[AstroDave]

Prompted by various threads on the Forum wondering about the quality of non-OEM camera batteries, along with conversations with forum member jon.partsch (and his great account of adventures rebuilding and measuring batteries: Wasabi battery pack rebuild - PentaxForums.com ) I have run discharge curves for all the batteries I have at hand. This includes the batteries for my K-1/K-3, Q7, and Canon G15.

The short version is that the OEM batteries I have, all of which have been used for several years or more, perform close to original specifications, whereas the one non-OEM battery tested falls well below its OEM counterpart, and much below its claimed capacity.

Since my first round of such measurements (Some Pentax D-LI90 Battery Charge/Discharge Measurements - PentaxForums.com), I have acquired a very nice voltage logger (HOBO UX120 4-Channel Analog Data Logger - UX120-006M) so I no longer have to write down voltages and times. The logger reads and stores voltages from 0 to 2.5 V, with a precision of 40 microvolts. Since all the camera batteries have higher output voltages, I used simple resistive voltage dividers to put the voltage in the correct range for the logger. The dividers have typical resistances of 20K to 100K ohms, so they have essentially no effect on the battery discharge current. I set the logger to take a data point every 30 or 60 seconds.

I made several battery holders with spring-loaded contacts so I could connect the batteries to the logger. Since I know the load resistance to which the batteries are connected for the drain measurement, I can calculate the current being drawn from the battery by Ohms law (current = volts/resistance), and by summing up all the measurements for the relevant time intervals, determine the milliamp hours (mAh) that the battery can provide.

Here are a pictures of some of the test jigs (some with batteries):

Pentax D-LI90


Pentax D-LI68


Canon NB-10L



Generally, batteries were charged in the relevant OEM charger to full charge. In most cases, the battery was removed from the charger for a few minutes and inserted once again, until the charger deemed that the battery was again fully charged. The discharge measurements started within minutes of that final charge.


Pentax D-LI90 Batteries

I have three of these (genuine Pentax) batteries. They are dated 201102, 201306, and 201601, and probably arrived with my K-5 (March 2011), K-3 (March 2014), and K-1 (July 2016) respectively. Somewhere back in the K-5 era, I bought an extra, which went with the K-5 when it was sold.

Originally, I was drawing current from these batteries at a ~150-250 milliamps (mA) with load resistors of 30 to 50 ohms. However, after discussions with Jon.Partsch and seeing his table of current drain values in his and my references above, I lowered my load resistors to 12.7 ohms, so that typical current draws were more like 500-600 mA. Actually, the batteries performed similarly (i.e. same number of mAh) independently of load. This behavior is better than that observed for the non-OEM Vivitar battery discussed below.

All three of these batteries, despite their ages, perform very closely to specification. The batteries are rated at 1860 mAh (or 14 Wh). In my last data runs, with the 12.7 ohm resistors, when drawn down to 6.0 volts, the batteries performed as:

Battery			Measured	Measured
Date Code			(mAh)	(Wh)
201102			1872	13.6
201306			1844	13.3
201601			1826	13.2

The oldest battery actually marginally exceeded its mAh specification! The others are just a bit below spec.

Based on the number of exposures which have been taken by my K-3 and K-1 cameras, I estimate that each of these batteries has probably undergone somewhere between 100 and 200 charge cycles. All the batteries get rotated at random between the cameras, and have usually been used until the camera battery indicator shows less than full charge.

Bottom line: Pentax OEM D-LI90 batteries, even as much as 10 years old and after a couple of hundred charge cycles, perform very close to original specifications.

