|The old battery bank...and some baking soda to neutralize acid|
I've been doing research on batteries and have found that many don't consider most of the marine deep cycle batteries to be very good or capable of deep cycles. Add in the fact that the identical replacement batteries cost $700 each (and I need 3) and spending that kind of scratch on a less than good solution seemed silly. Golf cart batteries (group size GC2) are generally considered to be much better at deep cycle use, and two of them fit within the footprint of the group 4D batteries (that is the size that currently make up my house bank). They are generally less expensive and have higher amp-hour (Ah) ratings so this decision was fairly easy.
Then came the great AGM versus wet cell debate. There are certainly pros and cons to both options. The big pros for AGM are the lower maintenance requirement, low self discharge rate, and faster charging. The pros for wet cell are they can tolerate overcharging a bit better, seem to have a bit higher capacity, and are cheaper. To us, it was a real toss up. The existing batteries are AGM as are the engine start batteries, so we figured we would likely go that route.
That is, until we tried to get some. The local Napa store didn't have any in stock, and the ones they could get seemed inferior to many others. The guy at the local golf cart store tried to locate ones from a variety of different suppliers and only found two options. One he wouldn't be able to get until mid February and the other was over $300 each. On the other hand, he had just received a pallet of 232 Ah wet cell batteries that cost $105 each. We tried looking online for AGM's as well, but between shipping and the inability or cost to ship the old batteries back (cost of batteries usually includes returning the old ones back for recycling...since all that lead is still worth some money) and the resulting core charge we would have to pay (over $200), it wasn't a feasible option. So, the decision was pretty much made for us...we would go with the wet cell batteries. Since the race between AGM and wet cell was so close in our minds, we really didn't mind this route.
|The new batteries|
We bought 6 of the US 2200 XC2. These are 6 volt batteries rated at 232 Ah. By wiring two of these in series, I end up with a 232 Ah 12 volt "battery". Wiring 3 sets of these in series would give me 696 Ah. The old batteries were 198 Ah each, so the battery bank, when it was good, was a total of 594 Ah. This means the new setup will give me an extra 102 Ah. Of course, for best life you are only supposed to discharge batteries to 50%, so this gives me an extra 51 Ah of usable power. Not too bad, particularly when you consider the fact that all the batteries cost less than just one of the West Marine batteries.
Of course, the batteries weren't the only cost related to this change. I needed 3 new cables to connect the 6 volt batteries in series to make 12 volt battery sets. I considered ordering some custom cables from GenuineDealz (I've purchased wire from them before and have seen their custom assemblies), but being a bit impatient, I opted to have them made locally. The Napa Auto Parts in Southport stocks a variety of marine grade stuff and that included the 2/0 marine grade wire and crimp on connectors needed to make the cables. They made me the 3 cables I needed for a little under $40.
Getting the old 4D batteries out of their home in the cockpit locker wasn't as bad as I thought it might be. Doug, the harbormaster at Deep Point Marina, came and helped me lift them out of the locker and get them off the boat and to the car. We put them in some heavy duty trash bags and took them to the battery store to trade them in for the $35 per battery core charge (the golf cart store was nice enough to understand that a 4D battery was roughly equivalent to two "cores" so we could get the 6 core charges refunded with the 3 4D batteries). After getting the batteries out, we had a little cleanup to do. We ended up using 3 boxes of baking soda and copious amounts of water to clean up the mess we made trying to revive the old batteries. This took quite a bit of time, but after a few hours the battery box was reasonably clean and ready for the new batteries...or so I thought.
Before I decided to go this way I spoke with a couple of people who owned Leopard 38's and have done this change, and they reported no fit issues. When I measured the space (as best I could when the old batteries were still sitting in there) it looked like it was going to be close. So, naturally, the batteries didn't quite fit. I guess my battery box was just a bit smaller than the boats that came after mine, and the two golf cart batteries, when placed end to end, wouldn't quite fit into the tray built to hold the old 4D batteries. I ended up having to modify the tray so there was enough room. Height was also a minor issue, and I had to modify the ledge that holds the shelf/lid to the battery compartment in order to get the batteries to fit. Not major reconstruction, but not a slide in replacement either.
|Minor technical adjustments to the battery box|
Finally, after many hours of cleaning and reworking the battery box, the new batteries were placed in the compartment and wired up. Connections were checked, and after verifying everything looked OK, we flipped the switch and brought the electrical system on the boat back to life. Before letting the inverter/charger go to work charging the bank, I changed the settings to represent the new battery bank configuration. Then the charger was started. It seemed happy with the batteries and charged them up after an hour or so (being new, they were mostly charged when we got them). Since it was getting dark and cold, we decided to finish the last parts of the install in the morning.
|The new house battery bank wired up|
The next morning I started by running a couple tests to confirm everything was working as it should. I ran the inverter with high load (our smaller cabin AC unit) and checked temperatures of the batteries, battery terminals, and cables with a non-contact thermometer and only saw a couple degrees of difference after letting the unit run for 15 minutes or so. I then turned the charger back on and took more measurements to verify everything is fine.
Then came the finish work on the battery box itself. With the cables attached it took up even more room above the batteries, and I decided I needed a little under an inch of extra height for the lid. I added some wood strips to the battery box lid and mount to give it more clearance for the taller batteries and cables. I also repositioned a couple of the wires to allow better access to the battery vent caps.
|Modified ledge so everything fits|
The one last hurdle was how to strap the batteries down. The box had 6 straps and I figured I could use one per battery. But I didn't take into account the wires and the funky battery caps on the battery. Simply running a strap over them would hold down the caps so you couldn't open them to add water (a necessary maintenance task on flooded cell batteries) and worst case might even break the caps. I thought about just putting wood blocks on the top of the batteries to hold the strap off of the caps, but I was worried that they could slide and that would result in the straps coming loose.
My solution was to create some wood spacing blocks that would slide in between the battery and tabs of the battery tray and run up the side of the battery. At the top, a second piece of block was added to sit atop the battery so the straps would hold the batteries down. This solution will hopefully prevent the batteries from moving side to side as well as allow the straps to hold them down without crushing the battery caps or putting a lot of strain on the cables.
|Modified battery box lid and battery hold down shims|
Of course, constructing these things and then painting them so they might survive a little while in the harsh environment of a boat battery box has taken a lot of extra time. The temperatures have been OK here in Southport, but still not good paint drying temperatures. I let the shims dry for a good day, and they still feel just a bit sticky to the touch but I'm sick of waiting. The batteries are strapped in now and everything is finally back in the locker, and the cockpit is looking a bit more like a cockpit and less like a garage. It has taken me about 5 days to do this battery replacement. I'm still hoping for the day I find a project that doesn't take 10 times longer than I think it should on this boat. But now we seem to have a well functioning battery bank. Only time will tell if going the golf cart battery route will be worth it.