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Old 04-06-2012, 10:29   #1
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Need Help Setting up my Battery Monitor

I have a LinkPro that had been working fine for over a year. But then I decided to fine tune it by tweaking the self discharge rate and temperature compensation. Now I'm suddenly "losing" about 1.5 ah per day. (The batteries are fully charged according to open circuit testing with a digital volt meter and temperature compensated hydrometer).

I have two 6-volt Trojans in series, topped off by a solar panel that is more than adequate for replenishing any self discharge.

Trojan says conflicting things about the self discharge rate: "about 4% per week," or "10-15% per month." I set the monitor at 15%.

Trojan says the temperature coefficient is 1.2%/C (which I confirmed via email with tech support). I set the monitor at 1%/C, which is its highest setting.

I set the nominal temperature for the battery ratings to 25C, and left the battery temp setting at the default 20C, which is typical for my location. I have not yet installed a temperature monitor.

Both the self discharge rate and temperature coefficient seem high to me (especially since the latter is beyond the Xantrex setting limit). Any suggestions for better settings?

BTW, nothing in the system has changed--the missing capacity results solely from the changed settings. There are no new loads, the solar panel and controller are working fine, and the monitor is recording the incoming amps. It's just that the meter thinks it's losing more capacity at night than the sun can replenish.
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Old 04-06-2012, 15:21   #2
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Re: Need help setting up my battery monitor

Perhaps the monitor is thinking that 15% is per day. Don't know why you're confused about the difference of 4% per week vs. 15% per month, four weeks in a month.

With that high a self discharge, you're probably right thinking the montior is thinking that the batteries are discharging.

Why'd you mess with something that worked?
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Old 04-06-2012, 15:37   #3
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Re: Need help setting up my battery monitor

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Originally Posted by Stu Jackson View Post
Perhaps the monitor is thinking that 15% is per day. Don't know why you're confused about the difference of 4% per week vs. 15% per month, four weeks in a month.

With that high a self discharge, you're probably right thinking the montior is thinking that the batteries are discharging.

Why'd you mess with something that worked?
Stu, I know not to expect too much precision in discharge rates, but 10-15% is quite a spread, while 4% per week extends that range to more than 17%. (I'm a little frustrated with Trojan's online documentation because it's often not consistent.)

The LinkPro is looking for %capacity/month. The default is 3%, which is not realistic for flooded batteries. I just wanted to track things a little closer.

I guess I'm looking for a reality check. According to Trojan, my batteries have a self discharge rate of more than 500% of Xantrex's default setting, and my temperature coefficient is almost 250% of Xantrex's default--while also 20% beyond the max limit on their scale.

Any suggestions on working numbers? I'm not ready to return to the default values--yet.
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Old 04-06-2012, 18:40   #4
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Re: Need help setting up my battery monitor

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Stu, I know not to expect too much precision in discharge rates, but 10-15% is quite a spread, while 4% per week extends that range to more than 17%. (I'm a little frustrated with Trojan's online documentation because it's often not consistent.)

The LinkPro is looking for %capacity/month. The default is 3%, which is not realistic for flooded batteries. I just wanted to track things a little closer.

I guess I'm looking for a reality check. According to Trojan, my batteries have a self discharge rate of more than 500% of Xantrex's default setting, and my temperature coefficient is almost 250% of Xantrex's default--while also 20% beyond the max limit on their scale.

Any suggestions on working numbers? I'm not ready to return to the default values--yet.
The only reality check I can give you is one of playing "forensics" or detective work from afar. I'll give it a try.

1. self discharge: Function F5.5, right? As I understand your presentation, raising this gives you negative accumulation. My read is what I said in my last post. If it's too high, regardless of what Trojan's telling you, then either revert to default (I know you don't wanna!), OR what I'd do as Inspector Clouseau, would be to drop it measurably over its range in reasonable increments of your choice. See what happens.

2. F5.3, right? Temp coeff. Note that it is in degrees CELSIUS, not Fahrenheit, so if you have a table, which generally shows battery changes per degrees, you'd have to calculate it. I haven't calculated one, but I'd first look at the table labeled "Temperature / Charging Voltages" which would be easy to find in published literature. Either convert F to C degrees or find a table with C already. That'd be a reasonable selection, see if it's anywhere near the default. An interesting exercise anyway to see how they calculated the default.

