E-Bike Battery Guide

[TomD]

Here's another scenario. Let's say you need to use 80% battery for a long ride. What would be best?

1) Charge to 100% and run to 20%
2) Charge to 90% and run to 10%
3) Charge to 80% and run to 0%

I would typically opt for 1, as it gives you 20% margin for error if you need it. But perhaps 2 or 3 might be better (ignoring non-linearity of the 80%) if you know for sure you won't need more than 80%.

 

[FlatSix911]

Here's another scenario. Let's say you need to use 80% battery for a long ride. What would be best?

1) Charge to 100% and run to 20%
2) Charge to 90% and run to 10%
3) Charge to 80% and run to 0%

I would typically opt for 1, as it gives you 20% margin for error if you need it. But perhaps 2 or 3 might be better (ignoring non-linearity of the 80%) if you know for sure you won't need more than 80%.

I believe that this question has already been answered in some detail by Ravi on page one of this thread... see the link to the study and graph below.

TLDR... lower depth of discharge is significantly better.

BH has a battery diagnostic device that can tell you what's the SOH (state of health) and how many cycles are done. I recommend you do this if you think your battery is aging prematurely and your dealer should be able to get his hands on one. The problem is, degradation is not linear. Let's say your battery had 80% charge capacity left after 400 cycles and it will go exponentially down because of impedance build up. By 450 cycles, it may have only 50% SOH. The reason why everyone on the Tesla forum uses 80% or 90% charge limit
Effect of charging rate and overcharging on the capacity.

1. Cycle life testing and modeling of graphite/LiCoO2 cells under different state of charge ranges.
2. Incremental Capacity Analysis and Close-to-Equilibrium OCV Measurements to Quantify Capacity Fade in Commercial Rechargeable Lithium Batteries.

A detailed study reporting the effect of depth of discharge. Check this paper. Online state of health estimation on NMC cells based on predictive analytics.
To summarize: Don't keep your battery at 100% all the time, don't expose it to hot temperatures and enjoy your ride.

 

[Gionnirocket]

A better battery chart. IMO.

View attachment 61770

Splitting hairs... But is this chart based off of typical BMS Specs?
The white paper on the Samsung 18650-35E states the Discharge Cut-off Voltage 2.65V and the Charging Voltage 4.2V
So for a 13S pack I've been using 34.5v and 54.5v... rounded for an even 20v span

 

[Gionnirocket]

Hi @Alaskan , As a owner of 3 Bosch battery packs, I am yet to find a suitable, satiator-type charger for Bosch powerpacks. I have been using rough gestimates (stopping the charge when the 5th LED blinking) and my packs have sustained good amount of capacity even after 1.5 years. Until you or I find a better solution, that's what I am going to use.

@ebikemom , glad you found it useful. Pedego as a company is very responsive to any warranty claims but it is smart of you to be proactive and try to get max battery life out of your bikes. They have had their fair share of battery pack issues by using generic cells and battery design that resulted in a battery recall of 5000 packs.
https://www.cpsc.gov/Recalls/2015/pedego-recalls-electric-bicycle-batteries

Since then they have moved towards better designs and higher quality cells. I hope your dealer is a friendly one. Some dealers think you are being too anal about small details and they may not know the implications of charging to 100%. But, in the long run, your batteries will outlast other batteries on the field even after heavy use. But, I don't expect them to be experts at battery design. They still have this going.. https://www.pedegoelectricbikes.com/battery-details/#charge

View attachment 23885



You're right. That's a male XLR pin. @Mr. Coffee posted this image a while ago. You could get XT 60 to XLR-male pin connectors for a Luna charger.

View attachment 23886

You have already found the solution. Using a timer can be an inexpensive option but it does demand little bit of cognitive effort in terms of guessing the existing charge and time needed etc. Since you say you your use your bike quite a bit and you have 4 pedego bikes, it would be good to have a satiator and by default it comes with a male XLR plug. If you have the 48V, 15Ah battery then it would be a worthy investment for a household of 4 E-bikes because $300 amortized over 3-4 years for 4 batteries is quite cheap.

Thanks Ravi... Excellent post!
I don't know if you've seen my post on a dyi charge controller... But for the past few months this has been working very well for me and is a lot more accurate and less hassle than a timer.

