I'd like to ask for comments on the topic of safety of higher power systems in a van.
- Use case: Occasional simultaneous use of an induction cooktop with brief microwave use, always within all manufacturer specs including the inverter.
- System: 400Ah LiFePO4 and a 3000W inverter in a Sprinter van, plus moderate solar & alternator charging (charging is not the topic here, focus is on inverter loads and safety)
I don't want to debate the need for higher power in this thread, everyone's needs are different. I've already been told that I may just want to stay home where there is lots of AC power. But hey, to each their own. The topic here is safety. I was also told by one of several experienced installers I have spoken with that it would be a big mistake to do this, it is outside of safe limits for a van, and that I have no idea what I am getting into.
OK fair enough, I'm always ready to learn, and safety is critical. That's why I talk to experts, including those on this forum. So following is my understanding so far on doing such a system. I'll work up a schematic, but I think these are general questions applicable to any such system. I welcome any constructive feedback on safety, and references are always helpful. And yes, I am also consulting with experienced installers, industry specifications, and directly with the vendors. The Sprinter forum is a valuable additional resource I am using.
1) 200A in 4/0 cable
I was told that running DC loads of 200A continuous is quite risky and likely requires cables larger than 4/0 to be safe. I don't understand that. 4/0 wire has an ampacity rating of 448A for single dry wire, 270A even if wet and in a 122F engine room.
The cables in question would connect from battery bank through Class T fuse and battery switch to inverter, all inside a 3 foot long non-conducting box. Voltage drop not an issue with these short cables, ampacity is the limiting factor. I would think 200A is safely achievable in this application using 4/0 cable. Are there other factors I should be considering?
2) Lithium batteries inside the van
I've also been told that lithium batteries inside the van are inherently unsafe. That was a surprise for me. I'm aware that other lithium chemistries are fire hazards, but no LiFePO4. If you have comments on the safety risks of batteries inside, please educate me. Again, references are helpful.
3) Inverter peak loads:
Use case as I mentioned is ~5 minute use of microwave while an induction cooktop is already in use.
Specs for a Victron 3000VA Inverter/Charger:
- 3000VA continuous at 25C (77F)
- 2400W continuous output power at 25C (77F)
- 2200W continuous output power at 40C (104F)
- 1700W continous output power at 65C (150F)
- 30% overload ok up to 30 minutes
- 6000W peak power up to 2 minutes
- 93% max efficiency
Inverter AC load at 104F
Victron specs allow running at 30% above continuous rating, for durations less than 30 minutes. And an amazing 6000W for 2 minutes. My use case is 5 minutes, maybe a couple times a day. So the 30 minute spec applies here, and limiting further to a 5 minute peak load just adds margin due to lower heating in the inverter FETs than with 30 minutes.
This means 2860W available for 30 minutes if the inverter is sitting at 104F ambient inside the electrical cabinet. More if cooler, less if warmer. As with all inverters, user needs to manage what's plugged in. And actual devices to be selected after measurements of devices and of actual ambient temperature rise for the inverter in its cabinet.
DC load at 104F Ambient
- Inverter: 2860W @ 120VAC, 40C, and 93% efficiency = 256A DC for <30 minutes
- DC loads: Worst case, assume also maxed out at 100A
- 4/0 wire is rated at 378A ampacity continuous at 50C/122F, so 356A is in spec
- This is a worst worst case sum of several peaks: max AC load for 30 minutes, max DC load, 104F ambient, still meets all specs.
A detailed ABYC type load analysis accounting for actual intermittent and continuous loads would come in with more margin, and I do plan to do that. But I believe this provides a useful frame for discussion.
Conclusion
An induction cooktop plus microwave seems feasible to implement safely using this 3000W inverter. A detailed load analysis would be needed before finalizing appliance selection, if needed for safety margin. But selecting from induction cooktops in the 1200-1800W range plus a microwave in the 600-1000W range, there should be a viable and safe solution.
