Saturday, 10 March 2018

Hot Rubber Smell

When we returned home yesterday Jan immediately commented on a smell of hot rubber coming from the rear of the Isuzu 4x4.  My immediate thought was I’d run some cabling over the exhaust and then promptly discarded the idea as something I’d never do.

Eventually I realised the Isuzu was in four wheel drive.  It’s something you shouldn’t do if driving on bitumen.  Somehow the selector knob in the cabin had been knocked from 2WD to 4WD.  The small 4WD icon on the dash is the same colour as the numerous other icons and I hadn’t noticed it.  Moreover this is the second time the selector know as accidentally engaged 4WD.

I’ve decided to fit my own 4WD warning light in a prominent place on the dash.  It only needs to illuminate in 4 High Range as 4 Low Range is rather obvious.

The first step was to remove the Selector Knob.  This came out rather easily when I inserted a small flat tipped screwdriver into the recess on the passenger side (left arrow).


There was a green plug under the knob.  I used the multi-meter (thank you Maplin) to establish which wire was ‘live’ when 4H was selected.   It was the White wire with the Black stripe.


I stripped some of the insulation off this wire and then soldered a length of spare cable to it.  This will be the positive cable to the LED.  The bare joint was wrapped in insulation tape and the selector knob re-assembled. 

The next step will be to visit Jaycars (Maplin equivalent) and buy a suitable LED.  My preference is for a bright Blue LED.  I don’t plan on driving in 4x4 when it’s dark so the bright LED isn’t going to affect any potential night vision.

The other thing I’ve been working on is the lithium battery project.  The plan to recover lithium cells from old laptop batteries will mean some of the cells will be “dead”.  I therefore need to test every cell to firstly identify the dead cells (which will be discarded) and then establish the capacity (in milliamps) of the remainder.  This means each cell will need to be charged; then discharged and finally; recharged.  I’ve purchased a SkyRC iMax B6 charger from eBay which is capable of doing the above.  However it can probably only test an average of one cell daily.  This isn’t a problem if I only want to make lithium batteries for electric drills as they only have 6-9 cells.  however if I decided to complete my major project; a lithium battery to power the house then that will require around 17,000 cells.  I’ll be long dead before that project is completed Smile

But wait……  The SkyRC iMax charger requires an external 12V DC power supply.  Moreover there are cheap lithium cell charger and dischargers available from China.  These require an external 5V DC power supply. 

You may recall I’m reluctant to throw things away (yes I’m a hoarder).  I’ve been trowing away old desktop pc cases; but not before I’ve removed the internal components; including the power supply.

Well the power supply has an input of 240V AC and dual outputs of 12V and 5V DC.  I’ve found my power supply for the SkyRC and the cheap Chinese chargers and dischargers.


There are two things to note here.

1.  The power supply won’t work if it is connected to the 240V supply but not connected to a computer motherboard.  I eventually worked out I could get around this problem by connecting the GREEN wire on the main power plug to the motherboard to any BLACK wire.  This tricks the power supply into working.

2.  The second thing is the power supply was reluctant to supply any 12V or 5V power without a ‘load’.  Usually this would come from the motherboard but as I’m not using one I connected a ‘dead’ hard drive to the power supply.  The hard drive provides a ‘load’ and tricks the power supply into providing the DC voltage.


The RED wire produces 5V DC


And the YELLOW wire produces 12V DC.

A 18650 lithium cell should be charged or discharged at 5V and 1amp.  The computer power supply is rated at 430 Watts (Watts = Volts x amps) so a VERY rough calculation suggests the power supply should be able to simultaneously charge or discharge 86 cells.  I’m thinking of simultaneously charging 20 cells and discharging 5 so there shouldn’t be a problem.


Don McCoskrie said...

There is a facebook page: DIY Powerwalls devoted to powerwall construction from secondhand lithium powerpacks. Might be worth a look (assuming you are on facebook).

Tom and Jan said...

Hi Don,

I don't go near Farcebook but there are a number of YouTube channels on DIY Powerwalls.

Pip and Mick said...


Have you heard that Maplins has gone bust? :-(
The shops haven't shut yet but the future looks bad.


Tom and Jan said...

Mick that hasn't made the news in this part of the world. However I'm not particularly surprised as Dick Smith Electronics here in Australia collapsed and it's business model was very similar to Maplin's.