Batteries for LED calcs, revisited

[mdunn]

I previously posted about my LiPo HP35 replacement battery pack. Not wanting to repeat the effort of machining a wood holder and building a regulator circuit for each of my recent acquisitions (45 & 67), I went looking for LiPo cells that would better fill the battery space in the calcs. Sure enough, poke around on Amazon, say, and you'll find LiPo cells of just about any size. I ended up with 2 AH cells labelled 104245, which seems to be a standard naming convention, i.e., 10×42×45 mm. Combined with a bit of foam, the cell fits snugly in the battery bay. The only work required is attaching some sort of contact. I have thin adhesive Cu foil, which works well. See the attached picture.

BTW, I don't have any AC adapters, and wouldn't recommend using them to charge LiPo. You should use a proper charger or a lab supply.

Still to try: 3AA & 3AAA battery holders w/NiMH...

   

[Hans-Peter]

Where is this Lipo to buy?
Can‘t find on eBay.

Hans-Peter

[mdunn]

I got this one:
https://www.amazon.ca/gp/product/B0798CRVM9

[burkhard]

Looks neat, but I don't get it. What does that offer over a more conventional aftermarket NiMH 3-pack offered by several sources on eBay and elsewhere?
The NiMH:
1. Has similar (or higher) energy capacity to LiPo.
2. Drops right in using the OEM HP battery contacts in the compartment. No special jumpers or adapters.
3. Recharges with the HP charger (or via a special USB cable sold nowadays). No special off-board charging rig-up required.
4. Price is similar to this LiPo.
5. Unlike LiPo, NiMH don't (often) burst into flame.

Maybe I'm wrong or missing something, but I se LiPo batteries as a good way to maximize energy density in odd available shapes (wide and flat, log and thing, &c.) That's great for a new design of a super-compact phone, but if you have an existing device designed to fit AA form factor batteries, why go LiPolymer? What is it providing over off-the-shelf NiMH solutions?

[mdunn]

Hey, do whatever makes you happy. The LiPo here is one half to one third the cost of the NiMH packs. And all the "high capacity" (≥ 2 AH) NiMH AA cells I've had experience with have had very short lifespans, whether you use'em or not.

[burkhard]

(07-01-2018 10:06 PM)mdunn Wrote:  Hey, do whatever makes you happy. The LiPo here is one half to one third the cost of the NiMH packs. And all the "high capacity" (≥ 2 AH) NiMH AA cells I've had experience with have had very short lifespans, whether you use'em or not.

Yup, just trying to figure out your angle... I haven't run through a ton of cycles on my NiMH packs yet, but so far they have been OK. I'll definitely check the lifespan, thing though.

The cost claim is hard for me to figure out, but I think you earlier listed a Canadian eBay on the LiPo, so maybe that's where you are and shipping across the border for NiMH factors in.

LiPo do give me the willies, though, especially if they are being charged unattended. They "count on" some reasonably sophisticated pack management controls. I don't have your original thread link handy, but I'd personally avoid open-loop charging. Too many of them catch fire without a lot of warning.

[Dieter]

(07-01-2018 10:06 PM)mdunn Wrote:  Hey, do whatever makes you happy. The LiPo here is one half to one third the cost of the NiMH packs. And all the "high capacity" (≥ 2 AH) NiMH AA cells I've had experience with have had very short lifespans, whether you use'em or not.

This sounds like you haven't tried Sanyo/Panasonic Eneloops yet. They are available in size AA and AAA, the AAs in both ~2000 and ~2500 mAh. I think these are very reliable cells, and they have virtually no self-discharge. Charge them now, put them in a drawer, get them out one year (or more) later, and they're ready to go.

There are other brands that offer similar batteries, but I can't say anything about these. Why bother when you can get the original, genuine and reliable solution from Panasonic? I bought mine in 2006 (at that time from Sanyo), always charged them in a decent smart charger, and they still work fine. Not just in calculators, but aso in much more demandig devices like flash guns.

Dieter

[rprosperi]

(07-02-2018 02:00 PM)Dieter Wrote:  This sounds like you haven't tried Sanyo/Panasonic Eneloops yet. They are available in size AA and AAA, the AAs in both ~2000 and ~2500 mAh. I think these are very reliable cells, and they have virtually no self-discharge. Charge them now, put them in a drawer, get them out one year (or more) later, and they're ready to go.

There are other brands that offer similar batteries, but I can't say anything about these. Why bother when you can get the original, genuine and reliable solution from Panasonic? I bought mine in 2006 (at that time from Sanyo), always charged them in a decent smart charger, and they still work fine. Not just in calculators, but aso in much more demandig devices like flash guns.

Dieter

I agree with Dieter, Eneloops are one of those rare products that really do live up to both the manufacturer's claims and their word-of-mouth reputation. They just work and essentially don't self-discharge (if properly charged with a smart charger like the BC-700).

For Woodstocks, these are perfect.

For Spices, they are a bit too long, and depending on the condition of your batter contacts, could damage them, so I use flat-top cells here.

[Removed my own stupid suggestion to have a classic battery pack made from AA Eneloop cells. Can't really be done as the classic charger and power supply are 'dumb' and would not properly monitor/charge the Eneloop cells in-place. So using the existing battery holders for AAA cells is the best option for Eneloops.]