Jump to content

Batteries failing


ProjectGKR

Recommended Posts

Hello

Hoping someone can help me troubleshoot or guide me in a direction on why I am losing batteries on my system. My current batteries are not even 2 years old and I have already lost 5 out of 12 baterries, so I am now down from 3 banks to 1.

Some details are as follow:
-Battery: Sonx 12v 200Ah AGM
-Mppt: 2x 60A Microcare (9 panels each)
-SolarPanels 18x 300W 24V panels (9 facing east and 9 facing west)

The Mppt's settings are as follow:
1. Boost Voltage = 14.5V
2. Float Voltage = 13.6V
3. Equalize = Manual
4. Boost to Float Change interval Scan  1hour 
5. Boost to Float Change If charge  < 6 amps

Yesterday I did notice that during Boost on the single remaining battery bank (no Load), with Mppt showing 58V and amps around 10A that 1 battery was charing at 15.6V, 2 of them at 14.5V/14.3V and the last at 13.8V. After swapping some of the batteries around I only manage to get the voltages to be 15, 14.5,14.3 & 14.9 during boost.

I am thinking of just getting 1 new battery just to get back onto 2 banks atleast.

The previous set of battries also only lasted 2 years, The previous set was Torjan 6v battries and lost al 16 of them

Thanks
 

Link to comment
Share on other sites

Good morning,

I can't really tell in your particular case, but in my experience there are 2 main reasons why most lead acid batteries fail early, this is either from being under-charged or over-charged.

They can be under-charged if they spend a long time in a partially charged state. This can often happen in off-grid systems when there is not enough PV to fully recharge the batteries every day, especially in winter for example. In this case you will get sulphation of the plates and the battery life will be reduced.

Over-charging for a long time especially at high temperatures can cause some electrolyte loss, which is fine for flooded batteries that you can top-up, but with sealed batteries this is a big problem that will reduce the life of the batteries.

Link to comment
Share on other sites

Hi ProjectGKR

There is only one thing I can see that might contribute to loosing battery banks so quickly, you might be undercharging them. Let me explain. 

You have a 600Ah Bank, that is 28.8kwh of available power. And you have 18 x 300Watt panels that give you 5400whp and you can expect to get 4320whp after losses. Now lets say you use 50% of your battery power at night that will be 14400wh and with your available power from the panels it will take 3.3 hours to recharge your bank. This is if you dont use any other loads during the that time.  

 

1 hour ago, ProjectGKR said:

The previous set of battries also only lasted 2 years, The previous set was Torjan 6v battries and lost al 16 of them

This is also an indication that something is wrong. Loosing trojans after 2 years is not normal. They normally last 5 years or more. 

What is your charging current set at, and for interest sake did you ever attempt equalization on these specific batteries?

Link to comment
Share on other sites

Hello

 

Thanks for the Feedback.

Jaco de Jongh The System is still connected to Eskom. I am using a 5kw 48V Microcare inverter. The inverter is set to switch to Eskom at 48V and then Go back to Battery on 54V. Also the Charger is turned off on the Inverter.

With the Trojans I did set it to auto equalize and also once a month after doing maintenance on the Trojans (water top up) I did force the mppt's to equalize. With the AGM batteries I was instructed to not equalize them.

I am not sure where to check the charing current on the Mppt's.

 

Link to comment
Share on other sites

11 minutes ago, ProjectGKR said:

The inverter is set to switch to Eskom at 48V

Do you have a battery monitor and do you maybe know how many Ah you use during the night? 

On a bank that big and expensive its crucial to have a battery monitor at least and battery balancers can also help you to rectify this imbalance. 

Link to comment
Share on other sites

I have no batery monitor. I know from the last couple of days I use around 4-5 kw units during the night, with my daily average about 17 kw units

When the installer designed the system, they never mentioned the use of balancers, even when I had to replace the Trojans, no mention was made about it, I am only now learning about it (and I am paying very expense school fees currently with lessons learned)

It all seems like the fact that I have no Battery Balancers is the cause that I am losing batteries

Link to comment
Share on other sites

Hello

So I am just trying to make sure I understand how to install th Victron balancers. I had a look at the pdf doc from Victron, but firstly I am not sure what size cable I must use with the balancers. Also not sure if I must add fuses in between. Can I also go ahead and connect it directly to the battery terminal or must I break the link cable between the batteries.

 

Thanks

Link to comment
Share on other sites

13 minutes ago, ProjectGKR said:

what size cable

They pass 700mA, so the wire doesn't have to be very thick at all.

