Custom battery pack

[Shdwdrgn]

OK I'm getting way out in left field here, and since I have a spare Z with a busted touch-panel to experiment on, I'm not too concerned about just jumping in and trying it out.  HOWEVER... if someone can see any immediate flaws in my <evil> plan, feel free to jump in and point them out.

With that out of the way, I recently ran across the Sony #LIS2106 battery pack.  It is 2.75" x 2.46" x 0.15", 3.7V li-ion, 1300mAh.  Ideal size to strap to the back of an SL5x00, and it's the same type and voltage as the original battery.  950mAh + 1300mAh = 2250mAh.     Find the + and - leads, tie them directly to the internal battery (of course the cover would have to be left off, but would be covered by the new battery).

Only one issue I see here.  Will the internal charging circuit of the SL5500 deal with the extra capacity?  The way I see it (and I've been wrong before), tying both batteries together in parallel should safely work with the charging current provided, but of course it will take more that twice as long to recharge.

Assuming this crazy scheme would work, it appears you could actually fit TWO of these battery packs on the back of the Z for a total of 3550mAh, while increasing the overall thickness by a mere 0.15"/4mm, and the weight by 2.3 ounces/65g (again,   )

With the considerable increase in battery power, this may be a worthwhile mod even if I have to use an external charging method for the additional batteries.  Comments or suggestions?

[V-Man]

I am definitely interested in the results of you expiroment.  Let me know how it turns out.  I use the Z extensively at work, but it is kept in my briefcase so a minor increase in size is not a problem.

I think you may have to use an external charger because there is supposedly some circuitry in the lithium batteries.  I am also worried about the results when the battery is exhausted.  

Good Luck, and let me know how it turns out.

[Shdwdrgn]

I'm not sure if this is the same thing you are thinking of, but the battery packs I ordered state they include internal charge protection circuitry.  I ordered 2 batteries today, should be here early next week.  I guess I should start working out how I'm going to tie the new batteries in.  I think the most convenient setup will be to add a new power jack into the case, but I need a temp connector first for initial testing...

Yep I could ramble on all night as I think about what I need to do.  Think I'll stop and just say that I'll post here when I know something.

[V-Man]

I made a bunch of external battery packs (NiMh), but they all use an external charger and the Z's external power connector.  I never got as ambitious as what you are planning.  Good luck and I look forward to hearing your results.

The major problem I ran into using the external battery packs was:
When the battery packs are powering the Z and become exhausted, the Z shutsdown very ungracefully.  It sometimes requires a soft reset in order to bring it back to life.  

Just something to keep in mind during your expironments (gawd I gotta learn how to spell).

V-Man

[technojunkie]

Seing as how you can drop in the battery from a 5600 into a  Cx60 and ouble the life I would imagine that the charging circuitry in the Z would be able to handle the extra capacity fairly well. Just keep in mind that when you add larger packs to your setup you will increase your charging time as well.  The Z's APM might not like it too much but you may be able to tweak that to avoid the low power lock up problem mentioned above.

Good Luck,
If it works I may follow suit

[dougeeebear]

My SL-5500 came with 2 batteries.
When one battery is low, pop in the other one.. thus, twice the battery life. No worries, no fear.
Seems a whole lot easier and safer to me.

Doug

[Shdwdrgn]

The batteries arrived today (wow that was fast!).  The good news is they are actually the smaller of the two dimensions that I found listed.  Actual size is 69mm x 61mm x 3mm.  The wide dimension fits nicely across the back of the SL5500.

The batteries came pre-charged.  Makes things easier for me. :-)  Voltage is sitting at 3.77V.  Right in the range I was hoping for.  

The first test has been completed.  I did a direct hookup from the internal battery to a single battery pack.  I am not certain if these were fully charged before they shipped, but I needed to discharge them for recharge testing anyway.  Starting with two SL5500's, both internal batteries fully charged.  Backlight set to full, and sleep mode turned off.  In the test unit with the extra battery pack, I plugged in a DLink DFC-660W.  The other unit has an 256MB SD card, but no other accessories plugged in.  The stock unit died first, in about 2 hours.  I was rather surprised it quit so soon.  The other unit (with battery pack and wifi) lasted nearly 3 hours before shutting down.  I don't have an accurate measurement, but I believe that when running wifi, I have never gotten more than 30-45 minutes from the battery.

