connecting batteries in parallel or series, myth and theory

[daestrom]

I am probably making a big mistake jumping into the
line of fire, between you two, but it appears to me that
both of you have valid points. And both of you are
providing information to support the idea that Golf Cart
batteries can be useful, when the charging and
discharging characteristics (as provided by their
makers, for their intended purpose) are taken in
consideration and adapted to how they would apply
to the new purpose.

EV use, (and a Golf Cart is an EV) would certainly
involve heavy discharge rates into a motor, the GC
battery would have been designed with that in mind.
It is my understanding that batteries are more open
to degradation during the charging process than the
discharging process.

Neon John's post speaks to the hardiness of the
GC battery during discharge, and should be taken
to indicate no problem with the occasional
discharge below a 60% design level. Fortunately
a home running on wind or PV power, has many
smaller loads/demands instead of a single large
motor to feed.

N9WOS's post points to the need for sufficient
capacity so that the slower charging rate from
alternative sources, are practical. The less
aggressive charging should indeed extend the
operating life of the battery bank, ( with proper
maintenance including a schedule of
"maintenance overcharging").

Golf Cart batteries may be less efficient or
practical than a number of newer alternatives
but they have a long history of availability and
low cost for less demanding homepower use.

If you are thinking of powering John Edward's
house, you should probably give the Golf Cart
batteries a pass.

I think another key point is how often the batteries are fully recharged as
well. In Neon John's use of a golf cart, I would bet that he recharges the
thing every day or so depending on how much he uses it. Recharging from
grid power through a dedicated charger is pretty straight forward and not at
all hard to get a full charge overnight.

But a solar installation may not have quite that luxury. A partial
discharge each day for a couple of days, followed by only a partial recharge
might be more problematic. A couple of cloudy days, and although the
batteries are not fully discharged, the chances are that one sunny day will
*not* put back all the charge.

Seems that type of duty is a lot harder on a battery than even 'typical'
golf cart usage.

Unless of course you want to buy a lot more solar cells so you *can*
recharge the battery in one sunny day ;-)

daestrom

 

[daestrom]

In alt.engineering.electrical daestrom
<daestrom@no_spam_heretwcny.rr.com> wrote:

Commercial UPSes are put in place usually to prevent _any_ downtime
where even a 5 minute outage every 5 years means a major loss of
money (directly) and/or reputation (which translates to money).

Homepower systems being down can be inconvenient ... as inconvenient
as the utility going out is to the typical grid powered home. You
fix up the system (for example, take a bad string offline and reset
the breakers for the others, and cut the loads down a bit).

I'm sure people vary in how much they consider it inconvenient to
have to go make an adjustment to their battery system. If I have to
swap out a GC battery which I can pick up, vs. have to wait until I
can swap out a 250 lb monster cell and have zero power in the interim,
well ... different people have different needs.

Now *THAT* is a good argument for using parallel battery strings. But keep
in mind what you are effectively saying is, "Although parallel GC batteries
may not be the best solution, some of the benefits of using them outweigh
the shorter life." You're just weighing how often you want to fuss with
swapping out a dead battery and how often your power goes out versus how
much money you want to spend replacing batteries.

But FWIW, when one "250 lb monster cell" goes bad, when you have just a
single series string you simply jumper out the cell and reset the voltage
settings. Running 2.1 V lower is not a big deal when you're talking +250VDC
(a slight reduction in capacity) and power is restored. Of course, if you
lose several cells and have to jumper them out, it's time to start thinking
of a new battery.

Grid-tie inverters I have seen need the grid present and online to
run.
When the grid goes down, they go down. These are not homepower
inverters.

Yes, but I was trying to point out that inverters are not limited to 48vDC
input. That was all.

daestrom

 

[[email protected]]

You are stating that you were meaning to say irrelevant of 1 to 10 of
charging that if you don't keep them fully charged, then they will die.

I wrote exactly what I meant, but I will concede that I'm not willing
to work at writing clearly enough for you.

You change the subject back to grid tie systems again!!!!

No, you're misinterpreting again. I'm off-grid. Surely it can't be
news to you that some people have charging sources that aren't as
time-limited as you're used to.

