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G8MNY > TECH 10.01.24 10:51l 92 Lines 4583 Bytes #999 (0) @ WW
BID : 64376_GB7CIP
Read: GUEST
Subj: Lead Acid Batteries
Path: IZ3LSV<I0OJJ<GB7CIP
Sent: 240110/0942Z @:GB7CIP.#32.GBR.EURO #:64376 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Feb 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
BATTERY OPEN CIRCUIT?
Have you checked to see it they come up with a reverse charge? This is
something that is quite safe to do to a Lead acid (but never a Nicad as they
may explode), as this is how the original batteries were made.
FLAT STATE
+ Plate Electrolyte - Plate
Pb PbSO4 H20 PbSO4 Pb
Grey/White Low SG=1.0 Grey/White
CHARGED STATE
+ Plate Electrolyte - Plate
Pb PbO2 H20+H2SO4 Pb Pb
Brown SG > 1.25 Grey
(SG = Specific Gravity of the Acid measured with a Hydrometer)
There are 2 types of lead (PbSO4) sulphate that is formed on flat batteries,
the first type is conductive & allows normal recharging, the 2nd type that
crystilizes over a long time is hard white lead sulphate that just insulates
the cell plate & inhibits normal recharging unless very high voltages
(>5V/Cell) are applied. But reverse charging (with a suitable current limiting
lamp in series) will break down the hard sulphate immediately, charge until
current drops (as normal). A couple of charge/discharge cycles with a lamp load
to discharge each time will then bring back a heavily sulphated battery to near
normal capacity.
DRY FIT TYPES??
The so called dryfit batteries are actually wet types with a clever seal. They
are just as susceptible to loss of water by over-charging & warm temperatures
as wet batteries are, but your supposed to throw this type away instead of
topping them up!
WET TYPE DRY TYPE
Top up Hidden
Plug Internal Plug
ÚÄÄÂ==ÂÄÄ¿_ Connections_ÚÄÄÂ--ÂÄÄ¿
ÃÛÄÙ ÀÄÛ³ ÃÛÄÙ""ÀÄÛ³
³Û------Û³--Acid Level--³ÛÜÜÜÜÜÜÛ³
³ÛÛÛÛÛÛÛÛ³ ³ÛÛÛÛÛÛÛÛ³ Acid totally
³ÛPLATESÛ³ ³ÛPLATESÛ³ Absorbed in
³ÛÛÛÛÛÛÛÛ³ ³ÛÛÛÛÛÛÛÛ³ separators.
³ßßßßßßßß³Deposit ³ÛÛÛÛÛÛÛÛ³
ÀÄÄÄÄÄÄÄÄÙSpace ÀÄÄÄÄÄÄÄÄÙ
However closer examination of the top of dryfits will show a glued cover over a
set of 6 rubber cup caps that if removed will let the cells be topped up as
normal. Only some success is possible with this method, as over-charging
usually destroys the lead frame in the +ve plate as well & it falls apart.
Cycle charging up to 14.5V (6 cells), 13.8V standard infinite float charge, but
13.5V MAX on sealed cells, as the cannot afford to lose any water!
SAFETY
a) Make sure the battery polarity is correct!
b) Disconnect battery earth first to make +ve connections, as this is safer if
using spanners in confined areas where they are liable to short out.
Reprogram car radio e.g. make sure U have radio security numbers before you
start! The same might go for some types of engine management systems, read
handbook.
c) For your garage, put a sign by the car battery if there is a 2nd battery!
d) Use short runs of suitable gauge wire, remember @ 12V volts are easily lost.
e) Protect wire though bulkheads from chafing damage with suitable grommets.
f) Use suitable fuses. (no nails/ally foil).
g) Make sure 2nd battery fastenings are secure (e.g. in case of accident).
h) Be aware of explosive hydrogen build up on batteries, always "BLOW AWAY"
gases before risk of sparks from connecting leads & crock clips etc!
i) Acid makes holes in clothes, wash any splashes immediately. In eyes wash
immediately & seek medical help.
j) 12V Electrical fires are best stopped with a pair of cutters!
k) Molten copper is HOT & stays hot. Use water on red hot leads.
l) Use RCDs protected mains on outdoor leads for charging/soldering etc.
m) Take extra precaution if gas soldering leads/connectors on/near vehicles!
o) If you are wiring -ve directly to battery then fusing the -ve to rig, this
protects against faulty battery earth straps, (rig fire on starting car!)
------------------------------------------------------------------------------
Tony, G8TBF says there is another way to recover batteries that have gone high
resistance due to being left idle for long periods.
Connect a bridge rectifier across the battery, + to +, & supply this from a
240V AC source in series with a 15W or 40W light bulb. The supply should
preferably be from an isolating transformer..... 73, Tony, G8TBF.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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