Of course, keep in mind these times were with no actual usage.  Both units were simply sitting on the desk.  Under actual load, the battery life may be decreased.  But so far I'm pretty happy with what I'm seeing.

Now of course I need to wait for the recharge.  The AC has been plugged in for about 20 minutes so far, and there is no unusual heating within the Z.  I will have to watch the recharge time for both units tomorrow and see what happens.

One more note.  These battery packs come with a 4-lead connector, however the red and black pairs are actually tied together.  I will probably desolder the original connector and replace with a straight wire connecting both battery packs into the Z.  I'm only showing a draw of 32mA from the single battery pack, so it won't require a very large wire to supply to current.

That's all I've got for now, but one way or the other, I think these battery packs provide a lot of power for the space.  Tomorrow the recharge and usage tests begin.

[Shdwdrgn]

Just an update on my experiment thus far...
I've been recharging and running down the batteries all day, and have noticed something odd.  Recharge time for a stock Z -- 1:45.  Recharge with the battery pack + internal battery -- 2 hours.  That's too close to be a coincidence, yet I can't deny that the external batteries are being used AND being recharged.

I'm currently running a single external battery (which was recharged fully with the Z this morning) with the wifi card installed, and have Wellenreiter running in scan mode.  It's been scanning for over 2.5 hours so far, yet I'm still showing 30% battery.

Charging tests seem to be going well with a single battery, so later tonight I'm going to try recharging 2 battery packs together from the Z.  Since I've seen no problems up to this point, I think only time and long-term usage will tell if there are any real problems with this setup.

[V-Man]

Recharge time is possibly explained by the following: (provided that the Z uses a standard three stage charger)

1.  Bulk charge.  Amperage is high and voltage is high.  Somewhere around 70-80% of charge is delivered this way
2.  Forgot what this stage is called.  Voltage rises, and amperage is low as the battery is fully charged.
3.  Float charge.  Voltage and amperage are stablized at a point that compensates for the battery selfdischarge.

Note:  I know the above for 12V lead/acid and NiCd and NiMh works well.  Not sure about lithuim though.  If the above is true, the bulk charging stage is providing enough current to charge both batteries in approximately the same amount of time.  The second stage (absorbtion?) is where the time difference comes in.  Of course, I could be completely wrong  .

V-Man

[omega]

I agree with V-man. One thing to note though, i have seen lithium batteries with 3.7, 3.8 etc voltages stated. Be careful that all batteries are being charged fully (or not draining each other)... I suppose you could do this by charging them as you are and then getting a load (an appropriate resistor maH/10 for current suggestion). Then see how much you can get out of the battery down to the proper voltage point (read about it on net).

If the batteries were mismatched (internal vs external) it might be better to use the two external 'matched' batteries and leave the internal alone keeping it safe and happy. Try the run time with just the two external batteries.

also keep in mind new batteries take a little while to get to a constant charge capacity (~10 charge cycles?)

[Shdwdrgn]

Good info, I'll have to keep all that in mind as I continue testing.  The recharge cycle probably affects the current being pushed to the batteries as well, so there may be specific times in the cycle when damage to the circuitry is more likely to occur.

Got an update on the charge times.
1) Stock Z, further recharging has shown a full charge after only 1 hour, rather than the 1:45 I reported initially.  This is more consistant with what I expected, so I am guess the first recharge time was simply a fluke.  Timing on wifi scanning all channels is around 30 minutes (compared to the 3 hours I get with the external battery installed).  Apparently even though the internal and external batteries are both 3.7V lithium, the external packs are much more efficiant.
2) Charging with the internal battery + 1 external pack is remaining constant right around 2 hours.  Usage with the wifi in scan mode and full backlight remains constant at about 3 hours.
3) Charging with internal battery + 2 external packs -- have only done this once so far.  Total recharge time was over 3 hours, however one of the packs was not fully discharged.  I'm estimating a full recharge time at somewhere around 4 hours.  After charging, all 3 batteries measured 4.10V, so it appears they are charging equally.

I am currently running one last discharge test with single internal battery + wifi + backlight to confirm the 30 minute usage time.  

