battery life

[Paul Feltz]

Does anyone have a diagram of a meter that can be used to determining
the quality of the battery 12volt. Paul

[Mark Zivley]

Are you interested in the current charge state of the battery or it's
ability to provide power for the duration of the day?

For the charge state you simply need to use a voltmeter. 12.5 to
perhaps 13 volts would be ok. On charge the battery should be getting
13.5 to 13.8 volts.

If you want to test your battery's capacity you need to connect the
battery directly to a large resistor and monitor the voltage on the
battery for a couple hours. A 10 ohm, 25 watt resistor will work and by
using a 10 ohm resistor it's easy to compute what the current is by
looking at the voltmeter. 12 / 10 = 1.2 Amps. Be careful, this
resistor will be hot! The standard "gel cell" should stay above 12
volts for several hours if it's "good". My two cents anyway.

Mark

Paul Feltz wrote:
> Does anyone have a diagram of a meter that can be used to determining
> the quality of the battery 12volt. Paul

[Eric Greenwell]

Mark Zivley wrote:
> Are you interested in the current charge state of the battery or it's
> ability to provide power for the duration of the day?
>
> For the charge state you simply need to use a voltmeter. 12.5 to
> perhaps 13 volts would be ok. On charge the battery should be getting
> 13.5 to 13.8 volts.

To elaborate a little on what Mark mentioned: This voltage would be
after it's fully charged. With a "good" charger, the voltage should be
bit higher, about 14.4 to 14.8, before it drops back to 13.5 or so when
charging is complete.

>
> If you want to test your battery's capacity you need to connect the
> battery directly to a large resistor and monitor the voltage on the
> battery for a couple hours. A 10 ohm, 25 watt resistor will work and by
> using a 10 ohm resistor it's easy to compute what the current is by
> looking at the voltmeter. 12 / 10 = 1.2 Amps. Be careful, this
> resistor will be hot! The standard "gel cell" should stay above 12
> volts for several hours if it's "good". My two cents anyway.

A good technique, but for the usual 7 AH battery, I'd use a 25 ohm, 10
watt resistor instead, as the load would be closer to the typical
current draw in a glider. A fresh battery should stay above 11 volts for
about 13-14 hours. Be sure to charge the battery at the end of the test,
as it will degrade more rapidly if it sits around uncharged.

Your glider's equipment might not function as low as 11 volts, but the
test does give you an idea of how good the battery is compared to a new one.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Malcolm Austin]

And to elaborate a bit on both Mark's and Eric's notes.

The modelling fraternity often completes these type of tests on their
battery packs,
you may find a suitable discharge unit available from their suppliers? (I
have one from
years ago here in the UK)

It is good to create a graph of the results of each battery pack over a
typical
life span. You will quickly see then if the capacity is changing and how
quickly.

Remember, over charging is often the killer for all batteries.

Malcolm...

"Eric Greenwell" > wrote in message
...
> Mark Zivley wrote:
>> Are you interested in the current charge state of the battery or it's
>> ability to provide power for the duration of the day?
>>
>> For the charge state you simply need to use a voltmeter. 12.5 to perhaps
>> 13 volts would be ok. On charge the battery should be getting 13.5 to
>> 13.8 volts.
>
> To elaborate a little on what Mark mentioned: This voltage would be after
> it's fully charged. With a "good" charger, the voltage should be bit
> higher, about 14.4 to 14.8, before it drops back to 13.5 or so when
> charging is complete.
>
>>
>> If you want to test your battery's capacity you need to connect the
>> battery directly to a large resistor and monitor the voltage on the
>> battery for a couple hours. A 10 ohm, 25 watt resistor will work and by
>> using a 10 ohm resistor it's easy to compute what the current is by
>> looking at the voltmeter. 12 / 10 = 1.2 Amps. Be careful, this resistor
>> will be hot! The standard "gel cell" should stay above 12 volts for
>> several hours if it's "good". My two cents anyway.
>
> A good technique, but for the usual 7 AH battery, I'd use a 25 ohm, 10
> watt resistor instead, as the load would be closer to the typical current
> draw in a glider. A fresh battery should stay above 11 volts for about
> 13-14 hours. Be sure to charge the battery at the end of the test, as it
> will degrade more rapidly if it sits around uncharged.
>
> Your glider's equipment might not function as low as 11 volts, but the
> test does give you an idea of how good the battery is compared to a new
> one.
>
> --
> Change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA

[Tim Newport-Peace]

