frechett@spot.Colorado.EDU (-=Runaway Daemon=-) (04/26/91)
I hope that this group can actually work.. So, here is my first post to comp.sys.hp48.d (ooooooooo doesn't that sound important?) I recently started seeing the little alarm indicator come on when I had no alarms and the calculator was thinking hard.. I realized that the batteries might be low so I went to the diagnostic mode to check the batteries and it shows me that all the batteries are fine.. I then go back and play with the calc some and find that it does it again.. So this time, I take out my multimeter and check the voltages across the three batteries. I get the following numbers. 1.23 V 1.22 V .9 V Now that is quite a significant jump. I know that this sort of thing has cropped up before and I don't remember if it was the hp48 or the hp28 but it was definately the same problem. I don't remember if it was ever resolved or not but I would like to know what people think of this. ian -=Runaway Daemon=-
zielke@duke.cs.duke.edu (David Zielke) (04/26/91)
The battery problem you see with the 48sx is very similar to the problems which I delt with when using a 41CX, expecially when using NiCad batteries. The reason, the machine is CMOS based and they change the clock rate from sitting still to working hard. CMOS changes its power consumption when it is clocked at a different rate. David
jcohen@lehi3b15.csee.Lehigh.EDU (Josh Cohen [890918]) (04/29/91)
I beleive that in order to measure correctly, you MUST have the batteries out of the calculator.. You cant measure with them working.. jcohen@scarecrow.csee.lehigh.edu
frechett@spot.Colorado.EDU (-=Runaway Daemon=-) (04/29/91)
In article <1552@lehi3b15.csee.Lehigh.EDU> jcohen@lehi3b15.csee.Lehigh.EDU (Josh Cohen [890918]) writes: >I beleive that in order to measure correctly, you MUST have the batteries out >of the calculator.. You cant measure with them working.. >jcohen@scarecrow.csee.lehigh.edu I did have the batteries out.. I just replaced them.. And two of them are 1.2 volts and one is .9. It is really odd. ian -=Runaway Daemon=-
csmith@plains.NoDak.edu (Carl Smith) (04/30/91)
In article <1991Apr29.073246.23703@colorado.edu> frechett@spot.Colorado.EDU (-=Runaway Daemon=-) writes: > >I just replaced them.. And two of them >are 1.2 volts and one is .9. It is really odd. > > ian > >-=Runaway Daemon=- I have replaced the batteries in my HP28S three times now, and each time something similar to this has happend. I got my 28S in December, about a year and a half ago. In late January, a month later, the battery indicator came on, so I replaced the batteries with 3 fresh N cells. I checked the old batteries and two measured 1.29 volts, and the third measured 0.45 volts. As a test I placed a 10 ohm power resistor across each cell, to put a heavy load on them. Two still measured at 1.1 and the third quickly dropped to near zero. This shows that the two cells were still near full charge capacity. About two months later, at the end of March, the battery indicator came on once again. So I replaced them with one fresh N cell and the two good ones from the previous set. The ones I took out measured at about 1.0 volts for two of them, and the third measured about 0.3 volts, each with a 10 ohm power resistor across them for a load. I then took notice that the dead one in each case was the one that sits by itself. So I looked at the calculator to see if there was some connection to the metal piece on the battery door, so that the single battery could be drained faster than the others. I could see no such connection. It looks like the three batteries are in series. Therefore there should not be any more drain on one battery than the others, and no reason for one to go dead faster than the others. That third set of batteries, the set that contained one new battery and the two good ones from the set that came in the calculator ran for almost exactly one year. They were put in in late March a year ago, and the battery indicator came on in late March about a month ago. So I pulled the batteries and tested them, to find two good and one dead. The two good ones included the fresh one put in a year ago, and one of the two that were good from the first set. I replaced the one dead one and the calculator and it is still going. The third set doesn't prove anything, since the batteries each had been used different lengths of time before they were put together. But the first two sets were brand new batteries, and two came out good and one dead... This was discussed a while back, but nobody came up with a solution.
rkb@po.CWRU.Edu (Robert K. Brunner) (05/01/91)
I just checked my old batteries, and they all read between 1.16 and 1.17 V without load and ou of the calculator. I removed them when the calculator could not complete an arachive without getting a low battery warning. The serial port is a big load, I guess. Robert