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G8MNY > TECH 25.08.06 11:19l 85 Lines 4383 Bytes #999 (0) @ WW
BID : 43552_GB7CIP
Read: DL1LCA DL1RX GUEST OE7FMI
Subj: Regulating 12V Generator Output
Path: DB0FHN<DB0MRW<DK0WUE<7M3TJZ<ON0AR<GB7CIP
Sent: 060825/0009Z @:GB7CIP.#32.GBR.EU #:43552 [Caterham] $:43552_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Jun 06)
(8 bit ASCII Graphics use code page 437 or 850)
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 1N4001 ³
³ + 100u ³ ³
ÃÄÄÄ´ÃÄÄÄÄ´ 10A 470ê
TRIP + LONG ÃÄÄÄ2k2ÄÄÄÙ SCR ³ Fuse
ÚÄ´>ÃÄÄÄÄÄÄÄÄÄÄÂÄo--oÄÄÄÄ<<ÄÄÄÄÄÄÄÄÄÁÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄ´>ÃÄÄÄÁÄÄÄÄ>>ÂÄo-oÄ>loads
³ ³ GENNY THICK _³_GEN 270ê ³g CROCK ³
³ ÚÄÄÄÄÄÄÄÄÄ)ÄÄÄÄÄÄÄÄÄ<<ÄÄÄÄÄÄÄÄ¿ =\_/ OK ÃÄ´>ÃÄÙ ³
³ 20V³ 20V ³ CONNECTOR - LEAD ³ ³ LED _³_ 1N4001 ÄÄÁÄÄ 12V
ÀCCCCCCCCCÄ´>ÃÄÙ ³ ³ /_\'14.5V ÛÛÛ BATTERY
========= ³ 1k ³ Zener CLIPS ³
ALTERNATOR ÀÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ>>ÁÄÄÄÄ>
SCR mounted on heatsink
HOW IT WORKS
The raw DC peaking well over 20V 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..
14VÄ´ .------. -....__-----....____
25V_ _ _ 13VÄ´ | `\ BATTERY VOLTAGE
³ /' `\ /' `\ 12VÄÙ__³ FLAT 11V CHARGED 14V
14VÄ´ | | | | 14VÄ´ .-----. .-----.
³ ³ ³ ³ ³ ³ /' `\ /' `\ ZENER 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.
NOISE & LEAD LENGTH
Using the low voltage output means thick short leads! This does not help the
noise isolation problem. If you are closing doors on the lead do make sure it
is not crashed! If you are using long leads due to noise, then made sure that
are VERY THICK. eg. A 30A cooker lead with the 3rd earth wire bonded to -ve up
to say 10m long for an 8A charge lead, if the losses are not to be too great.
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 loading or regulation problems, but due to safety! This is
because the DC output winding is often part of the 230V AC 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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