Deye Parallel 8kW not working the same

RWI

New Member
I have 2 identical Deye 8 kW inverters operating in parallel with identical settings. Each has an identical set of solar panels 4 strings, 9 in series 300W nominal. 4 strings connected into the 2 MPPT controllers of each inverter. The Voc are virtually identical for each string at about 320 V DC. With good sun the panels will work at 270 V and 15 A per MPPT. For one of the inverters however the voltage slowly drops to 135-140 V and the power reduces while the other continues at 270 V. If I turn off and turn on again the DC on the one where the voltage has dropped it goes back to 270 V but then again slowly drops back to 135-140 V. Does anyone know if there are adjustments that need to be made to the MPPT controller settings or have any other idea why i have this problem.
 

meetyg

New Member
Do your inverters support limiting sensors? If so, and your not using them, maybe you should check the configuration to make sure limiting is disabled.
 

RWI

New Member
Hi Meetyg, yes there is a grid connection CT connected to the master inverter and the settings are for no export power. Th two inverters share the UPS lad and the grid import.
 

RWI

New Member
Hi XO4001, Yes there is a common battery system connected to both inverters. Any excess solar power charges the batteries and if there is insufficient the batteries help to supply the load until the minimum capacity (set 50%) is reached after which grid power is used.
 

XO4001

New Member
Just asked bc I have 2 5Kw parralel without batteries and they doint work in parralel
Each unit do his own thing they say it's normal until batteries are connected
Could it be that your batteries are near full when this ocours and the inverter is reducing itself
 
Last edited:

RCinFLA

Photon Sorcerer
You are getting close to maximum PV power limit. The two MPPT inputs are limited to unsymetrical maximum amounts according to spec sheet. (18A + 9A).
 

RWI

New Member
Hi XO4001, Thanks for the advice. Yes the batteries are connected. i think that these would work in parallel sharing the load even with no batteries. The batteries do not usually go above 90% so not near full batteries although maybe somehow the MPPT is thinking that the batteries are full and reducing the output. But it drops the DC voltage to 130 V even at part loads.
 

RWI

New Member
Hi RCinFLA, These are Deye hybrid 8.0 kW and have 2 x 22 A MPPT controllers and a maximum DC input of 10.4 kW and MPPT range of 125-425 V with a start up of 150 V. For some reason it takes the MPPT voltage slowly down to the minimum even at low loads. i know that it looks like it is limiting because the battery is at 100% but this is not the case also the battery voltage is well below the set absorption voltage.
 

mrzed001

Voice of reason
Hi RCinFLA, These are Deye hybrid 8.0 kW and have 2 x 22 A MPPT controllers and a maximum DC input of 10.4 kW and MPPT range of 125-425 V with a start up of 150 V. For some reason it takes the MPPT voltage slowly down to the minimum even at low loads. i know that it looks like it is limiting because the battery is at 100% but this is not the case also the battery voltage is well below the set absorption voltage.

Contact Deye (email), ask for help.
It can be a setting (but I do not see which can cause it), or it can be a bad MPPT in the inverter.
If you have an answer from them, please write it here :)
I have a friend who is thinking of an install like yours.
 

RCinFLA

Photon Sorcerer
Hi RCinFLA, These are Deye hybrid 8.0 kW and have 2 x 22 A MPPT controllers and a maximum DC input of 10.4 kW and MPPT range of 125-425 V with a start up of 150 V. For some reason it takes the MPPT voltage slowly down to the minimum even at low loads. i know that it looks like it is limiting because the battery is at 100% but this is not the case also the battery voltage is well below the set absorption voltage.
I don't know a lot about Deye but I thought is was similar to SolArk. I think they push PV DC-DC converter output to HV DC first stage point versus directly to battery done by other HF all-in-one inverters. That would limit PV to inverter 8KW capability which is also used in reverse to charge batteries. When I looked up spec I saw this sheet. The 2 x 22A may depend on model variants or firmware change that allows higher PV current when PV voltage is lower but still staying within 8kW limit.

This sheet with 18A + 9A would be 8KW at 300 vdc PV inputs. 22A + 22A would be possible if PV voltage is less than about 180 vdc. The drop off you are seeing may be the overload time based on inverter overload heating.

The 10400W max PV input power is likely refined specmanship to make it look good. Just like 'max' battery charging of 190A which is only possible sustained when battery is below about 42v. It may take higher then 8kW PV input if sum of battery charging plus inverter AC load is above 8kW but the HV DC-DC first stage cannot sustain backfeed to battery charging greater than 8kW. You can try that to see if it allows higher PV input power.
Deye-8KW-Solar-Inverter-Datasheet.png
 
Last edited:

RWI

New Member
Contact Deye (email), ask for help.
It can be a setting (but I do not see which can cause it), or it can be a bad MPPT in the inverter.
If you have an answer from them, please write it here :)
I have a friend who is thinking of an install like yours.
Yes I have contacted Deye but no response yet. I am not sure that they will identify this issue. Yes possible a setting but i have checked them many times and tried a few changes. Maybe a bad MPPT but then it has to be both of them. Possible some problem with the load sharing logic because this issue is with the Slave and not the master.
 

RWI

New Member
I don't know a lot about Deye but I thought is was similar to SolArk. I think they push PV DC-DC converter output to HV DC first stage point versus directly to battery done by other HF all-in-one inverters. That would limit PV to inverter 8KW capability which is also used in reverse to charge batteries. When I looked up spec I saw this sheet. The 2 x 22A may depend on model variants or firmware change that allows higher PV current when PV voltage is lower but still staying within 8kW limit.

