pictonrose: 6 year old system--Now with some upgrades--But not working well?

System

This discussion was created from comments split from: Determining Batteries State of Charge.

pictonrose

I recently joined this forum. I'm having problems with loosing power overnight. I have been off grid for 6 yrs. It was all installed by a local installer of solar, we added more panels last ur and upgraded the genie to 5kw. Solar array is now at 5 kw too. Have outback 80 charge controller and xantrex inverter 24, 2v batteries = 48v. Last 4 months we r waking up to 47.2 or less VDC. In the years past it was 48.4 or better VDC. we checked the batteries, they seem good. Not sure what the problem is, any ideas.

BB.

Welcome to the forum Pictronrose,

I have moved your question to your own thread/discussion... That way we can focus on your Q&A without confusing the original poster's discussion.

Can you tell us a bit more about your battery bank? Brand/model of batteries (FLA, AGM, etc.)?

What specific model of Xantrex inverter-charger (link to model)?

Do you know how much energy you use overnight (AH or Watt*Hours)?

Have you measured the charging voltage on the bank (something like 59.0 volts, held for 2-6 hours--longer time for deeper discharge)? Specific Gravity of all the cells (if Flooded cell Lead Acid) after charged, and in the morning before charging?

Have you used a voltmeter to measure the voltage across each cell? (looking for any cells that do not match voltage during charge and discharge).

What is your peak charging current that you have seen from your solar array... More or less, the peak charging current (cool/clear weather, near solar noon):

• 5,000 Watt array * 0.77 panel+controller derating * 1/29 volts charging = 133 Amps

Do you have 2 Outback FM 80 charge controllers?

Of course the maximum charging current is dependent on lots of things... Battery state of charge, any DC Loads, Charge Controller mode (bulk, absorb, float), etc...

-Bill

pictonrose

Batteries AGM 2V, Outback flex max 80
Xantrex sine wave plus inverter/ charger model # swplus5548
24 panel - (12 on the roof, 12 on an A frame) 2 different brands
Magnum 5 kw generator

I dont know how much power I use overnight, how do I tell that?

We checked the battery bank with a volt meter a couple of months ago, seemed as though all the batteries were the same, roughly. Didnt know I should check when charging. A little afraid of my battery bank. We checked batteries with inverter off. 

Are u talking VDC, closes we got was 58.9, sometimes it says charged, sometimes absorbing, sometimes bulk.

Not sure what u mean about peak charging current at noon. The inverter will read 57.8 or so, inverter say it's taking in 98V or more depending on the day. I dont think I know the amps.

I only have 1 outback 80.

How do i check outback for DC loads? Not sure. Whenever i think i know something about my system, something happens and i realize i am solar illiterate. 

Thank you for moving my post, i couldn't figure out how to start a chat.

Thanks again Bill for your response

Photowhit

It's always a little difficult with AGM batteries to determine the State of Charge (SOC).

It will be even hard for us 'looking through the internet' at your system. So we'll ask a bunch of questions.

AGM batteries will come in 2 sorts, one is designed for daily cycling the other is designed to be held in float for many years and come to the rescue if there is a grid failure. So the specific brand label would be nice. We'll also like to know the size of the battery bank, so if you can see an amp hour rating it might say 200 ah or spell it out.

pictonrose said:

"... we added more panels last ur(year?) and upgraded the genie to 5kw. Solar array is now at 5 kw too."

So did you do this in response to having problems or was it planned ahead to add some loads?

What are your normal loads over night, Fridge? Freezer? Clock Radio? TV? Computers? Haven't added any think like a space heater, electric blanket or mattress warmer? CPAP? Drink Coffee at night?

Days are getting shorter, and we'll want to look for new loads run at night, So have you changed anything?

pictonrose said:

...Last 4 months we r waking up to 47.2 or less VDC. In the years past it was 48.4 or better VDC...

Certainly very low for a constant low low voltage. So when you take this measurement, what loads are running Is this while the coffee machine and toaster are on? What you are seeing is the system voltage. So loads will effect the voltage you 'see'. A coffee machine and toaster will draw more than 1 kWh total or 1000 watts and will cause a sag to system voltage you 'see'.

pictonrose said:

Are u talking VDC, closes we got was 58.9, sometimes it says charged, sometimes absorbing, sometimes bulk.

