Battery charging

gav

hi everyone I have 2 volt batteries in series for 12 volt which we will be turning 24 volt but my query is what is the max boost rate charge rate , absorption rate and float rate I have a picture of the charger settings thanks

Estragon

As a rule, you'd want to start out with the recommended voltages, etc given by the battery maker for your specific model of battery. Depending on your actual use pattern, these may need to be tweaked, but best to start with recommended values.

MrM1

What is the source for battery charging?  Solar, Wind, Other?   If solar,  while it is good to start with the factory recommendations for the specific battery,  the numbers used by the battery manufacture are usually set with  an AC charger in mind that can run all day and all night if needed.  With solar you only have a limited time to get the batteries back to fully charged each day. 

So starting with the recommended settings from the battery manufacture for Bulk (aka Boost)  / Absorb / Float,  do this a few times in good solar conditions,  and then using a good temperature compensated hydrometer test the Specific Gravity of the batteries at the end of the charge cycle when the charge controller indicates 100%.  If you have not reached 100% in the SG reading,  on the next day increase the Bulk and Absorb voltage settings, recharge and test the SG again.  Keep increasing the voltage of Bulk and Absorb until batteries get fully charged with available sun light and you find that sweet spot.  Obviously this will change depending on the season.

You are  going to need to figure out which charge setting the CC uses first.   This would be the Constant Current setting.  Usually referred to as Bulk.  Then most chargers Switch to Constant Voltage for the last 80-90% of charge known as Absorb.  From a quick read of that picture I am not sure which is which.  But I would suspect in a Solar situation you might need as a starting point:

Bulk (which is actually the Bulk switch over / cross over voltage to absorb) set to - 2.54v per cell

Absorb set to the same - 2.54v per cell

And by the time this is done depending on where you are located and how many solar panels you have you may or may not reach fully charge.  So test test test.

And then set float to either 2.25v per cell IF the batteries reach fully charge before the sun is gone  ... OR ... you may need to set float to the same as absorb if you just do not have enough Sun / Panels to fully charge the batteries very day. 

But because we are limited to the number of sun hours we have per day,  Some times you just have to set the charger settings to "Maximum Smoke" to get the batteries anywhere near fully charged.   And remember,  the higher you set the charge voltage,  the more  distilled water you will use per cell - so keep an eye on those water levels. 

gav

I have tubular gel batteries so I am not able to do a SG test. As we already had 12 volt inverters we have the battery bank set up as 12volt system. The amp hour size is 3600 ( this will lower to 1800 when we change to a 24 volts system) I have 24 solar panels, 250 watt. I can only run 4 of them for now until the 2nd and 3rd Outback’s arrive. (We have the Outback Flexmeax 80) Then I will run 12 of them until I change to 24volt with the purchase of a new inverter. We only need to run the fridge and deep freezer for now (200watts each) We also charge with a generator at night. 

To get the most out of the four panels, should I increase the absorb time limit on the Outback? According to the chart the full charge absorption time can be up to 20hrs. 

Thanks

Estragon

With gel batteries I highly recommend checking the manufacture website for charging voltages for your specific battery. Some gel type batteries can be irreparably damaged if charged a too high voltage.

Absorb takes a diminishing amount of current at a constant voltage. With limited panels, you may want to bulk charge with the generator, and let solar finish when current drops off to what the panels can support. Absorb should be terminated when charging current drops off to ~1-2% of amp-hour capacity, so around 20-25a for an 1800ah bank (40-50 for a 3600ah bank)..