New solar installation - optimization and tips for improvements

sanitariu

Hello dear friends,
finally i did my solar installation.
It is hybrid type and includes the following:

Battery - 4 pieces - CT VRLA - 12v - 150Ah, connected at 24V / 300Ah
Inverter Victron Multiplus C 24V 1200VA
4 solar panels Jinko Solar 245Wp poly
Morningstar MPPT 45 solar controller.

Seems like everything is working perfect and i am doing approx 5000W per day.
My panels are clear of shade and I am at 43 Latitude. Currently they are at 20 degree tilted.
I am discharging 30-40% from the battery and next day i am doing float.

Please give me advise what i can make better ?
Do you think everything is normal for such installation ?
Can i change/optimize something for better ?

BB.

Re: New solar installation - optimization and tips for improvements

Welcome to the forum Sanitariu.

One minor clarification... you are probably generating/using ~5,000 Watt*Hours per day... Watts is a "rate" like kilometers per hour. WattHours is an amount of energy like kilometers driven.

I guess you are in Eastern Europe... Do you have utility power and/or a backup genset for bad weather/when you need more power than the solar system can supply in a day?

You have a "traditional" off grid capable system and the inverter can be configured as a "UPS" (Uninterruptable Power Supply)... That is you can connect to utility power and even recharge the battery bank from utility power, and if the utility power fails, the inverter will "fail over" to battery power and continue supporting the loads.

"Hybrid" inverters systems (as we use the term here) is typically an AC inverter that can do both off grid power and also "grid tied" mode too--Feed excess power from the solar array + battery bank to the utility and even spin your utility meter backwards (when the utility power is working). In many locations, GT Inverter systems are heavily regulated and need building permits/utility approval to connect (and many utilities do not allow GT connected systems).

Your system sounds like it is working well. I would worry that you may not be fully recharging the battery bank, at least, every few days (over 90% state of charge). Sealed Batteries (like your VLRA--probably AGM?) can be a bit difficult to manage. Normally, we would tell people to get a hydrometer so they can measure the specific gravity of each cell's electrolyte to make sure the battery is being recharged correctly.

With sealed batteries, you cannot measure the specific gravity--So you are left with measuring the "resting voltage" of the battery bank to estimate state of charge. One meter that can help you manage your battery bank is a Battery Monitor (such as from Victron). They measure the current into and out of the battery bank using a "current shunt" (and time too)... This lets the meter estimate the amount of Amp*Hours / Watt*Hours into and back into the battery bank.

Most of the hardware for off grid systems are pretty rugged and will last well if not shorted out/connected backwards/etc. However, batteries are not rugged and are very sensitive to use (charging, discharging, failures in cells/cabling). I would suggest that you study up on batteries and ensure that they are being operated correctly so they don't die an early death:

http://www.windsun.com/Batteries/Battery_FAQ.htm
http://www.batteryfaq.org/
http://batteryuniversity.com/

Some batteries (such as GEL type) may have further limits on maximum charging current. And VRLA batteries, in general, are very sensitive to being over charged. Most people probably "kill" their first set of batteries--So reading up on the batteries and understanding their "care and feeding" can give you years more battery life.

I would also suggest that you get a DC Current Clamp meter (this meter is available in the US for very reasonable pricing). It can make debugging/monitoring of DC power systems much easier and safer (using a typical digital meter to measure current, you have to "break" the wires and insert the meter leads--can be dangerous).

Hope I was helpful.

-Bill

sanitariu

Re: New solar installation - optimization and tips for improvements

Thank you very much BB. for your help.
You are correct i am located in Eastern Europe.
5000Wh correct too.
My batteries are VRLA AGM type. I am most scared about them.
As I read the manual they do not need equalization. Batteries are entering in FLOAT almost everyday.
Absorption is approx. at 28.68V. (26 degree Celsius)
In the victron inverter i plugged in also normal AC from the electric company. So when batteries are under 24.55V for 10 minutes,
inverter automatically switches back to electric company. When voltage is over 28.00V for 10 minutes it switches back to battery only.
I am very new to solar and i hope not to screw my batteries

BB.

Re: New solar installation - optimization and tips for improvements

AGM's are very nice batteries--But they are expensive and easier to damage (you cannot replace water if over charged).

