question about ram card without battery

[hpmin48gx]

good afternoon group, a few weeks ago I acquired a 1mb smi ram card, it does not have a battery compartment, I have noticed several times that the main battery discharges quickly, the question is where does the memory take the energy to store data, or is it because of that? memory that quickly drains the battery?.

[Joe Horn]

If your RAM card contains a non-removable rechargeable battery (as some SMI and TDS cards did), then it only gets recharged when the HP 48 is turned on. So to fully charge it, you must leave the 48 turned on for a while. This will drain your 48's batteries faster than usual because they are powering the 48 and recharging the RAM card's battery. When the 48 is turned off, the card is only powered by its own battery. If the card's battery is not sufficiently charged, it will lose its contents while the 48 is turned off.

Of course, rechargeable batteries can't be recharged forever, so at some point all such RAM cards will become useless, unless you figure out a way of cracking it open and replacing the battery.

[hpmin48gx]

I put some new batteries a couple of days ago and I have hardly turned on the calculator, if the charge runs out in a couple more days, does that mean that even with the calculator turned off, the card would be consuming the battery so this card would be defective? a little more information to those who have this type of card

[Joe Horn]

(01-30-2023 01:00 PM)hpmin48gx Wrote:  ... does that mean that even with the calculator turned off, the card would be consuming the battery ...

The card should not draw any current from the AAA batteries in the calculator when the calculator is turned off. The card only draws power from the AAA batteries when the calculator is turned on. If the card draws a lot of power when recharging, and doesn't stay charged for long, I'd conclude that its permanent rechargeable battery is no longer rechargeable and the card is effectively dead.

[John Keith]

I don't know what type of rechargeable batteries these cards used, but many battery types, including Ni-Cd, are effectively a short circuit when they are dead. In this case one would expect the card to draw current from the calculator's batteries even though the rechargeable battery is not capable of being charged.

[hpmin48gx]

Indeed, after 4 days the main batteries ran out, the ram card is with the information stored, but what can be concluded? So the card is already defective?
but it keeps the information but changing the battery every 4 days is not viable either, so what do you advise me? I consider it defective

[hpmin48gx]

The only thing that also occurs to me is to disassemble the card and put a 2016 battery on it

[rprosperi]

(02-02-2023 08:28 PM)hpmin48gx Wrote:  The only thing that also occurs to me is to disassemble the card and put a 2016 battery on it

Not necessarily a good idea - as this card was designed to charge its original battery when the 48 is on, this will now apply some current to the non-rechargeable battery which is never a good thing. The applied current will not be large, but it still can cause problems and damage, I would not risk a working 48GX this way.

Probably best to consider it defective and replace it.

[hpmin48gx]

okay. Thanks for the answer and yes, with this it would be confirmed that cards of this type are not good and it is preferable to buy those that do have a battery compartment.

[Kiwi]

You could replace the dead ML2016 battery by a new one. By carefully removing the front metal label, you can access the battery.