Sorry about the corss-post

Two identical RV batteries. They have been unhooked from the RV
'converter' (smart trickle charger) for 5 days. Checking with a hydrometer
shows that all cells are 75% charged. (12 cells, two batteries). HOWEVER
one of the batteries reads 12.35 volts while the other reads 8.6 volts. Why
this discrepancy when the hydrometer readings are identical? Obviously, I
will replace the low voltage battery, but, I want to learn why the
hydrometer readings are in discrepancy with the voltage readings. BTW,
checked the voltmeter against my truck battery (everyday use). It reads
13.2 volts with the engine not running.

Thanks for all replies,

Ivan Vegvary

"Ivan Vegvary" wrote in message
news:N3Lhk.271$GI.248@trnddc05...
Sorry about the corss-post

Two identical RV batteries. They have been unhooked from the RV
'converter' (smart trickle charger) for 5 days. Checking with a
hydrometer
shows that all cells are 75% charged. (12 cells, two batteries). HOWEVER
one of the batteries reads 12.35 volts while the other reads 8.6 volts.
Why
this discrepancy when the hydrometer readings are identical? Obviously, I
will replace the low voltage battery, but, I want to learn why the
hydrometer readings are in discrepancy with the voltage readings. BTW,
checked the voltmeter against my truck battery (everyday use). It reads
13.2 volts with the engine not running.

Thanks for all replies,

Ivan Vegvary

hydrometer checks the density of the acid. it doesn't check how many cells
are actually working. you have some dead cells in the battery. you need to
replace it.

"Ivan Vegvary" wrote in
news:N3Lhk.271$GI.248@trnddc05:

Sorry about the corss-post

Two identical RV batteries. They have been unhooked from the RV
'converter' (smart trickle charger) for 5 days. Checking with a
hydrometer shows that all cells are 75% charged. (12 cells, two
batteries). HOWEVER one of the batteries reads 12.35 volts while the
other reads 8.6 volts. Why this discrepancy when the hydrometer
readings are identical? Obviously, I will replace the low voltage
battery, but, I want to learn why the hydrometer readings are in
discrepancy with the voltage readings. BTW, checked the voltmeter
against my truck battery (everyday use). It reads 13.2 volts with the
engine not running.

Thanks for all replies,

Ivan Vegvary



That sounds like you've got a dead cell in the lower-voltage battery.

If these are Deep Cycle batteries, it's time to replace them both: DCBs
need to be paired (ie. both from the same lot) for best results.

DCBs, BTW, normaly do not get charged to 13.8V but to ~12.5V max.

On Wed, 23 Jul 2008 14:54:27 -0800, "SteveB" toquerville@zionvistas
wrote:


"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many cells
are actually working. you have some dead cells in the battery. you need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and it
was one of the best things I ever did on my MH. Costs the same, and will
give you many more hours of boondocking battery power. Made an incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway, so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

Definitely the best solution, guys. Paralling battery cells should
only be the method of last resort.
** Posted from http://www.teranews.com **

"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many cells
are actually working. you have some dead cells in the battery. you need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and it
was one of the best things I ever did on my MH. Costs the same, and will
give you many more hours of boondocking battery power. Made an incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway, so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

On Wed, 23 Jul 2008 16:25:26 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 14:54:27 -0800, "SteveB" toquerville@zionvistas
wrote:


"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many
cells
are actually working. you have some dead cells in the battery. you
need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and
it
was one of the best things I ever did on my MH. Costs the same, and
will
give you many more hours of boondocking battery power. Made an
incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway, so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

Definitely the best solution, guys. Paralling battery cells should
only be the method of last resort.
** Posted from http://www.teranews.com **

After reading these posts I went hunting for a web page I had read which
explained a certain 'effect' which gave parallel batteries more capacity
than serial. I didn't find it though. However I did find this one which
was pretty good at explaining the differences. They do mention parallel
having more capacity, all things being equal. Anyway choosing parallel or
serial would depends on different factors, which they discuss.

http://sierranevadaairstreams.org/ow...ry-config.html

Maybe you guys got better results with serial because the battery
technology
was better than the batteries you replaced. Just a thought.

Wayne D.

