[Elecraft] Fwd: Bioenno's July Promotion

[Guy Olinger K2AV]

Hi Wes, et al.

I went looking through emails from you to find the reference, because I
wanted to read it. I did not locate or recognize the reference in those
emails. That aside...

For conversation purposes I'll begin this assuming a flooded wet cell
battery. That's because I have a pair of T-105 6 volt 225AH cells in series
in my RV to supply the "house" "12" VDC needs. T-105's have been very
common in golf carts for decades. In larger RV's it's not uncommon to see
four T-105's in series parallel to supply house 12VDC. T-105's are large
deep cycle flooded wet cells. They are an easy choice for an RV's house DC
circuits. It's a very mature application, over 30 years of this scheme in
RV's.

An RV has extensive "12" volt wiring. The actual satisfactory running DC
voltage on the house DC wiring can be 11 to 14.4 volts. To supply the house
DC from RV park AC mains, the RV uses a high amperage three stage battery
charger, with anywhere from 35 to 100 amps bulk charge rate depending on
the specific battery type and configuration. Nomenclature in the RV
business for this charger is "converter/charger" which I will denote
hereafter with "C/C".

The C/C serves two functions: 1) Supplies all the myriad 12 volt RV stuff:
lights, blowers, fans, plus controls for fridge, heat, hot water heater,
just to name a few. It converts the park AC to DC. 2) Charges the batteries
to keep them ready for a common and deliberate operation of the RV without
an AC voltage source, as in a park without electric hookups during
no-generators-running quiet time. It's very common to run an AC generator
from early afternoon until after supper to supply air conditioning, power
the microwave, and recharge batteries. Then the generator is shut down and
all runs off the house batteries until the next afternoon. A lot of us keep
small inverters, 12VDC to 120V, to power cellphone chargers, game boxes,
etc, when on batteries.

The charging stages are:

1) Bulk charge, current limited. Where up to 80% of the battery energy
capacity is replaced by the charger at maximum steady current amp rating of
the charger. This charge current continues until the battery voltage
reaches 14.4 volts.

2) Absorption charge, voltage limited. Voltage is held at a constant 14.4
volts and the current declines until the battery is 98% charged.

3) Float charge, voltage and current limited. Not more than 13.4 volts and
usually less than 1 amp of current **into the battery**. This in time will
bring the battery to 100% charged or close to it. This maintenance float
charge will not boil or heat batteries but will maintain the batteries at
100% readiness and prevent cycling during long term inactivity. Some Gel
Cell and AGM batteries may require different settings or chargers specific
to the battery. This is related to differing optimal voltages and heat
sensitivities. But the rough concept is the same.

When the C/C is running from RV park or generator AC, the RV's DC bus is
supplied from the C/C. In float charge the C/C will supply the RV DC at
13.4 VDC. If the AC cuts out at the park or the generator goes off, the
house DC circuits will begin to discharge the battery. The battery voltage
will quickly drop to the normal battery discharge curve in the upper 12.x
range and continue down.

When the AC comes back on, before it kicks in, the C/C detects that the
battery is down on the discharge curve and re-initiates at step 1).

The stink when many hams talk about operating their shack with a battery
float, is that they envision hooking a battery to the output of a plain
single voltage Astron RS35 or some such, the usual 13.8 volts regulated,
fixed supply. One cannot properly care for a battery this way, because it
needs the three charge stages for good health. If what one meant by float
was a "single voltage float", then no, one cannot *properly* float a
battery on one's ham station. After the first discharge event, the battery
will not recharge to full charge. It needs the bulk charge voltage to
recharge.

However, I would not call my RV a "battery float", because "float" is only
*one* charge condition of the three RV C/C charge states. But I do have ham
friends who call that "float" because that's how the wires run. This little
double meaning can make for some confused conversations until the specifics
are brought to light.

If what you meant is battery always in the circuit, no blip switching
interruptions from the "uninterruptible" UPS, then yes, you can use the RV
style setup in a ham station, **with a list of caveats**. You probably do
not want to use T-105's for a number of reasons. But you will need to
obtain a three or four stage charger setup designed for an appropriate
battery.

Caveats:

a) You need an RV style charger-converter, or equivalent specifically
matched to the battery. Some equivalents have been described in this
thread.

b) The bulk charge rate of the C/C must match the battery normal charge
maximum. More C/C bulk charge amps than the battery max normal charge rate
is NOT better. Slightly less is OK. A lot less will take a long time to
return to full charge, leaving you low on charge in case of a double power
outage.

c) The bulk charge rate of the matched C/C - battery combo should be at
least at the next step up from the max station DC amperage draw. This is so
that you can run the station under normal AC supply situations at float
13.4 VDC without ever kicking into battery discharge because you turned
something on. You want to save your limited number of discharge cycles, and
related ventures into bulk charge rate, to actual events and stay away from
bulk charge induced heat, etc, unless it's actually a battery supply event.

d) In the flooded cell case, the normal C/C switching between 14.4 and 13.4
VDC, or approaching 11 VDC from a partly discharged battery must not be a
problem for any of your DC station equipment. There is a parallel
requirement for other battery/charger combinations that you must quantify.

e) Cost of a battery and multi-stage charger suitable for a) through d) in
your station environment and with bulk charge rate that covers your
station's draw may exceed what you want to pay to have a Field Day Class 1E
station at the ready 24/7.

Throwing a lawn tractor battery across your single voltage Astron supply
may appear to work, but will be very limited in its effectiveness because
after the first discharge it will never return to full charge. Some may
call this arrangement "working" and answer the question about float in the
positive, but it is in fact severely handicapped, and does not lend itself
to healthy batteries. As usual, the devil is in the details.

There is a nice entry level treatise that reads well at
https://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html


My first encounter with the rather complex issues of battery floating and
discharge were with AT&T Long Lines in the 60's, where we had such things
as 10,000 ampere 12 VDC supplies for many thousands of tube filaments, with
delta 440 AC driving huge motor generators in parallel, and strings of low
gravity 2' x 2' x 5' single cell batteries floating across the discharge
bus, and end cells to switch into the string to maintain 12 volts as the
batteries went into their normal discharge curves.

Carelessness in the battery room could get you burned, blinded, possibly
killed. Also having a major switching center go down because of batteries
in Washington, DC, could get one in a lot of trouble with various branches
of government. We had Bell Laboratories, Bell System Practices, and lots of
management in our ear all the time about how to do the batteries. Zero
tolerance for battery screw-ups, for any reason.

73 and good luck,

Guy K2AV

On Tuesday, July 12, 2016, Wes Stewart <wes_n7ws at triconet.org> wrote:

> I've given the reference already.
>
> I'm not saying I necessarily agree with it, I'm just the messenger.  I
> suppose that when I posted my first message I should have added, "According
> to the vendor, you cannot..."
>
> On 7/12/2016 6:39 AM, Clay Autery wrote:
>
>> I'd like to see the reference on that one, too.  As I EVENTUALLY will
>> add high Ah batts to run pretty much all my household electronics, et al.
>> Even if this is a true issue, no matter.  Will just have to engineer
>> around it.... 2x batts with power consumption fed "clock" and
>> auto-switching comes to mind as a 1st brainstorm.  :-)
>>
>