EMAG Battery Upgrade ?

[athomas]

650mA is the battery capacity. Instantaneous surge current capability may be more or less than that. That is why alkaline batteries won't work in an emag. They actually have higher capacity at full charge but cannot deliver the instantaneous current on demand that an emag requires. That is also the reason most aftermarket electro-frames won't work as well at high rates of fire. The batteries used, won't sustain the current required to operate the solenoid.

After checking the Lithium battery data sheets, I stand corrected. The lithium cells do not have the required instantaneous capacity to power an emag. NiMH it must be.:)

[rbreding]

So am I wasting my time with the extra 50ma ? Would it be that noticeable for extra runtime ?

[hitech]

Originally posted by rbreding
I assume that the 650ma batteries are being buffered by the capacitor then ?

I don't really know. Tom told me that the solenoid can draw up to 3 apms for a short duration.

Trying to replace the eMag battery pack (yes, it is a "bunch" of AAA's in series) is going to be difficult. Most battery packs have "matched" batteries and are tack welded together to avoid contact problems. You would be better off adding another battery pack in parallel.

[FalconGuy016]

battery memory IS a real thing that happens.... its not an everyday thing but its not like it only exists in satalites. It happens once you use batteries that get memory (ex.cadium) for a while.

[314159]

The Memory Effect Myth
Possibly the biggest myth that exists partcularly for NiCd cells is the "memory effect". Almost every one quotes it as the reason that cells have to be completely flattened - otherwise they develop some sort of memory, and can only hold a partial charge from there on. Like all good stories, this one has a grain of truth in it! The myth originated from the early days of satellites when they were using solar cells to charge batteries and because of the orbiting of the craft around the earth, the batteries were subjected to precise charge/discharge cycles many hundreds of times. The effect disappears when the battery cycle is suddenly varied, and it is extremely difficult to reproduce this effect even in a laboratory. So the "memory effect" is not a significant problem in home usage.
What I can tell you is while it may be OK to discharge individual cells to 0V, it is certainly not recommended to discharge an entire battery of cells. The reason is simple. When the battery is discharged below 0.8V per cell, one of the cells is inevitably weaker than the others, and goes to zero first. If the battery is further flattened this battery becomes charged in reverse, which again makes it still weaker. This creates a more common but less commonly known effect called "voltage depression". Eventually the battery's performance drops off quite suddenly which ironically is the very thing that the user is trying to prevent. Most users know where the battery's "knee" occurs; it is when the original equipment first starts to show signs that the battery performance (and hence voltage) is suddenly dropping, and it is a good idea to place it straight on charge at this point. Usually there is less than 5% of C remaining anyway.

One other thing, batteries don't like getting too hot or cold; they do not take a full charge and they actually discharge (even under no load) much faster when over 40 degrees or below 0 degrees. They can build up internal heat when working and this can cause temperatures inside to increase also. Particularly avoid leaving cordless tools inside a hot car for this reason. They also should be left to cool down for a while after discharge before placing them on charge. NiCd/NiMH batteries do self-discharge too, as a rule of thumb a battery will hold a full charge (with no load) for about a month or two, although when they get old or hot, they might only last a day.

So what can you learn from this?

You don't have to flatten your battery before you recharge it,
Don't flatten your battery below 0.8V per cell,
Don't overcharge your battery beyond 100% of C, and
NiCd/NiMH don't like to get too hot, or too cold (0 to 40 degrees C is usually best)

courtisy of http://www.angelfire.com/electronic/hayles/charge1.html