How to maximize Battery Life

[rpwbike]

Hi all.  Have ordered a Rad Commuter Bike for myself, and a Rad Step Thru Mini for my wife.  My bike should be arriving within the week.  So I have been watching videos, trying to learn how to care for my bike and maximize the enjoyment of riding it.
Several videos I have watched mention some interesting ways to maximize battery life and range. 

Maybe some of you have had experiences that can shed some light on these tips.

The most interesting tips I have seen regarding battery charging and extending its life (and the ones I am unsure about) are-

1) Don't charge your battery to 100%, but rather stop at 80% or so.

2) Don't charge your battery immediately after using/discharging it.  Wait an hour or so for the battery to 'rest/cool down', then charge it.

3) If you are going to store your battery for a few weeks or longer, don't store it at 100%, but rather 60%.

I welcome all constructive comments/experiences.

Other tips I have seen/read about Lithium Batteries-

Keep away from extreme temperatures.
Don't keep charging it once it reaches 100%.
Slow charging better than fast charging, as heat is minimized.
Don't allow your battery to get soaking wet or submerged in water.
Don't run the battery down to close to 0% before charging it.

[RadJohn]

When you get your Rad you'll find out that charging to 60% or 80% is not as easy as it is on a Tesla because the "brick" charger that Rad supplies only terminates at 100%, so if you want to try charging to lower voltages to get some extra battery life you'll have to rig up some PITA way to read charge voltage on your own, monitor it and manually terminate at the appropriate value (or buy something like a Luna Advanced 48V Charger or a Grin Cycle Satiator).

As for some of the other points, Rad still recommends periodic balance charging their OEM batteries for up to 12 hours, even though the Battery Management Systems (BMS) built into many other modern Ebike batteries make that unnecessary  (they balance on the fly).

As for not running the battery down close 0%,  phooey, how else am I going to find out if I can get 60 miles out of my Mini (55.5 is my best so far, to one bar flashing+). It's my bike and if I want to do that three or four times a year, I will, and I'm not going to let the possibility of a few extra months battery life stand in the way of having fun.

[rpwbike]

Thanks RadJohn!  Good info!  Agree with you, there will be times when I run the battery down to (close to) 0%.  That should not be a problem. 

Like you, I will be curious to see how many miles I can go before exhausting the battery.  And then I will attempt to beat that number!  LOL.

[DickB]

Deep discharge does also reduce battery life. batteryuniversity.com cautions against it.

Battery charge limits can be set by monitoring either voltage or current. I've monitored both while charging to get an idea of how the Rad charger operates. Of minor concern to me is that the charger continues to supply current at a low level even after the charge light turns green.  Voltage peaks at 53.8V. Current drops to only 20 mA but doesn't shut off after several hours - this may be in order to achieve the balance charge. If not balance charging, Rad recommends disconnecting the charger as soon as possible after the green light, but that is not always convenient.  I have asked Rad via email why they don't stop charging altogether; I have not yet gotten an answer.

I'm going to build a simple circuit to plug in between charger and battery to monitor current and automatically disconnect at a desired current, and give that a try.

[RadJohn]

Deep discharge does also reduce battery life. batteryuniversity.com cautions against it.

An occasional foray into the lower limits of what our batteries can provide isn't going to kill them because there are low voltage cutoffs in BOTH our batteries and our controllers.  When our Watt  display goes to 000, there is probably still somewhere around 39 or 40 volts left in the battery, which is ~3.00 to 3.08 volts per cell, which isn't particularly harmful if only done occasionally (<2.5 volts/cell is generally considered the lower limit to avoid more rapid/permanent damage to most Lithium Ion cell chemistries ).

Battery charge limits can be set by monitoring either voltage or current.

Almost ALL modern Lithium Ion battery chargers are CC>CV, meaning that they maintain a constant current (like the 2 Amps for the Rad OEM charger) until a target voltage is reached (typically 54.6V for a 13 serial cell, 48 volt nominal Lithium Ebike battery pack), then they hold that voltage and let current decrease, until either shutting off completely at ~<50mA or providing a low trickle charge current as observed with Rad chargers (again, a sign of a BMS that is behind the times).

