My daily charge is dropping for no reason?

[raysun]

Today's FM80 activity. It ran bulk till about 9 AM. Switched to Absorb. Voltage slowly went up, but only got to 14.5V. Didn't reach the absorb voltage setting of 14.7 V. It switched to floating at 12, after the 3 hour absorb timeout.

Is that bad?

The voltage readings are the OUT Voltage on the FM80?

The charger starts a Bulk charge and maintains it until the battery reaches the Absorb Voltage, only then should the charge controller switch from Bulk to Absorb stage.

What is the Absorb Voltage setting? (Double check.)

The charging behavior described is unusual.

[bikemechanic53]

The absorb voltage is set at 14.7V. I didn't record the end voltage for the bulk charging section. Oops. I'll do that tomorrow.

[raysun]

It should be 14.7V

The voltage fluctuating below that is typical if there's not enough charging current to maintain 14.7V, and the charge controller should switch back to Bulk if below 14.7

There's two sets of numbers displayed on the FM80 - Volt IN, Amp IN / Volt OUT, AMP OUT

IN is voltage and current coming from the array.
OUT is battery voltage, and current flowing to the battery. The display also shows instantaneous kilowatts, and accumulated kilowatt hours.

The numbers are tracking the charge cycle, and also the amount of solar power harvested.

The Victron monitor makes that easier to track.

[bikemechanic53]

Good to know. I hope to get the Victron delivered by end of next week.

[raysun]

Good to know. I hope to get the Victron delivered by end of next week.

Before you get it, spend some quality time familiarizing with the FM80 data screens. Its valuable to be able to read the data.

[pss]

You are trying to approach mixing panels of various powers together so they add up like solving a math problem. that doesn't work in the real word case for solar panels and you cannot do it. also, your math is missing the internal resistance of each cell within a panel and the direction current will flow. Better minds than mine have researched the mix and match and it is not possible except with a resultant loss of power, not a gain as you might have added up to.

[bikemechanic53]

You are undoubtedly correct. However, I did get a significant power increase with the new panels. Not as much as I would have gotten had I been able to add more of the original panels, but Evergreen went out of business some time ago.

[bikemechanic53]

I have received the Smart Shunt, but not the GCSOAR controller, as they screwed up the shipping.

However, I was rear ended 2 days ago. Lots of damage. The insurance company and the RV repair shops are trying to decide if they will declare this accident a total loss. Which means I'll need another RV. So I won't be making the solar changes any time soon. I expect to move my solar system over to whatever RV I buy. That will take some time and a huge amount of work that I'm not looking forward to.

SO, I will get back to you guys when this current problem is resolved. Hopefully, to continue with my solar upgrade.

[raysun]

Yikes!

I hope you were not injured.

Please do keep in touch.

[bikemechanic53]

I have bought another RV. This one has a generator in it. I'm planning how to install my solar system in this RV. My FM80 may have to go in one of the storage areas. Currently it's accessible from inside my living room. I'd like to have remote access to it. I've read about the MATE. Would that work with my 12 year old FM80?

I don't know what to do with the generator yet. I'll keep it, but don't expect to use it much. I have run only on solar for 12 years.

[raysun]

Will the storage space provide enough ventilation for heat dissipation from the FM80? Also, it needs to be mounted vertically.

A Mate will allow programming without pushing buttons on the FM80. There are two models: Mate2 and Mate3s. The both will work fine with your FM80. The '2 is plenty enough for the task, especially since the FM80 is pretty much "set and forget" when configured properly.

Having the SmartShunt will give much better battery status data than the FM80 can.

12 years on solar only is an admirable track record! What is the generator model? I assume its wired into the house circuits through some kind of load center? The inverter is going to need to wire into the house power system as well, yes?

[bikemechanic53]

I'm planning on putting all the solar components and the batteries in the 2' x 2' pass through in this RV. I'll have to see how it goes with heat output. I will be putting a fan on one of the doors to pull air through when equalizing the batts. Yes, there's a lot of wall space for vertical mounting.

I'll probably go with the simpler Mate2. I don't see the need for the extra functions of the 3. The generator is an Onan 5.5 KW EVAP model. I don't yet know how everything is connected. I'll find out in a week or so when I get it. My first thought is to use the existing switch to go between the 2 power sources. I have no need for shore power, so can use that switch. I don't know how I will connect the Xantrex inverter.

This is a 2016 trailer, so has had some good use.

