The Offshore Voyaging Reference Site

While Converting To Lithium

Member Rob sent us the above photo of the very cool (in more ways than one) equipment and battery bay he and his installer built in the aft cabin of his 2002 Beneteau Oceanis 473 while they were changing the boat over to a lithium house (service) bank.

Prior to that change, as is so often the case with productions boats, the batteries were in much less functional positions, too low in the bilge and subject to engine heat.

This brings to mind two thoughts:

  • Lithium battery systems are way more fragile and complicated than lead-acid, so when making the change we want to make sure everything is well away from the engine, well ventilated, and easy to access, as well as laid out in an organized way to make troubleshooting easier.
  • Lithium batteries are about four times lighter and three times smaller than lead acid for a given usable capacity, so improving location and installation is way easier than it would be with lead acid.

Does this make changing to lithium a no-brainer for everyone? No. Here’s how to decide if lithium is right for you.

For those of you who want to nerd-out, Rob was kind enough to provide the following details on the photo:

Equipment from forward to aft in this locker under the starboard quarter berth (forward = bottom of picture):

  • Two Damp Rid containers in process of being changed and secured with cable ties
  • 3 x LiFePO4 batteries secured with truck-style ratchet tie-downs
  • 3 x Blue Sea safety relays
  • 3 x high-capacity fuses
  • At right slightly out of picture on longitudinal bulkhead, MasterBus interfaces
  • Hidden behind bunk crossbeam is the mains 240V residual current device (RCD)
  • Top right is the MV shore-power charger and inverter Mass Combi Pro
  • Top left are the two MV solar controllers
  • Out of picture and the other side of the boat is the MV AlphaPro regulator connected to MV 130A alternator
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John Cobb

Wow…That looks like an installation even the FAA would approve in an airliner!

Stein Varjord

Hi John,

As you say, lithium is much smaller and lighter “for a given usable capacity”. Still, in real life it’s not as straight forward, since all I’ve ever seen do this go for far greater capacity. Most end up with a bank almost the same volume and just a bit lighter. One could argue that the old lead acid house bank was too small, or that our modern boats have become more power hungry, that we read Amp hour ratings as if they were the same as with lead (they’re not), or just that we put in more capacity just because with lithium we actually can. In my opinion, we may benefit from considering a smaller capacity than the max we can fit in, but I understand the wish for more.

Either way, finding a good space for the cells and systems seems to remain a challenge.

Rob Gill

Maybe not the only reason Stein,

We originally bought two x 180 A batteries, though we only needed one to cover our daily usage, and then built in a space for a third – not for capacity reasons, but to provide resiliency.

In the Pacific Islands where we cruise to offshore from NZ there is little chance to get issues resolved with LiFePO4 batteries, so the plan was to be able to have two thirds of our batteries isolate themselves (or be manually isolated), and still be able to operate just fine.

A little later after the install, I was interrogating the BMS display and discovered our batteries were “first charged” three years previously, and MasterVolt hadn’t told me they were old stock. I know that chemically this shouldn’t be any issue as the batteries would have been stored at 50% charge. But it was embarrassing for MV and annoying to me, so after a little discussion they gave us a third battery free of charge, from their older stock.

So we now have 540 A hrs bank, a lead acid equivalent of around 900 A. More capacity than we had before, but not much more, and much less weight and size.

MV had also release a new bigger, brighter & colour version of the BMS display, just after I bought our older monochrome model. So they also upgraded me to the new version FOC. Good recovery from MV in NZ.