GH2 external battery

Posted on 27 May 2012

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I would like to power my whole rig, including the camera, from my  14.8V 95Wh V-mount batteries. The great thing about this is, that if the gear on the rig would take 12 W in total, I could run it a full day with one battery. If I would use the GH2 only, in theory it would be able to shoot for 24 hours on one battery (95Wh/3,4W).

V-mount specs

The total current of one battery is: 95Wh/14,8V = 6,4Ah= 6400 mAh. But one thing I don’t know is how much the maximum current draw is from these batteries. It might be higher then 95W, so the battery will run out in less then one hour, but it might also be lower. Looking at the specs of other batteries, I would say it’s not smart to use more then 8Ax15V=120W. The specifications of the D-tap connector are 50W max. IDX batteries have a maximum discharge current of 6,3Ah (69W: 6,3A * the end voltage of 11V). I’ve found that my V-mount batteries output 16,4 V when fully loaded, and switch off at 11,2 V.

V-mount plates

There are a few V-mount power-plates:

  • $ 120 Fotga DP500 V-mount with 5 /7.2 / 12V output and rod mount.
  • $ 150 TrusMT V-mount with 5 / 7.2 / 12V output and rod mount.
  • E 129 Dynacore DC mount without HDMI splitter. 5v USB, D-tap / 5V1A / 7.2V2A / 2x 12V2A / 15V (11-17V)5A. Also a 16,8v DC input. Fits to 15mm lightweight rods in any position (blue handles).
  • E 161 + 28 shipping Dynacore DC mount with HDMI splitter. It looks like you have to power the splitter with 5v in. It also looks like this one a USB connector. It comes with 3 power cables, rod adapter and LP-E6 type battery connector. No power adapter. My friend bought it and says that his one is getting really hot, see details below.
  • E 144 + free shipping Pchood battery pinch with HDMI splitter, looks like it is exactly the same as the Dynacore but with black thumb screws. 5v USB / 1x 12V (!) DTAP + 2x12V 5.5×2.5mm / 7.2V / 15V / 5V DC plug. 5V DC in for the HDMI splitter. Price includes 4x wires and 1x rod-connector. I’ve bought this one and it is not getting hot like the Dynacore. My first thoughts:  the Dtap really is 12v regulated power (so max 2A or so), and the HDMI plugs are not very well aligned, so you have to fiddle a bit to get the cables in !
  • $ 200 + free shipping Lanparte V-mount plate. With HDMI splitter. 5v USB, D-tap, 2x 12v / 7.2v / 15v / 5v DC plugs. 16,8v DC input charge interface. The 7.2 v out and 16,8v input are on the opposite sides, compared to the Dynacore model. Also, the holes for the powerplugs are square, instead of round, there is plastic visible at each power connector. I don’t know if this is good or bad, but it looks cheaper. Apart from that it looks the same. On this one, there is also a 5V DC in next to the two HDMI outputs and there also is a HDMI on/off switch, which is not present on the Dynacore. Fits tight on their shouldersupport and on any 15mm lightweight rods (in any position, green handles). It comes with adapter and 5 power cables.
  • $ 99 Ebay power support with  5v / 7.2v / 12v / Dtap and connectors on top.
  • E 90 Wondlan 5DII Power support V mount with 5v / 12v / 7.2v / D-tap. Much smaller then the above. It does not come with rod support, but you can attach it.
  • E 395 Bebob Coco V-Mount Battery Adapt. f. 15mm Lightweight Support. D-tap + 4 Hirose 4p 12V/7.2V Outputs.
  • E 151 IDX P-V284 with 5v, 7,3v, 8,4v OR 12v output on one D-tap, and unregulated 50W output on the other D-tap.
  • Tilta with 9.3V out. Can’t find it anymore. It might have been a custom built, see this thread on dvxuser (you should read it anyway to understand more about metering!)

I have been told that . Here is a nice picture by Lanparte about fake pinches, note that the 7.2V and 16.8V outputs are the other way around.

