LiFepo cells from cars

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pcatterall

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Do people re-use cells from scrap cars on their boats, is it worth considering?
Do cars with these cells have to be nurtured in terms of charging like the ones I am reading about here?
Would this mean that you would not put your car 'on charge' overnight as a matter of course but only if you knew you were going to use it the next morning.
It would seem that some owners could ' wear out' their batteries quickly by not understanding the best charging regime?
 
I can’t comment on the reusing car batteries as such but the advice we got for battery care when we bought our e-bikes was to recharge them after every use. The chargers shut down as soon as the batteries are fully charged and the packs retain their charge well. If the batteries are to be left unused for some time (in excess of a couple of months) it is recommended that they are recharged every 6 - 8 weeks.
I think it all comes down to the charging system provided with the vehicle: I know that there is an on board BMS in the battery packs for our bikes as well as a fairly sophisticated charger. Reading the DIY LiFPO thread, it seems that the biggest difficulty lies in sourcing, fitting and monitoring the various bits of the BMS involved, which has to be able to cope with alternator, solar and shore power chargers.
 
pcatterall said:
Do people re-use cells from scrap cars on their boats, is it worth considering?
Do cars with these cells have to be nurtured in terms of charging like the ones I am reading about here?
Would this mean that you would not put your car 'on charge' overnight as a matter of course but only if you knew you were going to use it the next morning.
It would seem that some owners could ' wear out' their batteries quickly by not understanding the best charging regime?
Click to expand...

It's certainly not common practice to use 'second life' EV cells on boats. In fact I've never come across it in my researches but no doubt has been tried. LiFePO4 (LFP) is the particular lithium ion chemistry used for boats. This is less energy dense than the lithium ion technologies that have been used on cars which deliver higher power more quickly, but at the cost of less stability, using additives such as cobalt or manganese. (More recently, I gather, LFP is being reconsidered for vehicles because of lowered cost and new manufacturing technology.) Boats generally have a 'fractional C' use - lower charging and discharging rates - so LFP is very suitable once all the tight charging parameters are taken care of.
 
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pcatterall said:
Do people re-use cells from scrap cars on their boats, is it worth considering?
Do cars with these cells have to be nurtured in terms of charging like the ones I am reading about here?
Would this mean that you would not put your car 'on charge' overnight as a matter of course but only if you knew you were going to use it the next morning.
It would seem that some owners could ' wear out' their batteries quickly by not understanding the best charging regime?
Click to expand...

This Blog Beginning from this Morning - Page 10 | is from a guy who has installed ex-car lithium batteries into his RV to use as house batteries, some interesting info to be found.
 
My lithiums are second hand. New in 2007, and used in a delivery van or similar.

Quite a few canal boaters use second hand batteries from cars. There is a guy somewhere down South who specialises in them. I would have bought from him but he didn't get back to me with a price and a means of getting them to me.

I understand that, once a battery gets below 80% capacity, it is not deemed suitable for use in cars. However, at 80% there is plenty of life left for boating.
 
Richard10002 said:
My lithiums are second hand. New in 2007, and used in a delivery van or similar.

Quite a few canal boaters use second hand batteries from cars. There is a guy somewhere down South who specialises in them. I would have bought from him but he didn't get back to me with a price and a means of getting them to me.

I understand that, once a battery gets below 80% capacity, it is not deemed suitable for use in cars. However, at 80% there is plenty of life left for boating.
Click to expand...

Interesting. What Li chemistry are they, Richard?
 
pcatterall said:
Do people re-use cells from scrap cars on their boats, is it worth considering?
Do cars with these cells have to be nurtured in terms of charging like the ones I am reading about here?
Would this mean that you would not put your car 'on charge' overnight as a matter of course but only if you knew you were going to use it the next morning.
It would seem that some owners could ' wear out' their batteries quickly by not understanding the best charging regime?
Click to expand...
So you mean an EV battery?
The one in my car is not big by car standards but is the equivalent of 3,300 AH at 12V. Or 30 odd batteries.
In my last car I charged it to 100% twice a day and flattened it to 5% or less twice a day for 97,000 miles and the battery state of health was 87% when I sold it. Sounding good as a boat battery so far.
But........
It’s the size of a dining table and a very odd shape sitting under the floor of the car. Plus it’s 400V and if it goes wrong it goes into thermal meltdown. Water can’t put the very hot burn out. So you would lose your boat as a minimum.
On balance not ideal.......,
 
duncan99210 said:
I can’t comment on the reusing car batteries as such but the advice we got for battery care when we bought our e-bikes was to recharge them after every use. The chargers shut down as soon as the batteries are fully charged and the packs retain their charge well. If the batteries are to be left unused for some time (in excess of a couple of months) it is recommended that they are recharged every 6 - 8 weeks.
I think it all comes down to the charging system provided with the vehicle: I know that there is an on board BMS in the battery packs for our bikes as well as a fairly sophisticated charger. Reading the DIY LiFPO thread, it seems that the biggest difficulty lies in sourcing, fitting and monitoring the various bits of the BMS involved, which has to be able to cope with alternator, solar and shore power chargers.
Click to expand...
Current thinking is that it best to store bike batteries not full but at 60-80% charge. If you can, fully charge as you describe but just before you use the battery for a ride rather than immediately after a ride. As post-ride battery state is often in the 60%-80% range this regime can be quite practical.
 
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