Battery Question

[braeside]

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The corruption to the photos may be as a result of pickup of nearby radio transmissions on the longer battery leads. Perhaps you had a mobile phone nearby? Just a thought.

[Maarten]

Alexander have you seen the battery solution developed by Krauklis for the DMR?

(see Digital Forum) Maarten

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[atufte]

The corruption to the photos may be as a result of pickup of nearby radio transmissions on the longer battery leads. Perhaps you had a mobile phone nearby? Just a thought.

 

That might be it...thx

[atufte]

Alexander have you seen the battery solution developed by Krauklis for the DMR?

(see Digital Forum) Maarten

 

Thx Maarten...

[atufte]

If you wire stuff together as indicated in the schematic then the variable resistance (trimmer) R2 can be used to adjust the output voltage.

 

If you believe the datasheet then you could even use the equation to figure out the resistances, let's see 3.7 = 1.25(1+R2/R1) & forget the rest as the current is only 50 microamps, so then 3.7/1.25 -1 = 1.96 = R2/R1 then we go to the preffered numbers for resistances and the E48 series gives 196 exactly as a option so you could use R2 = 1960 ohm and R1 = 1000 ohm, color coded repectively 1.96K = Brown, white, blue, brown, red and 1K = Brown, black, black, brown, red see here for a resistance color band device.

 

Thanks Stephen...

 

How much will you charge for making this 3.7 V regulator for me, this is way past my knowledge...?

[SJP]

I guess I can help with this, do we know the current and voltage we need to deliver to the M8? That is the first thing, the rest is easy except for the final mounting into the empty battery case. How do you propose to do that?

 

Maybe it would be worth asking the company that made the DMR external supply whether they can do it for you? Then it is their problem and may also generate a market for them as there must be other M8 users that would be interested.

[atufte]

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I guess I can help with this, do we know the current and voltage we need to deliver to the M8? That is the first thing, the rest is easy except for the final mounting into the empty battery case. How do you propose to do that?

 

Maybe it would be worth asking the company that made the DMR external supply whether they can do it for you? Then it is their problem and may also generate a market for them as there must be other M8 users that would be interested.

 

Thanks Stephen, if we get the regulator set up, and ready for soldering, it should be easy to get it fitted into the emty battery case, i guess it should be only to solder a red and black lead onto regulator,(or can you do this?) and with a short connection to + and - on the battery circuit board?

 

I have already been in contact with them, so maybe wait and see what their answer would be first?

 

Thx

 

//Alex

[marknorton]

Far be it from me to pour cold water on your efforts but extreme caution is called for. There's a lot of Radio-Shack level opinion flying around here and as for the assertion that the staff in such stores have a lot of knoweldge, do you honestly think they would be eeking out a living in retail if they were any good?

 

First, have you noticed how the noise from the wind-on motor is the same whether the battery is fully charged or breathing its last gasp. That's because the battery is not used to power the camera directly. Instead, there's a series of switching power supplies (6 on the DSP board) alone which generate the required voltages for the electronics and there's also another one on the shutter controller board. Picture time....

 

This is the shutter controller - the section at the top is the power supply - the square ferrite component marked 4R7 is an inductor used by the very clever switching regulator, a Linear Technologies LTC3421. On the right is the Sanyo chip used to drive the motor and bottom left is the inferface for the shutter electromagnets and the optical slot sensors.

 

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On the DSP board, you can see the same inductors for each of the 6 power supplies for the Maxim 1567 power controller on the other side.

 

 

Regulating the battery voltage down is a pointless exercise because the voltage drop across the regulator (especially the passive types of regulator being suggested) is dissipated as heat and if you tuck it up inside the battery container, there's no place for the heat to go. Besides, the heat is created from some of the battery capacity you are trying to stretch.

 

I've made these comments on another thread, but if you look at an M8 battery pack, you will see 4 connections, 3 of them are used when charging the battery, the third (in addition to + and -) being a temperature sensor so that the charging can be stopped if the battery gets hot and bothered.

 

When in the camera, the 4th connection comes into play and the camera can query the state of the battery from the chip built into the battery which counts charge in and charge out - a bit like a car park sign telling you how many spaces there are left. Therefore, if you want normal operation, the battery circuit should be retained (with its added protection for over current and over temperature) and the extra battery capacity provided the other side of the circuit so that the circuit is between battery pack and camera when being used and battery pack and charger when being charged.

 

If you have more than one 3.7v nominal cell, it gets more complex because you can't just charge the cells in parallel as you can with NiCads, each cell needs to be charged separately and there needs to be load balancing on discharge so that you don't end up with one cell trying to charge the others. That is why, on a multi-cell battery pack you have multiple pins, check out your lap top battery. Each separate cell + and - needs to be made available externally for charging.

Edited February 23, 2010 by marknorton

[SJP]

Good point - I am also a bit concerned about the charge monitoring electronics that the M8 is expecting to see.

 

Nevertheless Alex's first attempt seemed to work to some extent. The regulator heat management could be a problem depending on the currents involved. If is 1A max then it will have to dissipate 1 watt roughly, but that presumably is not continuous load so I was hoping that the heat would not be problem.

 

How about keeping the set-up as it is and just putting a capacitor into the battery holder? Then we can see if the pictures show less banding and it is only a minor modification, 100 microfarad electrolytic capacitor (max20V or higher) should fit.

[marknorton]

So here we have the 5 connections from the battery pack to the camera and you can see the positive and negative have wires connected which supply the power to the DSP board. The 3 connections in between are all connected to the camera microprocessor for battery state monitoring. Only one is populated in the battery itself (the middle of the three) which is presumably there to allow a different battery to be used (with an appropriate firmware change). There's a missing position in this group of 5, there's an extra position beyond the positive connection which is populated in the battery and used only when the battery is connected to the charger for the temperature monitoring I described.

