Solar Charge Controller Confusion

[Mike Sibley]

I have been looking for a PWM solar charge controller to put between a 200W solar array and a 200A AGM battery bank. I thought it would be easy. First I went to the West Advisor in the 2014 West Marine catalog, which indicates that AGM batteries should have set points of 14.7V for the Absorption phase and 13.6V for the float phase. Then I started looking for a controller that was close to these values. I looked at Morningstar, Blue Sky, Go Power, Xantrex and Renogy controllers. The absorption rates for AGM batteries varied from 14.1V (Morningstar) to 14.4V (all of the others). The biggest variation, however, was for the float rate which varied between 13.2V (Blue Sky) to 13.8V (Renogy). I am left with the conclusion that battery charging is a very imprecise science. I know that some of the controllers let you change the set points for absorption and float phases, but then I have to wonder what the appropriate rates are. If the people who make charge controllers can't figure it out, where does that leave me?

[Ex-Calif]

There are certainly anomalies.

Did you decide on a controller? I'm going with Morningstar PWM to control 100-140W in two panels & 210-200 a/h AGM bank.

[MarkJ]

I thought you could adjust them?

[Jimbo485]

Yes, some are adjustable,

[noelex 77]

Controllers with variable charge parameters are much better.
Use what your battery manufacturer recommends.
There are differences between different batteries of the same chemistry.

The generic settings for controllers are a compromise. They also often assume that there is no battery temperature compensation (because this is an option) so lower the voltage set points to play it safe.
Battery charge algorithms for solar are also a compromise between charging aggressively and charging slowly therefore having a lower SOC. Both of these are not good for the batteries. By adjusting your set points you can achieve the best compromise between these options (more aggressive is usually better for boats especially if you are using the boat over winter)

[Ex-Calif]

You need to get the manuals and read the fine print. here are a couple of snips from the Sunsaver Duo PWM which I am settling on.

Note that to set custom points you need to get a software solution and I presume cable adapter) form Morningstar.

If you want standard profiles you can do it with DIP switching.

[Mike Sibley]

The idea of getting an adjustable controller and and using the set points recommended by the battery manufacturer is the obvious solution. Does anybody know who makes the AGM batteries sold by West Marine? I can find no information in the West Marine catalog or on their web site that says anything about charging set points.

[Maine Sail]

Originally Posted by Mike Sibley

The idea of getting an adjustable controller and and using the set points recommended by the battery manufacturer is the obvious solution. Does anybody know who makes the AGM batteries sold by West Marine? I can find no information in the West Marine catalog or on their web site that says anything about charging set points.

They are made by Deka / East Penn..

Deka batteries are temp corrected at 68F not the industry norm of 77-80F. So any time the battery is above 68F temp compensation needs to begin reducing voltage. You would probably be best to set it at 14.2V or 14.3V, as opposed to 14.4V, if using a controller without direct battery temp sensing.

[Mike Sibley]

I called customer service at Deca Battery (Makes the West Marine AGM batteries) and they recommended charging voltage of 14.4V to 14.6V for the bulk/absorption stage and 13.5V for the float stage, assuming 77F. Based on this, the Morningstar controllers seem very conservative on the bulk charge rate and "aggressive" on the float rate. The rest of the controllers looked at seem "in the ballpark," except that the Renogy and Go Power controllers, which also seem a little high on the float rate. Of course, other battery makers might have different set points. In any case, I will probably go with the Blue Sky charge controller, which is adjustable - and I have always been happy with Blue Sky products.

[sstuller]

Controller confusion is another reason to stick with flooded batteries which are much more forgiving. We all need lots of forgiveness. Thanks.

[ErikFinn]

Originally Posted by Ex-Calif

You need to get the manuals and read the fine print. here are a couple of snips from the Sunsaver Duo PWM which I am settling on.

Note that to set custom points you need to get a software solution and I presume cable adapter) form Morningstar.

If you want standard profiles you can do it with DIP switching.

Did you find out if the Sunsaver Duo PWM is capable to be custom set for voltage?
Until now I've been under the impression that most Morningstar PWMs are fixed in this respect to 14.4V for flooded battery regulation (except the Tristar).
Trojan recommends my batteries to be charged to 14.8V daily (15,5V equalization), so I have kinda dropped any charge controllers not offering 14,8V regulation from my list. And I'm having difficult time in finding the "bestest" most suitable controller for my setup.

[Stu Jackson]

Don't buy batteries at WM. You can find the same ones for lots less elsewhere.

[Ex-Calif]

Originally Posted by ErikFinn

Did you find out if the Sunsaver Duo PWM is capable to be custom set for voltage?
Until now I've been under the impression that most Morningstar PWMs are fixed in this respect to 14.4V for flooded battery regulation (except the Tristar).
Trojan recommends my batteries to be charged to 14.8V daily (15,5V equalization), so I have kinda dropped any charge controllers not offering 14,8V regulation from my list. And I'm having difficult time in finding the "bestest" most suitable controller for my setup.

Yes you are right the Duo only has two built in profiles, sealed and flooded. DIP switch settings.

However you can customize the profiles with a Morningstar serial to 'meterbus" adapter (sold by Morningstar) and a PC. Look s like around $50 on Amazon...

[ErikFinn]

Originally Posted by Ex-Calif

Yes you are right the Duo only has two built in profiles, sealed and flooded. DIP switch settings.

However you can customize the profiles with a Morningstar serial to 'meterbus" adapter (sold by Morningstar) and a PC. Look s like around $50 on Amazon...

Thanks for super fast reply!
I'll have a look, this might be something that (once again) changes my puzzle of finding a suitable controller..

[Mike Sibley]

I decided to get the Blue Sky Sun Charger 30. It is adjustable and the display allows you to easily keep track of voltage and amp hours. I have been happy with the performance of the unit so far except for one area.

To install the unit, you connect two wires (+ and -) coming in from the solar panel and two wires going out to the battery bank. If the unit is operating at anything remotely close to it's capacity (30A), these wires should be AWG 12 or 10, especially if the combination of the two wire runs is more than 10 feet. To attach the wires to the unit, you remove 1/4 inch of insulation from the end of the wire and insert into the side of the unit then tighten a set screw. Unfortunately, the set screw is very small and engages only the very tip of the wire, allowing the wire to fall out in response to any movement. This creates a hazard of a short circuit and a resulting fire. I found a way to solve the problem (with additional work and expense), but I was disappointed that the unit wasn't better designed.