My lights came with a 4.04V charge and much quicker than your order did. Here's what I'm doing.
I ordered a 0V-15V (2A max) variable voltage power supply off Amazon for like 40 bucks. I got some banana clips too, so I can clip directly to the battery and put my meter in line for a more accurate reading than what the power supply meter would have.
You want to just pop off the battery case top, the + and - are very clearly marked. Slowly take your voltage up to 4.8V if your batteries are really dead, but DO NOT leave them alone. If they get warm, drop down to 4.7V, or even 4.5.
Anything above a 2.15V per cell will charge the battery. These are 2 cell batteries, hence the 4.3 volts at full charge. The extra voltage will clear any sulfide off the plates. Just don't go up to 5V like the manufacturer does with their chargers. That charges the batt faster, but kills battery life. Best bet is to charge between 4.5 and 4.7 volts. Every 3 months take it up to 4.8V and monitor it to clear the plates. This will get you a lot more battery life. Just do it for a while, until they get just a little warm.
I plan on leaving mine on 4.5V for say a week at a time, once a month wether I use the light or not. Then every 3 months take it to 4.8V for maybe a half hour or so.
Don't bother with charging through the cap light, that stuff is too close together and if it shorts out and you aren't there, you'll have a big mess.
For more info, go to
www.powerstream.com and that should help you. Go to "technical resources" on the left. I Don't have my power supply yet so I'll let you know how I make out.
And if you read this then burn your house down, Banks forced me to write this.