Slightly OT External Battery Pack

[ChefJohn]

Has anyone successfully built an external battery pack for their 600 series?

Any tips tricks and traps?

What type of battery did you use? (Disposable, Nicad, NiMh etc.)

Why?

WHere did you get the raw materials?

Thanks

[joester]

The trouble with rebuilding 600 series batteries is that they must be cut apart. They are glued in a way that is not possible to undo.

Replacing the cells is relatively easy, BUT...
There are some safety issues you must be aware of and protect against. The lithuim ion cells can and will burst into an uncontrollable flame until they burn out themselves. By the nature of their construction, they have a flammable liquid inside. This liquid is what burns. Depending on where you get your info on them, it is suggested that the liquid reacts violently to air. This means puncturing a cell would cause it to flame up. Quite dangerous cutting the pack open then, isn't it? Also consider that accidentally shorting the cell will cause it to heat up and burst.

A quick Google on lithium ion batteries will turn up several sources, but most will not sell to an end user like yourself.
I've rebuilt a couple batteries, and had no issues. The 600 series battery I rebuilt unfortunately has an electronic issue and did not work as well as my T21 battery.

FWIW, you will be looking for 18650 cells should you decide to attempt repacking the battery yourself.

Joe

[ChefJohn]

I was thinking of an external "brick" that I could plug my notebook into...

[joester]

My apologies for the misunderstanding...

In fact, yes I have built an external power supply in "brick" form as you've mentioned. It is a simple basic cell pack consisting of 4 12V 2 AH batteries and a regulator circuit to drop the voltage to 16V.
My mistake was making it a 3 amp regulator. I am rebuilding it to handle 5 amps. The LM338 I used gets too warm for my liking.
Basically, it weighs more than the laptop, but it provides a full day of power. It charges on 24V. and is built in a cardboard box (prototype material...).

The new and improved model will only have two cells I think, and a more presentable box.

I'll take a few pictures if you want.
Joe

[jamiphar]

My apologies for the misunderstanding...

In fact, yes I have built an external power supply in "brick" form as you've mentioned. It is a simple basic cell pack consisting of 4 12V 2 AH batteries and a regulator circuit to drop the voltage to 16V.
My mistake was making it a 3 amp regulator. I am rebuilding it to handle 5 amps. The LM338 I used gets too warm for my liking.
Basically, it weighs more than the laptop, but it provides a full day of power. It charges on 24V. and is built in a cardboard box (prototype material...).

The new and improved model will only have two cells I think, and a more presentable box.

I'll take a few pictures if you want.
Joe

I'd be interested in seeing some photos. Maybe version 2.0 could use something like this as the casing.

Would you be able to give some details about the circuitry, too? It sounds like this has some possibilities.

[ChefJohn]

Apart from a weight thing what are the negatives to using an external battery using "D" cells as the power source.

I think that you would rule out any problems of specialised re chargers - combustion problems And I think D cells are prety much available anywhere ..... (could even go rechargeable I guess)

For a more readily available what about AA's? (I read somewhere that they are more developed in so far as power vs size.

I would appreviate any comments...

I do remember a Toshiba Notebook with two 720 floppies that had a string of D cell Nicads as its "battery" .

Thanks

[rodgermcliff]

One problem with akaline batteries is the voltage profile as they discharge. Li-Ion batteries only slightly drop voltage as they discharge and then have a steep ramp right as they finish up. Akalines have a much steeper slope and not much final drop; in the other words, the voltage drops a lot as it discharges. You may have to build in a voltage regulator to keep the voltage stable enough to run your laptop [not to mention that you will have to more batteries to start with to last long enough to be worthwhile].

Rodger

Apart from a weight thing what are the negatives to using an external battery using "D" cells as the power source.

I think that you would rule out any problems of specialised re chargers - combustion problems And I think D cells are prety much available anywhere ..... (could even go rechargeable I guess)

For a more readily available what about AA's? (I read somewhere that they are more developed in so far as power vs size.

I would appreviate any comments...

I do remember a Toshiba Notebook with two 720 floppies that had a string of D cell Nicads as its "battery" .

