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Welch Allyn web site, saids something about max voltage, it is possible upgrade the ballast,B10N001, with 9-10 NiMH batteries?
I think 10 cells provide a max initial voltage of 14V!(is right?) too much for the ballast, would be be the ideal number 9 cells? my concern is the voltage.
http://www.walamp.com/lpd/markets/po...=9943960361230
The technical information in PDF format is no longer available in WA site. :(
I have 2 different Halcyon light heads that are now using NiMH. A 10w and an 18w. Both use 10 cell packs no problem. Even Halcyon uses 10 cell packs...and they use the same ballast for those as they do the SLA. The SLA have the same voltage as a 10 pack of NiMH...so no worries. Ever check your SLA pack voltage when it's fully charged? It should be 13.8-14.1v...same as a NiMH.
I'm pretty sure that WA lists nominal voltages on their website...and the nominal voltage for an SLA and 10 cell NiMH is 12v.
Mike
Ok, can you (or anyone) do this test for me. take your fully charged 10pack nimh batteries,and measure the voltage, which is the result?
I measured the voltage of both packs I have - which each have 20 4/3A 4500mah NiMH batteries(2 sets of 10 wired in parallel to make a 12v 9000mah pack). One was 13.45v, the other was 13.51v. These are both fully charged, but have been off the charger for several days. A pack fresh off the charger will measure ~13.8v, but will drop fairly quickly to 13.5v or slightly lower. Once you put a load on these packs(by turning the light on), the voltage will drop to 13.0v or less for an 18w, 13.2v or less for a 10w.
Just for kicks...I measured the voltage of my scooter batteries. They are 2 12v SLA batteries(just like what's in your light now, only much larger and higher amp hour ratings) wired in series to make a 24v pack. The voltage was 26.8v. I also checked each one individually...one was 13.5v, the other was 13.35v.
If you want to hear the same type of info from others that are also experienced with building such packs, sign up for the group "hiddivelights" on Yahoo groups. http://groups.yahoo.com/group/hiddivelights/ You have to sign up before you can read or post, though.
Mike
Oh, one more thing...if you decide to have a pack built, I suggest contacting Wayne at TNR Technical. http://www.tnrtechnical.com They're in Sanford(Orlando area). Very knowledgeable and have just about any small NiMH battery you could want in their warehouse. He will also build a pack for you...just give him the canister dimensions and he'll do the rest. I've had him build a couple packs for me when I just didn't have the time(or sometimes access to spot welding equipment)...he does excellent work. He builds NiMH packs for several of the manufacturers, too.
Mike