Future battery replacement

[RegGuheert]

So what can wear out besides batteries? Shocks, struts, brakes and tires – that’s about it.

The drive electronics for the 80 kW motor, that's what! In particular, the electrolytic capacitors (if any!) used in this unit will be very hard pressed to last much more than 10 years or so, particularly in the hotter climates.

In the solar PV arena, the makers of grid-tied inverters in the 5-kW range are struggling to achieve MTBFs longer than about 10 years, even in products that have been in production for years. In fact, some of the heads of these companies have stated as much. Note that that industry HAS been successful achieving MTBFs of 100s of years with life expectancies on the order of 30 years in a VERY harsh rooftop environment for microinverters in the 200-W range by greatly derating the capacitors and using extremely advanced manufacturing and quality control approaches. While that level of manufacturing and quality comtrol certainly exists within the automotive industry, the simple fact is that IF there are large electrolytic capacitors in the drive electronics, they may not have the option to derate these components sufficiently to achieve the MTBF and life expectancy of 20 years that would be necessary to allow the failure rates to remain low much beyond 10 years.

While it is encouraging to hear that the RAV4 EV is holding up well, please note that it was not sold broadly geographically, but rather was mainly restricted to CA, which has a rather mild climate. LEAFs are already being sold into some extremely harsh climates. An active cooling system certainly helps here, but storage at high temperatures can also be problematic.

I will say, however, that I absolutely hope that I am wrong here. If anyone has details on the power electronic design of the drive electronics in the LEAF along with some studies and testing related to life, can you please point me to it. TIA!

 

[TomT]

Let's see... Constant velocity joints, transfer case including differential, electric motor, inverter, various pumps, wheel bearings, suspensions bushings and tie rod ends, switch gear and electronics, led headlights, etc... There is still a lot in there to wear out or go wrong...

So what can wear out besides batteries? Shocks, struts, brakes and tires – that’s about it.

 

[siai]

You might be right on the money about capacitor failures. Both of my previous electrics had capacitor problems. In the S10-E (which shared the drive from the EV1) the motor inverter capacitors would fail. In the Rav4-EV, a common failure was the battery charger input capacitor. In both cases, the primary cause was a design issue that specified capacitors with a marginal ability to withstand the high voltages applied to them. In each case, private individuals came to the recsue by having replacements made and then sold them to owners of the vehicles. I replaced the drive capacitors in two of my S10-E's as insurance before they failed. I never had a failure in the Rav4, but it was common. You must remember that each of the vehicles I mentioned were 10 years old (or older) and none that I owned had actually failed. So fairly reliable. The S10's suffered from battery issues as they were the original Ovonic design--the original Nickle metal hydride battery. The Rav4-EV never gave me a single problem during the entire time I owned it. Almost 10 years old, no battery degragation, 100 mile range to turtle at highway speeds on a single charge. I don't think the LEAF that I own currently will match the battery life/range that I had in the Rav4.

 

[Herm]

Almost 10 years old, no battery degragation, 100 mile range to turtle at highway speeds on a single charge. I don't think the LEAF that I own currently will match the battery life/range that I had in the Rav4.

The capacitors have to be specced for automotive duty.. and that is harsh.

Do you have an estimate on how many cycles you put on those batteries?.. how many miles?. Nimh have a different failute profile than lithium.. mostly the internal resistance starts to go up and then the batteries start to waste more energy as heat. Does the Rav-4 use liquid cooling?

 

[copdoc]

You forgot the Johnson rod!

http://www.youtube.com/watch?v=Fx2GZ4AJtVM" onclick="window.open(this.href);return false;

Let's see... Constant velocity joints, transfer case including differential, electric motor, inverter, various pumps, wheel bearings, suspensions bushings and tie rod ends, switch gear and electronics, led headlights, etc... There is still a lot in there to wear out or go wrong...

So what can wear out besides batteries? Shocks, struts, brakes and tires – that’s about it.