Building lithium batteries for my boat – page 6 – the hull truth – boating and fishing forum que gases componen el aire


I spoke to Michael, Whatta Life about the LTO batteries and decided to make some of my own. I found some Honda electric car batteries, that were 24 cells 62V batteries, I reconfigured them into a 12 cell 15.6V battery, 6S2P, they have to be run at about 85% charge to be at 14V.

I was curious to see how they would work starting my Yanmar diesels as that would be a good test. I played around with them at home a bit and got them ready to install in the boat. My sort of finished battery weighs 15lbs and is a 40AH LTO battery. Since it is made up of two groups of 6 cells parralled with each other I can also have a 6S1P battery that is 20AH, with a little change in wiring. After playing with them at home the battery was at 15.2 V a little high for the boat so I connected it to one of my Starboard house bank for about 30 min to bring it down to 13.8V. That house bank is two XS power D3100’s and an Odyssey 34M about 300Ah of batteries. The AGM’s jumped up to 13.8 pretty quickly and then I let is sit for a bit before disconnecting the LTO battery.

I then removed the Odyssey group 31M Port start battery and put the LTO battery in its place. I had not ran the boat in about a month. Was about 70 degrees this morning. So I put the hose in the sea strainer turned on the water, double checked all the voltages and connections. The LTO battery was 13.8V now. I turned the key and the engine started in half a crank as if it was warm! I let it run for a bit to see how the charging would be, my VSR closed and joined the Port house bank (240AH) within a few minutes I was at 14.2V normally wouldn’t be able to get that high at idle so quickly after sitting for a month. I was impressed. After running for about 10 minutes I turned everything off.

Now for the control. Starboard motor was still cold and had not been started in a month either, still hooked up to its own Odyssey 31M sitting at 12.8V. Took 3 slowish cranks to start. I always thought it was the motors that were hard to turn after sitting for more than a week turns out they happily fire up in an instant if spun quickly enough from a 14V battery.

Needless to say I will be making a few more and I will have a bunch of very nice AGM batteries for sale soon.Can you physically make it s 5s battery? That would put the fully charged voltage around the same as a lead acid battery and it would be easier to charge.

I know some people are already thinking "don’t do it your boat will go up in flames " . This wont happen . There are many different lithium chemistry’s , the one used in phones and laptops is lithium cobalt oxide , LiCoO2 .It is uded because it offers very high energy density for its size and weight , the down side is it is somewhat thermally unstable and if damaged , over charged or built improperly it can catch on fire . The Chemistry most boat and car aftermarket batteries use is Lithium Iron Phosphate ,LiFePO4 , this chemistry doesn’t have the high energy density but is much safer .

The type i am using is an industrial / military spec lithium called Lithium Titanate ,LTO . This is the safest of all chemistry’s but is very expensive and therefore not usually used in products for the general public . One of the manufactures was closing a factory and we were able to buy the entire inventory of older stock at a deep discount . ( over 30,000 cells)

so anyway the plan is to build smaller ones for the starboard and center motor and build a big one for the port /house . The small ones will be about 20ah , have about 2000 cca and will weigh 10lbs . they will have 12 , 11ah cells in a 6s2p configuration . the series 24 deka it is replacing is 53lbs.

These will have a usable range of 11.4v to 15.6v . The other cool thing about these is their at rest voltage . a regular 12v battery will be about 14.7 volts while your engine is running after you turn it off it will fall back to about 12.9v and then depending on load will drop into the mid/low 12s . With these when your engine turns off they will stay in the mid 14v range . So your pumps pump more , your stereo puts out more power and your engines restart very fast .