Rappey
Well-Known Member
This is the case for many bikes, but possibly due to having auto decompression when starting.
Lithium is purely for weight saving.
bs3911 compared to CCA for starter batteries
- Thread starter geem
- Start date
Lithium is purely for weight saving.
Zing
Well-Known Member
That’s hen’s teeth rare nowadays.
Tranona
Well-Known Member
See post#30. This type of battery is not suitable for engine start, nor is it claimed to be. It is a deep discharge battery for traction purposes or standby applications. Read the article in the link.
Zing
Well-Known Member
It's fine. Read the spec sheet.
geem
Well-Known Member
They are just cells. You then need a bms, high power relay, class t fuses, why bother. There is no upside.
Just found Numax batteries 100 Ah or 80Ah for £113 and £96. No brainer. True drop in replacement. Shop on French side in St M
Zing
Well-Known Member
No, you don't need any of that. Many people don't have it for their existing starter battery. I don't. You do need to charge at the correct voltage though. Not hard and not necessarily expensive.
geem
Well-Known Member
You don't need it for a lead acid starter battery. We are talking lithium
PaulRainbow
Well-Known Member
You need to learn a bit more about batteries, this is just absolute rubbish.
Zing
Well-Known Member
Yes, obviously. A lithium battery as a starter battery doesn’t need all of that. You would charge it in a very tight band of say 70% To 80% capacity where a BMS is not needed. The other things are not needed also. Why would they be?
Zing
Well-Known Member
That‘s an unnecessarily rude, arrogant, patronising and incorrect comment.
I have quite a bit of knowledge and experience with all kinds of batteries. I suspect you are the one with little knowledge on the subject of lithium batteries.
geem
Well-Known Member
So you don't know about class T fuses? Or what happens when a charger fails? They do. I have had two Victron Mppts fail. How do you get your alternator to stop charging the lithium battery when it's at 80% charged? There is a lot more to using lithium safely and reliably than you are suggesting
Tranona
Well-Known Member
I have. To get a 12v pack suitable for direct use in a 12v boat system costs according to your link around £600 with VAT. A similar product without all the hassle of building it up such as this https://www.intellitecmv.com/collections/lithium-batteries/products/lfp-powerbrick-12v- is available off the shelf from a reliable supplier in the UK for £426. This both smaller and lighter and has a built in BMS
Still not recommended for engine start being a deep cycle battery and nearly 3 times the price of my Odyssey which is specifically designed for engine start which is again smaller and only weighs 4kgs more (or 3kgs more than your suggestion.
William_H
Well-Known Member
Just to reiterate with lithium batteries (any sort or size) you must have an accurate way to cut off charge completely at the correct voltage (around 4.1v) for each individual cell. Or risk damaging the cell or having a huge fire. ol'will
PaulRainbow
Well-Known Member
So. you're going to connect four of those Lithium cells together and connect them up without a BMS or anything else ?
Good luck with that, can i interest you in a job lot of alternators ?
PaulRainbow
Well-Known Member
It's not like i do any of this for a day job ?
Oh did this recently on a large cat' that has just sailed half way around the UK
This is also connected to two engines and a 3kw Victron multiplus
PaulRainbow
Well-Known Member
Numax are a good choice, i've used many of them over the years, with no problems. My current boat came with 4 x Numax for the domestic bank and a pair of 105Ah (740CCA) to start a pair of 7 litre diesels, which they do at the touch of a button.
CCA varies between models of the same Ah, for instance, one 105Ah model is 740CCA and another is 800CCA
The CXV24MF at 630CCA would be a good choice, IMO.
Poey50
Well-Known Member
3.65 volts is the the usual recommendation of maximum voltage per cell.
GHA
Well-Known Member
4.1V per cell ???
Best to double check *anything* you read online.....
Doubly so on here. ..
Let Me Google That
Refueler
Well-Known Member
Those LiFePo4 you highlight are 3C max discharge .... that's 40 x 3 = 120A rate .... combining the cells does not in fact increase that as the cells themselves cannot tolerate higher rate. In fact in reality - C rates are often 'optimistic' .......
Zing
Well-Known Member
I can’t see the need for a class T on a lithium battery. They don’t fail to dead short. Why do you suggest it?
Starter circuits are often not wired with fuses, but I think it a good idea to have one and if you have one already, you wouldn’t need another, so no added complexity. They are cheap anyway.
If a charger fails you have a dead battery, just as you do with lead. If it’s ok for lead, it’s no different for lithium and with no significantly greater risk.
I did suggest not using the alternator ideally, or you must then do it with a matched regulator/rectifier to get the ideal charge state. I.e. not full. But there are better ways. A charge controller or better still a battery to battery voltage supply on a timer. Cheap and almost zero risk of overcharge. The battery looked after like that will not need a BMS. Will not need protecting from discharge, will not overcharge, will not go out of balance and will be at least as safe as lead.
I don’t agree there is a lot more than I am saying than this for a starter battery.
That said, it’s easier to stick with what you are used to and unless you enjoy this sort of thing or particularly value lithium’s advantages in this application that I mentioned then I don’t think you should bother.
