Is my solar controller functioning properly?

[MWybo]

Hello,

Here is the scenario.

Brand new starting battery, charged through bulk (14.5v) to float (13.5v) using my "intelligent" battery charger.
Brand new house battery, charged through bulk (14.5v) to float (13.5v) using my "intelligent" battery charger.

Bring both batteries to the boat and install (same day). Batteries connected throug a Blue Seas ACR. Hook up solar panel (Kyocera 135 watts). (SunSaver 20 amp PWM controller)

No load on house other than DC panel lights and automatic bilge pump switch set to automatic.

Solar charge controller voltage immediately goes to 14.6v. Let it go for a few hours. Motor out of marina to go sailing. Voltmeter reads 14.6 volts with engine running. Cut motor and sail around all day (bright sunny day) with solar charging at 14.5 volts. Only the depth sounder (Raymarine ST40 Depth/Speed) turned on.

Here's the question: Shouldn't the solar controller have dropped the voltage to 13.5 volts at some point given the batteries were fully charged before installation and that the alternator and the solar panels had been charging during the day? My concern is that I will overcharge the batteries. Question 2: Should I stop worrying about it?

Thanks

 

[Maine Sail]

Hello,

Here is the scenario.

Brand new starting battery, charged through bulk (14.5v) to float (13.5v) using my "intelligent" battery charger.
Brand new house battery, charged through bulk (14.5v) to float (13.5v) using my "intelligent" battery charger.

Bring both batteries to the boat and install (same day). Batteries connected throug a Blue Seas ACR. Hook up solar panel (Kyocera 135 watts). (SunSaver 20 amp PWM controller)

No load on house other than DC panel lights and automatic bilge pump switch set to automatic.

Solar charge controller voltage immediately goes to 14.6v. Let it go for a few hours. Motor out of marina to go sailing. Voltmeter reads 14.6 volts with engine running. Cut motor and sail around all day (bright sunny day) with solar charging at 14.5 volts. Only the depth sounder (Raymarine ST40 Depth/Speed) turned on.

Here's the question: Shouldn't the solar controller have dropped the voltage to 13.5 volts at some point given the batteries were fully charged before installation and that the alternator and the solar panels had been charging during the day? My concern is that I will overcharge the batteries. Question 2: Should I stop worrying about it?

Thanks

Less expensive solar controllers don't recognize anything other than voltage and most often use "egg timer" charge programs. It has to first do bulk, then absorption (could be 2 hour time, could be 4 hour) then it will drop to float. Most of these reset each evening when the sun goes down and start all over the next day. Better quality controllers may use a min voltage threshold in order to re-boot bulk & absorption or a PWM % threshold to determine absorb to float.. For example until the controller sees a batt voltage of say 12.6V it will not re-enter bulk/absorb even after the sun goes down..

 

[MWybo]

Thank you.

Mike

 

[MWybo]

Is the Rogue MPT 2024 appropriate for the installation described above or can you recommend other controllers I should be considering.

Thanks again.

Mike

 

[Maine Sail]

I don't really know that your controller is not working properly and I just realized it is a Morningstar unit.. The Morningstar units like yours use the PWM % duty cycle + 1 hour to determine absorption to float. I guess we would need to know the actual SOC and net accepted current at 14.4V, from a strong current source such as your alt, before determining your controller is going to kill your batts.

Do you have an ammeter or battery monitor?

 

[MWybo]

I do not have a battery monitor but am on the verge of purchasing the Balmar SmartGuage from your site (at a very competitive price I might add). I have a Blue Seas 25 amp ammeter on the panel which monitors draw. Could that be placed elsewhere in the circuit to monitor charge.

When I took the batteries off of the intelligent charger the display showed them accepting 0.2 amps. I don't know if that helps or how accurate that charger is. It is not an expensive unit.

You raise an interesting point. The solar controller controls only the solar array which is wired to the house bank. The alternator directly charges the start battery. The relay connects the two batteries so that either charging source will charge both banks given sufficient voltage.

Are suggesting is that the alternator pass through the solar controller or is that not necessary to do the test you are suggesting? By the way, sorry for being such a novice on this, hopefully others will learn from the conversation.

Mike