ładowarka_aku_ołowiowe-od Roberta.pdf

Sealed Lead Acid

Battery Charger

Mk II

Revision : 1.3

21 st November 2000

Sealed Lead Acid Battery Charger MkII Manual. Rev 1.3

Page 1

Disclaimer

This battery charger may cause serious harm, even if used correctly. It could over charge your batteries and cause a

fire, burning your house to ashes and making your wife/girlfriend/mum or husband/boyfriend/dad pretty pissed off. In

fact, I don't recommend using it myself. I suggest you spend $300 on a commercial one, then take them to court when

it stuffs up. This project is offered in good faith for non commercial purposes only. If you build this project, you agree

that it is entirely your responsibility if something does go wrong and no damages in any way are the responsibility of

VK3EM. If after all this you still want to sue me, don't bother...I don't have any assets (I spend all my time designing

battery chargers you see...)

This project is offered under the Open Hardware scheme. All relevant design and manufacturing details are included.

You may not, in any way, shape or form use the information in this project for commercial purposes.

Revision History

Rev 1.0 - New development of MkII battery charger. New documentation and schematics. First build of Rev C PCB.

Rev 1.1 - Added document sections on construction and testing.

Rev 1.2 - Modified circuit for "LED Current Monitor". Added documentation on heat sink calculation.

Rev 1.3 - Modified circuit to fix reset problem. Updated schematic and BOM. Added wiring diagram. Fixed some

documentation errors. Change schematic revision to match documentation revision. Added documentation to locate

track to cut for reset circuit modification.

Thanks go to :

As with most projects, they don't happen without help. I have been very fortunate and received a lot of help from the

following people. They deserve a very very big thank you.

John Wright , VK3AJL for countless hours of technical conversation which inspired this project.

Bryan Ackerley, VK3YNG for his help manufacturing the PCB's and supplying UC3906's.

Adrian Hatherley, VK3LK for organising the kit orders, making kits up and soldering of surface mount bits.

Robyn (my girlfriend) for her patience!

This project is dedicated to Harold Hepburn, VK3AFQ who was one of the most proliferic amateur radio home brewers

I have been privelidged to meet. R.I.P.

Sealed Lead Acid Battery Charger MkII Manual. Rev 1.3

Page 2

Contents

Section 1 - Introduction

This section details why you should build and use a Sealed Lead Acid Battery Charger based on the UC3906 IC

from Unitrode.

Section 2 - Design Notes

This section details how the charger was designed, what was considered and why it was done. This section would be

helpful if you intend to modify the charger to suit your own needs (i.e.: change the voltage to 6 volts). This section is

more for my own reference than anything else.

Section 3 - Construction Notes

This section details how to construct the charger with a MkII PCB and the appropriate components. It also contains

hints and tips if you are building your own charger on vero-board or by some other means.

Section 4 - User Manual

This section details how the charger works and what those funny lights mean.

Section 5 - Appendices

This section details : (1) Schematics and wiring diagram, (2) PCB Layout, (3) PCB Overlay, (4) Bill of materials and

(5) Design Calculations.

Please Note : I have spent many hours documenting as much information as possible. If this documentation does not

answer a question or concern, try reading the "Frequently Asked Questions" on the website. If that does not help,

e-mail me at VK3EM@HOTMAIL.COM . All information, intellectual property, circuits and circuit boards documented

been placed in the public domain for the purposes of education.

Sealed Lead Acid Battery Charger MkII Manual. Rev 1.3

Page 3

1.Introduction - Why use a special charger?

A lot of people have their own view on charging batteries. A lot of people get it wrong. What do I mean by wrong? If you

spend big dollars on batteries (or you obtain good batteries for free) you want to get two things : maximum life and

maximum capacity. A significant influence on these two factors is the way the battery is re-charged, especially seal

lead acid cells with gel electrolyte. Get it wrong, and your getting less life and capacity than your battery can offer.

Sealed lead acid batteries are quite expensive, so building a good charger is a worthwhile investment. (Buying one is

the next best option, but good ones are very expensive).

The VK3EM Sealed Lead Acid Battery charger is based around a UC3906 integrated circuit from Unitrode (Now owned

by Texas Instruments) specifically designed for charging SEALED lead acid batteries. It is not a cheap and nasty

battery charger. It is an accurate battery charger designed specifically to get maximum life and capacity from your

batteries. It can also be built for a modest price.

Some key points about recharging sealed lead acid cells can be detailed here :

1.) The chemistry of sealed lead acid cells with a gel electrolyte is different to a standard lead acid cell (as used in

automotive applications)

2.) The use of a controlled "over-charge" is required to force chemical reactions to occur that lead to maximum battery

capacity and life.

3.) The use of temperature tracking is required as the battery voltage varies with temperature.

4.) A slow controlled charge gives maximum battery life

In my opinion, the following are the three biggest factors that cause a dramatic reduction in useful battery life and

capacity (not in order of preference).

1.) The failure to use an over-charge cycle during the charging process (i.e.: under-charging the battery).

2.) The failure to temperature track a float charger

and,

3.) The excessive discharging of a battery.

