jobtraklite

I've been told that it is better to charge only to 90%, rather than fully charge (charger light turns green). Fully charging supposedly shortens the battery's lifetime. On the other hand most brands qualify their range estimates by saying "when fully charged". This implies to me that fully charged is normal; and charging less reduces the range.

So, what's the story.

How much does fully charging as a general practice reduce the battery lifetime?

How much does charging to 90% reduce the range?

If 90% is definitely the way to go, how do you tell when you've reached 90%. My charger only shows fully charges (green light) or not (red light).

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bike: Swagtron EB9

Battery: 36V

Motor: 250W rear hub

Rick_D

An EE might be able to answer, given enough technical info.

My not-an-EE SWAG is, "depends."

Battery type, build quality, protection scheme.
Charger design, including voltage and current, and whether it switches off automatically when charging is done.

When charging my bike's display gives time remaining to full charge, and the charger switches off when its done. Unplugged, the display can give charge % and I guess if I were to compare time left to the % display, I would learn the time remaining that equals 90% and could unplug it there. Confess I'm not committed to doing that and prefer to leave home with a full charge and max range.

A daily ride bike may indeed benefit from a charging strategy for maximizing battery health and life. Mine's a 2-3 day/week bike at most and I don't think there's much, if any difference. I'd be more concerned about a long stretch if disuse and not allowing it to completely discharge.

Curious what others think. I don't let my phone go past 85%, which is a setting that automatically stops charging there. I'm on year 5 and have never had a smartphone last more than 2.

veganbikes

On a machine like that it probably doesn't matter much the thing will likely not last long enough for battery health to be a huge concern or you will decide you like e-bikes and want to upgrade quickly.

In the end going to 80% generally promotes good battery health but charging conditions also make up a factor and if you are regularly using a bike and draining it to zero then maybe charging to 100% is better than a complete drain every time.

JGaerlan

I use a runaround to charge my batts to any percent I want. I use a laptop power supply with a xt60 connector. THis gets connected to a boost DC to DC controller. You can boost the 19V from the laptop power supply to any battery voltage I think as high as 60V. As the desired battery voltage gets closer, the amps going out to batt starts tapering off. Drawbacks, watts will depend on the laptop power supply and boost controller has a 400w Max)

jobtraklite

@ veganbikes

Thanks for replying.

The internet is full of negative comments about ebikes, especially those costing less than $4000. But that's fake news when it comes to Swagtron EB9's. I aught to know. Between my wife and I we own 3 of them: two in Illinois and one in Florida (we are snowbirds). In general they are fantastic for riding around town; and in particular the Florida one has over 2100 miles on it and the battery acts like new. If I were to upgrade, it would be only to get a longer range for touring. The EB9 got 24 miles when I tested it: flat bike path, moderate wind (went out and back so it should balance out to some extent), rider weight 175 lb., and only using pedal assist level one (strangely that is 15-16 mph on the EB9).

The bike that I inquired about is an Illinois one. The statement "maybe charging to 100% is better than a complete drain every time" seems to be an answer. But it doesn't apply to my case. I regularly use the bike - it is my only transportation. I tend to charge if fully just about every day; but I have NEVER drained it to zero.

late

There are devices you can buy that will limit the charge.

Not cheap.

2old

As you notice, some individuals think you have crap until you purchase what they recommend. The reports I've seen suggest that by charging to 90% you double the life of your battery and 80% doubles it again (when storing the battery; if you charge fully just before riding, it's probably negligible; BTW, it's more deleterious to store the battery at < 20%). Your battery management system probably shuts the battery down --- let's say at 10%; therefore by charging to 90% you lose about 10% of your "gas tank"; someone might start carping about the linearity of the voltage system, so the numbers might not be exact.

jobtraklite

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@ Rick_D

Thanks for replying.

I'm not sure what "My not-an-EE SWAG is" means, unless it refers to that old expression "subjective wild a.. guess".

Battery type: lithion Ion
build quality: very good if you are referring to the bike
protection: probably none if you are referring to battery certification.
Charger: 42 Volts, 2.0 amps. Does not switch off when done; light turns from red to green.

The display must be pretty primative. It doesn't give time remaining to full charge or time or miles remaining before it dies. It does have 5 bars showing how much battery life is left (per the manual, whatever it means). Perhaps when it shows 4 bars, that means it just changed to 80% charged. So a little more would be 90%. Since I never let it go empty, I can't very well prorate time to %full.

My bike is a 7 day/week, 2-3 times per day bike; it's my only transportation. So your "charging strategy for maximizing battery health and life" might be the right answer.

jobtraklite

@ Mr. 2Old

Thank you for replying. Did you steal my handle; I'm 82.

I think I addressed your first sentence in my reply to Mr. Veganbikes.

"charging to 90% you double the life of your battery" is quite a statement. Would you have a link to the source.

