12v Battery - minimum voltage to start car?

Folks,

Does anyone know what the minimum voltage is for the internal 12V battery to enable the car to start? Reason is I have some equipment which will operate when the car is off and that equipment will stop working at a pre-set voltage and I need to set that so that it does not take the 12V battery below the car's starting threshold.

For older cars even with electronic ignition as long as the battery would turn the engine over it would start the car - but for newer cars the minimum working voltage of the engine management system is probably the determinant - for some Volvo models the minimum voltage is, I am told, about 11.5V which means that the slightest battery deterioration renders the car inoperable.

Anyone know what it is for the Outlander PHEV?

Best Regards,

Ian

I don't think the 12v battery on the Outlander is required to do much more than boot up the computers - after than, the traction battery is connected and tops up the 12v circuit via a power converter. I can imagine that if the voltage dropped much below 12v, you might have difficulty unlocking it, but once in, I would not be surprised if it was able to get things running at levels significantly below that.

One simple precaution is to take a spare smallish 12 V battery to start the car up, just in case. Such batteries are sold for domestic alarm systems, I think.

Thanks for the reply people but it doesn't answer my question.

The question is - below what voltage on the auxiliary battery will the vehicle not start?

The reason for the answer is that I want to run some equipment which drains current and which can detect what the voltage is and cease to operate before the required threshold is reached, thereby not stranding me. The same might apply if I were planning to leave the lights on.

Regards,

Ian

I have not managed to get the lights to stay on. As soon as I open the driver door, with the lights ON, and the power button OFF, the lights turn OFF.

The AUX battery recharger operates with the power button ON. The AUX battery will be topped up when the voltage falls below some preset value from the Traction battery automatically when the power button is OFF.

If you are really concerned then just see what happens yourself. You can purchase a cig lighter voltage display unit for about $10.

I would check myself no matter what advice I found on a forum for a critical operation. If you believe there is still a problem then an independent isolated battery may be a solution for the power hungry devices. Won't help if you want the lights to stay ON with the power button OFF.

A better question would be " How much energy drains with the PHEV stationery and aircon OFF and the power ON".

Why don't you just ask your dealer? I'm sure they have the figure in their documentation.

"The same might apply if I were planning to leave the lights on."
"I have not managed to get the lights to stay on. As soon as I open the driver door, with the lights ON, and the power button OFF, the lights turn OFF. "

If you have the 4h or better, the lights can be controlled from the app. Don't know why you'd want to leave the lights on, but there you go . . ! Not sure if they'll stay on for a pre-determined time that way, or until the battery runs out. And I'm not going to try it!

ibeeby said:

Thanks for the reply people but it doesn't answer my question.

The question is - below what voltage on the auxiliary battery will the vehicle not start?

The reason for the answer is that I want to run some equipment which drains current and which can detect what the voltage is and cease to operate before the required threshold is reached, thereby not stranding me. The same might apply if I were planning to leave the lights on.

Regards,

Ian

Click to expand...

I suspect that the actual threshold is the voltage at which the auxiliary battery will become damaged. It's a pretty standard small lead-acid battery and if you take it below about 11.5 volts, you will physically damage it and reduce its life expectancy. I would expect that the car would still boot up at that level.

Did find the lights were programmed to turn OFF in the settings, so changed that for a test.

Left the lights ON, high and low beams, so about 250W total draw, with power to ACC only. orange light. AUX voltage started at 12.2V and slowly dropped through 11V and down to 10.8V. Was tested for over an hour and voltage did not fall below 10.8V.

Powered PHEV to ON no trouble. Did have an FCM warning come up, and FCM stayed OFF. Was able to reset FCM the next power cycle.

Lost a bar on the main battery, so energy was transferred from the main to AUX battery. ICE operated from power ON in SAVE mode, and this does not normally happen.

If the main battery was very low and the test was repeated, then I suspect the PHEV would be a no go.