The point is the battery is not fully charged at 12.3 volts, the B-max charging sensing circuit which is incorporated in the negative battery cable located adjacent to the negative battery terminal thinks it is fully charged. This is dictated to by firmware I believe.

I know the battery is not fully charged by the vehicle cos after the battery is rested my battery analyser indicates approx 60% at 12.3 volts. It is only fully charged from the smart charger.

The only issue is that not charging the battery to near 100% by the vehicle will probably shorten the life of the battery unecessarily. I posted this in the hope of a discussion and not that I had a starting problem.

Edited by rustbucket on 15/04/2018 at 22:27

My thoughts? It is now too easy to get lots of info from vehicles and use it to over analyse and identify a problem where none exists.

Actually a problem does exhist as undercharging causes sulphation and shortens the life of the battery and unecessary expense in replacing the battery.

You may not have had to replace a battery in the last 5 years but there has been plenty of examples where some batteries in this situation have lasted only a year or two.

Edited by rustbucket on 16/04/2018 at 14:57

Testing a smart charge system on a modern car needs more than just a voltmeter and the result of a battery charger. I would be looking at testing the battery with a conductance tester and then interogating the power management system with suitable diagnostic equipment.

The battery fitted from new is an EFB (new vehicle registered October 2017).

The hand book with the car says for fitting a new battery just disconnect old one after waiting for the system to shut down, ignition off. Fit new battery and set up stations on the radio. No mention of anything else.

My concern is battery never charges to anything higher than approx 60 % on the vehicle, will charge to 100% from a smart charger. 60 % will probably shorten the battery life, but as the engine is not putting power into recharge the battery to 100% its probably done for economy reasons.

This on several other forums has also been mentioned re the charge of only approx 50-60%.

I wonder if other vehicle makes do similar tricks to improve economy?

Edited by rustbucket on 18/04/2018 at 17:21

Hi Perfection.

I read your post with interest and noted the comments from others. It appears that the start /stop vehicles have a rather strange charging patterns. As you said its all to do with maximum economy low emmisions at the expense of more frequent battery replacement. So what we gain in one hand we pay for with the other. In my post it was suggested I had an inaccurate voltmeter or other missunderstanding of what I was doing - not so just a not very intelegent battery charging system adopted by manufacturers. In one of the replies I read it was suggested that more sufisticated equipment was required to properly analyse what was going on but with a basic voltmeter (calibrated), 55 plus years engineering experience my diagnosis of battery only being charged to approx 50 -60 % was correct. Even with new battery technology its not good to only charge a battery to this low level.

Edited by rustbucket on 20/04/2018 at 08:05