This is actually something important that bears discussion. In a healthy battery bank, you should rarely have to bypass more than a couple hundred milliamps. There are other balancers on the market that can bypass more current -- up to 2A as advertised -- but the reality is that if you need to bypass that much you're in trouble already.

16 minutes ago, ProjectGKR said:

must add fuses in between

The Dutch would be telling you at this point to "read better!". It's in the documentation 🙂

Quote

Use at least 0,75 mm² to wire the negative, positive and midpoint connections (in this order). Additionally, if in your application it is needed to comply with UL, also fuse these wires near the batteries with a 10A fuse suitable for DC current (e.g. Littelfuse ATOF series automotive blade fuse in combination with an inline fuse holder).

UL is an American thing, but the answer is basically yes, you probably want to fuse them to be safe. You can use cheap automotive fuses for this, since the maximum voltage is less than 30V.

Reading back further in the thread:

3 hours ago, ProjectGKR said:

The inverter is set to switch to Eskom at 48V and then Go back to Battery on 54V.

I'd need more information to give a definitive answer, but just this bit alone suggests you may have been undercharging them. The battery has to spend enough time at absorption voltage, which is around 58V, to be fully charged. When your system goes back to battery at 54V, it depends on what kind of loads it has to handle. If there is more PV than loads, then of course the loads are powered AND the surplus power still flows into the battery... but the crucial bit of information we don't have (and it seems neither do you), is whether the battery was properly absorption-charged for long enough.

You have to fully charge a lead acid bank at least once a week, and to do this you have to take it up to 58V (ish, depends on battery spec) and hold it there until the tail current drops off to around 2% or less of the Ah capacity. If you don't do that, the batteries will sulfate, and they will fail.

It gets worse. After the absorption phase, the batteries are not 100% full yet. They should ideally spend some time at float voltage too.

Also, as @Jaco de Jongh already suggested, with the amount of PV you have it takes over three hours at full capacity to put back half of your capacity. The average equivalent full power solar day (ie if you divide the production by the peak power of the array) is around 5 hours in South Africa. Which seems to suggest your PV array is a little undersized for the amount of battery you have.

Link to comment
Share on other sites

1 hour ago, plonkster said:

I'd need more information to give a definitive answer, but just this bit alone suggests you may have been undercharging them. The battery has to spend enough time at absorption voltage, which is around 58V, to be fully charged. When your system goes back to battery at 54V, it depends on what kind of loads it has to handle. If there is more PV than loads, then of course the loads are powered AND the surplus power still flows into the battery... but the crucial bit of information we don't have (and it seems neither do you), is whether the battery was properly absorption-charged for long enough.

The MPPT's do reach a voltage of 58V for Boost and I do get that at least one of the 2 mppt's go into float (54.4V) (Summer days both reach float easily)

@Jaco de Jongh & @plonkster Would I be able to run 8x 200ah batteries on this setup atleast ?

Link to comment
Share on other sites

2 minutes ago, ProjectGKR said:

The MPPT's do reach a voltage of 58V for Boost and I do get that at least one of the 2 mppt's go into float (54.4V) (Summer days both reach float easily)

OK, that's a good start. But the MPPTs are not synchronised, so there is another issue involved here. One charge controller might go to float early because with the help of the other one the voltage is held high, but due to its own conditions (shading, different orientation perhaps?) the current drops below 6A earlier, and it goes to float too soon, leaving the other controller to attempt to finish absorption on its own.

A workaround might be to increase the boost-to-float timeout on the one controller.

This is just a wild guess though. You should ideally invest in a Victron BMV battery monitor 🙂

Link to comment
Share on other sites

You can run any number of batteries,  you just need to make sure you have enough power to charge them up again once they are discharged. What is your total usage in kWh per day, and how does that compare to the kWh generated by the panels?

Edited by DeepBass9
Link to comment
Share on other sites

2 minutes ago, plonkster said:

OK, that's a good start. But the MPPTs are not synchronised, so there is another issue involved here.

I was initially told that the 2 Microcare mppt's will automatically master slave (no link between mppt's). But as you said is that both helps to get to the boost voltage and then when the one goes to float, the other still boosts, meaning that the so called master slave is not true and they working independant. Does the Victron MPPT's have an option to sync?

 

7 minutes ago, plonkster said:

A workaround might be to increase the boost-to-float timeout on the one controller.