Not sure what u mean about peak charging current at noon. The inverter will read 57.8 or so, inverter say it's taking in 98V or more depending on the day. I dont think I know the amps.

I only have 1 outback 80.

So we are looking for the system to reach Float a few days a week. 

This is the basics of charging;

The voltage you are seeing is the system voltage and not the battery voltage. If you are connected to charging or a load it will effect the system voltage.

During charging, there are basically 3 stages of charging, Bulk, Absorb, and Float.

BULK;

First thing when charging starts you will be in bulk, the voltage rises from what ever the system voltage was to a set point, around 14.5 volts. At that point the Charge controller stops the voltage from rising. Higher voltage can damage sealed batteries.

ABSORB;

Once the battery hits the preset point the charge controller keeps it at that point. Your batteries are roughly 80% full. Flooded batteries will start accepting less current at 80-85% full AGM/Sealed may go a little longer before accepting less current.

On many controllers you can set this point, Some will have different presets for Flooded, and sealed batteries, or flooded, AGM, and sealed batteries. 

The charge controller has a couple ways to know when to switch to float, Most inexpensive Charge controller are just timed for 1.5-2 hours. Some will also see less current flowing through the charge controller and shut it down when minimal current is flowing through the controller. On more expensive charge controller. You can set battery capacity to give the Controller a better idea of when to stop. you can also set a longer Absorb time. Or set 'end amps' a amount of amps flowing through the charge controller to stop Absorb and switch to the final stage.

FLOAT;

Once the Controller has determined the battery is fully charged it reduces the voltage to a point where very little current is flowing to the battery. This will prevent the battery from over charging and heating up.

While in 'Float' the charge controller watch for voltage drop, which would indicate a load. If the voltage begins to drop the charge controller will allow as much current to flow from the panels/array to compensate and maintain the voltage. If the voltage can be maintained, the load will in essence be running directly off the array/solar. If the voltage drops below the preset float voltage, the controller may start a whole new cycle if it stays there for a period of time.

The system voltage drop you see at night when the sun goes down is the charge controller moving into a resting mode with no energy to contribute to the system.

The morning voltage may reflect a load present that is effecting the voltage level. With sealed batteries, you would want to disconnect the battery from the system and allow it to 'rest' for a while to get an accurate idea of it's SOC (State Of Charge) from the voltage.

Charge Controllers

So you have a 5000 watt array and a single FM80, in general this isn't awful, but pushes the limits of the FM80. I think the FM80 can be over panels a bit, but might be better to split it up.

Basically you can expect a 5000 watt array to regularly produce about 75% of that or 3750 watts, Charging a system that is at 47.2 volts It will likely present around 52 volts. Amps x Volts = Watts it's the basic equation we use for a lot of things. So 3750 watts/52 volts = 72 amps so near the limits of your charge controller. In the cold mornings if the sun hits at a good angle it can reach 5000 watts and exceed the charge controllers capacity. 

You should learn the setting of the FM80 and be able to check to see what stage of charging the controller is in. Likely you should increase the absorb cycle time on your charge controller as well. as batteries age this is helpful. But start with your battery manufacturers specs.

I don't know if you have your generator setup to auto start, I would suggest starting it if you see your batteries with minimal loads going down near 48 volts. Particularly if you know you will be having cloudy days.

Batteries like to be 80% or better, if they stay lower than 80% for any extended time they will start to sulfate. AGMs like to have a sustained charging at near their Absorb voltage to help equalize the cells, your battery manufacturer likely has information about how to do this.

