Battery at 9% and then dies

[leftside]

I have my Garmin 530 connected to the Decoy, so I can tell exactly how much battery I have left. The bike just got me to the top of the final climb, but then it died with the battery at 9%. I thought I should have had enough juice left to finish my ride.

Anyone know why the bike doesn't want to go into eco/trail/boost even when there appears to be some battery juice left?

 

[Maherto]

I had something similar not sure of exact % left but it would turn off when using boost and trail mode in eco it worked for a bit though. I think the battery icon was flashing as well but I could be wrong. I think they have to have 2 hours of juice left by law to power lights so maybe thats why at 9% your done. They a heavy anchor with no asisst

 

[leftside]

I had something similar not sure of exact % left but it would turn off when using boost and trail mode in eco it worked for a bit though. I think the battery icon was flashing as well but I could be wrong. I think they have to have 2 hours of juice left by law to power lights so maybe thats why at 9% your done. They a heavy anchor with no asisst

That would make sense. I'm just glad I made it to the top before the battery died. I often set it to "Off" if I know the descent is going to be all dh to save battery life.

 

[wildsau2]

Bike brands dont specify the total usable amount of battery capacity, they only specify the total capacity. I always think they should do that by law. As an example Car brands MUST specify the usable amount. your 9% “sweetspot“ seems ok. i had a bike with the Brose system which shutdown at 20%.

 

[flash]

Just like the fuel gauge in a car, I would always consider any bike battery gauge an estimate. I have yet to see one that is actually truly accurate. The system is programmed to shut down at a particular voltage (which might be well above the safe limit for lithium or with enough power to run electronic gears etc..). The percentage estimates when that might be but doesn't actually know. The voltage drop from full power to shut down isn't linear either.

If it's cutting out at 9% consistently then you just ride to that.

Gordon

 

[flash]

Bike brands dont specify the total usable amount of battery capacity, they only specify the total capacity. I always think they should do that by law. As an example Car brands MUST specify the usable amount. your 9% “sweetspot“ seems ok. i had a bike with the Brose system which shutdown at 20%.

My Landrover diesel certainly doesn't. There's at least 7 litres in the tank at zero km range.

Gordon

 

[Sapientiea]

If you used boost when the charge % is low then the power consumption will drop the voltage too much. I havent experienced your problem in our decoys to be honest in eco or trail.

 

[leftside]

If you used boost when the charge % is low then the power consumption will drop the voltage too much. I havent experienced your problem in our decoys to be honest in eco or trail.

So you can ride your bike/battery to 0%?

 

[Sapientiea]

So you can ride your bike/battery to 0%?

Never ran to 0%, lowest I got was 5% and it did not cut out, but I was in ECO-mid at the time. Will try near home sometime soon.

 

[leftside]

Never ran to 0%, lowest I got was 5% and it did not cut out, but I was in ECO-mid at the time. Will try near home sometime soon.

I was in eco when mine cut out at 9% - and wouldn't go back to eco.

 

[Sapientiea]

I was in eco when mine cut out at 9% - and wouldn't go back to eco.

Hmm you have the light setting on? Could be that the readout is not correct. It is always a bit iffy at the lowest percentages....Will investigate, would like to know.

 

[KenX]

Ran mine till it stopped last week, one bar showing, never flashing.............

 

[MattyB]

Lithium battery discharge is a very flat curve, so estimating remaining capacity accurately from voltage alone is very difficult to do accurately. Combine this with the legal requirement in some markets to be able to run the in built lights from the main pack (I believe Germany is one of those countries that requires that) and your 9% shutdown percentage starts to make sense.

 

[wildsau2]

My Landrover diesel certainly doesn't. There's at least 7 litres in the tank at zero km range.

Gordon

i am talking about eCars and eBikes. you are living in an old world maybe ?

 

[RocketMagnet]

I'd say the 9% has a quite large error margin on it and it has a safety margin built in to protect the battery as it needs power remaining for the battery control circuitry. So if it allowed you to run it totally flat then you store it for months without charging you could kill the battery. Less common with modern batteries especially when they are so big relative to phones etc. AFAIK it's actually a requirement of the battery standards in the EU to shut down and retain charge for the safety control circuitry and as said above you'll need even more for lights.

Basically with any device if the rechargeable battery runs flat don't try and repeatedly turn it back on as each power cycle until it auto shuts down eats into the safety charge area.