For those wanting to understand what to expect from their Rad batteries:

A fully charged battery will be able provide up to 750 Watts of power in Assist Level 5, as observed on the LCD Display.

As power is consumed, the maximum available Wattage shown on the LCD display will decrease, with only ~700, then ~600, then ~500, then ~400, then ~300, then ~200 , then ~100, then ~50, then ~25 maximum Watts available in Assist Level 5 as the Battery Capacity  Bar count on the LCD display drops from 5, to 4, to 3, to 2, to 1, then 1 Flashing.

Keep going and the final single bar will start flashing. Assist Level 5 will quickly become more like 2, then 1 was on a full battery, and the Wattage readout will eventually go to 000 and you're done.

If you're pushing for maximum range using pedal power and Assist Level 1, the LCD Watts display will eventually also go to 000, but when it does, increasing to Assist Level 2 will bring back ~25 or so Watts until the the LCD Displays zeroes again, but bumping up to Assist Level 3 will bring back ~25 Watts again, and so on. This makes the end a little less surprising, if not as sudden.

Time to swap in a fresh battery for the trip home...

And FWIW, I do charge to 80% most of the time, but I have another battery that is a 17.5Ah, so at 80% it's 14Ah, which is the same as the Rad OEM battery at full charge (and it balances on the fly). I also make it a point to charge fully depleted batteries as soon as I get home, as it's best to not leave them sitting around in that state.     
   

[DickB]

I agree that the battery pack or controller likely has a low voltage cutoff to protect the batteries.

The low "trickle" current that I measured after several hours may be just powering the battery management system electronics in the pack, with no current actually going to the cells.  Hard to tell without taking the battery pack apart. (Which I may do someday. I'm that way - I like to see how things work.)

This article is informative:

https://www.powerelectronics.com/markets/mobile/article/21859861/proper-care-extends-liion-battery-life

It describes two methods for terminating Li-Ion charge.  I suspect that Rad is using something akin to the second:

"The second method is similar, but it requires monitoring the charge current. As the battery charges, the voltage rises, exactly as in the first method. When it reaches the programmed voltage limit, which is also called the float voltage, the charge current begins to drop. When it first begins to drop, the battery is about 50% to 60% charged. The float voltage continues to be applied until the charge current drops to a sufficiently low level (C/10 to C/20), at which time the battery is approximately 92% to 99% charged and the charge cycle ends."

I base this on my measurements out of the Rad charger on an early charge cycle:

Hours     V       A
     0    48.0  2.03
  1.5    49.0  1.77
  2.5    50.5  1.42
  5.0    52     0.80
12.0    53.8  0.20

Note that the voltage and current seen at the charger output/battery pack input is not necessarily what the batteries are seeing, as the pack may have intervening electronics. However, it's reasonable to assume that the bulk of the current is going to the batteries themselves. Monitoring the charger output current should give a good indication as to how fully charged the batteries become.

"A C/10 termination level will only bring the battery up to about 92% capacity, but there will be an increase in cycle life. A C/5 termination level can double the cycle life although the battery charge capacity drops even further to approximately 85%. A number of charger ICs provide either a C/10 (10% current threshold) or C/x (adjustable current threshold) charge termination mode."

While it is safe to charge Li-Ion cells at up to the C rate, the Rad charger charges at considerably less than the C rate. Perhaps that is to prevent overheating the batteries.  (The Luna charger also charges at less than the C rate, although higher at up to 5 A.) The C/10 rate for Rad is 1.4 A. C/5 is 2.8 A, actually higher than the Rad charger provides, so it appears that there's not a practical way to limit charge to 80 or 85%, as that level may be reached while the charger is still charging at 2 A.  I propose cutting off the charge when the current reaches C/10. That will extend battery life while still providing a decent charge level.

I will actually make the cut-off current adjustable, so that it could be shut off at say 1.7 A.  I will be experimenting with cutoff current versus battery full percentage to see if I can reliably charge to 80%, but of course it will take me some time to go through multiple charge/discharge cycles.  I do ride every day however.

