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Hi As above, but make sure you use one with a fuse inline, as close to the battery as possible otherwise if you get a short on that wiring it will just catch fire cheers Joe

Hi David, here is my set up,

Maybe once a fortnight or once a month, take it for a longer run to give it a bit of a concentrated charge to help get round this problem. I use a 1988 Volvo 760 as my "Dogmobile" so its use is predominantly very short runs, however every once in a while i'll take it for a longer run to recharge the battery and blow the cobwebs out.

Maybe that’s it then as my drive to work was about 15 mins. It is a MY10 XF and Portfolio so has all the electrical extras.

Hi Low battery will cause this, especially if its a diesel on startup, short runs will not allow the battery to recharge ideally above 12.5 volts with engine off, if battery goes below 10.8 while cranking, it will put modules in fault. youve not said what car it is but on S-types, XJ's and early XF's the battery voltage with the engine running will vary between 13.6volts and 15.3volts on first startup but as allready said put it on charge overnight and see if it cures it but start up take so much out of the battery, especially on diesels and a 15 minute run wont put back in what was taken out on startup can recomend a CTEK smart charger which can be left on when not in use to keep the battery fully charged, CTEK as used by jaguar oe chargers cheers Joe

A fully charged battery is 12.7V : Your alternator should put out in the region of 15.1-14.7V depending whether cold or hot, the voltage may go up slightly on the upper level due to certain things like load etc, especially at idle but the battery is almost certainly a calcium/silver-calcium type which refers to the doping on the plates to prevent sulphation."Normal" lead-acid batteries have lead-antimony doping and need 14.4-13.8V to charge, the calcium increases the charging voltage by 0.1V/cell and with 6 cells, each of 2.2V (total 13.2V) you can see where the extra 0.6V of charging voltage is needed. With so much electronics on cars thse days and so many things referenced to a stabilised supply of 5V, 10V, 12V etc and a variable battery voltage, it's easy to see if the battery drops below a certain level of charge, strange things will happen. To put this into perspective, many sensors work on the potential divider principle where two resistors in series divide the battery voltage. One of those resistors will be the sensor but these derived voltages will be compared to a known voltage from one of the stabilised supplies. To make the figures easy, let's say one of the stabilised reference voltages is 6V. Let's make a sensor where the resistance is 6k and is fed by a 6k current limiting resistor which provides a total of 12k Ohms. Call the sensor R1 and the limiting resistor R2, the voltage developed across R1 = VR1 = Vb x (R1/(R1 + R2) so in this example, VR1 = 6/12 x Vb (Vb is battery voltage) so at 12V, VR1 will be 6V. If the threshold for a fault is 5.9V compared to the stabilised 6V supply, no fault will be shown but if the battery voltage drops to 11.5V, VR1 will also drop to 5.75V and hence register a fault. Bit long-winded for a simple explanation but hopefully gives an insight into how these things work!

The more you drive it the more charge will go into the battery. The fact you now have no warnings is proof of low voltage. Before you go spending on a new battery, give your existing one a full charge. If it still loses voltage then by all means replace it.

The first thing to do is fully charge the battery and then see what happens. After that you’ll need to have the codes read to see what the car is saying is wrong.

Yes you can Rob. As you have no BMS fitted to your car you can attach direct to the battery though it is best practice to connect the negative of the charger to a suitable ground point.