From 32V to 36V-A Story of Old Dogs and New Tricks

Recently I had my 32-volt battery charger fail.  With this failure also came critical systems failure such as my bilge pumps.   Those of you with older boats will probably have a 32V system as well.  You would also know that these chargers are VERY expensive.  While I do not believe that the boat would just sink immediately I did not feel I should push the envelope and leave it at the dock for any period in this condition.  After all, I cannot tell you how many times a transient has unplugged my power and left it that way.

I probably need to describe some very particular things about this old boat.  This is a 1986 Hatteras 52C.  For the most part everything has been upgraded to 2023 standards and equipment.  The parts that have not been upgraded have left me with three electrical systems on board-32V, 24V and 12V.  The only items which remained on the 32V were bilge pumps, trim tabs, a few lights, a live well pump and the radar system.  Everything on the list ran well and I even have spares for all of them.  I would pay particular attention if the batteries had to be charged by an 32V alternator and if starters required 32V.  They may also be other sensitive components that could be an issue when switching voltages so run through the systems first.

My first thought was to replace the charger and keep maintaining the 32V.  The boat had survived this long with 3 systems so why not.  When you consider resale maintenance and cost to repair this system I decided to look at other alternatives.  The next would be to switch the remaining system to 24V.  The Cummins engines are 24V and this would work well with Starter and house batteries on the same system since so little was powered by the old 32V system.  That cost added up to be the following estimate:

LED Light Bulbs                                  $75.00

Insta Trim Motor                              $150.00

6 Bilge Pumps                                   $840.00

2 Group 31 Batteries                      $300.00

2 Group 31 Battery Boxes             $200.00

2 ACRs                                               $220.00

4 Fuse Blocks                                    $130.00

1 24V Battery Charger                    $450.00

                TOTAL                                   $2,365.00

This was about double the cost to just buy a new 32V charger and put it in.  But I would still be stuck with three different electrical systems.

 I decided to dig around a little more to see if there was another way to get things done in a safe and reliable manner.  So, four 8V batteries is  32V and 3 12V Batteries is 36V.  I was not sure it would work but then I found one blog post from someone who had also done this successfully.  I decided as an intermediate step to convert to a 36V system and then see if the pumps and everything else would survive.  Also, upon inspection, it was nice to find out that Hatteras had used 4/0 wire for the mains from this 32V system.  Remember that wire size matters for all electrical work on a boat. Always select the appropriate wire size for your needs. This would not only work well with the 36V system, but it would also work well with a 24V conversion due to the short distance. Please note that I had very few things still on my 32V system which makes this much more feasible in both time and money.  The cost would be:

 1 3-Bank Battery Charger            $300.00

3 Group 31 Batteries                      $450.00

Wire and Misc                                 $100.00

                TOTAL                                   $850.00

This was about 1/3 less in cost then buying the charger and way cheaper then the full conversion.  I also looked at this as a partial step in eliminating all of the 32V gear over time.  One thing I did not tell you is that the boat has ALOT of spares.  It seemed to me that if pumps burnt out at a faster rate I could just replace them then go ahead with the full conversion to 24V.

 Once the 32V was replaced with the 36V system I powered the circuits and hoped for the best.  For the last 4 months I have monitored all the components left on the 36V system to make sure there was no early burn out.  To my surprise I only had one item fail to work on the system.  The Radar posted an overvoltage notice within two weeks of the switch.  The radar was a brand-new Garmin open array.  When I looked at the spec the maximum voltage for this radar was 40V.  Since I have two other systems I transferred it to a 12 V system in an adjacent panel. You may think that should still function but note that a 12V battery fully charged is anywhere between 13.1V AND 13.8V.  Triple that and you end up with a max of 41.4V most of the time.  In addition, the voltage drop over that distance with a 4/0 wire is not significant enough to keep the voltage down.  To this date all the pumps seem to work fine.  This turned out to be the best solution for my boat in the long run since I know have time to complete the entire conversion.

 Please remember one thing-Try new things but also be safe. Any electrical work on a boat can have consequences if not done right. If you are not absolutely confident in your ability I am sure there is someone on your dock that would be glad to help. Be Safe!

 UPDATE-Almost 9 months later and I can happily report there have been no failures or other electrical problems associated with this 36V system. It is still my full intension to convert this system to 24V down the line but it is about 4th on my list of TO-DOs.