Can battery types be mixed during use

[vacuum3d]

For space and voltage constrains, I'm thinking of mixing Lithium and Nimh to make up ~11 volts to drive a WA1185. The type/capacity/voltage/current draw of the two kinds of batteries are different. My question is, would it cause any damage if I try to mix them? Am I out of my mind for doing that?


thx,
ernest

 

[andrewwynn]

you can't mix like you describe.. the lithium battery is going to charge the NiMH.... 3 NiMH add up to 1 LiON so it is just about possible you could use 3 NiMH in parallel with a LiON battery... kinda curious what you meant by mix.. you want to use like 2LiON and 2NiMH all in series.. no go.

11 volts... sounds like 3 LiON batteries = 10.8V. -awr

 

[Steelwolf]

Do not mix cells of different chemistries, sizes or capacities. Do not mix primary cells of different age or rechargeables at different discharge levels.

You could do it in an emergency, but you run the risk of damage to the cells, not to mention leakage causing damage to your light, or even minor explosions with Lithium cells.

Maybe you can describe the flashlight body you will be using and we can suggest a configuration that will work?

 

[vacuum3d]

Thanks for the info, guys. I was trying to come up with around 10.8v to drive the WA1185 in either 1D or 2D Mag. I can't fit 9xNimh in 2D. I was thinking about 2x14450+2xNimh AA using a 1D Mag. I remember someone, maybe Litho123, mention the of 3.5/123, which he explained as 3x123+1xAA. I just wanted to find out whether I could extend his idea a little by mixing Li-Ion with Nimh to come up with 10.8v to drive the WA1185.

Thanks,
ernest

 

[andrewwynn]

there is one possibility you can play with... fractional cells.. rechargeable cells will come in 1/2 and 1/3 sizes... well i guess that's still tough you need 9 1/3 cells to get the voltage you want.. \

what is a WA1185?

3 LiON cells will get you just about 11V.. you could get a 3toD AA and that'd fit in the space of a single D battery. with a little bit of work you could get two sets in parallel and more than double the runtime.

a single D battery has 27 WH.. 3 AA LiON batteries have 9WH.. but are rechargeable (and have 11V)... i'd be done looking i like the LiON batteries.. you can get 1.7W out of a single AAA.. 3AA LiONs can output 18W or so... but 9W is recommended max.

-awr

 

[vacuum3d]

Decisions decisions... /ubbthreads/images/graemlins/smile.gif
WA1185 is a 9.6v Halogen bulb that gives out 816 Lumens according to the spec. There are a couple of Group Buys going on. Just have to figure out a good way to power these little beasts.

ernest

 

[oldtimer]

Isn't it the 1169 or something that puts out 816 Lumens? I thought the 1185 gave like over 1000 Lumens.

 

[Steelwolf]

For a 2D body and 9.6V bulb which you're planning to drive around 10.8V...

6 AAA cells will fit in to the space of a D. Actually 7 will fit, but then there is almost no space for support structure (ie the battery adapter/holder). 6 is a comfortable fit. So you can get up to 12 in a 2D body. With NiMH, that's 14.4V. So you just replace 3 spaces with dummy cells and get a nominal 10.8V or about 11.7V fresh, but not hot, off the charger. You can get AAA NiMH cells that hold 900mAh. Nominal 9.72Wh. Don't bother with alkaline as they will not do well under such a load.

2 CR123 cells will fit side-by-side in the space of a D cell. 3 CR123 will fit within the length of 2 D cells. That allows 6 CR123 cells to be used.

Looking at primary CR123s.
6 cells gives you 18V total, way too much. If you run 2 parallel banks of 3 cells, you get nominal 9V. Not quite enough. So you need to run 4 in series for 12V. I'm not sure if that will blow your bulb though. With 1A drain, the energizer data sheet suggests that it can give 850mAh with nominal voltage of 2.8V per cell or 11.2V total. Nominal 9.85Wh.

Rechargeable 123s as available from Juice, JSBurlys, JayCar electronics, etc.
Nominal 4V, so you can get 12V from 3 cells. This means you can use 2 banks of 3 cells. Since the capacity is rated at 600mAh, this will give you 1200mAh in total. Assume that the nominal voltage through the run time is 3.7V as is usually specified. Nominal 13.32Wh

Looked at CR2 cells, thinking to put 2 banks of 4. Just slightly over the length of 2 D cells. Possible to implement if you don't mind cutting down the stock spring. But at 1A drain, nominal 2.8V per cell over discharge period of 0.37hr, so 8 cells would have nominal 8.28Wh. Not worth the trouble.

With luck and very careful work, sometimes you can squeeze in 4 AA cells in the space of 2D cells. It depends on which batch of Mags you got. 8 primary cells gives you 12V nominal, 8 rechargeables give 9.6V or 10V if freshly charged. This is your best option because any way you look at it, you not only get the best capacities, but also the widest choice of chemistries, with lithium and Ni-xx being able to deliver lots of amps without undue voltage sag or high internal resistance penalties.

Unfortunately it is highly dependant on the internal diameter of your Mag, though if it is too small, there are several members here with lathes. They can bore out the tube just enough to fit 4 AAs.

Hope all this information helps.

 

[vacuum3d]

Steelwolf : Thank you for the info. Since I only want to consider rechargeable batteries, it looks like either 3xR123 or 8xAA Nimh are my only choice. I might have to move up to the 3D Mag body and just use 9xAA Nimh as recommended.

b2p : I'm really not sure what exactly the 1185 puts out. I'm just stating what the WA site says. Even at 816, that's more lumens than anything I only at the moment /ubbthreads/images/graemlins/smile.gif


Thx,
ernest

 

[3rd_shift]

That high output bulb may be a problem for the plastic reflector.
You may actually want to go with something a little smaller.
Or, perhaps come up with a 6 nimh D cell adaptor for a lantern flashlight with a metal reflector.
Such a high output bulb is a high stress proposition for most flashlights and batteries smaller than this.