wanted 10 amp battery charger schematic ?

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hi, any body  have or know of a schematic for a 10  amp lead acid  charger
for car batteries ?
something sorta basic , which  keeps it on trickle charge, after its fully
charged ..
ive had a look around on the net ,  but nothing really what i want.

thanks.
mark k
--





Re: wanted 10 amp battery charger schematic ?


On Thu, 07 Apr 2005 04:19:09 GMT, "mark krawczuk"

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How much are you prepared to pay?
Do you want off-the-shelf or DIY?


Re: wanted 10 amp battery charger schematic ?



"Ross Herbert"
"mark krawczuk"
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 **  An off-the-shelf or DIY  ***schematic***  ???




............    Phil



Re: wanted 10 amp battery charger schematic ?


On Thu, 7 Apr 2005 14:51:09 +1000, "Phil Allison"

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Touche Phil...

Ok, the first question still applies though. It all depends what parts
the OP has on hand. If he has a suitable transformer and bridge
rectifier he might add a Projecta 2 stage charge controller like the
BM140
http://www.projecta.com.au/products/index.php/productserial/20/command/viewproduct/categoryserial/10
and discussed in this forum
http://www.exploroz.com/Forum/Archive/2005_1/20618.asp . If it does
indeed cost only $50 then building something from scratch might be
more expensive.

Ross H


Re: wanted 10 amp battery charger schematic ?


On Thu, 07 Apr 2005 04:19:09 GMT, "mark krawczuk"

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DC supply--->current limit cct----->voltage regulator cct--->battery

When first connected the battery charges at 10 amps max
set by the current limit circuit.

As the battery volts rise to near 13 point (whatever you want)
volts, the current drops off to a trickle or float charge.

If the float charging is happening too soon just fit a switch
or knob to bump up the voltage regulator output so that
the charger operates in constant current mode for however
long you want. 10 amps times 10 hours = 100 amp hours.

Here is an example of current limit regulators
and constant  voltage regulators using LM317
http://www.national.com/ds/LM/LM117.pdf
Look at the bottom left hand corner of page 16.

Build those two circuits and see if they please you
knowing that the current limit is 1 amp.
If you are happy,  boost the current handling of
both the current limit and voltage regulator circuits
to ten amps.   That data sheet has some ideas.
The web will show you more current boosting ideas.

If you had a handful of tiny toggle switches you
could put ten in a row that switched in or out ten
LM317s set for 1 amp current limit a piece connected
in parallel.
That is a bit over the top I know but I like that idea.
Simple, and easy to see what the current is set to.
Five switches on gives five amps.
Ten switches on gives 10 amps.
Forget that idea if you have to buy retail.

Regards,
John Crighton
Hornsby



Re: wanted 10 amp battery charger schematic ?



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Basic requirements are a transformer and a rectum frier.  You'll need
a hefty transformer (150VA at least) and a 50A bridge rectifier.
You'll probably find a schematic in the back of the DSE catalogue (if
they still print one).

You should also note that most commercial chargers only have around
half the claimed output -- ie a charger labelled 10A will output
around 5A.  They apparently use some tricky electrical formula, like
multiplying the actual DC output by 2.  The price tends to rise
exponentially if you want real amps (as does its capacity to boil
batteries dry).


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It's no longer basic if you want it regulated.  Easiest and cheapest
way for only 12V use might be to to use Oatley's solar regulator kit
in conjunction with a rectified supply or basic charger.  It's a very
nifty regulator circuit (costs around $30).

If it is only for a 12 volt battery you can probably buy a hefty
regulated DC supply for a lot less then a commercial charger.  Wes
have a 13.8V 6A supply for around $100 (trade).  Some adjustments will
be required -- not exactly rocket science but some basic knowledge
necessary.

Jaycar once offered a kit for a 6, 12 and 24V 10A regulated charger
from Silicon Chip, which they've since dropped.  Price at the time was
around $200 for 6 and 12 volt or nearer $300 for 24V 10A (transformer
upgrade required). Alternatively you could use a smaller transformer
and limit the output to 8A.  You can no doubt buy the reprint from SC
and source the necessary bits.  It's a relatively complex project for
a beginner though.  It also has a raw output of 50V or so which isn't
without risks for the unwary.

I've been using one for a number of years without serious complaint.
Price wise it was a bargain.

--
John H

Re: wanted 10 amp battery charger schematic ?



"John_H"

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**  Nearly all car battery chargers are labelled with  " RMS Amps "  -
which is a blatant scam.  Because current is delivered into the battery via
100 Hz pulses the RMS value is much higher than the average DC value. Of
course, its the latter that actually produces increased charge in the
battery.

The practice arose from the common use of moving iron current meters to
monitor charge rate  -  these meters are rms responding by nature.




.............    Phil



Re: wanted 10 amp battery charger schematic ?


On Thu, 07 Apr 2005 04:19:09 GMT, "mark krawczuk"

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If you do have a suitable transformer and bridge rectifier you might
consider the add-on picaxe circuit in Silicon Chip Circuit Notes Sept
2004 http://www.siliconchip.com.au/cms/A_102420/article.html

There is an updated (Jan 05) program listing in a zip file at the
bottom of the page.


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