When you say "if you charge fully just before riding, it's probably negligible", what is "it", the increase in battery life.

The comment about storing the battery doesn't address my current post; but it gets at another question I have. I'm a snow bird, 7 months in Yankee-land and 5 months in Dixie. We have 4 ebikes, one for me and one for my wife and one for each in both places. Since we take the train back and forth, we leave the bikes behind when we move. So if I charge the bikes fully before we leave, how bad is the battery hurt by the time we return and charge them?

veganbikes

You are quite welcome!

Just FYI you want to put the (at) symbol and then immediately the posters name so it would look like (at)veganbikes but read veganbikes (it will come up with a menu to show the forum handles)

Glad your bike is currently working. A working bike is better than a non-working bike. Hopefully the will hold on for a while.

I have seen enough Swagtrons and similar bikes with issues and having working in one of the largest e-bike repair centers that would work on anything and had worked their for many many years I have seen a lot of stuff plus I have worked in the bike industry for a while so the non-electric components I know well. I know there are people here who have other anecdotal evidence that says the really low initial cost stuff works amazingly all the time and they will defend it to the death. However trying to build a decent hybrid will generally cost $700 and then a decent kit is going to be at least $1k and those are sort of closer to the bottom so trying to build a bike that is a $500 electric bike is going to be very tough without cutting a lot of corners.

You can find decent bikes for $2500 with plenty of good support. No they won't be as good as a 4k bike but will be a better supported machine with Bosch or Shimano or Brose.

In terms of the draining comment it was not necessarily directed at you but a statement of that would be better than going to 80 and then full drain. If you are not doing that then good, charge to 80%, and better health.

Doc_Wui

I worked as an EE/scientist. Now ab ebike hobbyist and retiree. I've read the data sheets on battery cells. I've looked up the studies that are available to read. Here a chart from one of them.

The top line shows that their cells never drop below 90% capacity when charged to 75%, The bottom line is a brutal 100%-25% charge cycle. It drops to 80% "fast". How fast? Like almost 4000 discharge cycles.

Meanwhile, if you do a full charge, run halfway down and recharge (100%-50%). you'll have 3000 cycles and still have 90% of your battery.,



That's about what I see in real life. I typically charge my batteries to 100%, run then down to half way, and then recharge. I've got ebike batteries from 2015-2017 that are still in service. The only time I don't charge to max is when I'm not expecting to use the battery immediately, Then I'll leave them sit,

I am not going to argue. It's clear that if you go easy on your gear, it least longer.

I'll also point out that the Swagtron EB9 appears to use a 36V6.4Ah battery. That is so tiny. I own a couple of packs in the same range. I get maybe 18-20 miles riding a light bike slow.. I used to carry them on long rides as emergency spares. Now if I charged then to 40V instead of 42V, I estimate a 10 mile range. The power relationship isn't linear.

Anyway, welcome to the ebike community. I've owned several ebikes that were under $700. Ridden as intended, at bicycle speeds with the advantage of motor assist, the brakes/shifters/tires were fine. Coasting downhill at a sustained 30 mph. Nope..

jobtraklite

If I understand the chart, the first % is the % you charge it to and the second is the % at which you recharge. If that is the case, I fit somewhere between the bottom bottom graph (top one in the legend at the bottom right of the chart) and the second from the bottom, 100-35% say. In that case I can expect the battery to drop to 80% of capacity after about 4000 charges. Let say I charge every 1 1/3 days on average. That's about 5330 days or 14.6 years.

In otherwords, it will drop to 80% when I'm 96 years old. I can live with that. Thank you for such a definitive answer.

Yes, but the motor is also tiny at 250W. I never amazes me how much power the EB9's have with all the talk about 750W motors. As I mentioned above, I got 24 miles out of a charge riding the light bike at 15-16MPH. The specs claim 28 MPH. If I had gone a little slower, I probably would have reached that.

2old

OP, AIR, what I learned was in batteryuniversity.com's site. By "it", I meant by charging to 100% just before you start using your battery, you probably do minimal damage to its life. I have a seven year old Haibike and the battery still functions well measured by the watt-hours used per mile.

Smaug1

Interesting chart in Post #11 by Doc Wui. One thing worth noting is that if a fellow does the "best case" 75-65% charge, it takes a LOT more charges to go the same miles than something more reasonable like 85-25.
I go for 80-20%, if I'm not planning a long ride. On any of my eBikes, that's enough for my typical around town usage, and it yields a good long battery life. I'd need to charge once a week, and for me, 5,000 cycles would mean 96 year battery life. It will certainly age out before that happens. *I* will age out too before that happens!

Maybe the more practical and simple approach is to just not leave it fully charged or discharged for too long. (more than a few days)

BTW, I'm an EE.

Roll On1

Charge it all with way when you're ready to ride! But, for storage, charge it 70 to 90%.