$10 DIY Smart Charger Alternative / Ver. 2.0

I've been experimenting with an easier way to achieve a 70% - 90% charge or a storage charge for my battery other than just timing it and I came across an inexpensive solar charge controller that I thought I might be able to adapt. In the end I am able to achieve my goal, but it didn't end up...

electricbikereview.com

 

[FlatSix911]

Thanks Ravi... Excellent post! I don't know if you've seen my post on a dyi charge
controller... But for the past few months this has been working very well for me and is a lot more accurate and less hassle than a timer.

$10 DIY Smart Charger Alternative / Ver. 2.0

I've been experimenting with an easier way to achieve a 70% - 90% charge or a storage charge for my battery other than just timing it and I came across an inexpensive solar charge controller that I thought I might be able to adapt. In the end I am able to achieve my goal, but it didn't end up...

electricbikereview.com

Well done on the DIY charge controller... you should consider offering these to EBR members for a nice price!

 

[tomjasz]

I've been using 34.5v

That is stressing the pack to 0% charge. A big hair!

 

[Gionnirocket]

I concur and agree it's always best to factor in a hefty margin of safety
It was more a statement of accuracy.
I don't believe I've dropped bellow 45V

 

[Ravi Kempaiah]

Here's another scenario. Let's say you need to use 80% battery for a long ride. What would be best?

1) Charge to 100% and run to 20%
2) Charge to 90% and run to 10%
3) Charge to 80% and run to 0%

I would typically opt for 1, as it gives you 20% margin for error if you need it. But perhaps 2 or 3 might be better (ignoring non-linearity of the 80%) if you know for sure you won't need more than 80%.

I would not worry about it, Tom!
Let me be philosophical for a moment.
We all come with an expiry date and in 50-60 years from now, most of us on this forum will be dead ( you and me included and that's the natural law). The same applies to batteries.
Whether we use it or not, they slowly degrade. Recklessly using it will make it degrade much faster for sure. (Nissan Leaf owners know it better than most E-bikers)

The benefit you get by switching from scenario 1 to 2 is minimal. If you can avoid your battery sitting at 100% for days on end, you're good.
If I were you, I would charge it to 100% just before the ride and then ride down to 20%.

That's what I do. Most of the time, my bike sits at 50-60% range and 2 hours before my morning commute or evening rides, I charge all the way and ride.

If we are talking purely technical, 90% down to 10% would be better by a tiny margin.
Someone asked a very similar question Elon and he responded like this...

https://twitter.com/i/web/status/448466037441179649

https://twitter.com/i/web/status/1068745921079345152

 

[FlatSix911]

I would not worry about it, Tom!
Let me be philosophical for a moment.
We all come with an expiry date and in 50-60 years from now, most of us on this forum will be dead ( you and me included and that's the natural law). The same applies to batteries.
Whether we use it or not, they slowly degrade. Recklessly using it will make it degrade much faster for sure. (Nissan Leaf owners know it better than most E-bikers)

The benefit you get by switching from scenario 1 to 2 is minimal. If you can avoid your battery sitting at 100% for days on end, you're good.
If I were you, I would charge it to 100% just before the ride and then ride down to 20%.

That's what I do. Most of the time, my bike sits at 50-60% range and 2 hours before my morning commute or evening rides, I charge all the way and ride.

If we are talking purely technical, 90% down to 10% would be better by a tiny margin.
Someone asked a very similar question Elon and he responded like this...

https://twitter.com/i/web/status/448466037441179649

https://twitter.com/i/web/status/1068745921079345152

Good perspective on battery life... I keep it simple and follow Elon's advice for EVs and EBikes.

 

[Gionnirocket]

Well done on the DIY charge controller... you should consider offering these to EBR members for a nice price!

Thanks!
. . . but taking into account that there seems to be zero interest in this... coupled with the fact that there are so many different chargers, connectors and battery BMS's it would be hard for me to test before sending it out. That would make me uncomfortable possibly wasting people's time.
That said if anyone would like to try it... I'm more than happy to help.

Funny... I've also kept a large aquarium for years and have built my own wet/dry filter along with heat and pump controllers and I'm often told the same... That I should sell my little inventions. It sounds tempting at first, but then I realize that though I enjoy doing these things, doing them on any scale will become work.

 

[info4johng]

The DIY charge controller is slick but is it necessary to manage your battery voltage? I did a simple test on the Lectric XP charger/battery and found that it restores battery energy at a nearly linear rate of 2 volts per hour. So I use a $5 smart plug linked to my iphone and set the charging time based on the initial voltage and my target voltage. (say 44 v + 2 volts/hr *3.5 hrs = 51 volts). Seems to work well for me.