The current interval is set to 1 hour, must I set the mppt that gets the morning sun first to be 2 hrs (setting options are 30min, 1hour,2hours)? If I change the one mppt to maybe boost to only 13.7v (54.8V), will this be even worse causing the on mppt to work harder?

 

14 minutes ago, DeepBass9 said:

You can run any number of batteries,  you just need to make sure you have enough power to charge them up again once they are discharged. What is your total usage in kWh per day, and how does that compare to the kWh generated by the panels?

I on average use 15-18kw units a day. I have set the Inverter to switch back to 48V instead of the default 46V to reduce the amount of discharge of the bank. I also have the bigger loads later in the day to give the bank time to get charged. I have noticed that on sunny days, the even a load of 50%, the 2 mppt's are still able to keep the voltage at 58V

Link to comment
Share on other sites

Thanks for all the feedback

Will I be able to salvage the system by doing the following:

1. Buy another SonX SX12-200D [12V200AH/100HR] AGM battery to get my system to run 2x 48v Battery banks again (as I now currently only have 7 batteries left)

2. Install  3x Victron Battery Balancers

3. Set the Inverter (Microcare 48v 5kw) to:
3.1. Battery Run to = 48V
3.2. AC Run To = 54V
3.3. Charger Switched Off

4. Mppt (Microcare 60A) for East Facing Panels (9x Panels)
4.1. Float Voltage = 13.5V
4.2. Boost Voltage = 14.5V
4.3. Boost to Float Change Interval Scan = 2hours
4.4. Boost to Float If Charge < 6 amps

5. Mppt (Microcare 60A) for West Facing Panels (9x Panels)
5.1. Float Voltage = 13.5V
5.2. Boost Voltage = 14.5V
5.3. Boost to Float Change Interval Scan = 1hours
5.4. Boost to Float If Charge < 6 amps

Battery info:
Cycle Use: 14.6-14.8V 
Standby Use: 13.6-13.8V

Edited by ProjectGKR
Link to comment
Share on other sites

With that usage you shouldn't have a problem. I'm off grid with less panels and a similar size battery and I get by no problem. My batteries rarely get to 70% and most mornings are at 80%. I am using 12-16 kWh per day. I also have 2 microcare MPPTs running independently. What I see with mine is that during bulk charging they both run with as much power as comes from the panels, once they get to absorb and the batteries start taking less current, one of the MPPTs will reduce current down until 6A and then go to float, the other one will keep the voltage up until the current gets to 6A, then that one will go to float as well and the voltage will drop to the float setting.

How are your panels connected? 3 strings of 3 in each array?

Edited by DeepBass9
Link to comment
Share on other sites

1 hour ago, DeepBass9 said:

How are your panels connected? 3 strings of 3 in each array?

Yes, 3 panels connected and then the 3 strings into a fused combiner box, and then down to the mppt

 

1 hour ago, DeepBass9 said:

I also have 2 microcare MPPTs running independently

Are all your panels facing the same direction or are they like my setup, 9x facing east and 9x facing west?

Edited by ProjectGKR
Link to comment
Share on other sites

Mine are north facing, one at about 35 degrees and the other at about 10 degrees, also in 3 panel series strings, so you should be getting plenty volts into the MPPT, so the problem is not there.

What I would suggest you do is firstly get a battery monitor. Then set the battery run down to voltage as high as possible (maybe 48V is as high as it goes). Run it like that for a few days so you are sure that the batteries are getting fully charged, and can check with the monitor. Then gradually adjust that voltage downwards until you get to a happy setting that does what you want it to.

What is the intention, to run from solar and batteries as much as possible? Or the batteries are more of a load shedding backup? The grid is still cheaper than batteries, so you should maybe use the grid a bit more and the batteries a bit less.

Is that microcare inverter a charger as well? I.e can you use it to charge the batteries from grid power?

Is it this inverter http://microcare.co.za/wp-content/uploads/2014/10/MC-1.5-5kW-Grid-Tied-Inverter-SpecSheet-2016v1.pdf

Edited by DeepBass9
Link to comment
Share on other sites

14 minutes ago, DeepBass9 said:

Is it this inverter

Mine is the following:

https://www.sustainable.co.za/microcare-5kw-24-48v-bi-directional-pure-sine-wave-inverter-with-charger.html

 

15 minutes ago, DeepBass9 said:

What is the intention

I work from home so basically if the sun shines I want to be able use solar as much as possible to reduce my carbon foorprint. Also loadshedding a big factor.

What monitor would you suggest?

