Saturday 24 June 2017

Battery charging revisited

I took it for a run today after my local car club gathering in the centre of town. To my discomfort I detected a burning smell under the bulkhead (this side of the fire wall).

The wiring harness was installed some time ago along with a 12V (Lucas 3182) regulator feeding the generator. This has the effect of converting the charging circuit to 12V with only one extra part. The only thing you need in addition to the regulator is a 3 ohm resistor to reduce the field coil current to approx. 2A maximum. In reality I found that to get a reasonable rev point where the charging light went out I had to fit a 2.2 ohm resistor. See: (regulator to field coil designated -F).

This probably means it is dissipating in the region of 16W. I had selected a 20W resistor which was 2 x 10 watt jobs glued on to a fiberglass board with epoxy and mounted on the bulkhead. The resistor rating was ok but the heat from the resistor created a foul smell when driving about due to the epoxy being over heated.

Old arrangement
I decided to change the arangement by mounting a single aluminium clad 50W resistor onto an extruded aluminium heat sink and bolted it on it's original location under the dash. This is complete over designed solution for what it is......but I wanted this problem to go away as I hate the smell of burning glue.

I had a standard alloy heat sink extrusion laying about from another project so I machined a lump out of the middle to take the resistor and it's M4 fixings, precision drilled 2 more holes to mount it (where it had been before) and machined some plastic insulators to terminate the wiring connectors (M5 tags either end of the resistor) and secured them in place with rivnuts.

The charging ability of my setup is not great but is now somewhat more reliable and more pleasant to drive with. All I need now is some dry weather to try it out!

New alloy extrusion solution

Update 4th Aug 21

The generator has been replaced by an Alternator, no mre charging issues.

Here is an Index page for the build

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