GH2 on external battery

The GH2’s manual states a 3.4 W avarage power consumption @ 8,4 V = 400 mA avarage. It senses if it is powered from a power adapter or a battery by measuring the input voltage. The power adapter of Panasonic runs at 8.7V, different users reports that you can use a power source between 9 en 8.4 V. Going lower then 8.4 (even just a little, see post 122) will make the camera think it is battery-powered and check if there is a decoder signal available. If not, the GH2 will tell you ‘this battery cannot be used‘ and shut off. It is advised to always regulate this power so that it will not get higher then 9 V.

There are a few commercial regulators from the 12V output of the power pinch to 9V, however:

  • $95 Jag GH2 12v to 7.4v converter including DCC8. Why 7.4 volt? They say it does not have a decoding chip inside and that ‘the GH2 regulates and lower the 12V to a 7.4V’. I wonder how this works with GH2.
  • $ 150 Dolgin Powerplate. You can use an external D-Tap, XLR4 or V-mount plate.
  • $ 170 Switronix XP-DSLR-GH2. D-tap to DC 9.2V 3A. Green & red led to display status of battery power.
  • Mark Vesterskov from Denmark fitted the LM2596 regulator inside of the DCC8. I’m sure this is the best solution so far! You could do that to by using a regulated DC-DC stepdown converter from 9-18v to 8.8 volt. If it has a size of approximately 4x3x1 cm size you could put it inside your DCC8, but it has to be a lot smaller if you want to keep the cable fixation of the DCC8 (see this post #174), like this V7809-1000 one. If you search for a 12V to 9V you might even find something smaller. Make sure it does not get too hot and that the polarity will be right (use an input diode to protect against reverse voltage). You might want to build this DIY indicator onto your monitor.

Please note that a regulator needs about 2 extra Volts on their input for regulating, and there is  5-10% of mah (mA per hour) power consumption on converting. You should also know that there is a regulator in the GH2 that makes it even less efficient a source: As it stands, Keylight’s 780 mA measurement indicates the GH2 is drawing almost twice the power from an external source as from the internal battery. The specs also reveal this: the maximum power consumption with a 7,2 V battery is 780 mA, opposed to 1,2A with the 8,7 V power adapter.

So it might not be a good idea to go from the V-mount to regulated 12 V, to regulated 9 V and then inside the GH2 to regulated 7,2 V and/or 5 V. It would be better to feed it with unregulated 7,2 V straight from the battery. This would be 5,6 – 8,2 V if you’d take 50% of the voltage of the V-mount battery, so that’s a great fit with the GH2 (see later on). It will add another big advantage: you can use the GH’2 battery status indicator and gentle shutdown function.

Unfortunately, this only works with genuine panasonic batteries, since the D pin of this battery will  send status signals from the battery chip (see this message # 131). See here why you would want this ‘decoding chip’. If the right signal is not on this chip, the camera will only work with 8.4 V or more.

GH2 battery indicator

To summarize: the first and biggest challenge is to have the power indicator of the GH2 warning and gently shutting down when the battery runs out of power. This means when the power is running much lower then the 7.2 V average of the battery. But how low?  This could go as low as 6.6 or 6 volts. (see message #152). This guy found that it is a 6.8 V threshold for the last bar of the battery indicator. He also made an adapter that shows battery status by using the decoder from a third party battery!

Ownuser battery-grip

To accomplish the same thing, I’ve bought this great $ 109 Ownuser (Taiwan) battery holder for GH2. Ownuser have a “MIG-PGH2B” model, and a AB or RAB which add a AC power adapter and a IR remote control unit that connects with minijack. I just bought the B model, as I didn’t need the extras. This grip lets you use two batteries and a DC adapter, allowing you to ‘hot swap’ power sources.