[bikemechanic53]

I am planning on putting the batteries in a heated cargo area under the bedroom of the RV I'm getting. In my current RV, the batteries are not in a heated area, and capacity drops by, I think, around 50% in cold weather. 20-0 degrees.

Does that seem like a reasonable thing to do?

[raysun]

I am planning on putting the batteries in a heated cargo area under the bedroom of the RV I'm getting. In my current RV, the batteries are not in a heated area, and capacity drops by, I think, around 50% in cold weather. 20-0 degrees.

Does that seem like a reasonable thing to do?

What do you estimate the ambient temperature will be in the heated area on the hottest days? Is the heating thermostatically controlled?

Batteries have a few major "killers", and high temperatures are one of them.

As you have noticed, battery capacity declines in cold temperatures, but longevity increases. In high temperatures, battery capacity increases, but longevity declines.

The decrease/increase are temporary, and vary with ambient temperature.

Sealed Lead Acid batteries have an operating range from 0°F to 140°F. At the lowest temperatures (below freezing) its important to keep the battery charged so the electrolyte doesn't freeze. At the highest temperatures (90°F and above) heat stress can warp lead plates and separators, and contribute to electrolyte venting.

[bikemechanic53]

The pass through area will probably be at ambient temp. Last summer there were temps in central Oregon over 105 for about a week. I might be able to vent some AC into that area. I'll have to see.

[raysun]

The Temperature Compensated Charging supported by the FM80 will help during excursions into hot weather. Likely it can be helped a bit by lowering the Absorb and Float voltages 0.1 volt during the hottest stretches.

Cooling the space, if available, is the best solution. Keeping it below 90°F is ideal.

Also, reading back, your Trojan L16s are flooded lead acid. Same considerations apply, but they are a bit more tolerant to high temperatures.

[bikemechanic53]

OK. Good to know. Thanks.

[bikemechanic53]

My FM80's absorb voltage, which is set at 14.7 V, has recently (last 3 days) gone up to 15.1 V. I don't know why. It triggers the Xantrex inverter to shut down. Which it should not, as it is rated to handle 15.5 V.

Anyone know why the FM80 would be running at a higher absorb voltage than it's limit?

Thx

[raysun]

Is the 15.1V being reported on the FM80's front panel as the Out Volts?

What is the voltage, as measured at the battery terminals with a voltmeter?

[bikemechanic53]

Yes, the FM80 is showing 15.1 V. The battery terminals are reading slightly less, at 14.9V.

[raysun]

Four general areas where the voltage readings and output can be thrown off:

• Wiring between the battery and the FM80
• FM80 calibration
• Temperature compensation sensor
• Defective charge controller

The first thing to check is the battery voltage at the key points in the circuit. This can be a bit tricky, as inputs (charge current) and outputs (discharge current) constantly change the battery voltage. The first set of measurements should be taken when the system is quiet - no charge current, and no discharge current.
Measure the voltage:
- at the battery terminals
- at the FM80 bat +/- terminals
- at the inverter bat +/- terminals
With no current flowing, the three measurements should agree. If they are off, check the wiring between the battery and the affected unit for loose or corroded connections.

Next compare the voltage reading from the FM80 bat +/- terminals to the Out voltage on its front panel. The readings should agree. If not, the FM80 should be calibrated. There is a Calibrate function in the FM80 configuration menu.

While in the menus, double check the Absorb and Float voltages, make sure they are set properly.

Check the Remote Temperature Sensor. Make sure it is firmly seated in the proper port in the FM80, and that the sensor is properly connected to the side of a battery block.

Turn on the system and allow the battery to charge. When Absorb is reached, repeat the voltage measurements at the battery terminals and FM80 bat +/- terminals. They should agree. The Out voltage on the FM80 front panel should match the voltage measurements.

If the measured voltages don't agree, check all connections between the FM80 and the battery.

If the voltage at the FM80 is too high, temporarily unplug the RTS cable prior to the next charge cycle (when the FM80 is idle) and observe charging without it.

[bikemechanic53]

Four general areas where the voltage readings and output can be thrown off:

• Wiring between the battery and the FM80
• FM80 calibration
• Temperature compensation sensor
• Defective charge controller

The first thing to check is the battery voltage at the key points in the circuit. This can be a bit tricky, as inputs (charge current) and outputs (discharge current) constantly change the battery voltage. The first set of measurements should be taken when the system is quiet - no charge current, and no discharge current.
Measure the voltage:
- at the battery terminals
- at the FM80 bat +/- terminals
- at the inverter bat +/- terminals
With no current flowing, the three measurements should agree. If they are off, check the wiring between the battery and the affected unit for loose or corroded connections.

