(Yet) Another Lithium Conundrum (or two)

[Frayed Knot]

Quite a specific question as I’ve now decided for certain to change my tired la bank for lifepo. All wiring and ancillaries now decided upon (with helpful advice from this forum) I now just have to decide which battery or batteries to buy.
The question really: do I need batteries with built in heaters?
We live aboard and cruise throughout the summer when hopefully this would not be an issue but we also spend a good amount of time on board through the winter - marina based and on shore power. SE England so the temperature on board very rarely drops below zero and the batteries are below the waterline, close to the hull.
My other area of indecision is, single battery or multiple in series. I want around 400ah which, with 4 x 100ah would be a tight squeeze with the additional cabling and switches etc. whereas a 460ah unit would fit nicely and also be far simpler to install. There are 200ah ish batteries available but there’s no way I can fit two of them into the available space.
As ever; advice/personal experience welcome!

 

[Trident]

My view is always more than one battery - if the BMS goes tits up then you still have some power in the other one (or ones)
For 400 ash AH you could get two 200ah from say Renogy or Fogstar but if they wont fit in the space it does seem excessive to run 4 lots of 100 with all the wiring and fusing extras needed. Maybe look at 2X 280ah sets of EVE cells with JK BMS - certainly smaller than most cased versions and a lot cheaper - around £1000 for 560ah total.

If you buy ready made batteries then the heat pads are not a bad idea unless you leave them off charge over winter or want to keep a very careful eye. Or leave a tube heater on. WIth the good programable BMS like JK you can simply turn off charge input below say 5 degrees so nothing to worry about. As LFP likes to be stored at half charge or so, turning off the charging systems you have for winter may be simpler either way if the boat is not in use. If it is in use then you will be able provide heat if needed.

I ran up to 8 Renogy 100ah for a couple of years but now have 2 packs of EVE cells at 314 ah each. They actually cost less for double the power, weigh less and take up less space - and took only a couple of hours to put together so definitely the best way to go if you're confident with simple wiring

 

[PaulRainbow]

Quite a specific question as I’ve now decided for certain to change my tired la bank for lifepo. All wiring and ancillaries now decided upon (with helpful advice from this forum) I now just have to decide which battery or batteries to buy.
The question really: do I need batteries with built in heaters?
We live aboard and cruise throughout the summer when hopefully this would not be an issue but we also spend a good amount of time on board through the winter - marina based and on shore power. SE England so the temperature on board very rarely drops below zero and the batteries are below the waterline, close to the hull.

Given the above, i'd say no need for heating.

My other area of indecision is, single battery or multiple in series. I want around 400ah which, with 4 x 100ah would be a tight squeeze with the additional cabling and switches etc. whereas a 460ah unit would fit nicely and also be far simpler to install. There are 200ah ish batteries available but there’s no way I can fit two of them into the available space.
As ever; advice/personal experience welcome!

Don't buy drop-ins, assemble your own from good quality cells and use an equally good quality BMS. The cells are nominally 3.2v so you'd need a combination of series and parallel connections. 4 cells connected in series makes a 12v battery, 2 of those in parallel doubles the capacity. So 4 x 280ah cells in series gives you a 280ah 12v battery, times 2 gives you 560ah @ 12v. The cells are not that big, a set of 4 is similar in size to a 100ah LA battery.

 

[Frayed Knot]

Thanks for those suggestions and thoughts, Trident and Paul.
The thought of building my own bank is not something I’d considered - I fear you may be overestimating my competence and confidence
I also wonder about insurance implications - one reason I’ve been looking at only CE approved or similar.

 

[Trident]

Thanks for those suggestions and thoughts, Trident and Paul.
The thought of building my own bank is not something I’d considered - I fear you may be overestimating my competence and confidence
I also wonder about insurance implications - one reason I’ve been looking at only CE approved or similar.

Worth noting if allowed under forum rules - as I have no connection with Fogstar and am just a happy customer - that they have a black Friday deal today with 20% off - these are very good batteries with good BMS and well priced

 

[Sea Change]

Thanks for those suggestions and thoughts, Trident and Paul.
The thought of building my own bank is not something I’d considered - I fear you may be overestimating my competence and confidence
I also wonder about insurance implications - one reason I’ve been looking at only CE approved or similar.

Assembling a set of cells and a BMS is a bit like meccano- it's just nuts and bolts. It's helpful if you can make up crimps too.
You do have to treat the components with respect, but it's not really that different to working with lead acid- avoid dead shorts! It's a good idea to use a small spanner wrapped in tape, that is physically unable to bridge between terminals if dropped.

The current pick of the bunch BMS seems to be the JK, with an active balance circuit. When I built my batteries this wasn't available and I had to balance the cells before assembly. Took a few days on low power using a £40 adjustable power supply.
For crimping, I bought a £25 hydraulic set and it's been perfectly fine. Those were the only extra tools required.

The advantages of building your own area:
- cheaper
- wider choice of components to suit your needs
- better cooling for the BMS
- BMS can easily be replaced if it dies
- much more compact
- BMS can be disconnected for storage

On the last point, I just started using my batteries after seven months in storage. They were sitting at nice healthy voltages. Unfortunately I can't remember exactly what I left them at but when I started them up again they were at about 47%. All you have to do is unplug a lead from the BMS and you have zero parasitic load.

 

[Frayed Knot]

Worth noting if allowed under forum rules - as I have no connection with Fogstar and am just a happy customer - that they have a black Friday deal today with 20% off - these are very good batteries with good BMS and well priced

Thanks for that heads-up. I was almost decided on the Fogstar 460 but have reconsidered the space and with a little carpentry work I can fit 2 x 230s which, at the same price now that I would have paid for the 460, I’ve just ordered.

 

[Frayed Knot]

Assembling a set of cells and a BMS is a bit like meccano- it's just nuts and bolts. It's helpful if you can make up crimps too.
You do have to treat the components with respect, but it's not really that different to working with lead acid- avoid dead shorts! It's a good idea to use a small spanner wrapped in tape, that is physically unable to bridge between terminals if dropped.

The current pick of the bunch BMS seems to be the JK, with an active balance circuit. When I built my batteries this wasn't available and I had to balance the cells before assembly. Took a few days on low power using a £40 adjustable power supply.
For crimping, I bought a £25 hydraulic set and it's been perfectly fine. Those were the only extra tools required.

The advantages of building your own area:
- cheaper
- wider choice of components to suit your needs
- better cooling for the BMS
- BMS can easily be replaced if it dies
- much more compact
- BMS can be disconnected for storage

On the last point, I just started using my batteries after seven months in storage. They were sitting at nice healthy voltages. Unfortunately I can't remember exactly what I left them at but when I started them up again they were at about 47%. All you have to do is unplug a lead from the BMS and you have zero parasitic load.

I appreciate the advice and I had watched a few YouTube video tutorials about it but although it does seem quite straightforward I just don’t have the electrical experience to be comfortable living (and sleeping) with the finished product!
I’m actually a carpenter - if I could make them from wood it’d be a different matter

 

[Sea Change]

I appreciate the advice and I had watched a few YouTube video tutorials about it but although it does seem quite straightforward I just don’t have the electrical experience to be comfortable living (and sleeping) with the finished product!
I’m actually a carpenter - if I could make them from wood it’d be a different matter

You can make the compression plates from wood