Should have added – did this guy not even have a multimeter to check the 12V battery voltage once disconnected?? Most batteries have floating balls now to colour-indicate whether the battery is charged too.

I was thinking some time back that EVs could do with a small hand-cranked generator for such occasions. You don’t need a fat lot of juice to activate the relay, just a small hand-cranking generator for a few minutes into a capacitor set would do the job of opening the HV relay, no problem.

From recollection (I could be wrong) the Fluence handbook simply says to jump start the car with another 12V battery source (i.e. just ‘jump start’ as usual).

All it needs do is to activate the HV relay, and then it’ll charge itself back up on the HV battery via the 12V charging inverter.

You can’t jump start another car with a ZE though. I can imagine that it will overload the 12V inverter if you try. Though I can’t see any particular reason you can’t connect up another 12V battery to a ZE with the ‘ignition’ on and leave it so the ZE HV battery charges up the other car battery. This way you are not pulling a sudden overload by cranking, but you will charge the other battery up, then disconnect the ZE once the other battery is charged enough and crank.

I see no reason that two ZE’s can’t jump start each other, though.

Of course, as mentioned could be nothing to do with the 12V battery. Absolutely ridiculous about the assist. So would it be better simply for me to call out the AA on our personal cover, if the people that turn up are just as un-initiated?

Hope you get this resolved quickly. It does sound like it must be a dead 12V battery. If you disconnected the battery from the car, surely it would be okay to charge it then? I’m just wondering in case something like this happens to me at some point. I have a battery charger that I could plug in to give the 12V some juice. I wonder why there is so much in the handbook about not doing that. To protect the 400V circuitry in case of some kind of problem with the 12V charging?

Odd, but I hope sorted in haste tomorrow.

There are stories of cars with a dead 12 V battery due to R-Link not going to sleep and sucking up all the stored energy. But this normally takes days not hours.

Did the guy try to load the 12 V battery? Some minutes should be enough because when the start button is pressed the battery will be charged by the traction battery via dc-dc-converter.

Maybe your 12 V is damaged (internal mechanically, this can happen but is close to a lottery win) and simply broke down.

Be sure to have the 12 V battery changed if it is discharged. Even one complete discharge leaves “marks” in the battery, you will have trouble with it again and again.

Regards and good luck
Umbi

I’m so glad that we’re not the only ones with this problem. We got our Zoe in Oct last year and it has been off the road for 4-5 weeks. Each time, it’s same message: ‘battery charging impossible’. Has happened on lots of types of chargers. Plug connector and charging main unit have now been replaced and yet fault appeared again a few days ago before finally resuming charging.

I would doubt that so much time at the end of the charge cycle is cell balancing.

Li charging for all chemistry types runs along a typical recipe:

First stage is that a constant current is applied to the battery. The battery, being a load, will cause the charging supply to be ‘pulled down’ to some voltage. As that fixed current is applied to the battery, the voltage will rise as the cell charges and the cell voltages rise. At some point, that voltage hits a level corresponding to, perhaps, 4V per cell (or whatever proprietary level Renault have chosen as an engineering margin for protecting the cells).

Li cells are tricky to know what SOC they are at. It is probable, IMHO, that when the charge level hits 99% this is not 99% SOC but is the end of the ‘constant current’ phase of charging. This is simply because the BMS can’t tell what SOC the cells are at, at the end of that constant current phase.

So the second stage then begins which is a constant voltage phase. In this phase the mode of charging changes and that 4V per cell (whatever the algorithm picks) is held steady. Because the cells are still charging, the current will now begin to drop. The constant voltage phase continues until the drawn current drops to 10% (or, again, whatever the algorithm is set to) of the constant current phase.

Throughout this constant voltage phase, the BMS doesn’t really know the SOC because the cell voltage is being dictated by the applied power from the charger. There’s no way of knowing the cell voltage, except by turning off the charging and allowing the battery to rest for a while until the open-circuit cell voltage can be measured. This would take too long to keen drivers wanting to drive off, so I am fairly certain that the long dwell at ‘99%’ is simply the constant voltage phase (sometimes called the ‘saturation phase’).

Interestingly, the slower you charge in the constant current phase, the shorter the saturation phase is. At 0.1C charge rate (which means a charge rate that takes 10 hrs of charging, e.g. 2.2kW for a 22kWh battery) there is almost no saturation phase. The faster you charge, the longer the saturation phase. There is a point where there is no advantage to trying a faster charge at constant current if you are aiming for 100% saturation charge as it simply extends the saturation charge period.

If you were to plot the drawn current during charging, you should probably find that at 99% the 30A charge current begins to drop, and will fluctuate downwards in a series of ups-and-downs as the BMS monitors whereabouts the SOC is. I expect it will probably terminate charging once it drops down to under 5ish Amps.

Cell levelling shouldn’t happen with every charge. If it does, then the battery is towards the end of its life, or at least some of the cells are. Cell levelling is wasteful and generates heat as the ‘high’ cells are shunted and the ‘low’ cells are differentially charged. Only if it is a very unbalanced battery pack will this need to go on for a long while. I have only observed it twice with the Fluence, once when I first charged the car at 3.5kW, and again some months later. Of course, you may well have caught an occasion when it was doing some cell levelling, but if it does it on every charge then, AFAIK, that would suggest the battery pack needs attention.

The ‘battery charge impossible’ message is something that many of us have seen quite a lot. This is the first time I’ve heard that there’s a problem with some of the BCPs though.

In common with jit187, my problems have been mostly around the fast chargers – but only those made by Elektromotive (Ecotricity’s rapid chargers are fine). When I contacted Charge Your Car about this, they explained that those charge points that pre-date the Zoe (which is quite fussy about everything being just right before and during the charge process) might not be set up quite right. And as Zoe is quick picky about the circumstances in which she’s happy to take a charge from a unit, if any of them is set up just outside these parameters, then it’s all off – hence the messages.

I’ve had this problem with Elektromotive units – both their fast chargers and their 7kw 305 units. It’s a recognised fault and (to quote the helpful guy from Charge Your Car):

“We have been made aware of an issue between the 305’s and the Zoe. It’s a bit complicated and I don’t know the technicalities but basically the Zoe draws so much charge from the unit that it is right on the edge of the charge points built-in safety margin; the point at which the charge point will think something is wrong and cut the power off. There is also a slight margin of error here and after the Zoe ramps up to full charge the vehicle tries to draw slightly more power than the 305 unit considers safe hence the problem you’re facing. It’s not exactly a fault with the unit or the vehicle. I suppose the best way to describe it would be a mutual disagreement regarding the standards”.

Apparently Zoe’s have been loaned for testing and a simple fix is being implemented by Elektromotive. Are the units that you’ve tried made by Elekromotive?

So, my advice would be do not despair. I’d suggest reporting the faults each charge point you encounter. And if Source London are as good as Charge your car, they’ll get onto it.

The fact that your home charger works ok is, surely, a sign that your car is fine? I guess Renault were quite specific about the specification for these home charging units (which might explain why BG were so ‘picky’ with getting the installations right?).