This way, you can use the original panasonic in slot A to power up the camera. I’ve tested this, you need it only for the first 2 seconds and can take it out after that, This allows you to use a third party battery in slot B or plug it into the 4,0*1,7*8mm DC plug of the grip with a 7,2 – 9 V power-source. The strange thing is that this DC input requires 9V. I’ve emailed them to ask but they are shure it should be 9 V. I’ve bought it to test it with the 7.2V output of the v-mount batteryplate. As far as I can see (i’ve tested with 5V and 7.2V) the power-input is unregulated. I guess they state 9V to make sure that it is always higher then the voltage of the batteries.

I found that this way, the camera’s battery status indicator and gentle shutdown works great. One thing though: the indicator will only go down, not up (so once a threshold is passed and it only shows one or two bars, it will not display more bars when you insert a full battery).

Battery level indicator test

So I’ve been doing some testing of my own. This is my test setup with the ownuser batterygrip:

Here are the results:

  • 3 bars: 7,9 (*) – 7,16 V
  • 2 bars:  7,15 – 6.76 V
  • 1 bar: 6.75 – 6.30 V
  • red blinking: 6.29 – 6.10 V
  • shutdown: 6.09 V

Please note that these are measurements taken at the output of the ownuser batterygrip’s PCB, with the GH2 on and only an original LUMIX battery in the grip. you take out the empty battery (6,09V) and measure it, you will see 6,5V or (depending on time and temperature) even 6,7V. This is because you are now looking at the battery ‘unloaded’: there is no GH2 connected to it. But if you put in back in the camera it will show the ‘no battery power remains‘ warning and shutdown immediately. Also note that the threshold values will be higher when you attach a M4/3 lens with electronics in it. I’ve also tested with the 12-42 stocklens and got 7,25 V instead of 7,15 V as the 2 bars threshold.

* The power input from a battery should be under 8.4 V (see here, message #138), if it is higher the battery will be seen as external power and the camera will not display the power indicator. But is this REALLY true? What does it do if there is a decoder and the power input is 9V btw, does it give a warning?

Third party battery testing

This brings me to my third party battery I bought at DealExtreme: this battery does not give a ‘this battery cannot be used‘ warning which is great, but it also doesn’t display the battery status indicator. I’ve filed a complaint with dealextreme and they removed it from their website. But be aware when you find a similar product elsewhere:

At first I thought it would not have a decoder, so it would be > 8.4 V. But when I started measuring it it looks like it really is a 7.2 V battery:

  • real battery: full = 8,35 V / Empty = 6,5 V / battery status indicator = yes / discharge time when shooting static scene = 2,5 hours
  • fake battery:  full = 8,35 V / Empty = 0 V / battery status indicator = no / discharge time when shooting static scene = 1 hour

There are three conclusions: 1/ the fake battery shuts itself down at a certain battery-level, like the V-mounts do; and 2/ the fake battery is not really 1200 mAh but more like 1200 mAh / 2,5 = 500 mAh; and 3/ there is a third camera mode between original battery (decoder) and DC power (> 8,4 V): under 8,4 V but no status indicator.

Third camera power mode?

So it seems like there also is the option of having a true 7.2 V battery with a decoder, but still NO battery status indicator. Bummer.

So I thought about putting this battery in the ownuser batterygrip and measuring what happens on the D and T pins of the battery. But then I got the ‘this battery can not be used’ message on the GH2. So I’ve checked and double-checked, but I am sure: the fake battery does work when inserted directly in the camera, but not with the ownuser batterygrip. Clearly: the ownuser grip is doing *something* with the signal on one of the pins of the battery. Knowing there are only three cables going from the grip to the camera, I took apart the battery block of the ownuser and found that the T-pin is connected to the – pin:

ownuser battery-sized block GH2 inside

I don’t know what to think of this exactly, but I’ll go with the idea that the fake battery is using a ‘decoder’ circuit on the D pin that does not like it if the T pin is shortcut to the – of the battery, through the grip+camera layout.