Where to find further information ?

One of the best sources of information is the "Gates Energy Products" applications manual for sealed rechargeable

batteries. As Murphy's law dictates, it's out of print and not available in PDF form. It should be, because there are many

hours of informative reading to be had with this book.

The next best source is Unitrode Application Note U-104. This application note can be downloaded at the VK3EM

website. It is also available via Texas Instruments (who now own Unitrode).

Please Note : It is impossible to detail exactly how to recharge a sealed lead acid battery. It will vary with different

manufacturers, materials, constructions, electrolytes, discharge cycles, etc. All I wish to point out with this project is

that using a UC3906 based charger is a few orders of magnitude better than a voltage regulator set at 13.8 volts.

Sealed Lead Acid Battery Charger MkII Manual. Rev 1.3

Page 4

2. Design Notes

Introduction : Please make sure you have a copy of Mk II schematics and design calculations in front of you when you

read this section. You will find them in the Appendices. This section of the manual should give you a fair idea of what's

going on inside my head when I designed this charger. As always, I might have done some things differently with

hindsight. I encourage constructive criticism, but remember, there are a lot of trade-offs that one goes through as a

designer. At some point in time, you have to trade off performance, reliability, manufacturability against cost.

Otherwise, who would want to build a $200 charger? (OK NASA would, but who else?) Soapbox dis-engaged....

Power Supply : J1 is the power input to the charger. The AC transformer required should ideally be 18v AC RMS. It can

be higher, but the power dissipated by Q1 (the main pass regulator) will increase. Please be careful with the unloaded

voltage on the Electrolytic capacitors. They can go pop and are 35v rated for a good reason. The input power can also

be DC should you already have a DC plug pack lying around. The best source of power for this charger are plug packs

from old laptops (Almost always 18v AC @ 3Amps).

The rectifier diodes are type 1N5404. They are 3 Amp 400 v PIV type. If you are only building a 250 ma bulk current

charger, you could replace them with common (and cheaper) 1N4004 diodes. If you have a diode bridge of a suitable

rating, you could also use that, but you might not be able to easily fit it onto the PCB. 3 Amp diodes were chosen (even

though the bulk current maximum is 1 Amp) because of input current rush into the electrolytic filter caps at turn on and

they were just as cheap as 1N4004 (From my source of parts anyway). These diodes do get warm at 1 Amp, they

would be egg frying temperature at 3 amps.

The value of the main electrolytic capacitors will vary with the loaded AC voltage of your transformer. In the case of DC

input power supply, they do not need to be fitted, although fitting a small value would be recommended. So long the

DC voltage across the capacitors is never less than 17v at your lowest mains supply voltage, you should be safe. I

make particular mention of this because designers sometimes forget that 240v AC mains does not mean you will have

240v AC RMS at all times. I've seen the voltage at my power points vary from 260v AC RMS to 222v AC RMS. When

designing, also ensure your electronics will cope with the change in transformer secondary voltage due to change in

primary voltage.

U4 provides a regulated 12v output for the operation of the other circuitry. This is required due to the possibility of

many and varied input supply voltages. It became too hard to try and limit the current through the leds with a wildly

varying power supply. Unfortunately, this regulator is a source of heat and thus will contribute to the temperature

sensing error of the UC3906 battery temperature compensation. U4 is located close to the rear edge of the PCB so it

can be mounted on a heatsink or have a small heatsink added. It is recommended that you mount this device on the

heat sink and run some short leads back to the PCB. Be careful though as long leads might cause the regulator to

oscillate.

Charger Control Circuitry :

The exact operation of the UC3906 battery charger is a bit complex to detail here. Not only that, but it's detailed to the

nth degree in the data sheet and application note (See links on the VK3EM web page).

Q1 is the main pass device. It is a TIP32C PNP pass transistor. The data sheet is provided website on the website for

those who want to substitute another transistor. When looking for a substitute, pay careful attention to the maximum Ic

and minimum Beta and Ft. Too low a Beta at the UC3906 will be unable to sink enough base current at 1 Amp

collector current. Too high Ft and you'll end up with a free running RF oscillator. Q1 will need to be mounted on a heat

sink. It is suggested that you use some medium gauge hook-up wire to run from the circuit board to the transistor

mounted on a heat sink. I've seen too many solder joints fail due to constant expansion/contraction of hold/cold

metalwork. See the construction notes (Section 3) for details on calculating the size of the heat sink.

R2 and R3 are the current sense resistors. These are the resistors that set the bulk charge current. As mentioned

before the charger tries to maintain 250mV across these resistors when in the bulk charge state. 1 Ohm will give you a

bulk charge current of 250mA, and 0.25 Ohms will give you a bulk charge current of 1 Amp. Just ensure that the value

chosen is never lower than 0.25 Ohms. Remember "RESISTORS HAVE A TOLERANCE AND YOUR RESISTOR

MIGHT FALL OUTSIDE THIS RANGE". It's best to check it first by making up simple circuit and measuring the voltage

drop across the resistor.

Sealed Lead Acid Battery Charger MkII Manual. Rev 1.3

Page 5

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: