Q: Battery Voltage

[SM-17]

Since i spend hours in the garage doing things and listening to music from the head unit, I would kindly like to ask what is the minimum battery voltage to start a toyota vitz with 1kr-fe 996cc engine.

I have battery monitor on head unit and would like to set the minimum (safe) voltage to shut down the unit leaving safe and enough power to start the engine

Thanks

[Bluevitz-rs]

That totally depends on the condition of the battery.

[SM-17]

Battery is brand new 45ah

Thanks

[Bluevitz-rs]

In that case you could probably drop to 11.5V and still start but doing that on a regular basis will destroy your battery and charging system very quickly.

[CoryM]

Just to add on, the car's charging system is not built to charge the vehicle from low voltage. It's only intended to top up what is used to start the car and a few other high-load things. Your alternator will fail early if you use it to charge the battery like that. It would probably be more cost effective to buy/build yourself a small shop radio.

[SM-17]

thanks for the replies.

I have been monitoring battery voltage whilst driving the car, the alternator is always supplying 14.1 to 14.3 weather the battery is full, half or flat. (the Alternator is supplying voltage all the time the engine is running) ... I can understand that when a battery is flat it demands more Amps from the Alternator but that shouldn't be a problem. I jump started the car with a flat battery (on purpose) to monitor the Alternator and after a 2Km drive the battery was able to restart the car (996cc petrol)

my other car is a skoda favorit (26 years old) last time I replaced the battery was in January 2006 (VMF Battery) and it's still good to this day, it has been treated the same way I am treating this new battery even though I don't expect it to last that long.

I have some experience with sealed lead acid batteries (model tugboats) and can say almost for sure that they give longer life when refreshed (charged/discharged)

[kevinj93]

There are diferent types of lead acid batteries.

The type you normally find in a car is designed to supply very high current for a short length of time to start the engine, then be recharged and kept nearly full.

The other type normally found is a Deep Cycle battery, which is designed to be repeatedly discharged and recharged, but is not designed to provide the high current neded to start a car.

Many 4 wheel drive owners who go camping wil have 2 batteries installed in their vehicle. One will be a normal starting battery, and the other will be a deep cycle battery. There will also be an isolator to separate the two batteries when the engine is not running, but provide for charging both from the car alternator.

All the power for their camping equipment comes from the deep cycle battery, with no worries about not being able to start the vehicle later.

It might be a tight squeeze to fit a second battery in a Yaris....