Painfully boring technical question re. rear lights and rechargeable batteries

[wafter]

I've been experiencing issues with my Moon Pulsar rear light (COB LED, 2xAAA batteries) dying after around 3-4hrs of use.

I thought this was a fault with the unit but have since tested another, NOS item with similar results. 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.

I appreciate that Alkaline batteries are typically higher voltage than NiMH (the former listed at 1.5v nominal, the latter 1.2v), however am still a bit surprised by these results since it seems that Alkalines typically run down to circa 1.2v before they really drop off, while at 950mAh the lower capacity of the rechargeables (versus 1.5Ah typically for Alkalines..?) don't scale with the 3-4hrs runtime I'm getting versus the 46hrs published with Alkalines..

Can anyone with the capacity to understand this stuff offer any thoughts please?

I love these lights as they don't have integral batteries, so really want to make them more viable if possible..

 

[Sharky]

Don't understand the numbers myself, but 3 to 4 hours for a rear light seems very short. When I was commuting, my flashing rear lights with rechargeable batteries would last almost all winter. Always had two rear lights, so that if one went and I didn't notice until I got home or office, would have a back up.

And I always used reflective slap bands on the ankles as my ultimate back up.

 

[wafter]

Don't understand the numbers myself, but 3 to 4 hours for a rear light seems very short. When I was commuting, my flashing rear lights with rechargeable batteries would last almost all winter. Always had two rear lights, so that if one went and I didn't notice until I got home or office, would have a back up.

And I always used reflective slap bands on the ankles as my ultimate back up.

Indeed.. I don't understand the numbers either! It would last longer were it flashing, but again nowhere near the quoted figures. I guess it could be a fault on both units, but seems unlikely..

 

[ColinJ]

Are you sure that the batteries are not knackered, and are being fully charged?

I had some which had seen better days and only had a fraction of their design capacity.

I now have a fancier charger than my previous simple one. Early in the charging process the new charger rejected some of my old batteries as being faulty so I recycled them and bought replacements.

 

[albion]

Likely you are not using Eneloops. And it is the load voltage that matters. No load voltages are deceptive.

 

[wafter]

Are you sure that the batteries are not knackered, and are being fully charged?

I had some which had seen better days and only had a fraction of their design capacity.

I now have a fancier charger than my previous simple one. Early in the charging process the new charger rejected some of my old batteries as being faulty so I recycled them and bought replacements.

The batteries shouldn't be knackered as they're nearly new and being charged on an overtly decent Ansmann charger that apparently "conditions" them and rejects any it sees as knackered.

Not sure what max charge voltage should be but it seems that with Li Ion rechargeables at least their rated voltage is a mean between max and min working; for example 3.7v typically charge to 4.2v.. as such I assume 1.45v for a 1.2v-rated cel is reasonable indication that it's fully charged as this too is about 20% above rated output..?

Likely you are not using Eneloops. And it is the load voltage that matters. No load voltages are deceptive.

lol - as it happens I am using nearly-new Eneloop Pros.. I assume what you're getting at is the ability for a cell to sustain voltage under load.. which I guess could be described as "high drain" or "low drain" suitability...

These batteries are pushed for "high drain" applications but since the lights are lowish-output LEDs I don't think the discharge rate should be particularly high.. think I worked out the current draw at about 60mA (0.5v drop on 0.95mAh is 0.45Wh; over three hours to discharge this is about 0.15W at a mean voltage of 2.6v so 0.06A).

While the low-drain batteries seem to have higher capacities, I assume there's no other drawback (other, perhaps than increased self-discharge) to using high-drain batteries in low-drain applications..?

 

[Bazzer]

That battery use sounds excessive.
I have a cateye permanently at the rear, which is plenty bright enough with x2 AAA Asda rechargeables, which claim to be 1,000mAh.
I always run mine in flashing mode, but when I was commuting, (75 - 90mins each way), the only time I recharged them was when I remembered.-Probably at best once a month. And given I left home at 5:30am, they were on in the morning from around the end of September to April, and for the return journey for the depths of winter.

 

[wafter]

That battery use sounds excessive.
I have a cateye permanently at the rear, which is plenty bright enough with x2 AAA Asda rechargeables, which claim to be 1,000mAh.
I always run mine in flashing mode, but when I was commuting, (75 - 90mins each way), the only time I recharged them was when I remembered.-Probably at best once a month. And given I left home at 5:30am, they were on in the morning from around the end of September to April, and for the return journey for the depths of winter.

