New Batteries

Removing old AGM's

On return to Grace ay SMN I was disappointed to find the service battery bank flat. Fully discharged, which is never a good thing for a lead acid battery. With the boat back on shore power we recharged and I did some basic tests. Not good. The boat would not manage more than 6 hours off the mains, sailing with nav systems on. The AGM batteries were goosed.

On charge and discharge the old cells were getting warm. Too warm. Also indicative of serious issues.




Grace has a brilliantly installed Fischer Panda genset and this is configured to come on if the battery voltage falls below 60% charge capacity so we were fine to go anywhere but I like to have proper power available.

My internet cafe in Port Grimaud

Someone told me that "BOAT" actually stands for "Bring Out Another Thousand" and that is pretty
much what we did. It took a bunch of searching on the wifi of my local cafe, round the corner from Grace but we managed to find a set of three MasterVolt AGM 120AH cells with the right terminal config and form factor to fit.

These things are damn heavy. When I got the old ones out it was clear that the cases were warped and heat damaged. This was not a recent issue.

I fitted the new cells taking great care not to short anything. The power available here is pretty scary.

I tested the calibration of the genset and battery charger making sure we had no overcharge issues. I also tweaked the generator's turn on / turn off points.

Its easy to write this in summary but it took me a few hours to learn and troubleshoot these systems. I am now reasonably confident with Grace main power electrics.


We knew the MasterVolt charger/inverter had non working indicator panels both on the remote panel at the nav station and on the unit itself (seen during survey). On speaking to MasterVolt the only way to get this fixed was going to be to return the unit for repair... thats a pretty big strip out job and one that I may take on in the future.. Testing has proved that the unit is working 100% in both charge mode and inverter mode. Someone is home, its just that the lights are not on!

Done and dusted. New cells in.

After the power refit... Grace ran for 4 days off mains with me leaving stuff on 24/7 before the genset kicked in. I love POWER! Fixed.