On 3/25/2012 1:18 PM, joost wrote:
Hi,

In an attempt to restore a pair of sulphatated Trojan T105 batteries I
ordered a desulphator kit, soldered it together and hooked it up to
the batteries. After it had been pulsing for a week and a half, the
batteries needed to be recharged (the pulser is powered by the
batteries). I connected my nice CTEK 15 A charger WITH THE PULSER
STILL ATTACHED to the batteries. I'm afraid this was a mistake. In my
understanding, the batteries should absorb the peaks produced by the
pulser and not damage the charger. However, now it seems that my
charger is only outputting 17.0 volts (always) and heavily
overcharging any battery that I connect it to. The peaks from the
pulser might have been higher than I thought.

I opened the casing of the charger, but couldn't any component that
looked fried. Can anyone tell me where to start looking for the
defective component? It is quite a complicated microcontroller
controlled charger, but I still have some hope that there is a single
component that needs replacement for it to start functioning properly
again.

Many thanks,
Joost
There are lots of claims made by desulphator vendors. I've never read
anything, outside the vendor sphere of information, that said they
worked at all. My experiments agree that they don't work.
I assume you wired the desulphator correctly?

The symptom of a sulphated battery is high internal resistance.
One theory is that if you put a huge voltage spike into the battery,
you can dislodge or reverse the sulphation.

One measure of the progress of desulphation is to watch the
amplitude of the spikes go down as the process proceeds.
In my experiments, I never saw any reduction in spike amplitude
and never experienced any improvement in ability to take/deliver charge.

So, if your batteries are sulphated, you'll see high voltage spikes.
Only a good battery could absorb the spikes...in which case you'd not
need a desulphator.

Sounds like you shorted whatever controls the charge current in your
charger.
May be a FET or SCR.
Is there any activity on the lights on power up that suggests the
logic might still be working? I assume you checked for a fuse
somewhere in the logic supply? If the pulser jacked the VCC up to
the peak of the voltage spikes, you probably fried the whole thing.

Not clear what charger you have, so downloading the manual is ineffective.
Without schematics, or an understanding of battery chargers that you
don't appear to have, it's gonna be difficult to fix it.

You're probably going to want to probe around in it live with an
oscilloscope.
Looks like an offline converter that can be dangerous to service without
proper equipment (AKA You get dead).