What does that have to do with the conversation?

In this case, debating hypotheticals is only useful if they're at
least somewhat practical. It seems that you have *the* solution in
search of a specific problem that you've never actually heard of.

You are most likely just trying to mess with peoples minds.

Good idea! A word of advice - if someone offers to sell you cheap pot,
don't bite, because you won't be able to cook a damned thing in it! Oh
crap, now you're going to accuse me of suggesting that people bite
each other.

I am not going to carry on this stupidity any longer.

Good. Chill dude.

PS. No ice cubes!

Wayne

 

[[email protected]]

The only thing the article points out as problematic in shallow discharge
situations is paralleling two completely different lead acid battery
designs. High rate/low rate, AGM/flooded/gel, starting/deep cycle/marine.
And paralleling different battery technologies. Lead acid/nicad/NMH/Li
Ion./nickel iron/or the like. Nothing more, nothing less.

Plus, no article can trump practical experience, which is that
parallel strings of like batteries are routine and generally
successful. I visited a setup recently with 6 (IIRC) parallel strings
of GC batteries. About the last arrangement I'd ever recommend to
anyone, and they had been replaced recently. But the previous ones
lasted 5 years, which was reasonable considering their low cost and
hard life.

Wayne

 

[[email protected]]

Hmm. Perhaps you should have a look at wayne's assertion that
increasing the daily load will reduce line losses.

Perhaps you should show a quote to support that contention, which is
exactly the type of BS that got you a free parody site. Regardless,
how can anything that others write ever help mitigate your posting
definitive proof that you don't know Ohms from apple butter?

Wayne

 

[daestrom]

I think that they design and build their systems to meet their or
their corporate customer's needs, in line with what they may be
willing to pay. In the case of submarines it would be more
whatever is needed, for national defense, regardless of the cost.
In any case, they can pretty much afford any battery they can
dream up, the average DIY homepower, doesn't have that luxury.

My point was that because of that last factor they are able to use
materials and equipment that would never be available to anyone
designing and constructing their own Homepower solutions.

"Station batteries" are a widely available technology. Single 2.1VDC cells
of a wide variety of A-H ratings are commercially available. Probably a
size for just about any homepower installation.

Also
that they can design for a prescribed maintenance environment,
that again includes resources beyond that likely for the Homepower
enthusiast. (I have trouble getting the kid to mow the lawn, once
every blue moon; wouldn't want to consider the results of expecting
him to play Plant Engineer.)

True, maintaining batteries is more work than maintaining a grid-connect
electric meter. But this is true of *any* battery installation. Then it
becomes a question of how valuable your time is, playing Plant Engineer
versus buying new batteries every two or three years.

For the 430v commercial UPS you described "36 12v batteries
connected in series", are we to assume that they had a 430vDC
inverter, that provided a voltage and current capacity to run the
commercial installation? Do you think that if the commercial firm
could not afford that 430v DC inverter, they would have gone with
that design?

Obviously the customer considered the cost of the UPS against the costs of
losing power. Can't speak to that much as I'm not that customer.

We recently 'retired' a UPS at work because a) The cost of replacing the
battery every five years was getting kind of expensive (~$9,000) b) the
annual maintenance /repair was running rather high and c) the 'fragile' (and
costly to repair) computer systems it was protecting had been replaced with
cheaper, COTS PC-based computers. The loss of service had never been the
issue, but the cost of repairs to the 'fragile' computer system after a
power outage. With that risk eliminated, the cost of the UPS was no longer
justifiable.

Then there is the question of what is appropriate for the
scale of the project. Any significant commercial operation
will consume a great deal more energy than the average
wasteful American home; the successful Homepower setup
uses less power than the average wasteful American home.

The design requirements aren't at all the same.

So don't use a submarine battery for a homepower setup. I never actually
suggested that you should. I only pointed out that large commercial setups
of batteries have always opted for series strings of relatively higher
voltage instead of many parallel batteries at low voltage.

When unltra-reliability is an issue, commercial installations will use two
strings in parallel. They aren't paralleling the strings for added
capacity, they are concerned with *redundancy*.

