Low Battery - Reduced Power

[WAC 768]

Just noticed when the low Battery warning comes on the cars now limited to 60% power, which i can't remember this happening pre the Jan BMS update but maybe it did, anyone else noticed this?

 

[JodyS21]

Curious, not had it happen yet, but how can you tell it's been reduced to 60% power?

 

[Mike]

I had this a lot especially in cold weather on the last BMS update from October.

I’ve not experienced it as much now, but it does have a tendency to do it under 20% SoC especially if it’s cold.

There was one occasion going up a hill, not even rated as a percentage, but it was steep, and the car slowed from 30mph down to 25mph! It was around -1°C and my SoC was below 20%.

 

[WAC 768]

I had this a lot especially in cold weather on the last BMS update from October.

I’ve not experienced it as much now, but it does have a tendency to do it under 20% SoC especially if it’s cold.

There was one occasion going up a hill, not even rated as a percentage, but it was steep, and the car slowed from 30mph down to 25mph! It was around -1°C and my SoC was below 20%.

Hi Mike, thanks for the reply and just experienced a maximum of 20% power @ 25MPH on what was only a 2% incline, so not even a hill but did only have 11% SOC remaining. I would though have thought having the new BMS this would have been resolved?

 

[WAC 768]

Curious, not had it happen yet, but how can you tell it's been reduced to 60% power?

Just put your foot flat to the floor and you'll see the power gauge not go past 60%

 

[Mike]

Hi Mike, thanks for the reply and just experienced a maximum of 20% power @ 25MPH on what was only a 2% incline, so not even a hill but did only have 11% SOC remaining. I would though have thought having the new BMS this would have been resolved?

I’m not so sure yet, as yes, you may have the new BMS, but how out of balance is your battery? Whats the voltage fully charged like now?

 

[WAC 768]

Fully charged and balanced the cars showing 450v which from previous posts seems to be the new normal. Worrying though if MG has rolled out the fix to resolve the balancing, yet accidentally introduce another and more potentially dangerous bug....

 

[Mike]

If the range is the same, then its not a bug, plus many people complained that their cell values were too high.....

 

[JodyS21]

Just put your foot flat to the floor and you'll see the power gauge not go past 60%

Ahh gotcha - the dial on the right! I've not took much notice of that dial so far!

 

[JodyS21]

I was thinking when heard about this power reduction at low SoC, that it shouldn't cut the power but just warn you, it's up to you to decide if you want to conserve the juice more - if only got 1 mile left of your journey there's no need to save juice etc.

I'm just wondering now, could it actually be a battery limitation...
Do batteries once they get to a low state of charge get damaged by draining them at a high current? Maybe that's the reason why, it's to protect the battery cells???

 

[macd2401]

Might be a safety thing. Lipo batteries tend to just stop working when they reach their limit, rather than tail off... they probably don't want you hammering along at say 70, then you lose everything.

 

[WAC 768]

I was thinking when heard about this power reduction at low SoC, that it shouldn't cut the power but just warn you, it's up to you to decide if you want to conserve the juice more - if only got 1 mile left of your journey there's no need to save juice etc.

I'm just wondering now, could it actually be a battery limitation...
Do batteries once they get to a low state of charge get damaged by draining them at a high current? Maybe that's the reason why, it's to protect the battery cells???

All EVs at some point will limit the power normally when under 10% by limiting your maximum speed to around 50MPH, then when nearly empty to around 30MPH and in most cases, you are warned, unlike what I am experiencing.

Today again and with 36% SOC (41 miles) the power was restricted to 60% power, stuck on charge whilst shopping for 40 mins and with SOC around 43% (55 miles) 100% power was available... Annoyingly this only started after having had the latest BMS update (Mid Jan 21) before than i had never suffered any power loss..

 

[Gomev]

All EVs at some point will limit the power normally when under 10% by limiting your maximum speed to around 50MPH, then when nearly empty to around 30MPH and in most cases, you are warned, unlike what I am experiencing.

Today again and with 36% SOC (41 miles) the power was restricted to 60% power, stuck on charge whilst shopping for 40 mins and with SOC around 43% (55 miles) 100% power was available... Annoyingly this only started after having had the latest BMS update (Mid Jan 21) before than i had never suffered any power loss..

Where did you have the update done? It sounds like something is not right, that's not normal behaviour. Maybe not everything was done/completed.

 

[Mark Holmes]

Where did you have the update done? It sounds like something is not right, that's not normal behaviour. Maybe not everything was done/completed.

Agree, I’d ask them to reinstall it again or ask the question at least.

 

[WAC 768]

Cars going in tomorrow, but have found the power first reduces to 60% once the battery voltage goes below 400V which is around 38% SOC. Having worked for many years within the automation industry every software download is based around a succesful checksum, so you would assume the BMS is good but then again.....

 

[Jasonmgev]

Ahh gotcha - the dial on the right! I've not took much notice of that dial so far!

yes same issue here and got the update last week

 

[WAC 768]

yes same issue here and got the update last week

Interesting and wonder if this could be a common problem, post update, which if you charge daily and don't let the SOC go below 40% you would never notice this...

 

[Jasonmgev]

Interesting and wonder if this could be a common problem, post update, which if you charge daily and don't let the SOC go below 40% you would never notice this...

True as I am getting terrible mileage at the moment so doing tests and coincidently am running my battery low and checking things and now literally just noticed this while driving now , and came to check of it was happening to anyone else as I put my foot flat and get nothing .. well max limited on all modes , even when I turn esp off

 

[Jasonmgev]

True as I am getting terrible mileage at the moment so doing tests and coincidently am running my battery low and checking things and now literally just noticed this while driving now , and came to check of it was happening to anyone else as I put my foot flat and get nothing .. well max limited on all modes , even when I turn esp off

 

[WAC 768]

After further investigation 60% power, reduction starts once the battery voltage goes under 400V and then ends up where with my foot pressed hard to the floor it barely gets over 20% power with 16% SOC still remaining. In today so let's see what MG says, but this is clearly unacceptable...