SunSynk Batteries: Cable and Fuse Sizing

[SRY]

After reading numerous posts on this subject, I thought I would consolidate the following:

Having read the various SunSynk Manuals (3.6/5Kw and 8kw inverter), I still find the information regarding wire gauge sizing and fuse disconnect sizes for the batteries a tad bit confusing/contradictory.

For instance, in the 3.6/5Kw manual, it states that the wire size for the battery connection should be 25mm but neglects to clarify if this is for a 5kw, 10Kw or 15kw battery? As the wire sizes are “apparently” different for each battery size respectively, if you order the 5kw vs 10Kw vs 15kw battery wire set for the SunSynks?

BUT after ordering a 10Kw battery wire set, it was exactly the same size (25mm) as my 5KW set, I ordered on my initial setup. So, either I received the incorrect wire set or there is no difference between the 5kw and 10kw wire sets that are sold?

The manuals state the following:

3.6/5Kw Inverter Manual:

·        Battery wire connection size = 25mm

·        Battery Fuse/disconnect = 150A

 

8Kw Inverter Manual:

·        Battery wire connection size = 50mm (single phase) & 70mm (3 Phase)

·        Battery Fuse/disconnect = 250A

As a side notes:

·        I’ve seen lots of posts with pics on this forum were 160A fuse/disconnects have been used on 8Kw inverters for the batteries – is this fine? If so, why?

·        There is no way to pass 2 x 50mm wires around the provided magnetic ring….I know! I’ve tried! Best suggestion for this problem?

 

10Kw Inverter Manual (Not available for single phase):

·        Battery wire connection size = 95mm (3 Phase) - single phase unknown?

·        Battery Fuse/disconnect = 300A

 

12Kw Inverter Manual (Not available for single phase):

·        Battery wire connection size = 120mm (3 Phase) - single phase unknown?

·        Battery Fuse/disconnect = 300A

 

So my question is, which component dictates the sizing of the wire? The Inverter or the Battery or both?

Bottom line is, I would like to know that if I want to upgrade a 5Kw SunSynk Inverter with a 10kw or 15kw Battery, do I need to increase the wire size? (Should answer the above question then)

And the same for increasing battery sizes on a 8kw, 10kw or 12Kw single phase inverter?

Any info on this “rabbit hole” would be appreciated.

[Scorp007]

Lots of info. 

My short answer would be the installer should know what size to fit. 

The fuse is about 30-50% higher than the maximum current that can be produced by the source. In this case the battery size dictates the size. If the future will be extra batteries then one can already fit a thicker cable to not having to change in future. 

Not sure what you mean by magnetic ring. Is this inside the inverter. 

[SRY]

Thanks, but I am the installer and I don't know what size to fit, thus my query. 

Perhaps you not familiar with the SunSynk inverters but the 8kw Inverter comes with a magnetic ring for the battery connection; check page 12 and 16 of the 8Kw manual to see what I'm referring too.

[GreenFields]

12 minutes ago, SRY said:

Thanks, but I am the installer and I don't know what size to fit, thus my query. 

Perhaps you not familiar with the SunSynk inverters but the 8kw Inverter comes with a magnetic ring for the battery connection; check page 12 and 16 of the 8Kw manual to see what I'm referring too.

My 2c' worth. I'm going to see it the other way around, and start with the maximum charge and discharge currents on the inverter. For the 5kW inverter it's I think 115A, and on the 8kW inverter it's 190A, so it's based on the power ratings of the inverter at approx 48V. So under normal operation except for transient surges you should not be exceeding that Amp value significantly, and accordingly they've specified the fuse rating at 150A and 250A respectively, with wiring sizes to match. No matter how much battery capacity you install, for me it's the inverter and its rated power that should dictate the maximum discharge limit in the event of a fault, even if the batteries could comfortably push out more current.

The magnetic ring you're referring to - if you mean the CT coil - is not intended to be fitted to a battery cable. It must go onto the incoming AC mains wiring. I think you need to re-read that section of the manual carefully.

 

[TaliaB]

4 hours ago, SRY said:

Perhaps you not familiar with the SunSynk inverters but the 8kw Inverter comes with a magnetic ring for the battery connection; check page 12 and 16 of the 8Kw manual to see what I'm referring too.

@Scorp007 @GreenFields

They are ferrite (magnetic) rings, over cables in order to suppress noise and filter out unwanted external interference for battery and bms cables.

