Rollei 6008i battery thermistors

[OrientPoint]

I recently acquired a Rollei 6008i with a non-functional (of course) battery. I found NiMH cells to replace the spent NiCads, opened up the battery and replaced them. In the process I broke one of the thermistor leads. Not a big deal, but it got me wondering whether it's actually necessary to maintain the thermistors. Internet postings are of two minds on this. There's an iFixIt post that suggests they're "obsolete". The author even goes so far as to fill the battery plugs for the two sensor leads to ensure the battery cannot be used in a charger that requires them. And then there are numerous posts over the years relaying the advice of a "Rollei tech" that they must be maintained in place as the camera uses them for power management of some sort.

My camera came with an ancient "G" charger, which is of no use for NiMH batteries. I repurposed it as a battery tray with leads that go to my modern multi-chemistry hobby charger. In the process of rewiring the old charger I noticed that while the batteries have 6 pins, both charger and camera only have four. The charger includes pins only for the thermistors and non-fused power plugs; the camera includes pins for both fused and non-fused power plugs and omits the thermistor plugs.

My question is: how can the camera use the thermistors for power management if it doesn't have any way to read them? It sure seems like they're only used during charging. And with a modern charger are they absolutely necessary?

 

[ic-racer]

When rapid charging batteries, a lot of heat can be generated. Things can melt and burn. The heat sensing circuit is to keep your house from burning down during a rapid charge.
If you are only going to trickle charge, you shouldn't need a high-temp emergency shutoff.

 

[OrientPoint]

Yes, exactly. You can turn any battery into a torch by ramping the current too high. But with a modern charger and some patience you can easily control this and keep things cool. You don't absolutely need internal thermistors for this.

What I'm really trying to establish is whether the notion that those thermistors are somehow required by the camera in operation are true. There's this underlying tone in some of the posts that if you don't have those resistors in there you'll fry the camera electronics at some point. And looking at the battery and camera I can't see how that could be true. I totally get why they would've included the thermistors in 1990 to prevent the chargers of that time from torching that battery. But I think (and am looking for confirmation) that this is their only function.

 

[ic-racer]

Yes, they are for rapid charge; neither the camera body or trickle charger can access them.

The thermistor on a contemporary peak charger would be just as important as on the older analog charger if you are going to be rapid charging. You could make a hole in the housing and slip a chargers external thermistor in there.

 

[OrientPoint]

The thermistor on a contemporary peak charger would be just as important as on the older analog charger.

Yes, absolutely. But I'm only going to trickle charge this battery. I'm not shooting weddings.

 

[AgX]

How fast could that NiCd battery pack be loaded with its dedicated charger to necessitare temperature-control in first place?

 

[OrientPoint]

The thermistor on a contemporary peak charger would be just as important as on the older analog charger if you are going to be rapid charging. You could make a hole in the housing and slip a chargers external thermistor in there.

I was thinking of doing that actually. There's already the spare fuse hole to use for that purpose. Or I can just fix the existing lead I broke and wire the pins on my tray to run to the temp inputs on my charger. It's not a problem to have those thermistors in there. I just couldn't see how the camera would care if they're there or not, contrary to some of the available internet wisdom.

Thanks for your confirmation of this!

 

[ic-racer]

I just looked back at the 6008i manual. I have been using a hobby-grade charger for my Rollei batteries for quiet some time so I forgot the Rollei charger only trickle charges when connected to a 12v batter (like car battery adapter). So, if using the Rollei charger, the thermistors need to be working as the Rollei charger will always start with a rapid charge.

It is the 3003 that had two chargers, a rapid charger and a smaller trickle-only charger.

 

[AgX]

My question remains, what is a "rapid-charge"?

The standard charging time for NiCd cells is 14h, however for instance at the Metz 45 the NiCds are charged within 5h and still without temperature control.
To my understanding the range between 14h and 4h is called accelerated charging and anything shorter than 4h is called rapid charging. The latter necessitating temperature control. (Either metering directly or by metering cell voltage intermediately.)