Here are two plots showing voltage versus time for all three batteries for 12.7 ohm and 30 ohm loading (sorry about the color change between plots!):







Pentax D-LI68 Batteries

These are used in my Pentax Q7. I have two OEM (Pentax) batteries, which are approaching 6 years old (my Q7 was acquired in July 2015). There is no date indication on the batteries, and I do not remember which is the original with the camera and which one I bought shortly thereafter. The Q7 has taken not quite 1100 exposures, so these batteries have probably fewer than 10-20 charge/discharge cycles on them. These batteries and those for the Canon G15 have generally not been discharged in use as deeply as the D-LI90s, which means not much at all

These were discharged through a 30 ohm resistor, so the current draw was around 120 mA (perhaps a bit light compared to actual draw in the camera?). Each battery was run twice. The results, for a discharge to around 2.90 volts, are

Battery	Run		mAh		Wh
1	1		988		3.6
	2		940		3.4
2	1		925		3.3
	2		888		3.2

The specification for the D-LI68 are 1000 mAh (typical), 940 mAh (minimum) and 3.4 Wh. Battery 1 meets these specifications, while battery 2 seems to be a bit low.

I think this is not bad for a couple of 6-year old batteries.


Canon NB-10L and Vivitar VIV CB-10L batteries

These are used by my Canon G15 camera, which was acquired in April of 2013, so the Canon battery is about 8 years old. The Vivitar may be a year or so younger. The Canon has taken more than 4600 pictures. The batteries have probably been through 30-50 charge/discharge cycles.

These batteries were discharged through various loads, most typically 50 ohms, but the Vivitar was also tested with 12.7 ohms and 30 ohms. I have no idea how the relevant discharge currents relate to actual loading in the camera.

For the Canon NB-10L battery, the results are

Run		discharge level		mAh		Wh
1		6.04 volts		874		6.5
2		6.06 volts		847		6.4

The battery is rated by Canon at 920 mAh / 6.8 Wh . So, my data show the battery to be somewhat below rated, but not too far, for an 8-year old battery. Not too bad, I think.

For the Vivitar VIV CB-10L battery, with the 50 ohm load, my results are

Run	discharge level		mAh		Wh
1	5.80 volts		337		2.4
2	5.95 volts		596		4.3

I don’t know why these are so different, but both are much below the Canon (and Vivitar's rating - see below).

And, for some heavier loads:

Run	discharge level		load resistance		mAh		Wh
3	6.02 volts		12.7 ohms		199		1.3
4	6.01 volts		30 ohms		358		2.6

The Vivitar does not seem to do well under heavier loads.

Vivitar rates this battery at 1300 mAh, which seems very optimistic when compared to the same-size Canon battery, and wildly optimistic compared to my measurements!


So, for my rather small sample, it seems that Pentax and Canon OEM batteries supply very nearly their rated mAh, even when they are as much as 10 years old. On the other hand, the Vivitar battery appears to be both over-rated and have not nearly the mAh rating claimed by its vendor.


I would be glad to measure and report on any batteries sent to me, as well as consult on how you might make similar measurements.

[shyrsio]

Very interesting study and finds. Thank you for the amazing work!

[aaacb]

Thanks for posting. I've had mixed success with third party batteries, from just lower battery life but otherwise fine for the money (ricoh gr 3 and pentax k10d) to not being able to power the camera during long bursts (panasonic g95), and I think they were all the same brand. So currently I'm using only oem batteries.

[DWS1]

Thank you for your extensive work here. It's very interesting.

[ramseybuckeye]

Nice work Dave. Without any scientific study I know the aftermarket batteries wear out quicker. Most of my Pentax batteries have worn well over the years, I do have a D-LI109 dated 201707 that does not perform well. But your study shows me that I should buy another OEM before buying a generic battery. It's just really hard when you look at the prices, but looking at the data makes more sense.

[c.a.m]

So, for my rather small sample, it seems that Pentax and Canon OEM batteries supply very nearly their rated mAh, even when they are as much as 10 years old. On the other hand, the Vivitar battery appears to be both over-rated and have not nearly the mAh rating claimed by its vendor.

Thanks @AstroDave for this interesting piece of work and your report. Your data shows that the time-proven OEM D-Li90 is a robust battery, probably based on high-quality cells. Glad that Pentax kept it in the new K-3 Mark III.

