Newbie with FM80 programming questions

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Newbie with FM80 programming questions

Postby FrankB on Thu Jul 13, 2017 1:25 pm

Just installed 6 x 205 watt Solartec 72 cell panels on the roof of our RV. Voc is 45. Vmpp is 39. All panels are wired parallel with #12 solid to a combiner box, and with #8 over the remaining 20 feet to the solar controller. Battery bank is 6 x GC2 flooded cell batteries from NAPA that are about a year old. System is just installed by myself, and the FM80 is at factory default.

As a test, I have been running my aftermarket 2500 watt inverter to keep the trailer powered, and am using only the FM80 to keep the batteries charged. I deliberately left the propane fridge running on 125V to see what my new system is capable of. Something must be wrong.

I turned off the PV array to the controller this morning when I saw that the batteries were pretty much depleted, and were showing just under 12v. I waited until noon, and turned the array on to see what 'maximum performance' would be, as it is bright and sunny in Calgary today.

The FM80 beings pouring amps into the batteries in bulk mode up until it gets to about 46 amps. It then switches to absorb mode, and input current drops to 40 amps or just below. This changeover takes less than half a minute. Should it not run in bulk mode for several hours?

I tried resetting the controller. Same story. I reset the factory defaults. Same story.

I don't understand what it is that is kicking the controller out of bulk mode and into absorb within a few seconds when the battery bank is pretty much depleted.

HELP! :grin:

Frank.
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Re: Newbie with FM80 programming questions

Postby FrankB on Thu Jul 13, 2017 4:14 pm

OK, I may have found the answer by poking around on the web. It appears that the absorb voltage needs to go up from the default 14.4 volts to closer to 15.3 volts for the majority of gc2 batteries on the market. IIUC, when the controller hits the absorb voltage, it drops to absorb mode for 1 hour, then into float. Batteries are not charged properly.

I have requested specific information from the manufacturer of my batteries, but in the meantime I did put the absorb voltage threshold up to 15.3. It is now staying in bulk mode with the voltage sitting around about 14.8. We'll see what that does. :-)

I also set the absorb time up from one hour to two hours. Again, what I've seen on the web is that the absorb time for these batteries can be between two and three hours.

I am now two or three hours past solar noon here in Calgary, but I'm getting about 45 amps, which is a tad lower than the expected 50. We'll see what tomorrow brings, which is also supposed to be clear and sunny.

Frank.
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Re: Newbie with FM80 programming questions

Postby petertearai on Sun Jul 16, 2017 9:31 pm

bulk goes untill absorb voltage is reached . then it goes into absorb and absorb counter stsrts . . sulphsted battrtys will quickly get to absorb quickly . extendeding the absorb time is a good idea .. but on the face of it uour absorb voltage looks like an equilize voltage . best not to set the absorb to this voltage . .. maybe check with battery manufacturer re correct voltages .
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Re: Newbie with FM80 programming questions

Postby FrankB on Mon Jul 17, 2017 1:59 pm

petertearai:

Thank you for your input. Yes, 15.3 was WAY too high for absorb. After a couple of days, the batteries were gassing heavily, so I set everything back to default (and refilled the batteries with distilled water).

sulphsted battrtys will quickly get to absorb quickly


This is quite likely my issue. The Progressive Dynamics Charge Wizard shore power converter in my trailer is VERY conservative, and the batteries have been around for a year or more longer than I thought. They may well have been sulphated, though not anymore! :-) I have since set everything back to default, including the absorb time.

Shore power units have constant power, and 'constant' contact with the battery bank. The Outback controller appears to start again every morning. I have my doubts about the 'timed' absorb stage, as it may bear little relationship to what the batteries have been asked to do in the meantime. If they were used, well and good. If they just sat all night, then the absorb time could be well off the mark. Any suggestions on how to program for that?

