Which AA batteries can I use with my LD20 R4?

vinegar strokes · May 30, 2010

I'm new to these forums and to cool lights in general. The best torch I own is my Heser LED dive light, which I use as a backup in shipwreck penetration. It is an awesome light. But the best surface light I have is an AA Mini Maglite, which I know is pretty weak compared to the latest technology lights. I've just ordered a Fenix LD20 R4, and am confused as to which batteries I can and can't use.

I've tried to UTFSE, but the answers seem conflicting. I don't really care about rechargeables, since I will use the light mainly for travelling. But I am very interested in using Lithium primaries in my LD20. Some posts on here seem to imply that they will fry the emitter, or at least over-drive it and shorten its life dramatically. But even on Fenix's website, it states 'Uses two 1.5V AA (Alkaline, Ni-MH, Lithium) batteries'.

I can get six Energizer lithium primaries for about £5 from Amazon. I understand that they are more reliable, have a much longer shelf life, and deliver more power/longer burn time. I'd be really grateful for some advice on whether they are suitable for my LD20, and if so, how much advantage I would gain.

Thanks!

Stereodude · May 30, 2010

Energizer Lithium L91 AA's will not work fine in a LD20. The lower 2 levels end up the same as high. On the other hand, alkaline AA's will not work well for turbo or high. Take a look at the graphs in this 2xAA Round-up Review. I would recommend NiMH batteries or another 2xAA light like the 4Seven's Quark AA^2 if you want to use L91 Lithium batteries.

shark_za · May 30, 2010

If you absolutely have to run lithium AA's then you have bought the wrong torch.
It probably wont kill it but the lower 2x modes are lost and it works at one high level until the voltage drops a bit.
If you want Lithium compatibility in an almost identical method of operation get a Quark.

Don't discount rechargeables though. Good low self discharge NiMh cells power it perfectly and wont lose charge when not in use.
Cheaper in the long run and its a win-win scenario.

Im my neck of the woods 4x Duracell Active charge cells cost only $2 more than 4x Energiser Lithium L91's.
Even given capacity difference they pay for themselves in 2 charges.

Stereodude · May 30, 2010

shark_za said:
If you absolutely have to run lithium AA's then you have bought the wrong torch.

I didn't think this was the case since L91's work just fine in my fleet of Fenix L2D's (thought they had the same circuit) and in a 4Sevens Quark AA^2, but I just tried it in my LD20 (XR-E Q5) and much to my surprise the lower 2 modes are the same as "high".

RedForest UK · May 30, 2010

Eneloops!! :twothumbs Energizer L91's will not burn out the emitter, it is the higher voltage li-ion rechargeable cells that people on here will rightly warn you away from using. However, they are expensive, while they store roughly 7x as much capacity as an alkaline cell in a high drain flashlight, Eneloop/Duracell Active Charge Ni-Mh cells store 5x time amount as an Alkaline, hold their charge whule not in use unlike conventional Ni-mh cells and are rechargeable over 1000 times. Even if you only use them 20 cycles each then they will prove many times better value for money than Energizer disposables..

berry580 · May 30, 2010

could it be because L91 is too expensive to be used in the long term?

SirJohn · May 30, 2010

There are many threads about the LD20 that comment that anything over 3.0 volts in the LD20 puts it in direct drive (bypassing the regulation) and therefore the two lowest modes are gone. It only gives you high and turbo. Two L91's will put over that 3.0 volt threshold. It's not enough to damage the light any, but you just can't use the low modes when you use the lithiums. I just got my LD20, but do not have any L91's handy to test this. My plan is to use LSD NiMH's and just keep a couple of L91's in reserve for back-up. Te LD20 works fantastic on the LSD NiMH's so I would suggest you just use those. Not too mention they are quite cost effective.

Per-Sev · May 30, 2010

SirJohn said:
There are many threads about the LD20 that comment that anything over 3.0 volts in the LD20 puts it in direct drive (bypassing the regulation) and therefore the two lowest modes are gone. It only gives you high and turbo. Two L91's will put over that 3.0 volt threshold. It's not enough to damage the light any, but you just can't use the low modes when you use the lithiums. I just got my LD20, but do not have any L91's handy to test this. My plan is to use LSD NiMH's and just keep a couple of L91's in reserve for back-up. Te LD20 works fantastic on the LSD NiMH's so I would suggest you just use those. Not too mention they are quite cost effective.

