CTEK Battery Monitor

[Harley Dave]

I got one - anybody know how to download the voltage graph??

Cheers

Dave

[SwissXC90]

I have one too.

No download of data exists, only thing you can do is screenshot it.

PS: do you also suffer the following problems:
1. Date is shown in wrong format, does not use the same format as your iPhone
2. Vertical intervals on the graph are totally weird time intervals
3. Voltage and Temperature do not display when not connected to the car

I've sent CTEK feedback asking them to fix these issues

[SwissXC90]

Here's a long term view of my battery voltage:


The two negative spikes were from leaving the parking heater running, and forgetting to turn the lights off.

The general decay from 100% to 80% is caused by not using the car, every blip going positive is when I used the car.

The sharp sudden rises to 100% are when I connect the battery charger.

The long periods at 100% are caused by initially charger connected and then a fair amount of driving.

[Harley Dave]

Thanks Swiss - As I anticipated - you have provided more info than I have.

I also get the steady decline overnight - down to 80% - a colleague of mine suggests this is due to cooler conditions at night having a negative impact on terminal voltage??

I also get a small "charge" showing with a couple of hours driving at 50 mph/80 kph but a big charge when I leave the battery tender connected.

I'm not sure if I know how to "screen shot" on my Android One+2 phone but I'll look into it.

Be back later with more data but feeling a bit more secure now - Thanks.

Cheers

Dave

[Harley Dave]

And google is my friend (again)

Here's a screen shot of my results

The big/long drop was when I was parked up on traffic survey duties; it was raining and I had to keep switching on to operate the wipers.

The upward curve after is overnight battery tender connected

I need to start logging exactly what's happening Parked - Driving - Charger connected - etc etc

My concern is that the terminal voltage falls away overnight down to 80% ish on a frequent basis - (in steps it looks like) - what causes this? (obviously alarm etc contributes...) but why the steps...

Cheers

Dave

[SwissXC90]

Originally Posted by Harley Dave

My concern is that the terminal voltage falls away overnight down to 80% ish on a frequent basis - (in steps it looks like) - what causes this? (obviously alarm etc contributes...) but why the steps...

The discharge when the car is not running is completely normal for any car with a wet lead acid battery.

The charge slowly drops because
a) constant power drain from the car: clock, alarm, central locking, Volvo OnCall, and any other device using a memory: all use power all the time
b) self discharge in the battery, which increases at lower temperatures
c) chemical age of the battery: older batteries are less capable of holding a charge than newer batteries, due to the chemistry involved


The CTEK Battery Sense takes some time to properly reflect the battery's state of charge.
However you have had the CTEK Battery Sense connected for over a month, and me now for also about 2 months.
So our CTEK Battery Senses should both have "learned" the charge cycles and be accurate (as can be).

The fact that the battery drops about 1% state of charge a day was something I was not aware of, and never noticed, until I connected the Battery Sense. With measurements comes knowledge and insight.

The Battery Sense does a great job of informing you as to the current state of charge, and when you should make the decision to connect a battery charger.
As you can see, the battery sense estimates the time taken to recharge the battery (this is based on battery size which you configure in the app, as well as current temperature and charge voltage.).
The time to fully charge the battery is actually much longer than you think!
We used to say "drive for 30 min after starting a car from a flat battery to charge it up enough" but that would never have brought a 100% charge.
It simple brings "enough" charge to keep you going.


I saw my battery was at 80% on Friday night, so I put my 5A battery charger on the car at 21:30
The Battery Sense reported that the battery was fully charged at around 05:00, which is a charge time of 7.5 hours
At 5A charger capacity, 5 x 7.5 = 37.5Ah added to my 90Ah battery.
But the calculation is not that simple because the charge current and voltage is regulated, it is not a constant 5A. The CTEK charger reduces the charge current as the voltage increases.
Assuming it is on average about 50%, that means the charger loaded about 18.75Ah to my 90Ah battery.

Battery Sense reported the battery as being 80% before charging, which would be 72Ah (90 x 0.8 = 72)
72Ah + 18.75Ah = 90.75 Ah

At which point I must congratulate myself on my math and my assumptions, because the results are perfect



And as for the steps: you are simply seeing the charge time (engine running, charge state increasing) vs discharge time (engine not running).
You should be able to correlate the data to your drive cycles.

If you can, put the charger on for 24hrs to bring the battery back to 100% charge. Then monitor how it holds it's charge.

[Harley Dave]

Thanks Swiss - I've been a bit busy of late but I have a 2.5 hr drive on a fast dual carriageway tomorrow and then back again towing, so a bit slower, but there'll be 6 hours of driving in the day - I bet I don't get to 100% though...

The steps I was referring to were the discharge steps overnight when the car sits outside the house, "switched off" - I would have expected a linear discharge curve from time of parking to time of next drive but instead it seems to drop, then hold for a while then drop again.

Mind you that might be a function of how the CTEK represents the voltage between "Sample Times" which seem to be every 5 minutes.

I agree I need to start keeping a log of what journeys I do, at what times and for how long then correlate that info with the data from the CTEK to get a real picture.

As it is I will soon be away on the bike for 3 weeks and the car will be parked up not being driven. - I will of course leave it on the charger...

Cheers

Dave

[SwissXC90]

If the vertical resolution of the graph is 1% SoC, then steps will be clearly seen.