I checked with the battery manufacturer (tough to find as I bought them from a nationwide reseller that buys from whoever), and I now have the correct figures. However, I suspect that the manufacturer's figures are also on the high side. I think I'm just going to buy a hydrometer, watch for gassing, and play it by ear by paying attention to real world conditions.

Thank you again for a response! I was beginning to think that no one was watching what was going on here. Not a lot of traffic. :-)

Frank.
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Re: Newbie with FM80 programming questions

Postby larrywa on Mon Jul 17, 2017 5:56 pm

FrankB wrote:petertearai:

Thank you for your input. Yes, 15.3 was WAY too high for absorb. After a couple of days, the batteries were gassing heavily, so I set everything back to default (and refilled the batteries with distilled water).

sulphsted battrtys will quickly get to absorb quickly


This is quite likely my issue. The Progressive Dynamics Charge Wizard shore power converter in my trailer is VERY conservative, and the batteries have been around for a year or more longer than I thought. They may well have been sulphated, though not anymore! :-) I have since set everything back to default, including the absorb time.

Shore power units have constant power, and 'constant' contact with the battery bank. The Outback controller appears to start again every morning. I have my doubts about the 'timed' absorb stage, as it may bear little relationship to what the batteries have been asked to do in the meantime. If they were used, well and good. If they just sat all night, then the absorb time could be well off the mark. Any suggestions on how to program for that?

I checked with the battery manufacturer (tough to find as I bought them from a nationwide reseller that buys from whoever), and I now have the correct figures. However, I suspect that the manufacturer's figures are also on the high side. I think I'm just going to buy a hydrometer, watch for gassing, and play it by ear by paying attention to real world conditions.

Thank you again for a response! I was beginning to think that no one was watching what was going on here. Not a lot of traffic. :-)

Frank.


If you have the temperature probe your voltages may be set for thermal compensation, with limits or turned off.

If you only have an FM80 it shouldn't be a problem but IIRC the FNDC sensing unit is not temperature compensated. This can cause missed voltage evenst to trigger inproperly due to fixed sensing with a variable voltage, This doesn't sound like a problem for your system (I don't see an equipment list)

My batts are basically standby only so I need to get my absorb over as soon as possible or there is no selling. With off-grid regular usage there is no hurry to stop absorb and I would attempt to keep it more gentle on your batteries and drag it all day. A compromise is necessary for an unexpected dull day with a dead battery so you want a fast charge there. No absolute win there.
Try the new Crystal eBall app. LOL :)
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Re: Newbie with FM80 programming questions

Postby FrankB on Tue Jul 18, 2017 12:31 pm

LarryWA:

Thank you for the input. I have no temperature sensor on the batteries, and retrofitting one could be an awful wiring job, so the machine is 'guessing' the charge points.

Do I understand correctly that I can program the 'end amps' for the absorb stage? I would think that if I increase that to maybe a few amps that I could avoid the battery gassing when in absorb. Even at the default 14.4 volts, I am getting some gassing as around 5 amps shows on the controller. Some of that will be parasitic load (fridge, etc.) but I don't know how much for sure.

Thanks.

Frank.
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Re: Newbie with FM80 programming questions

Postby larrywa on Tue Jul 18, 2017 1:33 pm

To use the "end amps" IIRC you will need the FNDC with shunts, or some other method to determine the current going into the battery.

If your fridge, and other equipment loads, are being drawn while the charging cycle is happening, those currents are not going into the batteries. What matters is only the difference (net) actually going into the battery that makes it gas. Think of a bucket and a small tap is running water into it. Meanwhile somebody with a cup is taking water out of it continuously. Only the water level rise in the bucket is important, not how fast the faucette was running.

In the end, you need to experiment with your bulk and absorb voltages. Make all adjustments very slight and wait a few days each time, to see the results. This will end up in a trade off between charging, as fast as you can, and wearing out your batteries. AFAIC you should not boil your batteries too much as it causes faster plate wear and tear. On the flip side of that, is needing to stir up the chemicals somewhat and wanting to get them back to 100% as fast as you can. Specific gravity readings and water usage rate will tell you in the end.

