Axpert 4KVA inverters overcharging battery bank

[Eric]

Hi All,

I am a total newbie with solar, but because I've been noticing our system going down very quickly lately, I have began trying to understand my setup. I decided to check the voltage of each of my batteries this morning and to my surprise they all are reading about 27 volts.

I have two 48KVA-48-PARA-A inverters with the parallel boards installed, twenty 250w solar panels, and twelve twelve Taiyou 12v 200ah Valve Regulated Sealed Gel batteries. The batteries are connected in four in series and then the three series are connected in parallel to create three 48v batteries in parallel.  The battery bank is reading 105 volts. I am not sure how they have the solar panels connected, but when I read the voltage with a voltameter at thePV input it reads 125 volts. 

I just downloaded the WatchPower software, so I'm about to take a look at how the units are programmed. I'm hoping someone can tell me what might be the problem that is causing the batteries to be overcharged and also if the battery bank may be ruined from the excessive overcharging.

We had the system installed around August 2017, but at that point there was no parallel boards inside. The company connected the parallel boards in February of 2018. So, I'm not sure if the overcharging began six months ago or a year ago.

Thanks!

Eric

 

[Jaco De Jongh]

Firstly Welcome Eric

This looks like quite a problem you have. This seems to be an off grid setup. No AC connected..

1 hour ago, Eric said:

create three 48v batteries in parallel.  The battery bank is reading 105 volts

This With every setting available that I Know of is impossible to achieve. 

This is a wild guess, the installer either got it right to install the 2 chargers in series, or your panel voltage are reaching your batteries in some way or another, but i repeat, this is a guess, I have never tried to connect two Inverter chargers in series. Theoretically, they should add up, but if it is practically possible, that I haven't tested with Inverters. I have tested it with DC power supplies and was able to connect them in series and the output voltage doubled in that case. I suspect something similar in your case. 

 

1 hour ago, Eric said:

I'm hoping someone can tell me what might be the problem that is causing the batteries to be overcharged and also if the battery bank may be ruined from the excessive overcharging.

If you saw the system degrading, I guess the Batteries got hurt. Excessive over charge over any prolonged period will definitely destroy the bank...   

 

Please do the following?

1. Please check what voltage the Inverter is reporting by scrolling through the screens that is available to you. If they are reporting around 54 to 58 volts, I would even stronger bet on the "Chargers in series" theory.. 
2. Please check the connection to see if the inverters battery output connections are connected in series or in parallel?

[___]

That cabling job below the inverters... class one perfection.

48 minutes ago, Eric said:

The battery bank is reading 105 volts

Even the uprated Axperts only have 85V capacitors on the DC bus and the FETs are not rated much higher. If you actually have a 105V input, I'd expect some things to be blown sky-high. Unless some protection machinery kicked in. Also, those batteries must be toast.

22 minutes ago, Jaco de Jongh said:

your panel voltage are reaching your batteries in some way or another

Not uncommon. Shoot-through or otherwise damaging the top FET in the async buck converter causes the PV panel to be connected directly to the battery bank. That should pull the PV array down to the battery voltage, so it still points to the batteries being open circuit or toast (or both), but it could potentially account for the degradation.

 

[Jaco De Jongh]

4 minutes ago, plonkster said:

If you actually have a 105V input, I'd expect some things to be blown sky-high.

True if they are parallel connected, But if the chargers are connected in series, the input on each will only be halve the banks voltage, so effectively nothing will blow.. 

[Gnome]

7 minutes ago, plonkster said:

That cabling job below the inverters... class one perfection.

Battery cabling is up to sh#t also. Not to mention the wires are WAAAY too thin. Looks like 6mm which is a joke.

[___]

2 minutes ago, Gnome said:

Battery cabling is up to sh#t also

It's odd, the battery banks looks well cabled and neatly wired. In complete contrast to that rats-nest below the inverters.

[KLEVA]

1. From what I remember: In a parallel setup the Battery Bank is supposed to be ONLY connected to 1 of the Axperts. (Its highlighted in the manual)
2. 105V / 2 = 52.5 V (roughly close to the normal float voltage for those batteries) so maybe your battery testing is across incorrect points?
3. Test across the +ve and -ve across each battery bank (each 4) where the GREEN wires are connected (one with Red tape and one with black tape) - I am sure you will see 52-54V
4. Where do those smaller (possibly 6mm) black wires go from the Positive on one Invertor and the Negative on the other?