Of course you don't need as many amp-hours as a commercial UPS operation.
But the basic principles are the same, correctly sized cells connected in
series to attain the desired working voltage. The TCO of such a setup is
lower than massively paralleled systems at low voltage. YMMV.

Still lead acid? Not some of the newer much more expensive
exotic batteries? They should want to gain the space savings
if nothing else. In anycase, I haven't seen any sub battery banks
available at my local government surplus auctions, and short of
that I will have to use what is available, and affordable.

I'm sure that small research subs and such use all sorts of exotic power
schemes. But your basic warship submarine sticks to what works.

And again, I never suggested that a submarine battery was the right battery
for a homepower installation. I pointed out that some of the largest
capacity battery systems in use do *not* go for multiple parallel strings.
So *they* (the ever infamous 'they') have figured out that if you want more
capacity, the best way to do it is with larger amp-hour rated cells, *not*
paralleling small cells together.

So you see the homepower guy, being able to afford
the products of Co-Generation contractors?

Just glancing around at random,
http://search.altenergystore.com/energy/rolls surrette
Prices seem to run about $1 / Ah with 10 year warranty. Some higher for odd
voltages, a couple lower.

For a 'golf cart' battery, the first hit I found was...
http://www.apexbattery.com/mk-8agc2-golf-cart-battery-6v-220ah-golf-cart-batteries-.html
Price is a bit over $1 / Ah with a 1 year warranty.

Of course this was just a five minute search. I'm sure a more detailed
search would be appropriate before jumping on any choice.

I think there are already postings and links posted, in this thread,
that bring your "Just about every commercial battery bank is strickly
a single string in series." statement into question. There is also
the fact that "battery banks" come in all sizes, to serve many
different power storage requirements. (While it seems to be my fate
to run into those who think this way You can't just pick the largest or
most extreme example you know anything about, and say all must
conform to that design.

True, some commercial installations will use two strings in parallel. But
they generally do that for redundancy and reliability. Not for increased
capacity. Different reason all together that probably doesn't apply to a
homepower installation.

daestrom
P.S. Despite our disagreements, it's nice to find someone that is polite
about disagreeing

 

[daestrom]

I have seen them in the field, they have two parallel battery
strings. They don't say it on the website, but that is the way they
are wired. That is why I posted the link to the picture. If you look
at where the battery + leads connect to the fuse block and the
negative leads to the - negative terminal block, then you will see
two wires going from each. One to each string.

Fair 'nuff. But as I said in another post, UPS designers typically use
*two* (and no more than two) strings in parallel because they are installing
a redundancy in case a cell opens up. It's a question of reliability, not
increased capacity.

I doubt any homepower installation is thinking about increased reliability
when they start thinking of paralleling batteries.

daestrom

 

[bw]

As a definition I would have to agree. Perhaps you would show us the
circuit where a single diode can change AC to DC.

Look up "half wave"

http://www.allaboutcircuits.com/vol_6/chpt_5/3.html
http://www.bapihvac.com/CatalogPDFs/I_App_Notes/Understanding_Full_and_Half_Wave.pdf

 

[Palindrome]

Then that definition is as faulty as other definitions from your
Telco oriented textbook answers.

In general, a diode is a rectifier, but here are other applications,
like current steering. Yes, it prevents reverse current flow, but it is
in a DC only application. Then there are 'Protection Diodes', that
attempt to outsmart fools who shouldn't be anywhere near electronics.
Diodes are used to drop a DC voltage, or provide a reference voltage,
both DC only applications. Then we get to LEDs, which are not typically
suitable for rectifiers. A Gunn diode turns DC into microwaves. Once
again, these are DC only application, and no rectification takes place.

The whole world isn't bands of 2 V telco batteries and refrigerator
sided 'Rectifiers' to float charge them.

AFAIK, the term "diode" pre-dates semiconductors by some considerable
period. The term was used to describe a valve (tube to our trans-pondean
friends) with a cathode and an anode (two in total, hence a diode).

Particular diode designs were designed as "rectifier diodes". That
terminology was continued when semiconductors came along, to give
"signal diodes" and "rectifier diodes". Eventually, by common usage, the
latter was shortened to "rectifier" and the former to "diode".

