Painfully boring technical question re. rear lights and rechargeable batteries

[ColinJ]

Thanks - appreciate your thoughts!

I guess I need to lash something up to test their capacity; any suggestions?

How about sticking them in a rear light for a bike and seeing how long they last from fully charged...?

 

[albion]

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

 

[Mike Ayling]

Does the current spell of icy weather have any influence on your run time?
I don't what the save the planet effect is compared to rechargeables but I have a CherryBomd which I run in dayt time on disposables from Aldi. I get at least 100 hours in flashing mode.

 

[albion]

I assume you are using Flashing mode. None flashing would be a massive power drain. Also, reviews have mixed quality control and thus might hint of a power leak.

 

[wafter]

How about sticking them in a rear light for a bike and seeing how long they last from fully charged...?

Have you read the OP?

Simply knowing that they won't power my lights for very long has limited value.. hooking them up to a load of known value to ascertain total capacity for comparison to the quoted value is much more telling. If I had the ability to lash up such a setup..

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..

Does the current spell of icy weather have any influence on your run time?
I don't what the save the planet effect is compared to rechargeables but I have a CherryBomd which I run in dayt time on disposables from Aldi. I get at least 100 hours in flashing mode.

I'd imagine it does from my minimal knowledge of battery chemistry, however it certainly shouldn't cause the difference between what I'm seeing (3hrs) and the quoted runtime (46hrs).

I assume you are using Flashing mode. None flashing would be a massive power drain. Also, reviews have mixed quality control and thus might hint of a power leak.

Nope, always on.. the quoted runtime for this being 60-odd hours, but I'm lucky if I see four.

Tempted to go to flashing as this will extend battery life, and while this mode arguably has additional benefits, I don't much like being exposed to it myself..


So.... I have a multimeter, some batteries and assorted wires with crocodile clips courtesy of my late father, however am yet to find a way of reliably connecting it to a load of some description to do a capacity test.

In any case I bought the batteries over a year ago (although they've not seen a lot of use), so I potentially have very little sway with the seller.. although if I do end up testing them and getting suspect numbers I can threaten to report them to ebay I guess; for what that's worth...

 

[Kingfisher101]

I think I'd just get some more rechargeable batteries from somewhere like Argos or Screwfix or get some lights that you can recharge via the USB from Halfords etc.

 

[sleuthey]

presumably this would be by banging a volt meter across the batteries while the unit's in use..?

Yes. Just before when it would normally cut out.

 

[presta]

I'm running the light with 950mAh rechargeables; which when fitted are around 1.44v each for a total across both cells in series or around 2.88v. When the lights die the cells are at 2.3-2.4v.

So you have 0.95x2.62 = 2.5Wh available from the battery, and Moon claim 43hr battery life at 25 lumen for your lamp, so that suggests it's drawing 2.5/43 = 58mW, giving 25/0.058 = 430 lm/W.

Being as "The current state of the art is 150 lm/W" and "the LED industry is aiming for 250 lm/W, with 300 or so the likely theoretical limit" something doesn't sound quit right. Nevertheless, it's not as big discrepancy as you seem to be getting.

I think you need to define what your end point is (subjectively too dim or does it just cut out?), and measure the supply current, then these might be of some help:

Nickel Metal Hydride (NiMH) Handbook and Application Manual
Alkaline Manganese Dioxide Handbook and Application Manual

Early in the charging process the new charger rejected some of my old batteries as being faulty so I recycled them and bought replacements.

My charger complained that one of the cells out of my desk phone was faulty because I forgot them and let them discharge until one went into reverse, but I managed to recover it by putting it on a power supply and nuking it with an amp or so for a few seconds.

I've not tested as you suggest - presumably this would be by banging a volt meter across the batteries while the unit's in use..?

Measuring the battery on and off load, along with the current is useful, then you can calculate the source resistance.

I guess I need to lash something up to test their capacity; any suggestions?

If you know what the lamp draws that will do as your test load, especially as you already know it's lasting 3-4 hours.

 

[Bristolian]

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

Were they fully charged?

 

[Bazzer]

You can get on eBay devices which show battery capacity and you can get load testers. But in terms of cost, I am not sure what this would achieve for you, with the total cost of the devices likely being more than a replacement light.
If the batteries are from a reputable source, so the stated power should be there or thereabouts, it sounds like the internal circuits of the lights are screwing the battery life. So you either need new lights, or limit your rides in the dark.

 

[albion]

Here is the Hansa?
'

Awful seller, don’t waste your time. EBay had to step in to refund Panasonic Eneloop PRO AA batteries 2550mAh Rechargeable HR6 Ni-MH (#134467008079)	Buyer: s***o (307) £11.99	Past 6 months
Detailed item information is not available for the following items because the Feedback is over 90 days old.
Fake Eneloops. Seller refunded without question. Panasonic Eneloop PRO AA batteries 2550mAh Rechargeable HR6 Ni-MH (#134467008079)	Buyer: n***b (1966) £47.96	Past 6 months
Poor communication and arrived late! sony vtc5 2600mAh High Drain Li-ion 3.7V Rechargeable Battery x1 (#134548299985)	Buyer: 2***e (55) £5.99	Past 6 months
2 x Efest 3000mah 35A 18650 cells. NEW STYLE 20 Digit security verification codes. Go to manufacturer site to confirm. Originality. Neither of the codes are genuine issue. Explains why they're low powered after a full external charge on delivery after only an hour. I have genuine 18 month old battery's the same that have more kick to them. EFEST Battery 3000mah 35A Rechargeable x2 (#134563029667)	Buyer: i***m (1747) £12.99	Past year
Not a genuine item - many red flags with item. Eneloops often copied, poorly. Refund requested and granted. Panasonic Eneloop Pro AAA Rechargeable Battery 4 PCS (950 mAh) – BK-4HCCE/4BT (#134039851244)	Buyer: k***k (1473) £10.75	Past year
6 weeks after buying batteries will no longer hold a charge, too late to return! Poor quality, should have paid a bit more for better ones.... Ultra fire BRC 4000mAh 3.7V Rechargeable Battery for Video Doorbell Torch LEdlig (#134098251245) '

Time for a beer. You wos robbed. Even with refunds, guy is probably making a fortune. (Might not be totally the sellers fault. Grey markets are always risky.)

 

[Sharky]

I bought some of Amazon's rechargeable AA batteries.
They hold their charge fine, but the diameter of them is minutely bigger than duracell ones and they can be a tight squeeze trying to fit them into some devices.

 

[albion]

Try these.

https://www.ikea.com/gb/en/p/ladda-rechargeable-battery-hr03-aaa-1-2v-90509819/
Hopefully still made in Japan where there is said to be one single factory! Weight is fine !

 

[StuAff]

Try these.

https://www.ikea.com/gb/en/p/ladda-rechargeable-battery-hr03-aaa-1-2v-90509819/
Hopefully still made in Japan where there is said to be one single factory! Weight is fine !

The ones I've got have been excellent.

 

[Mike_P]

I bought some of Amazon's rechargeable AA batteries.
They hold their charge fine, but the diameter of them is minutely bigger than duracell ones and they can be a tight squeeze trying to fit them into some devices.

That size problem occurs with a lot of rechargeables. I've put them in a device and had a real fight to get them out so much so I tend now to use Aldi or Lidl alkalines and recycle them when dead. Having a good battery tester is useful. Often it's only one battery that has gone dead. Given how long the alkalines last in comparison I'm not convinced rechargeables are that green given the amount of charging needed.