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Old 03-03-2014, 01:48   #31
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Re: Battery Capacity Testing in the Real World

More lovely data from an overnight charge on the mains supply.
But embarrassingly somehow the charger's been set to gel....
Wonder how long it's been like that, never noticed.

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Old 03-03-2014, 05:11   #32
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Re: Battery Capacity Testing in the Real World

Interested to know how you can get voltage/time or current charts, I understand some fancy battery monitors may have an output to your computer with special software. Is there any other way?.
Years ago, on the ships we used charge discharge curves, which in theory were pretty good, I know manufacturers like secrets and I understand the limitation but still useful I feel, any thoughts?.
In regard to Discharge test, I think 12 monthly, but Mainsails comment about PITA adjusting to 20Amp rate, either couldn’t a current generator be made up or even better use a inverter with resistive ac load, as a bonus you get a low volt S/D, consistent anyway.
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Old 03-03-2014, 05:39   #33
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Re: Battery capacity testing in the real world..

Quote:
Originally Posted by hellosailor View Post
Carbon pile testers? No, that's the old technology. Still being made but not what I meant by new testers.

Amazon.com: SOLAR BA7 100-1200 CCA Electronic Battery and System Tester: Automotive
I bought this exact model. The electronics and logic are the same as expensive models. It works great.

Bill
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Old 03-03-2014, 06:21   #34
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Re: Battery Capacity Testing in the Real World

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Originally Posted by Oceanride007 View Post
Interested to know how you can get voltage/time or current charts, I understand some fancy battery monitors may have an output to your computer with special software. Is there any other way?.
.
Another way there is......
One of these;
http://www.amazon.co.uk/Arduino-Mega...duino+mega2560

With one of these and a micro sd card;

http://www.amazon.co.uk/Ethernet-W51...et+card+shield

Then a few lines of programming writes the data to the card as often as you want, wake up in the morning and it's waiting for you as a csv text file

The microprocessor only measures up to 5v so a little voltage divider is needed, then I worked out the calibration with a Fluke meter and altered the numbers in a spreadsheet which went into a little graph program, voltages seem to be accurate down to tens of millivolts against the Fluke. I programmed it to take the average of 20 readings once per minute.

I've 8 temperature sensors (cos they're so cheap) and a couple of current sensors on the way from eBay so with a power transistor or 2 and some 12v lights as a current drain I should be able to rustle up a constant current battery discharge tester at whatever current draw and down to whatever cut off voltage you want, while measuring the voltage and temperature of each cell along the way. All for the price of an average meal for 2 which should be interesting, after a solar panel took instead of giving I have 4 apparently trashed batteries onboard so it will be interesting to find out how much, if any, they come back to life with a load of equalising.


It's all very good fun and very cheap.



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Old 03-03-2014, 06:26   #35
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Re: Battery Capacity Testing in the Real World

Battery capacity testing can be done cheaply by applying a known load and monitoring the time.
It requires little equipment.

Nigel Calder recommends this test yearly which personally I think is excessive, but it is a useful test to do when preparing to sail areas where batteries are expensive or difficult to obtain. It is also useful when disposing of batteries. Sometimes individual batteries can still have useful life remaining in a poorly performing battery bank.

The 10.5 v cut off is harsh and if you can terminate the test earlier once adequate capacity has been displayed this is helpful. Recharge quickly once the capacity is established and do an equalisation cycle if this is permitted by the battery type.

The talk of sophisticated battery testers is interesting (I love gadgets), but the average cruising sailor can do a capacity test with a $10 multimeter and a few bits of wire.
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Old 03-03-2014, 07:58   #36
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Re: Battery Capacity Testing in the Real World

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Originally Posted by noelex 77 View Post
Battery capacity testing can be done cheaply by applying a known load and monitoring the time.
It requires little equipment.

Nigel Calder recommends this test yearly which personally I think is excessive, but it is a useful test to do when preparing to sail areas where batteries are expensive or difficult to obtain. It is also useful when disposing of batteries. Sometimes individual batteries can still have useful life remaining in a poorly performing battery bank.

The 10.5 v cut off is harsh and if you can terminate the test earlier once adequate capacity has been displayed this is helpful. Recharge quickly once the capacity is established and do an equalisation cycle if this is permitted by the battery type.

