My mind is working over-time again, please help me out for me.

[mountainsport]

Hello to all,

When we think about the BATTERY MANAGEMENT SYSTEM we all feel extra protected, but at the same are we also being robbed by using it?

The reason why I am asking this question, is because whenever we purchase a purpose made electric bike or just the kit, theses days the batteries are supplied with a (BMS), which we all know of, right? (Hopefully). One of the safety functions of the BMS is to prevent the battery from being damaged, whereby the BMS is programmed to detect a very low voltage, (hope i'm right so far), then shuts down all power.

Now ,this is the puzzling part for me, I know that the battery can be set to any voltage ie ,24v, 36v ,48v , 72v and so on and lets say that you are using a 72v battery, when the BMS shuts down the battery, does it withhold about 10 floating unused volts give or take on the cells all combined?

If that is the case ladies and gents, are we all losing out here, so actually you and i have just bought a 62 volt battery for the price of a 72 volt. Another way of thinking about it, after 2-3 years of using the battery until no life is left in it, as in time for a replacement, will some voltage be left in the battery because of the BMS not allowing that remaining voltage left back never to be used due to safety. Should all battery manufactures take this in to consideration when pricing up their products, or shall we just take it as it is? Please tell me how it works so that I can get to sleep tonight also in this hot beautiful weather, and as beautiful as my loving Lynda.

MS. LONDON WILL BE IN THE THIRTIES NEXT WEEK XX.

 

[Alan Quay]

You have to remember that voltage is only the indicator of state of charge (SOC). In a 36v (nominal) system, the battery holds100% SOC at about 41-42 volts, and approaches 0% somewhere about 33v (that might be wrong number, someone please correct me if so.). The relationship is not linear however. It follows an S shaped curve.

The point is that volts is only part of the story. What you really want from your battery is power (watts) which is volts x current.

 

[oigoi]

The BMS doesn't actually deprive you of any of the battery's voltage. It simply monitors it. When it sees the battery voltage getting too low it disconnects the battery to prevent you discharging it too much and damaging it. BMS or no BMS the actual voltage you get from the battery to use is the same

 

[mountainsport]

You have to remember that voltage is only the indicator of state of charge (SOC). In a 36v (nominal) system, the battery holds100% SOC at about 41-42 volts, and approaches 0% somewhere about 33v (that might be wrong number, someone please correct me if so.). The relationship is not linear however. It follows an S shaped curve.

The point is that volts is only part of the story. What you really want from your battery is power (watts) which is volts x current.

Thanks for replying Mike, in other words all types of batteries from low to high powered batteries, when measured from new, when fully charged the SOC should be at between 41-42 volts. Therefore after one year of usage, that same battery when fully charged the SOC would be far more less, is that how it works?

MS.

 

[Jimod]

Thanks for replying Mike, in other words all types of batteries from low to high powered batteries, when measured from new, when fully charged the SOC should be at between 41-42 volts. Therefore after one year of usage, that same battery when fully charged the SOC would be far more less, is that how it works?

MS.

One of my batteries is now 2 years old, it doesn't show any less volts now than it did 2 years ago. You're not being cheated, just get out and play on your bike in the sun.

 

[amigafan2003]

BMS = Battery Murdering System

I've never run a BMS and I've never had a problem. I did have has a cell go bad but my regular monitoring routine caught it before it became an issue. A BMS would have actually disguised the issue for a while, potentially creating an bigger problem.

 

[flecc]

As other have said, you have the full voltage available and that scarcely declines over the life of the battery. What does decline is the ability of the battery to sustain that full voltage when under load, driving the bike. Eventually a point is reached when the battery cannot sustain the voltage under load for any useful period of time, or at all. The reason for that is the cells that make up the battery having exhausted their chemical content due to age and use.

The BMS primary function is preventing overcharging while balancing each of the cells to full charge during charging. Either the BMS or the e-bike's controller have the other necessary function of cutting the current supply when the voltage under load reaches a critical low point, below which could damage the cells. That low point for lithium batteries is generally about 76% of full charge, 31 volts on a peak 41 volt battery.

 

[Alan Quay]

Thanks for replying Mike, in other words all types of batteries from low to high powered batteries, when measured from new, when fully charged the SOC should be at between 41-42 volts. Therefore after one year of usage, that same battery when fully charged the SOC would be far more less, is that how it works?

MS.

A used battery might drop a little from the 41-42 volts when at 100% SOC, but not a lot. Really, the voltage indicates how full the battery is, not how much capacity it has. As the battery gets older, it will still be 100 full, but its capacity may be reduced.
Imagine a bucket that gets thinner. Same water level (volts), only less water (amp hours).

Hope that makes sense.

 

[mountainsport]

A used battery might drop a little from the 41-42 volts when at 100% SOC, but not a lot. Really, the voltage indicates how full the battery is, not how much capacity it has. As the battery gets older, it will still be 100 full, but its capacity may be reduced.
Imagine a bucket that gets thinner. Same water level (volts), only less water (amp hours).

Hope that makes sense.

Thanks, but I know there is more to it than that I need to learn.