The inverter also can go to 50v for back to ac. I will set to either 48v or 50v and start monitor with a volt meter until I get a monitor

 

Link to comment
Share on other sites

One of the victron BMV monitors. Voltage actually tells you very little about battery state of charge and can be quite misleading. The battery monitors sum the energy going in and out of the battery so you get a true state of charge measurement.

That inverter is a charger as well, so you can use the grid to charge the batteries to full to get a proper 100% full reading on the battery monitor.

Battery monitors :

https://thepowerstore.co.za/products/battery-monitor-bmv-700

https://thepowerstore.co.za/products/victron-bmv-712-smart-battery-monitor-9-90vdc?variant=12367958474814&currency=ZAR&utm_campaign=gs-2018-09-19&utm_source=google&utm_medium=smart_campaign&gclid=CjwKCAiAqqTuBRBAEiwA7B66hewNUIcif8SYdtIuc9kXY3kntxp9ioP-whO6eRMgpkF6Znm7pnqV6xoCm3QQAvD_BwE

 

Edited by DeepBass9
Link to comment
Share on other sites

4 hours ago, ProjectGKR said:

The current interval is set to 1 hour, must I set the mppt that gets the morning sun first to be 2 hrs (setting options are 30min, 1hour,2hours)? If I change the one mppt to maybe boost to only 13.7v (54.8V), will this be even worse causing the on mppt to work harder?

The idea is to get the MPPT that goes to float first to hang on a bit longer. You could increase the absorb/float timeout, or you could increase the charge voltage a tiny bit. It's a bit of a workaround, and also a bit of a guess from my side. I used to be of the opinion that unsynced solar chargers are no problem, but recently I started to realise what a big issue it is when they each have their own tail current detection. So one of them holds the voltage up and the other one measures a low tail current... and bingo. One of them decides it is time to go to float and leaves the party. Could be a problem... or maybe not. Got to get better monitoring.

4 hours ago, ProjectGKR said:

Does the Victron MPPT's have an option to sync?

Yes. The SmartSolar models sync via bluetooth.

Link to comment
Share on other sites

The tail current is a big problem, because if you are running loads then the tail current won't go low enough to switch to float, so you must add whatever your 'base load' current is. What happens on my system is when the pool pump switches off in the afternoon, then both the MPPTs go to float, usually.

Link to comment
Share on other sites

49 minutes ago, plonkster said:

The idea is to get the MPPT that goes to float first to hang on a bit longer. You could increase the absorb/float timeout, or you could increase the charge voltage a tiny bit.

The battery cycle use range is 14.6 to 14.8v. Gives room to up the morning sun mppt side. (With a voltmeter I have found that the mppt shows 58v but at the battery bank it is 58.4V)

Also is the battery balancer a good place to start with as well? Planning on ordering it first thing  in the morning.

Link to comment
Share on other sites

9 hours ago, plonkster said:

The average equivalent full power solar day (ie if you divide the production by the peak power of the array) is around 5 hours in South Africa.

Laymans' thoughts & thumbsucks. In the heart of winter I'd guesstimate around 3-4 hours equivalent solar day with the days being shorter. That's maybe two months around June/July where the daily consumption of 17kWh (or more during winter?) is only just being generated, if at all. And after a cloudy day or two, I'd expect the charge level to remain near permanently low for an extended time unless Eskom is used to replenish the charge.

11 hours ago, ProjectGKR said:

I know from the last couple of days I use around 4-5 kw units during the night

At peak generation, this power should be replenished within around 1 hr. In the morning, it could be achieved by for argument's sake 10-11am. To be checked once you have a battery monitoring system.

7 hours ago, ProjectGKR said:

I also have the bigger loads later in the day to give the bank time to get charged.

Not sure what time the bank is charged, but if peak production is say 10:00-14:00, try to make hay while the sun shines and run heavy loads in this time. Leaving it for too late might mean having to forgo the opportunity to use the available solar power, and cycle your batteries more than needed, with insufficient time to recharge for the night later in the day.

Link to comment
Share on other sites

9 hours ago, GreenFields said:

Not sure what time the bank is charged, but if peak production is say 10:00-14:00, try to make hay while the sun shines and run heavy loads in this time.

Heavy load is usually between 13:00 - 16:00. Will make plan to change this.

I am going to order a battery monitor this morning plus balancers. Will give feedback once I received and installed it.

Basically from my understanding is that with a monitor I will get a better picture on what is happening at the charging side of my system as this looks to be incorrect.

Thanks all for the feedback. Helps alot.

Edited by ProjectGKR
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...