Should You Buy a Boat Lifepo4 Battery Charger without a Separate Battery Voltage Sense Input Wire?

[Danny]

Short answer : Best Practice is to have a separate voltage sense wire on your chargers (solar and shore) and voltage regulator. Read this https://marinehowto.com/alternators-voltage-sensing/

Lifepo4 has a really flat charge curve and then it climbs rapidly. Having your charger know the battery voltage is really important so you don't over charge your batteries. Also sometimes we run multiple solar charge controllers and they read each other's voltage. In doing my project, I have learned the value in having charge controllers that are capable of reading the Lifepo4 battery terminal voltage on a separate pos and negative input wires running from the battery to the charger without any load on the wire. The Victron MPPT, Balmar 614 and the Sterlining B2B BB1260 all have this capability so the charger can compensate for voltage drop in the main charging wire. I was looking at the new cool Renology DC DC charger and I noticed it has a voltage sense input but no body talks about hooking one of these wires up? Strange I think. Here is a video where I considered the separate voltage sense wire when I was wiring my boat.

 

[SolarMuppet]

Voltage sense wires are most useful to prevent under charging rather than overcharging. They prevent the charger cutting out prematurely when it sees a higher voltage than that in the actual battery terminals. On lead Acid that is a serious handicap and can cause battery sulphation if the charger goes into float before they are full, on Lithium it is more likely to simply lead to batteries being taken to a lower state of charge on the charge curve before cutout.