The other defaults you should question are these: F1.0 and F1.1.

You might be interested in this:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Thanks for the topic, very interesting. I might go look up one of those tables and see what come out.
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Old 04-06-2012, 19:06   #5
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Re: Need Help Setting up my Battery Monitor

Thanks, Stu.

I've read the gotcha factor stuff, and that hasn't been a problem for me--especially now!

With regard to the temperature coefficient, Trojan says 15F makes a 10% change in capacity, in both directions. That translates to 1.2%/C (the LinkPro want's C figures). I emailed Trojan and they confirmed my calculations.

It's gotta be the self discharge rate that's off, because the temperature coefficient would not change the capacity over time (no temp monitor, so the ratio of nominal temp to "actual" temp is static). However, maybe this could multiply the effect of errant self discharge rate since it automatically lowers the capacity? Maybe not--that should just give it a lower starting point and not have a dynamic effect?

I'm just a curious guy--and I tend to dwell on things then they don't work as planned--even though it often doesn't mean anything.
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Old 04-06-2012, 19:19   #6
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Re: Need Help Setting up my Battery Monitor

I just played around graphing Temperature C vs. Acceptance Voltage from a popular charger's manufacturers literature. It's pretty much a straight line shot - the curve is straight.

Here are the numbers I used:

Temp C Accept V Float 49 12.5 12.5 43 13.6 12.7 38 13.8 12.9 32 14 13.1 27 14.2 13.3 21 14.4 13.5 16 14.6 13.7 10 14.8 13.9 5 15 14.1 -1 15.2 14.3

I really haven't calculated the slope, yet.
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Old 04-06-2012, 19:32   #7
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Re: Need Help Setting up my Battery Monitor

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Originally Posted by Jbaffoh View Post
Thanks, Stu.
....
....

It's gotta be the self discharge rate that's off, because the temperature coefficient would not change the capacity over time (no temp monitor, so the ratio of nominal temp to "actual" temp is static). However, maybe this could multiply the effect of errant self discharge rate since it automatically lowers the capacity? Maybe not--that should just give it a lower starting point and not have a dynamic effect?

I'm just a curious guy--and I tend to dwell on things then they don't work as planned--even though it often doesn't mean anything.
I enjoy the curiosity, too.

I agree that it is the self discharge rate. Leaving F1.4 temp at the default of 20C makes sense without a sensor installed. The LinkPro should just use a single (static) temperature since it is not getting any "input" from that source, based on how the instruction manual describes it. You're right, no dynamic effect at all.

It's gotta be the self discharge rate. So, I'd try what I suggested. Would be very interested to learn what happens.

Glad the "Gotcha" helped. Nice to find someone else who understands it! Maine Sail and I have been doing this for years!

Also glad you understand "defaults"...

All the best,

Stu
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Old 04-06-2012, 19:42   #8
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Re: Need Help Setting up my Battery Monitor

One other thought: Someone once taught me that if you have two things to perform, like when working on your engine, ONLY do one thing at a time and restart the engine, 'cuz if you do two things at once and it doesn't restart, you won't know which one of the two things you did that was snafued!

Sounds like this could be the same thing here, so you could take the approach of defaulting both or either and doing only one at a time.

Your boat, your choice!
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Old 04-06-2012, 20:32   #9
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Re: Need Help Setting up my Battery Monitor

Try this
Attached Files
File Type: doc Temp Charging Voltage Curve.doc (44.5 KB, 61 views)
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Old 05-06-2012, 19:16   #10
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Re: Need Help Setting up my Battery Monitor

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Try this
Thanks, Stu!

If I'm interpreting that right, the temp coefficient for capacity to absorb is 2.7%/C--at least according to a charger?
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Old 05-06-2012, 19:18   #11
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Re: Need Help Setting up my Battery Monitor

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One other thought: Someone once taught me that if you have two things to perform, like when working on your engine, ONLY do one thing at a time and restart the engine, 'cuz if you do two things at once and it doesn't restart, you won't know which one of the two things you did that was snafued!

Sounds like this could be the same thing here, so you could take the approach of defaulting both or either and doing only one at a time.

