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3-stage charge controller worthwhile?

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william2021

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Jan 24, 2021
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Hi, I'm still learning while trying and just got a question. I have two Duracell 6-volt 1kWh golf car batteries in serial and 4 100W panels in serial. Currently I bought a Sunnysky 60A MPPT charge controller. I just learned that it's not a 4-stage charger. Is it worthwhile changing to a 3-stage controller such as Epever or Renogy?

The reason I'm wondering is, I never got the expected 1600Wh from the panels any day, the most I got was 571Wh. Of course it has to do with the many cloudy days and the direction the panels were installed. However one day the following happened:

1. charge controller was charging at 39W under clear sun with 12.8V measured on the battery (partly due to Peuker's Law)

2. I ran a 600W cooker via an inverter, and the voltage quickly dropped to 11.9V

3. AND the charger now charges at 175W! with nothing else changed!

That makes me thinking - maybe my charge controller was not charging as much as it could? Would a 4-stage charge be able to charge close to 175W instead of 39W at 12.8V (during charging, of course)? What the percentage a 4-stage charge controller can charge more per day?

A minor question is, for a 12V battery system, what voltage at rest is considered 100% full? I've seen it charged to 13.1, 12.9 etc, yet people appear to suggest it at 12.7V. But I definitely never obtained close to 1000Wh when the 2000Wh battery system discharged from 12.7 to 12.2V (which is supposed to be 50% full).

Thanks!
William
 
Last edited:
Welcome to the forum.

Most chargers are 3 stage. What's this 4th stage of which you speak?
 
william2021 said:
That makes me thinking - maybe my charge controller was not charging as much as it could?
Click to expand...
What are the settings on your solar charge controller (SCC)?
What is your battery bank?
How are your 4 panels placed in regards to the sun? Angled properly or on a flat roof? Any partial shading?
Shading, even minor partial shading is VERY detrimental to panels arranged in series.

Any pictures of your system that we can have a look at to maybe see something out of place? There are a LOT of eyes on this forum.
 
Ah. Equalization. Many chargers have this feature. I don't even count it as it really shouldn't be done on any arbitrary basis.

Are your batteries flooded, AGM or Gel?

I just looked up the Sunnysky.

I'm pretty sure I have the same version of this. It's terrible for lead acid. You should return it. It will consistently under charge your batteries due to its limitations.

 
MisterSandals said:
What are the settings on your solar charge controller (SCC)?
What is your battery bank?
How are your 4 panels placed in regards to the sun? Angled properly or on a flat roof? Any partial shading?
Shading, even minor partial shading is VERY detrimental to panels arranged in series.

Any pictures of your system that we can have a look at to maybe see something out of place? There are a LOT of eyes on this forum.
Click to expand...
My current charger allows to set, in addition to the battery type etc, the following (with the default):

floating charge: 13.8V
equilization charge: 14.5V
maximum current: 60A

Is there anything I can change so it charges more efficiently? I don't mind occasionally change setting when season changes. Or only a 3-stage charger will do significantly better?

Right now it's just 2 Duracell 6V 1000Wh batters in serial. There is no shading.

The main fact that triggered my post is as mentioned above, it was charging only 39W at 12.8V, but at that moment, when nothing else changed, when discharging for 600W appliance and the voltage immediately dropped from 12.8V to 11.9V, it immediately changed to charge at 175W. That means the charger was not using all power from the panel before applying that 600W load. So I was wondering, will a 3-stage charge controller be able to more efficiently charge at 12.8V, using all the 175W?

Or I can merely change some setting above to achieve similar improvement?

Thanks!
 
Last edited:
snoobler said:
Are your batteries flooded, AGM or Gel?

I just looked up the Sunnysky.

I'm pretty sure I have the same version of this. It's terrible for lead acid. You should return it. It will consistently under charge your batteries due to its limitations.

Click to expand...
Yes, it's flooded, and the link I bought is https://www.amazon.com/SUNNYSKY-Solar-Charge-Controller-12V24V48V/dp/B073P72XGC/. I thought it's better than yellow one you linked above, but looks like they are the same :-(
 
Yes. You need to monitor your charges every day. Set float to 14.X for the battery. Wait for it to charge and then change float to 13.2-13.8 depending on your battery. You need to do this every single day. If you fail to adjust your float voltage back down, you will damage your batteries.

The other choice is to replace it with a non-junk charger.
 
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