Contax RTS-2 Battery Compartment Cap Problem

[mtjade2007]

I recently ran into a battery running out of juice problem on a road trip with my Contax RTS-2. I checked the 4lr44 battery which had 6.0 volt the night before the trip. Checked it again when I returned home and found it had only 5.5 volt remaining. The camera drained the juice I thought. Bad news!

I installed a brand new battery again with 6.2 volt and checked the camera. It worked fine. Removed the battery and found it dropped the voltage down to 5.8 volt. Hum... Really bad news then!!!

I removed the camera bottom plate and soldered a piece of wire to the positive terminal of the battery compartment and set up my digital meter in order to measure the current flow trying to find how the battery was drained so quickly. What I found was very interesting. The current draw was 0 before turning on the camera. It drew 3.7 ua (micro amp) when turned on but no pressing of metering button (no LED in the view finder was on). This was actually perfect. If I left the camera switched on all day it would not really drain much juice out of the battery if the current drain is only 3.7 ua.

The current draw was about 8 ma (mili-amp) for a split second when the shutter was fired. This was OK still. I don't think the camera has any current draining problem at all. Hum... So why my battery lost the juice so badly? It tuns out it is the battery compartment cap that has a design flaw.

The way the cap is designed could easily short out the battery at the moment the cap is screwed in. I tried it with 2 new batteries. They both started out with 6.2 volt. Just installed them then removed them right after and the voltage dropped below 6.0 volt. The camera will work at 6.0 volt still so you will probably never know that the battery has been shorted for maybe a second depending on how fast you screwing in the cap. If you struggled to screw it in the battery could be shorted multiple times badly. The camera will still work if the battery has more than 5.6 volt I think. But you might have lost quite a bit of the battery useful lifespan.

I carefully checked the battery cap and there is nothing wrong with mine. By looking at the cap I realized it really can easily short out the battery the moment the cap is screwed back in. If you have a RTS-2 you will see what I am talking about. It is a design flaw. I don't think there is any easy way to correct the problem.

 

[shutterfinger]

Post some pictures of the cap, battery compartment, battery.

 

[Trask]

My understanding of a "short circuit" in this instance would be that the two terminals in some manner come into direct contact, like if I touched a wire to one terminal and the other end of the wire to the other terminal. No load (i.e, camera electronics) between the two terminals to impede/use the electron flow, so the battery goes flat quickly, probably while heating up in the process. I just looked at my RTS II again to refresh my memory. The negative battery contact goes down into the vertical battery tunnel, which has a spring-loaded terminal at the bottom. So the negative contact can only touch that terminal, and the battery tunnel is otherwise plastic, so no chance of a short there. At the positive end, where the cap screws in, there is a formed flat metal spring that makes contact with the metal screw-in battery cover, thereby completing the circuit. I don't see how a short circuit could occur. I do see that it might be possible for the battery cover to make and break contact with the formed flat metal spring as the owner tries to thread the cover on, but as the camera electronics are not being used no current should flow during any such intermittent make/breaks, And once the cover is screwed on, the circuit through the camera electronics is completed, which is not a short circuit. So I'm having a hard time understanding where a short circuit would occur, and by what mechanism. If there truly is a problem, I'd really like to know as I use my RTS II and wouldn't want to run into a lot of battery problems. (I would have attached photos of my camera and battery to illustrate, but my wife took my iPad to Europe...)

 

[shutterfinger]

Plastics can carbonize if a high enough voltage is applied and or dust has built up on it.
A short can cause a battery to explode, a circuit failure can cause rapid battery drain or short battery life.
If you have a VOM set it to OHMS, and measure between the positive and negative terminals of the camera both with the main switch ON and OFF with the meter leads in matching polarity and reverse polarity. Post the results.

 

[mtjade2007]

Trask, the negative terminal deep inside the battery cell is connected directly to the chassis of the camera regardless if the power switch is on or off. Now you really can see easily if a short can happen or not when you put on the cap tilted with an angel (easily happens unless you are very careful). The cap is in a two layer construction. The bottom layer is for connecting to the positive end of the battery and also for connecting to the wire tap for the positive voltage to go into the camera (to the power switch I believe). The upper (outer) layer of the cap is to be threaded onto the bottom plate (the chassis). So if you tilt the cap with an angel when you are installing a battery the bottom and upper plates can be shorted, especially if you struggle to thread it in, by the bottom plate of the camera. I found out about this because of installing one after another brand new batteries. Before installing them they were measured 6.2 volt. After installing them and fired maybe one or two shots then took the battery out they measured 5.9 ~ 6.0 volt. I nearly freaked out thinking my RTS-ii drained it internally somewhere.

I tried on a 3rd new battery and put on the cap extremely carefully. Fired a few shots then took the battery out. It measured still 6.18 volt. I think it is a proof of the flawed design. Shorting the 4lr44 battery will not heat up the battery nor explode. It is a battery with a quite high source resistance. The current resulted by a short circuit will be very limited. So if you have a short when you install the battery it may still work except with a shortened service life. If you put on and remove the battery frequently and each time causing a short you may find the battery to only last for a few rolls of film.

 

[mtjade2007]

Plastics can carbonize if a high enough voltage is applied and or dust has built up on it.
A short can cause a battery to explode, a circuit failure can cause rapid battery drain or short battery life.
If you have a VOM set it to OHMS, and measure between the positive and negative terminals of the camera both with the main switch ON and OFF with the meter leads in matching polarity and reverse polarity. Post the results.

I checked it and as I mentioned, there was 0 leakage when the power switch was off. It was about 4 micro amp with the switch on. This told me there was nothing wrong with the camera.