DIY Custom Battery Mod--Anyone know anything about circuits?

Okay so, here is my situation: I have an Asus battery with a 6 cell 4800mAh capacity and a Compal IFL90 battery with a 9 cell 7200mAh capacity. Both run at 11.1v. Yes, you see where this is going (muahaha)--I was wondering...

1. Is it possible to run these together to make a 15-cell battery? I suppose the answer is of course YES, but is it worth the trouble?

2. If so, how would I go about doing that? I have some electrical experience and this just seems like a parallel circuit sort of deal. I don't want to fry anything.

Stuff I know:
-I'll definitely need a multimeter and soldering iron
-The charge levels on the cells must be as close to one another as humanly possible
-Asus batteries are hard to take apart, and probably much harder to put back together (but what else is duct tape for, right?
-My Google-Fu returned this image: http://www.crunchgear.com/wp-content/uploads/2009/02/picture-2.jpg

Any help or input would be appreciated.
Thanks!
--Joe

 

Assuming the charge levels are close then yes, it should be possible.

You shouldn't do it though. These batteries are basicly explosives and your going to be fighting with a bunch of circuits that you don't know the designs of. What are the control circuits for the batteries like? What will this change do to the laptop charger? Will it just charge slowly, or will it fry itself trying to charge with more current then it can handle?

Also, what are you going to do with a laptop that has a 15 cell battery? There is no way you can consiter that portable.

 

does this help?

http://forum.notebookreview.com/showthread.php?t=213793

 

First off: lol @ the last paragraph

Secondly: You bring up some really good points. I'm a little worried that the batteries will either not charge or do something terribly wrong, like explode. In the little research I've done, no one has actually done this. I've never seen exploding cells except in a few pictures from an iPod, mac, and a Dell. And those were all from the manufacturer.

Finally, I have a gaming laptop (an Asus G50vt). It's already a beast to lug around, so no portability losses there by any means. I get around two hours under moderate to light use, which isn't bad considering it's got a 9800m and two hard drives. A 15-Cell would be AWESOME since I already committed to not caring about weight by buying it. Even three hours would be nice...
That said, I don't think the charger will have much trouble. It's a 6.32A charger (120W), and I think under full load this laptop barely hits above 90W according to someone's Kill-A-Watt.

What are the chances of something exploding, you think?

Hmm interesting. Disappointing results but not terrible, considering he did that without a multimeter. Thanks for that one!

 

you could try it.
The charging circuit should dynamically charge the batteries until they are full. Just use only one charging circuit, if you'll use both, then it won't work.
They also seem to use similar cells with the same capacity, still, it's risky if the cells aren't identical.
I wouldn't try it if they use different cells, with a different layout and produced by a different manufacturer.

If the cells are different then it can happen that you overcharge a few of the different cells which then may explode or burn.

It's also possible that the charging will draw too much current and smoke your charging circuit or DC-DC converter on the mainboard. But this shouldn't happen, because it should be protected by a fuse and also by the charging circuit itself which controls the charging current, it should just take much longer to charge the batteries.

So finally, I wouldn't do it. Better buy a few new cells, from which you know they are identical and work and use them instead of mixing two parts together.

 

I've got to commend you, just for the "what else is duct tape for?" comment!

But, seriously, it may be worth it (if you try) to document what you do and post it on here. Never know when someone else may want that info...

 

Yeah, I'll definitely rig it so that it's all charging through the same circuit.

Hmm... Well, you do bring up some other good points. I think the biggest concern would be how electrically similar the two batteries are, and getting them to the same charge level initially. I think my NP2090's mobo might be too dead to charge the battery, so I'll have to run my Asus's battery down to whatever level the 2090's pack is.

I'm a Duct Tape Dude, after all...

Oh definitely. What better place to brag about what you've done than the interwebs (after all your friends get annoyed with how awesome you think you are)?

 

It seems to me that the 18650 cells have different capacities. I highly not recommend you to combine them. Instead, taking apart the battery and reusing the old batteries, why not built your own battery pack. They offer highier performance/capcity and it's more felxible.

Say, if you budget is $100, I recommend these:
-Protected Li-ion 18650 (same ones in your laptop, but highier capacity and protected, so it's safer), order 8 packs of 2 li-ions (16 2500mha 3.7v batteries in total incase 1 is broken ) - $80 with free shipping
http://www.dealextreme.com/details.dx/sku.5790
-some sort of battery holder, solder, solder gun, w/e tool you need

1. Use a multimeter to measure all of these batteries. Make sure all of the batteries have similar resistance.
2. Group them into 5 groups of 3.
3. Solder together the 3 cells in each group in series.
4. Solder together the 5 groups of cells in paralell
5. For a combination of series and parallel circuit for a total of 11.1v 12500mAh laptop battery pack.
6. Hook it up to the laptop's battery circuit, calabriate the battery pack and you're good to go.

