On 19 Nov 2005 12:03:33 -0800, wrote:

Greetings:
Yes, I think "Deep Cycle" or "Marine" type storage lead acid batteries
are what you are asking about. These batteries are not usualy intended
for starting, as mentioned before, although most can do so. They are
indeed better for constant current aplications.

---
Being voltage sources, I would have thought that they would be be
better suited to feed loads which relied on a constant-voltage,
variable current source.
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(But so are 'regular car' batteries!) However, the real difference is this:
They are not distroyed by deep discharge like automotive starting batteries are.
(Leave your headlights on all day a few times, and you'll soon be
buying a new battery. Just ask my wife! )

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Hogwash. If you grossly deplete the capacity of a lead-acid or
calcium-lead-acid battery by _any_ means, the battery will be
damaged. In order to keep that from happening, if your wife's
ignorance is the culprit, you need to train her up on the proper
operation of a motor vehicle.

That is, assuming you have a clue.
---

Thicker plates, along with a
few other minor tweeks, make them more RESISTANT to damage from deep
discharge. (NOT, totally indistructable!) The real difference, however,
is really one of degree... All the same 'rules' for one type apply to
the other. For example, leaving a storage battery of any kind in a
discharged condition for a long period of time is a killer. Keeping
either kind 'topped off' will drasticly improve life span. Discharge
RATE is also most important. Lower rates mean longer overall run time,
and less damage to battery. Also, there are so-called 'Dual Purpose'
types now being sold. Supposed to be good for starting, (Huge current
draw) AND for deep cycle (Deep discharge). Avoid these. Like anything
else, they are not really all that great at EITHER job. (Jack of all
trades, master of none)

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Got data?
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They are a compromise, and in some cases, they
are the EXACT same battery being sold by same company, but with a
different lable! (And warranty, usually)

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Your point being...?
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As for using HAM or similiar type mobile gear with a nominal 12 volt
battery, no problems. All modern gear is designed to be able to work
with the engine OFF, and anyways, a fully charged lead acid battery
dosen't actually measure out at 12 volts. Try this: Get a digital volt
meter, check a 12 volt battery that has a good level of charge still in
it. You will find that it more likely will measure 12.7 or so,
unloaded. Possibly more. (Depends on many variables, like state of
charge, age, temp, ect) Your 13.8 volt gear will never notice the
difference, trust me.

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Trust you?

**** you.

So far you haven't demonstrated that you know what you're talking
about.
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The 13.8 volts was orginally mandated by the FCC,
back before PLL and microcontroler radios. Reason was, the older types
of radios were sensitive to voltage differences, and frequency and/or
power output could drift or vary out of specs.

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I guess you've never heard of a voltage regulator...
---

This is largely a moot
point now-a-days. Equipment had to be 'type certified" by the FCC at
13.8 volts, and all techs working on them had to use 13.8 volts when
making any adjustments or repairs, to avoid the above mentioned
problems. (Anyone remember "crystal ovens" ? They heated the 'rock' to
a specific temp, to avoid drift due to heat build-up) Who uses crystals
anymore? (OK, I know, we are still using them... But modern circuits
can compensate easily for temp rise/drift)

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Got an example?
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OK, having explained all that, as for the question of keeping your
stand by battery charged up and healthy, you could indeed do as
mentioned before by others, and that would be an easy way to go. Better
yet, buy a "Smart charger" to keep a float charge on the battery. It
won't over charge, and can be left on 24/7 without worry. (And will
cost pennies a month to run) However, here in the midwest, where I
live, power outtages are also common. (We get ice and snow storms as
well as tornadoes, thunderstorms, etc!) So MY solution was this: I had
a APC brand UPS in which the gel cell batteries died. I have found that
many people/companies throw these away when this happens, and they can
often be had for the hauling! (The new batteries would have cost me
over $150.00!)
What I did was this: My particular UPS used TWO batteries in series,
for 24 volts. It outputs a VERY clean sine waveform at 125 VAC. More to
the point, is ALSO keeps a trickle charge on the batteries. And being
"smart", it won't over charge. In a power outtage, this particular
model can keep any device plugged into it running without any hickup.
It's 'always on', no switching lag. So, you have two options here, one
is to power radios normally, via 125 vac, if you have that option, or
to use one or both backup batteries. You can either remove the backup
batteries from hookup to UPS, and use them stand alone, in parallel, or
single, one after the other. OR, just do as I do, and using a diode for
isolation, I use the 12 volts from one battery while it is still hooked
up to the UPS, while keeping the ability to have 125 vac available too.
(A heavy duty, fast recovery diode can do the job nicely, without much
forward drop, for free* (*Just canabalize an old computer power supply
for them. They come in "pairs" in a large transistor type package, are
VARY closely matched, being on one chip, and with the also included
heat sink, many can handle upwards of 20 to 40 amps EACH)
There you have it. Total standby solution. I bought TWO pairs of 12
volt deep cycle batteries, (About $60.00 each, for good ones) and,
along with the aforementioned UPS, I have 125 vac ready fulltime, as
well as plenty of 12 volt power. IF power outtage lasts a really long
time, I can recharge one set of batteries via automobile, if it comes
to that, while using the other set. Meantime, while NO power outtage
exists, one set is on the UPS, the other set is on 'smart chargers". I
also have 'regular' types of inverters, which use one battery, for
smaller tasks, like running a sawzall for cutting away downed tree
limbs. (These cheaper 'inverters' don't usally have a good sine
waveform, though) With 3 vehicles in the driveway, I have three more
batteries available for the inverter, and/or three more re-chargers.
Just be sure to run the engine from time to time. The inverter will
shut off before discharging battery too far.
(Our weather, and the remoteness of my location, has taught me valuable
lessons about being self reliant!)
One last thing: By re-cycling these UPS' rather than letting them go
into a landfill, you are helping the envioment. There are substances in
those devices, (And a lot of related gear too) that I'd rather NOT have
in my drinking water.

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Like what, for instance?
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Many locations reguard UPS' as hazardous waste,
even if old batteries have been removed.

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Really?

Why would that be true? That is, if the UPS dies and its batteries
are removed and it's sent to the landfill, what would be hazardous
about its disposal?
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(Take or send the old
batteries to a recycling station, or APC will accept them free, for
re-cycling, and/or proper disposal)
So you can help yourself, while helping everyone else too.
If you, or anyone reading this, has specific questions on this subject,
feel free to email, I'll try to help.

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Your "help" will certainly be self-serving and email will only lock
the unsuspecting ignoranti into your line of reasoning without
exposing them to the truth.

Any questions should be sent to the newsgroup, where they can be
examined and debated, as opposed to being sent directly to you,
where you can use subterfuge to try to bend the querants' wills to
your own.


--
John Fields
Professional Circuit Designer