[Hack] Shoe Dryer - portable, battery+car powered

Dryer completed and running on battery

Can't stand the smell of overused shoes ? Putting your shoes in the washing machine is a no-no (like climbing shoes) ? You exercise in the morning on the way to work with no place to dry the shoes but in the car ? Well, same here...

Such smells are created by bacteria going about their business. The remedy ? Bacteria can not develop in a dry environment. So dryer = smells gone.

Many shoe dryers are available that either run on AC or on a car's 12V power via the cigarette lighter outlet. Unfortunately, the 12V portable dryers I tried did a poor job, and my car powers down the 12V outlet when turned off.

Enter this DIY dyer: it can run on either car or battery power and has a 1 hour timer. It also provides 12V out via its own cigarette lighter outlet, in case other accessories need 12V, even when picnic'ing away from the car (Phone, USB charger, etc).

Having spare Makita LXT chargers cluttering my garage, that conveniently provided the battery holder system and a ready made box to hold all the parts.

A couple of years later, still virtually no smell from my climbing shoes: just leather & rubber. Boop !

Functions of the dryer ('blower' would be more accurate, as it just moves air, no heating):

Input power from either 12V car cig lighter plug, or from 18V battery (Makita LXT)
Voltmeter display to monitor battery voltage
1 hour mechanical timer (bathroom fan)
12V 0.45A 80mm computer fan (note: a blower would work much better than a fan in this application due to the high back pressure. Wish I had one handy)
Car or battery powered 12V cigarette lighter outlet

Wiring example (not final), Looking at the charger from the back

Note: in Colorado the air is dry almost year round, so moving air is sufficient. In more humid climates it may be helpful to add an inline heating element.

High level description of how to modify the charger:

Remove the main electronic board
Drill with a large hole saw the hole for the PVC flange
Trim the PVC flange base until it fits, screw in place (I think I used a 2.5" diam flange?)
Drill and install the switches, timer, 12V outlet, voltmeter
Drill dozens of holes to let air in
Connect the voltmeter to the battery leads
Connect the battery leads to a step down 12V converter (add a fuse on Batt+)
Connect the positives from the 12V plug input, and from the converter output, to the input selection switch
Connect that switch's output to the output selection switch (skip that switch and the 12V outlet if don't care. It simplifies the wiring notably, and allows connecting the converter after the timer thus removing a constant low current load on the battery)
Connect the output selection switch's outputs to the Fan+ and 12V outlet's + signals
Connect all the negative signals together (except battery's)
Cut & glue the pipes

1-1/4" or 1" is best for the pipes that slide in the shoes
Taper the ends to facilitate sliding
Many ways to go from the flange's diam to each shoe and reduce diameters. Fun time at the hardware store playing with adapters 😏

And voila, smells be gone !