Difficult battery charger task

Guest
Dear All,
I have been given a task to design a battery charger for SAFT
batteries in series.
There are 170 batteries in series.
The charge current is 12Amps.(6A above a level)
The discharge current is 120 Amps.
I have never dealt with high currents before. The charge voltage is 170
*2.1 = 357 volts. I consider to use LM350's in parallel to limit the
charge current but will they withstand such a high voltage?
Any suggestions for the circuit?
And how am I going to limit the discharge current to 120A?
Any Ideas?
Thanks
 
Here's some more fodder for the pros' hilarity... I can see why they
emit Bronx cheers in this case. But what the hell:

view in proportional font

And how am I going to limit the discharge current to 120A?
Click to expand...

load about .005 ohms 100 watts
_____/\/\/\________ _____________/\/\/\_____________
| _|___|_ _|_ | |
| _ / \ | |
| |_______/ V____________| |
| | |
| / |
| \ |
| / |
|_____________________\ |
| ground
__|__
_
_____
_
_____
_
|
|
ground

You will need a farm of parallel mosfets or a honkin igbt.
 
John Fields wrote:
---
Either let us design it for you or post an address where we can send
the flowers.

--
John Fields
Professional Circuit Designer
Click to expand...
LOL!

I was eating spaghetti thinking, "Oh God, please let him not fire up
that circuit without a friend around..."

Luckily, I had large paper towel handy. :))

-Chaud Lapin-
 
OK Boyz,
You have fun, at least tell me how to do this safely. How will I limit
the current without being electrocuted.
 
You're right. We decided to use a High Voltage Battery Charger from
PowerDesigners (PowerCharge HV Series). For the Discharge, the
Batteries have to be discharged before Charging. I still don't know how
to limit the discharge current at 120A.
 
Ian Stirling wrote:
To do it safely.
Remain 5m or more away from the apparatus under power, or with the batteries
charged at all times.
Cover the battery with a cover adequate to catch any shrapnel.
If you need to look at things closer, use a video camera/webcam.

Run the leads of the batteries (divided into 30V or so groups) outside
the cover.

Connect several adequately rated knife switches mechanically together,
and use these to isolate the batteries, so they are at a safe potential.
Make sure you can visually see that all the knife switches are disconnected
before approaching.
NEVER go anywhere near the battery pack with any metal buttons/tools/
eyeglasses/rings.
Wire the groups of cells up seperately, and case them seperately.
Click to expand...
The OP can't do the project as he described it safely. He just doesn't
know what he's doing.

But since he's going to try it anyway, Mr Stirling gave some very good
advice. The OP should carefully follow all the precautions and good
advice in Mr. Stirling's list.

If I could, I would add at least a pair of real polycarbonate safety
goggles which are ANSI Z87.1 compliant, and a pair of rubber insulating
gloves. He should go to an electrical supply house for these rather
than buy the cheapie imports from the "do-it-yourself-poorly" mega
hardware store down the street. For the most part, the megastores sell
wannabe toys, manufacturing culls and QC rejects for safety equipment.

A good pair of goggles and insulating gloves will reduce the chance of
eye damage or electrical burns, but only if they're used.

Chris
 
booth wrote:
You're right. We decided to use a High Voltage Battery Charger from
PowerDesigners (PowerCharge HV Series). For the Discharge, the
Batteries have to be discharged before Charging. I still don't know how
to limit the discharge current at 120A.
Click to expand...
Much better. All you need now is a 3 ohm, 43,200 watt resistor bank.
That's not as difficult or as expensive as it might seem (although it
will cost quite a bit)..

Try calling Surplus Sales of Nebraska. They've got tons of wirewound
power resistors, and will help you design the least expensive load bank
for your application. Remember to use the correct mounting hardware,
manufacture a frame with sufficient air space between resistors to
avoid hotboxing, and remember generous use of forced air (the 20" box
fans they sell for $15.00 USD each at the hardware store are really
good for this).

http://www.surplussales.com/index.html
Surplus Sales of Nebraska
1218 Nicholas Street
Omaha, Nebraska 68102-4211
402-346-4750 ˇ 800-244-4567 ˇ 402-346-2939 Fax

Use a remote voltmeter to determine the correct point to disconnect the
load bank, and you're good to go.

Mr. Stirling's advice is still valid for switching and releasing the
load bank. And please remember the rubber gloves and safety goggles.

Good luck
Chris
 
On Thu, 30 Jun 2005 21:22:28 GMT, Apostrophe Police
<sendspamhere@111.111.111.111> wrote:

On Thu, 30 Jun 2005 10:51:19 -0700, Jim Thompson wrote:
On Thu, 30 Jun 2005 17:45:40 GMT, ehsjr <ehsjr@bellatlantic.net
Rich Grise wrote:
On Tue, 28 Jun 2005 11:19:26 +0200, Alan Adrian wrote:
[snip]

No idea as to how to limit your current...

How about, "BMF Resistor"?

In this case, BMF stands for "Blows Mighty Fast", just as
in the BAF fuse, where BAF stands for "Blows Awful Fast".

Sheeesh! Political-correctness has come to circuit design.

BMF stands for "Big Mutha F....er" ;-)

"...ing". It's an adjective. ;-P
Click to expand...
To be precise, a participle. 8^Ţ~

--
Al Brennan

"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla
 
On Wed, 29 Jun 2005 05:47:57 -0400, "Daniel A. Thomas"
<dathomas@istar.ca> wrote:

| A good pair of goggles and insulating gloves will reduce the chance of
| eye damage or electrical burns, but only if they're used.
|

Ditto to the above and would add a buddy system. All parties should have
first aid with CPR. Never work on this kind of device alone.

Don't forget the eye wash station and neutralization solutions for
spills ...
Click to expand...
I'd do the goggles one better and get a face shield as a complement.
I'd wear long sleeves and full trousers, and only wear clothes I
wouldn't mind throwing away when little holes start appearing
everywhere. Before I started, I'd read and memorize this page:

http://ptcl.chem.ox.ac.uk/MSDS/PO/potassium_hydroxide.html

--
Al Brennan

"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla
 
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