My batteries sit on standby 24/7 and I want to get my absorb cycle over each morning so I keep it short and let the "end amps" detected by the Mate3/FNDC shunts determine when the current is down to an acceptable level to ensure full batteries. This pre-empts the timer. The timer still becomes effective on dull days (or snow covered) when the end amps watching ( bulk voltage trigger was never acheived) will never be reached. It's like giving up and getting on with the rest of the day.

Having said that, I top my batteries up every 3-6 months and equalise them fairly hard. The cells reach almost 50 C sometimes if I forget to turn off the equalise, fast enough. I find the Mate3/OB system timer fails every time for equalise. I do not ever use the auto equalise due to this failure, every time, even on auto-equalise. I had to learn the hard way when it was all a confusion to me. And yet I spent 34 years maintaining battery banks for an electrical utility substation backup. It was never this complicated in constant temperature buildings. :)

Now the temperature compensation causes problems. With the cells hot at 50c the voltage compensation takes the bulk/absorb voltage down so low that the Mate3 sensing (fixed) will not turn on the selling mode. As far as the Mate3 is concerned the requirement voltage was never reached and a day's selling income doesn't happen. The system has problems with co-ordination between parts.
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My RE system: FlexPower Two
2 x GVFX3648s,
2 x FM80s,
FNDC w/3 shunts,
Mate3 v3.015.005 (works excellent!)
Hub 10.3,
PV:1000W east@45, 600W west@45, 2400W south@19 deg.
Battery:48v @ 130Ahr Crown batteries, deep cycle <$380 for 6.25kWh

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WebControl 8 as weather station stuffing
ISY994 variables via REST interface

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Re: Newbie with FM80 programming questions

Postby FrankB on Thu Aug 03, 2017 1:13 pm

larrywa:

If your fridge, and other equipment loads, are being drawn while the charging cycle is happening, those currents are not going into the batteries.


As I thought. It is for this reason that the timer is the only limit on the absorb stage at the moment, as the draw never reaches the zero amp trigger to put the charger into float mode. I have parasitic loads running all the time. I just need to figure out about how much they are, and then program a current limit to the absorb stage that compensates for the parasitic loads.

In the end, you need to experiment with your bulk and absorb voltages.


Again, as I suspected.

AFAIC you should not boil your batteries too much as it causes faster plate wear and tear.


Exactly. And this is the issue I am having with the combination of parasitic load, and long absorb time with no current limit. I end up gassing the batteries at the default 14.4 V absorb voltage once they reach full charge.

I will experiment, as you suggest, setting a long absorb time, but with perhaps a 5 amp current limit to begin with. That should cover the parasitic loads, though I will try to put an ammeter in the system somewhere so I know better. Though I hesitate to spend more money on this system, which is already over budget, I may need some sort of battery monitoring device to optimize things.

Thanks for the help!

Frank.
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Re: Newbie with FM80 programming questions

Postby blackswan555 on Thu Aug 03, 2017 11:29 pm

Though I hesitate to spend more money on this system, which is already over budget, I may need some sort of battery monitoring device to optimize things.


The absolute best battery monitor system may be a little cheaper than you think, Its called a Hydrometer, :grin: Forget about voltages and trying to count amps in and out, Check your SGs and adjust things from those,

Tim
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Re: Newbie with FM80 programming questions

Postby pss on Fri Aug 04, 2017 4:20 pm

If your batteries don't gas, then your electrolyte isn't mixing and will stratify, weakening the output of your batteries. Batteries should gas some to mix the electrolyte. What you don't want is electrolyte coming out of the vents in the cap, that is too much gassing and is a boil over. It is most imperative that the batteries have the water level maintained over the plates at all time.
So optimally, gassing is okay, should be done at a safe voltage and amount of time during the absorb stage (MPPT Bulk on the Flexmax 80) and the water levels of the batteries regularly checked and distilled water used to top them off.
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