E-Bike Battery Guide
- Thread starter Ravi Kempaiah
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- batteries charger recharging
CSH
Active Member
Hi Again Ravi !
I have another question........... My Giant App shows the Battery charge level (naturally),
But it also shows The Condition of the Battery (at this point 98%).
Can you tell me what all that means, and what insight it may or may not give me ?
Craig
TerryV6
Member
So, like any hobby, there can be much to learn. Initially, it is, buy the bike (insert much research here) and have fun. Then you find out about battery charging, maintenance and storage. I'm at that point and I've watch quite a few videos on this topic. I understand the idea of the ideal battery charge etc. I've also seen advice that says, hey, if you take care of it, charge it to 100% (not for storage of course) and you are fine. Your battery is good for at least 500 cycles and that is quite a few years riding.
We have two new Rad minis and just the chargers that came with the bikes. If I wanted to charge the battery to about 80%, how would I know what that would be? About 3 of 4 bars? Or, I've seen how to use your tester and check the level that way. My battery connectors, on the bottom, have no markings. How could I tell which is positive? Lastly, it is a 48v battery. What reading would I get when at 80% and 100%?
We have two new Rad minis and just the chargers that came with the bikes. If I wanted to charge the battery to about 80%, how would I know what that would be? About 3 of 4 bars? Or, I've seen how to use your tester and check the level that way. My battery connectors, on the bottom, have no markings. How could I tell which is positive? Lastly, it is a 48v battery. What reading would I get when at 80% and 100%?
tomjasz
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- Minnesnowta
Get plug in timer and multimeter, bars a guessing game. A multimeter is invaluable for a numbrr of trouble shooting chores. I have customers that spend an afternoon timing their charge and use the data to sent their timer and get within a volt of 80-90%.
CSH
Active Member
On My Giant Bike the App tells me more precisely what % Level I am currently at.
So I figured out a Formula to "Time" the % Needed.
(for my battery & charger)
It is as follows:
2.25 Minutes for every % of charge needed.
Example:
If Battery is currently at 32%
But I want it at 80%
Take 80% minus 32% and it Equals 48
48 X 2.25 minutes = 108 minutes
That is 1 hour & 48 minutes Charge Time
This formula gets me within just a couple percentage points every time....................
HOW AM I DOIN RAVI ?
So I figured out a Formula to "Time" the % Needed.
(for my battery & charger)
It is as follows:
2.25 Minutes for every % of charge needed.
Example:
If Battery is currently at 32%
But I want it at 80%
Take 80% minus 32% and it Equals 48
48 X 2.25 minutes = 108 minutes
That is 1 hour & 48 minutes Charge Time
This formula gets me within just a couple percentage points every time....................
HOW AM I DOIN RAVI ?
Ravi Kempaiah
Well-Known Member
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- Halifax
I really would not worry too much about charging just to 80%. 80% to 90% is a recommended figure.
If you look at the infograph here: https://electricbikereview.com/forums/threads/e-bike-battery-guide.24443/page-2#post-249851
You will infer that just by taking care of few simple things, you can enhance the performance. Normally, you would want to minimize the time spent at 100%.
So, I normally don't charge by batteries until it hits the last 20% and when the battery reaches the 85% or above, I simple disconnect the charger.
quickest way to do this is, on the back of your charger, it will have output voltage and current details, something like: 54.4 V , 4A - meaning, the charger pumps in electrons at 4A per hour.
In the case of Rad power bikes, it is 48v, 14Ah supplied with a 2A charger. The display has 5 bars, so each bar on the display is roughly 2.8A (not in reality! because the top end works differently)
For simplicity sake, when the last bar is blinking, you could disconnect your charger. I also know that Rad power battery uses generic BMS and hence the 1yr warranty, so you may want to charge 100% once in 30-40 days to ensure no cell group is out of balance.
smorgasbord
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- USA
Having owned a Tesla for 9 years now, I'm pretty familiar with lithium battery care, and have read my share of articles on the subject. My car still has its original battery, btw.
One aspect that needs to be defined is: What is a Cycle?
Tesla says:
Going back to the first post in this thread, does Grin define what they mean by a Cycle and what they define as "Useful Cycles" (aka Cycle Life)? I couldn't find these definitions, making their bar chart potentially misleading.
