Hello bright minds,
I am still pondering the full build of the Audi 13S battery packs I got that are brand new. Yes 13S isn't ideal I know but I'm not going to tear open the factory metal box they are in with the intent of trying to reconfigure things, I'll just end up breaking things. So 13S it is. Yes these are the evil blow up bombs NMC chemistry. The box (besides the factory one) being designed is being designed to survive massive energy release and over 3000F of heat protection in multiple layers, with exhaust systems. That's going to be a heck of a build. For now I want to get the fundamentals of the parallel setup right before doing anything.
See the drawing and my terrible penmanship. The plan is one JK bms (already tested on all three batteries) per battery pack. A Class T fuse on the main POS of each battery pack going up to the busbar rated for 1000V. From there there's only going to be one load connection out, I added another class T on the POS after the busbar, followed by a disconnect switch. Then I'm no sure if I need anything more before the inverter. Load = 50-70watts max (yes virtually nothing I know).
Questions: You can see some notes at the bottom I scribbled.
1. Since JK does active balancing and each pack has its own BMS, in a parallel setup...what is the best way to handle this for proper battery stability? Only one BMS doing active monitoring? All of them? None of them?
2. Best way to charge, should I charge each pack independently and and then reconnect them after validating the voltages are almost identical so there isn't a surge of energy transfer? Or can I charge in parallel essentially replacing the inverter for a SCC and all the safety bits that go with that.
3. Other safety measures. What am I missing? What else would you recommend I add? Should I add a disconnect switch for each POS before the busbar as well?
Each 13S pack has the following properties:
All this info will come in handy because I have 4 Renogy brand new batteries I bought, 24V/25ah each and they are going in parallel. They have their own internal BMS, which is nice and all and it says they balance themselves but I still plan to follow this similar type footprint. Is it allowed or safe to add a BMS to batteries like that have internal BMSs? Just be to be able to monitor each battery? I have a 500V shunt from them but I didn't know if there is a better way for me to be able to see how each battery is doing. I dont just want to throw some fuses on them and wire em up that scares me not being to "see" how each battery is doing. How is that normally handled??
Keep in mind this are "portable" packs, they do not stay connected to solar panels or SCCs, they are in boxes that have wheels so they can be placed in safe locations to power certain parts of the house. Mostly I've been building 16S LFP packs in steel enclosures right now, but these I'm kinda on my own in terms of design. I've read the battery documentation from Renogy it actually says the batteries can be paralleled up to 8 (I only have 4) and NO series connections allowed. Curious of what the community would design in that situation.
I appreciate any and all feed back on design and safety measures needed. These Audi batteries are the last of NMC batteries and the case I have to build is going to have to be ridiculous to protect myself in the worst case scenario. It's going to involve a lot of thick steel vent holes with proper handling of the venting, I'm going to add sensors from microcontrollers I program to give me warnings ahead of time for temp and VOCs, the BMS's will be set very conservatively for temp shutdown and other things. Thermal insulating fireglass will be used, CellblockEX pellets will be automatically setup in a manner to douse each pack in the event they heat up too much.
Everything will be thick steel, firebricks and the like. Fans will be used to remove exhaust as well as keep BMS's and other electrical parts cool and they will have a seperation barrier betwen the batteries and the busbars/bms's ect..and with multiple layers of protection. Fire extinguishers designed for Lithium fires have been purchased along with "worst case" fire supression canisters you throw at the fire and it goes off almost like a tear gas can the police use to smother, cool, and coat the batteries to extinguish them.
Honestly I'm not looking forward to the box build its going to be a huge PITA, expensive, and heavy (though it'll be on wheels).
Batteries will be charged conservitively and same with dishcharge. They are capable (video is out there to prove it) they can do about 150A continous (minor sag) when they are fully charged dropping slowly down to about 100A at shutoff (3V) and remaining just slightly warm). Now I would NEVER pull that kinda amperage. Like said my loads are stupid small under 100W. Routine checks on the IR (with quality expensive tools) will be performed to ensure batteries are staying within spec and healthy. As always I appreciate in advance your support, opinions and advice. This about safety and best to set that up for a worst case scenario. I don't know if I mentioned but the battery packs will be seperated by thick steel, so all three are not together so to speak. The hope there is, if one decides to become a bomb it doesn't take out the others with it. If all goes correctly it may start to vent, the battery will be doused automatically with CellBlockEX (designed to smother and put out NMC fires) and hopefully that stops it, if not the thick steel exhaust and other measures I discussed will serve as containment. I hope. I know someone is going to say just put them far away from your house as possible. Not possible. This is FL where its hot as hell pushing high 90's today and I have no where to put them in my yard I rent. If I did put em outside now I have to worry about adding weather (heavy rain) protection and it spirals. I understand the dangers, I've seen it, but also if done conservitive and safely they can be quite reliable and safe. I've used NMC for other things many times they are great. But yes they are little bombs, in this case 3 medium bombs if combined, one giant bomb. Hence looking for the best way to protect my self from a worst case (internal short/thermal runaway) situation.
