Rollei E36RE Excell Battery 12V Rebuild

[ic-racer]

Can you send it to ic-racer[at]hotmail.com

 

[Fujicaman1957]

IC-racer....

I haven't forgotten you. My scanner is out of order so I can't scan the wring diagram. When scanner's fixed I'll get it to you.

 

[Fujicaman1957]

IC-racer-check your email

 

[ic-racer]

Ok got it (plans to use 12V gel cell for E35RE flash ) but I'm not sure how you get the 12V into the flash. Do you have an adapter that replaces the bottom part of the E36RE battery holder? Or does it plug into where the E36RE charger plugs (3 prong).

 

[Fujicaman1957]

I made what I called a "slug" out of PVC pipe with copper pipe caps at each end that fit into the battery compartment. You'll need to drill a hole in the battery compartment cap and the copper cap for the positive end and solder the positive wire to the copper pipe cap on that end and then do the same (solder) the negative wire to the copper cap on the negative end. Then, epoxy the copper caps into the PVC pipe making sure you have the length the same as the stock battery.

 

[lejaune]

I know this thread is now old, but I think it may still be relevant for the Rollei E36RE users since the original batteries are no longer available. I have read a number of sites (including this one) on less expensive solutions than the $65 Excell. I decided to make my own using commonly available 18650 Li-ion battery and a DC-DC converter to generate 12V. Here is a photo of my concoction.

The red 18650 battery is salvaged from an old, dead laptop battery pack. Ususlly, a battery pack dies if one or two cells die and the rest of the cells are still Ok. I measured the capacity to be 1970mAH. A new, fresh one is often labeled 2000-2500mAh. The green case is 3-D printed to be the same size as the original Ni-Cad battery. I used a 18650 battery holder to make the wiring simpler. The DC-DC converter is a small board in the little compartment next to the battery. The converter costs about $1 a piece on Ebay.

It works but the recylcing time is longer than with the original Ni-Cad. Also, the converter is always connected and drains a small current even when the flash is off. The original battery has a capacity of 500mAh at 12V, which makes it 6Wh. Assuming a 85% converter efficiency, the Li-ion has a capacity of 3.7V x 2000mAh x 85% = 6.3 Wh. So they are comparable. If you use the newer 21700 LoFePo4 cells commonly used in new EVs, you can get twice the capacity, and still fit into the volume.

Another limitation is obviously I can't charge the battery while inside the flash by using the Rollei charger. I have to take the cell out to charge it.

 

[Andreas Thaler]

Apart from your engineering work, the label on the blue battery pack from Varta in German is also interesting.

You can actually only find labels like this in English, so I think the Varta battery pack is from the 1980s or earlier.

 

[lejaune]

Apart from your engineering work, the label on the blue battery pack from Varta in German is also interesting.

You can actually only find labels like this in English, so I think the Varta battery pack is from the 1980s or earlier.

You are probably right. I bought the flash with the battery around 2005, but the battery was already dead. I had been using another battery with light blue skin, without label, and that battery is now also dead.
I use the flash occasionally with my Rollei 35. The flash has a high voltage trigger circuit, not suitable for newer electronics.

 

[ic-racer]

Very nice. Thank you for keeping the thread current.
I'll admit that I got two of the Metz flashes the work with the Rollei TTL system, and have not used my e36re as much since then. Mostly I use the e35re with my 2.8F and Horseman 6x9.

I have one with a bad capacitor. One day I'll fix that.

 

[Bushcat]

It works but the recylcing time is longer than with the original Ni-Cad.

There are two things you may want to check: the current discharge rating of the cell, and current rating of the DC/DC converter. Continuous discharge rates for 18650 cells can range anywhere from 0.5C to 15C (1A to 30A in your case), but the cheap-as-chips converters tend to have a rating below 1A, so that's probably your weak spot. If you can solve that issue, you also want to accommodate a peak draw way above these numbers for the first few ms, so you might want to consider a cell without a built-in protection circuit, and similarly a converter design without a current limiter: you'd be overdriving stuff for the first few milliseconds or so, not long enough for any localised heating.

Luckily, the popularity of vaping makes it easy to find very high-current cells.

Something like a Samsung -29E has a continuous discharge rating of 2.75A, while the Samsung -40T is up around 35A or 45A if your converter can monitor temperature. If you could show the print on your red cell, we could guess if the cell itself is a potential issue.

 

[lejaune]

There are two things you may want to check: the current discharge rating of the cell, and current rating of the DC/DC converter. Continuous discharge rates for 18650 cells can range anywhere from 0.5C to 15C (1A to 30A in your case), but the cheap-as-chips converters tend to have a rating below 1A, so that's probably your weak spot. If you can solve that issue, you also want to accommodate a peak draw way above these numbers for the first few ms, so you might want to consider a cell without a built-in protection circuit, and similarly a converter design without a current limiter: you'd be overdriving stuff for the first few milliseconds or so, not long enough for any localised heating.

Yes, the converter and the battery are limiting factors. The converter is rated at 0.5A at 12V, which is more of an issue than the battery. The actual measured converter output current can go to 1A but not sustained. The required battery current based on calculation should be about 4 times as much. The flash can draw several amps with the Ni-Cads, so it's obviously under powered. With the converter setup, the flash full output recycle time is about 50 sec, but on auto mode, indoor, it's still quite usable once the flash is initially charged.

The red battery is Sanyo, The label says "UR 18650FM M43A", printed, "MJ5M4CA 007605".

 

[Bushcat]

The red battery is Sanyo, The label says "UR 18650FM M43A", printed, "MJ5M4CA 007605".

5A continuous discharge, peak 8.75A for 4 seconds, originally 2600 mAh, manufactured October 2008. So, it's mostly your DC-DC converter at the moment. But if you sort that out, you may want to try an uprated cell, too.

 

[lejaune]

Thanks for the info!
I will leave it as is for now. I think upgrading the converter will require better heat dissipation and better material. The 3D printed case uses PLA material and it starts to become soft at above 45 degree C. ABS would be needed, but my printer can't use it.

 

[Bushcat]

Although I think the project itself is great, you're always going to be current-limited. Looking at the original Varta cells, I'd have probably just bought a bunch of H330's or similar, with the bonus that, if you close your eyes and put your fingers in your ears, the original charger might work, too.

Heh... the original battery pack seems to have a National/NATO stock number: NSN 6140-01-140-7758. So it's still being made by up to 5 manufacturers.