MS.

 

[funkylyn]

Hello to all,

When we think about the BATTERY MANAGEMENT SYSTEM we all feel extra protected, but at the same are we also being robbed by using it?

The reason why I am asking this question, is because whenever we purchase a purpose made electric bike or just the kit, theses days the batteries are supplied with a (BMS), which we all know of, right? (Hopefully. One of the safety functions of the BMS is to prevent the battery from being damaged, whereby the BMS is programmed to detect a very low voltage, (hope i'm right so far), then shuts down all power.

Now ,this is the puzzling part for me, I know that the battery can be set to any voltage ie ,24v, 36v ,48v , 72v and so on and lets say that you are using a 72v battery, when the BMS shuts down the battery, does it withhold about 10 floating unused volts give or take on the cells all combined?

If that is the case ladies and gents, are we all losing out here, so actually you and i have just bought a 62 volt battery for the price of a 72 volt. Another way of thinking about it, after 2-3 years of using the battery until no life is left in it, as in time for a replacement, will some voltage be left in the battery because of the BMS not allowing that remaining voltage left back never to be used due to safety. Should all battery manufactures take this in to consideration when pricing up their products, or shall we just take it as it is? Please tell me how it works so that I can get to sleep tonight also in this hot beautiful weather, and as beautiful as my loving Lynda.

MS. LONDON WILL BE IN THE THIRTIES NEXT WEEK XX.

Well my dear MS....Ilminster has been in and above the 30's for at least a week.......too hot to cycle, plus Im too busy ( more about that later when its all finalised )....so I have been concentrating on consolidating my all over tan

Meanwhile I think your battery concerns have been answered satisfactorily so I will await your next brain overdrive question and hope that I understand it

Just in case you are interested I have just had a nice bowl of strawberries with low fat ice cream, and now I am about to bake a new orange and cream cake recipe, then have a cold shower, wash my hair and otherwise prepare for my bf's imminent arrival early in the morning.......so please dont have any more problems till after the weekend as i will be too busy to help you

Have a lovely weekend MS......et al .......cos I will.....

Lynda

 

[mountainsport]

Well my dear MS....Ilminster has been in and above the 30's for at least a week.......too hot to cycle, plus Im too busy ( more about that later when its all finalised )....so I have been concentrating on consolidating my all over tan

Meanwhile I think your battery concerns have been answered satisfactorily so I will await your next brain overdrive question and hope that I understand it

Just in case you are interested I have just had a nice bowl of strawberries with low fat ice cream, and now I am about to bake a new orange and cream cake recipe, then have a cold shower, wash my hair and otherwise prepare for my bf's imminent arrival early in the morning.......so please dont have any more problems till after the weekend as i will be too busy to help you

Have a lovely weekend MS......et al .......cos I will.....

Lynda

Lynda, have funnn!!!

MS

 

[mountainsport]

BMS = Battery Murdering System

I've never run a BMS and I've never had a problem. I did have has a cell go bad but my regular monitoring routine caught it before it became an issue. A BMS would have actually disguised the issue for a while, potentially creating an bigger problem.

Ok, that is something else to take into account.

MS

 

[103Alex1]

Ilminster has been in and above the 30's for at least a week.......too hot to cycle, so I have been concentrating on consolidating my all over tan

.... as you do I love cycling in this weather. Build up enough speed and with the warm wind it's the coolest thing to be doing (except taking a dip in the sea !)

 

[funkylyn]

.... as you do I love cycling in this weather. Build up enough speed and with the warm wind it's the coolest thing to be doing (except taking a dip in the sea !)

You are right of course, my excuse is that I have so much on at the moment (apart from clothes lol )
I get up early enough, usually 6am, and it would be the ideal time to cycle except its when I get all my work done whilst its cool.
By the time I could get out Im exhausted with the heat........

ok ok I can see thats pretty feeble for an excuse......Im going to try to do better....honest.....

Lynda

 

[mountainsport]

.... as you do I love cycling in this weather. Build up enough speed and with the warm wind it's the coolest thing to be doing (except taking a dip in the sea !)

Alex don't you like cold showers? I works wonders!!

MS.

 

[Scimitar]

Alex don't you like cold showers? I works wonders!!

I've no doubt you do.

 

[mountainsport]

I've no doubt you do.

Dave, how about mentioning that to Lynda too. By the way where is Lynda till now? I hope that she is being a nice lady by baking some tasty tarty cupcakes.

MS

 

[103Alex1]

Alex don't you like cold showers? I works wonders!!

MS.

Depends who I'm with !

 

[muckymits]

Dave, how about mentioning that to Lynda too. By the way where is Lynda till now? I hope that she is being a nice lady by baking some tasty tarty cupcakes.

MS

I think Lynda has her BF over, it wont be cup cakes shes cooking

 

[funkylyn]

I think Lynda has her BF over, it wont be cup cakes shes cooking

Honestly......cant a girl have any private life lol

I will have you know I baked him a lovely orange and fromage frais cake and scones with clotted cream which went down very well during.....interludes......

Lynda