On Wed, 23 Jul 2008 18:42:13 -0500, Wayne
wrote:

On Wed, 23 Jul 2008 16:25:26 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 14:54:27 -0800, "SteveB" toquerville@zionvistas
wrote:


"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many
cells
are actually working. you have some dead cells in the battery. you
need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and
it
was one of the best things I ever did on my MH. Costs the same, and
will
give you many more hours of boondocking battery power. Made an
incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway, so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

Definitely the best solution, guys. Paralling battery cells should
only be the method of last resort.
** Posted from http://www.teranews.com **

After reading these posts I went hunting for a web page I had read which
explained a certain 'effect' which gave parallel batteries more capacity
than serial. I didn't find it though. However I did find this one which
was pretty good at explaining the differences. They do mention parallel
having more capacity, all things being equal. Anyway choosing parallel or
serial would depends on different factors, which they discuss.

http://sierranevadaairstreams.org/ow...ry-config.html

Maybe you guys got better results with serial because the battery
technology
was better than the batteries you replaced. Just a thought.

Wayne D.
Nope. I'll educate you if you are teachable.
tho batteries of THE SAME CAPACITY in parallel add their capacities
together. The voltage stays the same.

Tho batteries in series, the capacity stays the same, and the voltage
adds.
That's the simple explanation.

However, two batteries in parallel not only have voltage and capacity,
they have resistance and a few other esoteric qualities.
If batteries that are not matched are connected i parrallel, they can
FIGHT each other, and both capacity and lifespan can be severely
diminished. If their resistances are different, one gets more charge
than the other, and one provides more power than the other. Their
charge levels become more sisparate with time and charge cycles.

Now, take 2 batteries od half the voltage, and double the capacity,
which are roughly the same size as those you had connected in
parallel, and connect them in series.
Whatever current flows through one CELL of that combined battery pack
flows through all the rest. In both directions. All cells reach very
close to the same level of discharge - and take the same level of
charge. No fighting between shared current paths.

Also, six volt batteries of 400 ah capacity, for example, are MUCH
more sturdily built, on the whole, than 12 volt batteries of 200 ah
capacity. The plates and intercell connectors are, by nececity and
design, more robust - so they last longer.

When you connect 2 batteries of 3 cells each together, you still have
a single battery - of 6 cells, in a split case.
When you put 2 batteries of 6 cells together in parallel you still
have 2 batteries of 6 cells each.

The only battery technology that works RELATIVELY well with
parallelled cells is lithium iodide or lithium polymer. And they
require an intelligent charging controller.
** Posted from http://www.teranews.com **

On Wed, 23 Jul 2008 21:37:27 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 18:42:13 -0500, Wayne
wrote:

On Wed, 23 Jul 2008 16:25:26 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 14:54:27 -0800, "SteveB" toquerville@zionvistas
wrote:


"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many
cells
are actually working. you have some dead cells in the battery. you
need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and
it
was one of the best things I ever did on my MH. Costs the same, and
will
give you many more hours of boondocking battery power. Made an
incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway,
so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

Definitely the best solution, guys. Paralling battery cells should
only be the method of last resort.
** Posted from http://www.teranews.com **

After reading these posts I went hunting for a web page I had read which
explained a certain 'effect' which gave parallel batteries more capacity
than serial. I didn't find it though. However I did find this one which
was pretty good at explaining the differences. They do mention parallel
having more capacity, all things being equal. Anyway choosing parallel
or
serial would depends on different factors, which they discuss.

http://sierranevadaairstreams.org/ow...ry-config.html

Maybe you guys got better results with serial because the battery
technology
was better than the batteries you replaced. Just a thought.

Wayne D.
Nope. I'll educate you if you are teachable.

I did expect to be flamed, I didn't expect to be insulted.

tho batteries of THE SAME CAPACITY in parallel add their capacities
together. The voltage stays the same.

Not entirely true. The capacity in parallel is 2.14 times, not 2 times.
It's based on the Peukert effect.
See http://happytrailsmc.org/peukert.html and scroll down to
Implications for increasing the RV battery bank


Tho batteries in series, the capacity stays the same, and the voltage
adds.
That's the simple explanation.

Agreed.


However, two batteries in parallel not only have voltage and capacity,
they have resistance and a few other esoteric qualities.
If batteries that are not matched are connected i parrallel, they can
FIGHT each other, and both capacity and lifespan can be severely
diminished. If their resistances are different, one gets more charge
than the other, and one provides more power than the other. Their
charge levels become more sisparate with time and charge cycles.

Sounds resonable.
I'm assuming both batteries would be bought at the same time and
of the same manufacturer/model. That should reduce the mismatch.


Now, take 2 batteries od half the voltage, and double the capacity,
which are roughly the same size as those you had connected in
parallel, and connect them in series.
Whatever current flows through one CELL of that combined battery pack
flows through all the rest. In both directions. All cells reach very
close to the same level of discharge - and take the same level of
charge. No fighting between shared current paths.

