Solar charge controller settings?

[brandtj]

Hello,

I have a 150 watt solar panel and this 30 amp charge controller. The charge controller has two battery type settings: lead acid and gel -- I have two AGM batteries. Which setting should I use? Would it be harmful to my batteries in any way using a non AGM specific setting?

Thank you

[steve77]

Originally Posted by brandtj

Hello,

I have a 150 watt solar panel and this 30 amp charge controller. The charge controller has two battery type settings: lead acid and gel -- I have two AGM batteries. Which setting should I use? Would it be harmful to my batteries in any way using a non AGM specific setting?

Thank you

Do you know what your battery manufacturer recommends for float and absorption voltages? Also, do you know what values for absorption and float your controller will regulate the output to when you select gel or lead acid?

Once you know that, you will know which of the two choices is best for your installation. Without knowing more about your installation, I couldn't give any more advice than to do a little internet searching and find out what voltage your controller will output, and what voltage your battery manufacturer recommends.

Cheers!

Steve

[brandtj]

Originally Posted by steve77

Do you know what your battery manufacturer recommends for float and absorption voltages? Also, do you know what values for absorption and float your controller will regulate the output to when you select gel or lead acid?

Once you know that, you will know which of the two choices is best for your installation. Without knowing more about your installation, I couldn't give any more advice than to do a little internet searching and find out what voltage your controller will output, and what voltage your battery manufacturer recommends.

Cheers!

Steve

Hi Steve,

I wasn't able to find specific voltage readings for my batteries (West Marine Group 31 Dual-Purpose AGM Battery, 105 Amp Hours), though according to a general search, it looks like AGM batteries have a typical absorption voltage range from 14.4 to 15.0 volts; and a typical float voltage range from 13.2 to 13.8 volts.

I looked up the manual to my solar charge controller and this is what it reads: PWM constant voltage for Gel Cell battery: 14.1 volts +/-0.4
PWM constant voltage for Lead Acid battery: 14.5 +/-0.4
Float mode voltage: 13.4 +/-0.4.

Due to those readings, it looks like the Lead Acid setting might be closer to the readings of an AGM? If those settings aren't dead on accurate, would I risk any damage to my batteries by testing the lead acid setting?

Thank you

[steve77]

The solar controller's range of +/- 0.4 volts is quite a large range. For my Lifeline AGM batteries the manufacturer gives values of 14.27 and 13.25 Volts for Absorption and Float. These values are at 80 degrees F, and are reduced as the battery temperature increases.

I would go with the Gel value of 14.1 and then measure it with a meter and see what you are actually getting at the battery. I don't think you want to chance 14.5 Volts with another 0.4 Volts possible.

I'm not sure how you will be using your solar panels or if there are other charging devices in play. If the solar is your only way to charge, then you will probably get 10-12 Amps on a sunny day, which might give you 60 Amp-hours per day of charging. With two batteries, each 105 Amp hours capacity, you may never get to Float voltage during normal charging.

Try the lower value (Gel) and see how it does for you.

Cheers!

Steve

[brandtj]

Originally Posted by steve77

The solar controller's range of +/- 0.4 volts is quite a large range. For my Lifeline AGM batteries the manufacturer gives values of 14.27 and 13.25 Volts for Absorption and Float. These values are at 80 degrees F, and are reduced as the battery temperature increases.

I would go with the Gel value of 14.1 and then measure it with a meter and see what you are actually getting at the battery. I don't think you want to chance 14.5 Volts with another 0.4 Volts possible.

I'm not sure how you will be using your solar panels or if there are other charging devices in play. If the solar is your only way to charge, then you will probably get 10-12 Amps on a sunny day, which might give you 60 Amp-hours per day of charging. With two batteries, each 105 Amp hours capacity, you may never get to Float voltage during normal charging.

Try the lower value (Gel) and see how it does for you.

Cheers!

Steve

Great, thanks for the help! I have a charger to top them off in the slip, just want to use the solar to power essential electronics during extended trips. Thanks again!