Converting large RV to Solar and Lithium, assistance needed

[ElectricLove]

New member here; joined after seeing this thread because I also have Ohmmu batteries. Mine are not in my RV (yet) but are in a big rack on my wall in the garage which is where my solar charge controllers dump all of my photon-derived electrons all day! We have an "off-grid" system on our house, even though we live in the city and have no lack of infrastructure here. Anyways, we use a 30kWh Ohmmu battery bank and so far have been very happy with the performance.

Saw a couple strange comments though, I'm not understanding:

PSA: thermal runaway

Thermal runaway? LiFePO4 chemistry is actually known to be one of the most stable around from everything I've read

So, chemistry is the same, Lithium Iron Phosphate, but the ohmmu are only 4 cell. If there is a chemistry difference I am missing, please educate me instead of just saying they are different.

They are different than what? Every 12V Lithium Iron Phosphate consists of 4 cells, just like every Lead Acid 12V consists of 6 cells; An LFP battery cell has a nominal voltage of 3.2V, a Lead Acid battery cell has a nominal voltage of 2.0V; they are internally put in series to get whatever voltage is needed. The same way we take 12V batteries and put them in series to make 24, 36, etc...

I looked up the Ohmmu and they are indeed LiFePO4


Interesting. I did not know it before now but apparently tesla's do have a 'house battery' that runs the 12 volt electronics in the car.

https://forums.tesla.com/forum/forums/do-ev-have-smaller-12v-battery

"Learn something new every day" Well, that's done. I can go back to bed now!

Interestingly enough there has been some discussion on this in the "Tesla world" and EV world in general; the first 100 Tesla Roadsters actually were built with NO 12V battery, they figured it was a good idea to just use the massive lithium battery as the source for all 12V systems as well (as many would assume). However, they learned after a few very costly warranty repairs that the 12V battery acts like a "fuse" of sorts and is actually very beneficial to the overall safety of the vehicle. Reason being; what happens when someone drives their car down to "almost empty" and parks it at an airport for a few weeks while out of town? Well, that 12V system is online and running the entire time, computers are "checking in" with each other, looking for key-fobs, making data-calls back to the "mothership" to see if there are software updates and to provide status updates on the vehicle (so the Tesla app has access to this information when you are away and want to check-in)... So all of this is happening and just running the battery lower and lower, without a 12V there is no good way to stop this from totally draining the main battery pack. It is all deemed "necessary loads" to keep the car connected and ready to drive and even plugging the car in will require the 12V computers in the car to communicate with the charging station to initiate charging (that's right 12V dead? You can't charge the car)... So a few $30K bricked battery packs later and Tesla said "ok, ok we need 12V batteries in every vehicle"

 

[FilterGuy]

Now that you mention it, I remember the horror stories of Tesla batteries bricking. Now I know why you don't hear those stories any more.

 

[ElectricLove]

Now that you mention it, I remember the horror stories of Tesla batteries bricking. Now I know why you don't hear those stories any more.

Those were the "early days"... I bricked my share of EV before Tesla even existed so I forgave them (and drive their vehicles now and have a Cybertruck on reservation now!)