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About 60V,30A Voltage Regulator/Battery charger?

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colin55

Well-Known Member
Anything over 15 amps is beyond the capability of a novice.
I can put you on to a battery charger manufacturer/designer to confirm this.
The best way to control the output current is to have tappings on the primary.
With an ammter in the ouput, the current is monitored and you simply control the time.
All the other suggestions (SCR, linear regulator etc) are quite absurd.
 
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filbo

New Member
Hello Qaisar Azeemi,
I have just come from looking at your biography. You are certainly not a novice.
May I ask is this a project you have undertaken for your employer or a personal project you will expect to provide you with a product to sell? I only ask this to understand why you wouldn't buy one.
I think making a battery charger using a linear regulator will prove difficult for more than the obvious problems of establishing the 60v you desire. Charging industrial or commercial battery banks provides a number of phases which you need to understand before attempting to build one regardless of the method on which you decide.

SCR technology will certainly provide a robust technology, but will present you with stability, ripple voltage filtering and emi/rfi filtering as well as a heavy (and expensive) set of magnetics and large value (and expensive) capacitors.

Certainly I would be looking to a switching supply, but the design is complex. Do you have resources (fellow engineers who can help you...a college or university where you can get assistance if necessary. How is your mathematics? You'll need to be pretty sharp or have access to matlab or such. Don't buy anything until you have decided on a design. I think your 60v transformer might grow a bit...by any technology, you will drop some voltage on the way through. You need to choose or further investigate what technology you wish to use then do some preliminary calculations before you buy the gear.

Let's hear from you

regards Phil.
 

bountyhunter

Well-Known Member
Hello Qaisar Azeemi,
I have just come from looking at your biography. You are certainly not a novice.
May I ask is this a project you have undertaken for your employer or a personal project you will expect to provide you with a product to sell? I only ask this to understand why you wouldn't buy one..
I was wondering the same thing. Based on the responses, I was assuming it had to be either one of two things:

1) A school assignment/project

2) work assignment from boss

The only feasible topology for this would be an offline (208VAC/3 phase) using an H-bridge configuration. That requires floating gate drive, magnetics must be designed, control loop compensation, protection (overcurrent/over temp) circuits. Hardest part will be the mechanical design and PCB design (which happened to be my specialty). An 1800W converter will be dissipating about 300W internally at full power which requires a well designed heatsink array and fan. The PCB design is always complex to get it to work and not have noise/EMI problems. And the chassis/panels/controls/meters have to be designed.

I used to do these for a living, this would have been a 12 month project.
 
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filbo

New Member
Hello again
I would be interested to hear from Mr Qaisar Azeemi just to know his motivation, work or personal, and what he ultimately chooses as a design. It would be good to follow his progress; so many of these postings end as a blank wall or the person initiating the post is intimidated and drops out...no resolution, no fanks, no nuffin'. Anyway I hope you will appraise us of your progress or otherwise Mr Azeemi.

While you still have to tie it all together, so many of the functions and devices come prepackaged in ICs. All of the big manufacturers have extensive technical documentation and design information and support facilities.

How the batteries will see service; as a standby bank (24x2v cells or 4x12v blocks) on a float charge; as a traction "pack" such as a forklift battery; or just a 4x12v string to quickly recharge 12v blocks. will determine the ultimate charger specifications. Will the battery be flooded cells or "maintenance-free" type. These facts will determine the maximum voltage required (64v for a flooded standby bank) or 56.4 for VR types. If VR cells are used the battery charger must use a temperature compensation circuit.

Depending on the supply voltage (may be 230vac in south asia) a pfc offline converter single phase may be the way to go bountyhunter. If it is a product for sale I would go for smaller modules to be paralleled for greater capacity, but for a one-off application, the bigger unit would cheaper.

best regards
Phil
 
Hello Qaisar Azeemi,
I have just come from looking at your biography. You are certainly not a novice.
May I ask is this a project you have undertaken for your employer or a personal project you will expect to provide you with a product to sell? I only ask this to understand why you wouldn't buy one.
I think making a battery charger using a linear regulator will prove difficult for more than the obvious problems of establishing the 60v you desire. Charging industrial or commercial battery banks provides a number of phases which you need to understand before attempting to build one regardless of the method on which you decide.

I want to get all the knowledge abuot battery chargers and power supplies.

Certainly I would be looking to a switching supply, but the design is complex. Do you have resources (fellow engineers who can help you...a college or university where you can get assistance if necessary. How is your mathematics? You'll need to be pretty sharp or have access to matlab or such.

My Mathematics is not bad and i dont knw MATLAB programming however i did a little work on it in university.

Don't buy anything until you have decided on a design. I think your 60v transformer might grow a bit...by any technology, you will drop some voltage on the way through. You need to choose or further investigate what technology you wish to use then do some preliminary calculations before you buy the gear.

