Having worked with batteries and battery chargers during the last five years in the labs where I used to work, I thought I'd post some actual graphs of the charging process of some chargers that I own; the Optimate III and the CTEK MULTI US 3300.
I've read many reviews not so much for product information, but to see if the people reviewing the product actually had any background or technical ability to do so in the first place.
Answer: not really and most of them are laughable. For example, I contacted the people on WebBikeWorld about one of their reviews and they got downright upset that I would question them. Little wonder they got defensive since they knew SDA about electronics.
Then you have the average user who reports the battery charger they are using is great, and they are getting three years out of their batteries, the latter is nothing to write home about. Batteries should last about 10 years or more. Battery life does depend on a few factors though and while parked the important one is not letting them discharge which leads to sulphation if left discharged for any period of time. Sulphation is the number-one killer of batteries with heat and vibration being next. Of course, your vehicle's charging system has to be up to spec as well.
On the point of the much reported "it recovered my battery", I think the user should define what they meant by "recovered". I have yet to see a battery be recovered from a sulphated state to full spec of the battery. A battery that was drained due to leaving the lights on is not being "recovered" in my books, it is simply being recharged. And in most cases, unless fully discharged many times, that battery suffers little damage.
Here are the charging characteristics of the CTEK US Multi 3300.
This is what they claim. Note that they do not list any values.
And this is what my data acquisition unit measured...
The charging cycles after the battery has reached full charge were recorded using a data logger over a two-week period. The above is a one-day snap shot.
Nothing special. Once 12.867V was reached, the battery was placed under charge by the CTEK till 14.34V was reached. This would take 5 minutes for the "already fully charged" YUASA 53030 battery (12V, 30 Ah) at which point the charger would turn off.
After approximately 2 hours and 15 minutes, battery voltage would reach 12.867V again and the charging process would commence again.
It does not go into any "float" or "maintenance" mode.
And this is the charge characteristics of an Optimate III charger...
Note, the battery being charged was discharged to the 1/2 charged state to start the test.
Again nothing special.
In fact, it bulk charges and when it reaches 14.3V, instead of going into absorption mode, a topping up of the battery at constant voltage as the current tappers to near zero, it goes right into a float mode and cycles between 13.4 and 13.7V.
Having tested many upper end chargers at work, some costing over a grand, I have to roll my eyes to some of the claims and advertizing found in the brochures and on packaging. I would be skeptical of any till I tested them. The only one I found to be near perfect are the Xantrex Truecharge 2, but those are meant for the RV, boating and car crowd.
Of course, any charger is better than letting the battery discharge and sulphate. The point being made after reading so many trumpet blowing threads about chargers is, the differences between chargers are minimal at the price points we are looking at.