Bring batteries back to life

James Dillon revitalises a Gen 1 Prius battery

Published:  19 April, 2013

By James Dillon

When, several years ago, I embarked upon my journey of understanding hybrid technology, I had heard tales of many miles to the gallon, how 'different' these vehicles were to drive, stories of death, destruction and electrocution and what could and couldn't be done from a repair and maintenance viewpoint. I decided to go to the mouth of the horse and undertook hybrid training courses with the two main experts in the technology, Honda and Toyota. It was interesting to see the different ways in which each of these manufacturers implemented this technology. The courses themselves were top quality and there was so much that was new for me to learn that I found them very rewarding.

After completing the courses, I was eager to get to grips with a faulty vehicle. The next hybrid I got to work on was during a training session I was giving in Dubai at a Toyota dealership. The subject vehicle was a Hybrid Camry but unfortunately, it wasn't faulty (well, these Japanese cars don't really go wrong do they?) So, I had to simulate faults and fault finding procedures.

Having got to grips with the technology and being in the hybrid groove, my goal was then to own one. I scouted around attempting to buy a broken one from a well-known auction site. I was after either a Gen 1 Toyota Prius or a Honda Civic Hybrid. I looked for a while but even very old, worn out Japanese imports fetched strong money and were snapped up in double quick time. However, as the old saying goes 'God is good to those she knows'. Out of the blue I got a sniff of a broken Gen 1 Prius which had been traded in at the local Toyota dealership. I put a call in to the sales manager and the car was mine, bought unseen, for a little more than scrap value. The fault was the dreaded main battery problem. The car had the so-called 'triangle of death' warning lamp on as well as the tortoise symbol. The main battery was setting trouble codes and was 'dead'.        The supplementary 12V battery drained down very quickly and the motor wouldn't crank. I had just bought a 1.5 tonne 'bronze coloured' rolling paperweight.

A quick call to my friend Trevor Roper, who is both a model aircraft expert and an excellent diagnostic technician, proved extremely fruitful. The Nickel Metal Hydride battery in the Prius is very old technology in the model aircraft world. Trev knew the technology well and suggested a strategy and some tools which, although not recommended by the motor manufacturer, should be able to recover the battery pack. For less than £100, I had been able to buy a charger capable of seeing to the individual cells which made up the Prius battery pack. Trev called into my workshop and together (me making cups of tea), we analysed the battery cells and formulated a charging plan (how much voltage and at what milliamp in-flow. By treating the battery as individual cells, we were able to cycle them and recharge them.

The hybrid battery pack can become imbalanced when cells have a differing voltage, despite them being connected together. The battery ECU isn't happy under these circumstances and can, as it did in this case, shut the system down to prevent further problems.  Figure 1 shows the Prius battery pack sitting on the trolley being recharged by two model aircraft battery chargers. This is not recommended procedure, it was simply an experiment, but it was an experiment which worked. DO NOT TRY THIS AT HOME!

It took around 36 hours to recycle and recharge the 38 modules to a healthy voltage level. After refitting the battery pack, the little Prius roared, well OK, sort of hummed - as they do - into life. This recovery procedure was several thousand miles ago. I have been using the car for about a year now without a hint of problem. It's not a mans' man's car, nor will it win any prizes for sporting endeavour - my 14-year old son thinks it is just sooooo uncool. However, despite it being unfashionable, it really is a funky, economical, interesting little motor car.

Well, French vehicle manufacturer Peugeot has thrown this rule book out and is said to be developing an entirely new system, based on a three-cylinder petrol engine coupled to an air compressor. The system is known as 'Hybrid Air' and it combines two energies to achieve the highest efficiency in various situations. So, the compressed air will assist or even take the place of the petrol engine during the phases which consume the most energy: namely acceleration and moving off.

This technology uses certain components new to the motor industry but, according to the VM, is widely tested in other sectors such as aeronautics. The Hybrid Air system consists of:

? An energy tank, containing pressurised air, installed under the body in the central tunnel

? A low pressure tank at the rear suspension crossmember, acting as an expansion bottle

? A  hydraulic  unit  consisting  of  a  motor   and  a  pump,  installed  under  the  bonnet  on  the transmission

The latter consists of an EGC (Electronic Gearbox Control) epicyclic drivetrain to manage the distribution between the two motors. It replaces the mechanical gearbox and also offers automated gear changes.

The petrol engine is also very efficient and benefits from the new 'Diamond Carbon' internal coating, as well as split-cooling for faster warm-ups. It all sounds jolly good but we just wonder if the public are ready for cars that we think are going to make a noise like an angry swarm of fridge freezers...

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