 

[Gionnirocket]

The DIY charge controller is slick but is it necessary to manage your battery voltage? I did a simple test on the Lectric XP charger/battery and found that it restores battery energy at a nearly linear rate of 2 volts per hour. So I use a $5 smart plug linked to my iphone and set the charging time based on the initial voltage and my target voltage. (say 44 v + 2 volts/hr *3.5 hrs = 51 volts). Seems to work well for me.

Hey John
I'm not sure what you are asking.
The controller monitors the voltage and will disconnect the charger from the battery at whatever voltage you set. It will also back this up with an optional maximum amount of time allowed to charge. So for instance if you wanted to charge to 51v... you set the Shut off voltage to 51v. If you also set the timer it will automatically disconnect at what ever time limit you set as well but never going above 51V.
I hope that makes sense.

 

[info4johng]

Gionnirocket

I love the idea of the controller and I understand how it works. You are very cleaver! All I was trying to say was that I have the Lectric XP charger "dialed in" and understand its performance now so that I feel comfortable charging on just time to achieve my target voltage. If the charger was not imparting energy to the battery at a near constant rate it would be a different story but, at least, for the XP, time charging seems to work well. I looked for your first name but could not find it but I am following you and Thomas now. Love the active symbol you selected next to your user name!

 

[Gionnirocket]

Great... I'm John as well.... Gionni being what my cousins call me.
And yes, Thomas is a great guy and has been a big help to me many times.
I also was using a timer prior to finding the controller an it's definitely a working solution.
But being that the controller was so inexpensive.. coupled with the fact that I like to tinker and build things.. I kept myself out of trouble for a day.
All said and done I'm happy with it and appreciate the granular voltage setting. But since this isn't slated for the next Mars lander, it's really not that important.

 

[johndcoffman]

Charging Question: I have a battery that accepts a 2.5 mm barrel connector for charging, and this same battery uses an XT60 connector for the discharge plug. Can I charge the battery through the discharge plug without any ill affects?

 

[tomjasz]

Charging Question: I have a battery that accepts a 2.5 mm barrel connector for charging, and this same battery uses an XT60 connector for the discharge plug. Can I charge the battery through the discharge plug without any ill affects?

NO! If needed get an adapter for the chargers connector to the 5.5 x 2.5mm input. XT60 to DC 5.5mm x 2.5mm are readily available if that’s your issue.

 

[johndcoffman]

NO! If needed get an adapter for the chargers connector to the 5.5 x 2.5mm input. XT60 to DC 5.5mm x 2.5mm are readily available if that’s your issue.

Thank you; I will solder an adapter.

 

[Two is Better than Four]

I understand that I shouldn't charge my battery regularly to 100%. If I do charge it to 100% I also understand that it shouldn't sit fully charged for very long. My question is, what would be considered that maximum amount of time a fully charged battery can sit at without long term degradation? Is a whole day at !00% bad? Two days? A few hours?
Thanks

 

[Ravi Kempaiah]

what would be considered that maximum amount of time a fully charged battery can sit at without long term degradation?

One or two instances won't degrade the battery severely but cumulative effects will add up over a year.
Reminds me of this saying " No snow flake ever thinks it is responsible for an avalanche" ....
Long term degradation involves several, repeated occurrences. You can keep your fully charged battery at 100% for a weekend and if it's good quality pack, it won't degrade much. But, if you do that 5-6 times a month, over a year that would be 50-60 occurrences and that would have a negative impact.

 

[Alaskan]

One or two instances won't degrade the battery severely but cumulative effects will add up over a year.
Reminds me of this saying " No snow flake ever thinks it is responsible for an avalanche" ....
Long term degradation involves several, repeated. You can keep your fully charged battery at 100% for a weekend and if it's good quality pack, it won't degrade much. But, if you do that 5-6 times a month, over a year that would be 50-60 occurrences and that would have a negative impact.

Ravi, My habit is to just bring the bike in and leave my battery rest so long as it is over 25% at the end of a ride. I then charge to 100% starting in the early morning before going out on a ride. This avoid my battery ever sitting above 80% for more than a couple of hours. Thus far, after putting up to two years and 6000 miles on one of them, it seems to be holding near the same charge as when new. Does this battery strategy seem okay to you or am I risking a significantly shorter battery life?