the much-discussed Ford style 4-post starter relay. The battery switch was the real gem of this lot: I sourced it from a boat dealership. It's a very well-made blue sea marine-grade switch which cost me $24.
First step, done at home before the install weekend at Mike's place, was to clear some under-hood space for all these goodies and the addition of a 2nd battery. To do this I relocated the windshield washer fluid tank to the center of the firewall, and extended the squirter motor wire to reach the new location:
That created a nice hole for the additional battery, isolator, and switch:
Once at Mike's place, we scoped out component locations and planned the cabling runs.
I opted to replace all the primary battery hold-down hardware while I was at this since it was so old and grungy - brand new trays under both batteries with new clamping hardware. Then a final check of component locations before we began wiring:
Next up was installation of the starter relay. In some ways this was the most intriguing part to me, because the Scout had stopped charging about 6 months ago. A good mechanic friend of mine bypassed the charging circuit by running a 8 gauge jumper from the charging post on the back of the alternator directly to the "+" post of the battery. This kept me on the road, but being the anal do-everything-right type I tend to be, I wanted to locate and rectify the culprit in the charging circuit.
My bulkhead connectors (surprisingly) are in fine shape. But we did find two likely culprits: first, the fusible link wire running into the b.c. From the alternator had blown. There was still some contact, but that seemed to be the clear problem. Also, when I got down low to relocate the wires from the starter motor we discovered that the ammeter-to-starter-post length of the charging circuit was partly melted and moderately corroded at the ring terminal end. Surely these combined were my problem, so we replaced both problem areas with all new wire, jumpered the starter posts properly for the new relay, and wired the relay up:
Now the real fun began as we began routing, measuring, cutting, and terminating wires. I replaced all battery cables with new 2 gauge cabling. We also completed a "bonded ground" system, running additional 2 gauge cable from the block to the frame (visible in the second pic below) - something Mike regularly preaches the value of doing. By the end of it we had estimated almost perfectly: every connection was made and almost no heavy cabling was left over.
I put a new optima red top in the primary position, and moved my 6-month-old napa battery into the auxiliary position.
Finally, this shot shows the new 6-circuit fuse panel - 2 circuits currently used: 1 for my cb and 1 for a 12-volt auxiliary power outlet in the dash for charging my laptop computer. It also shows the new charging circuit wiring & maxi fuse - note that I bypassed the bulkhead connector completely. The charging circuit now works like a charm.
