“Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.” – Mark Twain

Battery Upgrade


Last year I completed an upgrade on the electrical distribution and charging system.  What I didn’t realize at the time is I created a ticking time bomb.  Our battery system prior to the upgrade consisted of two 4D Interstate batteries.  One was a year old the other was 4 years old at that time.  They were each on separate banks controlled by the typical 1/2/Both/Off switch.  The 4D’s are spec’d at about 160 amp hours each.  At the end of the upgrade I had the two 4D’s in parallel as the primary bank with a total of 320 amp hours and I was primed to drop in a reserve battery consisting of a Group 24 deep cycle.

Upgraded Battery System in 2013

Upgraded Battery System in 2013

The fatal error I made then was putting two batteries of different age and wear in parallel.  This will cause more stress on the new battery and shorten it’s life.  On top of that I knew that 4Ds were not very good deep cycle batteries despite the manufacture’s claims.  So I did not intend for these batteries to remain when we begin full time cruising.  I wanted to upgrade the batteries to something with better amp hours, that didn’t weigh 140 pounds each and had better true deep cycle performance.  Since I knew I planned to upgrade these I got a little lax in maintenance on them this winter.  Right before we launched I realized they were likely toast due to my neglect.  I confirmed this last week and started planning my upgrade.

Like I do with all things electric, I consulted Maine Sail/Compass Marine.  Based on his research I decided that the best battery bank for us would be to put four 6 volt golf cart batteries in series/parallel.  He had also identified the best bang for your buck 6 volt golf cart batteries as the Duracell ECG2 from Sam’s Club.  These batteries are made by Dekka/East Penn and are the exact same batteries as sold at West Marine for $270 with a different sticker.  The price was much better than West Marine at $112 each plus a $15 core charge each and a $45 Sam’s Club membership.  These batteries set up as two parallel sets of two batteries in series would provide 460 amp hours at 12 volt and be true deep cycle.  Here is a wiring diagram for the new system.


So off I went to Fall River first thing Saturday morning (closest Sam’s Club to me; about a hours drive away).  Purchased my batteries and I was almost ready to start this project.

I stopped at Marine Consignment in Fall River to look for battery boxes.  The existing fiberglass batter box for the 4Ds wasn’t going to work with the new setup.  As luck would have it they had exactly 4 battery boxes that would fit the golf cart batteries.  They were not the same brand but at $4 each as opposed to $10 plus shipping from Defender it was a steal.  I also scored a sweat metal 25mm flare gun I have been looking for at a great price.

Back I went to figure out how to ram 5 batteries into the battery compartment on my boat.  I knew most of the layout work I did last year was going to have to change.  The biggest problem I had was getting the correct battery orientation.  Based on a typically great article from Maine Sail, I found out that batteries are supposed to be situated in a specific direction on sailboats due to heel and exposing the plates.  However, I just could not get all of the batteries in the correct orientation.  In the end, I got 3 of the 4 6 volt batteries in the correct orientation.  Not perfect.

On the two batteries I couldn’t get in perfect orientation I made some adjustments that I hope will be OK in the end.  For the 6 volt, I positioned it so it was on the centerline of the boat.  There should be less affect due to heeling in this location.  On the Group 24, I chose one that has the fills in the center rather than offset and also positioning it as close to the centerline as possible.  Again, this should hopefully partially mitigate the issue.  Also, the Group 24 will not be in use while sailing.  So that should hopefully help as well.  In addition, I plan to add a battery watering system, something like Flow-Rite system.  This will make maintaining the batteries easier and should help reduce the potential for spillage during heel.

IMG_1577 IMG_1578

I again followed Maine Sail’s lead and used pad eyes and nylon straps to secure the batteries.

Another minor flaw in my system is the length between the terminal and the fuse.  According to ABYC standards, this should be 7 inches.  For the primary bank the distance is 8 inches.  Not too much to worry about.  On the reserve bank, the distance is close to 16 inches.  I could fix this by adding an on terminal fuse and I might do that in the future.

To make all of the terminal connections I used Anchor terminal lugs.  I purchased a cheap battery cable crimper from Amazon for $33.  I have to say that I am very impressed with the crimper.  I had previously borrowed a friends FTZ 94284 crimper to make my terminals for the last project but that was not available for this project.  Plus I wanted a way to be able to make terminals on the boat incase I need to sometime in the future.  The cheap crimper worked very well.  I tugged and twisted on the crimped lugs and I couldn’t get them to move.  This crimper is a great addition to my cruising tool set.  I used two different types of marine grade heat shrink on the project.  One was Anchor brand and the other was from Harbor Freight.  To be honest, I could see no difference other than the price.  The Anchor brand was twice as much.  Both were the same thickness (checked with calipers) and both had adhesive.  They shrunk up well and didn’t require excessive heat.

This upgrade ran about $650 including the cost of the crimper.

3 thoughts on “Battery Upgrade

  1. Nice looking work….thanks for posting.

  2. Nice article. Battery orientation is something I never considered and now make perfect sense. I learned something new today.

  3. Good article! The pictures make it very clear. Choosing the right battery type is very important so it is good that you did your research.

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