It appears many people quote Battery University's 2010 post on the subject of degradation, but, as this article points out, there are a few issues with BU's article, such as not incorporating starting SoC into its DoD chart. Starting at 100% and going to 50% has a different effect than starting at 50% and going to 0%, so a chart based solely on DoD is misleading. And there are data assertions without references in that article.
The definition of Cycle matters, too. For instance, this article claims: "100 cycles of 0.6 DOD does the same work as 150 cycles of 0.4 DOD." But, this is defining a cycle using the first bullet at the top of my post here. That's not the way others define cycle. As we see, Tesla is clear with its "full discharge-charge cycle" definition.
If Grin is using the top bullet definition, then its data needs to be adjusted to reflect the real work done. If going from 75% SoC to 50% yields a Cycle Life of X top-bullet-definition Cycles (for some definition of Cycle Life), and going from 80% to 30% yields a Cycle Life of 0.6X top-bullet-definition Cycles, then you actually got more miles out of the deeper discharge. 25% battery capacity * X is less than 50% battery capacity DoD * 0.6X (.25X < .30X). Or, as stated here: "At first glance, the 75-65 cycle seems to be the best for the battery, but you need to normalize it for work done: a 50% depth of discharge cycle does 5 times more work, 1000 cycles of 10% is 100 full cycles."
That last article has a table showing "Capacity per work done" and the results of that show that repeated 75%-65% use wears the battery out faster than repeated 100% to 25% use - at least when you look at the total miles you accumulated!
So, my questions on the definition of Cycle and Cycle Life being bandied about are not academic.
Of course, in practical terms, one needs to charge at least as much as one will use in the day's ride. But, rather than thinking that charging to 100% is just bad, we need to remember that it's not the charge to 100% that's bad as it is keeping the battery at 100% that's bad. This is repeated in scholarly articles dating from 2002, and mentioned numerous times elsewhere, including in this thread. Tesla, for its part, engages in active battery cooling when you do the full (aka Range) charge, trying to reduce the degradation effects from that full charge. Our eBike batteries do not have active cooling.
For my part, I try to charge in cooler environments. My normal procedure is to charge to 80% starting about an hour after my ride and then do a charge to 100% the morning of my next ride. If I know I'm leaving early for a ride, I'll charge to 90% the night before. This way I typically have close to 100% battery for my rides, so no range anxiety, but the battery hasn't sat at a 100% SoC for very long.
One aspect that needs to be defined is: What is a Cycle?
- Some articles appear to define a Cycle as "Any use followed by any charge back to the use start SoC." So, you could start at 80% SoC (State of Charge), ride down to 30% SoC, then charge back to 80% - and that would be 1 Cycle.
- Some articles appear to define a Cycle as "A full Depth of Discharge (DoD) followed by a full charge." With this definition, the above example (80% to 30%) results in only a half-cycle, so you would need two rides 80% to 30% to have used 1 Cycle. Tesla itself uses this definition.
Tesla says:
Going back to the first post in this thread, does Grin define what they mean by a Cycle and what they define as "Useful Cycles" (aka Cycle Life)? I couldn't find these definitions, making their bar chart potentially misleading.
It appears many people quote Battery University's 2010 post on the subject of degradation, but, as this article points out, there are a few issues with BU's article, such as not incorporating starting SoC into its DoD chart. Starting at 100% and going to 50% has a different effect than starting at 50% and going to 0%, so a chart based solely on DoD is misleading. And there are data assertions without references in that article.
The definition of Cycle matters, too. For instance, this article claims: "100 cycles of 0.6 DOD does the same work as 150 cycles of 0.4 DOD." But, this is defining a cycle using the first bullet at the top of my post here. That's not the way others define cycle. As we see, Tesla is clear with its "full discharge-charge cycle" definition.
If Grin is using the top bullet definition, then its data needs to be adjusted to reflect the real work done. If going from 75% SoC to 50% yields a Cycle Life of X top-bullet-definition Cycles (for some definition of Cycle Life), and going from 80% to 30% yields a Cycle Life of 0.6X top-bullet-definition Cycles, then you actually got more miles out of the deeper discharge. 25% battery capacity * X is less than 50% battery capacity DoD * 0.6X (.25X < .30X). Or, as stated here: "At first glance, the 75-65 cycle seems to be the best for the battery, but you need to normalize it for work done: a 50% depth of discharge cycle does 5 times more work, 1000 cycles of 10% is 100 full cycles."
