Today's Message Index:
----------------------
1. 10:57 AM - Re: Z-12N based architecture review request (N1921R)
2. 07:33 PM - Re: One for the battery gurus: recovery from deep discharge (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Z-12N based architecture review request |
esco wrote:
> ... Bill Judge is very clear about the need to connect to the switched side of
battery contactor...
It is not necessary to connect the Monkworkz regulator current output to the switched
side of the master contactor/main bus, only that it be disconnected from
the battery somehow while parked to prevent its parasitic load from depleting
the battery.
I show it connected to the engine/essential bus which is on the forward side of
the firewall. This way the engine will run with the main bus offline, for instance
in the smoke in the cockpit scenario. Snip attached. More complete PDF schematic
in folder 1) / A) here
The OP has seen this but maybe others have thoughts.
--------
John Bright, RV-6A N1921R, working on FWF.
Single battery, alternator on main bus, Monkworkz generator on engine/essential
bus.
My links <a href="https://docs.google.com/document/d/1YOtPiA3AdUsQEYR4nodBESNAo21rxdnx4pFs7VxXfuI/edit?pli=1">here</a>
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=513177#513177
Attachments:
http://forums.matronics.com//files/n1921r_electrical_power_schematic_snip_141.jpg
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: One for the battery gurus: recovery from deep |
discharge
At 04:09 PM 1/30/2024, you wrote:
>
>I have an SBS-J16 battery in an aircraft in
>which the battery master was left on for two weeks (I know).
>
> When found, the open circuit terminal voltage
> had dropped to 2.2 volts. A Dewalt
> sophisticated battery charger didn=99t want to have anything to do
with it,
Yeah . . . many smart chargers do a pre-assessment of the target
battery and will not take on the task unless the terminal voltage
is above some minimum level . . . I have a couple chargers that
do this.
A temporary parallel connection of the smart-charger and some
other voltage source, like another battery will often convince
the charger that it's time to go to work.
Now, recall the days long before RG/GlasMat batteries.
The 'wet' stuff inside was (and still is) a dilute mixture
of water and sulfuric acid. Pure water is a very poor
conductor of electrons . . . but adding some
combination of free ions like salt, sodium bicarbonate,
or sulfuric acid to the water and it becomes a ready
conductor of current.
Recall that we could test the relative state of
charge for a lead-acid battery by measuring the
electrolyte's DENSITY with a hydrometer. The
legacy float/in/glass hydrometer is generally
calibrated in density vs. state of charge
where electrolyte 12% greater than 1.000
(pure water) is zero-percent; 26% is full
charge.
Note in attached figure (shamelessly stollen
off BatteryUniversity.com), 0% state of charge
on a 12 volt produces an open circuit reading
on the order of 11.9 volts.
You cited an open circuit voltage of 2.2 volts . . .
Hmmmm . . . less than 0% state of charge?
Actually, yes. Active material in the plates
had sucked still more acid from the electrolyte
than what would produce any useful energy
from the chemistry.
The closer to pure water . . . the more depressed
conductivity. Hence, first attempts to push energy
back into the battery will be met with lots of
resistance . . . no pun intended.
I recall reading a qualification test on
a Concorde battery document where a fully
discharged battery is dead-shorted for a
period of time after which a recharge
protocol calls for applying a higher than
normal voltage until significant recharge
current is observed. The test proceeds with
a normal constant voltage/constant current
charge. After top-off, the battery is cap-checked
and must demonstrate some minimum.
I dug around in the library but could not
come up with that document so I cannot quote
exact times and values. But note that this
is a quality test for a new battery. While
a certain level of degradation is expected,
the battery is EXPECTED to recover by some
minimum amount required for return to
service.
> so I=99ve now put it on charge with my bench
> power supply at 14.4V limited to 4 amps.
>Initially the battery resistance was very high,
>and increasing - the voltage was limited at
>14.4V and the current dropped from 1.3 amps, to
>about 1.1 amps, within a couple of minutes, and
>then started to ramp up, about 1mA per second.
>After being on charge for an hour or so, the
>current it is accepting has risen so the current
>limiting has kicked in, presently at 4 amps and
>the terminal voltage has dropped to 14.3 V.
Yup, this is expected and you may well
recover this battery to some level for
continued service. After a 24-hour float
at 14.4, let it see idle for 24-hours
then do a cap check followed by recharge
and a load test.
>I=9Dm curious why the resistance was so high to
>start with, why it has now dropped (to what
>seems =99normal=99 charging behaviour to me) and
>also to know if this battery has a chance of
>resurrection,. It=99s only a couple of years
>old, so if it will soldier on after its
>mistreatment, I would be happy. What are my chances, do you think?
As Lord Kelvin oft admonished, if you
don't know the numbers, what you DO know
is of limited value.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=======
=
< Go ahead, make my day . . . >
< show me where I'm wrong. >
========================
========
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|