DIY EV Battery Charger

The last major item I need to find for my conversion is a battery charger.  Amazingly, I'm staying within my budget so far (detailed in my wired post), but I'll probably go over if I pay for a new charger.

Russco and Quick Charge make some decent chargers that are relatively affordable compared to nice but more expensive Zivans and Manzanitas.  But if I buy new, I'm still looking at at least $500.  I have heard of people making their own chargers and got curious about how difficult and expensive it might be.  All a charger really does is apply a dc current to a battery right?  How hard can it be?

I did a little digging and found some reasonable plans.  Building your own charger is most tempting when your batter pack's voltage is close to household voltage, as mine will be at 120V.  Household voltage is around 110V, and it is a relatively simple matter to convert AC to DC.  Small voltage modification can be achieved with an inductor to bump the 110V household to 120V or so that is the optimum charging voltage.

I was pleasantly surprised to see how easy and cheap this would be to do, and I have to say I am very tempted to do it.  I figure I don't have too much to lose, since I got my batteries for $5 each.  If I had spent thousands on the batteries, I might be more leery of subjecting such an investment to an experimental charger.

There are some downsides, however.  The main benefit of manufactured chargers is the managed charge.  Not only do they shut off by themselves when the batteries are full, but most of them also have a multi-phase charge profile which is better for battery health and maximum charge.

It wouldn't be too difficult to install a timer switch on the unit, and with a little time I could learn how much time to give the charger based on a given discharge. But the charger would have to be watched closely to make sure the batteries would never be overcharged.

I also don't think it would be terribly difficult to integrate some control circuitry and automated voltage monitoring, but with all that the project would grow to be much more complicated.  I think it would probably still be cheaper than the manufactured chargers, but I need cheap AND simple.

I've also heard of "Capacitive Chargers" that will charge any voltage pack (more of a trickle charge), and can be made from very cheap parts.  Wilderness EV says they work well and sells them on their site.  I can't find much more information on them though, and it almost seems too good to be true.  Anyone have information?