But on the other hand, it might not be the T pin that’s the problem, it might be the D pin that is in some way connected to the T inside of the battery. This is because I found another really strange thing, which is that I could measure 9 V on the ownuser output at a certain grip switch setting (grip with A = lumix and B = fake, no DC in):

+  pin => B: 9,0 / DC: 7,3 / A: 7,2 V
D pin => B: 8,4 / DC 4,5 / A: 4,4 V

note that I’ve also found that you can charge the batteries inside of the grip by changing this switch to A and B position. This way, the output voltage will be avaraged. If you don’t want that, you can set it to DC and put the original battery in the A-slot!

This 9V at B setting was interesting, so I tested it a bit more. I found that it didn’t matter if I put the fake battery in the A or B slot of the grip. So I put it in the A slot and started testing. The voltage would be 8,20 V with the camera off and the switch set to A, but it’s 8,14 V with the switch set to B or DC. Then, when I put the block into the camera it would stay 8,20 V with the switch at position A but drops to 8,06 V with the switch in B or DC position. When I switch the camera on it goes up to 9 V exactly (A position), 7,61 V (B) or 8,65 V (DC).

Looking at D+ when the switch is in position A, it starts with 7,43 V unloaded. When you insert the block in the camera it rises to 8,16 V and when turning camera on it drops 7,85 V and stabilizes at 8,36 V. The strange thing is that there also is voltage on the D-pin with the switch set to B, even if that slot is empty (0 V unconnected, 8,06 V connected and 4,56 V with camera on. Another strange thing are the D- values, starting at 0 V, then going up to about 1,2 V and stabilizes at 0,65 V when the camera is connected (switch in A position). When the switch is in DC position these values are even higher, more like the original battery. The camera displays ‘this battery cannot be used’ and turns off.

I don’t understand why and how yet, but this might be another reason that it’s decoder does work in the camera, but doesn’t work in the grip.

Comparing battery pins voltages

Unfortunately this was a dead end on my preferred testing method. So I tested directly on the unloaded outputs of the batteries and the batterygrip to try and compare them.

GH2 battery levels all pins unloaded

Note that this is unloaded (the batteries are not connected to the camera). Again a few conclusions:

  • Fake battery has a small electrical potential difference between D/T and -/T, while the other setups have D and T at the same level as  the -;
  • The LUMIX battery has a small difference between the values of T and +, so I measured the resistance between – and T, which is 6,9 kOhm;
  • The LUMIX battery has a 108 kOhm resistance between D and T pins. I’ve not found any other resistance values.
  • The LUMIX battery’s (both direct as throught the grip)  D pin starts at about 7,6 V when the multimeter touches it and then drops quickly to 7,14 V.

D pin and T pin

I am not into electronics, but going on the above measurements, I guess in the LUMIX battery there is a capacitor on the D (decoder) pin that unloads when it is connected to the camera. On the T (thermal safety) is a 103A thermistor which indeed has a base value of 6000 Ohm. This thermal safety is for charging only, that’s why ownuser have just connected it to the – of the battery, as if there is no resistance. I’ve checked if it is needed by taping the T pin of the LUMIX battery, but this giving the ‘this battery can not be used message’. Then I taped the T pin of the fake battery, and this one just works (but still without battery status indicator) so yes the T pin is needed in case of < 8.4 V and/or a proper decoder.

Loaded decoder test

Knowing that the first two seconds of powering the GH2 matter for the genuine battery test and the indicator, I tested this with a 6,96 V Lumix + 8,34 fake battery in the grip. The unloaded output of the grip is 7,42 V. When I turned on the camera it drop sto 7,2 V shortly and then stabilizes at 7,29 V. The corresponding values of D+ are: 5,88 V (lumix) translates to 6,24 V on the output of the grip. Then, when I turn on the camera it drops to 4,83 V, raises to 6,30 V and then stabilize on 4,22 V. The values of D- are: 0 V with camera of and stabilized at 3,07 V when the camera is on (D+ & D- = -+ / 4,22+3,07=7,29 V).

For now, I am perfectly happy with using the ownuser battery grip. Later on, I might want to disassemble a battery to try to make my own small decoder that fits into a battery-sized block. So let’s focus on the V-mount again.

