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G8MNY > TECH 29.04.15 10:06l 67 Lines 3256 Bytes #999 (0) @ WW
BID : 28800_GB7CIP
Read: GUEST
Subj: 7AH "F" NiCad Battery Pack
Path: IW8PGT<IW7BFZ<I3XTY<I0OJJ<GB7CIP
Sent: 150429/0612Z @:GB7CIP.#32.GBR.EURO #:28800 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update Apr 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Nicads batteries usually end up with several cells being short circuit, this
means that trickle charging is no good & will not recover the shorted cells!
What is needed is higher pulse current charging to remove crystal growth.
This circuit charges each cell independently, & I have used it on very old
nicad pack of >15years. If a cell has shorted crystal growth across its plates,
then 20W is available to blast it off.
Using 12 cells gives a better voltage for most /P kit but 10 cells can be used
if the kit really can't stand 16V of a just charged battery!
The diodes are 3A (60A max) soldered to the tags of the battery stack. They
will run quite hot on charging!
_________________________
_ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ -
º(_ AC1 ÚÄÄÄÄ´<ÃÄ´ ³ ÚÄÄÄÄ´<ÃÄ´
ÄÄÄÄ¿ º _ ³ _Á_ ³ ³ _Á_
)º(_ AC2 AC ÄÄ)ÄÄÄÄÄÄÄÄ´ ³ AC ÄÄ)ÄÄÄÄÄÄÄÄ´
)º _ 1 ÄÄ´ _Á_ ³ 2 ÄÄ´ _Á_
MAINS )º(_ AC3 ÀÄ´>ÃÄÄÄÄ´ ³ ÀÄ´>ÃÄÄÄÄ´ 12-16V
)º _ MULTI- ÚÄÄÄÄ´<ÃÄ´ ³ ÚÄÄÄÄ´<ÃÄ´ TO
)º(_ AC4 PIN ³ _Á_ ³ ³ _Á_ LOAD
)º _ PLUG & AC ÄÄ)ÄÄÄÄÄÄÄÄ´ ³ AC ÄÄ)ÄÄÄÄÄÄÄÄ´
)º(_ AC5 SOCKET 3 ÄÄ´ _Á_ ³ 4 ÄÄ´ _Á_
ÄÄÄÄÙ º _ ÀÄ´>ÃÄÄÄÄ´ ³ ÀÄ´>ÃÄÄÄÄ´
º(_ AC6 ÚÄÄÄÄ´<ÃÄ´ ³ ÚÄÄÄÄ´<ÃÄ´
40VA TRANSFORMER ³ _Á_ ³ ³ _Á_
CORE WITH 6x AC ÄÄ)ÄÄÄÄÄÄÄÄ´ ³ AC ÄÄ)ÄÄÄÄÄÄÄÄ´
IDENTICAL 2V 3A 5 ÄÄ´ _Á_ ³ 6 ÄÄ´ _Á_ FUSE
WINDINGS ÀÄ´>ÃÄÄÄÄÁÄÄÄÙ ÀÄ´>ÃÄÄÄÄÁÄÄo/oÄ +
12x 7AH "F" CELLS
MODIFY A TRANSFORMER
1/ Rewind a suitable unvarnished transformer (12V @3A).
2/ Carefully take the laminations off.
3/ Remove the secondary,
4/ divide it up into 6 (will need a large garden for this).
5/ wind it all back on 6 wires together.
6/ Test the windings to make sure they are all separate.
7/ Replace the interleaved laminations (the odd one left over does not matter
much!)
8/ Suitable transformer tags for terminating the windings are useful.
9/ Test with mains, it should not get hot!
CONNECTOR
With 3A multicore wire, wire up the battery to a female multi-pin socket & the
transformer to a plug (e.g. 25 way RS232 with 2 pins per connection).
CHARGING
In use you must disconnect the battery pack after it runs hot (45øC). The time
taken will depend on the exact secondary voltage available, as well as the
state of charge of the cells. Cell lifetime has been at least 20 years for some
of my cells, but some go open circuit eventually (hummy voltage across them on
charge), none have gone short over that time!
If trickle charging is wanted as an option, add a switched 220ê 20W in series
with the mains circuit (e.g. Neutral).
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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