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G8MNY > TECH 14.09.15 10:01l 83 Lines 3590 Bytes #999 (0) @ WW
BID : 42720_GB7CIP
Read: GUEST
Subj: Auto SCR Charger for Car Batts
Path: IW8PGT<IV3ONZ<IZ3LSV<I0OJJ<GB7CIP
Sent: 150914/0831Z @:GB7CIP.#32.GBR.EURO #:42720 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Mar 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Here is a commercial design I came across, ideal to leave across your spare
battery knowing it will not damage it with overcharge.
FEATURES
Reverse connection protection
Auto charge on low battery
Auto shutoff on charged battery
LED Charging state indicators
13A FUSE
ÉÍÍÍ0---0ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ> + BATTERY
º
ÇÄÄÄÄÄÄÄÄÄÄÄÂÄÄ´>ÃÄÂÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
º ³ D1 ³ ³+1u ³ ³ ³ ³
_ ÉÍ)ÍÍÍÍÍÍÍ» ³ e\³ === e\³ ³ _³_ ³
)||( º º ³ BC577 ÃÄÄÄ´ ÃÄÄ2k7ÄÄ>220 \_/-> ³
)||(__º 6 Amp º ³ TR1 /³ ³_____/³ P1³ ³ CRG COMP ³
)||( 14-0-14v º 2k7 _³_ ³ BC557 _³_ ³ LED ³
_)||( º ³ <-\_/ ³ TR2 '/_\ ³ ³
_º_ 2x 8A _º_ ³ CRG ³ 22k 11V ³ 1k 11V _³_
/_\Ä¿SCRÚÄ/_\ ³ LED ³ ³ Z1 ÀÄÄÄÄ´ Z2 '/_\
º _³_ _³_ º ³ 470ê ³ \³ ³
º /_\ /_\ º ³ ³ ³ BC107 ÃÄÄÂÄÄ2k7ÄÄ>220 P2
º ÀÄÄÄÁÄÄ)ÄÄÄ)ÄÄÄÄÄÄÙ ³ TR3 e/³ ³+ ³CHARGED
º D2 D3 º ³ ³ ³ ===47u ³
º º ÃÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ
º º ³
ÈÍÍÍÍÍÍÍÍÍÊÍÍÍÏÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ> - BATTERY
Not shown for simplicity is the mains fuse & mains neon indicator.
HOW IT WORKS
With mains connected nothing happens until voltage from a correctly connected
battery is applied (not a totally flat battery!). Then TR1 will be turned on
through D1 & spike filter 22k & 1uF.
TR1 turned on, lights the Charge LED, & via D2 & D3 triggers the 2 charging
SCRs. Charging current is limited only by the transformer type, leads & SCR
voltage drop, it flows through the 13A protection fuse to the battery.
When the battery voltage exceeds the threshold of about 14.5V, TR3 is turned on
via Z2, pot P2 & filter 2k7/47uF. TR3 turning on lights the charge completed
LED, & via Z1, pot P1, turns on charge stop transistor TR2. The charged
completed LED starts to light up more & more indicating the battery state until
the charge is eventually stopped. Preset Pot P1 sets the loop gain & stop
/restart start sensitivity.
CONSTRUCTION
The transformer must be suitable for this purpose or have tappings to let you
adjust the current to be safe.
The 2 SCRs are mounted on an aluminium plate or the case with insulation kits,
but they do not get very hot in practice (less than a bridge rectifier).
Thick leads (top & bottom of the drawing) must be used to the battery, as added
voltage drop can make the battery seem charged early!
DRAWBACKS from Frank I0ZV & Harry M1BYT...
1/ There is some discharge current flowing all the time. (10s of mA)
2/ The mains is still powering the unit.
3/ Not able to charge a totally flat battery of 0v.
These could have all been designed out, but the above unit I have not modified.
MODIFICTION
With some old batteries I found cells would short out some time during the
charge & get yhe charger & battery very hot & take out the fuse.
To speed things up I added a resettable 10A trip. This breaks the circuit much
earlier.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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