Let's hear from you

regards Phil.

you are right MR filbo and i am very thankful to you that u ask. i am not a novice in the field of electronics. i qualified my Masters in electronics (Fresh Graduate) & just started my professional carrier (Practical work) as an electronics engineer at private company who want to develop their Research and development department and start production of electronics products to sale out. since the R & D department has just developed by the company and i am only haired as an Engineer and researcher till now on test bases so no Electronics Expert is present in the company. boss is looking at me that either i can carry the Projects or not; so their progress is based on my success. MR bountyhunter is right that it is a project given by boss.
Till now i have developed a 24V battery charger using LM338k to charge 2, 12V,7AH sealed lead acid batteries in series. this charger was a simple float charger i think; because i just used the regulator to charge the batteries with 1.2A of current that droped down to 720mA and also used a cut off circuit to cutt the charger off when the voltage rises to 26.8V and keep the battries protected from being damaged.
now i am given a task to charge high capacity battries up to 300AH. so i must need at least 30A current to charge it in 10hrs. for commonly available 200AH battries the charging current can be adjusted by the user from 20A to 30A for fast charging of the batteries. this 20to 30A current may heat up the circuit severely so i am also thinking to search on Switch mode type circuits to develop small, less heat producing and high current handling design. since now i have a small idea of switch mode and i will work on it soon.
The available resources that i have now are LM338k regulators.
 

bountyhunter

Well-Known Member
The "SCR" type designs phased out in the mid 80's. Our direct competitor in the power converter business was Electronic Measurements Inc (EMI) and they had an extensive line of SCR type converters. The problem is that since they are using 60/120 Hz, the transformers and filter inductors are the size and weight of boat anchors.

When we (Power Ten) brought out the slimmer, lighter off line switchers EMI had to follow.... and they did.

Off line switchers are definitely the way to go in the 2 kW power region. A standard H bridge could do it pretty easily.
 

bountyhunter

Well-Known Member
now i am given a task to charge high capacity battries up to 300AH. so i must need at least 30A current to charge it in 10hrs. for commonly available 200AH battries the charging current can be adjusted by the user from 20A to 30A for fast charging of the batteries. this 20to 30A current may heat up the circuit severely so i am also thinking to search on Switch mode type circuits to develop small, less heat producing and high current handling design. since now i have a small idea of switch mode and i will work on it soon.
When I was starting out as an engineer..... about 35 years ago.... one of the first lessons they taught me was the biggest mistake is to try to re-invent the wheel. If you need a battery charger as described, the smart (and cost effective) approach is to go to the companies that have the expertise and get them to develop it to your spec. It ends up being faster and cheaper than trying to develop a technology internally.
 

filbo

New Member
Hello Qaisar and bounty
So as I understand it, your boss is testing your ability to handle power electronic design...is he expecting a saleable product at the end or is he wishing batteries in the factory to be charged?
If you are going to charge 48v 300A batteries, are they flooded cells (you can see the electrolyte level and need to top it up from time to time)? If they are, the size of the charger will be 64 x 30 / (.9 x .99) for a PFC switching supply. That gives approximately 2.2 kw. with about 220 watts of that as losses. My personal choice would be for several modules of 700w connected in parallel. So with a pfc (power factor corrected) design you get a pf of about 0.99 (99%) and an efficiency of something better that 90%.
What sort of timeframe do you have to complete the design?

regards Phil
 
When I was starting out as an engineer..... about 35 years ago.... one of the first lessons they taught me was the biggest mistake is to try to re-invent the wheel. If you need a battery charger as described, the smart (and cost effective) approach is to go to the companies that have the expertise and get them to develop it to your spec. It ends up being faster and cheaper than trying to develop a technology internally.


i can not tell this to my company.... therefore i have to develop some thing.
 

bountyhunter

Well-Known Member
i can not tell this to my company.... therefore i have to develop some thing.
I actually meant it as a useful suggestion: in the 35 years I worked, there were times when I had to tell my boss that what he was asking for was not feasible...... or not possible at all..... or ill advised, which is to say theoretically possible but ridiculous when common sense was applied to the reasoning process.

Those are never easy things to tell a "superior"..... but sometimes necessary.

The idiot I worked for right before my "retirement" was a complete idiot. He would go to meetings and somebody would tell him to do something, and he would quietly accept rather than admit he did not understand what was involved in the task. then he would tell us (or me) that we have to do it..... regardless of whether it was possible or not.

One of the tasks an engineer is forced to do is called "sanity check".
 
he didn't told me any time limit. i want to do it as soon as possible. in a month or better if i do it in 15 days.
 