I have some L91's I use in my Haiku and the volts are listed as 1.5 on the batteries is that incorrect or is that the minimum volts they put out. I don't have any thing to check them with but if they say 1.5 on the batteries then I would hope that they are correct.

Stereodude · May 30, 2010

SirJohn said:
There are many threads about the LD20 that comment that anything over 3.0 volts in the LD20 puts it in direct drive (bypassing the regulation) and therefore the two lowest modes are gone. It only gives you high and turbo. Two L91's will put over that 3.0 volt threshold. It's not enough to damage the light any, but you just can't use the low modes when you use the lithiums. I just got my LD20, but do not have any L91's handy to test this. My plan is to use LSD NiMH's and just keep a couple of L91's in reserve for back-up. Te LD20 works fantastic on the LSD NiMH's so I would suggest you just use those. Not too mention they are quite cost effective.

Well... It's time to eat crow.

I just tried it. My Fenix LD20 (XR-E Q5) does not work normally with brand new L91's. As you note, the lower levels don't work. My various Fenix L2D's and my 4Sevens Quark AA^2 all work fine with L91's.

I was under the impression the LD20 and the L2D had the same circuit, but apparently that is not the case. I keep a L2D Q5 in my car with L91's loaded in it for emergency use (and a spare 4-pack of L91's). It works normally with L91 lithium cells.

Stereodude · May 30, 2010

Per-Sev said:
I have some L91's I use in my Haiku and the volts are listed as 1.5 on the batteries is that incorrect or is that the minimum volts they put out. I don't have any thing to check them with but if they say 1.5 on the batteries then I would hope that they are correct.

They're not really 1.5V. They measure >1.7V (~1.75V) open circuit brand new. Under load they will drop a bit, but hold about 1.6V.

Per-Sev · May 30, 2010

Stereodude said:
They're not really 1.5V. They measure >1.7V (~1.75V) open circuit brand new. Under load they will drop a bit, but hold about 1.6V.

Thanks, I guess don't believe everything you read or everything they label.

SirJohn · May 30, 2010

Per-Sev said:
I have some L91's I use in my Haiku and the volts are listed as 1.5 on the batteries is that incorrect or is that the minimum volts they put out. I don't have any thing to check them with but if they say 1.5 on the batteries then I would hope that they are correct.

The 1.5 volt listed on the energizer lithiums is a nominal rating. Many of them apparently test at 1.7 to 1.8 out of the package. Of course as they run down, the voltage would decrease, so eventually they will run down enough where the regulation kicks back in and the low modes will work again. As I said, I haven't tested this myself, but this is what I've read from other posters here and other places.

rydude07 · May 30, 2010

Wow I did not know this either.

Sorry if this is off topic but :
I just bought a ld20 q5 and was planning on using energizer lithium ultimates with it (since I bought a lot of lithiums recently on sale) and was planning to buy a ld10 q5 to use lithiums in as well. So i assume it wont work well with the ld10 q5 too?

This totally sucks that on fenix's website, it says that lithium is ok as well, but in actuality...it isnt. Im really upset. :awman:

Maybe i should just return all my lithiums since it supposedly only works in my E01 and not a ld10 q5 or ld20 q5. OMG:shakehead Major FAIL.

selfbuilt · May 30, 2010

FYI, L91 lithium works just fine in the LD10 R4 (i.e. all modes are available). It is just the 2xL91 configuration in the LD20 R4 that causes the loss of the low modes. :shrug: This wasn't the case in the older L2D series.

So you could always pick up the the LD10 battery tube for use on the LD20 R4 and run in 1xL91 configuration. Otherwise, you will need to stick to regular alkalines or rechargeables in the LD20 R4.

Personally, I would go with eneloops and simply charge them up before leaving (with a spare charged set in your travel bag). This is how I do it with my camera before going on trips. In a pinch, you could always pick up alkalines on the road.

rydude07 · May 30, 2010

selfbuilt said:
FYI, L91 lithium works just fine in the LD10 R4 (i.e. all modes are available). It is just the 2xL91 configuration in the LD20 R4 that causes the loss of the low modes. :shrug: This wasn't the case in the older L2D series.