OK, comments invited.
- Use case: Occasional simultaneous use of an induction cooktop with brief microwave use, always within all manufacturer specs including the inverter.
- System: 400Ah LiFePO4 and a 3000W inverter in a Sprinter van, plus moderate solar & alternator charging (charging is not the topic here, focus is on inverter loads and safety)
I don't want to debate the need for higher power in this thread, everyone's needs are different. I've already been told that I may just want to stay home where there is lots of AC power. But hey, to each their own. The topic here is safety. I was also told by one of several experienced installers I have spoken with that it would be a big mistake to do this, it is outside of safe limits for a van, and that I have no idea what I am getting into.
OK fair enough, I'm always ready to learn, and safety is critical. That's why I talk to experts, including those on this forum. So following is my understanding so far on doing such a system. I'll work up a schematic, but I think these are general questions applicable to any such system. I welcome any constructive feedback on safety, and references are always helpful. And yes, I am also consulting with experienced installers, industry specifications, and directly with the vendors. The Sprinter forum is a valuable additional resource I am using.
1) 200A in 4/0 cable
I was told that running DC loads of 200A continuous is quite risky and likely requires cables larger than 4/0 to be safe. I don't understand that. 4/0 wire has an ampacity rating of 448A for single dry wire, 270A even if wet and in a 122F engine room.
The cables in question would connect from battery bank through Class T fuse and battery switch to inverter, all inside a 3 foot long non-conducting box. Voltage drop not an issue with these short cables, ampacity is the limiting factor. I would think 200A is safely achievable in this application using 4/0 cable. Are there other factors I should be considering?
2) Lithium batteries inside the van
I've also been told that lithium batteries inside the van are inherently unsafe. That was a surprise for me. I'm aware that other lithium chemistries are fire hazards, but no LiFePO4. If you have comments on the safety risks of batteries inside, please educate me. Again, references are helpful.
3) Inverter peak loads:
Use case as I mentioned is ~5 minute use of microwave while an induction cooktop is already in use.
Specs for a Victron 3000VA Inverter/Charger:
- 3000VA continuous at 25C (77F)
- 2400W continuous output power at 25C (77F)
- 2200W continuous output power at 40C (104F)
- 1700W continous output power at 65C (150F)
- 30% overload ok up to 30 minutes
- 6000W peak power up to 2 minutes
- 93% max efficiency
Inverter AC load at 104F
Victron specs allow running at 30% above continuous rating, for durations less than 30 minutes. And an amazing 6000W for 2 minutes. My use case is 5 minutes, maybe a couple times a day. So the 30 minute spec applies here, and limiting further to a 5 minute peak load just adds margin due to lower heating in the inverter FETs than with 30 minutes.
This means 2860W available for 30 minutes if the inverter is sitting at 104F ambient inside the electrical cabinet. More if cooler, less if warmer. As with all inverters, user needs to manage what's plugged in. And actual devices to be selected after measurements of devices and of actual ambient temperature rise for the inverter in its cabinet.
DC load at 104F Ambient
- Inverter: 2860W @ 120VAC, 40C, and 93% efficiency = 256A DC for <30 minutes
- DC loads: Worst case, assume also maxed out at 100A
- 4/0 wire is rated at 378A ampacity continuous at 50C/122F, so 356A is in spec
- This is a worst worst case sum of several peaks: max AC load for 30 minutes, max DC load, 104F ambient, still meets all specs.
A detailed ABYC type load analysis accounting for actual intermittent and continuous loads would come in with more margin, and I do plan to do that. But I believe this provides a useful frame for discussion.
Conclusion
An induction cooktop plus microwave seems feasible to implement safely using this 3000W inverter. A detailed load analysis would be needed before finalizing appliance selection, if needed for safety margin. But selecting from induction cooktops in the 1200-1800W range plus a microwave in the 600-1000W range, there should be a viable and safe solution.
OK, comments invited.
vic