Just installed a 48v 3000 ah batery bank

Yryf

Hi
Just installed a 48v 3000 ah batery bank after our 1500 ah battery bank wouldn't hold charge.

The problem is its at 57.2 volts and it's only charging at around 30 amps. This seems off to me .

Shouldn't such a large battery bank be charging at a higher amp rating at such high volts? Not sure how that works.

I think the bank is about 90% full. So is it charging at 30 amps because it's only charging the 10% portion which is 300 amps?

Yryf

Forgot to mention that we are using a 20 KW solar array to charge the batteries.

Thanks

Photowhit

What charge controllers? What are your charge controllers saying?

30 amps each from 6 charge controllers? a lightly overcast day...

...or you are 90% full and you are out of bulk, battery slowly reduces what current it will take, but voltage should be regulated by charge controllers.

If the charge controller say Float stage they are just reducing voltage and will settle in at your set 'float' point.

What does you hydrometer say?

Tools?

-Charge controllers

-Clamp meter

-hydrometer

Yryf

Hi
Out of 6 charge controllers only two are working. There is a power draw from the inverters of 10 amps and a charge current going to the batteries of about 30 amps from 6 charge controllers.

I'm confused as to why a 3000 ah battery bank is only charging at 30 ah. Is this normal?

Yryf

Oh and there is full sun outside not overcast. I believe the batteries are at about 90% full. This was at bulk stage that the 6 charge controllers were charging the batteries at 30 ah at 57.2 v

Yryf

30 ah in total from all 6 charge controllers. 2 out of 6 were saying charged the other 2 said absorb.

Yryf

My question is why are only 2 charge controllers working when the batteries need charging and it is full sun outside ? And why is a 3000 ah battery bank being charged at only 30 ah?

vtmaps

Welcome to the forum.

Please answer Photowhit's questions, in particular what controllers are you using? 

Do you have an hydrometer?  If so, what is the specific gravity of the electrolyte?  If not, buy one.

By the way, saying that "battery bank being charged at only 30 ah" makes no sense.  I think you mean that the charging current is only 30 amps (not amphours).

--vtMaps

zoneblue

From the little  that youve said, its most likely the batteries are fairly full. 4 of the 6 controllers are in float, the other two in absorb. Thats just a product of calibration issues between them, and that they appear not to be networked.

It is best if the controllers are networked or failing that calibrated, so that they all move to absorb and float at around the same time. However multi controller setups will always share unevenly.

If you would like more help please post full system specs.

Yryf

Hello

Yes I mean charging current is around 30 amps.

No I don't have a hydrometer. What's it for?

I have 6 charge controllers. All victron 150/70 connected to 3000 ah 2V batteries arranged in 48v . Running 3 victron Quattro 10 kw inverters arranged in 3 phase.

My problem is I think the charging current of the batteries is low. Also another problem I noticed with batteries is, by the end of the night around 5 am the voltage drops to 47 v . The batteries have a constant draw of 8 amps from sundown around 5 pm to sunrise around 7 am. I think this voltage may be a bit low considering it's a new 3000 ah battery bank! What do you think?

vtmaps

Yryf said:

No I don't have a hydrometer. What's it for?
<snip>
My problem is I think the charging current of the batteries is low. Also another problem I noticed with batteries is, by the end of the night around 5 am the voltage drops to 47 v . The batteries have a constant draw of 8 amps from sundown around 5 pm to sunrise around 7 am. I think this voltage may be a bit low considering it's a new 3000 ah battery bank! What do you think?

I think your batteries will be scrap very soon if you don't get them properly charged.  If those batteries were fully charged in the evening and you drew 8 amps for 10 hours, in the morning those batteries would be at 97% SOC (state of charge) and their voltage would be at least 51 volts.

A hydrometer measures the SG (specific gravity) of the battery electrolyte.  That tells you the SOC of the battery.  You can buy an adequate hydrometer for $10, but I like this one:  http://www.solar-electric.com/midnite-solar-battery-hydrometer.html

You need to figure out why your charging current is so low... I would need many more details of your system to make a diagnosis.  Time is of the essence, you can ruin those batteries in a few weeks if you don't get them properly charged.  We (on the forum) can help you figure this out, but you have a lot to learn and not much time.  Who installed your system?  Maybe they can help. 

--vtMaps

animatt

Definitely  agree batteries are in serious peril.  Also agree poster needs to learn alot fast or be ready to buy more batteries soon.  So consulting installer maybe a wise move.

I just question given by poster. Reporting leaves a bit to be desired. 

