48v Growatt SPF 3000TL and LifePo4 Battery problem

[AakiraA]

Here is how I have my system setup:
-2 - 48v Growatts in split phase. Utility is in its own breaker panel and not connected directly to the house. Utility is set up to only power the washer and dryer and nothing else. The Growatt units run into my main breaker panel and powers the whole house. Utility only comes in on the back end when there isn't enough solar or battery power.
-I have 14 commercial 460w Jinko solar panels which provide me with more then enough power to run my whole house all day long.
-I just added 2-24v 5kWh total batteries which are in series to provide 48v.
SO my system is set in SBU mode and during the day solar provides power to my house. After sunset the batteries kick in and that's were my problems start. I plan to add more batteries soon but for now the 2 - 24v ones are all I have

I originally had 8 Harbor Freight AGM 12v 35ah batteries setup to provide 48v (left over from a small 12v system I had) and these would provide me with 1 hour of power before the Growatt would recharge then back to battery for an hour then recharge and so on.
I bought the 2- 24v LifePo4 batteries from Battery Evo and was excited to get better batteries and longer usage during the night. Talking to battery Evo and giving them my info on my nightly energy use I was told that I should get about 2.5 hours out of the battery which is cool that's what I was hoping for and if I add 2 more sets then I would be good for the whole night.

Here is my problem...I connected my batteries and waited for night to come. Sun went down and I watched as the Growatt switched over to battery then 3 min in it switched to utility and started to charge my batteries...then back to batteries once they were charged then 3 min later back to utility and so on.
Between me, battery Evo and 1 email reply from Growatt we can not figure out what is going on. This expensive battery gives my only 3 min of use so I figure its a setting problem someplace but I just don't know where to look anymore.
I came across this forum and seen everyone talking about these units and how everyone was trying to really help each other so I had to sigh up in 1 last effort to try and figure this out.

Here are my current settings:
#1 SBU
#2 20a
#3 APL
#5 USE
#12 48v
#13 55v
#19 56v
#20 56v
#21 45v

Thank you in advance

 

[sunshine_eggo]

First, seeing two 24V batteries showing a whopping 1.3V difference between them is a nightmare. This suggests your batteries are at a wildly different states of charge. I suspect what is happening is the a cell in the left battery drops to the BMS cut-off or nearly there or drops to the utility switchover point.

Those batteries need to be INDIVIDUALLY charged to full and then placed in series. They should always read nearly the same voltage.

The main wire from the Anderson to the Growatts looks pretty thin. What gauge is it?

The cheap-looking breaker you have on the (+) conductor could be a source of voltage drop. It's worth checking the voltage drop across it.

I would disable battery use until you get this sorted by making the following config changes:

Here are my current settings:

#12 48v 54.4
#13 55v 55.2

#14: SNU

#20 56v 54.4

Note that Big Battery's float specs are wrong. You need a float of 3.4V to prevent damaging the cells.

 

[AakiraA]

First, seeing two 24V batteries showing a whopping 1.3V difference between them is a nightmare. This suggests your batteries are at a wildly different states of charge. I suspect what is happening is the a cell in the left battery drops to the BMS cut-off or nearly there or drops to the utility switchover point.

Those batteries need to be INDIVIDUALLY charged to full and then placed in series. They should always read nearly the same voltage.

The main wire from the Anderson to the Growatts looks pretty thin. What gauge is it?

The cheap-looking breaker you have on the (+) conductor could be a source of voltage drop. It's worth checking the voltage drop across it.

I would disable battery use until you get this sorted by making the following config changes:


#14: SNU


Note that Big Battery's float specs are wrong. You need a float of 3.4V to prevent damaging the cells.

-Thank you for replying so fast. I re charged the batteries and they always seem to be about .3v off is that OK?
-The batteries came with there own cable set and there 6 gauge.
-I tested the voltage on both sides of the breaker and got the same reading. Just to be safe I moved the wire from the breaker to the distrobution block.

 

[sunshine_eggo]

-Thank you for replying so fast. I re charged the batteries and they always seem to be about .3v off is that OK?

You recharged them individually?

 

[AakiraA]

You recharged them individually?

Yes I did each on its own. Do you think there cold be an issue with the batteries?
I noticed in the manual (page 6) it mentions connecting lithium batteries BMS to the growatt RJ45 port. My batteries dont have a connection port. Could the problem that I have with only getting 3 min out of them be because there not connected that way?

 

[sunshine_eggo]

Yes I did each on its own. Do you think there cold be an issue with the batteries?

That's what we're trying to figure out.

I noticed in the manual (page 6) it mentions connecting lithium batteries BMS to the growatt RJ45 port. My batteries dont have a connection port. Could the problem that I have with only getting 3 min out of them be because there not connected that way?

Only certain batteries are compatible with the Growatt port. Yours are not.

0.3V difference isn't good either; however, it could just be the crappy digital meters. Check each battery with a voltmeter and compare.

The short run time could have been due to the horrific voltage difference between the two batteries. 26.3V could indicate a VERY LOW state of charge where 27.6V could be fully charged.

 

[AakiraA]

That's what we're trying to figure out.



Only certain batteries are compatible with the Growatt port. Yours are not.

0.3V difference isn't good either; however, it could just be the crappy digital meters. Check each battery with a voltmeter and compare.

The short run time could have been due to the horrific voltage difference between the two batteries. 26.3V could indicate a VERY LOW state of charge where 27.6V could be fully charged.

OK I just checked the batteries with my meter and Im getting whats showing op on the batter meter....27.7 and 28.1. Ive charge the batteries on there own 4 times now. I can get the voltage to be the same or like .1v off but once the growatt switches over to battery Ill see the volts start to drop fast then it connects back to utility to charge. After that 1st discharge is when the batteries always out of sync.

