Surefire B90 Battery

trooper1954 · Feb 6, 2014

Hello all...I have an older (20+) Surefire 8X that has the Surefire B90 battery. It is an NiCd 1800mAh 3 stick 3.6v, and will no longer hold a charge for more than 5 minutes even after a 24 hr charge cycle. Even tho lifetime guaranteed and discontinued, Surefire will not ship a replacement to Canada.
My questions are:

1. Can I replace this with a 3 stick NIMH battery of the same voltage and mAh?
2. Can I replace this with a 3 stick NiMh battery with a higher mAh rating?
3. Can I replace with 3 separate 1.2v batterys of the same mAh rating?

Thanks for any and all advice.

SilverFox · Feb 6, 2014

Hello Trooper1954,

Welcome to CPF.

To answer your questions... Yes, Yes, and Yes.

Your best bet is to go to NiMh cells, but there is an issue with bringing the negative terminal from the last cell to the top of the pack so the 8X makes proper contact. Actually the 8X may be more forgiving on this than the 8N but you need to check it out to make sure.

If you go higher capacity you will need to double charge the battery pack to get a full charge. One way to do this is to put the battery on the charger and set a timer for 1 hour. At the end of that hour pull the battery and re-insert it. You should then end up with a battery that is fully charged.

Tom

trooper1954 · Feb 7, 2014

Thanks Tom for such a quick response...just a few more questions:

Hello Trooper1954,

Welcome to CPF.

To answer your questions... Yes, Yes, and Yes.

Your best bet is to go to NiMh cells, but there is an issue with bringing the negative terminal from the last cell to the top of the pack so the 8X makes proper contact. Actually the 8X may be more forgiving on this than the 8N but you need to check it out to make sure.

Surely if I purchase a 3 stick NiMh it will make contact....are the batteries not the same configuration?

If you go higher capacity you will need to double charge the battery pack to get a full charge. One way to do this is to put the battery on the charger and set a timer for 1 hour. At the end of that hour pull the battery and re-insert it. You should then end up with a battery that is fully charged.

Really not clear what you mean here...I have the original C300 charger that came with the 8x...I don't think this will work to charge NiMh...what charger would you then recommend?

Thanks so much.

SilverFox · Feb 7, 2014

Hello Trooper1954,

I use the 8N and its plastic body doesn't allow for a ground path from the back end of the battery. The lamps have both ground and positive connections that are provided by the top end of the battery pack. The 8X may allow for a ground return but that is not the way it was designed.

I put together a project a few yeas back. Do a search on "Twice the run time and brighter" to find that discussion. The C300 charger works fine with a NiMh battery but it times out before the NiMh battery gets fully charged. The cells I used were 3700 mAh and we found that it took 2 charge cycles to completely charge those NiMh replacement batteries.

Tom

yellow · Feb 10, 2014

check the light + the battery and You will immediately notice, what SilverFox means with that negative terminal.
In short: You have to get the negative contact UP "around" the postive one - the body of the light does not do anything electrically.

I dunno how often I have posted my guide to making a battery stick for 8X/9N already but am not able to find one of them,
so typed here once again:
;)

* get a 7.2 V "Racing Pack" consisting of
* if possible try to get one, where the 2 "rows" are already "fixed" (explanation below)
* cut away "in half" the 2 row, at negative side at best
* bend whatever remains at the positive end so that the cell/stick reaches the length that is needed,
* put in an isolation disc at the top end so You can place the negative contact
* place negative contact and glue in
* put shrink wrap over
* done
;)

* if You want, You could solder in a "click contact" like with the original battery - salvaged from a 9V battery holder
(but when using a simple rubber band over the chargers contacts, that will work the same ...)

Explanation to Racking pack ...
when You look very closely "between" the cells at the racing pack, You see if there are simple flat metal bands making contact between the cells - thats "loose" and You will have to somehow glue the cells together before going on with the negative contact.
Hot glue gun or simple epoxy glue recommended
but when lucky the individual sticks are connected quite tightly - You will not see the bands then - and You do not have to glue the cells together to have the final battery stick rugged.