15 minutes to kill

[sido]

I was waiting at the train station to pick my wife up when she text to say the train was delayed by 15 minutes.
I have been waiting for a chance whilst stationary to fiddle with the power used by individual elements of the car and noticed the following.
I have the MG5 SR 2021 model. I had 83% charge and with the car started but nothing turned on the GOM showed 189 miles and the amp meter showed as 1. Then turned on headlights amp meter showed 4, I have upgraded bulbs to Nightbreakers. Then turned on fan to full, amp meter showed 14. Then turned on rear window heater amp meter moved to 17 and with windscreen wipers on 18 to 19 on the amp meter. I let this run for 5 minutes and the GOM moved to 162 miles. I did this twice just to check but each element responded exactly the same. Oh, and my % dropped to 82% after both runs. I have absolutely no idea how to interpret this info but I wonder if one of you can?
It seems to me that the GOM anticipates you are going to use more power in N or S mode than Eco, I wonder if it is right?

 

[Ozzie1989]

Does the amp meter measure the HV or LV battery pack power draw?

 

[sido]

I don’t know but assume hV

 

[Ozzie1989]

Ok let's assume it is (because two 55w headlights would draw approx. 9 amps from the LV battery in use).

So with the headlights on your usage increased by 3a, you can calculate this into kWh by doing the following:

3amps (power consumed) X 350v (nominal voltage of HV pack) = 1050w (or 1.05kw) per hour

So with your SR model you'd get approx. 45 hours of headlights usage before flattening the HV pack.

Another way to look at it is that for every hour you have them on you'd loose 3 miles (assuming 3 miles per kWh efficiency).

If you do the same with the heater:

10a X 350v = 3500w (or 3.5kw) per hour

You could then say that for every hour you have the heating on you are loosing 10.5 miles (assuming 3 miles per kWh efficiency).

 

[sido]

Ok let's assume it is (because two 55w headlights would draw approx. 9 amps from the LV battery in use).

So with the headlights on your usage increased by 3a, you can calculate this into kWh by doing the following:

3amps (power consumed) X 350v (nominal voltage of HV pack) = 1050w (or 1.05kw) per hour

So with your SR model you'd get approx. 45 hours of headlights usage before flattening the HV pack.

Another way to look at it is that for every hour you have them on you'd loose 3 miles (assuming 3 miles per kWh efficiency).

If you do the same with the heater:

10a X 350v = 3500w (or 3.5kw) per hour

You could then say that for every hour you have the heating on you are loosing 10.5 miles (assuming 3 miles per kWh efficiency).

Thanks Ozzie1989, this is exactly what I was hoping to find out. Probably of no interest to most but I do like delving and understanding the impact of each item on the car. It won’t change my driving habits but I will know where my KWhrs are going. Much appreciated.

 

[m4rmite]

I've noticed when you turn on the heating it seems to take 10% off your initial gom range, regardless of whether it was showing 200 or 100 miles.
So 20 miles off the 200 and 10 off the 100.

This is when in normal

 

[Jomarkh]

Hi, I did a similar thing turning things on etc. It is funny how the lights, rear heater and wipers change the current drain as they are on the 12v battery.
Does anyone know what the charge current from the HV pack to the 12v battery is?
I use 1% gives me 2 miles as a gauge. The GOM also takes into account your long trip figures so if you reset that you get a different reading.

 

[Ozzie1989]

My understanding is that the LV battery is charged from the HV battery by a DC converter. There will be some losses, as there always is with power conversion.

If something draws 10amp from the 12v battery then it would be drawing roughly 0.5amp from the 350v battery (not allowing for losses).

Once I get my hands on the car I'll be conducting some tests myself particularly after seeing this thread as 3a draw after turning the headlights on seems very high to me.

 

[Ealing Guy]

If you check the current when you are charging (or if you want to check that you are charging) it goes negative. Then if you switch some things on it counts up and down very rapidly every few seconds, at least on my ZS unfacelifted model