"Pete C" wrote in message
ups.com...
On Jul 25, 10:46 am, wrote:

Thanks for info. I started to read your technical section and the
lights went out but will do more studying later. I've always liked the
idea of a meter that showed amps in/amps out but never was able to
figure out a method of outwitting the time necessary for the chemical
changes to take place during the charging phase.

Hi,

Just google for 'battery conductance tester', that's basically what it
is.

Whether it's worth having or not IMHO depends largely on whether the
prospective user knows little about electrics and isn't able to use a
hydrometer.

cheers,
Pete.



Pete, do you propose using a hydrometer everytime you want to know your
state of charge? This could be a couple of times each day, or more.

On Jul 25, 2:37 pm, "KLC Lewis" wrote:
"Pete C" wrote in message

Pete, do you propose using a hydrometer everytime you want to know your
state of charge? This could be a couple of times each day, or more.

Hi,

For those who know a bit about electrics and can use a hydrometer I
would propose:

Do an energy budget/audit.

Size the battery bank for 40% DoD (depth of discharge) on a normal
days/period of use

Use the hydro to verify the above a few times as well as check the
batts are getting fully charged.

Use the hydro to check a few times that an exceptional days/period of
demand doesn't draw the batts below 80% DoD

Comments???

cheers,
Pete.

"Pete C" wrote in message
oups.com...
On Jul 25, 2:37 pm, "KLC Lewis" wrote:
"Pete C" wrote in message

Pete, do you propose using a hydrometer everytime you want to know your
state of charge? This could be a couple of times each day, or more.

Hi,

For those who know a bit about electrics and can use a hydrometer I
would propose:

Do an energy budget/audit.

Size the battery bank for 40% DoD (depth of discharge) on a normal
days/period of use

Use the hydro to verify the above a few times as well as check the
batts are getting fully charged.

Use the hydro to check a few times that an exceptional days/period of
demand doesn't draw the batts below 80% DoD

Comments???

cheers,
Pete.




My own energy needs are quite modest. Nav instruments, VHF, stereo, running
and anchor lights, computer (laptop), the occasional cabin light for short
periods (converting to led units). No refer, no power windlass. Of course, I
do need to be able to start-up the iron genny from time to time.

My battery bank is 4 new-this-seasonTrojan T-105's and a 40 amp smart
charger for dockside use. 2 US32 solar panels rated at 64 watts. Voltmeter
always reads "top of the green" at 13 volts after dockside charging, bottom
middle of the green after sailing for a day and anchoring out overnight with
the anchor light lit. Engine starts right up like it has a fully-charged
battery when weighing anchor in the morning. But translating this to "how
much power do I have left?" leaves me paranoid.

Hi,

If you're able to use a hydrometer, this FAQ tells how to relate
battery 'SG' to state of charge:

http://www.batteryfaq.org/
http://jgdarden.com/batteryfaq/carfaq4.htm
http://jgdarden.com/batteryfaq/carfaq4.htm#soc

Bear in mind 'state of charge' isn't a percentage of the battery's
*rated* capacity, as they lose capacity as they get old or sulphated.

State of charge is a percentage of the *actual* capacity of the
battery, taking into account it's age and condition.

To work out the actual capacity you need to compare the drop in state
of charge to a known amount of charge used.

So if drawing 1 amp for 10 hours (10 'amp hours') from a battery makes
it's state of charge drop by 25%, the actual capacity is about 40 amp
hours when it's fully charged.

If the above battery then reads a 75% state of charge, then
approximately 30 amp hours of charge are available until it's
completely flat. (Though of course it should be recharged when the
state of charge is around 50% or less)

If the above is a bit too then try and get someone to explain it to
you in person as it's a little difficult to do in a short posting.

hope this helps,
Pete.

On Wed, 25 Jul 2007 10:35:06 -0700, Pete C
wrote:

Hi,

If you're able to use a hydrometer, this FAQ tells how to relate
battery 'SG' to state of charge:

http://www.batteryfaq.org/
http://jgdarden.com/batteryfaq/carfaq4.htm
http://jgdarden.com/batteryfaq/carfaq4.htm#soc

Bear in mind 'state of charge' isn't a percentage of the battery's
*rated* capacity, as they lose capacity as they get old or sulphated.

State of charge is a percentage of the *actual* capacity of the
battery, taking into account it's age and condition.

To work out the actual capacity you need to compare the drop in state
of charge to a known amount of charge used.

So if drawing 1 amp for 10 hours (10 'amp hours') from a battery makes
it's state of charge drop by 25%, the actual capacity is about 40 amp
hours when it's fully charged.

If the above battery then reads a 75% state of charge, then
approximately 30 amp hours of charge are available until it's
completely flat. (Though of course it should be recharged when the
state of charge is around 50% or less)

If the above is a bit too then try and get someone to explain it to
you in person as it's a little difficult to do in a short posting.

hope this helps,
Pete.
Sorry Pete I cannot relate to the above, it is a far too simplistic.
Here in the UK and I feel also in the US battery capacity is normally
quoted at a 20hour rate.
Therefore in the example offered above - 1A for 10hrs giving a 25%
drop in "State of Charge" the actual original battery capacity would
have been more like 35AH given a Peukert of 1.25

Ok I realise that you used the term "about" but we are talking major %
differences here.