Next compare the voltage reading from the FM80 bat +/- terminals to the Out voltage on its front panel. The readings should agree. If not, the FM80 should be calibrated. There is a Calibrate function in the FM80 configuration menu.

While in the menus, double check the Absorb and Float voltages, make sure they are set properly.

Check the Remote Temperature Sensor. Make sure it is firmly seated in the proper port in the FM80, and that the sensor is properly connected to the side of a battery block.

Turn on the system and allow the battery to charge. When Absorb is reached, repeat the voltage measurements at the battery terminals and FM80 bat +/- terminals. They should agree. The Out voltage on the FM80 front panel should match the voltage measurements.

If the measured voltages don't agree, check all connections between the FM80 and the battery.

If the voltage at the FM80 is too high, temporarily unplug the RTS cable prior to the next charge cycle (when the FM80 is idle) and observe charging without it.

I've gone through the sequences you outlined above. The FM80 is working correctly. There are a couple of sketchy connections on the DC negative bus. I'll replace that when I move the system over next week. Only the Xantrex inverter is an issue. It's consistently reading .2 V higher than what the voltmeter says it's inputs are.

Thanks for this info. Helped me figure out what was happening.

[bikemechanic53]

Hello All, I am finally moving my power system over to my new trailer/RV/5th wheel/toy hauler.

My current setup is a 12 year old 12 Volt system consisting of:

4 L16 size 6 Volt Discover Dry Cell (AGM) batteries
4 Evergreen 200W panels, 18 V and 10 A, two pairs (in series) connected in parallel for an input to the FM80 of 36 V and 20 A.
1 FM80
1 Xantrex 2 KW inverter
4 circuit breakers

and 2 6 month old REC panels @ 40 V and 10 A each. Connected in parallel with each other and the older 200W panels.

I have now got all new cables. I have the Victron Smart Shunt and the GCSOAR PWM charge controller as recommended by raysun.

Per raysun, I plan to connect the 2 REC panels to the GCSOAR PWM and the output of that to the FM80.

I need to know how to set up the GCSOAR PWM and the FM80 to make this work.

[raysun]

Hey there.

Sounds like you have a good project in front of you!

First, of course, is to physically install the battery. Next install the SmartShunt. Finally, connect the inverter, chargers, and other loads.

Dual solar charging
The idea is to have the PWM controller contribute charge during the Bulk stage, then essentially drop out during the Absorb stage. The FM80 will contribute charge during both Bulk and Absorb.

The two controllers will need to collaborate, and their common control point is battery voltage. They will need to be calibrated to agree on voltage. If that's not possible, then the difference in readings need to be accommodated in the programming.

The important parameters to adjust are the maximum charge current during Bulk, and the Absorb Voltage and Time, and Float Voltage.

Which model of the PWM controller do you have?

I couldn't find a copy of the GCSOAR manual on line, but assume one came with the controller. It will be programmed by selecting the USER mode, rather than its preset profiles (Flooded, AGM, Gel, etc.)

Step #1: Determine battery maximum charging rate.

I don't recall the battery specs, but the typical L16 6V Trojan has a 320AH capacity @ C20. Two parallel banks = 720AH. The typical AGM can handle charge rates around 20%. 720AH @ 20% = 144A, so no problem running the controllers at full output.

(Confirm these calculations.)

#2 Determine Absorb Voltage and Absorb Time
The Trojan charging specs will give the figures for Absorb charging. These values will be programmed into the FM80.

#3 Determine Float Voltage
The Trojan charging specs will give this value. It will be programmed into the FM80.

#4 Calibrate, Program and Test the FM80
Connect the FM80 to the battery (if not done already) and disconnect from the solar panels. (If physically disconnecting, rather than via a DC circuit breaker or switch, do so while the panels are NOT under load. Otherwise, a nasty DC arc may result.)

Measure the voltage at the FM80 Bat +/- terminals. Compare the measurement to the front panel Out Volt which is the FM80's internal voltmeter reading of the battery voltage. The two readings should agree. If not, the FM80 should be calibrated. viewtopic.php?t=15400

Program the Absorb Voltage, Absorb Time, and Float Voltage into the FM80

Run it through a charge cycle and confirm its working as programmed.

