LIFEPO4 for starting

[witzgall]

I have been thinking about this issue for a few years. Headway has been making cylinderical LIFEPO4 cells for awhile. They have some new cells that will do 10c continuous:

HEADWAY Lithium LiFePO4 38120HP | LiFePO4 Cells, LiFePO4 Battery Packs for EV, Lithium Iron Phosphate Battery

We have a 24v starter, so 8 of these would make a very small, light starter battery.

Chris

[bill good]

Chris, I used 8 X 12A/H headways 12V for 3.5kgs. My recommendation for the ultracaps is one of low temp operation consideration. I can see an over time return on investment. In my case, I have no desire to move out of warm tropical waters!! So lifepo4 cells which has vertually the same internal Z as the caps will do my job. (I did start my truck engine with 4 of these cells which was impressive).

[dansken]

Bill good, I will check out the ultracaps, thanks. Regarding the temperature and LIFEPO4: from the spec sheet it says discharge down to -20 oC. that would not be a problem as the temp in the bottom of the boat seldom gets below freezing (as long as the sea water is still fluid ;o)
Charging should however not take place below 0 C. but I guess the engine, once running, soon will heat up things and charging could be postponed until that has happened.

[ardoin]

Danskin,
I ended up with 200 Ah cause I was planning on using 1200 Ah for the main bank when I found the starting bank died. So I salvaged a few cells to replace a 4D with LiPO4 cells for about the same Ah. My gen set also starts from the same bank. While the Yanmar starts instantly, the Northernlights gen set takes a bit of cranking.
The 200 Ah I installed takes about these same pace as the 195Ah AGM it replaced. I had to move the Hitachi 55Amp alt off this bank cause it was trying to overcharge the bank. Now I have both the 100 Amp and 55 Amp alt on the house bank and connect the two banks with the switch while charing, only when the starting bank needs a boost.
My only caution with smaller banks, I had my internally regulated Hitachi overcharging my 200 Ah bank. You many have to adjust your alt if it is dedicated to the engine bank.

[dansken]

Thank for the info Ardoin. My housebank is 24 v, charged from a double alterternator intall. the starting batt (12 v) is charged from the house bank through a charger when needed - the charging characteristics can be set to suit LIFEPO4 requirements.

I see that the limitations of LIFEPO4s in cold weather are beeing discussed on the "big LIFEPO4 thread", and also elsewhere on the nett. Some of the the interventions think they are OK as starting batts (motorcyckles, cars) .......

[d design]

I have used a 3s 50c 2000mah lipo battery to sart a car. Check out youtube.

[deckofficer]

Originally Posted by d design

I have used a 3s 50c 2000mah lipo battery to sart a car. Check out youtube.

What has been your negative experiences with LiFePO4 cells. On the poll you voted using Li was a mistake and you were going back to lead.

[hellosailor]

"to sart a car."
Folks were selling bricks of NiCd AA cells to do that ten years ago. This year it is a "can" battery instead, no idea what's inside it but at $30 it can't be terribly exotic either. Now, if those little packages could totally replace the car battery, for everyday use, that would be newsworthy.

[bill good]

Originally Posted by dansken

- the charging characteristics can be set to suit LIFEPO4 requirements.......

Sounds good but ensure there is a "cut off" phase to disconnect the battery from charge source at the end of the charge cycle.

[d design]

Originally Posted by deckofficer

What has been your negative experiences with LiFePO4 cells. On the poll you voted using Li was a mistake and you were going back to lead.

I had a 2s 2ah LiFepo4 catch fire in my rc sailboat ruining the electronics. Was likely due to corrosion from salt water

[deckofficer]

Originally Posted by d design

I had a 2s 2ah LiFepo4 catch fire in my rc sailboat ruining the electronics. Was likely due to corrosion from salt water

I guess I wasn't as explicit as I should have been in the LiFePO4 poll. I did say for folks to vote if they have used the cells in a house bank, propulsion or both but didn't stipulate it should be with a full size boat, not a RC model.