Cost per kWh

[Stinsy]

One thing that is not really considered when repurposing car batteries as house batteries if the fire risk of different types of lithium batteries in cars.

Most car batteries are lithium-ion as it has a high energy density (kWh per Kg). Most home batteries are lithium iron phosphate (LiFePO4) which has a much lower fire risk, as it does not suffer from thermal runaway.

I appreciate that the term lithium battery includes many battery chemistries and it is not always obvious which is used.

In a car the battery is being charged/discharged at 100kW or more, in a domestic setting the charge/discharge rate is a 10th of that at the very most. So the already-negligible risk of fire becomes even lower.

[John_S]

One thing that is not really considered when repurposing car batteries as house batteries is the fire risk of different types of lithium batteries in cars.

Most car batteries are lithium-ion as it has a high energy density (kWh per Kg). Most home batteries are lithium iron phosphate (LiFePO4) which has a much lower fire risk, as it does not suffer from thermal runaway.

I appreciate that the term lithium battery includes many battery chemistries and it is not always obvious which is used.

In a car the battery is being charged/discharged at 100kW or more, in a domestic setting the charge/discharge rate is a 10th of that at the very most. So the already-negligible risk of fire becomes even lower.

I would not be so quick to dismiss concerns about fire risk.

Firstly, are there any statistics on what proportion of EV battery fires are whilst charging, whilst driving whilst parked or as a result of a RTC?

Secondly, insurers of EVs are becoming increasingly concerned of where EVs are parked at night.

I am not sure that I agree with your comment on discharge rates. You fail to take into account that domestic batteries are around 10 - 20% of the size of car batteries. A typical 75-80kWh car battery should give a real life range of 250 miles which is over 3 hrs at 70mph which I understand to be a average discharge rate of 0.3C. Without digging too deep, a quick look on the internet supports LiFePo4 batteries having similar discharge rates than lithium-ion of 1C.

I am not saying that Lithium car batteries cannot have a second life as house batteries. I am just saying that the difference in fire risk needs to be assessed and taken into account.

[Joeboy]

I'd remove the pack and break it down into modules. They are 3P4S modules so you can easily arrange them into a 54V 15S arrangement.

You can sell the rest of the car sans-battery for decent money to a breaker!

Would that not stop in tracks the advantage of the IO/GO tariff?

Sure. But I was thinking purely about the cheap battery...

After I posted I was thinking about how much you'd have to strip out of the EV as a minimum to make it a home pack in a crate that could still get an individual onto IO.

[Stinsy]

Would that not stop in tracks the advantage of the IO/GO tariff?

Sure. But I was thinking purely about the cheap battery...

After I posted I was thinking about how much you'd have to strip out of the EV as a minimum to make it a home pack in a crate that could still get an individual onto IO.

Hard to know. Maybe just the onbord charger? Depends how integrated it all is. Maybe the onboard charger would refuse to do anything if it wasn't connected to the main computer...