Floating Charging Voltage

[Jim Burrow]

The term "floating charging voltage" is new to me although I have an idea of what it is but what to know for sure.

So what exactly is "floating charging voltage" (assuming with respect to charge controllers - I have a MPP 2424LV) and what is a good rule of them for the seeings. I see in my MPP 2424LV controller/inverter that there is a setting for it.

 

[gnubie]

Float charging is all about keeping batteries with a high self discharge rate fully charged. This is usually lead acid of some variety and prevents damage by having the cells not at fully charged for long periods. The lifepo4 cells / batteries most people use on the forum have very very low self discharge so technically float does not apply to them.

However, in the real world with a DC coupled system you always want the solar array to provide power to the load and that's where float voltages come into play today. It's generally agreed that 3.375V per cell is OK to apply indefinitely to a lifepo4 battery that is in daily use. If you have a 24V lifepo4 that'd mean float at 27.0V.

 

[Jim Burrow]

Thank you gnubie, I was way off what I thought it was. It's clear now to me after your explanation. My battery knowledge goes back 45 years ago (1975) and mostly on Ni-Cd batteries for space applications. I worked in a battery/Solar research lab for one of the big defense companies. But after 45 years, I have forgotten 99.9999% of everything and you guys have all the new knowledge and experience with your solar system.

 

[John Frum]

<snip>I have forgotten 99.9999% of everything and you guys have all the new knowledge and experience with your solar system.</snip>

Just like an engineer to forget 6 sigma.

 

[Jim Burrow]

Just like an engineer to forget 6 sigma.

I think it is in our DNA