X-no-archive: yes
In article >, Malcolm Austin
> writes
>And to elaborate a bit on both Mark's and Eric's notes.
>
>The modelling fraternity often completes these type of tests on their
>battery packs,
>you may find a suitable discharge unit available from their suppliers? (I
>have one from
>years ago here in the UK)
>
>It is good to create a graph of the results of each battery pack over a
>typical
>life span. You will quickly see then if the capacity is changing and how
>quickly.
>
>Remember, over charging is often the killer for all batteries.
>
>Malcolm...
>
>"Eric Greenwell" > wrote in message
...
>> Mark Zivley wrote:
>>> Are you interested in the current charge state of the battery or it's
>>> ability to provide power for the duration of the day?
>>>
>>> For the charge state you simply need to use a voltmeter. 12.5 to perhaps
>>> 13 volts would be ok. On charge the battery should be getting 13.5 to
>>> 13.8 volts.
>>
>> To elaborate a little on what Mark mentioned: This voltage would be after
>> it's fully charged. With a "good" charger, the voltage should be bit
>> higher, about 14.4 to 14.8, before it drops back to 13.5 or so when
>> charging is complete.
>>
>>>
>>> If you want to test your battery's capacity you need to connect the
>>> battery directly to a large resistor and monitor the voltage on the
>>> battery for a couple hours. A 10 ohm, 25 watt resistor will work and by
>>> using a 10 ohm resistor it's easy to compute what the current is by
>>> looking at the voltmeter. 12 / 10 = 1.2 Amps. Be careful, this resistor
>>> will be hot! The standard "gel cell" should stay above 12 volts for
>>> several hours if it's "good". My two cents anyway.
>>
>> A good technique, but for the usual 7 AH battery, I'd use a 25 ohm, 10
>> watt resistor instead, as the load would be closer to the typical current
>> draw in a glider. A fresh battery should stay above 11 volts for about
>> 13-14 hours. Be sure to charge the battery at the end of the test, as it
>> will degrade more rapidly if it sits around uncharged.
>>
>> Your glider's equipment might not function as low as 11 volts, but the
>> test does give you an idea of how good the battery is compared to a new
>> one.
>>
>> --
>> Change "netto" to "net" to email me directly
>>
>> Eric Greenwell
>> Washington State
>> USA
>
>
The is available an 'intelligent battery tester' that will quickly
measure battery capacity without the need to do a measured discharge.

Visit www.actmeters.com. The model I use is ACT-IBT, although the price
may put some people off (web site has prices in pounds and dollars).

Best regards,
Tim Newport-Peace

(No commection with ACT meters except as a user).

[Tim Ward]

"Tim Newport-Peace" ]> wrote in message
...
> X-no-archive: yes
> In article >, Malcolm Austin
> > writes
> >And to elaborate a bit on both Mark's and Eric's notes.
> >
> >The modelling fraternity often completes these type of tests on their
> >battery packs,
> >you may find a suitable discharge unit available from their suppliers? (I
> >have one from
> >years ago here in the UK)
> >
> >It is good to create a graph of the results of each battery pack over a
> >typical
> >life span. You will quickly see then if the capacity is changing and how
> >quickly.
> >
> >Remember, over charging is often the killer for all batteries.
> >
> >Malcolm...
> >
> >"Eric Greenwell" > wrote in message
> ...
> >> Mark Zivley wrote:
> >>> Are you interested in the current charge state of the battery or it's
> >>> ability to provide power for the duration of the day?
> >>>
> >>> For the charge state you simply need to use a voltmeter. 12.5 to
perhaps
> >>> 13 volts would be ok. On charge the battery should be getting 13.5 to
> >>> 13.8 volts.
> >>
> >> To elaborate a little on what Mark mentioned: This voltage would be
after
> >> it's fully charged. With a "good" charger, the voltage should be bit
> >> higher, about 14.4 to 14.8, before it drops back to 13.5 or so when
> >> charging is complete.
> >>
> >>>
> >>> If you want to test your battery's capacity you need to connect the
> >>> battery directly to a large resistor and monitor the voltage on the
> >>> battery for a couple hours. A 10 ohm, 25 watt resistor will work and
by
> >>> using a 10 ohm resistor it's easy to compute what the current is by
> >>> looking at the voltmeter. 12 / 10 = 1.2 Amps. Be careful, this
resistor
> >>> will be hot! The standard "gel cell" should stay above 12 volts for
> >>> several hours if it's "good". My two cents anyway.
> >>
> >> A good technique, but for the usual 7 AH battery, I'd use a 25 ohm, 10
> >> watt resistor instead, as the load would be closer to the typical
current
> >> draw in a glider. A fresh battery should stay above 11 volts for about
> >> 13-14 hours. Be sure to charge the battery at the end of the test, as
it
> >> will degrade more rapidly if it sits around uncharged.
> >>
> >> Your glider's equipment might not function as low as 11 volts, but the
> >> test does give you an idea of how good the battery is compared to a new
> >> one.
> >>
> >> --
> >> Change "netto" to "net" to email me directly
> >>
> >> Eric Greenwell
> >> Washington State
> >> USA
> >
> >
> The is available an 'intelligent battery tester' that will quickly
> measure battery capacity without the need to do a measured discharge.
>
> Visit www.actmeters.com. The model I use is ACT-IBT, although the price
> may put some people off (web site has prices in pounds and dollars).
>
> Best regards,
> Tim Newport-Peace
>
> (No commection with ACT meters except as a user).

