Fresh batteries

Since we arrived in Rangiroa, our starter battery was acting out. Then it totally gave up and died. We were firing up the engine with a little portable jumper kits with a lithium battery. We bought this kit in Oregon for our cars. We were happy to see that it easily worked for starting our Diesel engine. When that battery was low, we could always use our house batteries to boost the starter.

But one evening, we came back to the boat and the voltage of our house bank was around 12.2V. We never saw our batteries go that low. There was an issue. One dead battery is not too bad but a few dead batteries, that is a trend. It was time to change the whole bank. Of course, we were in the Tuamotus, where you are happy to find some fresh limes; it would not be easy to get any new ones here. There are some cars so they must be able to get some batteries but how expensive would that be?

Oliver from S/V Tao came to the rescue then next day. With his help, we disconnected all the batteries and tested them one by one with our windlass to see their capacity and voltage pre- and post-load. This technique allowed us to pinpoint the good batteries versus the ones not able to sustain the effort. The starter battery was clearly gone and one to the house batteries was also on its last leg. Another house battery had questionable mark on its side as if it had bled some acid or something of that nature.

As a result, we put back the two defective batteries but we didn’t connect to the system. The questionable one was put in quarantine: we connected it as our starter battery; this way, if it goes bad, it would not bring down the remaining banks. Our re-org’ed house bank was now composed of three batteries. It would be enough for our day-to-day life but it would not be enough to do an overnight passage with the autopilot, without the boost of the engine’s alternator.

One option was to head back to Tahiti and its relative comfort of having a city with facilities nearby. But heading to Tahiti would mean leaving the Tuamotus… probably for good. A better option was to have new batteries delivered to Fakarava. The local Fakarava Yacht Service advises to try via a shop in Raiataia. Their prices were competitive for ok-quality AGM batteries, at least compared to the high quality Varta batteries available in Taina. We went for the cheaper -but still not cheap- option and ordered 5 125Amp.h batteries. The delivery from Raiatai to Fakarava, via Tahiti, was only $30 and delivered in less than a week.

Fast-forwarding to today, the batteries arrived this morning on the Cobia3 and were ready on the dock for pick-up by 7:30am. It was a rainy day so the solar panels were not producing much today. It was perfect to switch the batteries. The old ones came out easily; we’ve done the operation a week or so ago and we knew exactly what to do. As for the new ones, it was more challenging: they are larger and heavier for once but we had to optimize for their geometry. The thing with AGM batteries is that they can operate in any orientation. So it gave us new options to store them in the dedicated housing. After some Tetris, we ended up stacking 4 of them, 2 by 2, in the middle, with the fifth one on the side and, as a bonus, an old one in working condition for the engine. This way, we can use all new batteries for our house bank, i.e. 625 Amp.h compared to 400 in our previous setup. No hardware store to buy more cables here, so we had to optimize for wiring with what we already had. And of course, all this in the aft cabins on a rainy day so no air circulation and sweat level on very high.

Once everything was ready to go, we fired up the engine to recharge a bit. All seems to work so far. We need to get used to how the batteries are behaving with tension, charge and capacity as they seem to have a different profile than the lead acid ones. But we will have some time to get to know them.

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