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Battery power gauge accuracy

I usually charge my Twizy overnight, but today because of regular use, I recharged it during the day to make sure I could complete my next journey. I didn’t make a note of how long it had been charging but when I went out to look, it said 90% charged with one empty bar on the power gauge. But when I switched on the ignition, the power gauge shows 100% charged with no empty bar. Now that makes me question the accuracy of the power gauge. I wonder how many of you actually ever see the end of the charging cycle to see if it says 100% charged, because as in my case a 90% charge will show up as 100% when switched on. Also how can we tell it will not charge more than 75%, the point when Renault will replace the batteries, if the power gauge is not accurate.

Each of the battery bars represents 10% of battery capacity. There are 10 segments, so all 10 showing represent 100%. When plugged in, and charging, it tells you slightly more when the bar is flashing, you are within 1-5% of that segment, if steady then it is 6-9% of it.

I often see the battery display go from 98% to blank and shut down - showing a full charge, the % figures being a guestimation.

Finally, nothing on the twizy will advise you have reached the 75% range limit - only the fact you are only getting (say) 30m from a full charge where you usually got 40. I mean these to be real-world road figures, not the digital display, which will show you 100% even when you have only 5% of the original capacity. The way to tell is when the range indicator gives usual readings for the first 20m, then plummets (sometimes dropping by 4 or more miles for every mile you actually travel).

I usually charge my Twizy overnight

How long!
If the Twizy is completely flat it only takes 3 hours to charge.
I put the Twizy on charge as soon as I get home, sort my Dinner out and its usually finished charging. (I do 16-20 Miles a day)


if you are only covering 20 miles a day then you should be recharged in one hour.


mine always says 100% before switching the display off, i check it often during my evening charging.[/quote]

The battery “bars”, as Buzby says, only have 10% accuracy. So although 10 bars, if you have completely charged the Twizy, does mean “full”, you will lose one of those bars when the state of charge drops to 89% of capacity, and the next one when it drops to 79%, and so on. When you’re driving along, unless you notice when a bar turns off, it’s best to assume the worst - i.e. that 10 bars means at least 90%, 9 bars at least 80% etc.

As others have said, charging above about 97% of capacity is an almost indeterminate process. If you inadvertently leave the ignition on, the charger may never complete. The way the charger works means that the last 30 minutes of any charge is very inefficient, and unless you really need the tank to be 100% full, you can safely stop at about 95% without much loss in range and 30 minutes time saved.

Here (if it loads OK) is a graph of charge state versus time that we use to work out how long it’s going to take:

I use one of those basic timer sockets, which switches on at 3.00am and switches off at 6.00am. That is more than adequate time to fully charge the battery as I never let it run totally flat. To be honest, I don’t really know if there is much point for me to charge overnight as I don’t even know if I get cheaper rate electricity at night.

If your meter has 2 sets of readings, then you will usually have an off-peak tariff - look at your bill for the definitive answer. I have Economy 7 /White Meter and can hear my meter switch over at 00:00:00 and 08:30:00 as it is controlled by a Radio TeleSwitch.

My recharge socket is only energised during Off Peak, and whilst the Twizy may not need all 8.5 hrs, it is not a good idea to limit the period to (say) three hours. The battery gets quite hot as it reaches max and the fans kick n to cool it - and will over run if need be once charging is complete to cool the pack. Shutting off the power early means the pack is not cooled and may lead to degredation.

Thanks. I will have a look at my bill next time.
As I said I never let the battery run too low, so 3 hours should be perfectly adequate to charge and cool. Besides the fan will continue to run even after it has been switched off at the mains. I think it must also run from the aux battery.