Inverter occasionally goes into high voltage disconnect

[ericfx1984]

An issue that I've noticed is that if my system is charging on a cloudy day with the sun peeking out from time to time and I'm not using a lot of energy that occasionally when I get up to the very top end of charge my inverter will disconnect due to high voltage

I have a pair of lithium iron phosphate batteries... Each with a 200 amp BMS (I think jbd?)

I also have multiple charge controllers in the mix

What I think is happening is that the battery voltage is reaching the maximum voltage per cell or possibly per pack... At which point the BMS disconnects the charging side of the battery which causes a momentary jump in voltage or split second, this temporary increase in voltage that lasts until the charge controllers recognize the full state of charge

My thought is that this is not noticed when I'm actually actively running a load, such as an air conditioner, because the act of load creates somewhere for the momentary increase in voltage to go... As such it remains unnoticed

There's a couple ways that I think I could solve this issue

One would be to lower the overall battery charge voltage coming out of The MPPT charge controllers

The other option might be to increase the maximum pack voltage before disconnect in the battery management systems


I could really use some help on this

 

[rodrick]

On a Lifepo cell 3.65 is the max per cell and for longer life span 3.5 or 3.55 is even better so depending on your settings I wouldn’t raise the pack voltage, definitely not above 3.65

 

[Shimmy]

My thought is that this is not noticed when I'm actually actively running a load, such as an air conditioner, because the act of load creates somewhere for the momentary increase in voltage to go... As such it remains unnoticed

Welcome to the world of cloud edge effect. PV voltage spikes, no place for power to go. You need some kind of load-- either a battery to charge or household load to stabilize things.

 

[ericfx1984]

Welcome to the world of cloud edge effect. PV voltage spikes, no place for power to go. You need some kind of load-- either a battery to charge or household load to stabilize things.

Perhaps leaving the AC on? Or maybe switching the RV refrigerator to plugin power(currently it's on propane)

 

[Shimmy]

Perhaps leaving the AC on? Or maybe switching the RV refrigerator to plugin power(currently it's on propane)

Whichever has the better value for you. You just need to try to better match total production with total consumption so your battery spends a minimum amount of time fully charged.

 

[mikefitz]

Lower the charge voltage. The 'recomendecd ' charge voltages are often too high, resulting in BMS entering protection and shutting down the charge path. 3.5 volts per cell is more than sufficient as a charge voltage.
Keep cell protection at 3.65 volts. If your BMS allows access to cell volts and protection activation any over volts will be shown.

 

[DIYrich]

What are your current settings? Charge rate could be set too high, and/or protection voltage could be too low. Or it could be all ok.

Can you export to grid?

 

[ericfx1984]

What are your current settings? Charge rate could be set too high, and/or protection voltage could be too low. Or it could be all ok.

Can you export to grid?

I rarely see more than about 170 amps or coming into the battery bank... I have 22 kilowatt hours of lithium-iron phosphate batteries so they can definitely absorb it

I cannot expert to grid because the property does not have a grid connection

 

[ericfx1984]

Lower the charge voltage. The 'recomendecd ' charge voltages are often too high, resulting in BMS entering protection and shutting down the charge path. 3.5 volts per cell is more than sufficient as a charge voltage.
Keep cell protection at 3.65 volts. If your BMS allows access to cell volts and protection activation any over volts will be shown.

I went ahead and set the overall charge voltage coming out of the charge controllers to 14 volts

I figure at that point it should never get above the battery management systems charge disconnect voltage

At least that's my thought on it

 

[LydMekk]

170A charging sounds like way too much for the size of your battery bank.

 

[DIYrich]

170A charging sounds like way too much for the size of your battery bank.

The original poster is really reluctant to give details about the system. Without more detailed information, it is hard to give good advice. If poster has two LF280k banks, then 170amps is fine. If it is two 100ah banks, then 170 is too much. Need the details on the charger and bms settings for his original question.

Assuming the signature is correct (and is not talking about a different system), OP has 230ah and 304ah, which is fine for 170a charging.

 

[ericfx1984]

170A charging sounds like way too much for the size of your battery bank.

As I stated earlier I have about 22 kilowatt hours of lithium iron phosphate batteries... 170 amps going into them providing all connections are done correctly is absolutely not a problem

 

[740GLE]

22kwh for a 12v system (you said you set the SCC to 14v) is about 1800ah.

How many cells do you have in parallel if you only have two BMS controlling two banks? 4p4s?!?!? Times two?

Any chance you could show how your multiple SCC are connected? Do you have 3 SCC? 8 SCC?

Are we taking mix and match brands and ratings as well? Maybe different types of inter connection wiring to boot?

Having multiple SCC handling that much current can get tricky as they may confuse each other.

 

[ericfx1984]

22kwh for a 12v system (you said you set the SCC to 14v) is about 1800ah.

How many cells do you have in parallel if you only have two BMS controlling two banks? 4p4s?!?!? Times two?

Any chance you could show how your multiple SCC are connected? Do you have 3 SCC? 8 SCC?

Are we taking mix and match brands and ratings as well? Maybe different types of inter connection wiring to boot?

Having multiple SCC handling that much current can get tricky as they may confuse each other.

I could probably draw it out at some point... But honestly dropping the charge voltage to 14v seems to have solve the problem

 

[HRTKD]

But honestly dropping the charge voltage to 14v seems to have solve the problem

That is a common solution.

It would be good to know what your cells were doing. Are thy hitting high voltage disconnect? Or is it the entire battery that hits that.

 

[Supervstech]

I rarely see more than about 170 amps or coming into the battery bank... I have 22 kilowatt hours of lithium-iron phosphate batteries so they can definitely absorb it

I cannot expert to grid because the property does not have a grid connection

22kWh at 12.8V is 1718.75 Ah!

 

[740GLE]

22kWh at 12.8V is 1718.75 Ah!

Don’t worry he has two BMS to keep that all in check! ?

 

[ericfx1984]

That is a common solution.

It would be good to know what your cells were doing. Are thy hitting high voltage disconnect? Or is it the entire battery that hits that.

It's the entire battery that's heading disconnect... I looked in the BMS to double check everything and it never recorded a a high cell... They all stay pretty darn close to each other. I've never seen them more than 0.00X volts out of balance

high voltage disconnect, for the pack is set to 14.6v on the BMS

Charge voltage for the MPPT charge controllers is set to 14 volts now but previously was set to 14.6

 

[ericfx1984]

22kWh at 12.8V is 1718.75 Ah!

Or thereabouts

 

[HRTKD]

Charge voltage for the MPPT charge controllers is set to 14 volts now but previously was set to 14.6

Bingo! That was too high.