• Ana and John

Batteries failure - what went wrong!

Before moving onto The Dream back in 2017 we had spent a lot of time doing research and arriving at our decision with regards to the new battery system after all the old batteries were dried out and damaged when we bought the boat, presumably from misuse and a failure to maintain them.

We had a good idea as to what we wanted to install and requested assistance from Victron Europe to find the correct installer, based on their recommendation we went with a local Portuguese marine electrician. He was a friendly chap and seemed to know what he was doing at the time when it came to the electrical installation on The Dream we were only just finding our feet and learning about marine electricity.


The local installer set up our new batteries, the charger/inverter and the solar system. At that time we made clear that we wanted a robust system cable of catering for an upgrade of the current solar system of 720 watts flexible panels we had just installed, to up to the 1500 watts capacity our new solar controller (Victron MPPT 150 | 100-TR) could take. Money was not a problem and any additional components required would be promptly purchased.

It was only a few months later we noticed a wood burning smell inside The Dream, a lot of persistence on our investigation and we traced the smell from below the cabin sole/floor and upon inspection, we identified a bolt that the electrician had installed through a timber floor support holding a number of negative cables on one side and many other negative cables on the other side.

This bolt was burning hot and was charring the timber it was secured to. We immediately switched off the solar system, shut down the boats electrical system and contacted the technician, under his advice, we installed a domestic house grade small busbar, dividing the negative feeds from the battery along the busbar rather than securing all that wiring to a single bolt has he had done previously.

This was round one of the electrical sagas and the fact is that now knowing what we now know, we would have been better to not have used him.

After this incident, we installed a smoke detector on The Dream, the burning smell that triggered our investigation was very subtle and it had taken us a couple of days to confirm its origin as the interior of our yacht.


At the end of the 2019 season, we finally upgraded our solar array from the 720 watts flexible panels to a total of 1170 watts high-efficiency rigid panels.

Less than a month after installation of the new panels we found we had a serious problem with the way the batteries were wired and off course these things never happen when we are in the comfort of a marina or in a protected anchorage, these things always happen at high sea.

So there we were mid-sea crossing from Greece to Sicily, about 150 nautical miles from our destination and 75 nautical miles from the closest port or land when the overheating battery alarm sounded. Upon inspection of the batteries, we found that they were all extremely hot, we turned off the solar system and the diesel engine stopping power from being produced and placed an electrical fan to help cool the system. At this point we were not aware of the damage that had been done and the reason for the overheating battery alarm, our initial thoughts were that the alternator controller had failed.

After trying to sail towards our destination for a few hours without satisfactory progress due to the wind on the nose/bow we diverted to the nearest port, to the north away from our destination, this gave us a sail with the winds on the beam.


It would take us almost a day to get to the port and once there we started immediately our inspection. After opening the batteries compartment (not just checking through the inspection opening) we found out that one battery had expanded (this could have led to an explosion at sea), the state of the remaining batteries was then checked by the local marina electrician in Rocella Ionica. They were still showing good numbers but there was now a possibility of a shorter life span after the overheating event.

By the time the local marina electrician arrived our boat to check the batteries we had already downloaded the new Victron wiring guide and identified a few problems, during a difficult conversation with the local Italian marine electrician due to language barriers we understood that in his mind there was nothing wrong with the way the batteries were wired and that the overheating battery was just one of those things of life, "it happened, but it could have not happened", he was insistent that the method of connecting the batteries did not matter.

We didn’t agree with his standing on the subject, in our opinion things don’t just happen without a reason, so we kindly asked him to remove the now confirmed dead barely two-year-old Victron battery and disconnect the solar controller cables. We couldn’t stay in Europe to solve this issue due to the limitations of Schengen time so we needed to carry our journey safely.

We departed soon after, motoring most the way to Siracusa. Always close to shore and constantly checking the batteries temperature with an external independent sensor. We wanted to test the alternator although by now we were sure there wasn’t anything wrong with it and this motor-sail saga proved we were right.

