maybe a dumb battery question, but... - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: April 11, 2014, 08:40:17 pm
content: So, I want to hack an old A1185 macbook battery.The battery is made of 6 Li-Po (Lithium Polymer) cells (3.6/3.7V) and I believe they have a capacity of 2400mAh?They are connected in parallel and series to give, if memory serves me, 10.8V / 4800mAh.The question is:Can I replace these cells with Li-Ion cells? Same voltage, maybe higher capacity?What about replace with Ni-Mh cells? Same as above?Yes, No, Why Not?Can something blow up?

author: Holograph
author_rank: Regular Contributor
timestamp: April 11, 2014, 08:45:43 pm
content: If you're only discharging and you keep the voltage the same, sure. But you'll run into trouble with charging the battery. Pretty much all different battery chemistries need to be charged differently. Actually I guess it's possible that Li-Ion and Li-Po are charged the same - I haven't used Li-Po myself for anything so I don't know as much about it - but NiMH needs a different charger (and is a much worse choice for this use). And using the wrong charger (and I don't mean "laptop power supply" but rather the actual battery charging circuit inside the laptop) can sometimes cause things to explode, yes.Li-Ion batteries themselves are prone to explosions if not properly handled.There is also a protection circuit in good batteries that might not work with a different battery chemistry, but it probably won't be an issue on the discharge cycle. Though Li-Ion battery protection circuits do disable the battery if it goes below a certain amount of charge. Probably Li-Po as well.

author: theatrus
author_rank: Frequent Contributor
timestamp: April 11, 2014, 09:14:23 pm
content: For charging, keep the same chemistry (standard Lithium-Ion is different enough to Lithium-Polymers that you won't get an optimal charge). Also, you will be hard pressed to find any cylindrical Li-Ion cell with higher capacity than the LiPo packs.You can probably find some labeled on eBay at ridiculous capacities, but that's all a lie

author: made2hack
author_rank: Frequent Contributor
timestamp: April 11, 2014, 10:18:44 pm
content: I know and Sanyo or Panasonic Li-Ion batteries are not cheap!

author: made2hack
author_rank: Frequent Contributor
timestamp: April 12, 2014, 02:51:59 pm
content: Ok, so i've been reading a bit more about Li-Po and Li-Ion.Apparently, the chemistry isn't that different, since Li-Po is a Lithium-Ion Polymer cell to begin with, just somewhat more updated.The charge circuit for a Li-Po is Constant Current up until 4.2V, after which it switches to Constant Voltage until the charge current drops to about 2% of the initial, and then the battery is said to be charged.This is not that different from the way Lithium Ion circuits are designed.I've also read that since the Li-Po batteries are "protected", I should get a protected Li-Ion cell, any ideas?

author: IanB
author_rank: Super Contributor
timestamp: April 12, 2014, 09:50:53 pm
content: Quote from: trs80 on April 12, 2014, 02:51:59 pmUsually the battery pack as a whole has a single battery monitoring and protection circuit built into it. Most likely you want to leave that in place and just replace the cells with new ones of the same kind. However, if the monitoring circuit happens to be a "smart" digital one, then you may not be able to re-use it (unless you can reset it and re-calibrate it) and will have to replace it with a simple analog type. On the other hand, removing a "smart" battery monitor may prevent the battery working in its original application inside the laptop.The short answer is that battery packs, battery monitors and on-board charging systems are often engineered as complete systems. You can't necessarily swap out one part for another without breaking the system.

author: T0mn0mn0m
author_rank: Newbie
timestamp: April 12, 2014, 10:03:25 pm
content: Are you trying to replace the cells and still charge it with the laptop?I did this on a recent project I posted here, and ran into the problem of the omnipresent LVC on the batteries controller board. I did some research and the vast majority of batteries will lock themselves and never charge again if the voltage drop below a certain point. On some batteries this can be reset (not sure if it's possible with macbook batteries). I got around this by manually balancing the cells, then carefully swapping over power from one pack to the other without the battery PCB ever losing power.

author: made2hack
author_rank: Frequent Contributor
timestamp: April 25, 2014, 10:08:49 am
content: Yeah, I want to replace the cells, but keep the battery pcb intact.

author: BravoV
author_rank: Super Contributor
timestamp: April 25, 2014, 10:22:58 am
content: Quote from: T0mn0mn0m on April 12, 2014, 10:03:25 pmEven with pcb stays on during the cells replacement, modern laptop battery pack is equipped withrotten timersmart gauge and timer, so when it times it decides that you need to buy a new battery pack for it's replacement, refreshing just the bare cells will not work. Unless you know how to hack that smart circuit "inside" the battery pack to defeat that mechanism.

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 26, 2014, 12:38:57 pm
content: Quote from: BravoV on April 25, 2014, 10:22:58 amAn amazing video on the related subject of hacking battery smart gagues;

author: made2hack
author_rank: Frequent Contributor
timestamp: May 15, 2014, 08:35:33 am
content: Yes! Love Defcon videos.Thanks for that!