solar controller

Don Crowther

Don Crowther

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Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
This is a question that I might have seen the answer to but for the life of me can't remember!

What parameters should my solar controller be set to. I have a 125 watt solar panel and It's connected to my house bank of 2 12 volt 205 amp hr deep cycle lead acid batteries.

Should the max volts going in be ???????????
And where should the low point be set.?????????
Thanks
 
C

Chief RA

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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Nominal voltage level for a solar panel is usually 18 volts but look on back of panel for exact amount. I personally do not have a low setting for the controller I use as it is all automatic internal presets as far as I know. I do use 12 volts as my lowest operative voltage level for my battery bank if that helps. I observe the levels with a battery bank meter monitor.
Chief
 
Don Crowther

Don Crowther

.
Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
Thanks Chief
I don't have any monitors for the electrical system. I know the panel will put out about 19 volts in full sun.
I don't think I want that much going into the batteries. I can though set my controller I think about 14.4 on the high end and maybe 11.8 on the low end.
 
C

Chief RA

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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Don: If 11.8 is what the controller would show the battery bank that would be low as you might want it to go but the reverse diodes and controller will basicly prevent back current to the panel anyway. Just try not to operate the system below about 12 volts as thats over 50% battery discharge. The controller will drop your 19v down to around 14v and batteries should be happy. You can get an inexpensive bank monitor at Amazon for about 15 bucks and it works great. Innova 3721 battery and charging system monitor is the unit. Chief
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Don Crowther said:
This is a question that I might have seen the answer to but for the life of me can't remember!

What parameters should my solar controller be set to. I have a 125 watt solar panel and It's connected to my house bank of 2 12 volt 205 amp hr deep cycle lead acid batteries.

Should the max volts going in be ???????????
And where should the low point be set.?????????
Thanks
Click to expand
By "low point" do you mean float voltage? If you do about 13.4 volts.

Max volts should be somewhere between 14.4 and 14.8 volts depending on what the battery manufacturer suggests. Trojan wants 14.8 volts for bulk.

What controller do you have?
 
Don Crowther

Don Crowther

.
Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
It's a 30 amp controller not a name brand but one from China. I found my batteries low on water this fall so I think it might be set to high.
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
I think that this falls under the RTM rule. Way too many unknowns to make anything but general comments. Max voltage is the max charging voltage the controller will output. Low set point could be a number of things depending on what type (MPP, PWM, buck-boost.....) of controller you have
 
C

Chief RA

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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Thanks Bill. I didn't want to comment and start an argument as I had hit it as close as I could with the info provided. Chief
 
T

travlinon

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Sep 6, 2014
2
Catalina 34mk11 Mandurah
I have a Mppt controller also from China that is programmable for charge voltage etc.
My panels and batteries are similar to your setup and I have used the following
Bulk. 14.2 volts (though 14.4v is sometimes recommended)
Float 13.6 volts
Check out the web site Ample Power who have a huge amount of information on battery charging.
The above figures were an average of a large number of differing views and may not necessarily be correct but have been working for my batteries.
Also of interest is following charge rates
12.7v. 100%
12.4v 75%
12.2v 50% ( lowest batteries should go.)
12v. 25%
If I'm wrong on any of the above I'm happy to be corrected.
 
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Don Crowther

Don Crowther

.
Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
Mitiempo; I don't remember what it is set at. But the batteries were low on water when I pulled her. I would like to have these numbers for the spring when I set everything up. The boat is in Saskatchewan but up on the hard.

I guess Bill what I'm looking for is what the controller should be set at so I don't boil the batteries and not so low that I'm letting them get too discharged. Does it matter what type of controller it is? I don't know if it does when you're setting the charge parameters.

I think that Travlinon got what I was getting at. At least I've got some numbers to use when I set things up in the spring.
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Don Crowther said:
Mitiempo; I don't remember what it is set at. But the batteries were low on water when I pulled her. I would like to have these numbers for the spring when I set everything up. The boat is in Saskatchewan but up on the hard.

.......and not so low that I'm letting them get too discharged. Does it matter what type of controller it is? I don't know if it does when you're setting the charge parameters.
Click to expand
I'm not sure what you mean by "not so low that I'm letting them get too discharged." The controller will charge to the set point - say 14.4 volts - and then go into float (13.6) keeping the batteries fully charged. If power is used the controller should replace the AH used, going into bulk (14.4) when the batteries are down enough.

Batteries should be checked every month or 2 and distilled water added when needed.

There are many recommendations of charging voltages on the web. The only accurate one will come from the manufacturer of your batteries, not from Ample Power or a charger maker.

If your batteries are on the boat as long as they are fully charged the cold will not bother them and they will keep their charge for the winter. Batteries will go down in warmer weather.
 
Don Crowther

Don Crowther

.
Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
I guess I'm not fully understanding what the controller does. Why would it need a low setting. I think I understand the need for a high cutoff but the low makes no sense to me.
I did pull the batteries once I saw they were low on water. They are fully charged and stilling outside in my shed.
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
A controller is similar to a shore powered charger with a bulk/absorption stage and a float stage. Bulk until a certain voltage is reached and then a float to finish and maintain.

If it is a controller with load connections it may have a low voltage cutout on this connection. Load isn't used on a boat so ignore it if it is there.
 
Don Crowther

Don Crowther

.
Sep 4, 2007
794
Hunter 33.5 Elbow, Saskatchwen, Can.
So l should ignore the low voltage setting and only be concerned with the High?
And it should be set at 14.4 or so. The batteries are from crappy tire deep cycle lead acid.
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
14.4 is good.

What does the manual say about the low setting?
 
C

Chief RA

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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Don: I do not have a low setting on mine but if I did I would set them at what you said initially. 11.8v seems reasonable to me to prevent anymore battery bank drawdown past that. 14.4v sound fine for top. These settings are not exact as some of these guys like to think. When some guy jumps my input over a few tenths it does tend to irritate me. I have only been in electronics for 50+ years! Lead acid batteries are fine, just take care of them.
Chief
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Chief RA said:
Don: I do not have a low setting on mine but if I did I would set them at what you said initially. 11.8v seems reasonable to me to prevent anymore battery bank drawdown past that. 14.4v sound fine for top. These settings are not exact as some of these guys like to think. When some guy jumps my input over a few tenths it does tend to irritate me. I have only been in electronics for 50+ years! Lead acid batteries are fine, just take care of them.
Chief
Click to expand
I know of no controllers with any setting as low as 11.8, which is 30% SOC. Controllers will float a fully charged battery at about 13.5 or thereabouts and if the battery drops they will go into bulk of 14.4 or thereabouts.

11.8 will shorten battery life considerably. If a controller lets a battery get that low when there is sun on the panels for output throw it away and get a new controller.
 
C

Chief RA

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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
mitiempo: I still do not know what low voltage setting he wants if it is not battery bank output. In that case 11.8v is low and would be an emergency cutoff level. If you know what this low should be set at then tell him and quit trying to upstage me!
I learn new things regularly on this forum. You have not taught me anything!
Chief
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
I've already told him. 13.5 or so for float and 14.4 for bulk/absorption.

Controllers do not have a low setting such as 11.8. They are really no different than a shore powered charger, but using solar panel output instead of AC power.
 
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