2-Batteries

I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


At 19:48 25 December 2006, Udo wrote:

Better yet is to use diodes so that both batteries
will always be 'on'
in parallel and you're always pulling from the best
battery with no
fiddling required from the pilot. Relatively low
voltage drop diodes
are available with 18 Amp forward capacity. For redundancy,
I used two
in parallel on each battery.

If it is always drawing from the best battery, what
is the time
interval between switching.
What controls the switching. Please advise.
Udo

Nyal Williams wrote:
I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


Here is a sketch

http://www.mydatabus.com/public/emer...y/e/sketch.JPG

and a pic of my install...

http://www.mydatabus.com/public/emer...y/e/diodes.jpg

There is a aluminum bracket which is lightly mounted to the bulkhead.
The PC board just provides insulation and some support for the wires.

Each diode has a heat sink, but I don't really think it was necessary.

I don't have the part numbers handy, but I'll see if I can't find something.

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.

Thanks Gary for the writeup. I have been thinking of doing the exact
same for a glider I just bought. Can you please add the part number if
you recall them.

I suppose if one really wants to know about the condition of each
individual battery, you could put a voltmeter on a 3-way switch and see
the volatge on the "main" bus, and each of the batteries. This way you
could tell the difference between them.


Gary Emerson wrote:
Nyal Williams wrote:
I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


Here is a sketch

http://www.mydatabus.com/public/emer...y/e/sketch.JPG

and a pic of my install...

http://www.mydatabus.com/public/emer...y/e/diodes.jpg

There is a aluminum bracket which is lightly mounted to the bulkhead.
The PC board just provides insulation and some support for the wires.

Each diode has a heat sink, but I don't really think it was necessary.

I don't have the part numbers handy, but I'll see if I can't find something.

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.

A quick Google of Schottky Diode and TO-220 yielded some sources.

I just tried the first one and then found this:

http://www.onsemi.com/PowerSolutions...do?id=MBR2515L

looks like even slightly better than what I had bought.

You'd lose about 0.3 volts during normal operation.

Datasheet at:

http://www.onsemi.com/pub/Collateral/MBR2515L-D.PDF

I'm sure some googling will find that someplace like DigiKey will have
these and will take small ordering quantities.

Is Paul Remde out there? Might be a nice "kit" to add to your line.
Kit includes 4 diodes, 4 heat sinks, 4 insulating washers some heat
shrink tubing, etc.??

Good luck.




Gary Emerson wrote:
Nyal Williams wrote:

I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


Here is a sketch

http://www.mydatabus.com/public/emer...y/e/sketch.JPG

and a pic of my install...

http://www.mydatabus.com/public/emer...y/e/diodes.jpg

There is a aluminum bracket which is lightly mounted to the bulkhead.
The PC board just provides insulation and some support for the wires.

Each diode has a heat sink, but I don't really think it was necessary.

I don't have the part numbers handy, but I'll see if I can't find
something.

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.

Hi,

I agree that it would be a nice product to offer. Larry Goddard reads this
group, hopefully he'll come up with a good solid product to offer. I'll
copy him on this note as well.

I must admit that I'm not sure I like the automatic switching approach - I
guess I just like to be in control of which battery is being used. The idea
of 2 battery switches and diodes to stop flow seems OK to me, but I'm not
sure it is necessary. I have always used 1 single 3 position switch (Batt
1/Off/Batt 2). I have never had a problem making a fast switch from battery
A to battery B. I wonder if there is a perceived need for something that
really isn't necessary. But I'm not an expert on batteries or diodes.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com


"Gary Emerson" wrote in message
. net...
A quick Google of Schottky Diode and TO-220 yielded some sources.

I just tried the first one and then found this:

http://www.onsemi.com/PowerSolutions...do?id=MBR2515L

looks like even slightly better than what I had bought.

You'd lose about 0.3 volts during normal operation.

Datasheet at:

http://www.onsemi.com/pub/Collateral/MBR2515L-D.PDF

I'm sure some googling will find that someplace like DigiKey will have
these and will take small ordering quantities.