After arriving in Siracusa we departed immediately to Hammamet in Tunisia a further two days sail where we would have plenty of time to study the situation and opportunities to seek the advice from other marine electricians.


For the first two weeks after arriving Tunisia our efforts were to educate ourselves as best possible based on the guidance documents available on VictronConnect website, and support from the online 12-volt community and another marine electrician. We established that the way the batteries and wiring that had been installed by the Victron recommended installer was of poor quality and completely against Victron guidance documents. We had basically been damaging our battery bank since day one, a situation that was emphasised the moment we upgraded the solar system to a high-efficiency array as originally planned.


This was not only a costly lesson but potentially a life-threatening one.

It has shaken profoundly our trust in the so-called professionals, a trust that had been on a few other occasions spilt.


The biggest disappointment for us is that at the time of the installation, in a desire to learn our system we had asked if the points of source power arriving into the battery bank mattered, only to be told that it didn’t matter and that the sources could be connected to any terminal so long as it was positive to positive and negative to negative. We have now learned that it does matter and it matters a lot!


With another steep learning curve still ongoing the first step now that we were docked safely and without overstaying visas concerns was to identify what was wrong with the setup.


The first problem we identified was the crisscross of electricity flowing in the battery bank. There were multiple points of "entry" and “exit" from the battery bank creating huge unbalances in between batteries.

Power was arriving the battery bank directly on battery number 1 via positive cable of the alternator and one of the inverter positive cables, on battery 2 via all negative cables and via the other positive cable of the inverter, on battery 3 via the positive cable of the solar controller, and on battery 4 was the house 12v positive cable supply.

Looking at the crisscross of power flow and different loads of each cable it wasn’t a surprise to find that the battery identified as "dead" was battery number 2, the battery with all negative cables connected directly and the positive cable for the alternator and solar controller on the neighbouring batteries and one of the positive cables of the inverter connected directly.

Keep in mind that we live mostly from our solar array so the battery bank is supplied mostly through the solar controller and occasionally by the alternator when we motor.

To be able to even couple as many cables in one battery as it was the case of battery number 2 the technician had replaced the original battery bolt by a much longer one.

All this was precisely what was indicated on the wiring guidance document from VictronConnect as incorrect and bad practices when installing battery banks.

Another finding that caught our eye immediately, probably due to being architects was the different cable thickness/sections. We could easily identify which were the original battery cables that had been reused and the new ones installed. The reduced section of the new cables was easy to spot, which raised the question why are cables in a similar of condition different capacities?

A quick read of the instruction manual of the Victron inverter (Multiplus) and solar controller (MPPT) we have confirmed that all the new cables installed and sized by the technician were considerably undersized or of non-standard quality and not following even the colour identification codes. Considering that we never put a price tag or limit on the amount of money that could be used to buy the correct material for the installation we couldn’t understand the reason for these choices.

Further study of what were the correct sections, lengths for each cable identified also outstanding fuses and switches. There was simply none installed between the new inverter, solar controller and the battery bank.

The only fuse present associated with the battery bank was the original fuse on the 12v house circuit. There was only one new fuse installed in the entire new setup and was just by the solar array but of incorrect capacity. So oversized that has no use at all.

So our new system installed by a Victron recommended technician was actually posing a high-risk fire due to:


  1. Incorrect wiring scheme, causing unbalances and overloads

  2. Incorrect cables section, causing voltage drops and overloads

  3. Outstanding fuses and switches, making impossible protect the system in case of overloads etc.


Having found all these problems and flaws we started to question other areas of this project and surprise, surprise we identified a situation of overheating terminal ends on the solar array now that we had finally upgraded our panels.

The MC4 connectors that were used to connect our solar panels in parallel were simply melting with the overload!

A full audit of all electrical installations, new ones and original ones was now needed and ongoing to identify potential problems and proceed with the correction of these.

I guess the moral of the story we have found is, don’t necessarily trust your installer, study and know that you could install the system yourself (understand what you have and want) and question anything anyone does to your boat.


At the end of the day, you are the one who must live with the system and manage/ repair it when you are alone at sea!

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