Hello Flatshovel,
Welcome to CPF.
The standard that the battery manufacturers use requires that cells survive 500 cycles being charged at 0.1C for 16 hours, and being discharged at 0.2C down to 1.0 volts, under standard laboratory temperature and humidity. A 0.2C discharge should empty the cell in 5 hours, and the standard calls for the cells lasting at least 3 hours in order to satisfy this specification.
If everyone had lots of time for charging, and only required a 0.2C discharge rate, we would be using the standard charge all of the time.
The hobby industry has shown that cells are more vibrant in use when they are charged at, or above, the rate that they are used. This has pushed the charging rates up, and the pendalum went so far that there were some battery packs that blew up causing some damage to some people. This ended up with charger manufacturers suggesting that the maximum charge rate should be 1C, although many people involved in RC find that they get better performance when charging at 2C.
The problem with higher charging rates is temperature. The cells heat up during the charge, and heat breaks down the electrolyte in the cell. The key to high charging rates is charge termination. If you can stop the charge before heat damage is done to the cell, you can charge at higher rates without cycle life performance degradation.
In fact, an alternate way of standard cycle life testing involves charging and discharging at 1C over most of the charge/discharge cycles. This cuts down on the time it takes to test a batch of cells, and many manufacturers use this accepted alternate method of testing.
This means that you should be able to get 500 cycles from your cells charging them and discharging them at 1C. The key, as others have mentioned, is reliable charge termination. Now the variable of the charger comes into play. A high quality charger will properly terminate the charge before damaging the cell, most of the time. Low quality chargers will do fine with vibrant cells, but may have difficulties with well used, or crap, cells.
Unfortunately, cycle testing with all the various chargers is impossible to do. There are too many chargers, and the process is very time consuming. I did run some tests on the Energizer 15 minute charger, and found that vibrant cells lasted around 150 cycles. Keep in mind that is being charged at close to 4C. The cells did get hot during the charge, and this did result in reduced performance.
This indicates that you are right. Fast charging (15 minute charging) will reduce your cycle life to around 150 charge/discharge cycles. However, a normal charge rate (60 minute charging) is actually listed as an alternate cycle testing that the battery manufacturers use will give you over 500 charge/discharge cycles, IF proper termination is used. Beyond this, slow charging (0.1C for 16 hours) is the standard.
The -dV method of charge termination is used by most charger manufacturers. In reviewing the -dV signal, the battery manufacturers state that the strongest signal comes when cells are charged in the 0.5C - 1.0C range, but they list most of their test results using a 1C charge rate. With the increase in cell capacity, the charger manufacturers have had to find other methods of terminating the charge because it would be too expensive to manufacture a "cheap" high output charger, and then it wouldn't be suitable for cells of differing capacities.
The charger manufacturers have a difficult task. They are working within price constraints and still are trying to find a good method of charge termination. They don't feel that the market will stand a charger that comes with a 50 page instruction manual and costs $100. Also there are liability issues associated with a more complex piece of equipment. Since most people place value on price and ease of use, they try to put together an affordable package that does a reasonable job of charging the cells.
The answer to your question depends on the performance of your charger.
Tom
