So my current setup is 2*us3000c batteries, with a sunsynk 8kw inverter (have panels etc but dont think relevant to this question).
The connection from my pylontechs is the pylontech connectors on 35mm cables  (alvern permopower welding cables), about 0.5m to a battery disconnector with 160a fuses, then from there another 0.5m on the 35mm cables to the inverter.

If i add 2 more US3000 batteries, i assume the 35mm cables will support that (as well as the fuses)? or would i need to make any changes to my current setup like an additional pylontech cable pack from the batteries to the battery disconnector, would i need a busbar etc?

realistically I doubt we will ever draw the max amperage from the batteries, and if we got close would probably be for a very short period

Hi Woody. 3 x Us3000c batteries can deliver 5kw(+-100A) of power. The 35mm² cable can handle that  but with 4 batteries I would by a extra cable pack.

The 8kw can draw 190 Amp's from the batteries when pulling full load. You will have to limit that on the inverter to protect the batteries. For now the 160Amp fuses should be sufficient.

 

ok thank you, and i guess i will have to double up the cables from battery to battery disconnector/fuse, and then double up from the disconnector to inverter?  or i guess i could just limit the inverter to 100a from batteries? (this should accommodate my load at any one time tbh, but the extra storage capacity would be nice)

42 minutes ago, Woody said:

ok thank you, and i guess i will have to double up the cables from battery to battery disconnector/fuse, and then double up from the disconnector to inverter?  or i guess i could just limit the inverter to 100a from batteries? (this should accommodate my load at any one time tbh, but the extra storage capacity would be nice)

The 4 x Pylontech Us3000c can discharge at 133 amps the 35mm² cable will be adequate no need to double up 35mm² cable. The chart below is based on approved SABS 1574 standards and ratings:

Awesome TaliaB, so i wouldnt even need to double up the cables from the battery to disconnector/fuse?
sorry for so  many questions, just making sure i understand it 100%

1 hour ago, Woody said:

Awesome TaliaB, so i wouldnt even need to double up the cables from the battery to disconnector/fuse?
sorry for so  many questions, just making sure i understand it 100%

The 35mm² cable can carry 200A@100%duty cycle your maximum draw from your 8kw inverter is 190 amps but you will limit the current up to 130 amps to accommodate your batt max current. The 160amp fuse is also below the 200amp of the 35mm² cable so cable is well protected, you good to go with single 35mm² cable.

 

 

 

9 hours ago, TaliaB said:

The 35mm² cable can carry 200A@100%duty cycle your maximum draw from your 8kw inverter is 190 amps but you will limit the current up to 130 amps to accommodate your batt max current. The 160amp fuse is also below the 200amp of the 35mm² cable so cable is well protected, you good to go with single 35mm² cable.

 

 

 

 AFAIR, the Surlok connector on the pylontechs are rated for 120A. They only support crimping to 25mm², so I would double up.

14 minutes ago, P1000 said:

 AFAIR, the Surlok connector on the pylontechs are rated for 120A. They only support crimping to 25mm², so I would double up.

Ah fair point i was under the impression the Pylontech used the 8mm connector that is rated at 120-200amps but if they use the 5.7mm connector that is rated for 100-120amp then yes you will have to double up not because of the conductor but rather the connector rating. @Woodyplease confirm the wire size as indicated below.

15 hours ago, TaliaB said:

The 4 x Pylontech Us3000c can discharge at 133 amps the 35mm² cable will be adequate no need to double up 35mm² cable.

Right. It's not the size of the battery that dictates the cable size, it's the load. If you have 10kW inverter it can draw at maximum 200A at peak load. But that happens most likely seldom if at all and for very short time. The mean load in my household with electric cooking is around 3 to 4kW with peaks up to 6kW. My batteries are happy with 25mm² cables.

1 hour ago, Beat said:

Right. It's not the size of the battery that dictates the cable size, it's the load. If you have 10kW inverter it can draw at maximum 200A at peak load. But that happens most likely seldom if at all and for very short time. The mean load in my household with electric cooking is around 3 to 4kW with peaks up to 6kW. My batteries are happy with 25mm² cables.

 

15 hours ago, TaliaB said:

The 35mm² cable can carry 200A@100%duty cycle your maximum draw from your 8kw inverter is 190 amps but you will limit the current up to 130 amps to accommodate your batt max current.

 

@TaliaB the wires in the picture (connected to the battery) are 35mm2, sound like doubling up the cables from battery to fuse is probably the safest and quite easy option. the 35mm2 cables from the fuse to inverter from the discussions above look like they dont need to be doubled at least
@Beat yeah my loads tend to be small, we are on egoli gas, and the electric geyser and oven are on non essentials. in a year of having only 2*US3000c the inverter has only shut off twice when we had visitors who didnt realise there's a reason we dont turn on the kettle, microwave and heater on at the same time, in the evening when there is loadshedding (since then we have put in gas heaters as well).

and then as an aside, when installing the 2 secondhand  US3000  (seller says updated to latest firmware) batteries to connect to my 1 year old 2*US3000c batteries, they should have no compatibility issues? sorry so many questions, trying to diy the installation of these batteries if possible rather than getting an installer to come in for what looks on paper like quite a simple install.

and thank you everyone for the input! really appreciate it!

1 hour ago, Woody said:

when installing the 2 secondhand  US3000  (seller says updated to latest firmware) batteries to connect to my 1 year old 2*US3000c batteries, they should have no compatibility issues?

No you shouldn't have any compatibility issues Pylontech is quite forgiving when it comes to adding modules. Should you have issues i am sure it will be minor issues nothing you won't be able to sort with some advice from forum members.

Comfortably ran 4 x US3000 on a single set of 2M long Pylontech cables for over 3 years with my Victron Quattro 48/8000. Only started to double up cables when adding the 5th and 6th which are US3000C. No issues with compatibility between US3000C and US3000. The US3000 were updated to v3.4 of the firmware prior to introducing the US3000C as the new master. It's best to ensure the SOC is approximately the same when introducing additional batteries. 

 

thank you everyone for all the info and advice, out of curiosity what is the actual differences between us3000b's and us3000c's?

Edited April 28, 20242 yr by Woody

US3000C supports 90% DOD while the US3000 only 80% DOD. 

4 hours ago, JKKM said:

US3000C supports 90% DOD while the US3000 only 80% DOD. 

95% DOD for the C range.

Thank you everyone for the assistance, iv connected one of the us3000b cables, balanced them etc and I think I've made all the right connections and settings in my sunsynk inverter, but it looks like my battery BMS isn't communicating with the inverter. Am I right that it's not communicating and anything that sticks out as obviously wrong?

False alarm! All I had to do is give the can bus cable a little extra nudge into the port! Works amazingly now