Back to the V-mount

I bought the Cinematics battery-pinch from the above list. I’ve attached the 7.2 V output of the battery pinch to the DC input of the ownuser batterygrip using this $ 3 curly cable with blue 4,0*1,7*11 mm plug for the ownuser side, and a black 5,5×2,1×12 mm plug that fits into my battery-pinch. Unfortunately the blue plug on this cable is 11 mm long and the ownuser batterygrip only takes 8 mm, this is not a huge issue but it would be good to look for a slightly shorter plug. I will only use the genuine panasonic battery to start the camera and then take it out to keep it as spare battery. I could also try to use an empty battery and leave it in the grip, but then it might charge from the DC input or influence the grip’s output voltage, I don’t know yet.

The CityTek V-mount batteries output 16,4 V when fully charged, and switch off when they reach 11,2 V. The Cinematics battery-pinch is outputting regulated power from its 7,2 V output, which stays at 7,3 V (tested with camera off) at all charge levels of the battery. This drops to 7,2 V when I turn the camera on, and as the batterygrip is also using a bit it will output about 7,1 V to the camera. So I expect the camera to display 2 bars battery status. But the problem is, that it will stay at this level until the battery switches off! Unfortunately, this means that the camera is not aware of the real status of the V-mount battery.

So I have part 1 working: running the camera on 7,2 V instead of 8,4-9V. But the second part (battery status indicator) is not working as I would like because the 7,2 V is regulated. I remembered having a V-mount battery converter for my JVC HD100. This is also outputting 7.2 V, but my HD100 knew the status of the battery so I guess it is unregulated.

I’ve started a test with the IDX ProHD adapter connected to the Ownuser batterygrip. With a full battery and the camera on, the output of the Ownuser is 6,83V (camera shows 2 bars), of the IDX is 7,24V while the V-mount battery’s output is 16,32V. Stay tuned! 14,68 / 7,22 / 6,81 = 12,43 / 7,20 /6,79 // 10,46 / 7,21 / 6,78. To conclude: the above 11,2V shut-off limit of Vmount battery might not be right, it might lower. And: the output of the IDX is regulated.

Then I measured the T and + pins of the IDX: the 16,3V battery translates to 8,9V and the 13,2V battery translates to 5,8V. So this information should be connected to the GH2. The only problem is that in this case, the + is the negative, instead of the T that is used in the GH2 as negative… To be continued

Conclusion

In the end, I will have my unregulated battery-block sized D-tap step-down converter with built-in decoder ready when the GH3 is introduced 🙂

Footnotes:

  • Plugs: I guess most of this gear is using 2.1mm DC input jacks, I’m not really a big fan of those. I’m not really a big fan of those (and Panasonic used a non-standard size that is 0.5mm smaller for their DCC8: The plug is 1.7mm inner diameter (ID) and 4.75mm outer diameter (OD) like this one from Amazon.). I’ve had plugs falling out, being too short or the inner side wearing and not connecting well (or breaking the circuit in the equipment). I like the 4 pin Hirose or Lemo plugs a lot more, but am not sure which of these is industry standard.
  • Batteries. Make sure it has D-tap and power-indicator, like the Wondlan Vect 95Wh (6,4Ah) for E 169
  • There also are cheaper alternatives, that  do not fit to the V-mount but is cheaper or more versatile! Like the Hobbyking 5Ahx14,8W battery for only E 25,-. This also is nice, a 12V+ 5V DC pack for CCTV, only $ 18. There also is a $ 30 portable 12v/9v/5v li-ion version, which is perfect for the GH2!  Unfortunately, they do NOT show capacity when your shooting!
  • lot of people use the $140-$300 Tekkeon 5-19v batteries, that has it’s own $ 90 15mm rod snap adapters,but I don’t think that is much cheaper if b.t.w.).
  • There are nice extra features like this switronix hotswap V-mount.
Posted in: GH2