Not quite a revolution yet. But…

This month John takes a look at why you can’t ignore EVs and where to start with diagnosis

By John Batten |

Published:  28 April, 2020

Picture this… It’s 2011, and I’m a much younger (and slimmer) version of myself. I’m delivering a training event in Chester so that the eager and excited delegates can learn about hybrid electric vehicles, pass their IMI HV qualifications and put their new-found skills into practice.
    
We were doing the usual rounds of quick introductions enquiring as to why each delegate had attended, and their desired outcomes from the training sessions. Many of the delegates, being technicians, had been sent by the business owner to ensure their team were safe when working around this technology, but one garage owner was there with a sole purpose. He wanted to get the jump on his competition and own the market for HV servicing and repairs in his area.
    
As you can imagine there were more than a few raised eyebrows in the room, mostly due to the fact that in 2011 only Toyota and Honda were producing these vehicles in any number, and the overall car parc was low. Nonetheless, one delegate had a vision. Everyone else thought we had some way to travel, and do you know what? As much as I loved the technology I could see their point of view. But, if the same statement were to be made today. Well, what do you think

So... are we there yet?!
Quite simply…Yes, and we’ve been there for some time. There’s a significant increase in awareness among the population, electric vehicle sales have seen a sharp increase, and this is only due to gain momentum with so many new vehicles this year being released by major manufacturers. Add to this the reduction of BIK tax to 0% and the positive effect this will have on electric company car sales means it doesn’t take a genius to work out that you’ll be seeing more of these in your workshops.
    
“I know it’s coming but…” Is not an uncommon retort to my enthusiastic musings on all things HV. I get it, but consider this. I’ve seen enough new technology introduced to our industry over the last thirty years to know the garages that grasp the nettle, understand the new elements of diagnosis and repair, and market their new-found skills, often have a healthy income stream for around a decade prior to their competition catching up. The BIG question is... Will you be going for first-to market-advantage, or playing catch up?
    
The good news is that while the technology may be a little different, the same rules of engagement apply. If you’ve been using our 15-step diagnostic process, and have proficient electrical knowledge then you’ll be well set to do battle with EVs and come out the other side triumphant. It is with this in mind that I thought you might like to take a look at some fundamental technology and HV diagnosis over my next couple of articles.

Let's get started – High voltage batteries
We’ll be taking a look at a Prius. The source of power is a NiMH battery that resides beneath the luggage compartment in the boot of the vehicle. The battery consists of 28 7.2 volt packs, each comprising 6 1.2v cells. The 28 packs are connected in series to give a total of 201.6v for the entire battery (fig.1).
    
The battery is air cooled by a multi-speed pulse width modulated fan drawing air from the cabin across the battery. The batteries temperature is subject to monitoring by three temperature sensors set equidistant (ish) across the batteries length. All pretty straightforward stuff, but do they go wrong? Well, from time to time – yes.

Where does diagnosis start
Like I said, “usual rules apply” and diagnosis starts with fault codes. A common battery code is P0A80-123. It is often accompanied by the HV fault light and the internal combustion engine running more than normal. As always, with fault codes in hand it’s off to take a look at serial data. Techstream – Toyota’s Tool – is readily available and not expensive, although you’ll also find many aftermarket tools offer the data required. But without knowing what good looks like, how can you tell what’s hot and what’s not?

Desk Diagnostics
At this juncture you grab a cuppa and hit the internet. Toyota’s online technical information is a breeze to use, and there’s really no excuse not to at only €3 an hour. A quick search for the fault code and you’ll be knee deep in information and know where to start with serial diagnosis.
    
Fig. 2 displays the serial data for the complete battery pack from our Prius. The eagle eyed among you will have spotted that while the battery is comprised of 28 7.2v packs. The battery management ECU is inspecting these in pairs hence the voltages around 16.X volts. So, is this one good or bad?
We’ve got some unfortunate news sir.

Toyota states that no more than 300mv difference is allowed between blocks (two packs) and as you can clearly see, the data shows an issue on block seven. But what could be causing this? Ultimately this could be down to a defective battery pack/s, alternatively it could be corroded BUS connections, as it’s not uncommon to see the BUS contacts a little green around the gills as shown in fig.3 adding an unwanted resistance between modules.

And the fault is…
In this instance, the fault is defective cells. It’s not uncommon for manufacturers to provide long warranties on their HV batteries. I’ve seen them as long as 15 years. In this instance though the battery is outside of the eight-year Toyota warranty with a new complete exchange pack available at around £1,000 + VAT from Toyota.

Until next time
There you go. A quick look at HV battery diagnosis. In our next instalment we’ll take guide you through some common HV components, their operation and key points for diagnosis. Just one thing to remember: While you’re no doubt eager to jump right in and get up to your elbows in HV diagnosis it’s worth remembering that these vehicles do offer up additional risks. They will kill you if you get it wrong, and work should only be attempted with the correct training and qualifications in place.
    
Need some help with your EV training and qualifications? As always, I’m here to answer your questions. If you’d like to find out how Auto iQ can help your garage with our training and consultation programs then feel free to call on 01604 328 500.






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