#5 Connect the PWM controller to the battery.
CONNECT TO BATTERY BEFORE CONNECTING TO SOLAR PANELS. This is always important as connecting to solar panels without connecting to the battery first will damage the controller.

#6 Measure battery voltage at PWM controller terminals, and compare with front panel reading.

The battery reading at the charge controller Bat +/- terminals should agree with those at the FM80 Bat +/- terminals. Note any difference.

If the controller has a battery voltage readout, compare to the measured voltage. If the controller has a calibrate function, use it to align the measured voltage with the controller's internal voltmeter reading. Otherwise, note the discrepancy.

#7 Program the USER profile.
The Absorb stage is called "Boost", I believe.

Program the Boost voltage to be 0.1V lower than the FM80 Absorb voltage. If the controllers are both accurately calibrated, the actual parameter value will be -0.1V relative to the FM80 Absorb Voltage. If calibration is off, the Boost Voltage value will need to be adjusted accordingly. When the Absorb and Boost voltages are programmed properly, at the point the FM80 switches to Absorb, the PWM controller should go silent. (As the battery voltage will have risen above its Boost Voltage set point.)

If the PWM controller has a Boost Time setting, make it as short as possible (but not zero.)

Set the Float Voltage 0.1V below the FM80 Float Voltage.

Connect the solar panels. (It may be best to do this early in the morning before the "FM80 wakes up".)

#8 Test the two charge controllers together.

The two controllers should "wake up" and start a Bulk charge cycle.

Once the battery rises to the PWM controller's Boost Voltage, it will switch to that stage. The battery should continue to rise another 0.1V to the FM80 Absorb Voltage, and it should switch to Absorb. At about the same time, the PWM controller should go silent.

When the PWM controller drops out, the FM80 may revert to Bulk charging due to the reduction in total charge current. That's expected. The PWM will likely "wake up" and resume charging. The Absorb stage will be reached again. This cycle may repeat many times, depending on load and solar conditions. Not to worry, its just the "controller two-step" dance. Eventually enough charge will have been put into the battery so the FM80 alone can maintain Absorb.

Once Absorb is complete, the controllers will switch to Float. If the FM80 can maintain Float alone, the PWM will stay silent.

It may take a bit of voltage parameter "tweaking" on the PWM to get it operating smoothly with the FM80. The important thing is the Boost and Float voltages be a true 0 1V lower than the FM80 Absorb and Float.

[bikemechanic53]

Hey there.

Sounds like you have a good project in front of you!

First, of course, is to physically install the battery. Next install the SmartShunt. Finally, connect the inverter, chargers, and other loads.

Dual solar charging
The idea is to have the PWM controller contribute charge during the Bulk stage, then essentially drop out during the Absorb stage. The FM80 will contribute charge during both Bulk and Absorb.

The two controllers will need to collaborate, and their common control point is battery voltage. They will need to be calibrated to agree on voltage. If that's not possible, then the difference in readings need to be accommodated in the programming.

The important parameters to adjust are the maximum charge current during Bulk, and the Absorb Voltage and Time, and Float Voltage.

Which model of the PWM controller do you have?

I couldn't find a copy of the GCSOAR manual on line, but assume one came with the controller. It will be programmed by selecting the USER mode, rather than its preset profiles (Flooded, AGM, Gel, etc.)

Step #1: Determine battery maximum charging rate.

I don't recall the battery specs, but the typical L16 6V Trojan has a 320AH capacity @ C20. Two parallel banks = 720AH. The typical AGM can handle charge rates around 20%. 720AH @ 20% = 144A, so no problem running the controllers at full output.

(Confirm these calculations.)

#2 Determine Absorb Voltage and Absorb Time
The Trojan charging specs will give the figures for Absorb charging. These values will be programmed into the FM80.

#3 Determine Float Voltage
The Trojan charging specs will give this value. It will be programmed into the FM80.

#4 Calibrate, Program and Test the FM80
Connect the FM80 to the battery (if not done already) and disconnect from the solar panels. (If physically disconnecting, rather than via a DC circuit breaker or switch, do so while the panels are NOT under load. Otherwise, a nasty DC arc may result.)

Measure the voltage at the FM80 Bat +/- terminals. Compare the measurement to the front panel Out Volt which is the FM80's internal voltmeter reading of the battery voltage. The two readings should agree. If not, the FM80 should be calibrated. viewtopic.php?t=15400

Program the Absorb Voltage, Absorb Time, and Float Voltage into the FM80

Run it through a charge cycle and confirm its working as programmed.