That last article has a table showing "Capacity per work done" and the results of that show that repeated 75%-65% use wears the battery out faster than repeated 100% to 25% use - at least when you look at the total miles you accumulated!
So, my questions on the definition of Cycle and Cycle Life being bandied about are not academic.
Of course, in practical terms, one needs to charge at least as much as one will use in the day's ride. But, rather than thinking that charging to 100% is just bad, we need to remember that it's not the charge to 100% that's bad as it is keeping the battery at 100% that's bad. This is repeated in scholarly articles dating from 2002, and mentioned numerous times elsewhere, including in this thread. Tesla, for its part, engages in active battery cooling when you do the full (aka Range) charge, trying to reduce the degradation effects from that full charge. Our eBike batteries do not have active cooling.
For my part, I try to charge in cooler environments. My normal procedure is to charge to 80% starting about an hour after my ride and then do a charge to 100% the morning of my next ride. If I know I'm leaving early for a ride, I'll charge to 90% the night before. This way I typically have close to 100% battery for my rides, so no range anxiety, but the battery hasn't sat at a 100% SoC for very long.
bikerjohn
Well-Known Member
"Smorg", your perspective on the subject on SoC and DoD for prolonging the useful capacity of Li-ion batteries is very helpful! Thanks for sharing! One important key understanding from your note: Charging to 100% is not as bad as keeping or storing the battery at 100%!
bob armani
Well-Known Member
Great advice-I simply charge my battery while it is in my line of vision and once it reaches the 4th LED flashing, I charge an additional 15 mins. This puts the percentage at approx 82% every time. I then install it into my bike and get the readout from the interface. Seems like a very consistent method IMO.
Last edited:
Lightning P38
Active Member
I use my ipad timer to time how long the charger is running on my 36 volt battery. Then I have a reminder of when to stop charging to hit the 80% soc. I check the battery voltage before I start the charging to estimate how long to charge. I write down the times for various soc starting points, so I can just look at my chart to see how long to charge. Easy peasy.
tomjasz
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- Minnesnowta
Take Ravis' advice and do 100% charges for 6-8 hours to ensure the pack cells get balanced. I do it every 4-6 weeks. But I also admit I have two 2014 batteries that are usually charged to 100% and are from 2014. The sag is noticeable but we still get enough charge to run 15-20 miles.
Lightning P38
Active Member
I will do that on the first of the month during riding season. Thx.
bob armani
Well-Known Member
Thomas-Did you happen to start doing the 100% charges every 4-6 weeks since your battery was new? So this will extend the life cycle of charges and contribute greatly to the overall battery SOH is what I am getting here? I have only been following the 20%-80% rule with my battery since new for approx 1 year.
tomjasz
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Some better batteries have a BMS that balances a pack. Budget batteries typically do not. I have several that depend on occasional long charges to balance the pack.
FlatSix911
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- Silicon Valley
Thanks, good to know.
Can you comment on any specific brands that use a BMS in their batteries? Shimano, Bosch, or Yamaha
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tomjasz
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I believe those sellers have advanced batteries. It's budget battery resellers that cut corners. Several China sources will upgrade the battery BMS but we need to. ask for those features. Some of us are only interested in the bottom line and don't request upgrades. They cost more and price rather than quality seems to rule.
tomjasz
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The big three you mention are all top-quality builds.
After the recent attacks accusing me of trying to sell here, I'm hesitant to make public posts regarding my experience with 6 different battery sources. A poster claims I "allude" to what I represent and sell. Nothing farther from the truth. We sell what we sell and typically I try to not show bias. I do buy cells from an EU source that resells reject Bosch cells. All good cells that didn't meet their high standard and are sold by salvagers. Perfectly good brand name cells but for whatever reason Bosch rejected the packs. Typically for reasons unrelated to the cell quality.
FlatSix911
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- Silicon Valley
Thomas, don't worry about the baseless attacks of others... you have been a great source of impartial information on the EBR forums.
tomjasz
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- Minnesnowta
Those 2A charges are available for $10 with free shipping. But they work. I find 2A charge rates are best for battery longevity. And long charges where the BMS isn't capable of balancing a pack.
I strongly recommend owning a multimeter And confirming just how reliable those "LED indicators" ( a $1 item). For me I consider them Indicators, like a signal light on an automobile. I INDICATE I'm turning left but nothing stops me from turning right!
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