Use a volt meter to monitor the voltage of each cell (if possible, or each battery otherwise) and look for "differences". Batteries (especially AGM) usually operate very "well matched" (voltage, current flow between parallel strings, etc.). Any differences need to be looked at and "addressed". One cell that fails shorted or open can damage other batteries in the string. Similar issues can occur with dirty/loose/corroded cables.

This thread (Working FAQ for beginners) has a lot of links to more information about batteries and their proper operation. As well as other solar related projects.

The more I read about batteries, the more I am convinced they will never work.

But--They do work and if you treat them right, they will last for many years.

By the way, why did you choose to "go solar"? Off grid power systems are typically much more expensive than just buying utility power (if it is already available). I have not heard of "unreliable" power in your region that your system would be a nice way to address (at least not yet--what is coming in the future is less clear--North America and Europe included).

Do you have a backup generator yet (if for emergency planning)?

-Bill

niel

Re: New solar installation - optimization and tips for improvements

i doubt you will overcharge anything as you are draining far too much power to suit such a system. the batteries 150ah at 24v is 3600wh and the most these should be depleted would be 1800wh before another full recharge so as to preserve battery life. now this isn't a problem if your pv system is large enough to charge the batteries while supplying excess to the loads. this is not the case as 4 245w pvs is 980w and if derating for real world conditions this is about 755w. this, alone, says that even with 5hrs of full sun that you barely have enough to recharge the batteries and this will be assuming no bad weather and is an optimal season for collection. the term here is deficit charging and you are going to kill those batteries in time. that power to charge the batteries does not equate to enough to run those loads and that is a big red flag.

sanitariu

Re: New solar installation - optimization and tips for improvements

Hi Niel,
may be I did not write correct my batteries.
They are 4 batteries each one is 12 volt 150 Ah, they are connected in parallel/series so total 24 volts - 300Ah. Total I have 7200 Wh.
I am depleting maximum 3000Wh. During day I am gathering approx. 5000Wh. The excess 2000Wh I use for daily loads.
I think I am fine ?

BB.,
I choose to go solar because want to see how things works. Also when i retire i would like to be ready. Other reason is the price. Each year it goes up by 7%
I do not have any kind of generator. My victron have charger. I think if have 10 days with no sun during winter i can charge the batteries from the grid.

If I can add/remove/change stuff to optimize the system will be very good.
Any help is appreciated !

BB.

Re: New solar installation - optimization and tips for improvements

Pretty much, at this point, read about batteries and how to best take care of them. From the day they are made, batteries slowly die. And there are things owners can to that cause them to die faster.

AGM batteries are more difficult to use because you cannot check the Specific Gravity... So you have to monitor the charging/usage/resting voltages closely.

If your charge controller has a remote battery temperature sensor option--Usually it is a good idea to get the RBTS. Battery banks, as they get warm need lower charging voltage (-0.005 volts per cell per degree C @ 25C reference).

There are also different rules we use to try and keep batteries "happy".

For example, don't store under 75% state of charge. Try not to cycle below ~50% state of charge very often ("wear out battery sooner). Do not discharge a battery below ~20% state of charge, week cell(s) can "reverse" voltage and actually begin to reverse charge--usually will kill that cell/battery.

Over charging, under charging, and deep cycling can all reduce battery life. But so can floating at 100% stage of charge for months/years on end... It appears that cycling to 75% state of charge at least once per month is "good" for a battery. Some vendors of industrial batteries would suggest that discharging to 50% SOC once in a while is not bad either.

There are several different suggestions for getting the most from a flooded cell battery bank. One suggestion is to discharge to 75% SOC in daily use, and during bad weather discharge to 50% SOC typical maximum discharge second day (bad weather). If to 50% SOC and more bad weather ahead, recharge battery bank to 80-90% SOC with generator (or utility grid). And try to get to >90% SOC at least a couple times a week (do not try for 100% SOC every day--That is over charging and can be hard on a battery bank).

Another method that can be more efficient for flooded cell batteries is to cycle the battery from 50% to 80% during normal operation and recharge back to >90% SOC every 5-10 days (some vendors may suggest even to every 30 days back over 90% SOC). Sulfation is not supposed to be a big problem if the batteries are actively cycled in the 50-80% rate (daily/every several days of cycling is supposed to not cause "sulfation" problems and Lead Acid batteries are more efficient in this range).