#5 Connect the PWM controller to the battery.
CONNECT TO BATTERY BEFORE CONNECTING TO SOLAR PANELS. This is always important as connecting to solar panels without connecting to the battery first will damage the controller.

#6 Measure battery voltage at PWM controller terminals, and compare with front panel reading.

The battery reading at the charge controller Bat +/- terminals should agree with those at the FM80 Bat +/- terminals. Note any difference.

If the controller has a battery voltage readout, compare to the measured voltage. If the controller has a calibrate function, use it to align the measured voltage with the controller's internal voltmeter reading. Otherwise, note the discrepancy.

#7 Program the USER profile.
The Absorb stage is called "Boost", I believe.

Program the Boost voltage to be 0.1V lower than the FM80 Absorb voltage. If the controllers are both accurately calibrated, the actual parameter value will be -0.1V relative to the FM80 Absorb Voltage. If calibration is off, the Boost Voltage value will need to be adjusted accordingly. When the Absorb and Boost voltages are programmed properly, at the point the FM80 switches to Absorb, the PWM controller should go silent. (As the battery voltage will have risen above its Boost Voltage set point.)

If the PWM controller has a Boost Time setting, make it as short as possible (but not zero.)

Set the Float Voltage 0.1V below the FM80 Float Voltage.

Connect the solar panels. (It may be best to do this early in the morning before the "FM80 wakes up".)

#8 Test the two charge controllers together.

The two controllers should "wake up" and start a Bulk charge cycle.

Once the battery rises to the PWM controller's Boost Voltage, it will switch to that stage. The battery should continue to rise another 0.1V to the FM80 Absorb Voltage, and it should switch to Absorb. At about the same time, the PWM controller should go silent.

When the PWM controller drops out, the FM80 may revert to Bulk charging due to the reduction in total charge current. That's expected. The PWM will likely "wake up" and resume charging. The Absorb stage will be reached again. This cycle may repeat many times, depending on load and solar conditions. Not to worry, its just the "controller two-step" dance. Eventually enough charge will have been put into the battery so the FM80 alone can maintain Absorb.

Once Absorb is complete, the controllers will switch to Float. If the FM80 can maintain Float alone, the PWM will stay silent.

It may take a bit of voltage parameter "tweaking" on the PWM to get it operating smoothly with the FM80. The important thing is the Boost and Float voltages be a true 0 1V lower than the FM80 Absorb and Float.

Wow, you've got a lot of information here. I've gone through it a couple of times.
I've got all the solar components moved over to the new RV. ( I keep saying FINALLY, but finally keeps getting extended.) However, I am waiting on some more MC4 connectors to arrive early next week. So the GCSOAR is not yet connected to it's set of panels.

Just to recap:
My current setup is a 12 year old 12 Volt system consisting of:

4 L16 size 6 Volt Discover Dry Cell (AGM) batteries. See: https://discoverbattery.com/products/search/EV305A-A
4 Evergreen 200W panels, 18 V and 10 A, two pairs (in series) connected in parallel for an input to the FM80 of 36 V and 20 A.
1 FM80
1 Xantrex 2 KW inverter
4 circuit breakers

and 2 6 month old REC panels @ 40 V and 10 A each. Connected in parallel with each other and the older 200W panels.

I have now got all new cables. I have the Victron Smart Shunt and the 60 Amp GCSOAR PWM charge controller as recommended by raysun.

I have the 2 new REC panels connected to the FM80. That setup is currently powering the RV.

I plan to connect the 4 Evergreen 200W panels to the GCSOAR controller, and the GCSOAR controller to the batteries.

I changed from my previous Trojan flooded lead acid E16 batts to the Discover Dry cells because the only place to put batteries in the new RV is connected to the living area. I wanted AGMs so I would not have to deal with cleaning acid off the batteries, creating fumes and general unpleasantness.

The Discover Dry cells are rated at 330 AH. 660 AH total for my 4 at 12 Volts. Max charge current at 20% would be 120 Amps. What the FM80 and GCSOAR can output together.

On #2 above: Discover says 14.7 V for Bulk and Absorb. I currently have Absorb time set at 3 hours
On #3 above: Discover says 13.6 V for float.
On #4 above: Done. Voltages are good. Won't get past this point until I can connect the panels to the GCSOAR controller. Should be next week.

Thanks for all your help on this.