Lead Acid Battery Bank Failure

Our first trip with out new boat was totally exciting. We took her out to a two week vacation on the Balearic Islands.


Apart from just enjoying our first trip on our new boat one of the primary goals was to measure our energy consumption when at anchor and during passage. In order to get accurate numbers, we had to simulate the real world scenarios, and that meant leaving the fridge unit on all the time (during measurement) and also running all instruments, lights and autopilot when cruising.

NOTE: we did this test with the old lead acid battery bank which was on the boat when we bought her. This was prior to installation of the LiFePO4 bank.


The good news is: we got our numbers. The bad: it completely destroyed our battery bank. The batteries did not survive the "abuse" of actually using them the way we intended to live for about one year for a just a few days!


It hit us when we were at anchor on Formentera - a beautiful beach and crystal clear water (but a bit too crowded for our taste). The battery was accepting a huge charge current but dropped voltage immediately once the charging source went away. Voltage went below 12 V a few minutes later. Dead meat.



Luckily, I had just built the Portable Battery Pack for powering the electric outboard for our dinghy (which was working absolutely great for us). I decided to wire the Portable Pack to the boat distribution, effectively replacing the service bank with the 40 Ah pack.

The picture shows how I improvised a connection to the main distribution. In order to prevent the pack from being tossed around in heavy seas I tied it to the bench.

And believe it or not, it worked absolutely great. Sure, we had to be a bit careful with charging, but we were able to just continue with the last five days of our vacation without having to return to the marina early.

This proves that the Battery Pack actually serves the additional purpose of a backup power supply for the boat. I assume we could even start the engine with it, but this would require some provisional rewiring, of course.


Comments: 3 (Discussion closed)
  • #1

    Jonty (Thursday, 09 June 2016 17:18)

    Firstly, great and very informative page.. thanks for taking the effort !

    It is sad to read that your battery bank died, but I presume this was the original lead-acid bank, not the new LiFePO4 bank we have just been reading about? If the latter (I hope not), did you ever understand the root cause of the failure? What specifically killed your bank in such a short time?

  • #2

    Martin Bartosch (Thursday, 09 June 2016 22:49)

    No, our LiFePO4 bank is just fine!

    The bank that died was the old Lead Acid battery bank which came with our boat when we bought her. The bank was four years old and was probably not very well treated by the former owner. See http://www.entropypool.de/2015/05/03/energy-management-part-2-batteries/
    So the failure was more or less expected and did not cause us much grief - we planned to replace the old bank with LiFePO4 anyways.

  • #3

    Jonty (Friday, 10 June 2016 11:39)

    Apologies.. the answer is hidden in plain sight in the title!