Kid Controller Continuous BULKMPPT Mode

[dmkkeng]

As a back-up to shore power I left my solar system on for the winter months. The AC charger typically operates in the Float mode of operation as there is very little draw on the batteries during the winter months. While on the boat I noticed the solar system comes on for 4+ hours on a sunny day, typically displaying something like 2.7A BULKMPPT 14.8V Solar 38W. The solar system never drops down into the Float mode of operation. When the solar system is on you can clearly hear the fluid boiling in the battery cells. This first came to my attention when checking the fluid levels in the battery cells and finding them all to be low. My concern is the solar system is overcharging the batteries causing the low fluid levels. I have a couple of questions as follows;

1. Is it a bad idea to run the solar system during the winter?
2. Why is the Kid Controller not going into the Float mode of operation?

The Kid Controller has been in service for 3-5 years, other than some initial set-up problems I haven't had any problems with the solar system (12V system, 4-100W panels, 6-Rolls 6FS220 batteries, Whizbang jr).

[boB]

What you are most likely seeing is the timed Absorb charge every day for whatever that time is.  Usually a couple of hours.  That would be normal.

The batteries will need a good Absorb (raised voltage) and timed at a couple hours at least once in a while...  Maybe once a week or two.

And this is why you have to check and periodically replenish the electrolyte (water) once in a while.  In the process of this Absorb maintenance cycle, it boils some of that water away.

It is nice to be able to skip bulk/absorb days because of what you are seeing.  Absorb cycles don't usually have to happen every single day.

Ending-Amps are also nice to have if you have something like the Whizbang Junior watching the current into and out of the battery itself to end the absorb cycle and go to float if the battery doesn't need to sit there for a long time... BUT, that doesn't force the charger to do a timed absorb for a couple/few hours every week or two.  The Ending amps setting along with a forced timed absorb every so often would be the ultimate.

For now, just watch the water levels.  The batteries should be OK.  At least they won't sulfate due to lack of absorb cycles.

Oh, almost forgot...  Why isn't it going to Float ?  I'm not sure but the days are getting shorter up here in the northern hemisphere so if that is where you are, maybe that is it ?  How long is the absorb timer set for ?

[dmkkeng]

I don't remember setting the absorb timer so likely it still is the default setting. Ends amps is set to 1.5% (size of battery bank is 660 ah) so approximately 9.9 amps. I was reading the manual and in Bulk mode the controller is trying to put as much current as possible to charge the batteries to the Absorb set point which is 15V. Perhaps there is not sufficient solar power to get the batteries to this point so it remains in Bulk mode - I'm starting to think there is just enough sun to get the system operational however not enough to get the controller to go from Bulk to Absorb to Float mode, perhaps this happened frequently enough early in the season to deplete the fluids in the battery. Going forward there isn't much sunshine in the long term forecast so hard to say if this will continue to be an issue.

The battery cells were topped up the previous month so that seems excessive in terms of fluid depletion?   

If the controller cannot get to the Absorb point voltage then it seems to me the Absorb timer doesn't come into play?

In the interim I shut down the solar system as I wanted to make 100% sure the depletion of fluid levels was caused by the solar system and not the AC charger.

I could change some of the controller settings however I'm concerned those changes may affect the operation of the solar system during the sailing months where the solar system is my primary source of charging the batteries.

[boB]

You will want to make sure that the batteries are getting some absorb time.  An accumulated X hours per week or two might even be OK ?

If it never or rarely gets to Absorb for a while, then there may just not be enough sun or PV array wattage for that battery bank.

If those batteries go too long without an absorb cycle, they won't be happy.  Maybe one or two or maybe all of them depending
on the degree of sulfation.

Right that if the battery voltage doesn't get to the absorb V setting, then the absorb timer counter won't count down towards zero.
But it can go in and out of absorb several times a day if they need charging and you have clouds rolling in and out.

Or, maybe they're all good !

Let us know how it's going.

[Resthome]

Looks like you don’t have enough panels to charge your batteries during the short sun days of winter. Sound like you have 6ea-6V batteries configured for 12V for 660AH. That is a hard battery configuration to charge all batteries equally. You don’t say how you have the panels configured but the most you will get is approx 80% of the rated wattage at 25C or around 320W with peak sun.  Your not getting any where close to that at 38W. So need to know how you have your panels wired and all the specs of those panels.

I’m not a Kid expert so don’t know if it has the ability to skip days like the Classic as boB mentioned. But your problem is you not reaching the Absorb set point voltage as you have figured out.

[dmkkeng]

I have (4) 100W flexible panels on the top of my cockpit closure, the (2) panels on the starboard side are in series as are the (2) panels on the port side, the port and starboard arrays are in parallel - so I have a series/ parallel configuration. You are correct on peak power, the highest power coming from the array, that I have recorded, is 315W. I can't find the specs on the panels. There is no doubt that 38W is not sufficient to get the batteries into Absorb mode - I'm not sure why the controller gets stuck in this mode as the batteries are already fully charged by the AC charger, there is a shunt connected to the Kid controller with an end amps parameter of 1.5%, however it appears that parameter does not override/ interrupt the Bulk/ Absorb cycle. I believe this may be an issue with the Kid Controller with respect to how it is set-up and/or functions that is caused by the lack of sun this time of year.

[Resthome]

Don’t know for sure but I suppect end amps works from the absorb stage. I was trying to determine what the VOC and the Vmp of the panels where. I would set the absorb voltage lower to see if that helps. The Classic CC has a feature that if it sees what it thinks is another charging source it can go to the Resting stage. Sorry I’m just not that farmilar with the Kid software I am a Classic guy.

I would also just try removing the AC charger. Is the AC charger a 3 stage charger or more like a car battery charger.

[dmkkeng]

I looked through my notes and had written down VMP of 35.6V and a VOC of 43.2V, keep in mind this is for the entire array so the actual per panel spec would be 1/2 of that. Yes it appears that end amps works from the absorb stage. The AC charger is a 3 stage charger - it is working as it should. It is definitely the solar system that is overcharging the batteries. I think the only solution, as you mentioned, is to lower the Absorb voltage. The manufacturer recommended setting is 15V, that does seem high, perhaps I will lower it for the winter season and observe what happens. Thanks for your help!