# Tri star charge controller showing Absorb' But battery banks volts are at 15.2

Solar Expert Posts: 38
wondering why it' would be in Absorb mode with My battery banks volts being so High ? the tri-star is wired to my bank for Volt's n temp, temp right now is 42* and i checked the banks voltage with a good fluke' and the tri-star meter is right,showing over 15 volt's, I checked the batteries water, and there fine level wise, bubbling very lightly....i checked the tri-stars set points, and there set at 13.5 float and 14.6 absorb...
I don't use the battery bank often, i built it as an emergency back up for power outages... my bank is 6- 6volt golf cart batteries, and i know I'm way under solar panel wise just having 1 250 watt pannel, but I use it just to keep the bank ready to go for an emergency.....So whats your thought's on 15.2 volts..

thank's Bob...

• Solar Expert Posts: 70 ✭✭✭✭
wondering why it' would be in Absorb mode with My battery banks volts being so High ?

Temperature compensation.
Bob, what is the temperature of the battery bank.

And does that controller have an automatic Battery Equalization every month?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 38
thanks for your input''' battery bank is in my garage, the bank temp on the tri-star meter read a temp of 42*degrees.. out side temp at the moment is about 30*ish right now...as for equalization, It is set to manual.. so it wasen't in that mode for sure
42F = 5.6C

Assuming -0.005 volts per C per number of cells, the temperature offset would be:

-0.005 V/C/c * 6 cells * (5.6C battery - 25C standard conditions) = + 0.582 Volt "offset" for charge controller

14.6 volts absorb + 0.582v = 15.183 volts @ 42F charging (absorb) temperature compensation

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 38
Thank's Soo much for explaining it and breaking it down.....this is my first winter with this set up Running, So I kinda freaked when I saw 15.2 in absorb mode, He he..
• Solar Expert Posts: 61
It would only be fair to point out, that a battery going bad will also drive up the voltage reading. I recently changed out what I considered to be a bad Interstate battery for a Deka. I could not get it to float, and (vehicle) the voltage was higher and higher charging as time went on, while the system tried to top it off. I'm now floating in a short time, and running voltages are very reasonable.

It is a consideration, that is all I wanted to point out.