extra battery

[Derekoak]

On 2nd thoughts I am not sure that a split charge relay is good for lead. Lead needs to be fully recharged ASAP and split charge relays do not do that reliably
How did you work that out, I can assure you my 200amp relay and a thick starter battery cable between starter batts and 2 less batts charges very fast, and with all connected together it acts as a big emergency engine start or jump start for helping others with a flat starter battery.
My van has still got the factory diode block in place which limits charging to 13.7 but once I flick the bypass relay switch I'm at 14.4 full welly.

As I understand it you need short thick cables and sounds as if you have those. Other than that when the engine compartment warms up the alternator backs off the voltage to protect the SB and there is another reason why the LB does not charge 100%. B2b solve these problems, and lithium does not really care to be at 100%

 

[trevskoda]

As I understand it you need short thick cables and sounds as if you have those. Other than that when the engine compartment warms up the alternator backs off the voltage to protect the SB and there is another reason why the LB does not charge 100%. B2b solve these problems, and lithium does not really care to be at 100%

When I'm driving all are linked together and yes once all 3 get near full charge the alt does indeed back off, my voltage sates 14.4 until full and then backs off to 14.2 as the charge cuts back as you say.