 

I appreciate your input, thanks for the walkthrough-- really helpful stuff!

As a college student, I unfortunately don't have much of a workable budget right now. I'm trying to get rid of some spare parts from my 2090, though I suppose I could sell my battery and then buy the protected cells you mentioned...

I've been browsing the stuff on the site and it looks really good-- and cheap! Perhaps I'll get those protected cells--that would certainly take the worry out of anything going boom. And I could make the battery as big as I'd like.

Thanks!

 

If you're on a tight budget, you can get lower capacity cells instead of the high capcity 2500mah ones. Also.. unprotected cells are cheaper as well. There's not much risk in battery exploading as long as the batteries in series have similar resistance which you can check with a multimeter. The battery charging circuit will take care of the rest. Don't forget to calibrate the battery or else the battery life won't increase no mattery how many cells you have.

Anyways.. other battery alternatives are:
http://www.dealextreme.com/details.dx/sku.19770
2500mah 3.7v unprotected - $3.375 per cell
Bulk rate 2 per pack: ntity 3+ units 5+ units 10+ units
Rate $6.05 shipped $5.95 shipped $5.85 shipped

http://www.dealextreme.com/details.dx/sku.21474
3000mah (very high capacity) protected 3.7v - $7.68 per cell
bulk rate 2 per pack: Quantity 3+ units 5+ units 10+ units
Rate $13.66 shipped $13.56 shipped $13.46 shipped

Anyways.. I would recommend selling either one of your battery. Then take your unused battery apart and "rebuild" a new, more powerful battery pack.

To properly calibrate the battery, go to the power properties window and turn off "hibernate when battery achieve certain %". Fully charge the battery for about a 6 - 12 hours (this step is really important). Then unplug the ac and use the computer until it runs out of power 100%. I meant 100% where no matter what you do, the computer won't turn on, won't respond, no lights will be on. Then plug in the AC and recharge to full for about 6 hours again. Repeat these process about 5 times and the DIY battery pack should reach about full capcity. Check the capcity rating through software such as mobile meter to check if the battery capcity is about as high as your calculated capcity.

1 more tip: The more cells and higher the capcity it is, the more efficeint the battery pack will perform.

 

Sounds like an interesting plan. I've looked at a few other battey modders, and it doesn't seem to difficult. I like your sense of safety best, though--multimeter and protected cells and all. I think I'll make this a summer project once college is out and I have access to time, a little more money, and some tools.

Two final questions that I've been running over: do you know if more cells will draw more charging current? Or will the supplied current be constant no matter what? Not that it's too disconcerting-- I know I have at least 20W of A/C adapter overhead to play with.

Also, does the smart battery specification include a standardized connector? I suppose I'm asking if I can simply physically modify the shape of my NP2090's battery so it can hook up to the Asus?

Thanks so much for your input, it's been great thus far.

 

More cells doesn't mean it'll draw more current while charging. The charging current should be decided by the battery charger itself and has a upper limit of how much current it can use to charge the batteries. More cells/highier capacity cells will take longer to charge because the charging circuit is limiting the current output. Anyways.. you won't have to worry about the A/C adapter because it'll be more than enough for the battery mod. If you have 20W of overhead, you'll still have 20W of overhead when you finished the battery mod.

I don't think smart battery have the same standardized connector. Different laptop models from the same company might have the same battery connector though. I guess you can call that "standardized connector".

It's definetly possible to "mod" your NP2090's battery to hook up to the asus laptop. There are many ways to do it. The simplest way is just to crack open the asus battery and then put the NP2090's battery inside hooked up to the asus's charging circuit. After the swap, you'll need to recalibrate the battery to achieve the maximum capacity.

 

I want to share this video.

I'm sure its posted a million times.

http://www.youtube.com/watch?v=BtqRvAu71Gw&feature=channel_page

Hope it helps.

 

LOL... the video comments are filled of people who're afraid to do the mod.

Anyways.. as long as you don't do stupid things like shorting out unprotected cells, you're 99.999999999999999999999999999999999999999999% safe.

 

@Ch28Kid: Oooh yeah that one looks familiar. Thanks for sharing!

@jackluo: Things seem really straightforward. I guess I'll just look forward to overnight charging times with the new pack if it's the same current. I wonder if Everest will pick it up?
Thanks for all your help. I wish I could mod you up a bunch of times for the info.


I think I'm going to wait till I can sell the Compal battery, and then get a bunch of protected cells as suggested sometime this summer (ie: mid-May or so). I'll be sure to keep whatever I do posted on here.

Thanks for everyone's help!
--Joe