Your boat, your choice!
Ah, the old scientific method of isolating variables. Very interesting
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Old 08-06-2012, 03:12   #12
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Re: Need help setting up my battery monitor

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Originally Posted by Stu Jackson View Post

You might be interested in this:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!
Battery return Amps is usuful way of a battery monitor resetting itself. IMHO it is a feature that should not be disabled, but setting of 13.2v is much too low and will result in silly readings.
Try setting the voltage to 0.2v below the bulk charge voltage value, the return amps to 1.5-2.0% and the time to a few minutes. I think you will find it a very useful and valuable feature of any battery monitor when more sensible parameters are used.
Dropping back the charging to a float value is also sensible when these parameters have been met. This is more critical with gel and AGM batteries, particularly when charged by solar, where the charge voltage can sometimes be just below the absorption threshold for long periods.
The return amps under float conditions will give you an idea if the parameters were correct.
The only slight problem with this is the battery monitor will read a couple of percent high, but this is preferable to the monitor getting a long way out of sinc.
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Old 08-06-2012, 10:28   #13
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Re: Need help setting up my battery monitor

As useful as battery monitors are, keeping the displayed Ah capacity and the actual capacity synchronised is the one major problem with them.

There are many complicated reasons for this, but all batteries have different Ah charge and discharge values depending on how many amps are going in or out. So discharging at 20 amps for 1 hour should mean that the Ah meter will read - 20Ah, or discharging at 1 amp for 20 hours should also read - 20 Ah. This doesn’t happen because of Peukerts constant which adjust the actual values depending on the size of the current. Charging is another problem because of the “efficiency” of the battery at accepting charge. Wet cells may be only 75% efficient whereas AGMs may be 98%. The capacity of the bank also has to be entered into the software. All these values change over time, which will upset the Ah count accuracy.

The UK military finally demanded more accurate battery monitors - so enter the SmartGuage. This is a very sophisticated monitor that uses clever mathematical algorithms to work out the % depth of discharge of the batteries just by measuring the voltage. It doesn’t use a shunt, so is cheaper and very much easier to install, and has proved to be much more accurate. Anybody with a battery monitor, or interested in installing one, should read the extensive details at the SmartGuage website:

SmartGauge Electronics - SmartGauge battery monitor
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Old 08-06-2012, 10:42   #14
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Re: Need help setting up my battery monitor

Many battery monitors will compensate for Peukerts formular and the battery efficiency factor is adjustable.
Smart gauge use a very different and simple monitor. It measures voltage only and does not measure current like most battery monitors.
it's easy to install, does require much set so is simple for people a bit electrically challanged, but not as good as a proper battery monitor IMHO.
Midnite make a similar monitor.
As an alternative the NASA battery monitor uses both techniques, but if you can set it up properly the traditional battery monitor is best.
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Old 08-06-2012, 10:46   #15
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Quote:
Originally Posted by sailinglegend
As useful as battery monitors are, keeping the displayed Ah capacity and the actual capacity synchronised is the one major problem with them.

There are many complicated reasons for this, but all batteries have different Ah charge and discharge values depending on how many amps are going in or out. So discharging at 20 amps for 1 hour should mean that the Ah meter will read - 20Ah, or discharging at 1 amp for 20 hours should also read - 20 Ah. This doesn’t happen because of Peukerts constant which adjust the actual values depending on the size of the current. Charging is another problem because of the “efficiency” of the battery at accepting charge. Wet cells may be only 75% efficient whereas AGMs may be 98%. The capacity of the bank also has to be entered into the software. All these values change over time, which will upset the Ah count accuracy.

The UK military finally demanded more accurate battery monitors - so enter the SmartGuage. This is a very sophisticated monitor that uses clever mathematical algorithms to work out the % depth of discharge of the batteries just by measuring the voltage. It doesn’t use a shunt, so is cheaper and very much easier to install, and has proved to be much more accurate. Anybody with a battery monitor, or interested in installing one, should read the extensive details at the SmartGuage website:

SmartGauge Electronics - SmartGauge battery monitor
Is this an ad?

I've been led to believe the LinkPro and similar monitors also use sophisticated algorithms based on precise measurements of millivolts across the shunt. What does the Smart Meter do differently?

However, while your advice is interesting, I've obviously purchased and installed my meter with it's shunt. My question was about finding realistic self-discharge rates and temperature coefficients for my Trojan T-145 batteries so I can improve the accuracy of my meter. Got advice? Or just marketing hype?
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