Not sure who the OP is here...

I gave some relevant info in another thread (Below), but here's some
additional info.

The lead acid chemistry's voltage goes from just under 12 volts at dead, to
just over 12 V at full charge (Don't remember the exact, but the idea
holds). HOWEVER, this is ONLY after "RESTING" for some time. I never found
out (or perhaps remembered) what this resting time is, but think it is
perhaps half to one hour.

Float voltage is around 13.8 (I have some Yuasa SLAs and they say give a
range of around 13.7-13.9 for float). At the float voltage, they will "take
what they need" to stay charged, but that is NOT the terminal voltage after
resting, or when delivering current. This is what I say above.

In addition to the constant voltage float, you MUST also limit the current
to some maximum (specified my the mfr) when a dead battery is first put on
the charger. With a high current 13.8 supply, you can damage (explode, or
whatever) the battery with too much current at this time. Once the battery
gets up to the 13.8 float voltage, the current will begin to drop and the
constant current part of the charger will fall out of use and you have a
constant voltage, where the battery top itself off thing going on.

Steve

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previous post


Looks like you have some good info from others. Here's a little more.

What you will be doing is not "trickle" charging, but it is called "float"
charging. Lead acid chemistry, similar to Li-ion (unlike in-Cd & Ni-Mh) has
the characteristic that it has a voltage chrematistic such that the terminal
voltage rises between dead and full charge. You can safely put a constant
voltage (but also with a current limit) on the battery and it will seek its
own full charge and the current will taper off, when it gets enough, to what
it needs to stay at full charge. CAUTION -- This voltage is typically
around 13.8, HOWEVER you MUST consult the manufacturer's specs. This
voltage also changes slightly as the temperature of the battery changes.

A commercial device designed for this service is recommended.

73, Steve, K,9.D;C'I







"Highland Ham" wrote in message
...
These SLA =Sealed Lead Acid batteries usually have a charging rate for 2
types of usage The YUASA battery I have in front of me has the following
instructions (applicable at 20 degrees Celcius ) :
Standby Use : Voltage regulation 13.50 -13.80 V Initial current :
No Limit
Cyclic Use : voltage regulation 14.4 - 15.00 V Initial
current:
1.75 Amperes max.

I also use a number of SLAs without such instructions , which I (safely)
charge at 0.1 C (for example a 7Ah battery is charged at 700 mA ) and
limiting the Voltage to 13.5 V ,bearing in mind that 12 V lead acid
batteries are still 70 -80 % charged when voltage has dropped to 12.6 V
To test (charged )12 V lead acid batteries I discharge them at a constant
0.1C current and check the time until the voltage has dropped to 11.9 V
(at that voltage the battery might not as yet be fully discharged ,but
below
that voltage they are of no use to me )

Frank GM0CSZ / KN6WH

+++++++++++++++++++++++
So my question... If it measures 13.8-14v after charging, it should be
fully charged, right? Is there something going on since it is only
drawing
10's of milliamps while charging? I've read that they charge at several
hundred milli's. I'd like to use my QRP rig remotely, and at the rate
its
dropping, I just don't think it will serve the purpose.