AGM batteries are "different" enough that the above cycling pattern may not be good to extend past 4-5 days before charging >90% SOC before there is a problem with sulfation (sulfation is when the "fluffy" lead sulfate of a partially discharged battery grows into hard/black crystals that are permanently locking away lead and sulfur in the acid/electrolyte from any further discharge/charging chemical reaction).

You might try talking with your battery supplier about how best to manage your battery bank. Batteries are different enough from vendor to vendor that what works for one battery bank may not work well for another brand/different load pattern.

AGM are almost the "perfect" Lead Acid storage battery (clean, very efficient, very high surge current, no electrolyte to check, usually no hydrogen gas released, etc.). But their issues are not trivial. Sensitive to over voltage/over charging. May sulfate faster when stored/cycled below ~75% SOC, expensive, and equivalent quality AGM batteries may not last as long as flooded cell batteries.

Making sure you have the correct charging voltage set points programmed into the AC inverter/charger and solar charge contorllers is critical. And you may need to adjust those voltages for your needs (deeper cycled batteries usually need slightly higher voltages/absorb times). Monitor the charging current and look at where the charging curve tail flattens out (i.e., to less than 2% or 1% of rated battery AH capacity--And AGM may tail out to 0.1% of bank AH capacity--I.e., 100 AH battery bank may tail down to 0.1 amps for AGM--That is when the battery is "full"). Note that as batteries age, that tail current rises... A white paper I read suggested a tail current >2% signifies a battery in trouble and in need of service/replacement (batteries can fail with smoke and fire--always monitor your battery bank for "issues (swollen cases, positive terminals being "extruded" out the top of a battery, hot batteries/terminals/wires, etc.).

I still would suggest a battery monitor if you can justify the price.

http://www.solar-electric.com/metersmonito
http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/rs.html

And read all you can about batteries in general and your batteries specifically.

Good Luck,
-Bill

sanitariu

Re: New solar installation - optimization and tips for improvements

Bill, Thank you for your complete answer !
I will follow your advice and take battery monitor.
I also got battery desulfator.
Remote temp sensor I already use.
Batteries I store in the room where temperature is between 22-28 degree C.
For discharging i will check first what shows the battery monitor. I could not calculate when to disconnect the inverter.
Battery disconnect voltage under use is very difficult. I accept any suggestions for 24 volt system ?

Have another question. Is it possible to add one more 245W panel to my system ?
My panels are connected in parallel and series.

BB.

Re: New solar installation - optimization and tips for improvements

Several ways to calculate the solar array size for the battery bank.

First is based on the size of the battery bank and 5% to 13% to 25% rate of charge (one battery company Representative recommends ~30-35% not to exceed rate of charge:

• 300 AH * 28.8 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 561 Watt Array Minimum
• 300 AH * 28.8 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 1,122 Watt Array Nominal
• 300 AH * 28.8 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,459 Watt Array cost effective" Maximum
• 300 AH * 28.8 volts charging * 1/0.77 panel+controller derating * 0.25 rate of charge = 2,805 Watt Array not to exceed

Another maximum seems to be ~1,000 watts of solar array per 100 AH @ 48 volt battery bank (or 500 watts per 100 AH @ 24 volt, etc.). What appears to happen with at least some MPPT type charge controllers is that charge controllers can "overwhelm" the battery bank with charging current during MPPT sweeps (or possibly changes in load current/clouds passing in front of sun, etc.) and take the batter out of its normal operating range (battery bank actually is the "voltage regulator" and if you feed a fully charged battery with excessive current, you can pull the battery voltage >72 volts on a 48 volt system with a very large solar array). So the (rough) maximum for your system based on this issue would be. This is not a "hard limit" but one to watch out for as at least one MPPT charge controller seems brand has been reported with this instability (too large array for battery bank):

• 500 watt array per 100 AH (on 24 volt system) * 300 AH battery bank = 1,500 Watt Array

So, there is a "grey" zone between ~1,500 Watt to 2,805+ watt array on your present system where you could have issues if you went "with a very large" array.

