Re J820 Batteries

Forgive this thought if this has been disscussed and put aside. Has consideration been given to the use of 7 1/2 volt mobil phone batteries? They are rectangle and thin and should fit well in the plastic case. Thoughts please?

No, I'm glad you're reviving this discussion - we've been trying to find a solution for some time:

http://www.hpcfactor.com/forums/forums/thread-view.asp?tid=9927&posts=89

We'd need to know at least two things: 1) the amount of current (mAh) the battery supplies; and 2) the polarity of each of the contacts. 'Course, I'm far from an electronics expert, so maybe the more knowledgeable members here have a comment or two.

Edited by CE Geek 2008-08-25 6:26 PM

I am far from being an electronic expert too. However, whilest the size/dementions of these batteries may be smaller the advances in battery technology over the last ten years have be huge. You only have to look at the progress in the AA battery to see that. I read somewhere that these advance in battery design and performance are what makes the electric car more likely. Just think it is all down to mobil phones and digital cameras.

I will go down to my local mobil phone supplier and have a talk to them in the next couple of days. Physical size is also important. I do not know the original physical size of the J820 batteries. Especially their thinkness. I don't mind if they are smaller so much I am sure they can be mounted in the battery case and stuck there if necessary using some tacky substance to stop them from moving about. Heat would be the problem there.

Another question. When compare to standard lithum pollomer batteries are the original batteries in any way different. Are essentailly just standard fancy standard batteries? Using Mobil Phone batteries by their very nature will have to be a work around solution. Not perfect.

In the case that these batteries are not perfects as regards overall current output it will be a case of better this than no solution don't you think? It as I said will have to be a work around solution. Maybe a combination of solutions maybe require if these machines are to continue to operate. It is either something like this or the rubbish bin.

In posting these thoughts I was hoping for a little more response. It isno good reinveting the wheel if some one has already considered this idea and put it aside. The other problem will be that the people selling the mobil phone batteries don't really have a great produce knowledge about the batteries they sell

I will get back

Hi

Have quickly checked out mobile phone batteries/cells for use in the Jornada 820. Firstly, a correction on my first thread. The majority of Mobil phone batteries are 3.6, 3.7 or 4.2 volts. Not 7.2 volts. The original Jornada battery cells were 3.7 volts

Size wise they come in at about the same deminsions at the originnal batteries. You may even be able to get six of the into the battery case. I beleive the extended form of the battery had six cells. I don't know of the power board arrangements used by HP will allow for this in the standard four cell battery case.

mAhours. I check on the internet and a battery retailer. Whilst they range from 500-1000 mAh the majority were from 750-850 mAh. An occational one was 900 mAh. They were usually 4.2 volts. LG Batteries seem to have the largest range for our purpose.

Regarding positive and negative markings. The ones that I saw were all properly marked on the battery case. However, some had three termials and others four. This must have something to do with the recharging circuit.

Now to the cons

Most batteries come unwired. No leads attached. Therefore, to make them work leads would have to be soldered to each of the appropriate terminals. Not really recommended. Li-polymer and Li-ion batteries can explode if too much heat is applied to the battery it self. Another way of attaching the leads should be investigaed.

The retailer also showed me a wired battery pack. Of course whilst they are small they were far too large to fit into the Jornada's battery case.

The mAh are not quite at the same level as the original batteries. But in this case, if no better solution is found anything is better than nothing. We could all go and buy an ASUS EEE PCs and bin or put our Jornada 820s into storage only to brought out on special occations to look at what was. May be a combination of solutions might be the best eg. smaller (mAh) cells combines with a 12 volt rechargeable battery pack.

Some further questions. Help Pease. Did the original Jornada 820 battery have a 'Protection Circuit Board' (PCB) built into it somewhere. Was it part of the battery or on the internal battery circuit board. If there was one where was it located.

With all the trouble people are having with getting correct equivalent batteries when there seems to be a number of options available what makes the Jornada's orginal battery cells so special/different? I really don't understand. If this could be explained to me it would help me when I talk to battery people about the Jornada's requirements.

Finally, has anyone tried out refilling/rebuilding the old battery cells with new cells? If all else fails this might be a good solution. This is something I will have to investigate.

Robert