DO NOT USE the FM80 or inverters equalizing methods, they are likely for flooded batteries and may destroy AGM batteries.

pictonrose

AGM batteries will come in 2 sorts, one is designed for daily cycling the other is designed to be held in float for many years and come to the rescue if there is a grid failure. So the specific brand label would be nice. We'll also like to know the size of the battery bank, so if you can see an amp hour rating it might say 200 ah or spell it out

C&D Technologies M.S.E.
MSE 1440 2V, 1440ah @ 8hr to 1.75V
Constant Voltage Charge 2.23-2.25V 

We added more panels to hopefully decrease genie use. We upgraded the genie as we were using gas, the genies had short lives, and the winters can be cold. We have fridge, 3 freezers, toaster only used on sunny days, no coffee maker, computers are used threw the day, then unplugged, my phone is mostly my computer these days so I rarely use the desk top model anymore. Usual TVs, etc. I dont use anything with an element in it, except the toaster. Propane stove, dryer. Our well pump draws 1kw, but not always running, bought an extra large pressure take to reduce it coming on.

Apparently our system is closer to 6kW, the first set is less than 3kW and the second set is just over 3kW. The charge controller is apparently designed to dump the excess power once it has reached its 5kW capacity in the battery bank.

Probably need to invest in another charge controller and split the panels. I dont know or think I have used the equalizing methods. 

We generally start the generator before it gets to 48.4, we recently have been waking up to these lower numbers. No autostart yet, still deciding if it will work when its bitter cold. Sometimes in winter it gets -47 degrees Celsius. This year we built a log genie shed and installed a woodstove so we can keep it warm during the coldest days.

I'm not sure if that's everything. Thank you for the reading on the different meanings. Will print off a copy for future reference.

BB.

OK... I used a 24 volt battery bank--Missed the 47.x volt (sorry) when typing the equation below... The typical max from your array:

• 5,000 Watts * 0.77 panel+controller derating * 1/57.6 charging (typical AGM) = ~67 Amps max from FM 80

So--The single controller is OK.

Measuring voltage on a battery bank with a DMM (digital multimeter) is pretty safe. Whether the inverter is running/charging/etc. or not does not matter... It only changes the battery bank voltage a little bit (ranges from ~46 volts to 58 volts or so).

With AGM batteries, watching the battery bank overall voltage:

• more or less, under 50.8 volts is discharging
• over ~56.0 volts is charging
• around 53.2 to 54.8 is "floating" -- batteries typically fully charged and just being "maintained" and supplying current from FM 80 to your loads during daylight hours)...
• Under ~46.0 volts (I had 44.6 volts--That was not right. -BB)--You are getting the bank fairly discharged--Reducing loads and/or starting a genset may be a good idea

Photowhit does a very nice job of describing the stages of charging... I am guessing that "Charged" on your controller = "Floating".

When working on a battery bank--Removing all rings and jewelry (pendant, chains, etc.). And if you use any tools (wrenches, etc.), wrap electrician's tape around the handles so that they cannot short out (electricians will rewrap their tools for every job to makes sure the tool handles are always insulated). You can wear a face shield if you wish (or safety glasses)--Generally with just using a DMM, you are not going to cause a spark or short circuit if you watch what you are doing).

Ideally, you want a volt meter that will read 59.xx digit accuracy. And 2.xxx volts when measuring each cell. You want to log your readings (at least once a month) so you can see patterns. The voltages will depend on the current/state of charge, and even temperature...

This article is for flooded cell batteries--But the idea is very similar for AGM batteries too:

http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

If you do not have one, I highly suggest getting an AC+DC Current Clamp DMM (digital multimeter). The current clamp is very safe and easy to use. Just "zero" the meter, and clip on one of the wires. Here are a couple examples (links are suggested starting points--This two meters have been used by folks here--But there are many others too):

https://www.amazon.com/UNI-T-Digital-Multimeter-Current-Capacitance/dp/B078PDNS27 (cheap, good enough for our needs--100 amp current limit)
https://www.amazon.com/gp/product/B019CY4FB4 (mid-priced, very nice meter--400 amp current limit--Better for larger systems).

Note there are both AC only current clamp meters (with AC+DC voltage function) and AC+DC Current Clamp DMMs... AC clamp meters are great--But we need the DC clamp meter function for working with batteries.

And look for both price and availability--These meters have been all over the place for price and availability because of COVID and trade issues.