In general, a rectifier is a diode, not vice versa. Much like a human is
a primate but a primate is not necessarily human. The word "rectifier"
indicates that the design purpose of this particular diode is some form
of power conversion - not some form of signal processing. Not all diodes
are rectifiers by definition - because the definition of a rectifier is
that of being a diode designed or used for a particular, limited,
purpose - that of power conversion.

 

[krw]

AFAIK, the term "diode" pre-dates semiconductors by some considerable
period. The term was used to describe a valve (tube to our trans-pondean
friends) with a cathode and an anode (two in total, hence a diode).

Particular diode designs were designed as "rectifier diodes". That
terminology was continued when semiconductors came along, to give
"signal diodes" and "rectifier diodes". Eventually, by common usage, the
latter was shortened to "rectifier" and the former to "diode".

In general, a rectifier is a diode, not vice versa. Much like a human is
a primate but a primate is not necessarily human. The word "rectifier"
indicates that the design purpose of this particular diode is some form
of power conversion - not some form of signal processing. Not all diodes
are rectifiers by definition - because the definition of a rectifier is
that of being a diode designed or used for a particular, limited,
purpose - that of power conversion.

I'd say the opposite; A diode is a rectifier, but not verse-visa.
An LED, for instance, may not be used primarily as a rectifier but
it is one. OTOH, synchronous rectifiers are not made from diodes,
rather "higher order" semiconductors (e.g. FETs or SCRs).

 

[Palindrome]

I'd say the opposite; A diode is a rectifier, but not verse-visa.
An LED, for instance, may not be used primarily as a rectifier but
it is one. OTOH, synchronous rectifiers are not made from diodes,
rather "higher order" semiconductors (e.g. FETs or SCRs).

This is because you are defining all things that rectify as being
rectifiers. That isn't how a rectifier was defined. A rectifier was an
abbreviation of the term "rectifier diode". It was a particular type of
diode. All diodes rectify but not all diodes are rectifiers.

Language evolves. Your definition may easily become the norm. May have
already become the norm in certain specialisations. But a purist will
always look to the derivation of the word, rather than current usage,
when considering definitions.

 

[krw]

This is because you are defining all things that rectify as being
rectifiers. That isn't how a rectifier was defined. A rectifier was an
abbreviation of the term "rectifier diode". It was a particular type of
diode. All diodes rectify but not all diodes are rectifiers.

Ok, all diodes are rectifiers, so all diodes are "rectifier diodes".
;-)

A "rectifier" is something that rectifies.

Language evolves. Your definition may easily become the norm. May have
already become the norm in certain specialisations. But a purist will
always look to the derivation of the word, rather than current usage,
when considering definitions.

It *IS* the norm (and your argument doesn't convince me it's ever
been otherwise). ...at least has been since I've been around the
biz. OTOH, both descriptive and definitive dictionaries both have
their problems.

 

[m II]

This is because you are defining all things that rectify as being
rectifiers.

Did you mean "all things that rectify as being diodes" ?

That isn't how a rectifier was defined. A rectifier was an
abbreviation of the term "rectifier diode".
http://www.merriam-webster.com/dictionary/rectifier



All diodes rectify but not all diodes are rectifiers.

Did you mean "All diodes rectify but not all rectifiers are diodes" ?

http://www.askoxford.com/concise_oed/diode
http://www.merriam-webster.com/dictionary/diode



mike



Densa International©
'Think tanks cleaned cheap'

Due to the insane amount of spam and garbage,
I block all postings with a Gmail, Google Mail,
Google Groups or HOTMAIL address.
I also filter everything from a .cn server.

http://improve-usenet.org/

 

[bw]

Cool. Now apply that to a DC battery bank.

A direct example
http://homepage.ntlworld.com/wilf.james/nicads.htm

68000 hits on google for "half wave battery charger"
That is a fundamental application, and one I have used many times.
Direct connection with a wire. Many modern applications of an old circuit.
You probably have used them if you ever used an old automotive charger.

