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G8MNY > TECH 26.12.05 18:13l 76 Lines 3831 Bytes #999 (0) @ WW
BID : 10490_GB7CIP
Read: DL1LCA GUEST OE7FMI
Subj: Regulating 12v Generator Output
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0AR<GB7CIP
Sent: 051226/1608Z @:GB7CIP.#32.GBR.EU #:10490 [Caterham] $:10490_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Oct 05)
Small generators often provide unregulated charging outputs. These can easily
over charge your /P battery & cause damage & excessive battery voltages across
low power lamps & other kit.
Here is s simple & efficient charge limiting SCR regulator that can be put in
the lead at the battery end.
FEATURES
1/ Charge output gradually shut of at 14V (dependent on Zener voltage).
2/ Low loss (1v) as it is an SCR & not a linear regulator.
3/ Generator connected LED, this lights when DC appears from the generator.
4/ Charged LED, gradually lights up as the battery needs less genny O/P for 14v
5/ Battery lead isolation, no battery DC to short out @ the generator lead end.
6/ No battery drain, the circuit does not take current from the battery.
CHARGED ||
LEDÚÄÄ´>ÃÄÄÄÄÂÄÄÄÄ´>ÃÄÄÄÄÄ¿
³ ³ ³
³ + 100u ³ ³
ÃÄÄÄ´ÃÄÄÄÄ´ 10A 470
TRIP + ÃÄÄÄ2K2ÄÄÄÙ SCR ³ Fuse
ÚÄ´>ÃÄÄÄÄÄÄÄÄÄÄÂÄo--oÄÄÄÄ<<ÄÄÄÄÄÄÄÁÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄ´>ÃÄÄÄÁÄÄÄÄ>>ÂÄo-oÄ>loads
³ ³ GENNY LEAD _³_GEN 270 ³g CROCK³
³ ÚÄÄÄÄÄÄÄÄ)ÄÄÄÄÄÄÄÄÄ<<ÄÄÄÄÄ¿ =\_/ OK ÃÄ´>ÃÄÙ ³
³ 20v ³ 20v ³ CONECTOR - ³ ³ LED _³_ ÄÄÁÄÄ 12V
ÀCCCCCCCCCÄ´>ÃÄÙ ³ ³ /_\'14.5V === BATTERY
========= ³ 1K ³ CLIPS³
ALTERNATOR ÀÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ>>ÁÄÄÄÄ>
SCR mounted on heatsink
HOW IT WORKS
The raw DC peaking well over 20 volts off load lights the GEN OK LED to the 1K
to -ve. The 20V also provides up to 14.5V on the zener. This puts 14V onto the
gate of the SCR via a blocking diode. If the battery voltage is much less than
this the SCR will be triggered & put nearly all of that 1/2 cycle of DC from
the generator into the battery. When that half cycle of current stops the SCR
is ready for the next voltage comparison & trigging for the subsequent half
cycles etc.
As the battery charges the voltage rises & the SCR is triggered later & later,
in fact a crude form of phase firing naturally occurs, as the battery voltage
falls from the last current burst as the zener voltage rises..
25v_ _ _ 14vÄ´_ .""""----....."""--- BATTERY VOLTAGE
³ /' `\ /' `\ 11vÄÙ ""FLAT 11V CHARGED 14V
14vÄ´ | | | | 14vÄ´ .-""""-. .-""""-.
³ ³ ³ ³ ³ ³ | | | | ZENNER VOLTAGE
0v_³V_________V_________V 0v_³V__________V__________V
OFF LOAD GENNY DC TRIGGER | early | late
This does what you need for charging, it turns the current down as the voltage
comes up & stops excessive gassing. Eventually just the odd trigger occurs
keeping the voltage @ 14v.
If the charge current is small (small genny eg. 8A max), the battery a big one
with low internal resistance, then the hum across the battery MIGHT be small
enough not to cause hum problems at all with kit like a 25Amp SSB rig.
DC CHARGING WITH AC LOADS
Some generators warn you not to use both DC & AC outputs at the same time. This
may not be due to a loading or regulation problem, but due to safety! This is
because the DC output winding is often part of the 230VAC load winding, & that
can put DC onto the AC output or bypass some of the safety trip features, as
well as MAKING THE 230V NON FLOATING & therefore more hazardous!
If you intend to use both at once do at least use a ELCB/RDC mains trip plug!
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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