Another limit is the 45 Amp MPPT controller current limit. The controller can easily and safely take a "very large" array, but it becomes a "waste" as the MPPT charge controller limits it output current to 45 amps maximum (clips array output during the middle of the day). You can go larger, and will will get more power during the mornings/evenings, but it is a diminishing return on your money/investment without going with a larger array. Also, the battery bank charges so quickly with a very large array, that the battery bank simply sits at "float" for most of the day unless you have a lot of day time loads to use the excess energy (irrigation, day time home loads, etc):

• 45 amps * 28.8 volts charging * 1/0.77 panel+controller derating = 1,683 watt "cost effective" maximum array based on 45 amp MPPT controller limits

You have a 980 Watt array, so you can add some panels pretty nicely. The issue with your system, I assume is that it is 2 panels in series and 2 strings in parallel.

You would need to add two more panel at a time (not one) to wire up for your charge controller. If I have the right Jinko 245 watt panels (PDF spec.), Vmp~30.2 volts. Typically your "acceptable" input voltage for your controller should be around 2-3 panels in series... 1 panel has too low of voltage (Vmp=35 volt minimum recommended) and 4 panels could over voltage the controller input on very cold/clear winter days--around 140-150 VDC input for typical higher end MPPT controllers).

If you put three or more parallel strings together for a solar array, you usually need to install a fuse/circuit breaker per string to prevent a shorted solar panel from being fed too much current from the other panels in the array (15 amp breaker/fuse for this solar panel). A solar combiner box with fuses/breakers is one way to do that (sort of a "reverse connected" main power panel--current comes in on the branch circuits and goes out the main bus).

Regarding the Battery Desulfator--I am not a big fan of them (some people think Desulfators work well, and others do not think desulftators do anything). In any case, desulfators "work" by making a lot of electrical noise (current spikes). It has been seen that the electrical noise can cause problems with attached equipment (electrical interference) and at least one poster here has seen the desulfator drop the output current from the MPPT battery charge controller--So make a comparison of the MPPT charge controller's output current with the desulfator on and off--And make sure it does not cause your MPPT controller to reduce current/turn off prematurely.

Lastly, battery voltage is a very difficult way to judge when to to turn off loads... We usually start with ~11.5 volts under load (23 volts for 24 volt bank, 46 volts for a 48 volt bank) as the cutoff voltage as the starting point. If you have large surge loads (well pump, etc.), then you may need to reduce your cutoff voltage a bit (some controllers will qualify the minimum voltage for a couple minutes to allow current surges for starting equipment).

-Bill

BB.

Re: New solar installation - optimization and tips for improvements

By the way, I would also read this article about wiring of your series/parallel battery bank. You want to insure that the batteries always properly share current/loads/charging energy.

If you "wire the batteries" wrong, one string may get most of the current charging/discharging while the other strings do less work. And the batteries will wear out/fail at different times (plus the "useful energy" stored by your battery bank will be less.

Believe it or not--I am just about out of anymore things I can say/suggest about your system if it is otherwise working well for you.

-Bill

sanitariu

Re: New solar installation - optimization and tips for improvements

I got my victron bmv monitor and everything is connected now.
I calibrated the monitor for 300Ah battery.
Seems like i am using approx. 25-30% from my battery. SoC is 65-70% showing 114Ah daily usage.
Next day i am making 100% full again.
The strange thing is that morning star is staying too long in absorption mode. It stays for 340 minutes or times like that and almost never goes in float mode.
Do you think that these absorption times are normal ?
Morningstar MPPT 45 have default settings.
I read somewhere on the forum that may be battery voltage sense is not correct. Is it possible ?

Coach Dad

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

I got my victron bmv monitor and everything is connected now.
I calibrated the monitor for 300Ah battery.
Seems like i am using approx. 25-30% from my battery. SoC is 65-70% showing 114Ah daily usage.
Next day i am making 100% full again.
The strange thing is that morning star is staying too long in absorption mode. It stays for 340 minutes or times like that and almost never goes in float mode.
Do you think that these absorption times are normal ?
Morningstar MPPT 45 have default settings.
I read somewhere on the forum that may be battery voltage sense is not correct. Is it possible ?

Hi Sanitariu
If battery voltage discharges below 12.50 Volts (25.00 Volts @ 24 V, 50 Volts @ 48 V) the previous night, Absorption charging will be extended on the next charge cycle by 30 minutes. That is the Absorption Extension time.
If the battery bank discharges below 11.50 Volts (23.00 Volts @ 24 V, 46.00 Volts @ 48 V) the previous night, Float charging stage will be cancelled for the next charge cycle and it will stay in Absorption.

