Ennie’s going out of town this week on business and I suggested she take along a Garmin Oregon 450 that we typically use for geocaching. It’s not the best at navigation since it doesn’t do text-to-speech, but it’ll get you out of a jam if you get into one.

It runs off of two AA batteries and I like to keep an extra set just in case you run one set down. Of course the best (and greenest) is to use rechargeable batteries for the purpose. I picked up a few sets of NiMH batteries for use in the GPS and also for the flash for my camera.

This was all happy until last night.

I inserted the batteries to top off the charge and was greeted to…

Nothing.

Not good.

Now what?

First let’s try another outlet. No joy. (Putting to rest the question of “Is it plugged in.”)

Ok. Let’s pull out the multimeter and test voltages. (Yes, I have a POS multimeter. When I have some spare change I’ll pick up a good Fluke or Agilent or similar grade one… one that has real protection and won’t blow up in my hand. Thankfully this POS one hasn’t yet!)

The cord works, but there’s no power at the end connector that plugs into the socket on the charger itself. It seems that the problem is with the power supply itself.

At this point I checked the charger (the thing you put the batteries in) and the input voltage is 12-16V at 4A. Well, it turns out I have a power supply that’s smack in the middle of that range — nominal 13.8 V. It’s the one I have my radio attached to!

It was short work before I cut off the cord and connected it to the power supply. The fan in the charger whirred to life!

Problem: Solved.

Today, when I was taking pictures to post here I started to go through steps again:

• Mains voltage: Check
• Voltage at input to power supply: Check
• Voltage zero at power supply output: F***! It’s 16V! (Yes, En can vouch for the fact that it wasn’t working last night)

I guess I just have a dodgy power supply.

For a brief moment I thought about splicing things together again… but for what? I already determined it wasn’t working right.

I continued with the plan to attach a lighter plug to it.

A few minutes later et voila: plugged into the big power supply and charging! Added bonus: I can use it in a car without an inverter!

Lessons:

• When electronics don’t work: Check voltages
• It’s good that Duracell printed voltage and current specs on all the devices
• Don’t be afraid to break something that’s already broken to begin with
• Even though it is intermittent, Duracell did a fine job engineering their power supply. Nicely routed blast shields separate out the high and low voltage parts.