Tests still remaining:
1) continue testing full recharge time with internal battery + 2 external packs.
2) wifi + 2 battery packs + backlight.  I'm estimating that to be over 5 hours.
3) wifi + 2 battery packs, backlight set to one notch below full brightness, and allowed dimming and turning off (this is how I typically configure).  Without the backlight running constantly, I'm hoping to get a couple more hours out of the batteries (possibly approaching 8 hours?)
4) wifi + 2 battery packs, allow backlight dimming, and enable LCD shutoff.  This should provide by far the highest battery life, and should be similar to a setup used for a wearable, where of course you want the computer turned on all the time, but the display is optional.  I can't even guess at how long the batteries will last in this configuration, but knowing that the LCD pulls a tremendous amount of current, I'm hoping to get over 12 hours of uptime.
5) check how much current is being pulled from the AC adapter while charging all 3 batteries.

If anyone has other suggestions for useful tests, let me know, I'll work them in somewhere.

[waalkman]

If anyone has other suggestions for useful tests, let me know, I'll work them in somewhere.

Check out:

http://dataweek.co.za/news.asp?pklNewsID=9...klCategoryID=46


Enjoy

[Shdwdrgn]

Great article!  If I had to guess, I would say the Z's battery is a graphite type, simply because I've noticed during the discharge that the battery % has a reall slow discharge, then suddenly drops like a rock.  Also as I mentioned above, after a full recharge, all of the battery packs are sitting at a solid 4.10V.  I think overall I'm pretty well set up, because each of these external packs has it's own monitoring circuit built in, so no one battery should cause a catastrophic failure of the others.

FYI I completed a couple more tests today
1) Stock Z + wifi + backlight -- the first test only lasted 30 minutes.  The last test ran for 65 minutes.  Quite a discrepancy between tests, however even in the longest run, the addition of the external battery pack gave me 3 times the usage.
2) 2 battery packs + wifi + backlight -- Ran for a whopping 5 hours, 35 minutes!  I ran into a small problem during this testing however.  Apparently wellenreiter has a serious memory leak, because after 3 hours it crashed due to memory being full, and I had to reboot the Z to recover the wifi card.

Batteries have been recharging for about 4 hours now.  Should be almost done, but will have to wait and see.

[waalkman]

I think overall I'm pretty well set up, because each of these external packs has it's own monitoring circuit built in, so no one battery should cause a catastrophic failure of the others.

Ummm, I don't think so, there's a chip to measure the tempature, and your charging circuitry is supposed to monitor that to limit the charging of the battery. There is a fuse internal to the battery, but you don't want to have to use that


Apparently wellenreiter has a serious memory leak, because after 3 hours it crashed due to memory being full, and I had to reboot the Z to recover the wifi card.

Now that's funny!

wellenreiter developer #1 "We seem to have a memory leak in the program."

wellenreiter developer #2 "Yeah, but the Zaurus battery will die before things lock up"

wellenreiter developer #1 "Oh, right. Nevermind..."

Now I understand how these things work

Batteries have been recharging for about 4 hours now.  Should be almost done, but will have to wait and see.

Sounds like you have been doing some good testing. Just be careful, Li-ons aren't known to be forgiving.

[Shdwdrgn]

Well I've been using the extra battery packs for about a week now, with no hardware failures.  During the days with typical usage (pulling up address book, playing a few games, running zRoadmap and wellenreiter while driving to/from work), I've not run the batteries dry yet.  Under the heaviest usage (running wireless much of the day, and having OZ turn off the LCD rather than turning off the computer) I got the batteries down to about 30% one day.

After next weekend (Halloween) I am going to start trying to vacuum-form a custom backplate to protect the batteries.  Things I would like to incorporate include:
- Full backplate to contain the batteries
- Opening for toggling the battery switch and pressing the full reset switch
- Extra space above the batteries in which to experiment with a second CF socket
- Integrated serial connector so I can include a more standard serial connector and USB port
- Clear faceplate which can flip over to the backside without being removed.

Ideally I would like to make a backplate which completely replaces the original and allows me to build in a permanent GPS on a second CF socket.  The only problem I see with this is the internal circuit board interfering with the reception of the GPS.   Lots more fun to be had...