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filbo

New Member
I am off to play Santa Claus right now so will catch up with you all on Monday

Happy Holiday
regards Phil
 

bountyhunter

Well-Known Member
he didn't told me any time limit. i want to do it as soon as possible. in a month or better if i do it in 15 days.
Still would like to understand:

Do you need this battery charger because they plan to develop it and sell it as a product?

Or do they just need it to charge some batteries in systems used there?
 

tvtech

Well-Known Member
Most Helpful Member
Impossible time line....

I was in the South African Defence Force (SADF) way back in the Eighties. I was a Signalman....
One of our duties was to charge Lead Acid batteries.The chargers we used were all three phase and heavy beasts. Huge transformers and so on.

If I remember correctly, we could charge up to 60V per rail with up to 4 rails per charger....

Lets see: 4 tank batteries in series per rail @ a total of 48V and around 20 Amps initial charging current.
That's around 80 Amps for all 4 rails charging at the same time.

The huge transformers buzzed and took strain. But never once burnt. All was to Military spec.

You have to know what you are doing to design stuff that can reliably handle both the current and voltage at this level.

That was my experience in the early Eighties.

Cheers,
TV Tech
 
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unclejed613

Well-Known Member
Most Helpful Member
modify colin's circuit for a 60V battery as shown below. the charging voltage of a 60V battery is 66-69V. the circuit will pull the relay in when the battery voltage goes above 67V. it needs a separate 12V supply for the relay. if you're actually charging at 30A, then the relay needs to be a 60A rated contactor, the snubber diode will be a 1N4004 instead of a 1N914, and the transistor will be a 2N3055.
 

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filbo

New Member
Hello Mr Qaisar Azeemi
It seems that you have sufficient options from which to choose.
You can use the Colin55/unclejed613 ("simplest") design for which you need to determine a current limit circuit, ripple filtering (high levels of ripple current kill Lead Acid batteries), transformer design (will input transformer provide current lmiting?...gonna be big 'n' heavy) What is the battery application? Will temperature compensation be required? How would you provide that?

SCR-based design usually has large line frequency input transformer . Very noisy (electrical (sometimes physically noisy)), produces high levels of harmonic currents and RFI/EMI. These must be addressed as well as output filtering; similar issues to the above. Current limit and voltage regulation and temperature compensation can be built into control circuitry. Generally design is complex result is big, heavy and expensive. What is the application of the batteries? Moderate efficiency.

Switching regulator can provide all of the bells and whistles but is complex in design and operation. It is however the only way to get high efficiency in these ac to dc converters. The outcome is a relatively small unit, which is suitable for paralleling, so smaller, cheaper modules can be added to give higher power/current outputs.

I would add only that it is essential to begin a design journal ((diary(if you don't already do so)). Describe the design problem firstly...what are you looking to produce:
48v30A battery charger for 48v300Ah battery banks...what type of LA batteries flooded, VRLA, GEL?
...are they a stationary, standby installation...are you float charging them?
...is there a standing load connected to them?
...if not a stationary installation, are they traction (forklift, golf cart) batteries?
...do special standards apply to the installation...telecommunications...power supply authority?
READ ALL YOU CAN ABOUT LEAD ACID BATTERIES AND THEIR CHARGING REQUIREMENTS...YOU CHARGER HAS TO ACHIEVE THESE REQUIREMENTS.

So far your design journal should have a description of your design brief; absolutely all you know about LA batteries and their charging regimes.

You should go on at this stage to begin evaluating the 'design difficulties' for you. Get help for these or read up on them. Continually update your design in schematics and notes so you always have something to show your boss. In the early stages develop parallel designs. Always make notes on why you decided one way or another, and progressively develop a costing schedule on designs to ultimately justify your design decisions.

You are considering charging 48v300Ah battery banks here. They are expensive and must be kept fully charged and maintained in good condition; they are not batteries for toys or torches.

Your task is an involved one and would usually have a number of people involved. But by your postings you are alone in this. I couldn't estimate how long this will take you; it depends on so many things. If you keep a journal to instantly support your decisions, assumptions, costings, your boss will be able to see your efforts and progress.

As regards a timeline, I don't think you can do so for the whole project, but you should attempt to define how far you will have progressed in the first week/month, then continually update and expand that as you progress.
 

Boncuk

New Member
modify colin's circuit for a 60V battery as shown below. the charging voltage of a 60V battery is 66-69V. the circuit will pull the relay in when the battery voltage goes above 67V. it needs a separate 12V supply for the relay. if you're actually charging at 30A, then the relay needs to be a 60A rated contactor, the snubber diode will be a 1N4004 instead of a 1N914, and the transistor will be a 2N3055.

Do you suggest to charge the battery or boil it?

A 48V battery is fully charged at 52.8V! Everything above that voltage will cause the battery to gas freely. After that "BOOM".

Boncuk
 
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