Alright, this is an oldie, but I'm finally going to try it. Tonight I was on my way home from a meeting and it was pouring. The poor Metro's lights are noticeably dim when running at 12V (vs 13.5-14.5 with the alternator hooked up) so much so that I usually just run around with my brights on to see on country roads.
So when I got home, I dug up this little dc to dc converter I got a while back for some random project. It takes 11-14V input and boosts it to 15-24V. I'm going to install this on at least the ignition circuit to boost the voltage back up to more normal operating voltages.
Why do this? Well, first off headlights are annoying DIM at around 12V as mentioned already. Second, there are other efficiency penalties associated with running lower than nominal voltages.
Orange4boy noted this a few years back.
Thankfully, the alternatorless benefit overshadows the penalties, but why not have the best of both worlds? This solution I actually
posted about in 2009.
I'm sure a few people have run with the idea, but I don't recall anyone specifically documenting it.
I'm going to start by boosting the ignition coil voltage from 12V to ~15V. As mentioned, normal operating voltage is 13.5-14.5V. By running at 12V, the ignition coil is putting out 11-17% lower voltage to the spark plugs. A quick google says that most ignition coils run around 40,000V output. That means I'm loosing 4400 to 6800 volts by running lower voltages.
So, lets get on with it! Above you can see the dc-dc converter. Its a cheap Chinese piece I got off ebay. They're about $10 if you search for laptop car adapter or something like that. There are actually cheaper ones now for about $5 shipped that handle more power.
I cut the connectors off of it and crimped on some blade connectors. It'll be all be taped up to protect from any water. This also allows easy removal for testing and/or if it fails in the future.
This is the connection point. Its right before the ignition coil, so the install is quite simple. Snip the wires, crimp on connectors and plug in the dc to dc converter.
More to come...