Author Topic: Battery lesson (Read 10406 times)

Kremmen · « **on:** June 11, 2024, 10:40:01 AM »

Since moving I've been doing fairly regular DIY runs. I haven't used the CTEK as I'm now doing more mileage

However, last week, on a local run, I noticed the battery bar was only going between 3 and 4 on a regular basis. No higher, just 3 4 3 4, etc

The engine was still cutting in and out but when in it seemed to be revving higher

Over the weekend I gave the 12v battery a CTEK which took 8 hours to complete like it did with little to no use

Been out today and the battery bar is now going between 3 and 7 as normal

So it seems 5 mile each way round trips twice a week isn't enough to keep the 12v battery topped up

One to watch ?

madasafish · « **Reply #1 on:** June 11, 2024, 11:00:16 AM »

Quote from: Kremmen on June 11, 2024, 10:40:01 AM

Since moving I've been doing fairly regular DIY runs. I haven't used the CTEK as I'm now doing more mileage

However, last week, on a local run, I noticed the battery bar was only going between 3 and 4 on a regular basis. No higher, just 3 4 3 4, etc

The engine was still cutting in and out but when in it seemed to be revving higher

Over the weekend I gave the 12v battery a CTEK which took 8 hours to complete like it did with little to no use

Been out today and the battery bar is now going between 3 and 7 as normal

So it seems 5 mile each way round trips twice a week isn't enough to keep the 12v battery topped up

One to watch ?

5 miles is 10-15 minutes time. With two starts in that period.
A 12V battery usually takes 30 minutes plus to recharge..even a moderate discharge with no startups...

5thcivic · « **Reply #2 on:** June 11, 2024, 12:21:52 PM »

Seems too little for good charge with an alternator, - without one we don't know the exact routine of these hybrids with micro controlled charging from an HV battery. EVs and hybrids are more expensive to buy and it seems manufacturers do seem to save some on the 12V battery, although even a high Ah one will need toppiing up sufficiently. But a small one does not seem to last well while stopped for some time, particularly in the cold.
I too drive little and in cold weather it seems the engine likes to charge up to 8 bars or so from start up, presumably to excersise the cells in rotation, in warm weather sometimes not so high. One would assume some charge from the engine running must be used for the 12V too depending on its state?
Still without a reasonable commute usage, trickle charging remains a good idea.

ahavoja · « **Reply #3 on:** June 11, 2024, 01:06:55 PM »

Quote from: 5thcivic on June 11, 2024, 12:21:52 PM

I too drive little and in cold weather it seems the engine likes to charge up to 8 bars or so from start up, presumably to excersise the cells in rotation, in warm weather sometimes not so high.

I have a feeling that in a cold weather start, the engine keeps running for a while to heat up the cabin air, and while doing so, it also charges the HV battery.

Quote from: 5thcivic on June 11, 2024, 12:21:52 PM

One would assume some charge from the engine running must be used for the 12V too depending on its state?

Yes, I think so. I did a 19 minute drive today. I measured the battery voltage and it was 12.51 V before the drive and 12.86 V after the drive.
If the photo below is correct, it means my Jazz charged the 12V battery from 70% to 90% during that drive. I have never used a CTEK on my Jazz, but I have been driving almost every day.

Kremmen · « **Reply #4 on:** June 11, 2024, 01:24:38 PM »

My gut feeling is that the battery meter reads both HV and 12v

I've had instances where I know the HV is quite full and a CTEK has resulted in the battery meter going straight to 10 on next powerup

olduser1 · « **Reply #5 on:** June 12, 2024, 07:34:52 AM »

8 out of 10 cars I used to see had a battery 30-50 charge, very few owners open the bonnet , I imagine modern cars need maintaining something many manufacturer kid us on no longer needed with sealed for life etc etc. As other comments check your battery charge as we approach autumn N winter. Low voltage charge = likely breakdown call out.

Bristol_Crosstar · « **Reply #6 on:** June 12, 2024, 09:15:20 AM »

I think it certainly a good idea to check the 12V battery voltage occasionally if you're only doing short journeys, I usually do a couple of top-up charges in the winter.

Regarding charge taken out when starting the car the hybrids aren't started in the traditional sense, more just switched on so it doesn't take so much out of the 12V when starting a journey. The petrol engine is started by the HV battery to my understanding which is why only a smaller 12V battery is required.