My wife is a dentist, and she has a $500 light called a Lumident. A couple of weeks ago, she showed me the charger for that light, which had been damaged by someone rushing around and banging it around. She had called the manufacturer, and they wanted to charge her about $40 to ship out a new charger.
I looked on the label of the damaged charger, and it had the following information on it:
Output 8.4dc 1.2A
And a symbol that shows the positive (+) side is INSIDE the power connector, and the ground or negative (-) is on the outside of the power connector (power plug).
This was the important stuff. This tells me that the charger works everywhere -- US, Europe, Japan, etc (Input 100-240Vac). More importantly, it told me that I needed to find a charger that has an output of 8.4 Volts, and puts out 1.2 amp.
Looking online for "8.4V charger", I saw dozens of AC adapters that were designed to charge Li-ion batteries, and were rated for 8.4V. All of them were only rated for 1 amp, not 1.2 amp. I went ahead and bought one from Amazon, and one from Ebay. The replacement ones looked exactly like the Lumident.
The one from Ebay was supposedly from a US seller -- but instead, it turns out that the seller lied and is shipping the charger from China. Two weeks later, I am still waiting.
The one from Amazon arrived promptly as promised. Here's the label:
I tested the voltage on both chargers. The original one put out 8.4Volts. The new one put out 10.4 Volts. I've noticed that most chargers put out a slightly higher voltage than what their label states. This is fine; most electronic gadgets can accept slightly higher voltages to work. The opposite is not always true.
The power connectors looked different, but they actually had the same measurements, and the inside wire was indeed positive.
I was concerned that the new power adapter put out only 1.0 amp, but then I saw my wife's Lumident gear. It turns out that the chargers are not meant to power the light directly, but to charge the battery packs that then power the lights. This is great. This means that a charger rated at 8.4 Volts will charge the battery packs, no problem, even if it has a lower current (amperage) flowing out of it. It will just take more time.
If the charger was used to power the light directly, then using a charger rated at 1.0 amp rather than 1.2 amp might mean that the light is not as bright as it should be. This would have been a problem.
I did not notice the other information on the original charger, which would have made things easier if I had. If I had noticed, then I would not have been concerned about the current (amperage) of the replacement charger at all. Anything near 1 amp would have been fine.
Class 2 Battery Charger
Smart Charger for Li-ion BAttery Pack
Charge 2 cell Li-ion battery, rated 7.4V, max 30Ah, min 1.2Ah...
The original charger is labelled as a smart charger. This likely means that it turns itself off after fullying charging a battery pack. With the replacement charger, the user might need to unplug the charger after noticing the battery is fully charged, or put the charger on a timer.
Hopefully the above helps someone replace an AC charger without paying a ridiculous amount.