The Honda is fine though in terms of cold start and reliability. All it needs is a 12-V trickle charger to get the Yuasa lead-acid battery through the winter. To prevent embarrassment the old Sparta needs recharging in the garage after just about any ride. It’s a 15-hp two-stroke two-cylinder engine with a kick starter only and due to its compression, dual ignition coils, and dual sets of contact breakers, it will not cold-start with a battery voltage below 6.20 V. Anything upwards of that and the engine starts immediately and runs perfectly. 4 Insiders: two-stroke cold start combustion is critical on spark voltage. And no CDI in 1956.

The previous winter both bike batteries successfully hibernated on a suitably adjusted Delta Elektronika benchtop power supply. Every 4 weeks or so I changed between the 6-V battery and the 12-V, and put the charged battery through a discharge cycle with a simple lamp. On occasions I did miss the Delta supply in my electronics workspace and I also regretted its long term energy consumption on the grid — it’s a classic 0-15V / 3 A linear regulated PSU from the 1980s. Even the 50 or so milliamps-out to the battery in the elongated trickle charge phase did equate to 5-10 watts consumption from the power outlet.

So I wanted a state of the art charger with these features:
  • Compact and light
  • Totally safe
  • Automatic
  • Prudent on my batteries
  • 6 V and 12 V, auto-detect if possible
  • Slow charge and trickle charge
  • Lead-acid and gel batteries
  • Connect & forget
  • Cost: <0.33 x [new 12-V 14-Ah motorbike battery]

What I did not require was “fast charging @ lots of amps” and/or “starter aid”.
I do not ride these bikes in winter time, and looking forward to roughly four months of hibernation for my batteries I started an Internet trawl for a suitable charger. On a Dutch group-deal site I saw just what I needed at a ridiculous price of €80 but now! – due to immense response! – selling at €20 plus shipping! The image of the charger looked familiar and I remembered having seen the device in the spring at Action, a wideband super discount store chain in the Netherlands.

What? Dunlop?

I was delighted to find the “Dunlop Automotive 5-stage 6V / 12V battery charger” for €11.95 in a nearby Action store, and bought two (along with a 3-channel HDMI switch, sorry). Two remarkable things: one, the manufacturer is a Dutch company, and two: there was much technical terms and imagery in and on the package, like an ideal gel-type charging curve and words like volt and amp, all with the correct symbols although with decimal commas which gave the product’s Dutch origin away. Just as it was easy to tell this was a PRC (Taiwan) manufactured product carrying CE approval.

The build quality I found satisfactory and a far cry from other PRC but also German, US and UK bike / boat /snowscooter chargers I had seen. The case is sturdy (in fact it’s IP65 rated), the DC-out cables and connectors are certainly up to the 1 amp maximum output current (for 12 V). Two polarized (i.e. fool proof) adapter cables are provided to connect your battery: one with spring clamps and one with cable eyes. The latter cable is ideal for my bike and small boat batteries which have rectangular terminals with a central hole, as opposed to the solid round studs on most car batteries. In the case of my motorbike batteries, the clamps are too large for a secure fit. With the cable eye however you achieve a solid connection using the same bolts and nuts that normally secure the vehicle + and – cables. Of course, this is a no-brainer with the battery removed from the bike and in a secure place in the garage or in the attic.

Almost-destructive testing

I left one charger in its blister packaging and decided to pester the other to see if it survived “garage style” mishaps like:
  • Regular short circuit, 1 hour.
  • Bob Pease style dynamic short circuit: draw sparks by pulling a coarse file over the output contacts*.
  • kick start a 12-V Chinese scooter (28-V, 150-ms surges lasting about 1 second)
  • Apply up to 30 volts reverse from a 30 amp PSU.
  • Ditto from a charged 30 mF electrolytic capacitor.
  • Expose to 5 watts of UHF RF power from a handheld at 30 cms distance.
  • Connect a 24-volt truck battery with correct polarity.
  • Spill engine oil over it (charger swithed off)
  • Plunge into water and beer (charger swithed off).

*it’s the ultimate test to wreak havoc in the most expensive and highest specified PSUs around!

Nothing untoward happened and I was disappointed to not see the FAULT indicator light in some of the direst circumstances but heck the thing survived everything.