MAX charge rate for Flooded batteries during winter - low sun...
My battery specs state that max charge rate can be 10$ to 20% of C20. I have a 630 amp hour bank. So MAX DC charge amps can be anywhere from 63 to 126 DC amps.
During the winter there is considerably less sunshine and so I am wondering if it wouldn't hurt to increase the max charge rate from 10% to 15% or even 20% when charging the batteries.
Summer time 10% seems to keep the batteries up fine but now that we are nearing the shortest day of the year and when its cloudy would it make sense to bump up the charge rate especially when charging from the Gen? At 10% max charge rate I am only using about 4000 watts AC from the 13kW gen.
Thanks for any feedback. Always appreciate it.
Comments
Others might disagree but that's what I have read.
I think you will find that as long as you don't exceed 14.4-14.6 volts during the absorption phase, the amperage flowing into the battery will never exceed what the manufacturer lists as the max recomended rate.
Flooded batteries, will generally limit themselves! and they will take less current as they approach a full charge.
Charge controllers are basically voltage regulators. They actually do little other than monitor the voltage when the voltage is less than the absorb cut off you select. Once it reaches that cut off, the charge controller just limits the upper limit of the charging current to the voltage. This keeps the battery from over heating. Some higher end charge controllers can also limit the current flowing into the battery bank. It is also good to have a charge controller which will limit charging and vary the cutoff voltage with a battery temperature sensor.
Once the battery reaches the absorb cutoff, the charge controller limiits the voltage and the current which the battery will absorb will slowly taper off to 1-2% as it reaches fully charged. This is the reason it's usually best to run your generator early in the day and let the solar array(?) top off the battery bank. My older forklift battery takes near 4 hours to top off once it hits abosrb voltage.
Here are basics on battery charging.
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
Your inverter charger? I haven't used one, but didn't know you could set a chare rate. If it has Battery Temperature Sensor, I'd let it go at least to the general capacity of your battery bank.
You say you have a 630 ah battery bank, is this 3 strings of 210 ah golf cart batteries?
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
Unless you are bringing the batteries from zero voltage (such as when new) or the batteries are extremely hot (like arizona ambient temps) then I wouldn't worry about charging current. You will never exceed the max recommended by the manufacturer because the difference between the voltage commanded by the charger and your battery voltage will never be enough.
You can also experiment. Pull the caps and see if you see bubbling. You can feel the batteries to see if they are getting warm/hot.
What issues are you worried about causing?
More or less, for batteries, every 10C/18F increase in temperature over room temperature (25C/77F) causes the battery to "age" 2x faster (while hot)... Don't exceed the mfg. recommended max temperature.
And just make sure that they are not bubbling/gassing excessively (light fizzing OK, rolling bubbling, too much current/too high of charging set point).
-Bill
My 2430 Watt array system collected .05Kwh today.
Snow and ice on the panels. The little Yamaha is gonna be going full-tilt for the next month or so.
I raise my voltage from 58 v to 59.5 for December Jan feb March
I don’t get a lot of solar and it helps the charging .
My charger Max’s out
Even my charge controller dosent put out close to max out put unless I turn the system on mid day .
I’m into absorb at 1000 am so the charge started limiting out put .