Building my own pseudo(Powerwall)

[L-P-G]

You have contactors on the DC side to disconnect the battery when the voltage gets too low or too high, that's not overkill. That's best practice to prevent killing your batteries.

Are you getting the discharge rate of 280A because the battery is 280Ah? If so, that is incorrect. Ah is a measurement of current over time not discharge rates. For example here are the specs for the modules on my pack.


Capacity (ideal) 5.2 kWh (233 Ah)
Discharge Current (max, 3s) 1,520 A (~6.5C)
Discharge Current (10s) 1,000 A (~4.3C)
Discharge Current (continuous) 233 A (~1C)
Discharge Power (max, 3s) 30 kW
Discharge Power (continous) 5 kW
Charge Power (max, 10m) 8 kW
Charge Power (continous) 5 kW

As you can see the capacity of each battery module in the pack is different than the discharge current. Also I have my modules wired in 2S7P, that means I'm spreading the load across 14 modules. So if I were to take the max output of my inverter 250A (12kW) I would need to divide it by 14 since the load will be divided across all my modules in the pack. That would mean at the worse case scenario when inverting 12kW each module would have a load of [email protected] which is way lower than 233A.

 

[mspohr]

You have contactors on the DC side to disconnect the battery when the voltage gets too low or too high, that's not overkill. That's best practice to prevent killing your batteries.

Are you getting the discharge rate of 280A because the battery is 280Ah? If so, that is incorrect. Ah is a measurement of current over time not discharge rates. For example here are the specs for the modules on my pack.


Capacity (ideal) 5.2 kWh (233 Ah)
Discharge Current (max, 3s) 1,520 A (~6.5C)
Discharge Current (10s) 1,000 A (~4.3C)
Discharge Current (continuous) 233 A (~1C)
Discharge Power (max, 3s) 30 kW
Discharge Power (continous) 5 kW
Charge Power (max, 10m) 8 kW
Charge Power (continous) 5 kW

As you can see the capacity of each battery module in the pack is different than the discharge current. Also I have my modules wired in 2S7P, that means I'm spreading the load across 14 modules. So if I were to take the max output of my inverter 250A (12kW) I would need to divide it by 14 since the load will be divided across all my modules in the pack. That would mean at the worse case scenario when inverting 12kW each module would have a load of [email protected] which is way lower than 233A.

Probably should divide by 7 for current since you have a 7P setup.

 

[L-P-G]

Probably should divide by 7 for current since you have a 7P setup.

Yep, you're right. That's what I get for browsing forums when I'm supposed to be asleep.

That's still 35A which is well within the limits of each module.

 

[LV_Solar]

It's super important to protect the batteries with a Battery Management system to watch your draw, charge as well as low and high voltages. L-P-G is running a smart BMS to let him do that kind of thing. A good BMS will allow you to monitor all those numbers and not solely rely on a fuse/breaker if things go wrong.

 

[Xianrecords]

You have contactors on the DC side to disconnect the battery when the voltage gets too low or too high, that's not overkill. That's best practice to prevent killing your batteries.

Are you getting the discharge rate of 280A because the battery is 280Ah? If so, that is incorrect. Ah is a measurement of current over time not discharge rates. For example here are the specs for the modules on my pack.


Capacity (ideal) 5.2 kWh (233 Ah)
Discharge Current (max, 3s) 1,520 A (~6.5C)
Discharge Current (10s) 1,000 A (~4.3C)
Discharge Current (continuous) 233 A (~1C)
Discharge Power (max, 3s) 30 kW
Discharge Power (continous) 5 kW
Charge Power (max, 10m) 8 kW
Charge Power (continous) 5 kW

As you can see the capacity of each battery module in the pack is different than the discharge current. Also I have my modules wired in 2S7P, that means I'm spreading the load across 14 modules. So if I were to take the max output of my inverter 250A (12kW) I would need to divide it by 14 since the load will be divided across all my modules in the pack. That would mean at the worse case scenario when inverting 12kW each module would have a load of [email protected] which is way lower than 233A.

