Michele,
Those 9V lithium rechargeables cost each about as much as THREE 9V NiMH ones (probably 4 because the eBay vendors who sell these usually don’t charge any shipping) and aren’t even double the energy content of the NiMH. You can get 300mAH NiMH cells. Yours are 450mAH. There are plenty of better 9V lithium cells out there that are 600mAh which is only 50mAH lower than a 9V alkaline non-rechargable that really don’t cost any more than what you spent for yours.
Also, 9V lithiums are usually 8.4V fully charged. 9V NiMH are usually 9V fully charged. A small difference but a difference.
A 300mAH cell is enough to keep a T-Rx running for about 4 days continuous. It doesn’t take nearly this amount of time to charge a 9V NiMH cell but then you’d have at least 8 of them for the cost of your 2 lithium batteries and with a dual charger (most are) you can keep 2 of them fully charged while using a 3rd so I really don’t see the benefit of spending the extra money.
Lithium cells do have one distinct advantage. Unlike NiMH and the older Nicad ones which have an internal discharge of about 10-20% of charge per month, Lithium cells internal discharge is almost negligible. A fully charged cell forgotten for a year in a room temp place will be almost still fully charged when you find it again. A NiMH battery will be quickly heading toward dead.
I use my T-Rx continuous when I’m poisoned or something funky is going on but usually only 2-4 hours per day otherwise. Seems to work just fine.
I have 2 SP’s – one Don so graciously gifted me and a second I built myself with a slightly smaller crystal -both running at the same time. This way, when I go out gifting I can take one with me and still have one running at home.
One thing I do want to mention about lithium rechargeable batteries as a warning (ALL lithium rechargables are like this including cell phone batteries). You CAN overcharge them so do use a good charger. A good charger will not overcharge them. You also need to let them trickle charge for a couple hours after the charging light goes out so they reach full charge. Because of lithium chemistry all quick chargers cut the quick charging off before the cell voltage reaches final value and there could still be 10-15% charge they need to get to full power. You can drain them too low where they can’t be recharged. What you need to look for are cells that are claimed to be “protected” or have a protection circuit in them.
Why? Well, lithium is funny chemistry. The cell needs to be carefully charged by the manufacturer to about 2.75V before you get it so it can be normally charged. If you plug a cell thats below this voltage (maybe 2.5V or so) into a rapid charger, not only could you permanently damage it, it could become dangerous and perhaps even rupture.
The protection circuit cuts-out the battery when the voltage gets too low so you don’t deplete the cell below the limit. Though with a good charger its not necessary, it also limits the charge current to something safe AND limits the discharge current to whats considered safe for the battery – the other thing about lithium cells – you should never draw more current from them than is recommended by the manufacturer. This too can damage the cell and cause issues. Built in protection circuitry prevents this from happening.
With the protection board inside the cell you can use it like a normal battery. Without it, you have to watch like a hawk so whatever you buy, make sure its “protected”.
I suspect 9V batteries are all protected because of how they’re used. Don’t make this assumption for any other cell configuration (AAA, AA, C, D or even some batteries that are a non-standard size to be used in flashlights and the like). If it doesn’t say “protected”, it most likely isn’t.
NiMH batteries don’t have any of these quirks albeit the energy density is about half that of a lithium battery but as I said, the cost differential is huge.
