LiFePO4 Battery Build

@ttmott - Boeing ended up putting the 787's LI batteries in SS boxes vented overboard for fire protection. Would it make sense to make your battery boxes from SS instead of AL?
 
carterchapman said:
@ttmott - Boeing ended up putting the 787's LI batteries in SS boxes vented overboard for fire protection. Would it make sense to make your battery boxes from SS instead of AL?
Click to expand...
I don't think so Carter
Boeing uses Lithium-Ion batteries specifically Lithium Cobalt Oxide which contains a flammable electrolyte. The energy density is very large so in a thermal runaway situation fire is usually the case. Hense the SST enclosures. Wasn't it a JAL 787 flight that had a battery fire on the ground then there was one other that got them into the SST enclosures?
The batteries we are using are Lithium Iron Phosphate which the chemistry is not flammable. The energy density is much less in these batteries compared to LiCoO2 (aircraft, Laptops, cell phones), LiMn2O4 (power tools), LiMnCoO2 (automobiles), LiNiCoO2 (automobiles). Aircraft, personal electronics, automobiles, and power tools all demand high energy density to keep weight and size down yet provide a high amperage charge and discharge capability sacrificing the safety inherent in LiFePo4 batteries consequently they are purpose applications.
In our case we are not as concerned with weight and size but rather safety. There are still safety concerns with the LiFePo4 batteries but these are more to destroying the expensive batteries or having a battery shutdown precisely where you don't want one in a boat. I think the coming ABYC regulations will be primarily for the manufacturers but I worry about the insurance fallout for owners that do their own thing. Many owners are building battery systems and many lack some critical skills to ensure what is being built is safe and achieves the desired operation. @dtfeld has done a lot of research to ensure his application will safely and reliably operate for years to come. A boat neighbor of mine down the dock has installed a couple of used Tesla automobile battery banks and has cobbled together a BMS; I don't know his exact configuration but I'm glad my boat is six or seven slips away.
I have this bookmarked -
https://batteryuniversity.com/article/bu-205-types-of-lithium-ion
 
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Tt do you have access to the abyc regulations?


If I understand the Tesla batteries do not utilize a BMS, each individual cell is fused and protects itself. If he is using a BMS on top of that protection scheme, he might have a fairly safe setup.
 
Also have you guys considered going all in with electric drives a battery bank and a diesel generator?
 
jmauld said:
Tt do you have access to the abyc regulations?


If I understand the Tesla batteries do not utilize a BMS, each individual cell is fused and protects itself. If he is using a BMS on top of that protection scheme, he might have a fairly safe setup.
Click to expand...
They have quite an exotic BMS for the cars which also controls the coolant flows and heat for the batteries. A fusible link only takes care of a shorted cell.
 
ttmott said:
I don't think so Carter
Boeing uses Lithium-Ion batteries specifically Lithium Cobalt Oxide which contains a flammable electrolyte. The energy density is very large so in a thermal runaway situation fire is usually the case. Hense the SST enclosures. Wasn't it a JAL 787 flight that had a battery fire on the ground then there was one other that got them into the SST enclosures?
The batteries we are using are Lithium Iron Phosphate which the chemistry is not flammable. The energy density is much less in these batteries compared to LiCoO2 (aircraft, Laptops, cell phones), LiMn2O4 (power tools), LiMnCoO2 (automobiles), LiNiCoO2 (automobiles). Aircraft, personal electronics, automobiles, and power tools all demand high energy density to keep weight and size down yet provide a high amperage charge and discharge capability sacrificing the safety inherent in LiFePo4 batteries consequently they are purpose applications.
In our case we are not as concerned with weight and size but rather safety. There are still safety concerns with the LiFePo4 batteries but these are more to destroying the expensive batteries or having a battery shutdown precisely where you don't want one in a boat. I think the coming ABYC regulations will be primarily for the manufacturers but I worry about the insurance fallout for owners that do their own thing. Many owners are building battery systems and many lack some critical skills to ensure what is being built is safe and achieves the desired operation. @dtfeld has done a lot of research to ensure his application will safely and reliably operate for years to come. A boat neighbor of mine down the dock has installed a couple of used Tesla automobile battery banks and has cobbled together a BMS; I don't know his exact configuration but I'm glad my boat is six or seven slips away.
I have this bookmarked -
https://batteryuniversity.com/article/bu-205-types-of-lithium-ion
Click to expand...
Thanks Tom,

As you can tell, EE was not my strong point in Engineering School!
 
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jmauld said:
Also have you guys considered going all in with electric drives a battery bank and a diesel generator?
Click to expand...
In a vehicle (especially a light truck) that makes a TON of sense for a variety of reasons. In a boat, not so much, because most of the operating in a boat is under high speed high load conditions. The losses you take in the double conversion (mechanical>>electrical then electrical>>mechanical) means you have to have a much larger generator (and diesel engine driving it) than if that powerplant directly drove the props. You could recover some of the efficiency if you went with submersible electric pods, like the big cruise ships do, but that might not be practical on smaller boats.
 
jmauld said:
Tt do you have access to the abyc regulations?


If I understand the Tesla batteries do not utilize a BMS, each individual cell is fused and protects itself. If he is using a BMS on top of that protection scheme, he might have a fairly safe setup.
Click to expand...
ABYC TE-13
It may have been adopted in December.... A clip of the relevant discussion -
2020-10-08_10-34-31-350x97.jpg
 
Well finally got a few minutes to assemble the cells. I cut some fiberglass insulation sheets to separate the cells, fixtured the cells together to a mild compression, and then used kapton tape stretched tight. Now to start laying out the internal wiring and BMS. These are not the best battery box in my opinion with this BMS, but I haven't found a lot of other options that fit the space and meet all my other criteria.

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Nice David! I finally have all 12 of my cells now, and just last week purchased the solar controller, inverter/charger, shunt and Cerebro (Yep, all Victron so far). The only thing I'm deciding on now is the BMS, I haven't yet figured out which one I want to go with.

I also haven't decided which configuration I want to go with, I need to do that so I can start building out the box for them. It's likely going to be one of these two, but I haven't figured out the bus bar thing yet.

3P4SConfig.png
 
@dtfeld have you considered making a fiberglass box for these, should be a fairly simple project.
 
jmauld said:
@dtfeld have you considered making a fiberglass box for these, should be a fairly simple project.
Click to expand...
No I have not. Interesting idea! How? Not in my usual skill set, but willing to attempt something new!
 
Easiest way is turn those batteries upside down and start laying layers of fiberglass over them. But I’d probably build a wood mold around the batteries and fiberglass it instead. The wood can remain inside the fiberglass for structure and reduce the amount of glassing needed. Fiberglass is really easy to work with. It’s the gelcoat and the finishing that takes the most time. You won’t necessarily need that for this project though..Maybe even intergrate those tensioning rods into the box, and leave one end so that you can add tension to the batteries. Unless you can tension them with shims.
 
I’ve made a few carbon fiber parts just by watching videos on YouTube and some guy from an adventure motorcycle forum. Can’t remember his name, but he illustrated really simple processes that didn’t require special tools like vacuum bagging. For carbon fiber you can also use epoxy instead of resin. It is safer and doesn’t cause as many issues if you breathe it. I’m not sure if epoxy is compatible with fiberglass but I would give it a shot for a project like this. I made a carbon fiber intake and some mounting brackets for my old mustang.
 
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