To put the test another way are you saying that if the load had been
100ma for 100hours = 10amp hours your conclusions would have been the
same?
I would then suggest the battery's max capacity would have been 22Ah.

--
Richard

Nb "Pound Eater" Parkend G+S
"Governments are like Nappies, they should be changed often."
(For the same reason)

On Jul 26, 7:51 am, Electricky Dicky wrote:

Sorry Pete I cannot relate to the above, it is a far too simplistic.
Here in the UK and I feel also in the US battery capacity is normally
quoted at a 20hour rate.
Therefore in the example offered above - 1A for 10hrs giving a 25%
drop in "State of Charge" the actual original battery capacity would
have been more like 35AH given a Peukert of 1.25

Ok I realise that you used the term "about" but we are talking major %
differences here.

Very good point, to get a good comparison of actual to rated capacity
you'd need to discharge at a 20hr rate.

So for a 40Ah battery this would be 40(Ah)/20(hours) = 2 amps.

cheers,
Pete.

On Wed, 25 Jul 2007 11:04:43 -0500, "KLC Lewis"
wrote:


"Pete C" wrote in message
roups.com...
On Jul 25, 2:37 pm, "KLC Lewis" wrote:
"Pete C" wrote in message

Pete, do you propose using a hydrometer everytime you want to know your
state of charge? This could be a couple of times each day, or more.

Hi,

For those who know a bit about electrics and can use a hydrometer I
would propose:

Do an energy budget/audit.

Size the battery bank for 40% DoD (depth of discharge) on a normal
days/period of use

Use the hydro to verify the above a few times as well as check the
batts are getting fully charged.

Use the hydro to check a few times that an exceptional days/period of
demand doesn't draw the batts below 80% DoD

Comments???

cheers,
Pete.




My own energy needs are quite modest. Nav instruments, VHF, stereo, running
and anchor lights, computer (laptop), the occasional cabin light for short
periods (converting to led units). No refer, no power windlass. Of course, I
do need to be able to start-up the iron genny from time to time.

My battery bank is 4 new-this-seasonTrojan T-105's and a 40 amp smart
charger for dockside use. 2 US32 solar panels rated at 64 watts. Voltmeter
always reads "top of the green" at 13 volts after dockside charging, bottom
middle of the green after sailing for a day and anchoring out overnight with
the anchor light lit. Engine starts right up like it has a fully-charged
battery when weighing anchor in the morning. But translating this to "how
much power do I have left?" leaves me paranoid.

And you have 450AH available ;-) I have customers who live on their
boat with less than that!
Paranoid is a bit OTT but aware is sensible.

--
Richard

Nb "Pound Eater" Parkend G+S
"Governments are like Nappies, they should be changed often."
(For the same reason)

On Wed, 25 Jul 2007 08:17:40 -0700, Pete C
wrote:

On Jul 25, 2:37 pm, "KLC Lewis" wrote:
"Pete C" wrote in message

Pete, do you propose using a hydrometer everytime you want to know your
state of charge? This could be a couple of times each day, or more.

Hi,

For those who know a bit about electrics and can use a hydrometer I
would propose:

Do an energy budget/audit.

Size the battery bank for 40% DoD (depth of discharge) on a normal
days/period of use

Use the hydro to verify the above a few times as well as check the
batts are getting fully charged.

Use the hydro to check a few times that an exceptional days/period of
demand doesn't draw the batts below 80% DoD

Comments???

99% of my customers would not know what a hydrometer was
99% of my customers have no idea what their audit is
70% do not care
30% want to be able to look at something to tell them whether to
charge or not

cheers,
Pete.


--
Richard

Nb "Pound Eater" Parkend G+S
"Governments are like Nappies, they should be changed often."
(For the same reason)

On Jul 26, 7:58 am, Electricky Dicky wrote:
On Wed, 25 Jul 2007 08:17:40 -0700, Pete C
wrote:

For those who know a bit about electrics and can use a hydrometer I
would propose

[stuff snipped....]

99% of my customers would not know what a hydrometer was
99% of my customers have no idea what their audit is
70% do not care
30% want to be able to look at something to tell them whether to
charge or not

Exactly! E-X-A-C-T-L-Y!

If they knew a bit about electrics and could use a hydrometer, they
wouldn't be your customer, as they woundn't need professional help,
would they?

cheers,
Pete.

"Pete C" wrote in message
ps.com...
On Jul 26, 7:58 am, Electricky Dicky wrote:
On Wed, 25 Jul 2007 08:17:40 -0700, Pete C
wrote:

For those who know a bit about electrics and can use a hydrometer I
would propose

[stuff snipped....]

99% of my customers would not know what a hydrometer was
99% of my customers have no idea what their audit is
70% do not care
30% want to be able to look at something to tell them whether to
charge or not

Exactly! E-X-A-C-T-L-Y!

If they knew a bit about electrics and could use a hydrometer, they
wouldn't be your customer, as they woundn't need professional help,
would they?

cheers,
Pete.


It takes me about 10 - 15 minutes to check all of the cells in my bank. This
is with the boat sitting calmly at the dock. I would much prefer not to have
to open those cells with the boat in motion, sloshing battery acid around.
If a meter will give me reasonably accurate information, which I can verify
from time to time with a physical check of the electrolyte when it can be
done safely, so much the better.