Growatt 3500 error 52 with SOK 48v 100ah

[Bhilton]

Hello,

When I use my 10” compound mitre saw I am occasionally having an issue where the SOK battery seems to go into a protection state causing the Growatt to no longer see the battery and thus throw an error 52 “bus voltage too low”. I am guessing the bus voltage is too low because the battery completely disconnects itself. During these errors, The battery is at 75% or more capacity. Cells are balanced too.

If I turn off the PV array off and on to let the growatt reboot, it clears the error 52 and also the SOK battery kicks itself back in after something like 60 seconds.

The AC output on the inverter connects to a breaker panel with a single 15A breaker which feeds a receptacle. I use a 75’ extension cord to reach the mitre saw.

I run a fridge 24/7 and various other items including an electric kettle which has a high watt surge I believe. These do not use a long extension cord and they do not cause the error 52. In fact, nothing else has caused the error.

Any ideas?

 

[timselectric]

The saw has a high start up surge. It's overloading the BMS.

 

[marionw]

When using the SOKTools software to view the battery does the Memory Info tab show anything.
Just before operating the 10” compound miter saw start up the SOKTools software and on the Multi Monitoring tab check the "Save data to database" checkbox which will start data collection. If you get the error then check the status of the DISCHARGING-Off (or -On) and DISCHARGING MOSFETS. Also look for any Alarm or Protection status(s)

You will need a serial to USB cable to connect to computer to run the software.

Download SOKTools form the Current Connected website, use last link on gthe page.

SK48V100 Server Rack Battery Owner & Operator's Manual | Current Connected

Full instruction manual for the SOK SK48V100 server rack battery. Everything you need to know is contained within this document!

www.currentconnected.com

 

[Bhilton]

When using the SOKTools software to view the battery does the Memory Info tab show anything.
Just before operating the 10” compound miter saw start up the SOKTools software and on the Multi Monitoring tab check the "Save data to database" checkbox which will start data collection. If you get the error then check the status of the DISCHARGING-Off (or -On) and DISCHARGING MOSFETS. Also look for any Alarm or Protection status(s)

You will need a serial to USB cable to connect to computer to run the software.

Download SOKTools form the Current Connected website, use last link on gthe page.

SK48V100 Server Rack Battery Owner & Operator's Manual | Current Connected

Full instruction manual for the SOK SK48V100 server rack battery. Everything you need to know is contained within this document!

www.currentconnected.com

Ok I will try this next time I am up at the cabin.

Thanks!

 

[Bhilton]

The saw has a high start up surge. It's overloading the BMS.

Wouldn’t the 15A 120v AC breaker limit the startup surge to 15A?

 

[timselectric]

Wouldn’t the 15A 120v AC breaker limit the startup surge to 15A?

No
Surges are brief, and the breaker is designed to let them happen.
Breaker has a trip curve that decreases over time.
A surge is short enough to not trip the breaker.

A BMS is very fast.

 

[Bhilton]

No
Surges are brief, and the breaker is designed to let them happen.
Breaker has a trip curve that decreases over time.
A surge is short enough to not trip the breaker.

A BMS is very fast.

Ok, can I use any devices to avoid hitting the BMS, such as a small AC UPS to handle the surge, if it even works that way lol

 

[timselectric]

Ok, can I use any devices to avoid hitting the BMS, such as a small AC UPS to handle the surge, if it even works that way lol

Not really.
You should either decrease your loads or increase your battery/BMS capacity.

 

[timselectric]

Or move the saw closer. (Shorter cord)

 

[Bhilton]

Not really.
You should either decrease your loads or increase your battery/BMS capacity.

Decrease my loads seems odd, I don’t have anything running during these errors, except maybe at the same time the fridge is cycled-on which uses 2.0A, the Growatt itself uses around 0.8A.

I can’t see the 2.8A draw being the straw that broke the camels back!

I will use the SOKTools and get some data. Maybe I can get an appropriate battery setup or BMS for my needs.

If I ran a separate inverter off the SOK battery would that make a diff? Could it manage the saws surge draw better?

 

[timselectric]

If I ran a separate inverter off the SOK battery would that make a diff? Could it manage the saws surge draw better?

Not if the BMS is what is being overloaded.
Which is what I believe is happening.

 

[Bhilton]

Not if the BMS is what is being overloaded.
Which is what I believe is happening.

ok.

Out of curiosity, are there any LiFePO4 batteries with BMS's that are known to handle higher output surges?

 

[Bhilton]

It looks like the SOK can handle a brief surge of up to 125A.

I looked up a golf card 48v lifepo4 and it listed 400A peak surge.

I guess the SOK 48v 100ah is on the lower end of peak surge performance. Damn.

 

[timselectric]

You can increase your capacity with a second battery.
Or with a larger battery.

 

[Bhilton]

You can increase your capacity with a second battery.
Or with a larger battery.

Ah ok, so you're saying a second battery in parallel would also split the surge across the two BMS's ?

 

[timselectric]

Ah ok, so you're saying a second battery in parallel would also split the surge across the two BMS's ?

Yes

 

[Bhilton]

Yes

Thanks!

Before I run out and purchase a 2nd battery, would it be ill-advised to buy a different battery brand for a second battery or keep them identical?

 

[timselectric]

Thanks!

Before I run out and purchase a 2nd battery, would it be ill-advised to buy a different battery brand for a second battery or keep them identical?

As long as the type and voltage are the same, they will work fine together.
As long as you don't want closed loop communication.

 

[Bhilton]

As long as the type and voltage are the same, they will work fine together.
As long as you don't want closed loop communication.

ok, thanks again!!

 

[marionw]

Thanks!

Before I run out and purchase a 2nd battery, would it be ill-advised to buy a different battery brand for a second battery or keep them identical?

Although you do not need to keep the batteries identical, keeping them identical may help later on if you decide to expand. In addition keeping with the same battery, they will have the same BMS and battery balancing may be more uniform. If the SOKTools software (or a manufacturer provided software) works then managing and keeping an eye on the batteries would also be easier. It would then also be your choice if you want to use closed loop communications (or not) or use a monitoring software like Solar Assistant. The same brand I believe gives you better options for and flexibility for the future.

I look at it like buying cordless power tools. With the same brand tool I can use the same batteries between the different tools and the same chargers to charge the batteries. I have several EGO outdoor power tools but only two batteries and chargers. Since I only use one tool at a time and I can swap the batteries between the tools it all works out.