[RadJohn]

All this C/x and voltage measurement stuff is far more complicated that it may initially seem, and is only serving to obscure a practical answer to the OPs original question. The last article cited, while containing no truly misleading information, was written in 2008, long before the Samsung 35E (or equivalent?) cells used in our Rad batteries were released (2015), and the Battery Management Systems (BMS modules) inside our battery packs reached their current level of sophistication. If one wants to design their own charger, bear in mind that our Rad batteries are 13 Series/4 PARALLEL packs, and that affects the C value (as in multiply by 4). Also, did you have your battery switch Off or On when taking voltage readings (it makes a difference)?

So, if an average Rad user wants to try get a little more life out of their battery pack without getting a math headache every time they think about charging it, and don't want to build a special contraption to charge to ~3.81 volt per cell termination overshoot voltage (to provide the Samsung specified 3.60 nominal "rested" voltage), only ride ~5 miles or less at no more than Assist Level 1, and keep it in the refrigerator between uses, then something like the Luna Advanced 48 Volt Charger is a proven commodity that's hard to beat (when it's available).

Here's the bottom line; Charging  to 80% at 2 or 3 Amps whenever possible is probably the best thing most typical users can do to add significantly to their Rad battery longevity IF most trips are short enough to not go below 2 Battery Capacity Bars showing on the Rad LCD Display. If you find yourself frequently ending up with 1 Bar showing, it would probably be safer to charge to 90% (the Luna Advanced charger will also do that) initially to try to reduce the number of times you end up at 1 bar. If you've already charged to 80% and decide to go on a longer trip, topping up to 100% JUST BEFORE THE TRIP will be less harmful to the battery than charging to 100% and letting it sit in a fully charged "just in case" state (100% charging has two negative aspects, just doing it, and leaving the battery in that state for significant periods of time, and the same applies to leaving batteries sitting around in a FULLY discharge state, avoid it). Charging to 100% in two time separated stages also reduces individual cell heating, another plus.

Here are some more factoids relevant to using a Luna Advanced 48 Volt Charger, in no particular order:

A Rad Battery pack charged to 80% will still show ALL 5 Battery Capacity  Bars on the Rad LCD Display, you just won't get as far before dropping to 4 Bars.

Always charge with the power switch on the Rad battery pack in the ON position, it WILL make a difference in charge termination profile & behavior (PARTICULARLY with current Luna Advanced chargers, at least as of early 2021). You can turn the Rad LCD display OFF, but if you don't, it should go off by itself after a while (at least until Rad fixes the PITA thing about losing your Trip Odometer count every time you stop to smell the roses, or something).

Like any other charger, ALWAYS plug a Luna into the AC wall/mains outlet FIRST, so the spark that comes from the surge associated with filling up the chargers capacitors will happen at the more robust power plug/wall socket where it will cause the least damage, rather than the wimpy 5.5 x 2.1 mm DC coaxial connectors on the charger/battery pack (which should be connected LAST and disconnected FIRST).

The Luna comes with an XT60 DC Male output connector (could be replaced with an anti-sparking XT90 if you like re-engineering things) so it needs an adapter with an XT60 Female to 5.5 x 2.1 mm Male Coaxial connector to fit the 5.5 x 2.1 mm Female (plastic) socket on the Rad Battery Pack. When shopping for 5.5 x 2.1 mm Male plugs to make your adapter (if Luna doesn't have them in stock at the time, a frequent occurrence) you may note that many of the listings on Ebay and Amazon say theirs are rated at 10 Amps, don't believe it, they're either lying or talking about Chinese Amps. Figure 4 Amps at best to be safe, (which makes the maximum 5 Amp charge rate of the Luna Advanced of questionable use, at least with our present batteries). I noticed the coax connectors getting warm with ALL my chargers, so attached is a thermal scan of the back end of a 5.5 x 2.1 mm coax connector plugged into my battery while being fed 4 Amps by my Luna. The plastic cover has been removed from the back of the plug to get a more accurate temperature measurement. 140.7°F is as high as I'm going to let things get, considering that the internal temperature at the actual connector contact junction(s) has to be even hotter than that. Limiting charge current to 3 Amps would be safer.   

