Notebook Battery, wiring up anther brand

[Siddy]

Hi Guys,
I recently bought an old notebook for uni, its a "M722". Dodge kinda thing, P3 850 (think it was upgraded from stock 700mHz) 256 SD 133 4MB RAGE card. Basically, the battery doesnt hold a charge anymore, and its not really possible to buy a replacement to suit a 10yr old cheap notebook. Unfortunately the battery was not jsut out sources to a common company as they usually are, so im looking at buying anther 14.8V battery they is similar dimensions and "making" it fit.
When i built my first speed machine (worked A8N-Sli Deluxe) a few years ago, i found a lot of help here, so i thought id try again.

So what i need to know is how to wire up a different battery.
My battery has 6 pins (actually they are slits, but you know).
I know it needs at least 2 for powering the notebook (+ and -), then 2 for the charger (+, -), so i dont know what the other two are for, also i dont know how to tell which ones are which.

Can anyone give info on how to find out which pins are what? use of a multi-meter and test for impedance is my first guess, but unsure what results will mean.

Thanks for any help!

(i would rather not just buy some other battery and HOPE that the pins line up and i can hook them up in the same series).

 

[Gibson486]

Geesh...i woudn't even dare to do that....i could work....but i don't think it is worth teh hassle if you do not have the time. One of the more important things is to measure the thermistor (it's a Thermistor pin to the ground pin). Since you have 6 pins, i don't even know if it would be possible to tell which is which with out experimenting or actualy having the schematic (however, it may tell you on the battery).

What i would do is go into goolgle and search for it.

http://www.google.com/search?hl=en&clie...=hX5&q=MiNote+M722+battery&btnG=Search

Google is your friend.

 

[herm0016]

you could try to just replace the cells in the battery, normally they are aa or aaa cells just soldered together. i have rebuilt packs for portable ham radios and other rechargeable devices.

 

[Aluvus]

The Google search above suggests that you have a lithium-ion battery, which really indicates you should rethink this.

You're going to need to determine the pinout of the battery you have, and of whatever you intend to replace it with. Impedance measurements aren't going to do it. You might make some progress with a voltmeter, but you would still end up doing some serious guesswork. You don't want to screw this up; Li-Ion batteries do not deal well with being mistreated (ie, they explode).

 

[Siddy]

Ah k, thanks guys.
I was going to do what herm0016 said but i realised its lithium, thats why i asked here. I thought it might have been done before, but looks like its a little to tedious, and not really worth it.

As far as the search goes for a replacement, i live in Australia. To pay USD for a new battery and freight would be more than another laptop.

Watch out for M722 laptop on ebay.au, "as is".

Cheers,
Si.

 

[Cattlegod]

post a pic. is there a circuit board on the battery? if not, then the only possible outputs from the battery are +14.8 and ground, meaning that the other two you don't know the purpose of are +14.8 and ground. Open up the plastic and see where then run to determine if they are positive or ground, or both positive/ground. if you can't open up the plastic (can't figure out why you wouldn't be able to) stick a multimeter up to them, there should be some residual charge left in the battery to determine what is pos/ground.

 

[Mark R]

2 of the pins will be power (+14.8 and 0 V). These will be used for charging and discharging.

The others will be used for charge/discharge control and monitoring. In laptop batteries, it's common for these to connect to a battery monitoring processor built into the battery pack (often only 2 wires). The processor monitors individual cell voltages, the amount of energy going in and out, temperatures, etc. and is used to tell the laptop when to charge and how quickly, and also let the laptop know how full the pack is.

The final 2 wires probably connect to a temperature sensor in the pack, and are used as a failsafe by the laptop to abort charging in case the battery is overheating.

Before you can use a different type of battery, you need to make sure that it has compatible temperature sensors and monitoring processor - otherwise, don't expect the laptop to charge it, or be able to tell how much power is left.

If replacing the battery pack isn't an option - refurbing it may be. Inside the pack, apart from the proprietary monitoring system, is usually a series of standard batteries (usually size 18650 cells) soldered together. Often it's possible for a person competant with electronics to buy some new generic cells and install them in an old battery pack.

 

[pm]

Most laptops nowadays use 18650 lithium ion cells. You can buy these for a reasonable price at http://www.all-battery.com, and http://www.batteryspace.com - among many others.

As others have pointed out, working with lithium ion cells can be dangerous. If they are overcharged, or short-circuited, they tend to readily explode in a rather spectacular fireball. The new cells sold come with a PTC fuse which helps prevent explosions, but I have seen several other people that I know still manage to cause a lithium ion cell to vent even with the PTC present.

While I agree with Mark R's comments, one other thought that occurred to me is that the two other wires could be intermediate wires. 14.8 is a 4 series pack. Lithium ion (cobalt) cells are 3.7V per cell (3.7V x 4 = 14.8V). So it's possible that rather than temperature monitoring, the other two wires are taps off the middle two connections.

It seems to me that you have three reasonable options, and one rather scary one.

You can:
Find someone who sells a compatible battery for your notebook and just buy a pre-built one. I'm sure that on the internet, you will be able find a compatible battery pack for around $100.

Figure out what the DC plug in the back of the notebook puts out as a voltage and current and then create a NiMh pack (or buy one, the two links above sell them) that matches the spec's of that and then drive it off of an external battery pack and not mess with the lithium ion pack. This will be cheaper, and definitely safer, but obviously will be heavier and isn't quite as handy.

Figure out what cells were used in the pack and then replace them with the closest equivalent that you can find by taking apart your existing pack and then swapping out the cells from the links that I listed above. This shouldn't be too expensive, and it's moderately low risk as long as you match the cells fairly well. But it's hard to take those packs apart and there's a risk of incompatibility.

Lastly, you could build a new pack that matches the voltage of the old pack from scratch. Speaking as someone with a lot of experience working with lithium ion batteries (I have an electric bicycle/motorcycle/vehicle with a homebrew 96 cell lithium ion battery pack that I made), I would advise against this route. There are several ways that you could inadvertently cause a lithium ion battery to explode and when they burn, they burn very hot and are very hard to put out. (you need a class D fire extinguisher... and if you think laptop batteries are expensive, run a froogle search on a class D extinguisher).

Personally, I would just pony up the $100 for a new compatible battery, or just run off of AC power.