@SRY

Which battery are you referring to. If you are using SunSynk 5kwh batteries they come with 25mm² cables/ battery. Each battery cable set uses 1 ferrite ring the pos and neg cables needts to be wrapped around twice .  If you use these batteries in parallel you either need to use 1 disconnect/ battery or use a busbar connecting X amount of batteries to the busbar, from the busbar to the battery disconnect use either 50mm² , 70mm² or 95mm²depending on the amount of batteries in parallel with fuse rating you mentioned above. Do the same from disconnect to inverter.The Bms cable also need to be wrapped 4x around a seperate ferrite coil as indicated in the manual. 

Ps. As you indicated it is not always possible to fit the ferrite coil close to the inverter with cables>25mm² 

OR

 

Edited July 15 by TaliaB
Ps added comment

[Scorp007]

36 minutes ago, TaliaB said:

@Scorp007 @GreenFields

They are ferrite (magnetic) rings, over cables in order to suppress noise and filter out unwanted external interference for battery and bms cables.

@SRY

Which battery are you referring to. If you are using SunSynk 5kwh batteries they come with 25mm² cables/ battery. Each battery cable set uses 1 ferrite ring the pos and neg cables needts to be wrapped around twice .  If you use these batteries in parallel you either need to use 1 disconnect/ battery or use a busbar connecting X amount of batteries to the busbar, from the busbar to the battery disconnect use either 50mm² , 70mm² or 95mm²depending on the amount of batteries in parallel with fuse rating you mentioned above. Do the same from disconnect to inverter.The Bms cable also need to be wrapped 4x around a seperate ferrite coil as indicated in the manual. 

OR

 

Thanks for helping out as usual. You highlighted the important aspect of busbar vs batteries connected in parallel via 1 set of fuse disconnect. 

Thanks for the information around the ferrite cores. Not an item that got mentioned a lot in other topics. 

@GreenFields I had the same line as your post but then changed it to the source power.

My reason was in case of using a very small battery it is sometimes used just to be able to start a high surge load in which case I would want to protect the battery from too a high current than to select as per the maximum the inverter can use. 

For me this is where one could look at the detail around the actual installation. Not 1 size fits all.

 

Edited July 15 by Scorp007

[GreenFields]

40 minutes ago, Scorp007 said:

Thanks for the information around the ferrite cores. Not an item that got mentioned a lot in other topics. 

Thanks @TaliaB, was not aware, and I humbly stand corrected/educated.

[TaliaB]

4 minutes ago, GreenFields said:

Thanks @TaliaB, was not aware, and I humbly stand corrected/educated.

No problem we all learn on a daily basis but in your defence the ferrite rings more commonly known as ferrite beads in hf applications is not always mentioned and not always fitted by installers. I normally always implement the ferrite coils on the bms cable at the inverter terminal but the battery ferrite coil is difficult if you exceed 25mm² especially the position indicated in the manual( as close as possible to inverter battery terminal). 

[SRY]

@TaliaB Thanks for your feedback, your inputs to my questions are always very helpful and greatly appreciated! 

As you've stated, yes I am referring to the ferrite ring (stated in the manual as "magnetic ring") supplied with the 8Kw SunSynk inverters. My 5kw SunSynk inverter did not come with this ring. They only supply 1 ring and it's not possible to wrap 2 x 50mm cables around a single ring twice. Perhaps if you can purchase another one, then running 1 cable in each ring might work? I'm assuming that you placed the rings in the boxes you have circled in pic 1 of your post or are those housing the busbars? Wrapping the BMS cable in the smaller ferrite ring is not an issue.

Just to clarify, I'm referring specifically to SunSynk batteries ONLY (the 5Kw, 10Kw and 15Kw sizes). I'm also only referring to installing 1 battery per inverter. No other parallel connected batteries.

So, perhaps to rephrase my question as follows:

If I have 5kw SunSynk Inverter and I want to upgrade the battery to either a:

• 10kw SunSynk Battery - do I need to upgrade the wire size to 50mm or
• 15kw SunSynk Battery - do I need to upgrade the wire size to 75mm?

AND the same question applied to a 8Kw, 10Kw or 12Kw Inverter, upgrading batteries from 5Kw to 10Kw and 15Kw respectively?

This is what is not clear in the Manuals supplied by SunSynk? Cos if you go by the manual, you would just use 25mm wire size for a 5KW SunSynk inverter for all battery sizes and the above mentioned wire sizes for 8kw, 10Kw and 12Kw inverters respectively?

 

 

[abd7]

10 hours ago, TaliaB said:

@Scorp007 @GreenFields

They are ferrite (magnetic) rings, over cables in order to suppress noise and filter out unwanted external interference for battery and bms cables.