Most current Rad full size Battery Packs have a 5 Amp fuse in the charging circuit, which should be OK for charging at up to 4 Amps (as long as you follow recommended practices/sequences to avoid connector plug in surges). Samsung says the normal charge rate for 35E Cells can be up to 1700 mA, which multiplied by 4 (because of the parallel circuitry use in our battery packs) would be OK for a 6.8 Amp charge rate. Samsung also specifies a  "Maximum Cycle Life" charge rate of 1020 mA for the 35E cells, which would be 4.08 Amps for the pack, which fits nicely with Lunas next to the highest switch selectable charge rate. I sometimes charge at 4 Amps just before going out the door after a last minute change of plans, and although it's nice to have that option, I'd limit the rate to 3 Amps with all but the best coaxial connectors (verified by actual thermal scans).

For those who hang up their bikes for longer periods of time during winter and want to store their batteries at the Samsung recommended life maximizing long term storage voltage of 3.6 volts per cell or 46.8 volts for the pack (resting voltage after at least 20 minutes, NOT charge termination voltage) Luna chargers don't offer and easy way to do that, but fortunately our bikes do, sort of. Just run the battery down a little past the point where 2 Bars show up and "stick" on the LCD Display and it should be fine. Avoid high storage temperatures, the colder the better as long as the battery pack doesn't get below ~0°F. When it's time to use it again, let it warm up to room temperature before charging/use (8 hours or so should be fine, no forced heating/condensation).

If you have a choice of parking your bike in the shade or in direct sunlight on a hot day, go for the shade.

Don't slip into a state of Analysis Paralysis! Treat your battery with the respect it deserves, but remember to have fun. I'm only planning on my Rad batteries lasting 5 or 6 years (even though I'm current using MANY individual 18650 Lithium Ion cells much older than that on a regular basis, I just don't charge/discharge them as often as I do my Rad batteries). If some of the things I enjoy doing end up shortening the lives of my battery packs by a few months, I could care less.

[DickB]

The OP didn't ask any questions, but asked for constructive comments and experiences. I'm offering mine. As well as a very practical solution.

Not everyone cares to buy and use an aftermarket charger. Rad warns against this. I suspect this may be because a user not knowledgeable could run into problems, such as charging at too high a rate and blowing a fuse. I'm not saying that there is anything wrong with using an aftermarket charger; I'm just relaying what Rad advises.  Many people will want to heed this advice.

My goal is to develop a simple-to-use add-on device to stop charging at less than 100%.  My device will have a power jack into which the charger will plug and a plug identical to the Rad plug to plug into the battery pack. It will also have a rotary knob to select charge percentage from 100% down to 80% or so.  To the Rad charger, the device will look like nothing more than a switch. There will be no alteration of the Rad charger nor any change in its operation.  It will be equivalent to simply unplugging the Rad charger at less than 100% charge.

To monitor actual battery voltage, one would need to plug into the power plug at the base of the Rad pack.  (The charge voltage at the Rad charger output is not the same as the battery voltage.) That adds unnecessary complication. It is perfectly legitimate to monitor charge current to determine battery charge capacity. In fact, it what Samsung specifies. Note that Samsung specifies cutoff at 3 hours or .02C, not at a particular voltage. Samsung specifies a CC-CV (constant voltage with limited current) charge, and that is exactly what the Rad charger does. Samsung further specifies that a "Standard Charge" means charging the cell with charge current of 1,700mA and constant voltage 4.2V at 23°C with a 0.02C(68mA) cut-off. For four cells in parallel and 13 cells in series this is 6.8A (as you stated), 54.6 volts, and 272 mA. For a non-standard charge to 80%, simply cut off the charge at greater than 272 mA. That is what I am doing.

I am an electrical engineer.  I have built and marketed several specialty electronic add-on devices for automotive use. I will likely market my cutoff device.  Just like the average Rad user need know nothing about C, CC-CV, current and voltage, the user of this device will also need not bother with all that. Just plug in the device and set the desired charge capacity. Simple and practical.

Rad instructs users to plug the charger into the battery charge port first, then plug the charger into a power outlet. This is correct. Any spark at the AC power plug will not be transferred to the battery. You'll notice that the Rad charger power and charge LEDs do not illuminate until a second or so after the AC power is connected, implying that the charger electronics are stabilized before any power is routed to the battery.  This is common practice in many consumer electronic devices such as audio amplifiers.