Thanks... that's interesting. I'd have expected them to last ages too and thought that my weekly swap / charge routine would see me never running out.

It all came from ebay so I guess the provenence of all involved could be in doubt; although I don't see why anyone would bother counterfeiting a cheap bike light, while it's also done it with other rechargeable AAAs too. I guess I could do a discharge capacity test on the batteries if I could find a known-load, although I can't think of anything suitable offhand.

One positive thing to come out of it all is a great experience with Moon's customer service - while they couldn't help in any practical terms, they did offer to repair any issues FOC even though it's out of warranty if I returned it to them in HK (which of course is cost-prohibitive) and when I declined to do so they offered me a 10% off voucher for another

I've mentioned the rechargeable thing to them; will be interesting to see what they say (if anything).

 

[sleuthey]

Would recommend testing the lights with a pair of alkalines and comparing the run time to the 46h claim. Have you tested the PD whilst under load at around the 3h mark?

 

[Kingfisher101]

Thanks... that's interesting. I'd have expected them to last ages too and thought that my weekly swap / charge routine would see me never running out.

It all came from ebay so I guess the provenence of all involved could be in doubt; although I don't see why anyone would bother counterfeiting a cheap bike light, while it's also done it with other rechargeable AAAs too. I guess I could do a discharge capacity test on the batteries if I could find a known-load, although I can't think of anything suitable offhand.

One positive thing to come out of it all is a great experience with Moon's customer service - while they couldn't help in any practical terms, they did offer to repair any issues FOC even though it's out of warranty if I returned it to them in HK (which of course is cost-prohibitive) and when I declined to do so they offered me a 10% off voucher for another

I've mentioned the rechargeable thing to them; will be interesting to see what they say (if anything).

LOL, They would counterfeit a pair of socks on Ebay. Chances are its a Chinese knock off/knock offs.
The site is full of fakes, I've had Nike Trainers that were like walking on concrete they were that hard and even fake bike grips.

 

[wafter]

Would recommend testing the lights with a pair of alkalines and comparing the run time to the 46h claim. Have you tested the PD whilst under load at around the 3h mark?

Cheers - thought of testing with alkalines, but it pains me too much to create that much waste in the name of science

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..?

LOL, They would counterfeit a pair of socks on Ebay. Chances are its a Chinese knock off/knock offs.
The site is full of fakes, I've had Nike Trainers that were like walking on concrete they were that hard and even fake bike grips.

Perhaps... although that would be really left-of-the-field were it the case..

 

[Jenkins]

LOL, They would counterfeit a pair of socks on Ebay. Chances are its a Chinese knock off/knock offs.
The site is full of fakes, I've had Nike Trainers that were like walking on concrete they were that hard and even fake bike grips.

Very much this for the batteries. @wafter do you have a link to the seller or the sale itself?

 

[wafter]

Very much this for the batteries. @wafter do you have a link to the seller or the sale itself?

Thanks - ebay has lost the listing, but here's the seller:

https://www.ebay.co.uk/usr/alanb-8043

 

[Jenkins]

Doesn't appear to be the normal Chinese based drop shipper you'd find selling knock-offs on Ebay/Amazon, but the first page of feedback shows this...

At first I thought these were genuine Panasonic batterries but on closer inspection and charging them it was obvious to me these are counterfeit. Please do not buy as you can buy originals for four pounds more from other respected online sellers. DON'T WASTE YOU MONEY on these. Seller refunded immediately upon return.

and there's a few other similar comments later on. Registered as a private seller, but does seem to have them in a commercial quantity. I'd stick with the diagnosis of them being fakes and of much inferior quality. If you're near an Ikea they do their own brand AAA (£8 for 4 )or AA batteries (LADDA)

This is why for certain items (especially brand name goods) I stick to known shops or trusted traders having soon so much fake cr*p in my line of work.

 

[wafter]

Doesn't appear to be the normal Chinese based drop shipper you'd find selling knock-offs on Ebay/Amazon, but the first page of feedback shows this...

and there's a few other similar comments later on. Registered as a private seller, but does seem to have them in a commercial quantity. I'd stick with the diagnosis of them being fakes and of much inferior quality. If you're near an Ikea they do their own brand AAA (£8 for 4 )or AA batteries (LADDA)

This is why for certain items (especially brand name goods) I stick to known shops or trusted traders having soon so much fake cr*p in my line of work.

Thanks - appreciate your thoughts!

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