You can set up your Morningstar with custom values for each parameter by using the free MSView software which is available on the Morningstar web site.

sanitariu

Re: New solar installation - optimization and tips for improvements

I am discharging to 24.44 V under load and after rest battery returns to 24.75 V.
Is it normal to have almost each day absorption times like 300-350 minutes ?
I think is too much.
My batteries are AGM and i can not measure other way.
I just afraid not to overcharge or undercharge.

Coach Dad

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

I am discharging to 24.44 V under load and after rest battery returns to 24.75 V.
Is it normal to have almost each day absorption times like 300-350 minutes ?
I think is too much.
My batteries are AGM and i can not measure other way.
I just afraid not to overcharge or undercharge.

No 300-350 minutes is not normal. Here is the Absorb times chart from the manual.
Attachment not found.

sanitariu

Re: New solar installation - optimization and tips for improvements

Yes i read the manual.
I have battery voltage sensor and temp sensors connected.
I suspect battery voltage sensor like starting absorption too early before reaching 28 volts.
Anyone have similar problems ?
How much is normal or maximum time 2 hours + 30 minutes extended ?
I can not use end amps because i have load running during charging.

BB.

Re: New solar installation - optimization and tips for improvements

What is the charging voltage at the battery bank terminals?

Short/heavy cables between charge controller and battery bank (you are using remote sense leads? Probably connected)?

-Bill

Coach Dad

Re: New solar installation - optimization and tips for improvements

Coach Dad wrote: »

.

You can set up your Morningstar with custom values for each parameter by using the free MSView software which is available on the Morningstar web site.

As I stated earlier, you should go the the Morningstar web site and install the FREE MSView software.
If you use that software, you can customize EVERY parameter

If you don't want to use the MSView software, then I suggest that you reboot the charge controller and see what happens.

sanitariu

Re: New solar installation - optimization and tips for improvements

This is what i got early in the morning around 09.00 AM.
0.2 Volt difference.
The more power goes in the more difference.
Note: Inverter is switched off ! I have 0 load.
My cables from controller to battery are 35mm2 which i think is pretty much enough.
Do you think i must remove battery voltage sensor ?

Attachment not found.

NorthGuy

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

This is what i got early in the morning around 09.00 AM.
0.2 Volt difference.
The more power goes in the more difference.
Note: Inverter is switched off ! I have 0 load.
My cables from controller to battery are 35mm2 which i think is pretty much enough.

If you get 0.2V drop at 16A then the resistance of your cables is 0.2/16 = 0.0125 Ohm.

35mm₂ is about #3. Assuming your cables are made of copper, to get this sort of resistence you need about 60ft of them. Are they that long?

BB.

Re: New solar installation - optimization and tips for improvements

35mm2 wire should be plenty heavy--How long are they (between charge controller and battery bank)?

Ideally, the battery charger will feed 100% of available current to the battery bank when the sun comers up... The battery voltage will rise as the batteries become more charged and as you receive more sun (bulk) until the charging set point is reached (say 28.6 volts @ 25C)--At that point the charge controller will limit battery bank voltage to ~28.6 volts for the absorb period. After XX amount of time, the charger should drop back to float (~27.2 volts or so).

With AGM/Sealed batteries, they are very sensitive to over charging... Holding them at ~28.6 volts with room temperature batteries is probably not going to be a huge issue (yes, need to understand what the controller is doing). But is you are not reaching your set point, or going over your set point--That can harm your batteries over time.

So, exactly what voltage are you seeing at the batteries when charging--And what temperature are they at?

-Bill

sanitariu

Re: New solar installation - optimization and tips for improvements

My cable is 1 meter long. From charge controller to the battery.
From inverter to battery is 1 meter too.
All temperatures and voltages you can see at the picture i attached 2-3 posts below.
I think controller is going in absorption too early. And stays too much. Almost never goes to float.
Yes i can go and setup other times manually but i must be sure what i am doing.
I think the problem is:
Battery terminal voltage - 26.33
Battery sense voltage - 26.13
I have no load when i measured these voltages. Inverter was off. Cable is 1 meter 35mm2 /copper/.
These voltages must be equal i think ?

BB.

Re: New solar installation - optimization and tips for improvements

26 volts for "no charging/discharging" resting is a pretty full battery.