Cheers,
Cyberfed
I am still pondering the full build of the Audi 13S battery packs I got that are brand new. Yes 13S isn't ideal I know but I'm not going to tear open the factory metal box they are in with the intent of trying to reconfigure things, I'll just end up breaking things. So 13S it is. Yes these are the evil blow up bombs NMC chemistry. The box (besides the factory one) being designed is being designed to survive massive energy release and over 3000F of heat protection in multiple layers, with exhaust systems. That's going to be a heck of a build. For now I want to get the fundamentals of the parallel setup right before doing anything.
See the drawing and my terrible penmanship. The plan is one JK bms (already tested on all three batteries) per battery pack. A Class T fuse on the main POS of each battery pack going up to the busbar rated for 1000V. From there there's only going to be one load connection out, I added another class T on the POS after the busbar, followed by a disconnect switch. Then I'm no sure if I need anything more before the inverter. Load = 50-70watts max (yes virtually nothing I know).
Questions: You can see some notes at the bottom I scribbled.
1. Since JK does active balancing and each pack has its own BMS, in a parallel setup...what is the best way to handle this for proper battery stability? Only one BMS doing active monitoring? All of them? None of them?
2. Best way to charge, should I charge each pack independently and and then reconnect them after validating the voltages are almost identical so there isn't a surge of energy transfer? Or can I charge in parallel essentially replacing the inverter for a SCC and all the safety bits that go with that.
3. Other safety measures. What am I missing? What else would you recommend I add? Should I add a disconnect switch for each POS before the busbar as well?
Each 13S pack has the following properties:
- Capacity: 37Ah
- Energy: 1.78kWh
All this info will come in handy because I have 4 Renogy brand new batteries I bought, 24V/25ah each and they are going in parallel. They have their own internal BMS, which is nice and all and it says they balance themselves but I still plan to follow this similar type footprint. Is it allowed or safe to add a BMS to batteries like that have internal BMSs? Just be to be able to monitor each battery? I have a 500V shunt from them but I didn't know if there is a better way for me to be able to see how each battery is doing. I dont just want to throw some fuses on them and wire em up that scares me not being to "see" how each battery is doing. How is that normally handled??
Keep in mind this are "portable" packs, they do not stay connected to solar panels or SCCs, they are in boxes that have wheels so they can be placed in safe locations to power certain parts of the house. Mostly I've been building 16S LFP packs in steel enclosures right now, but these I'm kinda on my own in terms of design. I've read the battery documentation from Renogy it actually says the batteries can be paralleled up to 8 (I only have 4) and NO series connections allowed. Curious of what the community would design in that situation.
I appreciate any and all feed back on design and safety measures needed. These Audi batteries are the last of NMC batteries and the case I have to build is going to have to be ridiculous to protect myself in the worst case scenario. It's going to involve a lot of thick steel vent holes with proper handling of the venting, I'm going to add sensors from microcontrollers I program to give me warnings ahead of time for temp and VOCs, the BMS's will be set very conservatively for temp shutdown and other things. Thermal insulating fireglass will be used, CellblockEX pellets will be automatically setup in a manner to douse each pack in the event they heat up too much.
Everything will be thick steel, firebricks and the like. Fans will be used to remove exhaust as well as keep BMS's and other electrical parts cool and they will have a seperation barrier betwen the batteries and the busbars/bms's ect..and with multiple layers of protection. Fire extinguishers designed for Lithium fires have been purchased along with "worst case" fire supression canisters you throw at the fire and it goes off almost like a tear gas can the police use to smother, cool, and coat the batteries to extinguish them.
Honestly I'm not looking forward to the box build its going to be a huge PITA, expensive, and heavy (though it'll be on wheels).
Batteries will be charged conservitively and same with dishcharge. They are capable (video is out there to prove it) they can do about 150A continous (minor sag) when they are fully charged dropping slowly down to about 100A at shutoff (3V) and remaining just slightly warm). Now I would NEVER pull that kinda amperage. Like said my loads are stupid small under 100W. Routine checks on the IR (with quality expensive tools) will be performed to ensure batteries are staying within spec and healthy. As always I appreciate in advance your support, opinions and advice. This about safety and best to set that up for a worst case scenario. I don't know if I mentioned but the battery packs will be seperated by thick steel, so all three are not together so to speak. The hope there is, if one decides to become a bomb it doesn't take out the others with it. If all goes correctly it may start to vent, the battery will be doused automatically with CellBlockEX (designed to smother and put out NMC fires) and hopefully that stops it, if not the thick steel exhaust and other measures I discussed will serve as containment. I hope. I know someone is going to say just put them far away from your house as possible. Not possible. This is FL where its hot as hell pushing high 90's today and I have no where to put them in my yard I rent. If I did put em outside now I have to worry about adding weather (heavy rain) protection and it spirals. I understand the dangers, I've seen it, but also if done conservitive and safely they can be quite reliable and safe. I've used NMC for other things many times they are great. But yes they are little bombs, in this case 3 medium bombs if combined, one giant bomb. Hence looking for the best way to protect my self from a worst case (internal short/thermal runaway) situation.
Cheers,
Cyberfed
