Painfully boring technical question re. rear lights and rechargeable batteries

[presta]

Presumably the 2.62v value is that between fully-charged and cutoff voltage

The average of the two limits you quoted.

Alkalines which I think potentially have more capacity

Not necessarily, the voltage of alkalines varies much more that NiMH throughout the discharge cycle, and the source resistance is both higher to start with, and increases more during discharge. At 250mA load, the source resistance will be losing you something like 0.13V. I've known duff batteries have a voltage that looks good, but high resistance.

Both of which appear to be 18lm/W

I get ~35lm/W.

it consumed 3x0.25= 0.75Ah or around 79% of the two cell's rated value of 950mAh each..?

It looks about the right ball park, dunnit.

So; who gets the exploding box of dog turds in the post - battery seller or light manufacturer?

Well, I don't see where Moon are getting 43 hours from.

I'm not about to burn through a load to test a light if there are alternatives..

Looks like it won't take long though.

 

[wafter]

The average of the two limits you quoted.

Not necessarily, the voltage of alkalines varies much more that NiMH throughout the discharge cycle, and the source resistance is both higher to start with, and increases more during discharge. At 250mA load, the source resistance will be losing you something like 0.13V. I've known duff batteries have a voltage that looks good, but high resistance.
View attachment 719548

View attachment 719549


I get ~35lm/W.

It looks about the right ball park, dunnit.

Well, I don't see where Moon are getting 43 hours from.

Looks like it won't take long though.

Thanks for all that!

Seems you're correct about the the brightness per Watt; surprised that was the only calc I cocked up last night

So, it seems reasonable to assume that the batteries are fine (although it would be good to test them in an unregulated device to complete discharge to confirm) and that there is an issue with both of the lights I've tested. I do have a third I might try, and will mention it to Moon customer service to see if they have owt to say about it..

 

[Ajax Bay]

Not sure if any use. But I just weighted my Eneloop Pro 930mah AAA.
2 batteries comes to 25 grams on the kitchen scales.

Thanks - not sure how significant this is, but a pair of my "950mAh Eneloop Pros" come in at 21.4g; potentially suggesting they contain significantly less magic than yours; if mass can be taken as an indicator of capacity..

Assuming you (and the scales used) have measured the 2 batteries accurately, this pretty well determines that the poorly performing batteries described in the OP are fake: the light weight is a red flag.
Visibly, the fake ones have TM after pro and the genuine ones don't.
OP bay link image (950mAh):

[This is a fake AA version, for illustration.]
Get some assured rechargeables and do the test again: and ride on (flashing for twice the run time and the win).
https://www.batterystation.co.uk/pa...aa-hr03-930mah-rechargeable-batteries-4-pack/

 

[albion]

I was certainly puzzled about that assumption the batteries are fine, and that the light manufacturer is telling fibs.

 

[presta]

I was certainly puzzled about that assumption the batteries are fine, and that the light manufacturer is telling fibs.

If the current's 250mA the capacity of those cells would have to be over 10Ah to last 43h. Either the lamp's faulty, or the current measurement's incorrect, or it can't last 43h on the setting it was measured. Nevertheless, I'm sure my lights lasted longer than 4 hours, but the manufacturers don't say how bright they are. I'll give them a measure tomorrow.

 

[wafter]

Assuming you (and the scales used) have measured the 2 batteries accurately, this pretty well determines that the poorly performing batteries described in the OP are fake: the light weight is a red flag.
Visibly, the fake ones have TM after pro and the genuine ones don't.
OP bay link image (950mAh):

View attachment 719558

View attachment 719560
[This is a fake AA version, for illustration.]
Get some assured rechargeables and do the test again: and ride on (flashing for twice the run time and the win).
https://www.batterystation.co.uk/pa...aa-hr03-930mah-rechargeable-batteries-4-pack/


View attachment 719559

Thanks - that's very helpful. The packaging's long-discarded but was the same blister-pack format as that illustrated. My cells also have the "TM" on the jacket.

Do you have a link to the source that breaks this down please? I bought the batteries a fair while ago but the seller is still active and I'd like to drop them a message with some supporting evidence..

Of course the current draw measuredstill points the finger at the light, but there are certainly red flags associated with the batteries and it can't hurt to shake the tree a little.

The scale used to weigh them typically gets used for much lighter / more precise readings, so I'd be confident in its output to +/- 0.1g ot better..

I was certainly puzzled about that assumption the batteries are fine, and that the light manufacturer is telling fibs.

Makes sense when you look at the numbers, as Presta suggests below... looks like I might be having the p*ss taken out of me from all angles

If the current's 250mA the capacity of those cells would have to be over 10Ah to last 43h. Either the lamp's faulty, or the current measurement's incorrect, or it can't last 43h on the setting it was measured. Nevertheless, I'm sure my lights lasted longer than 4 hours, but the manufacturers don't say how bright they are. I'll give them a measure tomorrow.

 

[Ajax Bay]

Do you have a link to the source that breaks this down please? I bought the batteries a fair while ago but the seller is still active and I'd like to drop them a message with some supporting evidence.

Source??
First image is from your bay seller. The single cell image likewise, but from their AA offering.
The second image is from the best genuine price for a 4-pack (and images are same for several reputable sellers).
Not obvious (to me) what else you need (could also mention the weight discrepancy).
Shake the tree? Poke the bay.

 

[wafter]

Source??
First image is from your bay seller. The single cell image likewise, but from their AA offering.
The second image is from the best genuine price for a 4-pack (and images are same for several reputable sellers).
Not obvious (to me) what else you need (could also mention the weight discrepancy).
Shake the tree? Poke the bay.

Thanks - no links to a deconstruction of a fake cell versus the real deal...?

 

[Ajax Bay]

Thanks - no links to a deconstruction of a fake cell versus the real deal...?

You'll be able to do that once you cut the cells you decry in the OP longitudinally in half. Share the image when you do.

 

[albion]

If the current's 250mA the capacity of those cells would have to be over 10Ah to last 43h. Either the lamp's faulty, or the current measurement's incorrect, or it can't last 43h on the setting it was measured. Nevertheless, I'm sure my lights lasted longer than 4 hours, but the manufacturers don't say how bright they are. I'll give them a measure tomorrow.

But the 43 hours plus is only for flash mode. And flash can use one tenth or less of constant.

 

[wafter]

You'll be able to do that once you cut the cells you decry in the OP longitudinally in half. Share the image when you do.

Without a legit cell for comparison how would that achieve anything other than ruining a perfectly serviceable battery..?

But the 43 hours plus is only for flash mode. And flash can use one tenth or less of constant.

Moon state 43hrs for Mode 2 constant output at 25l, and 110hrs for the same light output when flashing..

 

[fossyant]

You'll be able to do that once you cut the cells you decry in the OP longitudinally in half. Share the image when you do.

And don't do that with a Lipo.

 

[albion]

Without a legit cell for comparison how would that achieve anything other than ruining a perfectly serviceable battery..?


Moon state 43hrs for Mode 2 constant output at 25l, and 110hrs for the same light output when flashing..

If the single red Led is about 350 lumen per watt then I guess that is about fine for Alkaline. 930mah Eneloops would thus run for 31 hours.

 

[presta]

If the single red Led is about 350 lumen per watt

In which case the supply current would be 25mA, not the 250mA that's been measured.

 

[albion]

In which case the lights would be fake.