Diode replacment

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Need to use a diode to prevent two batteries seeing each other when =
connected in parallel.  Not wanting to drop .6v with the diode is there =
something like a Mosfet I could use which I believe will only drop the =
voltage .2v?  Needs to be able to handle 30A and preferably 40A for =
safety factor.  Is never used for more than 30 minutes at a time.

Many thanks in anticipation for your knowledgeable assistance.

Paul

Re: Diode replacment



"Paul Noisette"

** Please do not post in  HTML   !!!!!!!!!!!!


Need to use a diode to prevent two batteries seeing each other when
connected in parallel.  Not wanting to drop .6v with the diode is there
something like a Mosfet I could use which I believe will only drop the
voltage .2v?  Needs to be able to handle 30A and preferably 40A for safety
factor.  Is never used for more than 30 minutes at a time.


** You totally fail to decribe what you are after or for what actual
purpose -  dickhead !!

From the large amp numbers you possibly are on about  12 volt car batteries
being operated in parallel.

If so -  go see Jaycar.

http://www.jaycar.com.au/productView.asp?ID=MB3670

If not,  then  TELL  US  WHAT  YOU  ARE  DOING  !!!!



.....  Phil





Re: Diode replacment



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Who says you dictate the posting rules Dipshit?

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Re: Diode replacment




Alan Rutlidge wrote:

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It is invariably considered bad form / netiquette to post html messages to
Usenet.

Graham

--
due to the hugely increased level of spam please make the obvious adjustment to
my email address



Re: Diode replacment


On Sun, 12 Jul 2009 12:29:42 +0800, "Alan Rutlidge"

:
:>
:> "Paul Noisette"
:>
:> ** Please do not post in  HTML   !!!!!!!!!!!!
:
:Who says you dictate the posting rules Dipshit?

With respect Alan, whatever the OP did to post his message, it causes the text
to come out on my newsreader as one long line of text and I have to scroll
horizontally to read it all. He should correct whatever he did so that it comes
out as wrapped lines of plain text.


:
:>
:>
:> Need to use a diode to prevent two batteries seeing each other when
:> connected in parallel.  Not wanting to drop .6v with the diode is there
:> something like a Mosfet I could use which I believe will only drop the
:> voltage .2v?  Needs to be able to handle 30A and preferably 40A for safety
:> factor.  Is never used for more than 30 minutes at a time.
:>
:>
:> ** You totally fail to decribe what you are after or for what actual
:> purpose -  dickhead !!
:>
:> From the large amp numbers you possibly are on about  12 volt car
:> batteries being operated in parallel.
:>
:> If so -  go see Jaycar.
:>
:> http://www.jaycar.com.au/productView.asp?ID=MB3670
:>
:> If not,  then  TELL  US  WHAT  YOU  ARE  DOING  !!!!
:>
:>
:>
:> .....  Phil
:>
:>
:>
:>
:

Re: Diode replacment



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Reads perfectly okay on mine. :-)
Not many complain except maybe PA.
But then again he craves attention a little like Rod Speed.
Were they hatched from the same unholy union?  One wonders....

 



Re: Diode replacment


2 100ah 12v batteries that are used independently of each other. To power
the invererter for short period with 280w on AC needs the batteries to be
paralled. With the batteries at differing states of charge dont want 1
battery attempting to charge battery 2. Realise that one battery will supply
more power till they equalise, but generally there is not much difference
between the batteries. However the batteries cannot be directly connected.

Since found this article
http://www.siliconchip.com.au/cms/A_103360/article.html

Going on that article I would need a P-channel Mosfet as the negative cannot
be isolated. In the Jaycar catalogue there is only a IRF9540N 100v 23A
http://www.jaycar.com.au/productView.asp?ID=ZT2467&keywords=ZT2467&form=KEYWORD
can these be placed in parallel to increase the current rating?
is there a higher powered P-channel Mosfet easily obtainable?
will the Mosfet need a heat sink?

Take it the Gate is the negative power for switching, the Source is the 12v
battery supply and the Drain is the power to the inverter.  Is that correct?

Many thanks to those offering their help and expertise.



Re: Diode replacment



"Paul Noisette"

** Now you are posting in mid air  = no context visible and no refeences to
previous posts.

  Says a lot about your thinking - or rather the lack thereof.


