Posts Tagged LP-E8

Arduino Battery Capacity Tester

Ar2uinoBatteryIllustrationS  NOTE! This Arduino Battery Capacity Tester has been updated!
See the new, improved and simplified version of the
New Battery Capacity Tester!

 

Arduino Battery Capacity Tester CircuitTo automate the testing of (camera)batteries and to make the tests repeatable I came up with a small circuit controlled by a Arduino microcontroller  – you can see the UPDATED battery capacity tester circuit on the left. (If anyone is interested I can put up the Arduino program that controls it.) I have used this on my tests of camera batteries – check them out!

Someone was! 🙂  (Interested in the Arduino program!) Link at the bottom of this post! The program outputs measurements to the serial monitor.  I just copy it from there to Excel and do the calculations and graphics in Excel.

After some consideration about the measurement process I decided to try to approximate the real world picture-taking – but I also wanted a repeatable and reasonable easy and quick way of comparing different batteries. The circuit I decided on can handle the three most common batteries: 1.2 V NiMh, 3.7  and 7.4 V Li-ion by changing the load resistor. I wanted the load to mimic the actual taking of pictures by applying the load for a number of shorter times – like taking pictures.

For the 3.7 V Li-ion batteries on test here I decided that, as the battery according to Canon should give about 300 pictures, I would apply the load in around 300 short intervals. That ideally translated to a 5.2 ohm resistor giving around 500 mA load for 16 seconds each. Settled for a more standard resistor of 5.6 ohm. The load in this case is around 2.5 watts so use an appropriate resistor – with higher rating unless you want it to get very hot! 🙂  I also decided to let the battery “catch its breath”  for 16 seconds between each “picture” – again mimicking (very oversimplified) the real world behaviour while keeping the time down. Initially I wanted to follow a “real” standard like the CIPA one – but it was much to complicated for me and would involve far too much manual work. More to read about battery measurement in the CIPA document – but be warned it is very technical!

PEPs This 16 second 5.6 ohm load followed by a 16 second rest period just had to have a name so I called it Photoman Equivalent Picture samples (PEPs) – cool eh? 😉 NOTE that this is not real pictures taken but gives a good enough approximation – especially for comparing batteries! . The circuit takes into account the resistance of the MOSFET transistor used – just below 0.4 ohm – but it lowers the load a little bit. Running through the whole test takes about 3 hours per battery. Cut off voltage is 3.0 V for Li-ion batteries so that is where I stopped the tests. (This goes well with my Canon S95 that signals empty battery at that voltage.)

mAh My testing method also gives the capacity in mAh under the above “simulated real world picture-taking” conditions. Note that under other (“laboratory”) conditions these batteries can give other mAh capacities – but as I do it the same way in all my tests you can compare the results between the batteries that I test.

Here is a link to the Arduino program: BatteryCapacityTester

NOTE: Right click on the link and select “Save target as…” Due to limitations with WordPress this Arduino source code file has been given the extension “.doc”. After saving this to your disk rename the extension to “.ino”.

As usual if anything goes wrong or gets broken by using this information I am sorry – but all the decisions are yours!

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Canon EOS 550D Compatible LP-E8 Battery

Here in Sweden the original batteries LP-E8 for the superb Canon EOS 550D/Canon Digital Rebel T2i are priced quite high at around 600 SEK/€ 60/$80 so I googled after some lower priced alternatives and I came upon Deal Extreme Compatible battery (SKU 35588) for only 10% of the original battery cost (free freight) … and after some consideration I ordered two. After waiting close to two weeks the batteries arrived! In the meantime I had read on several forums about “compatible” batteries and there seemed to be different opinions about whether the batteries were really compatible or not and whether they could actually damage the camera or not

NOTE! This test just shows the results from the two samples that I got and that I give NO GUARANTEE that any batteries bought by you will work as the ones I got! The fact that I got two different capacities might indicate that batches have different properties! Any tests that you make are your own responsibility!

This “make or break” was a worry on my mind and I did not dare to put the batteries in the camera when I got them!  I decided to try to compare them to the original battery. The two batteries I got were stamped with different capacities as you can see in the table below.

The batteries arrived boxed in small red&yellow boxes (above). They were also put in small plastic bags and had on their underside a snap-on cover. All in all they had a trustworthy feel to them. The plastic seemed as sturdy as the original. No text at all on the top. The grey colour were ever so slightly darker grey i colour than the original.

Turning them over they were printed with voltage, capacity and other info. The contacts were also visible and looked very much as the originals except that you could see the “gold-plated” contacts glimmer a little clearer than on the originals.

Now I set about checking weights and sizes. The compatibles weights were 18% and 4% lighter than the original. No visible difference in sizes. Having done this I thought it worth the risk of charging them. Charging them with the original charger posed no problems and after less than an hour they were both fully charged. (I guess they were partially charged from the beginning.) To get comparable results I charged the original battery also.

Not knowing that much about battery science I googled to try to find out what the different specification voltage meant 7.2/7.4 Volts. I found no easy to understand explanation – might depend on different materials for anode/cathode – but it is still a little of a mystery to me what the voltage actually stands for

These were the results I found when measuring the voltages under different loads.

As the no-load voltage of all three batteries were the same with 8.32 Volts I decided I would test them in the camera. Also helped was the fact that the the difference under load was just 1-2%!

I tried them and there was no problem with fitting, all three batteries felt similar in fitting them in the camera so I (with some excitement) turned the camera on – and it worked as usual! 🙂

I have now been using them for a few weeks and I have seen no real difference between the batteries – original or compatibles. I have not really measured or kept a proper eye on capacity – but my feeling is that the batteries last the same time. (If I get curious I might do a proper capacity measurement…) I have read comments by other buyers that the low charge warning does not work so well with the compatibles. I do not know if it is like that – I tend to not notice the battery charge indicator until I see the flashing red low battery indicator – and then I change battery! I will try to keep an eye on that in the future and report back here with an update! With three batteries I tend not to worry too much – when one goes flat I just change to a new one! 🙂

Canon original battery lasted an impressive 827 pictures total – spread out over a rather intense 4 hour photo shoot – checking most pictures on-screen. Of the total about 50 was flash pictures.

UPDATE!

After a few months of rather intense use I can now report the following average capacity figures for the above batteries – both compatible and original. Used by what I would describe as a “keen” photographer (me).

Normal usage, lots of focusing (without taking pictures),  checking the majority of the pictures on-screen for 1-2 secs (no automatic image review), info display switched off, a mixture of lenses used but mostly the 18-55 mm kit lens and just 1-5 flash pictures per charge, camera never switched off. I have taken 300-500 pictures each day so this was much less intense then the above mentioned photo shoot.

Original battery lasted 1000 pictures – with two battery level warnings at 2 bars with 200 and at 1 bar with 100 pictures before empty.
Compatible battery lasted 800 pictures – ONE battery warning at 1 bar with 10 pictures before empty.

It was no surprise that the original battery was the (slightly) better of the two – but at a 10 times higher price …  

The battery level indicator works well with the original battery and there is not really any warning with the compatible – it just goes flat! BUT as I usually – in practice – have the info screen switched off I am as surprised with both batteries when they run flat! Having the info screen on I would definitely have a better chance of picking my moment to change the battery – if I have the original. Either way I would really appreciate a more forceful way of warning for low battery – one that is seen even when the display is switched off!

Till next time…

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