All chemical cells are DC by definition.
http://en.wikipedia.org/wiki/Rectifier
More examples
http://www.talkingelectronics.com/projects/BatteryCharger-12vSLA/BatteryCharger-12vSLA.html
A 1999 patent http://www.patentstorm.us/patents/5940280/description.html

 

[m II]

Using general purpose dictionaries for electronics makes about as
much sense, as going to Midas Muffler for heart bypass surgery.

There's ANOTHER place?





mike



Densa International©
'Think tanks cleaned cheap'

Due to the insane amount of spam and garbage,
I block all postings with a Gmail, Google Mail,
Google Groups or HOTMAIL address.
I also filter everything from a .cn server.

http://improve-usenet.org/

 

[Archimedes' Lever]

68000 hits on google for "half wave battery charger"

Most battery chargers of the shit quality, consumer automotive variety
are single diode, half-wave-rectified DC "ripple pumps" that "charge" the
battery with the peaks from the half wave rectified transformer output.
Very cheap, quite functional.

I still found myself replacing the diodes with quad rectifier packs for
a full wave ripple.

 

[Palindrome]

Have you ever seen, or even heard of an electrolytic rectifier? It
was one of the fist developed, to charge batteries from the AC line.
The term Valve was the first low grade vacuum tube rectifier. Then we
have the more exotic like thyratrons and Triacs when can adjust the
trigger voltage, to almost any conduction phase. there were copper
oxide rectifiers, mechanical rectifiers, like those used in a vibrator
power supply.. Today, we have synchronous rectifiers, using power FETS,
where the gates are driven for the proper half cycle. These are commonly
used where the Vf wastes too much power, and the lower Ron of the FET
reduces the wasted power, and waste heat.

Have you ever seen an Eimac 15R vacuum rectifier? It was developed
for the early airborne RADAR used in W.W.II. It, along with the 15E
triode generated the RF pulse for the transmitter section.

http://www.radiomuseum.org/tubes/tube_15r.html

there was an online data sheet for the 15E, but I can't find it right
now. It looked like the 15R, but had a pin out the side to connect the
grid.

The oldest electronics manuals I have all refer to rectifiers rather
than diodes. Some are form the days of spark transmitters, but they are
all on another computer that's not accessible on my home network,, right
now.

We appear to be in agreement, only not so.

All things that convert AC into DC are defined as rectifiers.

All electronic devices with two electrodes are defined as diodes.

Some diodes convert AC into DC and are thus rectifiers.

Some diodes (eg DIACs) do not convert AC into DC and are thus not
rectifiers.

Some rectifiers have more than two terminals (eg A three phase mercury
arc rectifier) and are thus not diodes.

As I wrote, "in general rectifiers are diodes". That quite clearly does
not claim that all rectifiers are diodes. They aren't.

Nor are all diodes rectifiers.

I really don't see the problem. You first count the electrodes - if
there aren't two, it cannot be a diode. If there are two, it can be a
rectifier (diode). But it may not be.

 

[Palindrome]

A DIAC, despite the name, is not a "diode", it is a
five-layer device that acts like a diode.

It has two electrodes - it is a diode.

Triode tubes also can be made to act like a diode, but
that doesn't make them diodes.

It has three electrodes - it is not a diode.

The number of leads is not indicative. Note that a
common SPST switch has two leads, and nobody calls that
a diode, even then it can act as one.

It has no electrodes - it is not a diode.

 

[krw]

It has two electrodes - it is a diode.

So does Floyd's switch but it is not a diode. A (semiconductor)
diode is a PN device. A DIAC is not a PN device.

It has three electrodes - it is not a diode.

True (and stated), however it *can* be a rectifier, which was the
point.

It has no electrodes - it is not a diode.

Ok, would you prefer a neon bulb as an example?

 

[Palindrome]

It has 5.

DIAC = DiIode for Alternating Current

The manufacturer calls it a diode:

http://www.st.com/stonline/products/literature/ds/7488/db3.pdf

Same as above?


You are counting leads as electrodes with the DIAC.

Nah, I am counting connection points to the device. They may, or may not
have leads at the connection point - many rectifiers (and many other
diodes ) do not.