Help with CTEK D250s charger & 36v solar panels

[nitram38]

Hi Newbie here and an Electrician, but I've made an error! (never wired PV before)
In my rush to build an off grid camper I bought a ctek d250s and smartpass along with 3 x 250w 36v solar panels. I also have 4 x 125Ah batteries.
Installation all went well except that I connected 36v of solar to a ctek d250 which has a max of 22v input. (I missed this detail)
The result is a fried D9 diode and a 30A fuse inside the d250s. The smartpass was un-affected.
I have a choice of the following:
1) Repair the D250 by changing out the diode/fuse and finding a converter of some kind to lower the PV voltage (having trouble identifying the D9 diode as it is fried)
2) Buy a new D250 and finding a convertor etc
3) Either of the above and buy new panels (ouch cost £420 and are on my van)
4) By a completely different mppt controller (but I prefer the ctek for the main battery connection/alternator and also the battery deep cycle functions)

I would prefer to stick with the CTEK set up and somehow lower the PV voltage.
All ideas welcome!

Cheers Martin

[SunEagle]

My suggestion is to get a quality 60 amp MPPT type charge controller. With that 750watt total of panels and I presume a 12volt 500Ah ( 4 x 125Ah in parallel) battery system you need a 60amp CC that is designed for accepting the input voltage of those 3 panels wired in series. I don't believe that Ctek is the right CC for your solar/battery system.

[Mike90250]

Some charge controller models to look at in the 60A range
Morningstar TriStar MPPT 60
Midnight Classic 150

I'll assume the battery system is 12V. Wire the panels in parallel, with a combiner box and DC circuit breaker on each panel + feed
You would have a total of 21A (7A from each panel) (36V 250W ea) @ 36V going into the charge controller, the output of which would be 48A @ 13V
No cheap fix, this is major power, and as you see, parts already got cooked. And I doubt replacing the cooked parts would fix the controller, other parts internally likely died too. And controllers want to be connected to the BATTERY first, allowed time to boot, then the PV panels connect

[nitram38]

I was hoping you wouldn't suggest that!
My reason for staying with ctek is because of some of the features:
Charging from alternator & charging my van battery separately.
Looking after the batteries with different charge cycles.
The d250s coupled with smartpass is good for up to 100A of charging (the blown fuse is 30A from solar)
I'm not doubting your advice, just that I would like to maintain these features without spending lots more money.
I'd like to try and repair the d250s as it has been done by others. The fried diode is there to protect the unit.

Has anyone used a dc-dc converter or another mppt to reduce the voltage of a pv and then fed the ctek?

[Mike90250]

You could set up a 24V bank and if the ctek is a ROBUST MPPT controller, it might work. But MPPT Charge Controllers, must charge a battery bank, Not a capacitor bank, not a dummy load. They need steady DC on their battery terminal to run the internal electronics.
Don't try to feed a 24V battery to the solar input of a PWM controller, that will fry it, or blow it's fuse instantly - the battery can put out 100's of amps for a couple seconds as the PWM switches on and off, a PV array has limited amps it can supply to a controller

[nitram38]

I've bit the bullet and ordered this: https://www.ebay.co.uk/ulk/itm/152013917333

I will sell the CTEk

[nitram38]

Just to update everyone. I have the EPsolar tracer 60A controller working very well. I have bought a Voltronic unit to keep the Van battery topped up.
On a reasonable day the PV was 17A @ 35.5v. It was charging my 500Ah of batteries at 12A 14.7v for about 30 mins but now they are fully charged, 0.3A. (max manufacture spec current is 8A per panel, so total possible is 24A theoretically)
Will the solar panels charge the batteries and supply power to a load at the same time (via the battery load)? Only I calculated that this would give me around 39A at 14.7v available (allowing for losses). Currently as my Van is being built, I have tiny loads so I can't test this.
If the panels will supply a dynamic load and charge at the same time, happy days!

[nitram38]

[nitram38]

Bloody iphone! won't put right way up in this forum