Alexis Bazin, of the TSM research group, helps out Vendée Globe skipper Sébastien Destremau

Alexis Bazin is an assistant engineer in the TSM research group (LHEEA) at Centrale Nantes. As a specialist in a particular model of lithium battery, he was contacted on a matter of urgency by a Vendée Globe Skipper, Sébastien Destremau, to help him pass the endurance test following an unsuccessful initial attempt. Sébastien Destremau's boat is equipped with an electric motor. The Vendée Globe class measurement rules require that competing boats must be able to sail at an average of 5 knots for 5 hours. The endurance test is used to verify this capacity and must be passed successfully in order to compete. To this end, a Vendée Globe official carries out the test with the skipper on the open sea. Alexis was contacted to see if he ascertain what was wrong with two batteries and help ensure that the second attempt was successful. We interviewed Alexis to find out what happened next!

on November 26, 2020

Les batteries du
Les batteries du "Merci"

First of all, what's your role in the TSM research group?
I'm in charge of setting up data acquisition on the engine test benches.
You were contacted on a matter of urgency in mid-October by Sébastien Destremau, skipper of the boat "Merci", at the start of the Vendée Globe to assist with batteries. How were you contacted? Did you know each other before?
I got the first email on Thursday 15 October from Marine Gadel, Sébastien Destremeau's wife, saying that she was looking for a battery (specifically the Valence U27- 12XP) without any mention of the Vendée Globe.We exchange messages and she explains that it's for a Vendée Globe boat. She was looking for a replacement battery, finally located in the Camargue at the battery fitter's. I reply that I'm very familiar with these batteries very well - I am often asked to help with troubleshooting on them - and if needs be, I can help out. On Friday morning, I am at Centrale, in the lab and she contacts me again to say that they can't solve the problem with the batteries and that the endurance test absolutely has to be passed before midnight in order for the boat to compete. I tell her that I can make myself available in the afternoon, that I have 2 batteries and equipment for quick balancing. At 1pm she is in front of my house ready to set off to Les Sables-d'Olonne!
How did the repairs go?
We got to the boat at around 2.30pm where I met Sébastien. He explained how the boat's electric propulsion system works. Initially they had only found one battery to be defective. I replaced it immediately, but when I wanted to charge and start balancing the rest of the pack I realised that a second battery also had internal imbalance problems. Luckily, I had a second battery, this one was already down to 0V which is not good at all for lithium, but there was no choice it needed to be replaced. After 2 hours of optimisation the system was ready, we could embark upon the test. According to my calculations it was going to be very tight to have 5 hours of autonomy at 5 knots. The test started at 6.41pm, at sea, with the Vendée Globe official. I monitored the state of the cells with my computer as well as the different measuring devices on the boat. Following the official's instructions (change of course, speed etc.) we monitored and assessed the state of the batteries for 5 hours, uncertain as to whether or not the boat would pass ...
About an hour before the end of the test I couldn't tell him if we were going to make it or not, it would all depend on the chemistry of the batteries. A few minutes before the end of the test, I asked him to move away from the rocks, the engine could stop at any moment as the cell voltage was starting to get critical. Then I warned that we needed to turn everything off as we risked damaging the batteries by pushing them to their limit. I didn't know what time it was, we looked to the official and he told us that the test was successful! End of the test at 11.42 pm (in other words: five hours and 1 minute!)



Have you kept in touch with the skipper? Can you help remotely if there's another problem with the batteries?
To begin with, I didn't know Sébastien or his team, I hadn't even realised that the Vendée Globe was on this year!  But I know the world of the sailing well, as I have sailed quite a lot with my parents, including a transatlantic sailing race in 2008:
After the test, I went back to the boat each weekend to help out with the final technical preparations (installing the cameras on the mast, software etc.). The atmosphere is really friendly, all the people working on the boat are volunteers. Today, I'm in communication with Sébastien at sea and he regularly asks me questions about the cameras and energy management on board.

What do you take away from this experience?
I am proud that my contribution helped Sébastien to compete and that the adventure will continue for all the those involved. I also got to discover the technology on racing boats and to sail on one. I think this is an experience I will remember for the rest of my life.

The TSM sticker finds a prominent place on board!


The "Merci" leaving port

Published on November 26, 2020 Updated on September 30, 2021