I think the discharge curves are quite 'clean' and characteristic of what would be expected of healthy Li-ion cells.

Love your battery jigs!

- Craig

[AstroDave]

Love your battery jigs!

Thanks. It took me a while to figure out how to make something suitable. Then, the idea of spring loading popped into my head. The springs are from my "stuff" collection, in this case rescued from ball point pens!!

[grog85361]

You do awesome work. Thank you!

[kypfer]

Excellent - good old-fashioned hands-on facts
Those battery jigs are my kind of engineering
One of my OEM D-Li90 batteries doesn't have a date-code. Maybe it's so old they hadn't invented the calendar yet I suspect it came with my K-5, so 2014 vintage or earlier, but it seems to perform as well as the new battery that arrived with my K-3iii.
The "Jupio" branded D-Li109 that was a "bundle" with my new KP never was never much better than half as good as the OEM battery and only lasted a year before it died completely!
The only other comparisons I've got are a couple of (different type) Hahnel batteries. They seem almost as good as the respective OEM originals.
It'd be nice to have a proper logging meter to check these things … really quite envious
Thanks for an interesting post!

[jslifoaw]

Most of my OEM D-Li90 batteries are from used bodies since the only compatible body I bought new was the K-1. I also bought one used from a reputable local store.

The oldest ones appear to not last quite as long but seem to perform well for being 10 years old. Best part is that they behave predictably and don’t self discharge materially.

I think ultimately, third party batteries can be nearly as good but often aren’t and there may be no easy way to tell (the brand doesn’t reliably guarantee performance). The last thing most people want is to discover their camera won’t turn on a month later because the battery has discharged, or inserting what they thought was a fully charged spare only to find that it too has discharged while sitting idle.

It’s especially stressful when travelling. Predictability and reliability can pay for themselves in not having to closely manage how and when you charge batteries.

[barondla]

Prompted by various threads on the Forum wondering about the quality of non-OEM camera batteries, along with conversations with forum member jon.partsch (and his great account of adventures rebuilding and measuring batteries: Wasabi battery pack rebuild - PentaxForums.com ) I have run discharge curves for all the batteries I have at hand. This includes the batteries for my K-1/K-3, Q7, and Canon G15.

The short version is that the OEM batteries I have, all of which have been used for several years or more, perform close to original specifications, whereas the one non-OEM battery tested falls well below its OEM counterpart, and much below its claimed capacity.

Since my first round of such measurements (Some Pentax D-LI90 Battery Charge/Discharge Measurements - PentaxForums.com), I have acquired a very nice voltage logger (HOBO UX120 4-Channel Analog Data Logger - UX120-006M) so I no longer have to write down voltages and times. The logger reads and stores voltages from 0 to 2.5 V, with a precision of 40 microvolts. Since all the camera batteries have higher output voltages, I used simple resistive voltage dividers to put the voltage in the correct range for the logger. The dividers have typical resistances of 20K to 100K ohms, so they have essentially no effect on the battery discharge current. I set the logger to take a data point every 30 or 60 seconds.

I made several battery holders with spring-loaded contacts so I could connect the batteries to the logger. Since I know the load resistance to which the batteries are connected for the drain measurement, I can calculate the current being drawn from the battery by Ohms law (current = volts/resistance), and by summing up all the measurements for the relevant time intervals, determine the milliamp hours (mAh) that the battery can provide.

Here are a pictures of some of the test jigs (some with batteries):

Pentax D-LI90


Pentax D-LI68


Canon NB-10L



Generally, batteries were charged in the relevant OEM charger to full charge. In most cases, the battery was removed from the charger for a few minutes and inserted once again, until the charger deemed that the battery was again fully charged. The discharge measurements started within minutes of that final charge.


Pentax D-LI90 Batteries

I have three of these (genuine Pentax) batteries. They are dated 201102, 201306, and 201601, and probably arrived with my K-5 (March 2011), K-3 (March 2014), and K-1 (July 2016) respectively. Somewhere back in the K-5 era, I bought an extra, which went with the K-5 when it was sold.

