Friday 14 April 2017

Battery Drain problems

I used a modern core to modify the radiator in height, and as such removed the ability to completely convection cool the engine as the frictional loss in the vanes of the new core is too much. A new honeycomb core was way too expensive for my taste (£400 quoted). Instead I decided retained the modern core and added a 32mm electric pump from CBS instead.  Unfortunately the battery drain is 8 amps and that flattens the motorsport battery in no time unless you are in charging mode 30mph.

If I used a motorbike pump (less drain), due to the reduced bore, it would reduce the convection cooling even further. The CBS pump although very efficient is 80% redundant, it is only required to give a bit of extra circulation now and again.

The answer is simple, modulate the pump power at a ratio of 1:5 where On = 2 seconds and off =  8 seconds. This will reduce the power consumption by 80%. I found a Velleman 555 timer project kit in Maplin that will do the job just fine. However when I connected up the said kit it initially worked fine but on starting the A7 engine the times became random. I added a low dropout LM317T regulator, two resistors and a capacitor. This cured the problem and for good measure I put the whole thing in a waterproof/RFI enclosure. Again for good measure I used some capacitive feed throughs to connect the power.
Velleman project board with regulator

Waterproof/RFI enclosure

Update 4th Aug 21

This problem has been eliminated by the addition of an Alternator. The pump is now permanently connected via a thermostat mounted in the pipe to the top of the raditor.

Here is an Index page for the build

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