Battery Pack Question

[Cedar-Acres]

This may be a dumb question... Does the rechargeable battery pack cover open? It looks like it does just like the spare pack but it wouldn't slide and I didn't want to force it. I just wanted to take a look at what batteries were in it and see how hard it would be to replace the rechargeable cells once they started to go bad in time.

 

[Larry (IL)]

There is a little bit of glue holding it shut, but you can work with it and get it open.

 

[earthmansurfer]

Mine opened pretty easy, I just had to pull the plastic lip enough to clear the edge (like with the regular pack). Then it mostly stopped about halfway or less when it "hit" that resistor or something like that. That was when I realized it wasn't just a regular pack with rechargeables in it! I closed it back up and haven't opened it since.

I take it that if we put rechargeables into the alkaline pack and used the White's charger that it wouldn't know when to shut off as I think it senses the heat??? (In addition there is a reason the stock rechargeable pack has that resistor like thing in it.)

 

[Rob (IL)]

Yes it does, but as Larry said there are small dabs of glue, you can see them. Why do you want to open it? ROB

 

[Larry (IL)]

The alkaline pack will not fit in the charger anyway, at least not go all the way down to make contact with the terminals.

 

[Cedar-Acres]

Yes it does, but as Larry said there are small dabs of glue, you can see them. Why do you want to open it? ROB

I have an electronics background and just wanted to see how it was put together and what cells were used. I know that in time one or more of the cells will degrade to the point the pack won't hold a charge and it would be much less expensive for me to just replace the cells.

 

[Rob (IL)]

There are 8, 1800mah NIMH cells in a heat shrink pack. You can't put in 8 loose cells like those in the alkaline pack because it doesn't have all the contacts to hold the loose cells. If you snapped in extra contacts it would be a 1 minute job to pop in 8 - 2500 mah cells.

The pack looks like this except for the battery clips.
http://www.findmall.com/read.php?66,995136,1173821#msg-1173821
ROB

 

[Cedar-Acres]

I opened the pack last night and saw what is in it. I can get tabbed cells to build a new pack when the time comes. I also determined what the 3rd contact was for. Thanks for your input.

 

[kyledfx]

what is the third contact for? igot a dead dfx nicad pack id like to convert.

 

[Rob (IL)]

For the thermistor to control charge.

 

[Cedar-Acres]

The thermistor is connected between the 3rd (center) contact and the negative contact. I haven't measured it yet to see what type it is.

Is the thermistor used to control the charge rate or is it used as an over temperature safety shutdown? Most chargers I have seen that use a thermistor use it to shutdown the charger if the battery temp goes over a predetermined limit.

1 Thermistor (Digikey PN 615-1016-ND 80 cents each)

 

[Rob (IL)]

I gave you the information in the link in this post. It shows the thermistor and part number. When the pack reaches a certain temperature is how the charging is regulated. That's why in the build moving the thermistor changes the final charge voltage.

 

[earthmansurfer]

I gave you the information in the link in this post. It shows the thermistor and part number. When the pack reaches a certain temperature is how the charging is regulated. That's why in the build moving the thermistor changes the final charge voltage.

I guess this is connected - I would measure the voltage after I charge the pack (15 or so minutes later) - usually around 10+, never 11. If I put it back on later on I could up the voltage another 1/2 or so, sometimes to 11. That could be helpful if you are planning on hunting longer.