What I am now interested in--When the solar array is charging, what does the battery voltage and current look like--Something like this:

6am - 25.0 volts; 0 amps (no charging current)
9am - 26.3 volts 10 amps (early sun, bulk)
10am - 28.0 volts 27 amps (lots of sun, bulk)
12pm - 28.4 volts 18 amps (lots of sun, absorb)
13pm - 28.4 volts 6 amps (lots of sun, absorb)
14pm - 28.2 volts 3 amps (lots of sun, absorb)
15pm - 27.2 volts 1 amps (lots of sun, float)
etc...

-Bill

Coach Dad

Re: New solar installation - optimization and tips for improvements

The Tri Star MPPT will stay in Absorb for as long as you have set in the program....
So if the controller is staying in absorb for 300-350 minutes, I would be courous as to what your setting is.
If you go toe the setup wizzard and select "Read TSMPPT" you should get a screen that looks like this.
Attachment not found.

What is the "Absorption Time" set to?

sanitariu

Re: New solar installation - optimization and tips for improvements

Coach Dad I am attaching picture.
BB i will take notes with 4-5 measures.
First is from now. I have only load, no charging. All voltages must be equal I think.
Even with temp compensation i can not do 0.2v difference.
See attached pictures.
Thank you people for your time and help !

Attachment not found.Attachment not found.

NorthGuy

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

Even with temp compensation i can not do 0.2v difference.
See attached pictures.
Thank you people for your time and help !

Apparently, the cables are not a problem because the voltage difference is there whether you have a charging current or not. I'd say it's just a measurement error. I wouldn't worry about this.

Coach Dad

Re: New solar installation - optimization and tips for improvements

Hi Sanitariu-
Your Max Compensation Temp is set to 80C (176F). I don’t think it will ever get that hot :cool:. I suspect, that's the cause of your problem.
Let’s run a test.
Please make the following changes to your settings and see if your system goes from Absorb to Float.
Change your Max Compensation Temp to 40C (104F)
Change your Min Compensation Temp to -25C (-13F)
Change your Absorption time to 30 minutes
Change your Absorption Ext time to 30 minutes
Reboot the Controller after making the changes.

Your system should go through the bulk charge, switch to Absorption for 30 min and then go to float…
If this works, then you should go back and adjust your Absorption and Absorption Ext times to their previous settings.

sanitariu

Re: New solar installation - optimization and tips for improvements

Here is what i have.

battery voltage only load - no charge
Battery Terminal Voltage = 25.24 V
Battery Sense Voltage = 25.15 V

battery voltage 9 morning - only charge, no load
Battery Terminal Voltage = 25.76 V
Battery Sense Voltage = 25.64 V

battery voltage 12 clock - charging, no load
Battery Terminal Voltage = 27.82 V
Battery Sense Voltage = 27.56 V

battery voltage 16 clock - charging and load
Battery Terminal Voltage = 28.75 V
Battery Sense Voltage = 28.53 V

Temperature is 28 degree. Cable is copper 1 meter 35 mm2. I see difference 0.3 V which even
with temp compensation will be 0.18.

The other problem i noticed is that voltage was put for 28 V on my morningstar controller.
I checked my battery pdf manual and for 25 degree C I must charge with 28.5V.
Seems like i was undercharging with around 0.8 V ?
The other problem was absorption time. It was 2:30 hours + extended 3 hours more, so total 5:30 hours.
I corrected to 2:30 hours + extended 30 minutes.
So what do you think people ?
Did i make the correct things ?
Voltage 28.50 cycle charging
Absorption total 3 hours.

NorthGuy

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

Here is what i have.

battery voltage only load - no charge
Battery Terminal Voltage = 25.24 V
Battery Sense Voltage = 25.15 V

battery voltage 9 morning - only charge, no load
Battery Terminal Voltage = 25.76 V
Battery Sense Voltage = 25.64 V

battery voltage 12 clock - charging, no load
Battery Terminal Voltage = 27.82 V
Battery Sense Voltage = 27.56 V

battery voltage 16 clock - charging and load
Battery Terminal Voltage = 28.75 V
Battery Sense Voltage = 28.53 V

This is sort of opposite of what you posted before. In the numbes you posted now, there's a clear differemce. Voltage is the same without charging, but when you charge the difference between voltages appears. This is definitely the cable. Either it is too thin, long, or perhaps connections are not good. You can check it with multimeter. Do you have a multimeter that could measure voltages in the 0.1-0.3V range?

sanitariu wrote: »

The other problem i noticed is that voltage was put for 28 V on my morningstar controller.
I checked my battery pdf manual and for 25 degree C I must charge with 28.5V.
Seems like i was undercharging with around 0.8 V ?