The other issues--Lead Acid/AGM batteries can be damaged if under charged/over discharged... So you want to keep an eye on the battery bank voltage and make sure that all is working correctly/as expected.

And a 6-7 year life for an AGM battery bank is not a bad service life... Lead Acid (and AGM) do eventually sulfate (the fluffy lead sulfate turns into a black/hard crystal--Which no longer participates in the charge/discharge cycle). Undercharging/letting battery sit uncharged (less than 75% state of charge) will accelerate sulfation (AGM are supposed to sulfate less than FLA batteries). 

Also many AGM batteries have a catalyst in the cap/top of the cells to combine Hydrogen+Oxygen back to water... That catalyst does have a lifetime. Charging/gassing slowly decays the catalysts--And then eventually the cells can start to vent hydrogen+oxygen gasses. Note that overcharging (gassing) the batteries can overheat the catalyst too (and shorter cat. life).

There are meters you can hang on the battery bank to help you understand the AmpHours in and AmpHours out, and state of charge of the bank... But lets start with the basics first (a good quality voltmeter or AC+DC Current Clamp DMM).

-Bill

pictonrose

Thanks Bill, will get a volt clamp meter and get back to u. The worst number we saw was 46.6. Lately its 47.2 or so, so hopefully we haven't done too much damage. 

BB.

By the way--I made a mistake in post #7... The concerned voltage is roughly 46.0 volts (not 44.6) or below for a 48 volt battery bank... I cannot multiply 11.5v (12 volt battery bus) * 4 and get the right number anymore without using a calculator. 

Lead Acid battery voltages are very loose estimates vs State of Charge...

-Bill

Photowhit

So you perhaps looked up the battery when I suggested there were differences I didn't read much when I found the 'PDF instructions for the battery bank; The title pages says;


Here's a link;

https://cdtechno.com/wp-content/uploads/2020/04/12_386_mse.pdf

I will hunt around later, they don't talk about cycles, but my guess is they will only cycle to 50% SOC a few times <200. I would NOT have recommended them for daily cycling solar electric system, it is far from their intended use.

It does appear they have a 7 year full warranty on them, so perhaps there might be some recourse. Going after your installer (in Court not with a pitchfork) might be an option as well.

Photowhit

It appears that exact model has be discontinued. I found a current AGM line instruction manual. Unfortunately it includes information such as;

"Standby batteries such as the msEndur II are designed and constructed to provide long life in continuous float service. They differ in their design from cycling batteries, such as engine starting, solar or traction types."

and

"As such, standby battery life is directly affected by and will be degraded if subjected to repeat cycling. Depth of discharge, number of discharges, rate of discharge, and the interval between discharges are all determining factors in battery life. Cycling should therefore be kept to a minimum."

Link to manual;
https://cdtechno.com/wp-content/uploads/2020/04/rs_02044_1214.pdf

This might be better info, It's a manual for C&D Liberty MSE and DCS batteries. Includes the info;

"The Liberty MSE series is designed for float operation with minimal cycling. Typical applications include Telecom, Switchgear/Control and other non-UPS applications which are subjected to 20 or fewer cycles per year.

The Liberty DCS series is designed for cycling applications. Typical applications include OffGrid/Unreliable grid Telecom, Renewable energy or other stationary applications requiring a high number of cycles throughout the life of the cell."

There is info on recuperative measures by maintaining the float voltage for several hours. Perhaps it will help maintain some capacity for a while.


Link to manual;

https://cdtechno.com/wp-content/uploads/2020/04/rs_02109_0914.pdf

Since this manual is also for DCS batteries, I was hoping it would have some cycling information, but it doesn't.
I'm use to seeing graphs of number of cycles to expected battery life.

HUP Solar does a chart of types of Flooded lead acid batteries and their expected life discharged 80% (20%SOC)
I couldn't find a chart for your MES batteries, but suspect it's much like the 'lower lead calcium plate 'marine' batteries.



Since you aren't using them to 20% SOC, they have lasted longer...

These would be great batteries for a grid tied hybrid system, where their low discharge rate and long life while only in float would make an excellent choice. They wouldn't be cycled unless the grid went down.