Lithium batteries

[ykachuro]

Colin, from what I gather, the Dreamliner battery used/uses a different chemistry than lithium iron phosphate batteries do. I am told, lithium iron phosphate batteries do not produce enough heat when shorted to burn, but the smoke they generate can be deadly nevertheless.

Also, when you suggest spending money on battery charging circuitry, could you please allude to what circuitry do you have in mind? My understanding that the Shorai and EarthX batteries are designed to be plug and play in powersport applications without any need to make changes to the original charging circuitry. The only thing that needs double checking in our application is making sure there is a robust crowbar overvoltage protection (very inexpensive and easy to implement). Thanks!

[colin]

I was involved in the transition from NiCd and NIMH batteries to Li Ion batteries in the power tool industry. I've seen all the fires and I understand the phosphate (ABC) vs cobalt properties in Li Ion . I also followed the Dreamliner issues with great interest. I have utmost respect for the Boeing engineers, unlike Elon Musk. While the specs for Li Ion would lead you to use the chemistry like the Boeing guys did in the slim chance there was a fire due to a shorted cell the result would be catastrophic, especially with the battery in the cockpit . You cannot put these fires out . They make their own oxygen. That is why the Boeing guys finally put the battery in a containment box in the still unexplained result of a fire. The fire will be contained and not considered a flight hazard in the box. The issue with charging these batteries is with the charge regime and maximum charge voltage of 4.2 volts per cell, not the size of the alternator. If you spend any money spend it on the battery charger circuitry .

I elected to use the Odyssey 680 on the cold side of the firewall. If you want more cold cranking amps Odyssey have a SBS J-16 in the same form factor with 300 CCA. For cold starts on my RV7 I put snowmobile handlebar grip warmers on either side of the battery and plug it in when I'm preheating with the Tannis heater.

[jamesmil]

IMG_Jan22019at84219PM.jpg

I mounted my battery inside on the firewall and used the odyssey 680, if you are going to use an 0-320 you will the need nose weight. I fabricated aluminum angle with # 4 nut plates to engine side of the firewall using rivets and Hysol 9460. I also am using the B/C 8 amp alternator, works great. Sorry I tried to upload a pic but it says the file is to big. If you would like a pic PM me and I will send it.


Finally got the picture down loaded, this shows the battery box install,the master solenoid and start solenoid are above.
If you plan to do some heavy acro mount the start solenoid upside down to make sure that it doesn’t pull in and engage the starter under hard positive g’s .

[ykachuro]

Can’t share my personal experience yet as I am only considering what battery to use, just like you. But here is my thinking.

Adventages of lithium (more specifically, lithium iron phosphate) batteries over lead acid
— light weight (5+ times lighter) for the same cranking power and rrserve capacity — this is the main adventage to me
— can be deeply discharged with no ill effect (except can be killed if run down completely (unless it has a built in over discharge protection)
— can accept greater charging current
— may last longer (thousands vs hundreds of charge/discharge cycles)
— doesn’t vent hydrogen when being charged/overcharged — no risk of hydrogen/oxygen mixture exploding (this is purely theoretical as I’ve never heard of this actually happening with lead acid batteries)

Disadventages
— risk of catastrofic failure in case high charging voltage is applied or in case it is externally overheated. The catastrofic failure may lead to a thermal runaway and resulting noxious smoke. With lithium iron phosphate batteries the thermal runaway does not result temperatures leading to fires, however, smoke can incapacitate and kill.
— higher cost (2-5 times greater than a lead acid battery)

Considering that the risk of the catastrophic failure can be mitigated/eliminated, the adventages of a lithium battery (the weigh saving) are leading me to picking a lithium battery over a lead acid battery.

How I plan to mitigate/eliminate the risk of a thermal runaway:
1. crowbar overvoltage protection. This seems to be 100% reliable. It is a must in any electrical system and I do not consider it to be an added expense.
2. i plan to use a small alternator, which is very unlikely to drive the voltage high enough to overwhelm the lithium battery quickly in case of the voltage regulator failure. This is just incidental and not needed if the crowbar overvoltage protection is properly implemented.
3. I plan to place the battery on the cockpit side to limit its exposure to high tempratures in the engine compartment — for longetivity and for limiting the risk of it being expose to tempratures high enough to cause a thermal runaway (probably only relevant in case of engine compartment fire). The more conventional thinking is to place the battery in the engine compartment so that it is vented outside in case it smokes.

Now, lithium batteries (EarthX) with management systems (with BMS) vs no BMS (Shorai). I see no reason to pay x2+ for an EarthX battery over Shorai. EarthX “overvoltage protection” is not meant to protect against real overvoltage events (where voltage reaches 60v+ — so what’s the point, other than marketing? Built in cell balancing — this needs to be done only very occasionally and can be done with a lithium battery charger/maintainer. Overdischarge protection — might be a blessing or a curse — I’d rather get the very last drop of juice out of a battery when I really need it (even if it means I will kill it) instead of the battery saving itself while leaving me high and dry.

Please take this for what it is worth...

[fwellman@att.net]

Happy Holidays everyone!

I am considering using an EarthX lithium battery in my Panther, primarily because of the weight savings it provides. However, I am still not completely comfortable with the safety of lithium batteries. I am using a Lycoming 0-320 A2B with a conical mount, so there should be room on the engine side of the firewall to mount the battery. However, for servicing it would probably be better to mount it on the inside of the firewall under the boot. I am wondering if others have used the EarthX, and what your experiences have been.