Lithium batteries: domestic and cranking?

[TiggerToo]

So, I am looking at the complexities of changing over to Li batteries. Sometime in the future.

I have a Marlec wind generator, with its "regulator". It is an old 913. At some point I will switch to a 1200, which comes with a completely new/different regulator. This needs to be programmed for the type of batteries fitted. At present, I have a "domestic" bank, and a "cranking" battery. The domestics are the ones which go through the most cycles of charge/discharge, and they are the ones I would replace.

PROBLEM: the Marlec guys tell me their regulator can only be programmed for ONE type of battery (Li or Pb); therefore it seems that rules out a mix and match approach. Does anyone here know if it is possible to get a small "cranking"Li battery?

Or should I simply keep the Pb battery connected directly to the alternator but not connect it to the wind generator (anyway, it does not really get discharged at all)?

 

[Ceirwan]

I see no reason to connect the wind generator to your starter battery. The only drain on that should be from starting the engine & it should be recharged from the alternator & possibly your shore charger. No need to connect the wind to it.

 

[Poey50]

Most lithium battery systems on boats retain a lead acid starter battery. There are several advantages in doing so. My advice is to do your research on LFP and come up with a system to aim for well before any investment of new charging equipment. You can make the transition in stages if you have an eye on the end result. So one decision to make early on is whether you charge the LFP house bank direct from the alternator or whether it is charged via the start battery and B2B with the alternator connected only to the start battery. There are pros and cons to each - the B2B route is cheaper and may be fine if you are going to mainly rely on solar. The direct route of alternator to LFP makes use of LFP's remarkable ability to take all the charge you can throw at it, which would destroy a standard alternator so would need an alternator upgrade and external regulator, so £££s. Once that major decision is made then it is easier to decide how to fit in other charging sources. For example a B2B route takes care of the start battery (unless you never use the engine) so your other charge sources can go direct to the LFP.

So read, read, read at this stage - not just the ' it's oh-so-easy brigade' who have used so called drop-in replacements. Here's how I and then others have been tackling it. You will find other sources of information in the opening post. 270ah DIY LiFePO4 build

 

[TiggerToo]

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