1.5 volt lithium D cells

[Steelwolf]

[ QUOTE ]
Gadget Lover:
OK, I've seen the CRV3 (a 3 volt lithium the size of two AA side by side) implemented as two 3 volt AA sized cells permanently wired in parallel. I thought that was a "no-no" due to the possibility that one cell may be weaker than the other or short out and cause the good one to discharge.

[/ QUOTE ]

Wiring in parallel is fine. They balance each other out. It is wiring in series, especially when there are a lot of cells in series, that one runs the risk of reverse charging.

Think about the logic of it. I tried to write down an explanation but it couldn't do it without illustrations. Sorry.

 

[gadget_lover]

I think steelwolf is thinking of reverse charge whereas I'm thinking of the bad one draining the good one as the good one tries to charge it. There was a thread about one of the underwater kinetics lights that has a parallel setup. It was an interesting thread because the bad cell generated hydrogen when it was "charged" by the good cells. Loud noises and flying parts happened when the spark from the switch ignited the gas.

So that was my concern here. It's quite possible that the CRV3 uses matched cells to make sure one is not weaker than the other. It may simply be that it's a non-issue with modern lithium sisulfide cells.


Daniel

 

[gwbaltzell]

Chemistry of the cells is Lithium-Manganese Dioxide (Li/MnO2) not Lithium Sulfur. Lithium Sulfur has a few more risks. Lithium Sulfur, as I understand, are under pressure that gets higher as the cells discharge. As primary cells (CRV3), I doubt if any extra steps are taken to match them. They are not rechargeable.

Recharging other chemistries in parallel might result in a more balanced charge if the cells are good.

edit: Note that many manufactuers put a PTC (positive temp. coeffecient, thermistor) device in each lithium primary cell to limit the current it can deliver. Note also they can still deliver plenty to cause burns or a fire.

 

[gadget_lover]

[ QUOTE ]
gwbaltzell said:
Chemistry of the cells is Lithium-Manganese Dioxide (Li/MnO2) not Lithium Sulfur.

[/ QUOTE ]


I wasn't even close. I was actually thinking of the chemestry in the L91, which is something else altogether. Lithium /Fe?


Daniel

 

[Tweek]

Yep, L91's are lithium-iron... /ubbthreads/images/graemlins/smile.gif

Chris

 

[Steelwolf]

I see what Gadget Lover is getting at. Thanks. Yeah, I was thinking of reverse charging. I don't really know which is worse. Reverse charging, which is a common-place risk in any battery, or just straight charging which is a risk in parallel setup. Afterall, you always see the warning on primary cells about risk of fires, burns or explosion if recharged.

 

[bindibadgi]

Actually, the rechargables are Lithium - ion.

Cool batteries, with no memory effects! Better charge to wheight ratio (charge density - whatever you want to call it) too.

 

[JimH]

Hey bindibadgi, want to get rich - come up with a lithium-ion D cell.

 

[fivemega]

I have used this battery adapter for 4x14500 Lithium-ion batteries which are same size of AAs.
Nominal voltage of 3.7 @ 2600 mAh in size of D

 

[PeLu]

[ QUOTE ]
JimH said: want to get rich - come up with a lithium-ion D cell.

[/ QUOTE ]

Why another one? What is bad with the existing Li-Ion D-cells?

 

[Mark_Paulus]

Nothing is wrong with them, that I know of. Except, Where can you find them for "consumer purchase"? I am not a manufacturer, and I don't need 1000's of them to be able to buy in bulk lots, and I can't find them 1sy or 2sy to buy.

 

[fivemega]

Is there such a thing existed D size Lithium-ion batteries?
I never seen those. Any link?

 

[Tweek]

Yes, I myself would very much like to see a li-ion D cell... /ubbthreads/images/graemlins/smile.gif The only lithium D's I've ever seen were all primary cells, not rechargeable...

That'd be a group buy I'd be really interested in... /ubbthreads/images/graemlins/grin.gif

Chris

 

[PeLu]

[ QUOTE ]
fivemega said:
Is there such a thing existed D size Lithium-ion batteries?

[/ QUOTE ]

I wrote about D-sized Li-Ion cells, not batteries, I don't know about any of the latter ones, but cells are made by SAFT. As mentioned above, they are not too easy to get, as SAFT (like many other companies) does not want amateurs playing with it. I could ask my usual source where I buy my SAFT cells from.
SAFT Li-Ion D-cell datasheet

 

[Tweek]

Interesting, but the capacity figures don't seem right for the physical size. They work out to be just a little more total energy than a Maha 11AH ni-mh cell. Lithium-ion should be able to get more that 4.6AH into that big of a can. My guess is there's three 14500 cells in parallel inside the casing, and something similar using 14430 cells with the 4/5D version. That adds up just about perfect with commercially available 17500 and 17430 cells' capacities (1500mAh and 1200mAh, respectively).

But at least they're making progress. /ubbthreads/images/graemlins/smile.gif

Chris

 

[PeLu]

[ QUOTE ]
Tweek said:
Interesting, but the capacity figures don't seem right for the physical size.

[/ QUOTE ]
Chris, capacity is not everthing and different companies have different ratings.
The companies who aim at the mass market with lots of uneducated customers, just try to get the highest numbers and are sometimes (if not always) not honest getting them. If you buy an 2300 mAh AA cell, they only gurantee you that the cell will not exceed this capacity .-) (just in case: this is a joke)
The professional market is different. There are so many more attributes to care for. And the buyers appreciate it and are even willing to pay a much higher price for it.