Home-made Batteries for Pavilion dv6000

Hi guys!

I have an idea for a really cool battery power supply for my laptop. Here's the deal:

Using two 12V UPS batts to build a cheap regulated power supply for my Pavilion.

My comp. is an HP Pavilion dv6899ei. The AC adapter supplies (is rated as) 19V DC 4.74Amps (Model no. 393954-004)
This i believe is the required voltage to charge the battery. The current is the rate at which it is charged, i.e the higher the current rating the faster the batt is charged.

So if i hook (two relatively cheap) UPS batts. (@approx.$10 each), hook in series (=24V)then regulate the voltage down to 19V, i can get the batt charged, with this batt powered power supply unit. This will be a cheap home-made laptop battery!:wink:

Now, for you gurus here are a few questions:
1. will this work?, if not pls explain as well as you can why it won't.

2. if i connect this psu without the inhouse batts of the laptop, will it damage the motherboard, i.e is the 19V used to charge batts alone.

Thanks.:wink:

HSter2

 

http://www.notebookreview.com/default.asp?newsID=4224

Good luck!

 

Thanks but i'm not refurbishing. I'm building a dc power supply that'll plug-in via the adapter socket. Since the adapter supplies dc, i thought what about building a dc power supply using batts.(dc power source) that essentially does the job of the ac adapter. But using this technique i don't need to charge the batts. since this is like doing double work, i.e using a batt to charge another batt. So my question is will the psu built be good enough as a batt. so that i can run the laptop (not necessarily charge the in house batts) using this.

So any advice from you guys is highly encouraged (especially you EEs)

Thanks

 

The power supply can be made using a variable voltage regualator.

 

anyone out there?

 

If you manage this project with success, share what you learned.
I tried to do this myself ---unsuccessfuly.

 

You get what you pay for.

I tried the same thing to extend the power of a tiny battery powered mobile broadband router, and was very disappointed. Some folks trying to do the same thing reasoned that one of those UPS's that can power a desktop system for 30 minutes could power the same little router for a long long tiime, and it did not work out so well either (they got about 40 minutes due to the ineffeciency of the built in inverter). I have a bunch of UPS batteries, and have ried in vain to find a good use for them (other than backup power). They are not deep cycle, so they are not designed for heavy charge/discharge cycles.

You will have to be very careful not to let the voltage of the UPS batteries drop below about 11.6 volts (23.2 wired together), else your gonna damage them, and end up paying more for batteries than your gonna save. Further, those batteries are not designed for constant deep cycle use, and will not last very long using them that way.

They are also gonna be heavy and bulky. The point of battery power is usually to be mobile, and those lead acid cells are not very mobile (unlike the lithium ion's). They also do not charge very fast either.

You may get a hour or two of aux power, between 10 hour recharge cycles.

If you want some real power, get a pure-sine wave inverter, and a AGM battery (very heavy). Sears has a small inexpensive one they use for wheelchairs. I have one of the small marine AGM's in my car, and two big honkin ones at the house, and can power my laptops, mobile broadband routers, amps, and espresso machine for for days. Here a pic:

http://hecht-haus.net/joe/2964-9797924074100.htm

If you want cheap, get a old marine battery (and a not so cheap pure-sine wave inverter). I have an old die-hard marine battery on on its last breath, and it will power by DT9500T for 24 hours. Don't try using a car battery, as they are designed for starting, and will not last long. You need a deep cycle battery. They are starting to make small AGM batteries. AGM is a good choice (but very heavy).

I'm not trying to diss you on the idea. It's a good one, and there are plenty of "inventor kinda folks" that have tried this sort of thing, (time and time again). Try living on a Sailboat for a bit, and see how many things like this you will end up trying to invent

Let us know how it goes!

Joe

 

Thanks, what did you try pls?

 

First of all Thank you so much for responding with much advice.
The AC-DC adapter/charger converts the alternating current/voltage to direct current/voltage, specifically at 19V 4A in my case. Thus, its input is AC and its output is DC. So my idea is not exactly to invert and supply(to the adapter input), but to directly supply dc power to the power socket of the laptop from the batt psu that i'll build. i.e it substitutes for the dc output of the adapter/charger.

Not a problem

Not a problem, my main concern is to have more power, to have a longer run-time of my computer. Mobility is not an issue for me.

I've built a fully automatic charger for this type of batts that'll rapid charge & trickle charge.

My computer is an HP Pavilion dv6899ei, Special Edition, with Intel core2 duo (T5550) processor. It came with Vista pre-installed, so i created a partition for XP & use it most of the time in XP. However the fan seems to run most of the time (don't really think its a driver problem), so the batt life is short, about 1hr 30mins at best. So i need to extend my computers up-time desperately, but can't risk losing it, as well.

My main question now is how much current does the computer need to operate when powered by the ac-dc adapter with the laptop batt removed (i.e while not charging). So that i don't send excess current into the computer to damage the motherboard.

Thanks once again & Thanks for the link with the photo, cool!

 

It requires about the same as when the battery is there and in a charged state).

Your problem is not too much current, as the notebook will take what it needs, and leave the rest. In other words, you could have a thousand amps available, and it might only use 4. Like a small light bulb hooked up to a car battery, the car battery might have a hundred amps available, and the light bulb may only pull 0.25 amps, and the little light build does not get fried.

Too little current is a problem, as when the notebook starts pulling more amps than what is available, the voltage will drop, and that can be bad.

FWIW, My DV9500's will operate on on 18 volts, but refuse to charge until the voltage gets close to 19 volts. When hooked up to the stupid HP Airplane adapter (18.5 volts), it will suck the juice out of the battery till its dead, and keep right on going as long as its plugged in. I ave had problems ordering replacement power bricks on ebay, as the non-oem units are often a slight bit less than 9 volts, and wont charge the batteries.

You might want to get a "KillAWatt" unit, and try it out. My unit is supposed to need 90 watts (volts x amps as I am sure you already know), but I have never seen it actually use 90 watts (there is a safety margin built in).

Voltage regulation is going to be the big problem. Its gotta be pretty good, and have an emergency shutdown for low voltage.

I have fried a lot of electronics with the voltage regulation problem, most recently, a CTR-350 mobile broadband router just last week. My problem is doing reliable regulation from 11.5 to 15 volts to a constant 12.5, and a constant 5.25 volts. Doing a very good job of it costs some money

Joe

 

As for voltage regulation i have designed one with the LM317 variable volt regulator. Perhaps will use the TIP41/42 as a pass transistor.

What do you think?

 

What about the LM317 variable volt reg and set it to 12.5V or use a LM78xx series with a diode, i.e. 7812 and 7805. These ICs all regulate well when input voltage is greater 2V of the desired output voltage. So there'll be a problem with the 11.5v end with the 12.5v output.