Electric cars holding their charge

[danbrennan]

I wonder if the lithium wake up time has to do with the change in internal resistance as a function of temperature. The graph below shows Li internal resistance going up much more sharply than lead acid at cold extremes(well, at least Li-Ion, not some of the other Li chemistries). But I don't think that necessarily means the battery capacity is reduced, it's just that it can't put out as much current for a give voltage charge. Then with an Li battery, hitting the starter and then waiting a few seconds warms up the Li battery, lowering its internal resistance, and allowing to supply more starter current?

https://www.researchgate.net/figure/Dependence-of-internal-resistance-versus-temperature-for-lithium-based-batteries-LiFePO_fig15_316171277

 

[doug m]

i guess i was just wondering what percentage of a vehicle charge is disappearing into thin air and if that percentage is worse when not in use??

 

[bfmgoalie]

Was your car battery in your car lithium? or lead acid? Unlike traditional car batteries, lithium fairs a bit better in cold weather. Obviously we'll still have issues the colder you go, but that goes for ice cars too. At the end of the day both cars would have similar solutions for cold weather, you hook it up to a heater to help start your car in the morning.

As I stated, not a scientist, meaning don't have a clue. Ask me questions about metallurgical engineering, I'm your man! Now here's another example. I was an operation manager for Montgomery Ward Distribution. One of my departments I was responsible for was shipping. All trucks had to leave the DC by midnight to arrive in the stores by 6:00AM.

I arrived at the facility at 7:00AM and all the trucks were still there. The temp dropped between 0F to -10F and none of the trucks would start. Wouldn't turn over.

Is there a difference between a battery you run in a tractor vs a car?

 

[SPG]

As I stated, not a scientist, meaning don't have a clue. Ask me questions about metallurgical engineering, I'm your man! Now here's another example. I was an operation manager for Montgomery Ward Distribution. One of my departments I was responsible for was shipping. All trucks had to leave the DC by midnight to arrive in the stores by 6:00AM.

I arrived at the facility at 7:00AM and all the trucks were still there. The temp dropped between 0F to -10F and none of the trucks would start. Wouldn't turn over.

Is there a difference between a battery you run in a tractor vs a car?

Tractor batteries are just lead acid and AMG, you can put a lithium battery in a tractor. Difference is, they also need amp-hours so they're rated differently than cars.
But thats just a rating, they should function the same as a car battery.

 

[Gary S]

My concern isn't about the battery holding charge when not used. My concern is how much power you can expect from a lithium battery in really cold weather. Will an electric car be even able to move when it gets cold? This chart suggests that you might see a very low capacity and that translates into short distance the car can drive. You might see the car range to drop from 200 miles to 20 miles or less.

 

[Todd80Z28]

if a electric car is charged to 100 percent and then not used for a week or 2 will it retain its full charge? or how much is lost?

It's a bit of a loaded question, as it depends on the particular model and the "vampire drain" of some of the car's electronics. My BMW i3 has virtually no loads when off, it's a simple car. A Tesla phones home a lot, keeps some of the electronics awake, etc, so it uses a bit more- perhaps a few percent per week. If you use the Sentry Mode (active motion sensing and cameras on), it will burn through a few percent per day. Of course, Teslas have big batteries in general, so less worry there.
Last summer we went to FL for ~11 days, I left mine in the garage just above 40% charge. When we returned, it had the exact same charge. Temps were mostly 80s IIRC, so my garage was probably 75-90 over that time period?

Also, it's generally not good to keep a lithium-ion battery at 100% when sitting. The extreme ends of charging and storage can be bad for the long-term health of the battery. So it's preferred to keep it in the 20%-80% range unless you need that extra capacity for a trip. If it's being used immediately, not as big a deal. Different chemistries (e.g. Lithium Iron Phosphate) don't have this issue as much, but they all have various tradeoffs.

I defer to your opinion sir. My experience is based on a snowmobile lithium battery. Great idea, super light weight, but for whatever reason, does not like cold weather. I discovered it needs about 30 seconds with a mild load on it to "warm up" before it will budge the starter. A phenomenon that today's EV tech probably looks after electronically.

Almost all the motorsports batteries that are Lithium are Lithium Iron Phosphate chemistry, which REALLY doesn't like temperatures below freezing. So yeah, that seems pretty normal. A light load does seem to wake them up. Charging them at these cold temps REALLY REALLY shortens the life, though. EVs handle this by heating the battery before charging, but with a $100 starter battery, they just lead a harder life. Honestly, if you are out there in -10C or lower, you're probably better off with a lead-acid, lifetime wise.

 

[Rosster]

Was your car battery in your car lithium? or lead acid? Unlike traditional car batteries, lithium fairs a bit better in cold weather. Obviously we'll still have issues the colder you go, but that goes for ice cars too. At the end of the day both cars would have similar solutions for cold weather, you hook it up to a heater to help start your car in the morning.

The batteries heat up when discharging. My dirtbike was slow for a few seconds when we rode on real cold mornings and sped up everytime you hit the starter,

 

[gin man]

Both of our plug-in hybrids have what's called a high voltage coolant heater. It's job is primarily to warm the battery so that it operates efficiently but it also provides cabin heat when needed.