BTW I have measured no difference in charger output voltage or current regardless of the position of the key switch.

[twistydave]

Thank you for the info.  Waiting to the battery to rest after use is  new,   

[Jbcutler]

I have the Cycle Satiator charger. So if long term storage is ideally at 46.8 resting voltage. Any idea what the ending charging voltage would be? I'm guessing end of charging voltage is higher that resting voltage?

[Eric7]

I don't worry about it and resigned myself to buying another battery in 2-3 years whenever the range seems to fall off.  With 2 batteries, the bike should last 6 years at least? By then I'll have 2 used batteries that I can swap out on a long ride. Considering the value of my time, and the value of my enjoyment in draining the batteries for a longer ride and not having to cut a ride short, and not having to think about how to charge the batteries after every use, I think it is well worth it. 

I have a feeling that 6 years is about the life of the bike.  I'll reward myself then with a new bike after that.

Just sharing my views and maybe sharing another way to approach the problem - by not worrying about it and buying a second battery.

[Ishy]

Deep discharge does also reduce battery life. batteryuniversity.com cautions against it.

Battery charge limits can be set by monitoring either voltage or current. I've monitored both while charging to get an idea of how the Rad charger operates. Of minor concern to me is that the charger continues to supply current at a low level even after the charge light turns green.  Voltage peaks at 53.8V. Current drops to only 20 mA but doesn't shut off after several hours - this may be in order to achieve the balance charge. If not balance charging, Rad recommends disconnecting the charger as soon as possible after the green light, but that is not always convenient.  I have asked Rad via email why they don't stop charging altogether; I have not yet gotten an answer.

I'm going to build a simple circuit to plug in between charger and battery to monitor current and automatically disconnect at a desired current, and give that a try.

Reading further there are a number of lengthy and very informative posts on more technical specs. 

For a really crazy and simple solution to shutting off the charging after X amount of time. There's a Cheap and Easy option.

Possible Option#1 Pump Timers/Heat pad/Light timers for hydroponics Reptile Enclosures/Fish lights. *****Power consumption for charging may exceed safe limits for the these types of timers.   I'm not an expert so I don't know..  option#2 is a safer one but option #1 might be just as safe be sure to read the specs and don't exceed them****

Definitely Safe option#2.   Block Heater Timer for Cars.  If you don't know what a block Heater is... Well. It's mandatory in all vehicles sold in Canada since it warns up the cars engine block in winter.   This often is the difference between starting or not starting a car in winter.   Lots of power and a heavy duty switch mechanism.   I asked if it was possible to get a remote operated one... Yup. Not possible due to the power involved apparently 😅

Hopefully that's a quick Easy and cheap solution for the charging time shutoff issue some people may have.     

On the other hand.,..    complete Discharge of any litium ion battery is NOT. A good idea.   Lots of techy stuff but it causes irreparable damage to a component in the cells.   Even a small charge is better then none and any good BMS should prevent that... "Should". Being the key word there... But we all know techy stuff can mean glitchy stuff.

I hope this may be useful.   I read the other replies and no one mentioned using timers to stop the charging.    Lots of detailed techy info in volts amp hours etc etc.   
Learned a few things.
1.  What you plug in first.  Plug to wall or plug to device/battery is Important!
2.  Don't Store it Dead or Hot.
3.  It's hard to drain the battery on the bike without knowing it's going down.
4. Full battery= better/stronger/more power assist.
5.  Battery University... If I want to save money on expensive lithium ion batteries I better go visit.   At this point I want to earn a master's degree but I don't think they offer those😂.
6. There's something called battery balancing...  I think I need to know more... 🤔 Maybe?

Take care of your battery.  It's only a key component in what makes an ebike an ebike😅. Unless a couple hundred dollars in a few years is no biggie....  Maybe closer to 1k at this inflation rate🙈

[AJZin1952]

Smart Chargers
https://bafangusadirect.com/collections/all/products/48v-advanced-smart-quick-battery-charger#