About charging batteries in electric cars...

"BaconSandwich is tasty." (baconsandwich)
05/04/2015 at 18:11 • Filed to: None

I recently read a rather interesting article about Lithium Iron Phosphate batteries. Essentially, the guy bought some and had issues with them after a reasonably short period of time. It turns out what was happening is they weren’t being charged properly. His solution was to make a sort of balancer that would more or less allow each cell to be individually bypassed during charging.

!!!error: Indecipherable SUB-paragraph formatting!!!

This got me thinking: how do existing systems work in electric cars? Is each cell charged individually, or are they generally charged in groups? When doing something like Tesla’s supercharger, does the charger quickly switch between cells that it is charging to prevent each individual cell from overheating? How about during regenerative braking?

I really do wish I’d learned more about electronics when younger.

DISCUSSION (9)

E. Julius > BaconSandwich is tasty.
05/04/2015 at 18:29

I totally agree. I spent/spend a lot of time teaching myself mechanical principles. I started with the real basic stuff when I was a kid (“these are the four strokes of four stroke engine”), and I’m at the point now where I’m learning from the same textbooks my undergraduate classmates are using in engineering classes. The more time passes though, the more I feel like I need to dedicate time towards electronics and electric motors. I could tell you the basics of how electric motors and batteries work, but with nowhere near the nuance I can describe internal combustion engines. I know this knowledge is only going to become more and more important in the future.

Sam > E. Julius
05/04/2015 at 18:43

Knowing the inner workings of electric cars is going to be like knowing how IC engines worked at the turn of the century. People who know a lot will make a ton of money.

E. Julius > Sam
05/04/2015 at 18:53

Fortunately the part of the car I work on is important whether it’s electric or ICE! ; )

Sam > E. Julius
05/04/2015 at 18:58

The ECU?

E. Julius > Sam
05/04/2015 at 19:12

Nope, the stuff that keeps you from turning into meat paste if you get in a crash!

cnessel27 > BaconSandwich is tasty.
05/04/2015 at 19:19

I’m only familiar with R/c vehicle lipo’s and Ford hybrid/electric systems (although only in theory, I am mainly ford diesel tech never get to touch hybrids).

As for Rc lipo’s if there multi cell packs some (maybe most) battery’s come with balancer leads and most if not all lipo compatible chargers come with a balancer now-a days.

With Fords they have a HVBM (High Voltage Battery Module) and BCM(Battery Control Module). They work in tandem to control the discharge, charging (both plug in regen), and working with the PCM. I’m 99% on those module names an can double check on that tomorrow.

BaconSandwich is tasty. > E. Julius
05/05/2015 at 00:02

That's still a pretty awesome field to be in, I imagine. That, combined with material science, I think we still have plenty of room for improvement.

BaconSandwich is tasty. > cnessel27
05/05/2015 at 00:03

That's awesome. I'll have to do more reading on the topic as well.

BloodlessWeevil > BaconSandwich is tasty.
05/05/2015 at 07:09

You must have a balancer built into the battery pack (these are typically incorporated into the batter management system, and is actually one of the main purposes of those systems.) The cells must be balanced on both charging and discharging. The reason for this stems from slight differences in impedance between cells (or wiring to them) which causes them to charge and discharge unevenly.

If a cell is over charged or over discharged it could explode or catch fire or something bad (I skimmed over that part of the manual.) Anyhow, the take away is you must stop charging when the highest charged cell reaches capacity, no matter what level of charge the other cells are at. Similarly, you must stop discharging when the lowest cell reaches the safety threshold.