Battery powered off-grid systems are quiet popular and 48vdc is the current voltage of preference. Unfortunately, most 48vdc inverters are simply a poor match for Tesla Battery Modules. Why?
The main problem is the Low Voltage Cutoff - the point of battery discharge where the inverter will shut down to protect the battery. Almost all 48vdc inverters have LVCO in the 42-44v range with a very very few able to handle batteries down to 40v.
Two Tesla Battery Modules in series are pretty much discharged at 36v. but they are only 50% discharged at 43.2v. And so with almost all inverters on the market you are leaving 30-50% of your battery capacity on the table. That means you have to purchase TWICE the battery capacity that you would need if the inverter simply operated down to the 36v cutoff.
The other issue is that many of these inverters will also charge your batteries from AC - the charger is built in. That's great, but they are traditionally designed for lead acid batteries. They may support a bewildering array of Pb chemistry types, but ALL of the charge curves they provide are deadly to Tesla Battery Modules. We advocate charging with a simple bulk current to 50.5volts and NO MORE.
Almost all inverters want to charge to something more like 56 volts with equalization phases as high as 60v. This will immediately DESTROY your Tesla Battery Module, not over time but the FIRST time it does so.
And of course most 48vdc inverters provide 4kw to 8kw of power max.
We have located an excellent quality 12 kilowatt inverter made in China that can do 36kw for 20 seconds. It charges at 110 amperes from 240vac. And we have commissioned them to provide a Low Voltage Cutoff of 39vdc and a charge limit of 50.5vdc - ideally tuned for the Tesla Battery Modules.
This inverter has two modes of operation that offer some very interesting flexibility.
AC PRIORITY MODE. This allows you to pass a grid voltage THROUGH the inverter to your loads and operates primarily on grid power. It will automatically charge your battery and cycle it every 15 days. But on loss of grid AC input, it will transfer to battery operation within a few milliseconds. It is an ideal "battery backup" system.
In BATTERY PRIORITY MODE, it does NOT pass through AC but rather generates all output power - up to 50 amps at 240vac continuously, from the battery. In the event the battery falls below the low voltage cutoff level, it will switch to the AC input and indeed recharge the battery at the same time. When the voltage reaches the resume level, in this case 47 volts, it will switch back to battery operation.
Finally, it features a generator start output to start a generator if the source is a generator rather than the grid.
Finally, this inverter features an optional remote control panel. We INCLUDE that with every inverter instead of making it an option.
Inverter Output Specifications:
- Continuous Output Power: 12,000 Watts
- Surge Rating: 36000 Watts (20 Seconds)
- Output Waveform: Pure Sine/Same as input (Bypass Mode)
- 100-110-120Vac / 220-230-240Vac
- Nominal Efficiency: >88% (Peak)
- Line Mode Efficiency: >95%
- Output Frequency: 50Hz +/- 0.3Hz / 60Hz +/- 0.3Hz
- Typical Transfer Time: 10ms (Max)
- THD: < 10% DC
- Nominal Input Voltage: 48.0Vdc
- Low Battery Alarm: 39.5.0Vdc
- Low battery Trip: 38.75.0Vdc
- High Voltage Alarm: 51.0Vdc
- Low battery Voltage Restart: 47.0Vdc
- Idle Consumption: 145 Watts
- Power Saver Mode Idle Consumption: 40 Watts
- Output voltage: Up to 50.5vdc
- Charger Rate: 110A
- Unit Weight: 174 lbs.
- Unit Size L x W x H: 23.3 x 16.3 x 7.9 inches
- Shipping Weight: 200 lbs.
- Shipping L x W x H 30 x 21.25 x 15.25 inches