So you could always pick up the the LD10 battery tube for use on the LD20 R4 and run in 1xL91 configuration. Otherwise, you will need to stick to regular alkalines or rechargeables in the LD20 R4.

Personally, I would go with eneloops and simply charge them up before leaving (with a spare charged set in your travel bag). This is how I do it with my camera before going on trips. In a pinch, you could always pick up alkalines on the road.

So ld10 q5 is fine with lithiums but just not ld20. SIgh friggen fenix and their website saying that it is ok for the ld20. GAH

How come some other posts say that the ld20 works great on l91, and that you will only lose the low for a very short time and it will do no damage do the light?

Stereodude · May 30, 2010

rydude07 said:
How come some other posts say that the ld20 works great on l91, and that you will only lose the low for a very short time and it will do no damage do the light?

Well, it won't do any damage to the light because it doesn't have enough voltage for the LED to draw an unsafe level of current.

SirJohn · May 30, 2010

Right, according to everything I've read, it won't damage the light at all, it just bypasses the regulation circuit when the voltage is above 3 volts and turns it into a direct drive light until the voltage drops below 3 volts at which point the regulation circuit will re-engage. So you can use the energizer lithiums you bought, but you just won't have the two low modes until they are drained enough for the regulation to kick in. The 3.4 to 3.6 volts of two L91's is still quite a bit less than the 4.2 volts you are facing with a single 14500 li-ion cell. (obviously two 14500 cells in an LD20 would mean over 8 volts which would absolutely fry the light in no time.) What I have not found is anything specific of whether the cut-off is exaclty 3.0 volts are slightly above that at like 3.2 volts. I think I saw a post somewhere that said the LD10 and LD20 heads are listed for 1.0 volts to 3.0 volts, but I have not seen anything published anywhere officially. I'm sure one of the dealers out there would probably know for certain. Its sort of curious that Fenix does not make the cut-off a little higher, say 3.6 volts, to take into account lithium primaries, etc.

tre · May 30, 2010

I use Eneloops in my LD20 and everything is great. I loose the lowest mode on normal alkalines. never tried Lithiums.

rydude07 · May 30, 2010

SirJohn said:
Right, according to everything I've read, it won't damage the light at all, it just bypasses the regulation circuit when the voltage is above 3 volts and turns it into a direct drive light until the voltage drops below 3 volts at which point the regulation circuit will re-engage. So you can use the energizer lithiums you bought, but you just won't have the two low modes until they are drained enough for the regulation to kick in. The 3.4 to 3.6 volts of two L91's is still quite a bit less than the 4.2 volts you are facing with a single 14500 li-ion cell. (obviously two 14500 cells in an LD20 would mean over 8 volts which would absolutely fry the light in no time.) What I have not found is anything specific of whether the cut-off is exaclty 3.0 volts are slightly above that at like 3.2 volts. I think I saw a post somewhere that said the LD10 and LD20 heads are listed for 1.0 volts to 3.0 volts, but I have not seen anything published anywhere officially. I'm sure one of the dealers out there would probably know for certain. Its sort of curious that Fenix does not make the cut-off a little higher, say 3.6 volts, to take into account lithium primaries, etc.

If the cut off is 3.0 volts and i use 2 lithium primaries...that means it will do damage or what?

And this problem of bypassing is only for the ld20 and not the ld10 with primary lithiums?

Anyways, i just got some lithium primaries for my ld20 q5. When i first turned it on with the lithiums, you were right i could not tell the difference between low and medium mode. But that lasted for a couple seconds. Now it works just like it did on NIMH....I do not know if my lithiums are a new kind or modified kind but on the box it says improved. on the back of the box it says world's first AA lithium battery (1,5v). Sometimes when i turn it on, the low seems a little higher but from my naked eye, i am pretty sure that the medium is indeed brighter than the low.

Stereodude · May 30, 2010

Which Lithium AA's are they? Energizer has two kinds now (L91 & EA91). We've been talking about L91's.

LD10 doesn't have the problem because a single battery doesn't exceed Vf of the LED.

Which AA batteries can I use with my LD20 R4?

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