[KLEVA]

You surely would have seen smoke from the Axpert or the batteries after 6 months or more of a 105V feed to each of the 48V banks.

[Eric]

Hi All,

Thanks for the quick responses. I did some more investigating and discovered that it was me. I had the voltmeter on AC when trying to measure DC. When I switched it to DC the voltage now reads about 12.6 volts per battery and about 50 volts for the entire battery bank.

I think it may be running down because we're simply using too much power during the day. I'm including my wiring diagram and also my inverter settings. It would be great if someone can suggest any changes in my settings to ensure optimal performance. 

I live in the mountains of Ghana and there is no elecricity company here. I'm totally dependent on solar. If the sun is strong we can usually make it through the night without the solar beeping from a low battery. 

Thanks!
Eric

[Jaco De Jongh]

5 minutes ago, Eric said:

Thanks for the quick responses. I did some more investigating and discovered that it was me. I had the voltmeter on AC when trying to measure DC. When I switched it to DC the voltage now reads about 12.6 volts per battery and about 50 volts for the entire battery bank.

Wow what a relieve. Reading your first post, I thought you had some serious issues...  

I am glad you are closer to an answer.

[Eric]

That makes two of us Jaco! 

[___]

26 minutes ago, Eric said:

I had the voltmeter on AC when trying to measure DC

Interesting. My most meters I've worked with has a blocking capacitor and won't measure anything on DC. In fact, when you do that you get the AC component on top of the DC, and depending on the frequency and noise of that AC component you might get readings that are just completely bogus. So I suspect that is what you saw.

[Chris Hobson]

Hi Eric 

Welcome

A couple of things

1. Others have mentioned it but that rats' nest below the inverters is a no-no and potentially hazardous.  You have AC and DC conductors bundles up together. Unprotected cables should be in a conduit or trunking and DC and AC separated. Surfix has a thin metal sheath and so is deemed armored and can be exposed but not buried.
2. With 3 string of batteries I would have busbars and connect inverters to the bars.
3. Please ensure that you have CBs on the AC input and output and DC fusing and disconnects on both the PV and battery cables.

I may sound like I am coming down hard on you. I realise you had an installer do the job and now you are having to sort out his shoddy work. PV related fires are not uncommon. The local solar "ou" here in Graaff-Reinet house burnt down. Someone referred to him as my opposition. I just "looked" at at the offender and he retracted his statement.  

If you can supply the settings of your inverter Programs 1 to 31 or 38 we will be able to advise you. There is lots of Axpert know how on the forum (excuse the play on words but I have to take every opportunity I can get)

[Guest]

13 hours ago, Chris Hobson said:

Graaff-Reinet

17 hours ago, Eric said:

I live in the mountains of Ghana

I would hazard a guess and say that it could be a wee bit complicated to easily get all the correct parts?

Hope it is not the case though, for the advises given so far are solid.

 

Edited August 27, 2018 by Guest

[Coulomb]

I also notice that you are running stock firmware. Please look up posts about patched firmware; it fixes an issue that causes the battery to be chronically undercharged. This is not good for batteries, especially lead acid as you have. You may not be using too much energy at all. 5 kW of panels should run a decent sized house, unless you are getting a lot of shade.

I'm one of the "authors" of the patched firmware, so don't take my word for it, read posts from others.

Here is a place to start: Patched firmware based on version 73.00 . The actual patches are hosted on the Australian Electric Vehicle Association (AEVA) forum. You might have to go back several links to get to a "what this is all about" post; the patches have sadly been needed for several years now. Be sure to get the LC version of the patch, for Lead aCid and other chemistries, not the Lithium Ferrous version (for LFP batteries only).

I hope and expect that this fixes your issue.

[Coulomb]

I also agree with others that the battery cables are way too thin. They should be a minimum of 35 mm² (2 AWG). In Australia, we would not be able to get away with using green-yellow, or even pure green cable for any purpose other than protective earth (ground). At least, that's a regulatory / maintenance issue, it won't affect performance. But from the too-thin cables you will likely get very annoying flicker as loads come on and off. Also, those cables could overheat with extended loads and even normal charging at 4+ kW (80 amps or so). It could even start a fire.