Thanks. I am not using the Tesla Module but 280Ah LifePo4. I have a 1P16S scheme and the discharge rate of my battery is 1C. So I would be expecting a max. discharge of 280A. I am planning on getting another 16S in the future. I also have a Chargery BMS to keep the cells balanced and 2 contactors on the DC Side for low voltage cutoff and overcharge.

In my 1P16S setting with a max discharge of 280A, I was wondering what would happen if my load ask for more that 280a. The inverter can produce continuously 312.5A. I guess it would probably be ok for the batteries if the >280A is not too long ?

Also, I was talking to the Sigineer Sales Rep and I think he confused me and I am no longer sure about the exact specs of the 15kW inverter. In the documentation, it says that the bypass mode of the 15kW is 100A. So I would expect that the breakers on the AC Input and AC output of the inverter are 100A. But he told me that the Input is 100A and the output is 63a. That does not make much sense to me if the bypass is rated for 100A. Any help here ?

Thanks

Christian

 

[MP3Mike]

But he told me that the Input is 100A and the output is 63a. That does not make much sense to me if the bypass is rated for 100A. Any help here ?

Well 63A is the 15kW it is rated for. Maybe the extra power in the "bypass" mode is used to re-charge the batteries? (I'm assuming that it has that functionality.)

 

[LV_Solar]

Thanks. I am not using the Tesla Module but 280Ah LifePo4. I have a 1P16S scheme and the discharge rate of my battery is 1C. So I would be expecting a max. discharge of 280A. I am planning on getting another 16S in the future. I also have a Chargery BMS to keep the cells balanced and 2 contactors on the DC Side for low voltage cutoff and overcharge.

In my 1P16S setting with a max discharge of 280A, I was wondering what would happen if my load ask for more that 280a. The inverter can produce continuously 312.5A. I guess it would probably be ok for the batteries if the >280A is not too long ?

Also, I was talking to the Sigineer Sales Rep and I think he confused me and I am no longer sure about the exact specs of the 15kW inverter. In the documentation, it says that the bypass mode of the 15kW is 100A. So I would expect that the breakers on the AC Input and AC output of the inverter are 100A. But he told me that the Input is 100A and the output is 63a. That does not make much sense to me if the bypass is rated for 100A. Any help here ?

Thanks

Christian

You should follow the specifications for your battery. If the charge or discharge is out of spec, you should not allow it. This is how you destroy batteries and/or start fires. Don't pull more than your maximum safe AMPS from the Sigineer and set the Charge Rate on the Sigineer to less than maximum. The BMS should be set to cut off the batteries if you go out of spec, and if set up safely your BMS will never have to do that.

 

[Xianrecords]

Thank you. Actually after looking at a few YouTube videos of the 15kW inverter, it looks like the Input breaker on AC is 100A and the output breaker is 80A. So I guess the bypass mode is not a True input/output bypass but some of that power is meant to be directed to charging the battery.

I agree with @LV_Solar recommendation. For my 1P16S setup, the max Amp on the AC Side should be: 48*280/240 = 56A so I will go with a 50A breaker on my SubPanel. When I migrate to the 2P16S, then I will use a 80A breaker on the sub panel to match the one on the inverter.

 

[L-P-G]

The sigineers use a 19kW ATS. That's why you're seeing the deltas in your numbers, for example my 12kW can invert 12kW when running off the battery but while on standby the ATS will bypass 19kW.

Because of that you need to ensure that your wiring and breakers are rated to 19kW and not your inverters rated output. Failing to do so could leave you in a situation where the inverter will be on bypass mode, and you house loads could go over 15kW and melt a cable to trip a breaker. When in doubt, oversize.

 

[mspohr]

The sigineers use a 19kW ATS. That's why you're seeing the deltas in your numbers, for example my 12kW can invert 12kW when running off the battery but while on standby the ATS will bypass 19kW.

Because of that you need to ensure that your wiring and breakers are rated to 19kW and not your inverters rated output. Failing to do so could leave you in a situation where the inverter will be on bypass mode, and you house loads could go over 15kW and melt a cable to trip a breaker. When in doubt, oversize.

Good advice. My Outback Skybox can deliver 5kW from batteries but bypass 10 kW from the grid so breakers and wire is sized for 10 kW.

