How to charge bike battery to only 80% ?

Batteries, Chargers, and Battery Management Systems.
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spinningmagnets   100 GW

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Re: How to charge bike battery to only 80% ?

Post by spinningmagnets » Jul 21 2021 10:36am

Thanks for that information.

fatty   10 kW

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Re: How to charge bike battery to only 80% ?

Post by fatty » Jul 21 2021 10:54am

john61ct wrote:
Jul 21 2021 8:39am
Yes percentage of voltage is virtually useless.
High voltage is what ages cells, and percentage of voltage is used in the literature. Actual voltage limit as implemented by OEM is just an abstraction/application of percentage of voltage.
Percentage of voltage is perfectly fine, if not ideal to use, since it allows estimating cell cycle life using published data.
john61ct wrote:
Jul 21 2021 8:39am
Percentage of Ah/mAh is what should be targeted
No, because mAh does not age cells as much as high voltage. You are conflating capacity at voltage with aging at voltage -- not necessary.
john61ct wrote:
Jul 21 2021 8:39am
Just use voltages, HVC applies to charging, LVC to discharging, e.g. pack at rest an hour after charge termination should be under 4.10Vpc
and pack at rest an hour after use should be above 3.65V
As you indicate, capacity vs cell cycle life vs weight is up to the individual to balance, so rigid conservative guidelines like these only apply to you.

fatty   10 kW

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Re: How to charge bike battery to only 80% ?

Post by fatty » Jul 21 2021 10:59am

spinningmagnets wrote:
Jul 21 2021 7:54am
Tesla and Chevy have VERY expensive battery packs, and they charge to 4.05V
Can you share a reputable source for this? Would be great to save for future reference on similar topics.
TIA

eMark   1 kW

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Re: How to charge bike battery to only 80% ?

Post by eMark » Jul 21 2021 2:55pm

john61ct wrote:
Jul 21 2021 8:39am
Just use voltages, HVC applies to charging, LVC to discharging, e.g. pack at rest an hour after charge termination should be under 4.10Vpc and pack at rest an hour after use should be above 3.65V
Have found 3.65v after an hour rest more common than uncommon before again charging to 4.05v (85%). However, whether bounce back voltage is say 3.65v or 3.56v depends on the degree of load (raw performance vs cruising) when LVC was say at 3.40v ... when i'm sedately cruising the LVC bounce back voltage would be closer to 3.56v than 3.65v after both me and the battery rested for one hour :)
fatty wrote:
Jul 21 2021 10:54am
As you indicate, capacity vs cell cycle life vs weight is up to the individual to balance, so rigid conservative guidelines like these only apply to you (john).
Couldn't you say the same for docware's rigid cell tests? When talking about "capacity vs cell cycle life" isn't it OK to be as rigid as possible (minimize variables) when testing one cell vs say a LUNA 14s Shark pack (or 10s3p) with considerably more variables compared to the rigid demands required when comparative bench testing of one particular 18650 cell against another 18650 cell with each one having its own unique properties.

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Re: How to charge bike battery to only 80% ?

Post by fatty » Jul 21 2021 4:21pm

eMark wrote:
Jul 21 2021 2:55pm
Couldn't you say the same for docware's rigid cell tests? When talking about "capacity vs cell cycle life" isn't it OK to be as rigid as possible (minimize variables) when testing one cell vs say a LUNA 14s Shark pack (or 10s3p) with considerably more variables compared to the rigid demands required when comparative bench testing of one particular 18650 cell against another 18650 cell with each one having its own unique properties.
Docware's cell characterization tests are unrelated to john's blanket "3.65-4.10V" directive. It's not bad advice, but it's even more arbitrary than "only charge at 0.5C and discharge at 1C" is. It all depends on individual application.

Degradation is influenced as least as much by calendar time at high (90%) SOC and charge/discharge C-rate.

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Re: How to charge bike battery to only 80% ?

Post by john61ct » Jul 22 2021 3:20am


Trying to get every scrap of Ah capacity utilization means pushing closer to the mfg spec min/max voltages at both ends

greatly reducing longevity, possibly in a low C-rate context can mean getting 120 cycles rather than 1200 cycles before hitting EoL say 70% SoH.

But getting that 1200 may be sacrificing too much capacity for some, so maybe 400 or 800 is more appropriate.

Up to you, but don't just accept someone's over generalisation about what the right numbers are.

Any specific voltage (or other) numbers **I** give are simply working examples for illustration.

Each owner decides their own setpoints based on their use case, and measurements that vary from one rig to the next.

Having more knowledge about how to do so, helps define their priorities and preferences.




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ZeroEm   100 kW

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Re: How to charge bike battery to only 80% ?

Post by ZeroEm » Jul 22 2021 7:59pm

I watched my brother charge his batteries full and discharged them till they cut off, sometimes twice a day. Did not count but it was more like 300 cycles or around 6-7 months before the battery would give out. Watched him go thru 2 batteries. They were cheap but still around $600 for around a year's use.

I dream of my batteries lasting 6-10 yrs. 2 years behind me. Will keep everyone in formed.
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eMark   1 kW

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Re: How to charge bike battery to only 80% ?

Post by eMark » Jul 24 2021 10:16am

ZeroEm wrote:
Jul 22 2021 7:59pm
I watched my brother charge his batteries full and discharged them till they cut off, sometimes twice a day. Did not count but it was more like 300 cycles or around 6-7 months before the battery would give out.
IMO - that practice is partially a carryover from the RC Li-Po herd mentality. A prime example being Top Gun pylon racing pilots with their expensive carbon fiber planes like the Knife Racer Glass (100-150mph / $250), with its lighter weight Li-Po battery recipe of pure LiCoO4 instead of the mixture of LiCoO4 and LiMn2O4.

A LiCoO4 3700mAh 6s 22.2v 45C battery is $66 ... so it doesn't hurt quite as much to abuse and replace it as it does to abuse and replace an expensive Li-ion e-bike/e-trike battery.

Eventually, your brother should slow down as he ages. Maybe, not as much as you and i (15 to 20 mph), but the day should come (if it hasn't already) when he will welcome the more TLC challenge of cycle life longevity (3-5 years). :D
ZeroEm wrote:
Jul 22 2021 7:59pm
I dream of my batteries lasting 6-10 yrs. 2 years behind me. Will keep everyone in formed.
Enjoyed reading your other thread posts. Please do keep us informed :thumb:

john61ct   100 GW

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Re: How to charge bike battery to only 80% ?

Post by john61ct » Jul 24 2021 11:55am

Do not buy into vendor marketing about their "unique" chemistry formulation, 99% is BS and most get their slurry from the same dodgy suppliers.

Build quality and tight QA processes is what really makes the difference between pack value. And unfortunately nearly all sub prime makers lack consistency from one production run to the next.

Going on about LiCoO2 vs LiCoO4 for LCO, or LiMn2O4 vs Li2MnO3 on the LMO manganese side

And bringing up the RC LiPo world

is just masturbatory posing, irrelevant in the context of this thread.

The charge/discharge voltage profiles' impact on longevity has **very little** to do with the specific chemistry variant, or electrolyte / packaging

All the LI types quoted as 3.6 - 3.7V have the same care / voltage parameters,

balancing extended lifespan vs pushing (a little) more capacity utilization.


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Re: How to charge bike battery to only 80% ?

Post by eMark » Jul 24 2021 2:28pm

ZeroEm ignore ... "I Say, I SAY, I Say" ... and the foghorn rhetoric. He still can't make up his mind whether Samsung 30Q is "junk" as he once posted this year ... OR ... OK "for 99% of prospective [30Q] buyers".

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