AGM to LiFePO4; can I replace my starting battery, as well?

[Ded reckoner]

Were you charged a core charge when you bought the 31's? If so, the 27's can be returned to the vendor and you'll get that money back. Otherwise, I think most automotive supply businesses will take old batteries. Else, there's usually a community recycling center within 20-50 miles.

[Cool Hand Luke]

Originally Posted by Ded reckoner

Were you charged a core charge when you bought the 31's? If so, the 27's can be returned to the vendor and you'll get that money back. Otherwise, I think most automotive supply businesses will take old batteries. Else, there's usually a community recycling center within 20-50 miles.

No core charge... I actually bought five (5) of the Lifeline GPL-31XT 12V 125AH Deep Cycle Batteries. Can't wait to test them out... how long should I expect them to stay charged before having to either get shore power or run engine? I only have a fridge running and some fans and water pump... at night, LED lights inside and mast light. 2-4 amps during day; 4-8 amps at night.

[Cool Hand Luke]

4 of them are house batteries... 1 is engine.

So 4*125=500Ah.
500/2=250Ah usable
On average, 4 amps: 250/4=62.5 hours=2.6 days.

Does that make sense?

[cr180]

Originally Posted by Cool Hand Luke

No core charge... I actually bought five (5) of the Lifeline GPL-31XT 12V 125AH Deep Cycle Batteries. Can't wait to test them out... how long should I expect them to stay charged before having to either get shore power or run engine? I only have a fridge running and some fans and water pump... at night, LED lights inside and mast light. 2-4 amps during day; 4-8 amps at night.

Don’t know answer. But if you are aboard, can monitor voltage. Haven’t looked at Lifeline, but Trojan publishes voltage values as a function of state of charge. In the absence of Lifeline data, believe most cruisers would say as a rule of thumb, recharge before get down to 12v.

[jc1409]

Originally Posted by Pete7

...

The Cristec battery charger should be re-wired to only charge the engine start battery. Then the DC>DC charger passes this charge, with limits, to the LFP batteries.
...
Pete

Are there any concerns with placing the battery charger 'behind' the starter battery (in addition to alternator), knowing the bulk of charge will likely be passed over via a DC-DC charger to an LFP house bank? I would expect this will put heavy load on DC - DC charger (heat issue?) while plugged into shore power, but don't know otherwise why this would be a problem.





I'm currently planning to replace an AGM house bank with an LFP bank, and will be leaving the bow thruster and engine start battery connected to the alternator (via a Cristec isolator), and also planning to leave one of my battery chargers (40A) dedicated to charging the bow thruster and starter batteries. I would then add a DC-DC charger to charge from my starter battery over to my LFP bank. Because of relatively low usage from my starter and bow thruster battery, I would expect that the charger and dc-dc charger are primarily pumping current across to by LFP bank (which is also being charged from a separate 40A charger and from a solar MPPT).



thanks,


Jeff