# EV Safety



## researcherAU (Jun 24, 2008)

I have just come back in from a very unpleasant experience, driving a loaned EV conversion which is dead correct by all current standards I got very out of shape on a wet road corner and have probably totaled the car.
If I had tyres with good tread traction and a pressure that would allow a degree of flex I could have driven out of the situation, but on this car the tyres were narrow,pumped up to the max,and low on tread just as the pundits proclaim is needed for an EV. The start was a rapid deacceleration due to regen braking but the problem got out of hand when I tried to accelerate out and had NO TRACTION and the rear swung out and left the road. I feel that a balance of traction vs rolling resistance needs to be addressed with the grown in ability of EVs to obtain highway speeds (and better) and more being used as daily transport this safety issue could raise itself more in the minds of designers and converters, my own car now is getting a revamped suspension to allow standard road tyres to be fitted and a altered suspension so remove the dive I noted in the other car, I allow that the car I totaled was a front wheel drive and mine will be a rear wheel drive I recieved a big enough fright to put road safety a very high priority when I get my own unit on the road


----------



## Astronomer (Aug 7, 2008)

I'm sorry to hear about your situation, and I'm glad you're all right.

I'm all for keeping cars on the road as long as possible (I've been driving the same car every day for 20 years, so I walk the walk, too ), but I recognize that there are safety concerns with that. The car I plan to convert doesn't have air bags and has questionable side-impact durability. (Air bags were "experimental" and "Luxury" items, and side impact tests weren't performed when this car was built.) And increasing the car's weight with lead-acid batteries doesn't help either.

My plan is not to exceed the car's GVWR, and to continue to use standard tires at the recommended pressure. Depending on how much lead I add to the car, I may beef up its suspension and brakes. Being able to stop a car is more important than being able to make it go.

Thanks for raising the topic and starting this thread. EV conversions are great, but if they end up being the death of us (Pyramid car, anyone?), then what's the point?


----------



## researcherAU (Jun 24, 2008)

I thought I should do a follow up on my emotive post of yesterday,I spoke to the owner of the car who was also the passenger at the time of the incident when she was released from hospital this morning and we agreed to do a debrief this afternoon both at the incident site and at her home with a friend of mine who like me is an ex rally driver as moderator. Both the owner and I have a background of engineering design and so are very interested in examining the causes of the incident so when we do our next vehicles we do not redo the same errors(if any). The plan is to do the debrief and the over the next days examine the car from all aspects and prepare an incident report for our own use. If there is interest enough and the moderator(s) think it desirable we will make a public readable copy and either put it on the forum or make it available on request.


----------



## mattW (Sep 14, 2007)

I'm sorry to hear about your accident, its sucks that so much hard work and cash is gone but I'm glad to hear everyone is ok.

High tire pressures and skinny tires should actually increase wet weather handling not decrease it since they are more likely to cut through the water to contact the surface. I would say the lack of tread would be the major culprit, older tires generally have lower RR that new ones but you should never go below the minimum recommended thread depth. There is a good (long) thread about high inflation tires here, skip ahead to page 5 for actually studies and statistics.


----------



## Ioku (Sep 27, 2007)

This one of things I have never liked about the way most people do there ev conversions by going with super skinny over inflated tires with crappy tred and horrible grip just to get a few more miles range. I plan on building a performance rally capable ev and will be doing the opposite of recommended ev tires by going with the best grip I can get.


----------



## researcherAU (Jun 24, 2008)

Matt ( and others ) the report I spoke about in my blog is complete If you want a copy or the group wish to have a copy email me , there were many things that came out both from the design and performance areas Ian


----------



## Coley (Jul 26, 2007)

You said it was a front wheel drive. Seems unusal that the rear end came loose.

Did the front end come loose also, when you when to accellerate?, or did it come loose first from the regen?

Sorry to hear of the damage, but glad you both are OK.

I drive my front wheel drive in the snow, but don't have regen. So far it has not had a problem.


----------



## Qer (May 7, 2008)

Coley said:


> You said it was a front wheel drive. Seems unusal that the rear end came loose.


It can happen. I had a very nasty experience many years from now with a SAAB 900. They're (in)famous for going straight forward when loosing traction, yet this time it wagged it's tail furiously. I was accelerating hard on a uphill road that was slightly curved when the rear end suddenly lost all control and skidded away. It took me some wild steering to get control over the car again and after 3 or 4 pendlings I got the car to go straight again.

What really baffled me was that it happened when I was accelerating uphill with a front wheel drive. Sure, it rained at the time, but it wasn't really heavy rain. Very odd experience.


----------



## researcherAU (Jun 24, 2008)

Coley and Qer when we did a complete check over on the incident we found that the tyres although part of the problem were not the major cause it would appear that the villain was the location of the battery packs , if you want more on this email me and I will send a full copy of the report


----------



## engineer_Bill (Jun 24, 2008)

researcherAU said:


> Coley and Qer when we did a complete check over on the incident we found that the tyres although part of the problem were not the major cause it would appear that the villain was the location of the battery packs , if you want more on this email me and I will send a full copy of the report


A hint on battery pack location would be greatly appreciated.


----------



## researcherAU (Jun 24, 2008)

Engineer Bill on the Honda there were 3 battery packs the most forward was ahead of the front axle mounted on the radiator mounts the second was behind the motors and mounted between the firewall and the axle with the third to the rear of the rear axle and this pack was the heaviest so the dumbell effect was well in play.


----------



## sailfish11 (Sep 15, 2007)

For a good set of new tires with good (low) RR and handling in wet conditions, consider Michelein X Radials. At about $100 apiece, they're expensive, but not terribly so. You can only get them at clubs (Sams, CostCo, etc.). Worth checking out.


----------



## dtbaker (Jan 5, 2008)

researcherAU said:


> Coley and Qer when we did a complete check over on the incident we found that the tyres although part of the problem were not the major cause it would appear that the villain was the location of the battery packs


have you measured the weight distribution front/back?

For 'best' performance most front-wheel drive cars attempt to balance 60/40. The other factor is that the further from center the weight is located, the faster things will get out of hand once you start a slide.... i.e. with the same staic weight distribution, having batteries out at the front and rear bumpers would behave differently that having batteries more to the center of the car once a spin starts....

D


----------



## mrg (Dec 8, 2008)

Leaving tread patterns out for the moment, narrow tires may reduce the chances of hydroplaning, but once a slide starts the contact patch is minimal and harder to regain control of. Front wheel drives will pitch the rear end out if the drive wheels approach lock up and you have enough weight in the back. Additionally, if you add a lot of static weight (lead batteries) and do not adjust your brake and suspension proportioning valves you are asking for trouble at some point in an emergency avoidance procedure. Anti-dive shocks, springs and tire sidewall ratings, air pressure, front to rear brake proportioning.... I could go on and on.

You can't just look at how to change your propulsion system without looking at how it relates to all other systems on the vehicle.

Glad you and your friend are OK and that you are smart enough to do an incident/accident analysis to develop a corrective action plan for future use.


----------

