Although Elektor’s DIY projects for battery chargers have been numerous, famous and sometimes hilarious, that should not be a reason to ignore what’s out there in the shops for very little money. In fact everything you have read over the years on battery chargers (the ones you never got round to building) may have accumulated into a solid mistrust of dirt cheap products in automotive stores, on the web and in Little China. It’s the “no-way-that-can-work-for-that-price” one-liner so often heard from seasoned electronic engineers always aiming for the top notch, but everyone else grabbing the product and finding little wrong with it.

I  own two motorbikes, a 1985 650cc Honda Nighthawk, and a 1956 250cc Sparta ILO Twin two-stroke. The latter is rare and worth 5 times more than the Japanese bike, which is my summer commute vehicle. The bikes are worlds apart to ride but share a terrible ordeal in terms of the vehicle battery and especially the charging. The Honda has a 12-V 14-Ah lead-acid battery which gets a rough treatment from the vehicle charging system if you can call it that — like draining the battery at 10 A if the engine runs below 2000 rev/min and no way you can turn off the 75-watt vehicle lighting! The 6-V (yes!) dynamo and charging system on the vintage Sparta is so weak and badly regulated that the 6-Ah battery just about discharges while riding with the 45-watt headlight on. If in addition I decide to press the brake pedal, a 10-watt lamp comes on and I am a full ampère in the red. The 6-volt DC claxon on the Twin has a fantastic effect on the audience but sound it too much and you won’t reach home.