Charging problem on ST2 with Brush head

[camillitech]

Hi all,

my Lister ST2 stopped charging the batteries years ago when the resistor thing burnt out in the box on top of the alternator. I lived with it quite happily by connecting an ordinary battery charger to the AC output. Anyway I recently acquired a good 2nd hand one so had a go at fitting it today.



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As you can see the original is burnt out, when I fitted the replacement it started to get mad hot so I disconnected it pronto before starting the genny. However once the genny was running I reconnected it and it charged fine, it only seems to get hot once the generator has stopped.

Any ideas chaps, in words of one syllable 

The new resistor is off a 12v 3kW single cylinder if that makes any difference 

Cheers, Paul

[listerdiesel]

If there is a blocking diode in the charging circuit, check that it is OK and not short-circuit. It sounds as though the battery is running back into the DC start windings when the generator is stopped.

This function may also be carried out by a relay that has the contacts welded together.

On our SOM generator, we fitted a blocking diode as we didn't have the full set of control boxes to carry out that function, seen on the right of the box with two wires:



There is about 36 volts available for battery charging at full power, so volt drop isn't an issue.

You can also replicate the two-level charge rate by switching different taps on that resistor, which is effectively in series between the generator DC output and the battery.

Peter

[dieselgman]

We have the manuals here for many of the British generators in use for small Lister sets including Start-O-Matic. If I had the description for yours, maybe could locate the proper schematic to offer.

dieselgman

[dieselgman]

Here is one circuit layout for the Brush brand...



dieselgman