Lithium battery project.

[MoominPapa]

5 hours ago, mrsmelly said:

Well basicaly you can have a perfectly good electricity supply from 3/400 squids worth of tried and tested lead acid batteries Or you can be a guinea pig boat and spend 3 or 4k on Lithiums and hope all is ok ?

Buying the kit from Victron gets you closer to 6k, which is far more than I can afford.

 

This project will cost about £400 in bits, and the cells are about £1500 retail, but  hope to do a bit better than that. I'm not expecting to come out ahead financially for about six years, even counting the cost of the large amount of my time it will need at zero.

 

On the other hand, I get to play at a fun project. If it works I can stop stop stressing about my batteries sulphating because it's basically impossible for an off-grid CCer to get them fully charged. I won't even need to try to get them fully charged! I'll never again have to spend time babying a dying set of batteries and jump through hoops to get new ones cheap or buy over priced tat from chandleries. I'll have less generator or engine run time for battery charging. I won't have to top up electrolyte. The space under the floor in the engine room where the LA batteries live at the moment will make a fine new tool store once  the Lithiums are tucked away under the bed.

 

Try new things sometimes, smelly. Live a little!

 

MP.

 

 

 

 

[rusty69]

........and it will make a worthy entry when you are writing your memoirs!

[Phil Ambrose]

Lithium don't have to cost the earth, JohnV and Peterboat have both used pre-owned 

Phil 

[harrybsmith]

https://www.alibaba.com/product-detail/Rechargeable-12v-100ah-lifepo4-battery-for_60215699754.html?spm=a2700.7724838.2017115.44.211c117fVbOfw5&s=p

 

If the cost of batteries for lithium is off putting then you could always go Chinese. While completely different I've been very impressed with cheap LiIon 18650 cells from Chinese manufacturers, and almost all of the safety concerns with (potentially) poor quality cells can be mitigated with thorough control circuitry, much like the OP is doing. 

[peterboat]

On 16/10/2018 at 22:41, Phil Ambrose said:

Lithium don't have to cost the earth, JohnV and Peterboat have both used pre-owned 

Phil 

Yes Phil we have both used high quality valence batteries which went expensive and have a basic BMS in them. We have fitted overcharge undercharged cut off relays to protect them. At the end of the day I am sure MP will have sorted out a good system and enjoyed himself doing so

[Johny London]

Don't be put off by the nay sayers - this is a very interesting project and definitely the future. Do keep us fully updated and good luck!

[reg]

If your playing about then You may be interested in this article I recently came across. 

 

https://www.electricbike.com/how-to-make-lithium-battery-last/

 

Maybe your circuitry can handle some of the issues raised. 

Has some interesting info from the professor who worked on Tesla car batteries and who enabled them to give a 8 year battery life Warrenty

 

Edited October 22, 2018 by reg

[peterboat]

1 hour ago, reg said:

If your playing about then You may be interested in this article I recently came across. 

 

https://www.electricbike.com/how-to-make-lithium-battery-last/

 

Maybe your circuitry can handle some of the issues raised. 

Has some interesting info from the professor who worked on Tesla car batteries and who enabled them to give a 8 year battery life Warrenty

 

Its easy restrict charging to 80% and discharge to No lower then 20% and your battery will last 10k cycles to 80% of capacity

[MoominPapa]

2 hours ago, reg said:

If your playing about then You may be interested in this article I recently came across. 

 

https://www.electricbike.com/how-to-make-lithium-battery-last/

 

Maybe your circuitry can handle some of the issues raised. 

Has some interesting info from the professor who worked on Tesla car batteries and who enabled them to give a 8 year battery life Warrenty

 

The main thing, as Peterboat says, is to avoid high charge state. For boat house batteries, that's fine. It's much easier to avoid spending much time at charge state than it is to have to spend as much time as possible at high charge state, which is what lead-acid needs. 

 

The tricky bit for the computer is to measure charge state. The plan at the moment is to be able to measure cell voltage very accurately and to be able to measure cell current. You can model a cell as an ideal cell with a small resistance in series with it, with both the voltage across the idea cell and the resistance changing slowly as the cell charges and discharges. The computer sees the terminal voltage changing over short periods as the current changes and by doing linear regression, can make an estimate of the resistance and true cell voltage. The true cell voltage gives you an estimate of cell charge state. In addition, by integrating the current, you can estimate how the charge state is changing. For instance if you start with the cell at 50% and remove enough charge to take it to 40% based on the known cell capacity, then that gives you a new estimate to combine with the one you get from measuring the cell voltage. The trick is to use the coulomb counting for accuracy and the cell voltage to avoid the inevitable drift when you integrate the inaccurate current measurement.

 

We called in a Springwood Haven today, who a big Victron dealer. Chatting to the chap there, they're doing good business on the Victron LiFePo4 batteries and controllers. He said the the Jono videos were helping sales a lot.

 

MP.

 

 

 

 

Edited October 22, 2018 by MoominPapa

[Johny London]

Jonos system is way complicated though - real belt and braces stuff. I'd be very interested to hear more details from Peterboat... what exactly you have hooked up for charge/discharge protection. What about rate of charge as well? I'd like to give something similar a go.