How to get the best from your battery

I've heard two different versions on how to get the best from the battery on our electric bikes.

 

One (that I actually read in the instruction manual) is that the first time I need to charge it (I only got the bike last Saturday and according to the range meter I only have 13 miles left in it) I should let the battery completely die then charge it up. This is because of battery memory and after that I should do the same thing every 6 months to help prolong the battery range/life.

 

The second is that it doesn't matter about this because they don't have memories so it's irrelevant whether I charge it when it's half used or fully used.

 

What's your views?

 

Paula

Running the battery right down has no affect on the battery to make it better or worse. Some bikes use a complete cycle to calibrate the range estimates that appear on your LCD, if you have that, but these range estimates are so arbitrary, that it's probably a waste of time and effort to do that. After a few rides, you soon figure out how far you can go.

I've heard two different versions on how to get the best from the battery on our electric bikes.

 

One (that I actually read in the instruction manual) is that the first time I need to charge it (I only got the bike last Saturday and according to the range meter I only have 13 miles left in it) I should let the battery completely die then charge it up. This is because of battery memory and after that I should do the same thing every 6 months to help prolong the battery range/life.

 

The second is that it doesn't matter about this because they don't have memories so it's irrelevant whether I charge it when it's half used or fully used.

 

What's your views?

 

Paula

 

The complete discharge was for a previous battery chemistry, it doesn't apply to Li-Ion. Maybe they didn't rewrite that part of the manual?

Most important is if you have to store the battery for any length of time (month+) without use that it should not be fully charged, and should certainly not be allowed to become empty. People seem to suggest the 50% to 80% range.

 

Also, don't generally let it stay on charge longer than it needs (depends on battery/charger, typically till the light goes green). Except that once in a while let it have an hour or two extra to help the battery rebalance (get all the cells equally charged and at equal voltage).

 

This is my recounting what others have said, not personal knowledge of how batteries really work. Someone might well correct me on detail.

Advice seems to be that if you aren't regularly using the bike, store it at 50% charge, if you are using it regularly turn off the charger once it's 100% and never ever charge when very cold.

 

I'll be keeping my bike (when I get or convert it) in a brick outbuilding which is mains electricity wired but unheated and I have no intention of popping out in the winter snow every half hour to check when the battery is full so I can turn off the charger. Equally I can't really be faffed with removing the battery and charging it in the house (where at least it's warm but I don't intend to stay up half the night so I can turn it off when it's fully charged). Indeed, if I end up getting a bike whose battery is built into the frame I wouldn't be able to take the bike into the house to charge it and certainly wouldn't want to have to take the bike to pieces to retrieve the battery from inside the frame every time it needed charging.

 

So my question is how much do "real world" charging conditions damage a battery? If I leave the charger on overnight until I next use the bike and charge up in the middle of winter whilst using the bike most days am I going to kill the battery in no time and invalidate the warranty?

I charge during the night and leave charger connected, I disconnect in the morning.

The charger has Red light (charge in progress) and green light (charge ended) it as simple as that.

 

Charging out in the cold (freezing conditions) will reduce the charge capacity (wh), voltage will be unaffected. In use range will be affected as will voltage sag.

In use range will be affected as will voltage sag.

 

Here it is usually quite temperate so I had never experienced that until a "beast from the east" episode last winter - you can lose 33% (!) of capacity as I experienced.

Bosch range assistant shows (with other example settings) a range of 35 miles summer and 29 miles winter. As always lots of ifs and buts with their data, but the relative values are still informative of how they expect things to behave. The difference is presumably not down to things like wind and tyres which have their own separate setting. Some might be down to dress, but I expect the most part is down to different battery behaviour at different temperatures.

"Most important is if you have to store the battery for any length of time (month+) without use that it should not be fully charged, and should certainly not be allowed to become empty. People seem to suggest the 50% to 80% range."

 

Is this evidence-based or rumour based? Can anyone cite the data that support this recommendation?

Most lion cells if ordered via wholesalers/sellers come from the factory at a storage charge of approx. 3.5 - 3.7v, so manufacturers have likely tested them and the nominal voltage is best for longer term.

Taken from Bosch website....

 

 

 

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11 questions about the eBike battery

22.09.2016

The battery is the pedelec’s power source. It supplies the motor with the electrical energy that is required to provide power assistance when cycling. So it is hardly surprising that there is frequent discussion and “talking shop” about the eBike’s battery in particular. What is the difference between batteries? How far can you go on a fully charged battery? What do you have to remember about storage? Thomas Raica, head of technical customer application, here provides information and advice.

1. What is special about lithium-ion batteries?

Thomas Raica: Lithium-ion batteries are among the most up-to-date and common pedelec batteries around. Thanks to their high energy density they can store more energy and are relatively light in weight. We rely on lithium-ion technology for all of our Bosch eBike batteries – our PowerPacks. Bosch batteries weigh about two and a half kilograms and are among the lightest on the market. They also have the highest energy density.

2. How long does a battery last?

Thomas Raica: Lithium-ion batteries are not only light; they also have a long service life. Bosch PowerPacks are designed for many tours, distances and years of use. The smart electronic Bosch battery management system protects lithium-ion batteries from too high temperatures, overloading and deep discharging. A precise life span is impossible to forecast, however. The battery’s service life will depend mainly on the nature and duration of the stress to which it is subjected.

3. How can you influence the service life?

Thomas Raica: To get the longest service life out of a battery eBikers need only to follow a few simple rules in respect of protection, transport and storage. They include storing the battery in a dry environment and protecting it from direct sunlight at a room temperature of around 15° to 20°C. The ideal charging level for a battery is between 30% and 60%. Ideally, the battery should be recharged at room temperature. When transporting an eBike it is important to remove the battery from the bike and store it safely in the car.

