Was just talking to Robin G on another forum and he was talking about how 400V battery systems are more dangerous for DIYers. And of course they are - 400VDC is worse than 240VAC since it's both higher voltage and DC, which has worse outcomes when you get shocked by it.
But I've also noticed the battery landscape is changing. I used to build and maintain lead acid battery banks using GC2 batteries, and you had to use insulated tools AND clothing you didn't mind ruining. And safety glasses. And even so we had a battery box just plain disintegrate after exposure to enough of the airborne acid in the battery area. That kind of sucked.
My first LFP battery used CALB cells. And they were way better from an acid perspective but still had the same insulated-tool issue, and I would worry every time I had the cover off and there was a potential for some tool/wire/component to fall on the live terminals and cause a fireworks show. And since the BMS was external to them, it could not shut down the battery itself where the short would be made.
I did a small build for an RV using some off-the-shelf 12V LFP batteries and these were somewhat safer. These had internal BMSes so even a dropped wrench could only do so much damage before the BMS shut it down. Still used insulated tools for safety.
But then one year I did a server battery build for a Burning Man camp. And these had an external switch. And it completely changed how I handled the batteries, because now they could be "safed." I would never just give lead acid batteries to a non-electrical person and just give them a few instructions on how to hook them up, because the potential for disaster was too high. But with server batteries you can install the batteries, connect them, check the connections with a meter and only then power the system up - which makes the entire process far safer. And with the server batteries I could just give the camp instructions on how to set it up, and be fairly assured they'd be safe.
And that brings us to 400V batteries. The industry is gradually heading in this direction, mainly for copper cost/protection/lug cost reduction, but also because that's the most common EV battery voltage, and second life EV batteries are becoming more and more of a thing for cheap storage. The voltage is hazardous, of course - but with an AIO system there are now only two wires running from the battery to the inverter, and they can be installed long before power is ever turned on. And since all EV batteries not only have internal disconnects, they have to be cajoled into turning on at all, there's almost zero risk of accidentally getting zapped. Compared to that first bank of GC2's, I'd say a 400V battery with a disconnect is safer overall.
What do you guys think? Does the ability to only enable the output when you want outweight th eadditional risks you see at higher voltages?
But I've also noticed the battery landscape is changing. I used to build and maintain lead acid battery banks using GC2 batteries, and you had to use insulated tools AND clothing you didn't mind ruining. And safety glasses. And even so we had a battery box just plain disintegrate after exposure to enough of the airborne acid in the battery area. That kind of sucked.
My first LFP battery used CALB cells. And they were way better from an acid perspective but still had the same insulated-tool issue, and I would worry every time I had the cover off and there was a potential for some tool/wire/component to fall on the live terminals and cause a fireworks show. And since the BMS was external to them, it could not shut down the battery itself where the short would be made.
I did a small build for an RV using some off-the-shelf 12V LFP batteries and these were somewhat safer. These had internal BMSes so even a dropped wrench could only do so much damage before the BMS shut it down. Still used insulated tools for safety.
But then one year I did a server battery build for a Burning Man camp. And these had an external switch. And it completely changed how I handled the batteries, because now they could be "safed." I would never just give lead acid batteries to a non-electrical person and just give them a few instructions on how to hook them up, because the potential for disaster was too high. But with server batteries you can install the batteries, connect them, check the connections with a meter and only then power the system up - which makes the entire process far safer. And with the server batteries I could just give the camp instructions on how to set it up, and be fairly assured they'd be safe.
And that brings us to 400V batteries. The industry is gradually heading in this direction, mainly for copper cost/protection/lug cost reduction, but also because that's the most common EV battery voltage, and second life EV batteries are becoming more and more of a thing for cheap storage. The voltage is hazardous, of course - but with an AIO system there are now only two wires running from the battery to the inverter, and they can be installed long before power is ever turned on. And since all EV batteries not only have internal disconnects, they have to be cajoled into turning on at all, there's almost zero risk of accidentally getting zapped. Compared to that first bank of GC2's, I'd say a 400V battery with a disconnect is safer overall.
What do you guys think? Does the ability to only enable the output when you want outweight th eadditional risks you see at higher voltages?