@SRY

Which battery are you referring to. If you are using SunSynk 5kwh batteries they come with 25mm² cables/ battery. Each battery cable set uses 1 ferrite ring the pos and neg cables needts to be wrapped around twice .  If you use these batteries in parallel you either need to use 1 disconnect/ battery or use a busbar connecting X amount of batteries to the busbar, from the busbar to the battery disconnect use either 50mm² , 70mm² or 95mm²depending on the amount of batteries in parallel with fuse rating you mentioned above. Do the same from disconnect to inverter.The Bms cable also need to be wrapped 4x around a seperate ferrite coil as indicated in the manual. 

Ps. As you indicated it is not always possible to fit the ferrite coil close to the inverter with cables>25mm² 

OR

 

If one uses shielded cat5e cables for battery comms etc, does that negate the need for these ferrite rings? 

[TaliaB]

2 hours ago, abd7 said:

If one uses shielded cat5e cables for battery comms etc, does that negate the need for these ferrite rings? 

Maybe, it is supplied with the 8kw inverters so i use it, CANbus has a tendancy to be temperamental RS485 not so much.

[TaliaB]

10 hours ago, SRY said:

boxes you have circled in pic 1

That is the busbars one for each off the 2 batteries i don't think there is any point fitting the ferrite rings on the batt wires that far away from the inverter.

[SRY]

1 hour ago, TaliaB said:

That is the busbars one for each off the 2 batteries i don't think there is any point fitting the ferrite rings on the batt wires that far away from the inverter.

Thanks, makes sense.

Will post on the SunSynk forum regarding the wire sizes for the different battery sizes and see if anyone has any input. Thanks for your input.  

[PowerUser]

21 hours ago, SRY said:

So my question is, which component dictates the sizing of the wire? The Inverter or the Battery or both?

The inverter, not the battery dictates the sizing of the wire and fuses.

[TaliaB]

1 hour ago, SRY said:

Thanks, makes sense.

Will post on the SunSynk forum regarding the wire sizes for the different battery sizes and see if anyone has any input. Thanks for your input.  

In the inverter manuals 5kw= 35mm² 8kw= 50mm² and 16kw= 50mm² i have used 70mm² on Sunsynk 8kw but the reason was for longer battery cable runs.( volt drop)

[Gambit]

I didn't get the ferrite rings with my 8Kw SunSynk inverter 2 years ago. I wonder if they will help with all the noise I get on my HF radio. It will be difficult to test as i don't think the installer left a lot of slack in the battery cables.

Edited July 16 by Gambit

[TaliaB]

1 hour ago, Gambit said:

I didn't get the ferrite rings with my 8Kw SunSynk inverter 2 years ago. I wonder if they will help with all the noise I get on my HF radio. It will be difficult to test as i don't think the installer left a lot of slack in the battery cables.

That is strange never found one that didn't have the 2 ferrite coils. Maybe your installer never fitted them.

These work similar to the ones you find on VGA cables. The DC power also conducts broadband spectrum on unbalanced impedance wires from the switched current transients. The purpose of this Ferrite is to act as a BALUN or to BALance UNbalanced lines at RF frequencies. The other functional name is a Common Mode (CM) Choke. Since the AC-DC converters carry lots of harmonics up to 10MHz this ferrite raises the impedance of both lines DC+/- such that they become balanced radiators and thus cancel each other out for far-field EMI emissions. It might help you never know ask your installer to fit one as close as possible to the battery terminal at the inverter.

Edited July 16 by TaliaB

[Gambit]

1 hour ago, TaliaB said:

That is strange never found one that didn't have the 2 ferrite coils. Maybe your installer never fitted them.

These work similar to the ones you find on VGA cables. The DC power also conducts broadband spectrum on unbalanced impedance wires from the switched current transients. The purpose of this Ferrite is to act as a BALUN or to BALance UNbalanced lines at RF frequencies. The other functional name is a Common Mode (CM) Choke. Since the AC-DC converters carry lots of harmonics up to 10MHz this ferrite raises the impedance of both lines DC+/- such that they become balanced radiators and thus cancel each other out for far-field EMI emissions. It might help you never know ask your installer to fit one as close as possible to the battery terminal at the inverter.

It is highly possible that my installer didn't fit them as they made so many other mistakes that we are no longer on speaking terms. I had to get another company to fix basic things like the neutral earth bonding etc. I'll probably speak to that company and see what they have to say.

Edited July 16 by Gambit