diy solar

diy solar

LifeP04 meltdown in a Sprinter van ?

Is the fireball larger, or does it last longer? From what I understand, the reaction in the battery can only go so fast so it was my understanding that the fireball would just last longer, not be more intense.
Both. I was just reading a paper on LTO safety today. Different states of charge create varying proportions of volatile materials because of the way they are altered by moving ions. The cells include vinyl esters, etc. to help control dendrite formation and other life-reducing reactions.

Basically, the chemistry changes a lot with state of charge, and all that stored energy ends up as a bigger, badder, longer lasting fireball.
 
Both. I was just reading a paper on LTO safety today. Different states of charge create varying proportions of volatile materials because of the way they are altered by moving ions. The cells include vinyl esters, etc. to help control dendrite formation and other life-reducing reactions.

Basically, the chemistry changes a lot with state of charge, and all that stored energy ends up as a bigger, badder, longer lasting fireball.
LTO is capable of a lot higher discharge rates than LiFePO4 under normal conditions so I would assume they would discharge at a higher rate in a dead short as well, no?
 
i for one am extremely pleased that OP caught the weird battery operation condition early and prevented undesirable further operation of the battery. admittedly, my battery systems are not equipped with realtime notification systems, so if they were to operate in a very undesirable way, my phone might not even buzz me!

kind regards
 
LTO is capable of a lot higher discharge rates than LiFePO4 under normal conditions so I would assume they would discharge at a higher rate in a dead short as well, no?
I have not looked at a comparison, but since LiFePO4 actually has a higher energy density I would expect similar results. Things change once the reaction is allowed to go exothermic, but the key point is that the amount of energy in the cell is actually higher at higher SOC. That energy will get expended somehow, and "discharge rate" is no longer a viable term in the usual sense.
 
interesting, thank you for sharing

this motivates me to uniquely label each cell, it only takes one moment for me to grab the wrong one when they all look the same
When I received my 16 cells, I 'batched' them based on the test results I received from vendor. I sorted them based on their stats (mostly capacity, but considered IR as well) and labeled each battery by group. I built them into 4 12v packs. I currently am running two packs in parallel, and recent check shows all cells in each pack within .002v of each other, and the two packs are within .005v of each other. :) Of course, I top balanced myself. In the future, I may convert them to 48v, but right now, I have a really nice 12v inverter that I don't want to replace, and my system needs to remain movable. It moves several times a year, and I need to be able to lift and carry each component, as I am usually not on a smooth surface. I cannot lift a 48v 280ah battery:/
 
No - I know I know- f’ng rookie why the f did you not….

Considering the outside of the packs are all negative, even if over duration they wore out…

Honestly I am going over the whole system and building out for robustness.

I have a Simarine Pico system to monitor.
I will be going with 4 batteries- 4 cells each with 150A BMS and balance board on each battery and a Simarine Shunt with TS.
The Simarine solution has an ability to trip a relay (call into factory) and can trigger an alarm if a Temp sensor goes high.

Also going to build compression plates with FR4 pads to hold the batteries in place, locked.
This is all going to be in a box under the van where I will build an ejection solution to eject the pack if it decides to behave badly
Since you havent mentioned this again I assume it was just a passing thought.
While initially that might seem smart and safe I can only imagine the pandoras box of liabilities that would introduce on several fronts.
The most obvious being integrity of electrical connections, how would you get something of such high current capacity to also cleanly disconnect in an.emergency by remote? Any scheme I can imagine would introduce significant resistance, worsened by corrosion in an undervehicle environment.
In designing for safety youd ensure a destiny of disaster.
Now lets talk about that ejection system, lol. Theres a little story they showed us in the Navy, about a day on the USS Forrestal involving stray voltage and a Zuni rocket pod... John McCain happened to be in the seat of the plane that got hit when it shot across the deck. 134 were killed, 161 injured.
 
Well I noticed the cells voltage was set high. 3.75 isn’t 3.65. I know you found the root cause, but please check your cells maximum voltage ratings and let us know.
 
So far looks like prismatic DIY packs have caused several accidents and are quite dangerous. I wonder if cylindrical cells build had such accident. I have DIY cylindrical packs power wall at home and plan to use same for van when I have need.
 
So far looks like prismatic DIY packs have caused several accidents and are quite dangerous. I wonder if cylindrical cells build had such accident. I have DIY cylindrical packs power wall at home and plan to use same for van when I have need.
Me thinks cylindrical vs prismatic doesn't matter as far as "dangerous" as much as the chemistry does. Are you saying you have DIY LiFePO4 packs now? Or are they the more common 18650 NMC/LCO/NCA cells? LiFePO4 cells don't have a real risk of thermal runaway. The others have a very high risk.
 
So far looks like prismatic DIY packs have caused several accidents and are quite dangerous. I wonder if cylindrical cells build had such accident. I have DIY cylindrical packs power wall at home and plan to use same for van when I have need.
Not necessarily. Prismatics are the cheapest and easiest to source. Which makes them the most commonly used by beginners who make dangerous errors. I would imagine that building these batteries would be so easy now that we have BMS (not long ago, I ran without BMS, as did many others). But then I see a picture of improperly sized conductors, rats nest of wires and bad crimp connections. Stuffed into a high vibration RV storage cabinet.

Whether you use lead acid, lifepo4, nca, NMC or lto, it is still a current source and can easily cause electrical fires.

Lifepo4 and LTO is by far the safest. Even compared to lead acid. But there are still risks. Especially with diy packs.
 
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Me thinks cylindrical vs prismatic doesn't matter as far as "dangerous" as much as the chemistry does. Are you saying you have DIY LiFePO4 packs now? Or are they the more common 18650 NMC/LCO/NCA cells? LiFePO4 cells don't have a real risk of thermal runaway. The others have a very high risk.
Mine is lifepo4 32650 prebuilt packs so it’s easier than raw prismatic cells pack.
I agree with Will, that without proper safety measures, a diy build can be dangerous no matter types of battery.
 
Those new LiFePo4 blades claim to be very, very safe, even in puncture test. I'd love to get some of those and slip them behind the wall panels in my van. ?
 
Those new LiFePo4 blades claim to be very, very safe, even in puncture test. I'd love to get some of those and slip them behind the wall panels in my van. ?
They can still cause a fire if improperly connected to your system. The battery is not the problem usually. It's the connections, size of conductor that supply it, size of OCPD etc.
 
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They can still cause a fire if improperly connected to your system. The battery is not the problem usually. It's the connections, size of conductor supply it, size of OCPD etc.
I agree. When it comes to the energy storage side of any system, this is not the time to be cheap.
 
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