Do you think it could be a bad battery or BMS?

 

[offgriddave]

cable length problem? are the battery cables the exact some length from input terminal to output terminal for both positive and negative?
bad connection on one of the connectors? are all the connectors 100% crimped, soldered, connected, no debris, fastened, etc?
EMF interference? are you running a 7 ft jacobs ladder behind that wall? (j/k haha)

Edit: The blue wire between the batteries seems outrageously to long. Have you thought about or tried reducing that by 90%?

 

[AakiraA]

cable length problem? are the battery cables the exact some length from input terminal to output terminal for both positive and negative?
bad connection on one of the connectors? are all the connectors 100% crimped, soldered, connected, no debris, fastened, etc?
EMF interference? are you running a 7 ft jacobs ladder behind that wall? (j/k haha)

yes the cables are the same length and everything is crimped. Ive checked all the connections and everything is tight.

 

[offgriddave]

yes the cables are the same length and everything is crimped. Ive checked all the connections and everything is tight.

Edit: The blue wire between the batteries seems outrageously to long. Have you thought about or tried reducing that by 90%?

 

[AakiraA]

Edit: The blue wire between the batteries seems outrageously to long. Have you thought about or tried reducing that by 90%?

No that never crossed my mind, the cables came with the battery. Could that help with them not staying in sync? Could that be causing me to only get 3 min of use from them?

 

[offgriddave]

No that never crossed my mind, the cables came with the battery. Could that help with them not staying in sync? Could that be causing me to only get 3 min of use from them?

Sorry I am a newbie and new here, but it definitely doesn't look good. But if the theory thought out a bit, if true, the power is going to come in from the positive battery side good, then there's going to be resistance to the second battery through that blue cable. It won't charge the second battery as much. You could devise a few tests with a clamp meter and sample runs and see what the current is between the three. There's a "record" feature on my meter. It wouldn't be scientific but could help you eye it in before you start slicing up cables. Perhaps run this idea by their techs first?

 

[sunshine_eggo]

So the digital meters are accurate enough.

Are you charging them in the exact same way and to the same voltage for the same amount of time?

 

[AakiraA]

Sorry I am a newbie and new here, but it definitely doesn't look good. But if the theory thought out a bit, if true, the power is going to come in from the positive battery side good, then there's going to be resistance to the second battery through that blue cable. It won't charge the second battery as much. You could devise a few tests with a clamp meter and sample runs and see what the current is between the three. There's a "record" feature on my meter. It wouldn't be scientific but could help you eye it in before you start slicing up cables. Perhaps run this idea by their techs first?

I see what your saying and I understand. Ill try your idea and let you know the results

 

[AakiraA]

So the digital meters are accurate enough.

Are you charging them in the exact same way and to the same voltage for the same amount of time?

Yes, I charged the 1st one until charger said full then started charging the 2nd until the charger said full. What do you think of what offgriddave had to say about the cable length?

 

[offgriddave]

Oh also, the bolts for the battery input must be torqued down. Did you torque them down the right number of ft pounds? It should be in the manual. I don't have a growatt but yeah it could be that. If it is, one of those bolts could glowing red while in use.

Edit: You'll have to torque that bus bar also. I have the same one, it's very nice. Those bolts are big and silver coated for a reason!

 

[offgriddave]

-I just added 2-24v 5kWh total batteries which are in series to provide 48v.

...

Talking to battery Evo and giving them my info on my nightly energy use I was told that I should get about 2.5 hours out of the battery which is cool that's what I was hoping for and if I add 2 more sets then I would be good for the whole night.

Are these batteries even rated to dump 5kwh in "2.5 hours"? Could it be in 3 minutes you're hitting the internal BMS limits?

 

[sunshine_eggo]

...


Are these batteries even rated to dump 5kwh in "2.5 hours"? Could it be in 3 minutes you're hitting the internal BMS limits?

5000Wh/2.5h/48V = 42A

I sure hope so.

Yes, I charged the 1st one until charger said full then started charging the 2nd until the charger said full. What do you think of what offgriddave had to say about the cable length?

Unfortunately, I don't know the charger's criteria, so it's hard to say that it's good.

The batteries are in series, so the cable length can't affect balance between the two batteries. It only affects voltage drip, which may be a concern.

Oh also, the bolts for the battery input must be torqued down. Did you torque them down the right number of ft pounds? It should be in the manual. I don't have a growatt but yeah it could be that. If it is, one of those bolts could glowing red while in use.

Edit: You'll have to torque that bus bar also. I have the same one, it's very nice. Those bolts are big and silver coated for a reason!

This is a very good point. You need to carefully get a wrench/socket on every bolt/nut and make sure they're properly torqued.

What are the two battery voltages right before they cut out?

What does the Growatt report for battery voltage right before they cut out?

 

[AakiraA]

...


Are these batteries even rated to dump 5kwh in "2.5 hours"? Could it be in 3 minutes you're hitting the internal BMS limits?

Im told they are and Im hoping. The spec sheet is at the top of this page with my 1st post. Would you take a look at it and see if everything looks good. What can I do if im hitting the limit?

 

[AakiraA]

Oh also, the bolts for the battery input must be torqued down. Did you torque them down the right number of ft pounds? It should be in the manual. I don't have a growatt but yeah it could be that. If it is, one of those bolts could glowing red while in use.

Edit: You'll have to torque that bus bar also. I have the same one, it's very nice. Those bolts are big and silver coated for a reason!

I just used a wrench and did them really tight, my wrench didnt go low enough. I ordered a new torque wrench that will work. If the bolts are tight but not torqued right how does that cause a problem?