Victron MPPT Float Setting w/Lifeline Battery

[MarkK]

From the Victron manual:

1.6.3. Float stage
During this stage, float voltage is applied to the battery to maintain a fully charged state. When battery voltage drops below 13,2 Volt during at least 1 minute a new charge cycle will be triggered

Lifeline states float is set to 13.3 V at 77 degrees.

Now the question. When temps go up, and voltage from the CC goes down based on the internal temperature sensor, won't this unduly set the charge cycle (bulk, absorb, float) back into action? Or does it matter, as in what does it hurt?

 

[John61CT]

Since the voltages are user adjustable, I imagine the lower "restart cycle" voltage must also adjust, likely relative to float.

And I would trust the Dutch engineers to scale all the setpoints together when temp adjustments are changed.

But contact Victron directly if you want, they are responsive.

 

[tripper]

My Victron float is set at 13.2, it scales with temp, it works exactly as advertised. It wont trigger back into absorb/bulk unless a very large load draws the voltage to less than the setpoint.

 

[jonyjoe303]

Don't worry about lead acid batteries, I float mine at 14.4 volts. It's doubtful if the solar charge controller will absorb the battery for the numerous hours that is required. Maybe the victron is different and actually will absorb for the required 2 or 3 hours. I think all those battery manuals are for home chargers that can be left connected 24/7. With solar you only have maybe 8 hours of sunlight to play with, you need to get the most you can in those hours.

When I monitor my controller it will be in bulk until it reaches 14.4 volts then it goes straight to float. I compensate for this by setting the float to a higher setting. It behaves this way with any lead acid battery I connect to the controller.  By setting the float to the same as absorb voltage, I'm forcing the controller to absorb the battery, instead of stopping the charge at maybe 90 percent. Lead acid you need to charge it to 100 percent everytime.

Something else to pay attention to is the voltage at the controller and the voltage at the battery. At the controller it will read 14.4 volts, but when I put a multimeter on the battery it read 13.9 volts.  
Again I had to compensate by setting the controller absorb voltage to 15 volts, now the battery actually reads 14.4 volts. Everything the controller does is by the reading it is getting, if there is voltage drop, it will get a wrong reading. 

Even floating at the higher voltage, the amps will drop as the battery gets full, it won't overcharge. I done it for years, batteries don't mind sitting all day at the higher voltage but they hate to be undercharged. Thats why I recommend you check the actual battery voltage while charging and make sure its at least the 14.4 volts required. With solar I worry more about undercharging then overcharging.

 

[tx2sturgis]

Don't worry about lead acid batteries, I float mine at 14.4 volts.

{snip}

Even floating at the higher voltage, the amps will drop as the battery gets full, it won't overcharge. I done it for years, batteries don't mind sitting all day at the higher voltage but they hate to be undercharged.

At these settings I must assume that the battery bank is a lot thirstier for distilled water.

 

[Trebor English]

At these settings I must assume that the battery bank is a lot thirstier for distilled water.

My battery uses 20 to 30 ml per cell per month.  When I first got the solar it used almost none, a tenth of that.  Keeping it consistently undercharged saves hundreds of drops of water.  I will keep mine at 14.4 till the sun goes down.

 

[tx2sturgis]

  Keeping it consistently undercharged saves hundreds of drops of water. 

My point, of course, is not the cost of the water drops, but...the cost of neglect at the higher float voltage IF the battery is allowed to dry out.

 

[MarkK]

Something else to pay attention to is the voltage at the controller and the voltage at the battery. At the controller it will read 14.4 volts, but when I put a multimeter on the battery it read 13.9 volts.  
Again I had to compensate by setting the controller absorb voltage to 15 volts, now the battery actually reads 14.4 volts. Everything the controller does is by the reading it is getting, if there is voltage drop, it will get a wrong reading. 

Running my 2-panel portable setup in series and having the SC right by the batteries with temp control built in (Victron) helps not have to try to figure that all out. And then there's the convenience of bluetooth to make absorb and float changes doesn't hurt.