This sheet with 18A + 9A would be 8KW at 300 vdc PV inputs. 22A + 22A would be possible if PV voltage is less than about 180 vdc. The drop off you are seeing may be the overload time based on inverter overload heating.

The 10400W max PV input power is likely refined specmanship to make it look good. Just like 'max' battery charging of 190A which is only possible sustained when battery is below about 42v. It may take higher then 8kW PV input if sum of battery charging plus inverter AC load is above 8kW but the HV DC-DC first stage cannot sustain backfeed to battery charging greater than 8kW. You can try that to see if it allows higher PV input power.
View attachment 68416
i have attached the actual nameplate information which confirms the 22A + 22A MPPTs, maybe your spec sheet is a bit out of date.
Certainly the drop off looks a bit like overheating but is does it just the same if the MPPTs are at half capacity.
Also the master does not have the problem only the slave and they have identical solar set up.IMG_3927.jpg
 

mrzed001

Voice of reason
Yes I have contacted Deye but no response yet.
service@deye.com.cn ?
How did you buy the inverters? Alibaba or local reseller ?

I am not sure that they will identify this issue. Yes possible a setting but i have checked them many times and tried a few changes. Maybe a bad MPPT but then it has to be both of them. Possible some problem with the load sharing logic because this issue is with the Slave and not the master.

So on the slave unit both MPPT's Volt goes down (and so the Watts produced) ?
Did you check it with a multimeter/fluke? You must have 1-1 fuse for this strings. There you can check if V really down.
Did you check it with PV strings disconnected? So you see the Voc is OK.
Did you try to start only the slave unit ? If the problem does not occur at that time then it is a parallel/sharing problem.


i have attached the actual nameplate information which confirms the 22A + 22A MPPTs, maybe your spec sheet is a bit out of date.
Certainly the drop off looks a bit like overheating but is does it just the same if the MPPTs are at half capacity.
Also the master does not have the problem only the slave and they have identical solar set up.

This is a very good unit. 1 phase and 22+22A MPPT.
 

RWI

New Member
service@deye.com.cn ?
How did you buy the inverters? Alibaba or local reseller ? Yes service@deye.com.cn Bought on Alibaba.



So on the slave unit both MPPT's Volt goes down (and so the Watts produced) ? Yes on both MPPTs the volts go down about the same and the Watts fall to match the volts.
Did you check it with a multimeter/fluke? You must have 1-1 fuse for this strings. There you can check if V really down.
Did you check it with PV strings disconnected? So you see the Voc is OK.
Did you try to start only the slave unit ? If the problem does not occur at that time then it is a parallel/sharing problem.
Yes I check all voltages and the measured coming in from the solar panels match the values shown on the inverter screen.
You cannot run the slave unit on its own. Nor the master unit. If you shut one down they both shut down. However when I started the slave before connecting the two it also had this problem but I didn't investigate at the time. Its looking more and more like a hardware or software problem with the MPPTs. I was hoping there was some way to reset them or adjust them.

This is a very good unit. 1 phase and 22+22A MPPT.
Yes they are good units and manage the power exactly as they should but I do have another major problem with them. Where I am in Southern Philippines we loose the grid maybe every couple of weeks. This is usually intentional due to maintenance or load shedding but occasionally due to lightning or rain. The problem is that when the grid goes off both units trip. One on AC over current and the other on DC buss unbalanced. It is then impossible to reset them until the grid returns when they automatically reset. Very frustrating that there is no manual reset. If I turn the grid off and on there is no problem. Obviously when the grid is turned off at the sub station the islanding protection of the inverters is not working fast enough and hence they are overloading from the power draw into the network. This is not helped by the grid connection which is a single phase 13.2 kV with a 70 KVA let down transformer to 230 V. Here we are unusual and have a standard household supply of 230 V 60 Hz (no 120 V). Also single phase up to 250 A is not uncommon. Anyway it is looking like my only solution is to install a quicker islanding protection.
 

mrzed001

Voice of reason
Yes they are good units and manage the power exactly as they should but I do have another major problem with them. Where I am in Southern Philippines we loose the grid maybe every couple of weeks. This is usually intentional due to maintenance or load shedding but occasionally due to lightning or rain. The problem is that when the grid goes off both units trip. One on AC over current and the other on DC buss unbalanced. It is then impossible to reset them until the grid returns when they automatically reset. Very frustrating that there is no manual reset. If I turn the grid off and on there is no problem. Obviously when the grid is turned off at the sub station the islanding protection of the inverters is not working fast enough and hence they are overloading from the power draw into the network. This is not helped by the grid connection which is a single phase 13.2 kV with a 70 KVA let down transformer to 230 V. Here we are unusual and have a standard household supply of 230 V 60 Hz (no 120 V). Also single phase up to 250 A is not uncommon. Anyway it is looking like my only solution is to install a quicker islanding protection.
No way this is normal behavior.
So you feed into the grid (or to house with limiter out in AC in port ) and then grid is down. At that moment it should stop feeding into the grid.
And this unit has all the certificates from around the world, so it does, tested.
Something is not right on your setup or with your unit.
Can you make a pic and diagram of your system ? (Deye will ask for it also)
Also if inverter overloads it has a timer. After that it restarts itself.

We use 230V 50Hz here. But single phase 250A ... nope. Maybe they allow 60A single phase, and then they recommend to use 3 phase :) (and it is like 3x one phase)
 
Top