To charge or not to charge

[SEMPERAVANTI41]

I have converted my house batteries to 600 ah of Lithium, and they are working well. The Li batteries are either charged from the AC (Cristec) charger or from a Renergy 60 amp 12 v to 12 v charger connected to my start battery. The Renology charger is set to Lithium charging at 14.6 v (recommended charging v), while the Cristec charger is set to a maximum voltage of 14.4 v.. The Renergy charger is wired to only operate when the engine driven alternator is producing voltage. I could also wire the Renergy charger to operate when the Cristec charger is producing voltage. Would this be a good idea?

 

[Davidasailor26]

I wouldn’t set up the DC-DC to charge the house bank when the shore charger is on. I don’t know your Cristec output and whether it’s one bank or two, but either way I don’t think any good can come from having the DC-DC come on when the shore charger is.

If the shore charger is one bank then the DC-DC will be trying to charge the house bank from a start battery that itself isn’t being charged. That will quickly deplete the start bank.

If the Cristec is wired to both banks then when the DC-DC comes on it will present an extra load on the start bank side of the Cristec, so it will output more on that side, reducing the amount available to the house side. The DC-DC will have some amount of inefficiency, so some percentage of the current that the Cristec puts into the start bank be wasted rather than put into the house bank.

 

[mermike]

Where did the recommended charging voltage of 14.6V come from? That's pretty high for most LFP batteries. Most look for 14.1v or thereabouts. Battleborn is the only one that's in that range, at 14.5V.