Originally, I was drawing current from these batteries at a ~150-250 milliamps (mA) with load resistors of 30 to 50 ohms. However, after discussions with Jon.Partsch and seeing his table of current drain values in his and my references above, I lowered my load resistors to 12.7 ohms, so that typical current draws were more like 500-600 mA. Actually, the batteries performed similarly (i.e. same number of mAh) independently of load. This behavior is better than that observed for the non-OEM Vivitar battery discussed below.

All three of these batteries, despite their ages, perform very closely to specification. The batteries are rated at 1860 mAh (or 14 Wh). In my last data runs, with the 12.7 ohm resistors, when drawn down to 6.0 volts, the batteries performed as:

Battery			Measured	Measured
Date Code			(mAh)	(Wh)
201102			1872	13.6
201306			1844	13.3
201601			1826	13.2

The oldest battery actually marginally exceeded its mAh specification! The others are just a bit below spec.

Based on the number of exposures which have been taken by my K-3 and K-1 cameras, I estimate that each of these batteries has probably undergone somewhere between 100 and 200 charge cycles. All the batteries get rotated at random between the cameras, and have usually been used until the camera battery indicator shows less than full charge.

Bottom line: Pentax OEM D-LI90 batteries, even as much as 10 years old and after a couple of hundred charge cycles, perform very close to original specifications.

Here are two plots showing voltage versus time for all three batteries for 12.7 ohm and 30 ohm loading (sorry about the color change between plots!):







Pentax D-LI68 Batteries

These are used in my Pentax Q7. I have two OEM (Pentax) batteries, which are approaching 6 years old (my Q7 was acquired in July 2015). There is no date indication on the batteries, and I do not remember which is the original with the camera and which one I bought shortly thereafter. The Q7 has taken not quite 1100 exposures, so these batteries have probably fewer than 10-20 charge/discharge cycles on them. These batteries and those for the Canon G15 have generally not been discharged in use as deeply as the D-LI90s, which means not much at all

These were discharged through a 30 ohm resistor, so the current draw was around 120 mA (perhaps a bit light compared to actual draw in the camera?). Each battery was run twice. The results, for a discharge to around 2.90 volts, are

Battery	Run		mAh		Wh
1	1		988		3.6
	2		940		3.4
2	1		925		3.3
	2		888		3.2

The specification for the D-LI68 are 1000 mAh (typical), 940 mAh (minimum) and 3.4 Wh. Battery 1 meets these specifications, while battery 2 seems to be a bit low.

I think this is not bad for a couple of 6-year old batteries.


Canon NB-10L and Vivitar VIV CB-10L batteries

These are used by my Canon G15 camera, which was acquired in April of 2013, so the Canon battery is about 8 years old. The Vivitar may be a year or so younger. The Canon has taken more than 4600 pictures. The batteries have probably been through 30-50 charge/discharge cycles.

These batteries were discharged through various loads, most typically 50 ohms, but the Vivitar was also tested with 12.7 ohms and 30 ohms. I have no idea how the relevant discharge currents relate to actual loading in the camera.

For the Canon NB-10L battery, the results are

Run		discharge level		mAh		Wh
1		6.04 volts		874		6.5
2		6.06 volts		847		6.4

The battery is rated by Canon at 920 mAh / 6.8 Wh . So, my data show the battery to be somewhat below rated, but not too far, for an 8-year old battery. Not too bad, I think.

For the Vivitar VIV CB-10L battery, with the 50 ohm load, my results are

Run	discharge level		mAh		Wh
1	5.80 volts		337		2.4
2	5.95 volts		596		4.3

I don’t know why these are so different, but both are much below the Canon (and Vivitar's rating - see below).

And, for some heavier loads:

Run	discharge level		load resistance		mAh		Wh
3	6.02 volts		12.7 ohms		199		1.3
4	6.01 volts		30 ohms		358		2.6

The Vivitar does not seem to do well under heavier loads.

