Limiting Solar Charge Current from the Charge Controller

[Matrix]

Mike with the MS CC to use this method it need to have the Whiz-Bang Jr

[Sunking]

FWIW the way it is intended to limit charge current is panel wattage.

[Matrix]

I thought to get battery current limit with the Classic, you had to have a Whiz-Bang Jr to sense the battery current ? How else can it differentiate between loads and charging ?

You are correct Mike, it also requires a Whiz-Bang Jr for the limiting.

[Mike90250]

I thought to get battery current limit with the Classic, you had to have a Whiz-Bang Jr to sense the battery current ? How else can it differentiate between loads and charging ?

[Sunking]

Make this easy, don't worry about it. You have Trojan L16 hybrid batteries and they can take C/4 all day long.

[Matrix]

My battery bank is 4 6v 435ah wet batteries in series. C/8 would be 54 charging amps and C/10 would be 43 amps.

I have an array that can do upwards of 71 + charging amps. Just today with a mix of sun and clouds I saw a moment of 71 amps to the batteries. While this is not a sustained charge amp and it does not happen very often or long, I have seen the CC able to hold 60-66 amps plus for extended periods of time.

Question #1: are those higher amps a problem?

A solution would be to lower the output amps of the CC. The MidNite Classic 150 has an output amp limiting setting in the menu. But this would also limit the amps for loads and opportunity loads if I were to set it to C/8 of the battery Ah. Not a good idea I would think. But it may also not be a good idea to be "hitting" the bank with current up to C/6 + for momentary bursts.

A little known setting for the Classic 150 is the ability to Limit Charging Amps Only WITHOUT limiting total output amps for opportunity loads. This is a setting that is not easily accessed and is buried deep in the programing. But easy to do. I have done it ... and it works. (I can post the PDF of how to set the charge current limiting if anyone is interested)

Question #2: would there be any real benefit to limiting the charge amps in the Classic to say the exact C/8 of the battery bank? Does occasionally going higher than C/8, for short times during a charge cycle have adverse effects on battery health? (obviously assuming battery temp is kept within reason)

I have done the charge current limiting in the Classic. It does work, BUT the trade off is that it seems to build up a little more heat on the controller. So it is a trade off.

Question #3: which is worse? Times when the charge current exceeds C/8 during a solar charge on the battery, OR heat build up on the CC's circuit board and FET's, etc.?? I assume the hi heat would limit the life span of the CC. (right now even with the CC's internal fans, AND an external fan on the CC running all day the FET's can get 63*C during charging)

If setting the charge limit would be a good idea, Would you set it to C/8 or something higher? Lower?