Refurbish batteries myself or get external battery pack

hi all,

I'm thinking of getting 18650batts to refurb a notebook batt myself. But I'm thinking of an alternative of getting an external batt pack.

1.Refurb my own batts with 18650 cells (done it before with my 790, so technical, its no sweat! )
CandlePowerForum
Price: $30~$40 depending on the capacity of the cells I use
Pros: Cheapest, no extra stuff to lug around
Cons: max out at 2400mAH ... which is not much for this notebook. should get ~2hrs of usage.

2. 19.2V NiMH Universal External Battery + Charger for Notebook Dell Latitude Inspiron etc
19.2V NiMH Universal External Battery
Price: $45~$55
Pros: Cheap considering the boost in batt life, Possibly 3~4 hrs battery life to notebook
Cons: Extra 3.4lbs!!!! Long charging time 8hrs!!!

3. Extra life 4400mAh (or 4000??) extended batt for M300.
Price: ~$100
Pros: Fits into battery slot, should get 2~3 hrs or maybe even 4hrs of batt life
Cons: Pricey

4. External li-ion battery pack.
Price: $150~$200
Pros: Long battery life of 3~4hrs, can run notebook while charging
Cons: VERY Pricey *ouch*, still have something to lug around

Comments?

If 3. is a NiMH battery, take that one. You probably have better things to do than refurbishing batteries with rather small capacity.

oh, I missed out the details

for 2, its 3000mAh capacity while for 3. its li-ion

what are the advantages of ni-mh??
in my opinion, nothing.... much less density than li-ion.. memory effect...

anyway, i'd recommend the third solution (extended li-ion batt).

Related to this topic, I have a bunch of old batteries for my laptop. They are NiMh batteries, 3600 and 3800 mAh. I was thinking about refurbishing these, but they are Dell Latitude batteries, and the casing on them is a pain to crack. Anybody know how to refurb these? -Is there any url containing the information on how to refurb?

In the end, I got the 130wh li-ion external batt pack. It allows my notebook to run for almost 6 hours ... I never let it run till the end ... but it still had 2led out of 4 after 5.5 hours run.

I'm receiving a dead m300 battery. I think I'll rig it to accept a dc input instead of having 4X18650 batts inside. I think, that might give the batt pack an even longer run instead!

For the ni-mh battery pack for dell, you might want to do a search to see if they are using the standard AA size ni-mh. If they are, its a matter of scoring along the seam of the batt very very patiently like 20~30 times until they crack and open nicely. Be careful of the case near the connector. That's where charging circuts are possibly there.

I'm not entirely sure if standard AAs are used in them. They might be using those that are AA sized but with solder tabs instead. You might find something at www.batteryspace.com

Given the much higher capacity (2300mAh) of ni-mh today, if you succeed to refurb your batts, they should be very long lasting. But note that the charge time would increase as well, since the original charging circuit may be designed for 1/10XC current or something. Meaning a circuit designed for 1500mAh batts would have 150mA charge current. That means a charge time of around 12 hrs, assuming 20% power loss.

New charging algo might super charge with 1A instead and when the batt reach 80%, lower to 1/10XC current. In any case, expect a longer charge time.

I believe when you crack open your batts, you would find the cells in parallel-series config. ie, prob 1800mah or 1900mah batts. If you replace them with 2300mAh batts, we are looking at having 4600mAh batts.

Once you open the case, make sure you take note of the wiring, so that you get back the same voltage configuration.

Let us know!

Li-ion is definitely better, but Ni-Mh is better than Ni-Cd (which indeed has memory effect, while Ni-Mh does not)

Snappy, I am glad about your choice an prolongued authonomy of your gizmo.

Thanks vjurkas! oh yes ... definitely prolongs my autonomy! ... the ext. li-ion batt pack I got has a whole set of dc-jacks that fits practically anything too. So I can try it on my MP790 when I get back on Friday.

Just imagine ... the 790 has a default battery of 7.2v X 1500mAh = 10.8Wh ... if I plug in my 130wh, it would have 11.7 times of usage time than the original batt. If the original batt had 10hrs usage time ... wooo hooo ... my 790 would run for over 100 hours continuously!! wooooooooo

ok ok, someone try stopping me from taking over the world when all power generators stop working!!! ... I would be the only one with power for 4over days!!! mwaaaaahahahahaha hehe

vjurkas,

of course ni-mh is better than ni-cd... but i meant ni-mh vs li-ion..
but, ni-mh still does have some memory effect. of course, again, they're not affected as seriously as ni-cd

My bad. I shoulda explained better: Is there a quick way to test the cells individually?- It could be due to bad boards in these, or just a single bad cell. I believe they are wired in series.

-Is there a way to test the individual cells with a multi meter? - I have about 10 batteries that all are dead. If I can find the bad cells, I can just replace those... Also, my brother races RC cars, and uses 2300 mAh batteries. If I could use some of the good cells out of these, I could still make a more powerful battery...

Again, the big question is: how do I test the cells in the batteries right now? -Or are they all just junk?

If you can get the case opened (nicely), you can unsolder the cells and measure them easily. You are right. In many cases, its one dead cell that is causing the whole batt pack to die ...

But before you start measuring, try to put the batt on charge for awhile, so that the good cells will kinda show a variance from the dead cell ...

let us know how it goes ...