Max Traction battery charge

[Bowserman]

Whats the highest up the scale you have had on the Battery indicator?

Been on a hilly drive this morning and it went right to the top for the first time, except for the three little bars.

[Herbie]

On long descents mine often goes right up to the top.

[NemesisUK]

Routinely see fully charged except for the very last segment.

[BoutTime]

Had mine on full bars quite a few times but barely use that screen. I normally have it on the trip screen.

[Thackeray]

A couple of days ago, I came across this interesting video of a hybrid being driven down a mountain road. Obviously the hybrid Battery is potentially being charged continuously mile after mile. 

It seems to suggest that the system works to prevent the hybrid Battery being charged above 80% - which I assume is eight bars on the dashboard monitor. The video uses the Hybrid Assistant app, which shows the Battery charge of around 78-80% on the right hand side. Next to it is the engine rpm figure in a graphic shaped like a piston. As the car speeds up downhill and the Battery gets to 79% charge the engine starts to spin around 1500 rpm to provide engine braking. But as the Battery gets closer to 80% the engine speeds up to around 3500 rpm (quite noisily) to provide more engine braking.

The app also shows when there's any mechanical braking in the symbol in the top left next to the speed. The brake symbol turns red when the driver applies the brakes.

The commentary is in Italian but in the settings at the bottom right of the video you can set auto-translated subtitles in English.

 

[NemesisUK]

That's pretty much how I understood the system operates. I'm sure it's been explained on here before with regard to regen v hydraulic braking.

[ColinBarber]

The trick to getting the Battery pack to last so long it to not over charge it and not let it discharge. Therefore the Battery bars on the display represent about 25% to 75% and the hybrid system won't normally charge the Battery above 60% so there is some headroom for regenerative braking electricity to be stored.

[Herbie]

22 minutes ago, Thackeray said:

It seems to suggest that the system works to prevent the hybrid battery being charged above 80% - which I assume is eight bars on the dashboard monitor

It does prevent the Battery from being overcharged but I'm not sure if there's a correlation between the 80% and the 8 bars on the dashboard monitor.

As the driver or end user of the car, we don't have access to all of the capacity of the Battery. I can't remember if we get to use 60% or 80% of the total Battery capacity but for the sake of this topic we'll assume it to be 80%.

So, if you think of it as a vertical scale from 0 at the bottom to 100 at the top, we are blocked from using the first 10% between 0 and 10, and the last 10% between 90 and 100. As I understand it the dashboard meter indicates the level of charge in the part of the Battery that we have access to, not the SOC of the whole Battery, so when we see all 8 bars lit up it means that our part of the Battery is fully charged but not necessarily the whole Battery.

In reality, of course, the Battery isn't physically sectioned off into 'ours and theirs' and it's all done electronically, but I do remember reading that the charge indicator only relates to 'our' part.

When going downhill and the traction Battery becomes fully charged and cannot accept any more, MG1 spins the engine to provide a variable amount of engine braking, which is used as resistance to 'use up' the surplus electricity.

 

[BoutTime]

4 minutes ago, Herbie said:

It does prevent the battery from being overcharged but I'm not sure if there's a correlation between the 80% and the 8 bars on the dashboard monitor.

As the driver or end user of the car, we don't have access to all of the capacity of the battery. I can't remember if we get to use 60% or 80% of the total battery capacity but for the sake of this topic we'll assume it to be 80%.

So, if you think of it as a vertical scale from 0 at the bottom to 100 at the top, we are blocked from using the first 10% between 0 and 10, and the last 10% between 90 and 100. As I understand it the dashboard meter indicates the level of charge in the part of the battery that we have access to, not the SOC of the whole battery, so when we see all 8 bars lit up it means that our part of the battery is fully charged but not necessarily the whole battery.

In reality, of course, the battery isn't physically sectioned off into 'ours and theirs' and it's all done electronically, but I do remember reading that the charge indicator only relates to 'our' part.

When going downhill and the traction battery becomes fully charged and cannot accept any more, MG1 spins the engine to provide a variable amount of engine braking, which is used as resistance to 'use up' the surplus electricity.

 

Exactly this. We only see the usable capacity. Mine often goes to full bars after coasting downhill.

[Britprius]

The actual usable Battery capacity is is 40% "zero bars to all green bars". The maximum discharge level is 40% of capacity, and the maximum charge level is 80% of capacity. 
The normal cycle life of quality NiMh batteries is about 1000 cycles "fully charged to fully discharged. By only using the narrow charge cycle range of 40% increases the cycle life to many hundreds of thousands cycles.

One of the anomalies of the system is that if you are going downhill with a fully charged Battery the engine will spin at speed to dump power. On putting your foot on the accelerator the engine will slow down or stop as the car uses electricity to increase the called for extra speed. 

John.