SkipD wrote in post #14183367
In my opinion (with an extensive electronics background), you'd be better off using the Sanyo charger because going to a rapid charger will run the risk of degrading the batteries much sooner.
If a temperature monitor is used NiMH batteries can be charged at rates up to 1C (in other words 100% of the battery capacity in amp-hours for 1.5 hours). At the 1C rate charging is completed 1.5 hrs.
Otherwise C/3.3 charge rate results in full charge in 5 hrs.
The least sophisticated way to safely charge a nickel metal hydride battery is to charge at C/10 rate or below (10% of the rated capacity per hour). So a 2000 mAH battery would be charged at 20 mA for 10 hours.
So when the charger allows a selection of Charge Rate, like 200 or 500 or 700 MA/hr, here is the relative safety...
- there is risk at the 700 rate unless there is a temperature sensor (2000 MAh / 500MA/hr = 4 hr).
- At the C/3.3 rate (5 hr.) it is safe if there is a voltage sensor circuit to detect voltage depression; this signal can terminate the charge if the battery under charge is only partially discharged. Measuring -dV/dt is the easiest because it doesn't require a temperature sensor; the best method for NiMH is the dT/dt method but temperature has to be sensed.
- The C/10 rate does not require an end-of-charge sensor and ensures a full charge with safety.
There are two advantages to a 'smart' charger even if it has marginal sensing for the higher rates...
- Being able condition the battery by discharging it to a certain level before going into charge mode
- Being able to charge one cell independently of another cell, so that cells do not have to be charged as a pair, where the more fully charged cell can prematurely stop the charging of the other one, when the first cell reaches full charge and triggers the sensor before the second cell is fully charged
The BC-700 does have temperature sensor in it. The 700 mA rate charges an AA battery in approximately 3.5 hours. It treats cells independently and can even be put in a different mode (charge; discharge; refresh; test) for each one. It can sense defective batteries, and it will not try to charge them