CTEK 250S Dual regulator

[terrya]

The following is a copy of an email conversation I had today with Bainbridge Technologies re the Ctek 250s Dual installed in my old trailer. I thought anyone using one of these might be interested. It looks like I will have to add another regulator to the system. Terry

I have been advised that the 250s dual may require at least 80w of solar to operate correctly. I only have a single 80w panel. I have done some tests with the 250s vs a basic pwm solar regulator and there does appear to be a problem. I can only get about 2.4A max from the 250S as opposed to 4.5A from the basic reg. These figures were obtained in full sun. In low light conditions the 250s had only 0.006A vs 1.1 A for the reg. Can you help.
Cheers Terry Agland

Hello Terry;
The D250 S dual will work with a panel as low as 50 watts as we have tried it in the workshop - but as it has an MPPT inside it, the losses can be quite high with such a small panel against a PWM solar charger. PWM means - Pulse Width Modulated; and MPPT means - Maximum Power Point Tracking.

Also, with higher temperatures in Australia an MPPT on low panel outputs is not as efficient. The D250S Dual was originally designed in Sweden where it’s very much colder.

Ideally if you can go up to panel size of 300 watts it would be much better on the D250 S. The open circuit voltage on your panels needs to be no higher than 22 volts DC whatever panel wattage you use on a D250s dual.

At such low power levels, using a PWM charger will be more efficient, as you have already found out. On the other hand an MPPT charger is better than a PWM unit, when it comes to using cheaper quality panels and also obtaining the maximum POWER ( not CURRENT ) for your battery.

The following link will explain why an MPPT ( as used in the D250S dual ) is operating differently to a cheaper PWM solar charger at low power levels >

http://solarcraft.net/articles/comparin ... ntrollers/

Regards;
Kimbal Summers
Warranty Technician
Bainbridge Technologies


Hi Kimbal,
Thank for the response. The way I read your answer is I should get rid of the 250s as it is inefficient in Australia and it will not work efficiently on my 80W panel. This system is installed in a small trailer and there is no way I can carry 300W of solar power. Even the link you provided advises that I should be using PWM or at least 170W of solar.

I am really disappointed with this as this information was never provided at the time of sale. I actually have two of these units (my trailer and my daughters) and now I have the additional expense of replacing them or adding a PWM regulator in parallel.

Be assured that I will be passing this information to the members of my camper trailer group and my 4wd group.

Terry Agland

Hello Terry;
You can still use the D250S Dual but it won’t be as efficient as the PWM circuit, unless you up your panel size – which I understand is not practical for you to do.
Most end uses have around 150 - 250 watts on their D250s.
As for the alternator side of the Dual that’s another discussion, separate to the MPPT on the solar side. You can use that in its normal application, unless you have a smart alternator.
Regards;

Kimbal Summers

[GEOFF.PAULINE]

Responded to your same post in the TLCC forum. Cheers