Is Paul Remde out there? Might be a nice "kit" to add to your line. Kit
includes 4 diodes, 4 heat sinks, 4 insulating washers some heat shrink
tubing, etc.??

Good luck.




Gary Emerson wrote:
Nyal Williams wrote:

I'd like to see a full write-up with diagrams, photos,
and names/addresses of places to buy parts. This would
make a good article for Soaring.


Here is a sketch

http://www.mydatabus.com/public/emer...y/e/sketch.JPG

and a pic of my install...

http://www.mydatabus.com/public/emer...y/e/diodes.jpg

There is a aluminum bracket which is lightly mounted to the bulkhead. The
PC board just provides insulation and some support for the wires.

Each diode has a heat sink, but I don't really think it was necessary.

I don't have the part numbers handy, but I'll see if I can't find
something.

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.

Paul Remde wrote:
Hi,

I agree that it would be a nice product to offer. Larry Goddard reads this
group, hopefully he'll come up with a good solid product to offer. I'll
copy him on this note as well.

I must admit that I'm not sure I like the automatic switching approach - I
guess I just like to be in control of which battery is being used. The idea
of 2 battery switches and diodes to stop flow seems OK to me, but I'm not
sure it is necessary. I have always used 1 single 3 position switch (Batt
1/Off/Batt 2). I have never had a problem making a fast switch from battery
A to battery B. I wonder if there is a perceived need for something that
really isn't necessary. But I'm not an expert on batteries or diodes.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

I have the same setup as Paul, and it works fine. However, I have a 302
-- when I had a Volkslogger, this setup would create two separate IGC
files when you switched from one battery to the other.

Gary Emerson wrote:

With 18Amps of forward current capability (each), there isn't really any
"need" for the two diodes in parallel, but for an extra $5 and a few
extra minutes of wiring, if any one diode ever did fail "open" the other
would still provide power. Most likely overkill.
Yes because most often (probably at least 90% of the time) a diode
fails "short"
Therefore you may be reducing the reliability. :-)
...lew...

This is great discussion. I was doing a bit of research myself (it has
been over 10 years since I did any HW design, so am pretty rusty).

Another option that sounds even better is to use the new chips designed
for exactly this to control DirectFETs. That way the voltage drop and
power waste will be significantly reduced with very little additional
cost. The chips I were looking at were IR5001S:
http://www.irf.com/product-info/data...ta/ir5001s.pdf or LT4351:
http://www.linear.com/pc/productDeta...,C1079,P21 73


I have used DirectFET stuff in robotics and found them to be very
reliable and very simple to design with.

My biggest problem is all these components are only available in
surface mount these days and I have never tried to build a circuit
using them.

wrote:
This is great discussion. I was doing a bit of research myself (it has
been over 10 years since I did any HW design, so am pretty rusty).

Another option that sounds even better is to use the new chips designed
for exactly this to control DirectFETs. That way the voltage drop and
power waste will be significantly reduced with very little additional
cost. The chips I were looking at were IR5001S:
http://www.irf.com/product-info/data...ta/ir5001s.pdf or LT4351:
http://www.linear.com/pc/productDeta...,C1079,P21 73


I have used DirectFET stuff in robotics and found them to be very
reliable and very simple to design with.

My biggest problem is all these components are only available in
surface mount these days and I have never tried to build a circuit
using them.

That should be easy enough to do with a pair of suitable power MOSFETs
and an LM358 dual op-amp to control the MOSFETs. If I don't split my
supply (see earlier post) I'm thinking about making this type of circuit
this because the voltage drop in the MOSFET will be very small.

Size isn't an issue - suitable MOSFETs are in TO-220 type packages and
the LM358 is an 8 pin DIP package.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Lew Hartswick wrote:
Gary Emerson wrote:


With 18Amps of forward current capability (each), there isn't really
any "need" for the two diodes in parallel, but for an extra $5 and a
few extra minutes of wiring, if any one diode ever did fail "open" the
other would still provide power. Most likely overkill.

Yes because most often (probably at least 90% of the time) a diode
fails "short"
Therefore you may be reducing the reliability. :-)
...lew...

Fail "short" won't leave you without power on a flight. Fail "open"
might...