 

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In the second picture, you can see how the connections make it to the multi-pole connector which is used to connect to the camera control circuit board. Look for the thick tracks and the spider's web connections to multiple pins to provide the required current carrying capability from the connector pins paralled up. The 3 status lines from the battery pins are connected to other pins in the connector.

 

 

The remaining pins in the connector run to the lens detector circuitry which is part of the same flex print and runs down the front of the camera behind the battery housing.

[atufte]

Thanks for all of this info Mark...

[atufte]

Good point - I am also a bit concerned about the charge monitoring electronics that the M8 is expecting to see.

 

Nevertheless Alex's first attempt seemed to work to some extent. The regulator heat management could be a problem depending on the currents involved. If is 1A max then it will have to dissipate 1 watt roughly, but that presumably is not continuous load so I was hoping that the heat would not be problem.

 

How about keeping the set-up as it is and just putting a capacitor into the battery holder? Then we can see if the pictures show less banding and it is only a minor modification, 100 microfarad electrolytic capacitor (max20V or higher) should fit.

 

I think this is a good idea, any idea where to get one?

Is it easy to fit this capacitor, or is it just +- or is this a advanced setup...?

[SJP]

Fitting the capacitor is easy - just connect the + side of the capacitor to the + lead and the - to the - , the capacitor goes inside the empty battery pack - close to where the power goes into the camera. It just acts as a reservoir for the voltage from the external battery.

 

Buying parts like this is usually easiest via an electronics parts store or TV repair shop. I am pretty sure a place like Olso would have such a store. Cost is about 50 eurocents I expect. If you can get a bigger capacitor to fit into the case then that is better - even 1000 microFarad might fit. The voltage rating of the capacitor is not essential so long it is nicely above the battery voltage. Note a higher voltage rating means the capacitor will be larger in size, so a 100V electrolytic capacitor of the same capacitance will be larger than a 20V electrolytic capacitor.

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[SJP]

Note/question to Mark

 

I get your point that the M8 internal powers supplies are separately regulated but the pictures Alex showed had banding similar to the effect you get at ISO 2500, but more extreme. If I recall the 2500 ISO banding is believed to be due to voltage ripple (Leica even claimed to be working on a method to deal with it???) so this was my initial guess. This would not be an explanation for high ISO banding if the internal M8 power supplies are very stable.

[marknorton]

The reason Li-Ion batteries are dangerous is because they can deliver very high currents; they have a low internal resistance - a bit like lead acid batteries - and if a high current flows unchecked, they can overheat and blow apart which is the reason for the protection circuitry. As Pete says, the fuses are there to protect the battery not the circuitry it might be connected to.

 

That same characteristic though makes them suitable for battery powered equipment where the current demands can peak, such as in the M8. They shrug off a momentary increase in demand and the voltage they are supply changes little.

 

The problem with AA batteries is that they have (depending on the terchnology) a rather higher internal resistance which varies with temperature and battery condition which mwans they cannot consistently meet the current demands of the camera without the voltage falling, perhaps to levels below where the camera's power supplies can compensate.

 

Alex might have found, for example, that the banding occurs in later pictures in a sequence where the first from "rest" is OK.

 

Stephens idea of adding an electrolytic capacitor is like adding a flywheel - it effectively lowers the source impedance of the power supply; however, a 100 uF capacitor charged to 3.7v stores only 685 microjoules of energy; the camera running at, say, 2A current drain and 3.7v battery voltage requires about 10000 times that, each second so if high internal resistance is the issue, it's not going to help much.

 

It would be interesting to put a data logging 'scope on the red and black wires in my picture and monitor how the battery voltage is changing using the AA batteries.

 

One thing that does surprise me is that Alex got all these shots from the batteries with the battery meter apparently working normally. In my tests, the camera shut down because the battery electronics was telling the camera the battery was empty, however, I realise I was using a "compatible" battery, not wishing to butcher a genuine Leica one, so it's possible the Leica battery electronics are more intelligent. and that might also explain why the experience of compatible batteries is poor.

[marknorton]

Stephen's comment about ISO 2500 is interesting. It may be that Leica are finding the noise performance of the camera is limited not by voltage ripple as such but by noise induced into the critically important A to D conversion circuitry by these switching power supplies. They tend to create and radiate noise and the design of the sensor circuit board in the camera is critical, especially the grounding and shielding arrangements.

 

Coming back to the battery question, you could certainly think of a battery pack like the Leicavit containing a higher voltage/higher capacity battery pack with a DC/DC converter to change the nominal 7.4v to 3.7v without most of the energy losses associated with resistors and linear voltage regulators. You could also use remote voltage sensing so that the required voltage was delivered at the camera, not at the end of the cable feeding it.

 

There's still the issue of making the battery meter work and simulating that interface and I doubt that Leica are about to tell us how it works!

[gDallasK]

Does anyone have a picture (and some guidance) to help me to dismantle a battery case. I want to experiment with alternative cells but the two halves seem to be bonded together. I don't want to attack the case with a Dremel unless I really need to ....

[atufte]

Does anyone have a picture (and some guidance) to help me to dismantle a battery case. I want to experiment with alternative cells but the two halves seem to be bonded together. I don't want to attack the case with a Dremel unless I really need to ....

 

I just used a standard carpet knife, pushed it through on the side, and clicked it open with a turn of the knife blade, very easy and it does not get broken, just replace the glue and it is as good as new...