I'm an Electrical Engineer and I did my senior project in college on lead-acid batteries. You want to know what my favorite battery chargers are? The old-school full-manual ones, in amperages from 1A to 10A. I just gave away my heavy-duty roll-around 60A battery charger because I never use it.
Why do I like the older, 'dumb' chargers? Because they will charge completely dead batteries and older batteries that are near end-of-life. Most modern microprocessor-controlled battery chargers are too smart for their own good and are fooled by normal dead or old battery voltage behavior.
Perfect example - our !@#$% Honda Odyssey (save your Honda love for another thread) has developed the nasty habit of pulling the battery down to 4.0V in a couple of days of non-use (has happened three times in as many months). It's something in one of the electronic modules and I haven't been able to find the current draw yet because it's no longer there after I charge the battery back up. Maddening and now I know why people trade cars in . . .
At any rate, any new microprocessor-controlled charger will look at the 4.0V on that battery and not even recognize that it's actually a 12V battery and thus won't even attempt to charge it. So that's problem #1.
So if you have a 'smart' charger, you first have to use other means to get the battery voltage high enough that the charger figures out that it's OK to actually push some amps into the battery. What a pain!
Problem #2: smart charger is then fooled by high voltage that dead battery presents upon first accepting the initial charge, thinking that the battery is fully charged. So smart charger turns off too soon, and that's no good either. It is perfectly normal for the voltage to go really high at first, and then as the battery impedance drops, it starts accepting current and the voltage will go down (this can take several minutes or even longer for a really dead battery) - once this happens, you want to keep charging until it's completely done.
I select which amperage charger I will use based upon the size and estimated state of charge of the battery that I am trying to charge. I'll leave the battery on the charger overnight, and when voltage gets up to around 15VDC I disconnect the charger. It's not good to leave it at this high of a voltage for a long period of time, but for a few hours it isn't an issue.
So I would recommend look at yard sales, second-hand stores, and Craigslist and buy a few old-school manual chargers (I wouldn't pay more than $10-15 each). You can do a quick functional test with a 12V bulb to see if it lights up (a sealed-beam headlamp works great).
Now if you have really large batteries on construction equipment and need to charge in less time, that's where the larger 40-60A chargers really shine in getting the 'bulk' charge (the first 80%) done quickly. The 'finish' charge (the last 20%) always takes longer and requires much lower current, and the smaller, manual chargers mentioned above work great for doing that job overnight on both smaller and larger batteries.
Oh, having a good voltmeter is a must IMO - you can get a pretty good idea if you're done charging by looking at the ammeter on your charger, but that PLUS the voltage reading will tell you the complete picture. There is a ton of good information on lead-acid battery charging online so I won't repeat all of that here.
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Hey, I understand completely. Once you have access to that type of equipment on a regular basis, it's hard to imagine living without them. 