I particularly question the amp draw. 8 amps at what voltage? Battery voltage or 3 phase voltage?  Not sure if his inverters can output 480v.  Obviously 480v  vs 48v is a factor of 10 different. 

He does have major issues regardless. 

My question for original poster.

Amp draw over night, how is that measured.  And at what voltage is that.

What is charging voltage when charging in morning,  then mid day. Be more specific about charging as compared to first post,

And hydro meter is a must.
Animatt

Photowhit

Yryf said:

My problem is I think the charging current of the batteries is low. Also another problem I noticed with batteries is, by the end of the night around 5 am the voltage drops to 47 v . The batteries have a constant draw of 8 amps from sundown around 5 pm to sunrise around 7 am. I think this voltage may be a bit low considering it's a new 3000 ah battery bank! What do you think?

What is your charging current in the morning? Charging current when the solar panels (array) is fully exposed to the sun? Do all your charge controllers read the same or is there a single display? If you have a single display does it read for a each charge controller separately?

So you have an 8 amp load and I will guess at 400volts? That would be 8amps X 400volts = 3200watts (amps X volts = watts) 3200 watts ÷ 48 volts = @67 amps call it 70 amps since the inverters will use a bit. . .   Over 14 hours 14 x 70 = 980 Amps from your 3000 amp battery bank! If you are measuring the voltage while it still has a 70 amp load I'd say you are in the ball park at 47 volts. If you remove the load and the solar array and wait a half hour to an hour, I would expect the voltage to gradually increase to about 49 volts.

Yes, you have a lot to learn and an expensive system to make mistakes with! You had a previous smaller battery that died, if it had the same load did it fail over night?

I would familiarize your self with a hydrometer, which checks the Specific Gravity(SG) of the Batteries electrolyte (acid). The Specific Gravity of the batteries is the most accurate way to see what state of charge the battery is in. You might check with the manufacturer of the battery or possible on the information plate of the battery to find out what the specific gravity of the electrolyte should be.

Check to see how your charge controllers and display work. You may have a single display that is showing each charge controller individually, There may be a method to set it up to give you a total of the charging current.

30 amps from each of 6 charge controllers would not be out of the question. a 20,000 watt array would be expected to produce 20,000 ÷ 48 = 416 amps. but panels are rated at optimum conditions. Normally they produce about 75% of panel rating or 416 x .75 = 312 amps. 312 amps from 6 charge controllers = about 52 amps each.

The odd thing is rarely do system work at the max, your large array starts producing when the sun comes out, as it charges the voltage rises, so as you approach it's maximum ability the battery voltage rises, and the battery fills. So by 11 you likely reach absorb with the voltage being limited by the charge controllers at about 60 volts.  So to do the math at 60 volts 20,000 ÷ 60 = 333 amps. . . 333 amps x .75 = 250 amps . . . 250 amps ÷ 6 (charge controllers)= 41 Amps available, but your battery has reached absorb cycle so it is accepting less amps and will taper off until it reaches the float stage.

Hope this helps, we are working with limited information and all this could be erroneous (badly incorrect)

vtmaps

Yryf said:

The batteries have a constant draw of 8 amps from sundown around 5 pm to sunrise around 7 am.

vtmaps said:

If those batteries were fully charged in the evening and you drew 8 amps for 10 hours, in the morning those batteries would be at 97% SOC (state of charge) and their voltage would be at least 51 volts.

animatt said:

I particularly question the amp draw. 8 amps at what voltage? Battery voltage or 3 phase voltage?

Photowhit said:

So you have an 8 amp load and I will guess at 400volts? That would be 8amps X 400volts = 3200watts

Photowhit, I suspect you have guessed correctly.   I didn't make any guesses... I took Yryf's statement literally.   I have nothing to add until we hear from Yryf again.

--vtMaps

Photowhit

vtmaps said:

Photowhit, I suspect you have guessed correctly.   I didn't make any guesses... I took Yryf's statement literally.   I have nothing to add until we hear from Yryf again.

--vtMaps

You and I have seen it too often, people confusing amps (or volts) with watts!

zoneblue

Yes please please please all posters, specifiy all loads in watts AC (or DC). It adds significant clarity to not only the discussion but your own ability to grapple troubleshooting.

zoneblue

OP, you have done the right thing coming to the forum for help, as others have said now is the time to get this system running right. But you are going to have to put some leg work in here. We need FULL specs, everything:
PV brand and model, string configuration, cable lengths & gauges, battery brand and model, charger setpoints, Some photos will help as well.

