Adding solar panel to dual battery system

[Old.Tony]

If it's charging at 22V then it's cooking the batteries worse than third-day-lucky fishcakes.

The absolute MAXIMUM a 12V lead acid (excluding gels, keep reading) should EVER be charged at is 15V - you can, if you are using a charger that knows what it's doing (read "C-Tek") get that up to 16V during an equalisation phase - again, only for batteries OTHER than gel batteries.

Equalisation is important, because it helps remove the sulphation caused by cycling a battery below full charge (actually the crystals can form at 99% charge but the rate is very low, they start in earnest with a wet cell @ about 50% charge).

Anything over 14.1V cooks a gel, period. The problem with gel batteries is the silicate added to the sulphuric acid to make it a jelly really does make it a jelly. When an air bubble forms in the jelly, it stays there. As all the little bubbles form over time, eventually there's no path through the acid for any reaction to occur and the cell dies - end of battery.

Normal wet-cell batteries and AGM batteries don't suffer from this particular problem because they are a true liquid (not a jelly), so when a bubble forms it can rise to the top and burst, restoring the pathway for the reaction in the battery that produces power.

The controller should regulate the power to a voltage matching the requirement of the battery being charged and should be able to discern the difference between gel and other types either by measuring the battery (internal resistance) or by dip switch.

If there's nothing in the manual to indicate a regulated output, yes I'd toss it. Jaycar sell a decent 20A-20A controller that uses a dip switch to choose between gel/other batteries. It's quite a good unit.

 

[RustyNav09]

hey fellas

this is a generl solar related question. i have an EvaKool 100w solar panel kit which has a 10amp regulator fitted to it. i have since put in anderson plugs so i can bypass the regulator and just have the solar panels running into my Ctek D250S Dual charger usign the Solar Input feature. I plugged it in today using the bypass into Ctek and to my surprised i was getting a 24.50V input from the panels. i also had the same outcome with the panels plugged through the 10amp regulator on the panels. i am confused as i thought they were meant to be around the 12.8-14.4V input when used with a regulator like the inbuilt one or the ctek unit.

can anyone help me out i dont wanna destroy my good agm deep cycle battery

 

[Old.Tony]

The C-Tek charger should take that voltage and manage it properly. Solar panels (with no load) can produce voltages in that region and the C-Tek is designed to handle it. My own regulator reports PV voltages of over 20V but it does manage those nicely and I rarely see the battery (Optima D31A Yellow Top spiral-wound AGM) nudging 15V.

I would put a multimeter on the battery and see what you're getting there. As long as you're getting <15V during bulk & absorption phases and <14V during float, the thing is performing perfectly.

 

[RustyNav09]

I'm not sure how you tell whether its changing stages but it climbed from 12.7 to .13.7 pretty quickly. Then I took the multi meter off. I will leave it on for longer next time and watch it.

 

[Old.Tony]

12.7 will be the battery on its own. The charger at 13.7V will be introducing current to the battery and waiting for the voltage to start climbing. Right at the start the charger might be in a fairly blind "refresh mode' where it introduces a low constant current (like 2A) to se what the battery does - a charged battery will get a decently high voltage fairly quickly and a flat battery won't. The charger will monitor the voltage and when it rises high enough, it will know the state of charge of the battery.

Just another thing about battery refresh mode - it's not a bad thing when trying to revive old batteries. The problem with older batteries is that they generally show a very, very low voltage and chargers will refuse to charge them. A 'refresh' charge will boost the battery a little and you MAY be able to get the battery going again.

 

[G-Dubya]

Hi all, I have just put a Ctek D250s dual in my Navara. I read in the manual that they have a maximum input voltage from solar of 22v. When looking for a solar panel to purchase I am finding it difficult to work out what the maximum voltage from a panel is. There are a number of values listed on products including maximum voltage and open circuit voltage. The panel I was looking at had a maximum voltage of 18 volts but an open circuit voltage of 22.5 volts. I have two questions:
1. What is open circuit voltage?, and
2. Will open-circuit voltage being over 22 volts affect the Ctek D250s Dual?

Thanks,
G.

 

[Old.Tony]

The "open circuit" voltage refers to the voltage you'll get off the panel when it's not connected to anything. As soon as you connect it to something, the voltage will drop. It drops further when a decent load is placed on it.

It would be safe to connect that panel to the unit, because the maximum (closed circuit) voltage is lower than the max voltage of the C-Tek charger.

 

[G-Dubya]

Cheers for that. One more question though. With the Ctek being an MPPT regulator, should I get a panel without a regulator. It is my understanding that regulators burn off any excess energy coming from the solar panel to deliver a certain amount to what ever it is connected to. Would it give a better charge to my auxiliary battery if the panel had no regulator and the Ctek then decided what level charge is given?

 

[Old.Tony]

Never hurts to try things out in the driveway, too. Been a few evenings spent in the caravan at home here!

 

[G-Dubya]

Now I have a few more questions.

1.With the Ctek being an MPPT regulator, should I get a panel without a regulator. It is my understanding that regulators burn off any excess energy coming from the solar panel to deliver a certain amount to what ever it is connected to. Would it give a better charge to my auxiliary battery if the panel had no regulator and the Ctek then decided what level charge is given?
2. Could I use a folding panel (160w) if I removed the regulator and connected the positive for both panels and negatives for both panels to a common Anderson plug (panel positives to Anderson plug positive, negatives to negative {in parallel??}). Would this create too much voltage for the Ctek or would produce the same as the label on the panel states?

 

[Old.Tony]

The C-Tek charger does allow you to use an unregulated panel, but it will just as easily use a regulated one. You could describe the process of limiting voltage/current as "burning off the excess" because that's sort of what happens.

Connecting panels in parallel produces no extra voltage, it produces extra current. Works just like your AA batteries.

 

[G-Dubya]

I had an ARK power pack that had a 100ah battery in it. I put the 100ah battery into the battery box I made for the tray. Rather than buy 2 new 130ah batteries, I decided I would save a few dollars and get another 100ah (exactly the same as the one I already own, a century n70t) and put it back into the ARK power pack. I also ran an Anderson plug through the top of the box that connects to the battery terminals inside via a 50a circuit breaker. I was thinking I could use a lead to connect the Anderson plug on the power pack to one of the auxiliary plugs coming off the battery that's connected to the CTEK. When travelling I could have both batteries connected to the CTEK and separate them once at the camp. Are there any problems I may encounter if I do this?

 

[Old.Tony]

Because you've chosen the same size and type of battery you've reduced the likelihood of any problems. Technically they'll still fight each other because they'll be SLIGHTLY different and this will get worse as time goes on because age and cycle depth alter a battery's charging characteristics. The difference is marginal, but will grow over time - it would be best to never let the batteries sit too long together without the charger connected to them, especially in a couple of years.

I suppose you could try and balance that out by using the batteries alternately but even then there will be variations.

While technically there'll be some minor complications, in application they should be just fine.