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**  SLA ( ie gell cell)  or wet cells or other kind   ??

     Leaving this info out is really stupid.


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**  Kindly state why.

 Your Q may disappear with the correct answer.


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** This may be a false concern.


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**  Kindly state why.

 Your Q may disappear with the correct answer.



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** Purley reverse polarity protection for the load.

 Something far better done with a relay and one, small diode.



......   Phil




Re: Diode replacment - some kind person with manners please assist me.



"KR"

Trust me mate, some posts in recent months have clearly shown that
there are worse dickheads (call them what you may) on here than Phil.


**  Am I being condemned here with faint praise   ?????


Batteries have been paralleled in these sort of applications for
decades without problems, that is probably
why we need to know more about the application you need it for, as its
a very unusual setup you are asking about.


**  The OP has his reason  -  but it is not ours to know.


I wouldn't advise putting anything in series with them, it will only
waste power and generate significant heat
at the sort of currents you are talking about.
With those sort of currents, you want as low a resistance as possible
in the cables, connectors fuses etc.


** Water off a dope's back  -   I fear.

 Nice try at concilliation , anyhow




.....  Phil





Re: Diode replacment - some kind person with manners please assist me.


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No, not condemned, I would explain it as - yes you are rude at times,
but I got used to it years ago, and unlike
some on this group, I don't really care about it, but on the other
side you do have knowledge of electronics (which is the purpose of
this group) unlike some on here.


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Yes, as I see more and more these days, efforts with many people are
futile, better off saving energy
for something else. This can get so frustrating.  For example, trying
to show someone how to do something, being constantly interrupted,
asked irrelevant stupid questions that break concentration, and then
having them go
off and do the job some wrong way that doesn't work, and you have to
go in and clean up the mess afterwards.
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Re: Diode replacment



:2 100ah 12v batteries that are used independently of each other. To power
:the invererter for short period with 280w on AC needs the batteries to be
:paralled. With the batteries at differing states of charge dont want 1
:battery attempting to charge battery 2. Realise that one battery will supply
:more power till they equalise, but generally there is not much difference
:between the batteries. However the batteries cannot be directly connected.
:
:Since found this article
:http://www.siliconchip.com.au/cms/A_103360/article.html
:
:Going on that article I would need a P-channel Mosfet as the negative cannot
:be isolated. In the Jaycar catalogue there is only a IRF9540N 100v 23A
:http://www.jaycar.com.au/productView.asp?ID=ZT2467&keywords=ZT2467&form=KEYWORD
:can these be placed in parallel to increase the current rating?
:is there a higher powered P-channel Mosfet easily obtainable?
:will the Mosfet need a heat sink?
:
:Take it the Gate is the negative power for switching, the Source is the 12v
:battery supply and the Drain is the power to the inverter.  Is that correct?
:
:Many thanks to those offering their help and expertise.
:


There is a little more to using mosfets to isolate two heavy duty 12V batteries
than you seem to imagine. Usually, these devices are incorporated into what are
sometimes known as "Smart" dual-battery isolators, to distinguish them from the
"dumb" diode-only type of isolator.

For example, here is a design by Dave Johnson which incorporates paralleled
P-channel mosfets to give only 50mV drop, driven by a dedicated control IC.
http://www.discovercircuits.com/H-Corner/bat-iso.htm

Note that the mosfets must be on a decent heatsink to handle above 20A.

Re: Diode replacment


tell me where you live you filthy stinkin   rotten  phil  the turd =
allison..

there i just posted in html to piss you ioff philthy phil.



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Re: Diode replacment



    I would strongly suggest that drastic action not be used but by all
means
    give him a call.  He is listed in the Sydney White Pages under
Phillip
    (Martin) Allison
    8 Tintern Rd Ashfield NSW 2131 (02) 9799 8242

    BTW when you have a look via Google Maps at the dingy flats he lives
in have
    a look across the road and you will see a park and some public
toilets.
    Nothing like being near to where the action is eh? ;-)


   ALLMAN Park?  Would the even let Phil in?

--
You can't have a sense of humor, if you have no sense!

Re: Diode replacment


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Try this from Farnell. Make sure you use a big heatsink.


http://au.farnell.com/vishay-formerly-international-rectifier/80cpq020pbf/diode-schottky-2x40a-20v-to-247/dp/1013352


David

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