Vivitar rates this battery at 1300 mAh, which seems very optimistic when compared to the same-size Canon battery, and wildly optimistic compared to my measurements!


So, for my rather small sample, it seems that Pentax and Canon OEM batteries supply very nearly their rated mAh, even when they are as much as 10 years old. On the other hand, the Vivitar battery appears to be both over-rated and have not nearly the mAh rating claimed by its vendor.


I would be glad to measure and report on any batteries sent to me, as well as consult on how you might make similar measurements.

Great measuring and reporting. I use both Q and the big battery. So this study is very useful to me. As another data point I've had numerous 3rd party Q batteries swell. None of my Pentax batteries have this problem. The original battery (2011) still works fine, though at a little lower capacity.

Thanks,
barondla

[Mooncatt]

When you think about it, this makes logical sense. Aftermarket batteries have to fit in the same physical space as OEM batteries. To have a higher capacity, it necessarily means the "guts" that actually hold the charge are built thinner to accommodate more surface area. Even if we assume the higher advertised capacity battery started off with its rated capacity, it is going to wear out quicker than the OEM due to the less robust thinner layer design. Throw in the sometimes questionable build quality, and it isn't likely the best overall value.

[bdery]

I made several battery holders with spring-loaded contacts so I could connect the batteries to the logger. Since I know the load resistance to which the batteries are connected for the drain measurement, I can calculate the current being drawn from the battery by Ohms law (current = volts/resistance), and by summing up all the measurements for the relevant time intervals, determine the milliamp hours (mAh) that the battery can provide.

I would be glad to measure and report on any batteries sent to me, as well as consult on how you might make similar measurements.

As a scientist (actually, probably what would be called an engineer in the US), I gotta say: This. Is. So. Cool.

Great work!

My personal observation somewhat correspond to your findings. My old Pentax-branded batteries perform admirably even after many years. However, my Watson third-party do not show a different behaviour, so not all third-party are equal.

Also, for my Sony A7C I use the OEM battery as well as some Neweer cells, and again impossible to tell the difference, and the Sony camera reports a percentage. Seems accurate in all cases.

[madbrain]

Nice. It would be nice to see how those capacities translate in terms of exposures.
I recently did a non-CIPA test with a set of 6 Ikea LADDA 2500 mAh / 1.2V AA batteries in my K-1 II. I turned off the display, as well as instant review. I disabled auto(re)focus on remote and set the intervalometer. I got 5330 exposures that way until the battery ran out. Had to restart the intervalometer a few times, since the max is normally 2000 exposures. I think Pentax should fix it and allow a higher frame limit.
After the camera reported "battery depleted", I put the batteries in a couple of analyzing chargers. They recharged about between 1900 and 2100 mAh each.
I have had other (odd!) situations where the camera reported "battery depleted" and the AA cells recharged much less, though, as low as 500 mAh for some cells.
For the AA analyzing chargers, I use MaHA C9000, PSPower DC5000, and Opus BT-C2400. They don't report resistance, but they do report voltage during charge, final voltage, current during charge, and total mAh charge. They do discharge recharge/cycle though. Didn't have to build my own setup.
I have been shooting almost exclusively with AA batteries all along with my K200D, K-R, K-30 and K-1 II. It's one of the best features of Pentax bodies. I have a few hundred AA NiMH, mostly Eneloops.

I do have a few D-Li90, including the original Pentax, and two aftermarket. Never used them much, so can't really tell how they perform. My battery grip is always on the camera, and I find it very annoying to unscrew the battery grip from the camera to replace the D-Li90. I wish the opening was on the side and not underneath. Then I might actually use the D-Li90 a little bit more, in combination with AA in battery grip. And yes, I know the grip can take a D-Li90 battery as well. I don't bother.

[stevebrot]

However, my Watson third-party do not show a different behaviour, so not all third-party are equal.

I am currently evaluating three Watson's with my K-3. They seem to be up to the task so-far.


Steve