4. How long does it take to charge a battery?

Thomas Raica: The charging time depends on the battery’s capacity. Using the standard charger the PowerPack 300 takes about an hour to half-charge, the PowerPack 400 about an hour and a half and the PowerPack 500 around two hours. A totally flat PowerPack 300 takes two and a half hours to fully recharge, a PowerPack 400 three and a half and a PowerPack 500 four and a half hours.

5. How far can you travel on one battery?

And which factors affect the battery’s range? Thomas Raica: For many eBikers these are crucial questions to which there are, however, no generally valid answers. The answer can differ enormously – from less than 20 to well over 100 kilometres on a full battery charge. Many different factors affect the range. They include the assistance level, cycling behaviour, air resistance, the cyclist’s weight, tyre pressure and, of course, the terrain. What are the ground conditions? Am I cycling on a paved road, a farm track or a forest trail? Does my route include ascents or consist solely of flat and open country? All of these factors influence the battery range. If you are planning a tour, a visit to www.bosch-ebike.com is highly recommended. The website includes a range assistant that takes the different factors into account and gives you an idea of how far you can expect to travel in the conditions that you specify.

6. What precautions should be taken in winter?

Thomas Raica: A general rule is that cold weather reduces battery performance. That is why, in winter at below-zero temperatures, it is advisable to wait until just before you set out before attaching to your eBike a battery that has been charged and stored at room temperature. If you have not used the eBike for quite a while – in winter, for example – the battery should be stored in an environment that is dry and cool at about 30% to 60% of its charge capacity.

Aren't e-bike chargers smart so they detect when fully charged & stop charging like laptop power supplies?

"Most important is if you have to store the battery for any length of time (month+) without use that it should not be fully charged, and should certainly not be allowed to become empty. People seem to suggest the 50% to 80% range."

 

Is this evidence-based or rumour based? Can anyone cite the data that support this recommendation?

From the rest of that post you quoted:

This is my recounting what others have said, not personal knowledge of how batteries really work. Someone might well correct me on detail.

Aren't e-bike chargers smart so they detect when fully charged & stop charging like laptop power supplies?

Yes.

Yes.

So the idea as expressed earlier in the thread that you need to switch off the charger as soon as the battery is fully charged is incorrect?

So the idea as expressed earlier in the thread that you need to switch off the charger as soon as the battery is fully charged is incorrect?

Yes, it is incorrect if you are using modern technology battery and charger technologies.

I wouldn't leave the charger switched on indefinitely , that would be pointless, but I'd be happy to leave it charging overnight for example.

Yes, it is incorrect is you are using modern technology battery and charger technologies.

I wouldn't leave the charger switched on indefinitely , that would be pointless, but I'd be happy to leave it charging overnight for example.

Yes, in fact I make sure to do this every now and again to ensure a well balanced pack. No need at all to do this all this time. And certainly not best practice either.

 

Just charge till full and occasionally leave it for overnight or for a extra few hours. That is it really for a battery that gets used fairly regularly

So the idea as expressed earlier in the thread that you need to switch off the charger as soon as the battery is fully charged is incorrect?

It's nothing to panic about, but you shouldn't leave it on for too long. Not many types of charger actually switch off. Most hold the voltage at maximum (42v for a 36v battery), which is not good for the battery if it stays like that for too long. Also, there are all sorts of safety concerns.

It's nothing to panic about, but you shouldn't leave it on for too long. Not many types of charger actually switch off. Most hold the voltage at maximum (42v for a 36v battery), which is not good for the battery if it stays like that for too long. Also, there are all sorts of safety concerns.

How long is too long & can you list some of the safety concerns please?

Aren't e-bike chargers smart so they detect when fully charged & stop charging like laptop power supplies?

 

No.

Ebike chargers charge or cease charging when the Battery BMS says so, If the BMS detects a fault or issue then it will prevent any power to flow.

How long is too long & can you list some of the safety concerns please?

It's not an absolute condition. It's a case of the longer the worse, but the badness is very small. If you leave it on for 24 hrs, it might do .01% damage. Over the years of too-long charging every time, it might reduce the life of your battery by 10%. It really is nothing to worry about, but just something to be aware of. The biggest danger is from your battery catching fire when something goes wrong with the charge control system, but the chance of that happening is also extremely small.

No.

Ebike chargers charge or cease charging when the Battery BMS says so, If the BMS detects a fault or issue then it will prevent any power to flow.

Are you saying it's the battery that has the smarts to prevent damage by overcharging not the charger?

Are you saying it's the battery that has the smarts to prevent damage by overcharging not the charger?

 

Both.

 

The charger detects that the SOC of the battery has reached 42v and turns the LED to green and stops sending current. If the battery drains to 41.xxv it will resume charging.

 

The BMS starts balancing the cell groups when the SOC reaches 41.5v and when the first parallel group reaches 4.2v it will stop receiving current.

Are you saying it's the battery that has the smarts to prevent damage by overcharging not the charger?

The BMS electronics (Battery Management System) inside the battery pack take care of charging the individual cells. When the BMS determines that no further charging is required the current drawn from the charger becomes very low, the charger detects this and goes into standby mode.

The BMS electronics (Battery Management System) inside the battery pack take care of charging the individual cells. When the BMS determines that no further charging is required the current drawn from the charger becomes very low, the charger detects this and goes into standby mode.

Thank you. Glad to have it confirmed that you don't need worry about taking the battery off charge once charging is complete as the charger & battery between them prevent any adverse outcome just as leaving my laptop connected to the charger makes no difference to battery life.