The talk of sophisticated battery testers is interesting (I love gadgets), but the average cruising sailor can do a capacity test with a $10 multimeter and a few bits of wire.
Agree up to a point but I'm not convinced how repeatable or how accurate testing with a multimeter and few bits of wire can be, lots of variables. Though probabaly plenty to let you know if there's still a bit of life left in your batts. For $20 or $30 you can have an arduino with a card writer plus current and temp sensor and a relay to turn off your load. Then have very repeatable accurate graphs of how the battery behaved over time to compare next time you think they might be getting a bit slow. Cost certainly isn't the issue, the big one probably is IF you're made that way, if you find fiddling with bits of electronics fun
Many don't
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Old 04-03-2014, 03:50   #37
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Re: Battery Capacity Testing in the Real World

Another night this time sans charger, you can even see when that cloud went over earlier
Enough for now, current and temp next.

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Old 04-03-2014, 04:11   #38
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Re: Battery Capacity Testing in the Real World

One advantage of the traditional capacity test is that it is directly measuring what we interested in:

How many amp hours we can withdraw from the battery.

It can even be tailored so that the discharge is representative of our real world draw eliminating Peukert's calculations/estimations.

It is a time consuming test to do, but it requires minimal equipment and can be done by any cruising sailor. While much more sophisticated tests are available, with suitable equipment, these are a more indirect method of measuring storage battery capacity.

I hope we don't loose sight of the value of the simple capacity test.
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Old 04-03-2014, 04:30   #39
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Re: Battery Capacity Testing in the Real World

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Originally Posted by noelex 77 View Post
One advantage of the traditional capacity test is that it is directly measuring what we interested in:

How many amp hours we can withdraw from the battery.

It can even be tailored so that the discharge is representative of our real world draw eliminating Peukert's calculations/estimations.

It is a time consuming test to do, but it requires minimal equipment and can be done by any cruising sailor. While much more sophisticated tests are available, with suitable equipment, these are a more indirect method of measuring storage battery capacity.

I hope we don't loose sight of the value of the simple capacity test.
Maybe you missed the previous posts but that's exactly what the aim is, only in a much more accurate manner then using some wire and a watch. With cheap microprocessors available now it should be possible (I'll find out in a day or so when some more bits turn up ) to do a constant current capacity test to whatever cutoff voltage you want with whatever current draw you want, accurately measuring temperature and voltage along the way. All for the cost of a few beers with just a small amount of programming/electronics knowledge. Then have the ability to do a repeatable test, even if not total discharge but down to 50%, but some accurate data about how your batteries are holding up.
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Old 16-03-2014, 18:00   #40
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Re: Battery Capacity Testing in the Real World

For anyone interested........
A few more ebay bits and current has been added to the logging. Did a quick test tonight just to see something working, voltage is proving a bit awkward to calibrate but overall things are cheerful

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Old 27-05-2014, 22:05   #41
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Re: Battery Capacity Testing in the Real World

Hey Conachair,
Could you adapt your Arduino for a semi permanent setup. Could have bar graphs or digital monitoring of different things, did you ever consider the input impedence of the Arduino to measure 5 Volt (otherwise measuring could effect the result, could use Opamps), also for remote measuring (say more than a few meters) maybe convert the signal to 4-20ma and and use a 250 ohm resister across the Arduino. Would appreciate a PM to discuss further, I would like to see your sketch (code) and discuss source of economical pressure and other real world transducers, this could be exciting (for some).

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Old 07-09-2016, 11:49   #42
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Re: Battery Capacity Testing in the Real World

I realize this is an older post but some may find this inexpensive electronic load worthy of consideration. It has separate amp and volt sense leads and with the supplied software is fully programmable. With it's 150W rating this unit can handle up to a 230ah 12V battery.

eBD A20H Electronic Load Power Battery Capacity Tester Resistance Discharge | eBay?

I have one and found it quite acceptable once you swap out the test leads with properly sized wire.
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Old 08-09-2016, 11:05   #43
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Re: Battery Capacity Testing in the Real World

very interesting. I SO hate buying stuff off eBay from China, but for the price, it is interesting though.
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Old 08-09-2016, 14:16   #44
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Re: Battery Capacity Testing in the Real World

I would have some guilt as well if there was ANY competition from a US company...but there is none at this price point. For those of us that will do this test once a year this is a reasonable alternative.

There are cheaper electronic load alternatives but those are capped at 10A so they would only be able to test a 200ah battery and they are not programmable like this unit.

I considered going the very inexpensive route ($39 for a 10A 150W electronic load) but I would have had to use Peukert's Law to derive the Ah capacity of my battery at a lower than C20 discharge rate. Easy enough but the programing feature of the unit I posted earlier really made the decision for me.
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