Jornada 7xx battery rebuild Q's

i've read through the few battery rebuild threads, but still have a few questions. i've been looking at a few 18650 batteries and found a pair that i like. they are 3.6v 2600mAh. so they should provide quite a bit of juice seeing as how i'll be using two of them per pack. the only real question i have is do the batteries need an over charging protection circuit built in? it seems like half of the new batteries have an overcharge circuit built in. did the stock jornada 7xx have a built in protection circuit?

Thanks

seeing as how i got no answer, i went with some unprotected sony 2900mAh batteries. 36hr battery life here i come! it seemed like the best bet as the stock batteries are sony and don't appear to have overcharge protection. i'll let you guys know if they explode...

There are several methods HPC use to prevent overcharging. The most common method is a thermal switch cutoff circuit. It is a small sensor that opens the charging circuity automatically by the heat generated in the battery during recharging. For these batteries, it is important that the cutoff fuse is secured to the battery cell, otherwise it can't sense the temperature difference.

Other units use a reverse bias sensing method that can tell when the charge is slowing down to a certain point by sensing internal resistance. It isn't the best method, and probably a holdover from the old NiMH days...but it works and cuts off the charging at a prespecified level. As the LION cells degrade however, so does the ability to recharge them properly as the charging circuitry can't tell how good a battery really is.

Others use terminal voltage levels to prevent overcharging. These are pretty accurate, but the problem here has to do with people who use a/c adapters that don't supply enough voltage. Low voltage in a LION cell can cause problems too as most batteries also have low voltage sensors that prevent a battery from totally depleting itself, thus making it difficult to accept recharge in the future.

I can't speak for Jornadas as I've never rebuilt any of their battery packs...but for the Mobilepros...they use the thermal method, so straight batteries work well for them.