It only reached your absorption voltage (28.5V) at 4 p.m. That is when the absorption starts. Befire that, it was bulk. It should keep 28.5 for another two hours (or whatever you want the absorption to last).

During bulk, batteries can take a lot of charge and therefore all the charge you put in is not enough to increase the battery voltage to your 28.5. This may be hours.

Once 28.5V is hit, the absorption starts. It differs from bulk in that the controller now dials down the charging not to exceed 28.5V. It lasts for some time, and then when it's enough, controller goes to float. If absorption starts at 4 p.m., it may not be enough time to go to float.

sanitariu

Re: New solar installation - optimization and tips for improvements

No, no ... you did not understand me.
Voltage always drop charging / load or not.
The more voltage goes high we have more drop. Cable is clear copper 1 meter long 35mm2. All connections are perfect.
So i suspect here M*. If someone have similar experience, please let me know.
The other problem is absorption time.
You did not read my post, so i will give you link.
http://free.gorna.net/sol

Check absorption time for today.
I think i set it for maximum 2 hours and 30 minutes + 30 minutes but it is more than 5 hours.

NorthGuy

Re: New solar installation - optimization and tips for improvements

sanitariu wrote: »

No, no ... you did not understand me.
Voltage always drop charging / load or not.
The more voltage goes high we have more drop. Cable is clear copper 1 meter long 35mm2. All connections are perfect.
So i suspect here M*. If someone have similar experience, please let me know.
The other problem is absorption time.
You did not read my post, so i will give you link.
http://free.gorna.net/sol

Check absorption time for today.
I think i set it for maximum 2 hours and 30 minutes + 30 minutes but it is more than 5 hours.

On voltage drop.

There's Ohms law: Voltage = Current * Resistence.

When you don't charge, current is zero, so voltage difference is zero too. That's what you see, which tells us that measurements are correct.

When current goes up (charging), this causes voltage difference.

We can re-write Ohm's low like this:

Resistance = Voltage/Current.

Voltage difference is 0.3V. Current is, say, 20A. This gives us:

Resistance = 0.3/20 = 0.015 Ohm = 15mOhm.

7ft of #3 wire are supposed to have resistance of 1.4mOhm. Your resistence is 10 times bigger. Why? It's either a bad wire or bad connections (or perhaps a bad breaker). If you have a precise multimeter (voltmeter) I can tell you how to check what's wrong.

0.3V is not such a terribly bad voltage drop. Shouldn't cause problems.

On absorption time.

It think it displays bulk+absorption. There must be people who use this controller who can say if that's so.

Can you measure it directly? Mark the point when your battereies reach 28.5V (temperature adjusted). This is the start of the absorption. Then mark the point when it is so dark that the voltage is no longer 28.5V (temperature adjusted). This is the end of it. What is the difference?

Cariboocoot

Re: New solar installation - optimization and tips for improvements

There have been other posters who have noticed that MS's battery sense system does not work properly on their controllers. There could be an issue with the system (other than it doesn't function logically - another argument) or it could be a wiring fault (btw the negatives are tied together). The solution seems to be to not use it, and compensate manually. Since the Voltage difference is at its maximum under high current, the issue is not a large one in that respect. Most charge controllers don't have this feature, and yet manage to get the job done. I guess people just make sure the charging cables are large enough and leave out the V-sense connections. Some programming change is required to ignore the sense input.

IIRC, MS Absorb is a fixed time and has an "Absorb extension" function. So the time will not include Bulk stage time. To my mind this is another operational shortcoming. If the OP has it set for 2.5 hours Absorb and 30 minutes extension it should not run longer than 3 hours at Absorb Voltage. This is where you check the programming twice, measure the Voltage with a DMM, and then consider the possibility that the unit is defective.

If it is, try and get a refund and invest in a MidNite or Outback. Seriously, when it comes to MPPT controllers those two are functionally superior to all the others.