 

[Xianrecords]

Yes. The 100A input and 80A output will have the wires rated for these Amps.

 

[Xianrecords]

I am now facing a new issue. I submitted my Battery Backup plan to my city and the reviewer is now asking for UL Certification of the 15kW Inverter. I reached out to Sigineer and they do not have it for any of their product.
Does anyone know how to get a 12kW/15kW UL Approved inverter ? I have been looking all over. Found a product from AIMS for $4000 instead of $2200 for the Sigineer. How did you get around the issue with your own city ?

Thank you

 

[miimura]

UL listing takes a lot of effort on the part of the manufacturer. That is the main reason that listed products are more expensive. I don't see any way around it if you are getting permits and the city requires you to use UL listed products.

 

[L-P-G]

My AHJ didn't care about UL on non-grid

I am now facing a new issue. I submitted my Battery Backup plan to my city and the reviewer is now asking for UL Certification of the 15kW Inverter. I reached out to Sigineer and they do not have it for any of their product.
Does anyone know how to get a 12kW/15kW UL Approved inverter ? I have been looking all over. Found a product from AIMS for $4000 instead of $2200 for the Sigineer. How did you get around the issue with your own city ?

Thank you

My AHJ doesn't require UL for non-grid interactive inverters. In other words if it doesn't backfeed the grid which the sigineer does not.

You can look at the SMA Sunny Island, you can parallel 2 together and get 12kW. Outback Radian also has a parallelable 8kW but it's expensive. Magnum makes a few models that you can parallel but the highest output is 4kW.

Also AIMS is just a re-branded Sigineer, go online and look at pics and videos. Sigineer is the OEM for a lot of companies that just slap a different case or name and resell their product. If you try to get the UL cert from AIMS support they'll just give you the run around and send you their Intertek certificate. Before I found out my AHJ had that clause on the non-grid interactive inverters I was going down the same road as you trying to find a UL listed inverter, I emailed AIMS support asking for their certificate and after a number of emails they admitted to not being UL certified.

 

[Xianrecords]

I ended up having to switch to Sunny Island as my AHJ would not move on the UL requirement. I also decided to choose the Batrium BMS and I will include a 300A ABB DC shunt trip breaker at the output of the battery.

I have a generic questions with regards to BMS turning off either a contactor or in my case the shunt trip breaker if the DC Voltage goes too low or if the BMS detects a cell voltage too low or a variation between cells too high.

In the situation, the BMS will trip the shunt trip breaker. How do I get out of that situation ? I mean if I turn back on the breaker assuming that the voltage is still too low as the inverter were not able to charge the battery, the BMS will keep tripping the breaker. Would I have to set a temporary lower discharge voltage in the BMS to allow the breaker to be on and for the inverter to charge the battery ?

Also, if anyone is familiar with the Sunny Island inverter/charger, there is a feature called time-controlled operation which allow the device to be put in inverter mode at specific time when the grid is on. (I assume that is what the feature is about). Because I am with PG&E in California and my rate is higher between 4pm to 9pm, I intend to use that feature. The question is what happens if you are on Time-Controlled operation and the Deep Discharge threshold kicks in. Will everything shuts down or will the inverter be smart enough to go back to the grid ?


Thank you

 

[L-P-G]

Your sunt trip breaker should is meant to be a safety disconnect, not a control device. In other words the the inverter should control the charging and discharging via its built in settings and turn on and off accordingly. If a situation arises where the inverter either fails to stop producing power when the battery is too low or it fails to stop solar production via freq shift or curtailing because the battery voltage is too high then the shunt breaker should be tripped.
At that point is up to you to find out what went wrong and why the safety breaker was tripped. I belive the barium can also communicate with the SI via Can or RS485.

 

[L-P-G]

FYI for anyone wanting to replicate my build. Jack Rickard from EVTV, the creator of the controller I'm using to interact with the modules has passed away. He ran a pretty small shop and other than his developer Collin and a couple employees he was a one man company.

In other words, that controller probably won't be available much longer and it is now abadonware. Use a SimpBMS instead.

 

[L-P-G]

Someone had asked me for a video of the xfer switch in action. Here it is.