41CV Battery Life


Hello all,

I'm new to the forum, but have been following it for a few months and rejoined the fray quite recentky when I acquired a 41CV with Time Module, X-Functions Module & Quad Module (like many other, my dream machine of the 80s).

For a very short background, the first calc worth mentioning I ever played with, on which I did my first stints at programming, was a 67 borrowed from a friend. That was too expensive, so I moved to TI57 (lost), then 32C (NOK) and finally Sharp PC1500 (still working fine!).

I know the Quad module is useless with it, but in the absence of evidence that it is really incompatible, I've left it in the calc for fear of losing it.

I also added a NoVRAM module (an incredible package, thanks Diego).

Modules are arranges as follows:
Slot 1: Time
Slot 2: NoVRAM
Slot 3: Quad Mem
Slot 4: X-Funcs

The first time around, I found the battery life was a bit short, so I recorded the date I last changed it: jan 17 06

Today, when I switched it on the BAT indicator lit up. After 7 weeks!

So my question is: what's the typical battery life for a CV like mine (I thought it was something like a year rather than weeks)?

Any idea what could be the cause for such drain? Quad mem? Internal problem?

Thanks in advance for any suggestion that would help me get to the bottom of this.




Hi Francois,

First, I won't recommend you to keep the QUAD RAM plugged in... this will surely conficts with the resident RAM chips.

Under normal circumstances a NoVRAM/NoV-32 requires some 13-17mA while running (that means "just" while you're pressing keys or a program/function is running/performing) the rest of the time it "sleeps", draining some uAmps (mostly like if it was not present at all...)

Chances are that some ill code into NoVRAM's RAM memory iterupst the polling point for the HP-41 to tunrn off thus keeping itself in running mode while you still think your calc has been switched off...

Also, (I know it's my fault but I'm *REALLY* busy lately) the auto off feature was misimplemented inthe last NoVRAM code version, and it could lead to a similar situation, due to the fact that you're also using a TIMER module.

There ser several other reasos that can also produce such behavior and are not related to NoVRAM module:

Your TIMER mofule is *hungry* or it has some unwanted alarms/auto-run programmed that make the calc turns on unadvertedly.

To easily determine which module is involved (if any) I'd recommend you to unplug NoVRAM while not in use (you won't lose a bit by doing so)...

Hope this helps.



Hi Diego,

thanks for the detailed explainations. You have at least convinced me to drop the Quad Mem in my drawer.

You may be right about the NoVRAM...

I removed it along with the Quad Mem and the BAT indicator went off! So I put it back in and it went on again.

I'll leave it like that for a while to see if there is a difference, but would really like to be able to keepp it in at all times. When do you think you can update your code?

Also, I have no alarms running in the Time module. I mostly use it as a watch/stopwatch.

Is there an easy way to measure the consumption of a given module?



Also, I have no alarms running in the Time module. I mostly use it as a watch/stopwatch.
I don't know about the 41cv with plug-in time module, but I use the alarms regularly on my 41cx (as an alarm clock) and a set of batteries still lasts me a couple of years.



You're right regarding TIMER, Garth. It "shouldn't" make any difference in a regular use...

The trouble could arise if some unwanted auto-run alarm sets the calc into ON state repeatedly (if such can occur... I've never done or even try)... mostly besause the NoVRAM will draw current during the whole wake-up cycle.

In any case, this is a fairly unprobable situation, the more likely is that some garbage reached the polling area of the NoVRAM's RAM preventing it from going into sleep mode as it should. If this is the case, clearing the RAM is highly advisable.

If my work (yes, the one I do for a living... ;-) allows me, some more spare time in the next few weeks I will port the "Auto-OFF" bug solution code from NoV-32... not a heavy task but time requiring...

On the best case, any NoVRAM/NoV-32 will reduce your average battery life by a factor of 2 (light use) to 5 (heavy use), it should still last some months though.




OK, so my best bet now, assuming garbage in NoVRAM RAM is the culprit, is to clear it. But how do I go about it? Simply reprogram it with the utility?




Pour effacer la section RAM de ton NoVRAM, tu dois y graver le fichier NovClear.HEX contenu dans le NovRam documentation zip du site de Diego.

Ceci remettra la RAM à 0 sans toucher à la configuration ROM que tu aurais gravée par ailleurs.




To clear the NovRam RAM, you have to use the NovClear.Hex file contained in Diego's NovRam documentation zip package.