Yryf

Hi guys

Thank you for all your replies.
Will try to give as much info as I can.
I will get a hydrometer asap.
I have uploaded a log file of the last 2 days.
Also a chart of the battery bank voltage and amps. Unfortunately because the charge controllers aren't being recognised by the color control gx I cannot include them in the logs.

https://drive.google.com/file/d/0B-SkKoJuefl4ZFVRRHlQcnNrVDg/view?usp=docslist_api

http://imgur.com/t6N2bIG

We just changed all 6 of the charge controllers to victron 150/70 and connected them in parralel. I suspect they need an update though.

Another thing I noticed is that since we installed the charge controllers in parralel they have been charging the batteries nearly all day.

The battery bank is from an unknown Chinese company. We just imported them from China and installed them ourselves. Unfortunately we don't have people who know or supply battery banks here. All I know is they are 2V each and 3000 ah. And weigh a ton! I really hope we don't have to replace them soon!!

PV brand unknown another Chinese OEM.
İ will dig up some more info on them and let you guys know. Total of 20 kw of panels.

Right now in North Cyprus, we have full sun everyday and temps around 20 c.

I'd have to check the settings for bulk float etc. But the log would give a rough idea.

Yryf

The batteries are sealed vrla batteries and therefore cannot be measured by a hydrometer. So that's out.

I have a battery meter victron bmv 600 s . İt's supposed to work with Peukert's law. It shows the batteries being 100% full all the time.

Yryf

Night time consumption is around 500 w ac (230v).

westbranch

Another thing I noticed is that since we installed the charge controllers in parralel they have been charging the batteries nearly all day.

this is a GOOD sign, let them run and monitor frequently, ie log the numbers for everything you can see...V, A, hours in a stage of charge, BULK, Absorb,Float etc, of each Charge Controller...

Yryf

I'm thinking of doing a battery equlization. Anybody think this may be a good idea?

SandyP

Yryf said:

The batteries are sealed vrla batteries and therefore cannot be measured by a hydrometer. So that's out.

I have a battery meter victron bmv 600 s . İt's supposed to work with Peukert's law. It shows the batteries being 100% full all the time.

EDIT : Probably ignore the comments below as I based this on a simple Victron monitoring system.
 
Based on the graph you posted it appears that :

1) For the days in the graph there was no PV charging input into the batteries or,

2) You have installed the shunt that the Victron BMS uses in the wrong place ie. not in the common -ve lead that goes to the battery from both the charge controllers and the inverter(s).

I would guess the shunt is on the -ve lead to the inverter - however this should result in the SoC on the Victron continuously decreasing not staying at 100%.

I will have a look at your spreadsheet.

Solar2

Yryf said,
"The batteries are sealed vrla batteries and therefore cannot be measured by a hydrometer" 

Do not do any equalization.

I do not know what a vria battery is
but if it is a sealed battery, better not try any equalization until you know what is going on.

vtmaps

Solar2 said:

Do not do any equalization.

I do not know what a vria battery is
but if it is a sealed battery, better not try any equalization until you know what is going on.

VRLA = valve regulated lead acid.  That means it is a sealed battery, and the valve is a safety feature...  if you overcharge it hard enough (like an equalization), it will make enough gas to pop open the valve.  That's very bad for the battery.

Many AGM manufacturers do recommend equilization, but it's not the same type of equalization that a flooded LA battery uses... AGM equalizations may just be an extra long absorb stage, or if the voltage is raised above absorb, it is only by a couple of tenths of a volt.

--vtMaps

SandyP

Yryf said:

I have a battery meter victron bmv 600 s . İt's supposed to work with Peukert's law. It shows the batteries being 100% full all the time.

SoC at 100% all the time, obviously something is not correct.

Your spreadsheet of data seems to indicate that you are only using a total of ~217ah in a day of which only ~80ah is used from sundown to sun up.
If this is correct then the SoC in the morning should be ~98% - this does not correlate with the battery voltage drop - unless your batteries are severely (totally) sulphated?
Hopefully someone else can assist here as I think I am out of my depth.

Yryf

Hey guys
I've uploaded another graph of the last week.
http://imgur.com/sxUtW65

It's been 3 days since I've updated and synced all charge controllers. As you can see in the graph. Before the update and sync the charge controllers were in absorb almost all day.

Since sync and update, the last 3 days, it only charged the batteries for about an hour 1st thing in the morning. Which makes more sense given the 3000 ah battery bank and only 500 w consumption throughout the night.

Now the only thing that confuses me is the low voltage drop at night! Next i will connect the battery monitor to the system to get an accurate reading of the voltage.