Relocating original battery and adding a second

[ss3964spd]

So, two issues provided the motivation to undertake this project; 1) the existing battery was in an incredibly inaccessable location - obviously installed before the deck was put on the hull and 2) I needed a 2nd battery to ease my fears of being out all day and draining the single battery. Also, in addition to the main positive and negative cables, and the cables for the drive trim pump, there were 4 other, smaller, wires connected directly to the battery posts. Not a good set up.

Original battery location was in the extreme rear corner on the port side. Access to this spot is either from the engine compartment or through a small access hatch adjacent to the engine compartment. This first photo is taken through that access hatch looking aft and shows some of the jumble of wires. Second is taken through the engine compartment, port side, looking aft.
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What you can't see is then almost two feet from the hatch opening to the battery. The original battery was placed back there, in a battery box that was too large for it, and held down with a single strap. The only way to get to the strap was from the engine compartment but, because of the angles involved it was very difficult to get enough pull on the strap to make it tight. If you could make it tight the battery would still bounce around because the strap would tighten around the box, not the battery. Lord help you if you had to actually get the battery OUT for any reason. You first had to disconnect all the cables/wires, then tilt the battery and box almost on their side, pull the battery from the box (the box would tend to slide with the battery), then lift the battery over a short divider and snake it along the port exhaust manifold towards the front of the engine, turn it 90* so it is parallel wth the front of the engine THEN finally lift it out.

None of this is fun while at the ramp. It does NOT come out through the access hatch, you have to get it through the engine compartment. At no point can you lift the battery directly from above until you get it next to the manifold.

I decided to relocate it right next to the engine, port side. I build a small shelf from marine ply, one side of which rests on the top of the port stringer, and the aluminum straps bend up and over of the hull. Secured with SS screws and holes filled with sealant.
First pic taken paralelle to the front of the engine, second is the shelf. The wires shown are attached to the side of the stringer.
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I didn't have enough room to use any type of retention method other than straps. I reused the original strap, add 3 more (two for each battery) and added some small blocks to keep the batteries located.

[ss3964spd]

I could have bought pre-made cables but to keep the runs as short as possible I made my own using 2 AWG cabling. Interestingly, West Marine sells everything to make them, and has a heavy duty crimper, but will NOT make them for you - something about liability. Cut to length, crimped, liquid electrical tape, and then finished with adheasive lined shrink wrap.
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A quick test fit before I added the extra straps and blocks.
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Time to locate and drill the hole for the battery switch.
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[ss3964spd]

I was concerned about heat from the engine affecting the batteries so I wrapped each with a heat shield. Last photo shows the install almost finished. Thankfully the original positive battery cable was just long enough to reach the switch, and the neg was long enough to reach the new battery location.
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Everything was cleaned up, and all wiring is secured with tye wrap mountings blocks and wraps. The cables for the trim pump were pleanty long so I tye wrapped them and terminated them to the "starting" battery. What I didn't photograph was how I handled the 4 smaller wires that used to connect directly to the original battery. Those were not long enough to reach to the new location so I bought a 6 screw bus bar, mounted it to the bulk head at the rear of the engine compartment, and ran a 10 GA lead from the common post on the switch to the buss bar.

In this configuration everything will work regardless of battery switch position, except the drive trim pump - which always has power to it. If the switch is set to OFF nothing has power (except the drive trim pump). I could have wired the pump to the switch but just didn't feel the need to do so. I also chose not to separate the "house" loads from the rest because there would have been far more re-wiring involved that I just didn't want to get into, and the main feed for the house loads originates at the engine starter - which is almost inaccessable on this boat.

The starting battery is a GP 24 lead acid - which was new last year, so I kept it. The "house" battery is a GP 24 AGM. I wanted larger batteries but the 24's are all I had room for.

I plan to use the set up as such - and assuming fully charged batteries: start the engine on Batt 1 and head out to where ever we're going. If we're going to drop anchor or tie up for a while somewhere shut it down and switch to Batt 2. Listen to the stereo, use the fresh water system, run the VHF radio, lights when necessary, etc. Time to leave - switch back to Batt 1. Once engine is running switch to Batt 1+2 so both will get charged. I can now easily get to both batteries and lift them directly from above when I need to.

Should work pretty well.

Dan