The Sanyo charger does not have an automatic shut-off when batteries are fully charged, because it is "timer-controlled", ie on until much later after ener preprogrammed time from. A timer, then, regardless of the state of charge of the loaded battery pack.
Something worse can not do that, than to overcharge him a rechargeable battery. And it does this device, because the built-in timer allows the inserted cells roast much longer than necessary. Luckily the Eneloops're quite hardy, but long do not by such a treatment, they achieve never the advertised number of charge cycles.
Explanation of the charging times:
The device loads AA batteries for 10 hours with a charging current of 250mA, which are for a 2500mAh Eneloop AA with a capacity of about 2200mAh. Of course "fit" these excess 300mAh not in the battery, but the battery heats up and radiates the energy again. This is precisely the strategy of such low loader: 250mA are a pretty low charging current, so that the battery must not heat up too much. But he is tormented unnecessarily about the charging time required addition. Older batteries with significantly reduced capacity logically be tortured even more. And when you insert a not fully charged battery, which means once an extension of the pain ...
When the AAA batteries is similar, here are 120mA for 8 hours administered, ie 960mAh or 110mAh overcharging for AAA with a capacity of about 850mAh. Again, the charge current is so low that no excessive overheating is to be expected, but the battery will also be tortured.
This charging strategy of low loaders, low charging current and long charging time, is purely a cost issue. So a timer is cheap, and the customer does not realize immediately that his batteries are treated badly and lose capacity soon. In contrast, the detection of the right switch-off when full charge is technically more complicated and also more expensive.
Do yourself and your batteries a good thing and buy a charger with recognition of the charge state, the so make off at FULL. You can use much higher charging currents, eg 700 mA in the Eneloop AA or 350mA at AAA, can a battery recharge at any time, even if it is not empty (harms NiMH not because there is no memory effect) have, even a "Refresh" program for, tired batteries.
If you still need a recommendation, enter a time BC700 into the search field. Or Gugeln a bit, there are also specialized forums on the subject.