Finally, I also agree that it would be very good to separate the DC and AC cables, and ideally have them supported and protected in cable troughs. Especially since the DC cables, until you get them replaced, will be getting quite hot at times.

Hopefully those batteries would normally be inside some sort of box, to at least shade them from direct sunlight. Heat will cause them to degrade faster than necessary. Though perhaps you are high enough that overheating is the last of your concerns. Really cold batteries won't perform as well as warm ones.

[Eric]

Hi Everyone, 

Thanks for all the great advice. It's a bit overwhelming so I'll  start slowly.

@Chris Hobson No problem. Medicine isn't always sweet. Lol So, what are CBs? Also, how do I provide the settings of my inverters that you mentioned? I thought that is what I provided with the previous screenshot. 

@The Terrible Triplett You guess correctly. I'm about 1.5 hours from Central Accra, but even finding the correct parts in the city can be an adventure and very pricey.

@Coulomb I started reading about the patches and discovered that I likely have a clone inverter. The P/N is 4KVA-48-PARA-A which I don't see anyone referencing as a Voltronic number. Below is an image of the label on my inverters. Have you heard anyone else on the forum being able to install the patch on an inverter with this P/N? I prefer not to be the guinea pig. 

Thanks!

Eric

 

[___]

4 minutes ago, Eric said:

what are CBs?

Circuit  breakers :-)

[Eric]

@plonkster Duhhhh........See I told you I was a newbie.  Thanks!

[KLEVA]

Since you have no Municipal Power, the AC stuff wont apply.  For those batteries though you will need to set your Bulk Charging Voltage to about 58V for Lead Acid (bit low at 56.4). My preference is normally to have a max charge of 10A/200Ah48V bank (so max charge of 30A in your case) so as not to heat up/damage the batteries, but this is highly dependant on your needs.

Edited August 27, 2018 by KLEVA

[KLEVA]

Also, if you have the Actual manual for this invertor, check whether the batteries are supposed to be connected to each, or just one.

[Chris Hobson]

2 minutes ago, Eric said:

Hi Everyone, 

Thanks for all the great advice. It's a bit overwhelming so I'll  start slowly.

@Chris Hobson No problem. Medicine isn't always sweet. Lol So, what are CBs? Also, how do I provide the settings of my inverters that you mentioned? I thought that is what I provided with the previous screenshot. 

OK Eric CBs = Circuit breakers

http://www.tripplebar.com/shop-2/electrical/distribution-boards-breakers/schneider-acti-9-ic60n-single-phase-ac-miniature-circuit-breakers-mcb-6ka/

In the image there are single, double and triple pole circuit breakers I would use double breakers to use on AC input (you probably have a standby generator) and AC output.

If you press the enter button and hold it in for 3 seconds you then enter the programming mode of the inverter. You can scroll up and down using the up and down arrows. I'll teach you how to make changes later. You have Programs 1 to 31 or 1 to 38. It is time consuming but write down all the settings and get back to us.

17 minutes ago, Eric said:

 

@Coulomb I started reading about the patches and discovered that I likely have a clone inverter. The P/N is 4KVA-48-PARA-A which I don't see anyone referencing as a Voltronic number. Below is an image of the label on my inverters. Have you heard anyone else on the forum being able to install the patch on an inverter with this P/N? I prefer not to be the guinea pig. 

Thanks!

Eric



 

@Eric the good news is  that I think this is 100% Voltronic. All the right features are there the font is right the labeling is right  the security sticker is right so you should have good service from your machines and you can update using @Coulomb's firmware.

[Chris Hobson]

12 minutes ago, KLEVA said:

Also, if you have the Actual manual for this invertor, check whether the batteries are supposed to be connected to each, or just one.

The Axpert cannot function without being connected to batteries. The parallel guide says all inverters must share the same battery bank and that the cabling between the battery bank and inverter should be the same material, thickness and total length

[Eric]

Thanks @KLEVA. I'll try to understand some of this stuff before changing. 

@Chris Hobson Okay. I knew there was a magic key combination. Looks like I have 1 - 31, so I'll post that information shortly. It's a relief to know I have a genuine Voltronic. Today's project will be attempting to update the firmware as suggested.

[KLEVA]

Thanks Cris, makes sense. I knew there was a specific warning about battery banks. Sorry about confusion.