It looks like there's an opportunity for a data logger update here.

The logger is already in the aircraft. It's generally connected to the
battery.
An 8 bit A/D would give an accuracy of 20 mV across the 10-15V range.
Sampling once per minute or so should be adequate. Post-flight analysis
should give you a pretty accurate idea of the health of the battery..
Battery health information doesn't really need to be real time, since you're
probably not going to be able to replace it in the middle of a task, anyway.

Tim Ward


Tim Ward

[tango4]

"Tim Ward" > wrote in message
...

>
> It looks like there's an opportunity for a data logger update here.
>
> The logger is already in the aircraft. It's generally connected to the
> battery.
> An 8 bit A/D would give an accuracy of 20 mV across the 10-15V range.
> Sampling once per minute or so should be adequate. Post-flight analysis
> should give you a pretty accurate idea of the health of the battery..
> Battery health information doesn't really need to be real time, since
> you're
> probably not going to be able to replace it in the middle of a task,
> anyway.
>
> Tim Ward
>
>
> Tim Ward
>
>

But it would be nice to know that you are flying with a failing battery. You
can then limit the use of power hungry devices ( Personal stereo, head-up
gunsight or electric shaver ) or simply cut the flight short before the
battery goes duff.

Maxim and others produce 'digital fuel gauges' or coulomb counters that are
compatible with modern battery technologies. These basically measure the
charge put in and power taken out of a battery whilst in-circuit with around
1% accuracy. Laptop and consumer electronics have these built into the packs
these days. It would be simple to read the DFG using your navigational iPaq
but the drawbacks are probably not worth the benefits.

( google Maxim MAX1660 for more info )

Ian

[Tim Newport-Peace]

X-no-archive: yes
In article >, Tim Ward
> writes
>It looks like there's an opportunity for a data logger update here.
>
>The logger is already in the aircraft. It's generally connected to the
>battery.
>An 8 bit A/D would give an accuracy of 20 mV across the 10-15V range.
>Sampling once per minute or so should be adequate. Post-flight analysis
>should give you a pretty accurate idea of the health of the battery..
>Battery health information doesn't really need to be real time, since you're
>probably not going to be able to replace it in the middle of a task, anyway.
>
>Tim Ward
>
>
>Tim Ward
>
Sampling the voltage will only give the percentage discharge. As a
battery ages, it's capacity drops. Thus for a new 7AH battery 50 percent
charge is 3.5AH, but for an old battery with a remaining capacity of
(say) 3AH will only have 1.5AH left at the 50 percent point.

Tim Newport-Peace

"Indecision is the Key to Flexibility."

[COLIN LAMB]

Since battery discharge is at a linear rate, you can usually begin the
discharge with a resistor and closely monitor the voltage for say one half
hour. You can make a graph from the first half hour, monitored every 10
minutes or so, and extend the line created on a graph. It is a lot quicker
than waiting for the entire discharge.

Since capacity is the ability to resist change of voltage, you can also
determine the capacity by monitoring how quickly the voltage changes on
charge. Older batteries without the ability to hold a charge will also
charge much quicker (compared to other batteries that are full capacity).
This would be a useful test for a constant current charger rather than a
constant voltage type.

Colin Lamb N12HS



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[Tim Ward]

"Tim Newport-Peace" ]> wrote in message
...
> X-no-archive: yes
> In article >, Tim Ward
> > writes
> >It looks like there's an opportunity for a data logger update here.
> >
> >The logger is already in the aircraft. It's generally connected to the
> >battery.
> >An 8 bit A/D would give an accuracy of 20 mV across the 10-15V range.
> >Sampling once per minute or so should be adequate. Post-flight analysis
> >should give you a pretty accurate idea of the health of the battery..
> >Battery health information doesn't really need to be real time, since
you're
> >probably not going to be able to replace it in the middle of a task,
anyway.
> >
> >Tim Ward
> >
> >
> >Tim Ward
> >
> Sampling the voltage will only give the percentage discharge. As a
> battery ages, it's capacity drops. Thus for a new 7AH battery 50 percent
> charge is 3.5AH, but for an old battery with a remaining capacity of
> (say) 3AH will only have 1.5AH left at the 50 percent point.
>
> Tim Newport-Peace
>
> "Indecision is the Key to Flexibility."

Yep. By post-processing the collected data, you could compare the
discharge curves of the same battery with the same load, from flight to
flight and see how it was holding up. If it's not holding up well, buy a
new battery before you go flying again.

Tim Ward