Also, six volt batteries of 400 ah capacity, for example, are MUCH
more sturdily built, on the whole, than 12 volt batteries of 200 ah
capacity. The plates and intercell connectors are, by nececity and
design, more robust - so they last longer.

Agreed.


When you connect 2 batteries of 3 cells each together, you still have
a single battery - of 6 cells, in a split case.
When you put 2 batteries of 6 cells together in parallel you still
have 2 batteries of 6 cells each.

The only battery technology that works RELATIVELY well with
parallelled cells is lithium iodide or lithium polymer. And they
require an intelligent charging controller.
** Posted from http://www.teranews.com **

A lot of what you say was brought up in the original URL that I posted.
They took an unbiased view of the comparisons and left it up to
the reader to decided what is best for their application.

Wayne D.

On Thu, 24 Jul 2008 16:21:48 -0500, Wayne
wrote:

On Wed, 23 Jul 2008 21:37:27 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 18:42:13 -0500, Wayne
wrote:

On Wed, 23 Jul 2008 16:25:26 -0500, clare at snyder dot ontario dot
canada wrote:

On Wed, 23 Jul 2008 14:54:27 -0800, "SteveB" toquerville@zionvistas
wrote:


"charlie" wrote

hydrometer checks the density of the acid. it doesn't check how many
cells
are actually working. you have some dead cells in the battery. you
need to
replace it

PLEASE check out replacing with two 6v. batteries. I did on mine, and
it
was one of the best things I ever did on my MH. Costs the same, and
will
give you many more hours of boondocking battery power. Made an
incredible
difference in mine, but my 12 v.'s were ready to take a dump anyway,
so
going to the stupefying performance of the 2/6v. setup was light years
ahead. Don't take my word for it, ask around.

Steve

Definitely the best solution, guys. Paralling battery cells should
only be the method of last resort.
** Posted from http://www.teranews.com **

After reading these posts I went hunting for a web page I had read which
explained a certain 'effect' which gave parallel batteries more capacity
than serial. I didn't find it though. However I did find this one which
was pretty good at explaining the differences. They do mention parallel
having more capacity, all things being equal. Anyway choosing parallel
or
serial would depends on different factors, which they discuss.

http://sierranevadaairstreams.org/ow...ry-config.html

Maybe you guys got better results with serial because the battery
technology
was better than the batteries you replaced. Just a thought.

Wayne D.
Nope. I'll educate you if you are teachable.

I did expect to be flamed, I didn't expect to be insulted.

No insult intended.
Just that I've been a teacher in a past life -
Those who choose not to read/listen are unteachable.
Those who are intelectually challenged, yet wish to learn are
teachable.

tho batteries of THE SAME CAPACITY in parallel add their capacities
together. The voltage stays the same.

Not entirely true. The capacity in parallel is 2.14 times, not 2 times.
It's based on the Peukert effect.
See http://happytrailsmc.org/peukert.html and scroll down to
Implications for increasing the RV battery bank


Tho batteries in series, the capacity stays the same, and the voltage
adds.
That's the simple explanation.

Agreed.


However, two batteries in parallel not only have voltage and capacity,
they have resistance and a few other esoteric qualities.
If batteries that are not matched are connected i parrallel, they can
FIGHT each other, and both capacity and lifespan can be severely
diminished. If their resistances are different, one gets more charge
than the other, and one provides more power than the other. Their
charge levels become more sisparate with time and charge cycles.

Sounds resonable.
I'm assuming both batteries would be bought at the same time and
of the same manufacturer/model. That should reduce the mismatch.


Now, take 2 batteries od half the voltage, and double the capacity,
which are roughly the same size as those you had connected in
parallel, and connect them in series.
Whatever current flows through one CELL of that combined battery pack
flows through all the rest. In both directions. All cells reach very
close to the same level of discharge - and take the same level of
charge. No fighting between shared current paths.

Also, six volt batteries of 400 ah capacity, for example, are MUCH
more sturdily built, on the whole, than 12 volt batteries of 200 ah
capacity. The plates and intercell connectors are, by nececity and
design, more robust - so they last longer.

Agreed.


When you connect 2 batteries of 3 cells each together, you still have
a single battery - of 6 cells, in a split case.
When you put 2 batteries of 6 cells together in parallel you still
have 2 batteries of 6 cells each.

The only battery technology that works RELATIVELY well with
parallelled cells is lithium iodide or lithium polymer. And they
require an intelligent charging controller.
** Posted from http://www.teranews.com **

A lot of what you say was brought up in the original URL that I posted.
They took an unbiased view of the comparisons and left it up to
the reader to decided what is best for their application.

Wayne D.

** Posted from http://www.teranews.com **