Thanks

[joester]

At long last, I have pics. Long story, but I have them.
I got side tracked with a new toy... I was at the local electronics shop, and saw a camera on the discount table with a $10 tag. I asked them if they would take $5 for it, and lo and behold, I ended up buying it for $5. Not bad for a Vivitar 8300S. No cables, adapter, book, box, ect... Just the camera and battery. Been playing with it and learning to use it. Best $5 I have spent yet.
Anyway,
A photo of the outside. The red switch guard is from a 2 liter soft drink bottle. Works great. I wanted to be able to turn off the battery for charging purposes. The heatsink on top is held in place with double sticky tape. As mentioned before, it's only 3 AMP and needs to be 5.
Then a photoof the inside. The tiny board in the center is the resistors and caps for the regulator. Schematic is the suggested use for an LM338 regulator (typical circuit) from the datasheet.

V2.0 is in the works, and may only be 2 cells. I'm still gathering parts, so who knows?

As stated before, this will provide more hours of computing than I care to sit in front of a computer.

The advantage to this design is that I am working from a 24V supply regulated down to 16V. The mains need to run down to 16V before I notice a decrease in performance. That's a LONG time.

Also, a correction: These are 12V 2.5AH batteries.

Joe

[Rick Aguinaldo]

A neater and more efficient method is to use the commercial auto adapters. Here is a sample of one. Just clip off the cigarette lighter connector and replace with the slip-on battery termninal connectors. For added protection, an inline fuse between the adapter and the 12V batterry pack can be used. The LM series linear regulators are less efficient than the commercial switching regulators in this application. For a load of 3A from a 24V supply, the LM regulator must dissipate (wasted as heat) 24W of power to drop the voltage to 16V. Another alternate solution is to use the commercial 12V DC-to-AC inverters. The advantage of the latter is you can plug other small power electronic gadgets while outdoor.

[ChefJohn]

You must have been reading my mind.
I did some research and came to the same conclusion.
I did find a unit for a little less - it had a multiple voltage/power tip option.

My next phase is to look at the actual battery (also possible recharger).

Bearing in mind Budgetary constraints and possible acceptance by airlines, homeland security or ... what recomendations?
I don't want to haul a 12v car battery around - too much reserve power and heavy!!!
I also don't want to be tied into something esoteric (and probably expensive).
Are sealed lead acid batteries allowed? What about charging them?
Thanks for all input so far.

[joester]

I cannot argue with the fact that using a 12V-120 VAC inverter would provide an immense ability for other uses. Keep in mind that this came from stuff I had onhand one Saturday night. I have a 400Watt inverter I originally bought for use in my motorhome, and with a recently acquired 1500w model, the 400 is available for use elsewhere now. My plan was to make another cell using two 12V 32AH batteries and the inverter. Weight will be an issue, but I have a fold up luggage rack that will probably be dedicated for it.

V2.0 of the alternate battery will have a much cleaner look, and probably the same circuitry but bumped up to 5 amps. My goal is to have a pack small enough to include in the laptop bag. I also want to add a switch that will reconfigure the wiring to allow plugging it into the car to charge it. I could easily add a socket to allow an auto adapter to be used while charging.

I want my end product to allow extended laptop use without being plugged in to AC or being restricted to being near the car.

Joe

[Kyosho]

Out of curiosity, has anyone tried anything lower or higher than 16v on the charger/wall jack? I might build a pack that is 18v but I'd hate to have to deal with a DC-DC converter to bring it down to 16. I know the battery pack is only 10.8v. I'm guessing the main jack would probably run on 12v, but I can't be certain of that. Usually most electronics can run with higher voltage, so the 18 might be okay. Then again, what if the lower IS 12v and 16 is actually the highest safe voltage? Hmm.

Speaking of the battery pack, does anyone know if the connector on the motherboard will accept the positive and negative of the battery without the protection circuit connected? If so I might build myself a custom nimh battery pack inside the casing of one of the li-ion ones. I don't care whether the laptop can charge the battery or not, just that if it can run off it. I could charge it separately.

I've got experience with these sorts of things in building portable game systems (think Ben Heckendorn-like but with less financial resources), and I'd like to apply that knowledge here. I just don't want to risk frying my motherboard if some one else already has already done these experiments. Learning from the mistakes of others is key.