Burning this file on your chip will zero the RAM, preserving your ROM configuration.

Best regards.


Edited: 9 Mar 2006, 1:48 a.m.


Hi all,

Although this method effectively erases RAM contents, it also kills Flash ROM requiring two reprogramming phases (one for the ClearRAM, and another one to recover original -HEPAX- emulation) and thus it is somewhat cumbersome... It is necessary in case of "severe" RAM illness though, and that's why it is included.

As far as you've depicted your calculator's behavior, it seem that you still have full functionality, so try this HEPAX based procedure to clean your the RAM memory.

- Write "OK" into Alpha register.

- Assign "CLRAM" to a key of your choice, and set USER mode (just for your convenience)

- place 11 into "X" register. (this points to page #B)

- execute "CLRAM"

- repeat for "X" = 10, 9 and 8... and you're done...

Power cycle your calc for HEPAX to rebuild its FILESYS.

Hope this helps.

Regards from the Canaries



Thanks Diego,

will try this tonight. And check that BAT indicator stays off this time...

Thanks also for _not_ RTFMing me on this, even though I now feel I deserved it... ;-)

And lastly thanks to Etienne for chipping in with the NovClear procedure.

Enough thanks for today!



Bad news...

Nothing changed. I have tried all methods, and the result is the same... BAT indicator stays on.

I also tried a Clonix6P config with the same result.

Any ideas?



The BAT indicator will lit up if you're using the same set of batteries... even with ClonixLP.

That's because your battery are in the very low end of its useful life, so a tiny 5mA *extra* current at power up (with Clonix plugged in) makes the voltage drop below the BAT threshold.

It should be ok if you place a new set...

Best regards.



Hi Diego,

yes, I understand that now, it's just that when it went off after removing the NoVRAM, I thought I could use it as an indicator of the problem...

So, what I'd need to find out is a way to verify that the power drain remains acceptable with the configuration I want to use. Because the problem may well be with the calc itself, but the only way to know right now is to get fresh batteries and leave your module out...




And thanks Diego for stating the correct procedure.

May I ask a small question ?

I have both a Clonix (programmed with the low-power code) and a NovRam and use them fine in a normal 41.

However, I wish I could the Clonix in :

- a 41 CV that I've sped up myself
- or a Blanknut Cx which seems to be factory sped-up. (I'm the 2nd owner and the first one sweared he never opened it).

Diego would you advise me to speed down the CV or is there any other way ?

I do need the Clonix to program a 44468 ROM to control instruments.

Thank you very much for these jewels!



Hi Etienne,

Speed down an HP-41 is indeed as easy as speed it up... these are the good news.

The bad news are that neither NoVRAM code nor ClonixLP can be used in a sepeeded up 41...

In order to get your CV back to nominal speed (360Khz) just replace the cap between pins 9 & 10 of the the nut processor with a 150pF one... Cahnces are that the speede up procedure was simply placing a second cap in series qith said capacitor, so you'll only need to remove the "alien" capacitor.

Mail me if you have find it difficult to locate such capacitor.

Best wishes.



Hi Diego,

Thank you for your answer!!

As I did the speed up myself on the CV, I'll speed it down easily! I'll also solder completely the board as I did with my 41Cs.

As for the Blanknut Cx, I'll open it, follow your advice and report back.

If this works, I think I'll solder the Clonix directly in the Blanknut.

Thanks again and friendly regards from France!



Hi Etienne,

It's ok if you want to permanenetly attach the Clonix module into your 41 shell, just remember you more likely be unable to reprogram it afterwards!

In any case please let me know of your pregress... some pics will be very welcomed too... ;-)





Many thanks for everything!

In my config (all fullnuts):

1) The NoVRAM acts as a backup module with the HEPAX filesystem + 2 ROMS and I move
it from calc to calc all the time.

2) The Clonix is already *in* an old battered 41 which is
a) my Hp-3468 front-end: taking, recording and printing measures with the 44468 ROM.

b) the heart of my IL system with 44468 Data Acq., Ext-IO (Thanks Hans for HpILCOM), Sandbox (Thanks Ángel! If only we could have a fullnut version!!), CCD-OSX (Thanks Raymond!),

As soon as I have the CV or Cx working, I'll gladly report here with pictures!

Friendly regards from France!


Edited: 11 Mar 2006, 3:18 a.m.

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