[nitro2k01]

I haven't tried powering a 600E with 18 V, however the service manual states that the voltage should be in the range 15.5 V - 17 V.
I have however tried powering another computer with a too high voltage. (A HP laptop from the same time, also with an MMC-2 CPU module) The computer wanted 19 V, but I powered it with 22 V.
The computer itself worked fine, but the battery wouldn't charge at this voltage. (Probably because of the battery's over-voltage protection) When connecting a proper voltage, all was well again.
I judge the risk of hurting anything by powering with 18 V as pretty low. Just make sure that the DC you get is clean. (Free of spikes and noise etc) This goes for anything homebuilt of course. And make sure you don't get the polarity wrong! That's an instant killer!

[nitro2k01]

Oh, I missed this part!

Speaking of the battery pack, does anyone know if the connector on the motherboard will accept the positive and negative of the battery without the protection circuit connected? If so I might build myself a custom nimh battery pack inside the casing of one of the li-ion ones. I don't care whether the laptop can charge the battery or not, just that if it can run off it. I could charge it separately.

It can do that. Here it is in action:
http://www.flickr.com/photos/gameboygenius/524134604

http://farm1.static.flickr.com/228/5241 ... d822ee.jpg

However, a word of caution here: The TP is very fuzzy about voltage changes on the battery poles. A really small spike or drop, could make it die. (Turn itself off)
If you have battery that works, but barely, you're probably better off building something that powers the laptop through the external power port and using the internal one as a backup battery, even if it lasts only a minute or so.

MOD EDIT: Picture without warning, overlimit, changed to link.

[hjanzen]

Talking about batteries:
Has anyone ever succesfully replaced the Li ion cells of a battery pack by standard AA Ni-MH type cells?
These cells come nowadays with ~3000 mAH. and are very cheap.

Sometime ago I replaced the NiCD cells of a 701C battery pack by AA cells which was a succes, maybe only because of the absence of any electronics in the pack.

Now I have opened the battery of my 770X, that has Li Ion cells AND electronics and I was wondering..

[nitro2k01]

The electronics in the cell are there to protect the Li Ion cells, and charge them properly. I don't think the elctronics would work very well, if at all with NiMH cells. For example, Li Ion cells must no be over- or undercharged. If they are overcharged, they will explode or at least start leaking. If they are undercharged, nothing will happen until they are recharged, in which case they will also explode or leak. So the electornics are in charge of isabling the battery before the voltage drops too low.
Also, it's no co-incidence nearly every laptop battery today is using Li Ion cells. These cells can handle a high amperage, and can also handle the uneven load from the power swtich in the computer well.
Replacing the Li Ion cells with NiMH ones would be bad for that reason alone.
However there are replacement Li Ion cells that you can use, but I don't have the link handy any more. But google and you may find it.

[hjanzen]

Thank you very much for your extensive information.
I believe you are right.
New Li Ion cells however are rather expensive and I have no means to load them other than in the laptop. So I want to be sure that it is possible before I spend money on them since I have read somewhere that the battery electronics may prevent even new cells to be loaded.
I did a trial with 9 good Li Ion cells out of a demolished toshiba laptop, that I connected by outside wiring in parallel ( 3 by 3 in order to get 10,8 volt) to the existing dead cells of my battery pack but the 770X refused to load them. (The toshiba cells are just too long to fit in the 770X pack)
Regards, Hans

[joester]

I have read somewhere that the battery electronics may prevent even new cells to be loaded.

I've done some expermenting by mixing various age/voltage capable cells. It appears that the cells used (all of them) must be of similar charge/discharge rates. This rate is dependent on the cell itself. I have replaced a single cell in a battery pack that tested as being bad with a newer one, but the battery would not charge from the laptop. I re-replaced the cell with one of similar charge/discharge rates, and found the battery was happy to charge off the laptop.
I believe the electronics in the battery compare the cells to each other, and will isloate the battery from the charging circuit if too much difference is detected.

Joe

[hjanzen]

That is very interesting Joester.
That means that one should first charge all the individual cells to an equal load before mounting them in a battery pack.
Unfortunately I have no means of loading Li Ion cells...and moreover the Toshiba cells that I had have meanwhile landed in the waste bucket.
That made me think of using standard AA NiMH ones but I am afraid that is not a good idea either..