battery condition

Batteries, Chargers, and Battery Management Systems.
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Odessadream   1 mW

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battery condition

Post by Odessadream » May 25 2019 12:40pm

Probably this topic already has been beat to dead already. I am a biker who bikes short distances like 10 to 15 kms. The battery will not be even half way empty according to the display (3 of the 5 stipes are still on). When I arrive home I immediately hook the charger on the battery and as soon as I see that the green lite on the chargers comes on I disconnect the charger. Is this the right way to get the highest life time out of the battery or should I drain the battery further til say 15 - 20 % before charging it again ?

flat tire   1 MW

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Re: battery condition

Post by flat tire » May 25 2019 12:45pm

The best thing to do would be to leave the battery halfway empty all the time. Your constant full charging is the second worst thing besides running the battery down too far. You could try recharging when you reach maybe 20 or 25% capacity. Then disconnect when your cells have reached a resting voltage of 3.9v. Too high and too low voltages, too much heat, and trying to charge the battery when it's too hot or cold are the battery killers you may be wondering about here.

Of course if you have good EV chemistry (not high performance) the batteries are meant to be abused and fully charged / discharged and still get a few hundred cycles to 80%.

Cees   10 mW

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Re: battery condition

Post by Cees » May 25 2019 1:51pm

But leaving it always half charged you will not get the max power (speed and range) each time you go for a drive ?

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 25 2019 3:08pm

Leave it at low SoC as much as possible by default when not in use. Do not let it sit Full for a high percentage of its lifetime.

But never let it go even near dead flat.

As close as is convenient to when you need max range, charge all the way up and then use it.

Some (most) BMS need you to hold high voltage at end of charge cycle for a long time in order for them to finish balancing, IMO poor design but. . .

Your not drawing down too low is **great**, will extend bank life, likely more than the above.

docware   10 W

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Re: battery condition

Post by docware » May 25 2019 4:41pm

Balancing is practically unnecessary if you have new cells REALLY produced from LG, Samsung or Sanyo.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 25 2019 5:01pm

Until they start aging, lose some capacity.

Even the best units are not perfectly matched, and the extra money you need to pay for that may well not be worth it compared to the cost of design that lets you balance easily as needed.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 25 2019 5:02pm

Or of course some prefer to replace EoL at 80% capacity.

Good plan for safety.

Most users wait much longer.

docware   10 W

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Re: battery condition

Post by docware » May 25 2019 5:14pm

My battery 10s5p Sanyo GA is now 2 years old. Last year I started to charge to cca 40 – 41 V. So I am running this battery without balancing now for nearly 1 year. The cells are constantly within 3 mV range.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 25 2019 5:30pm

Is that a long run around here?

I've got LFP past seven years SoH still well above rating, prolly 1500+ cycles. Plan on leaving them to my grandkids.

Not high C-rates though.

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flippy   100 kW

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Re: battery condition

Post by flippy » May 25 2019 6:55pm

docware wrote:
May 25 2019 4:41pm
Balancing is practically unnecessary if you have new cells REALLY produced from LG, Samsung or Sanyo.
please dont say this, this is bad advice.
Lithium beats liquid dinosaurs.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 25 2019 7:15pm

A bit more qualified and it **can** be true.

I have seen many many LFP banks that have never needed re-balancing once commissioned properly.

But not in stressful high-SoC charging, high-C propulsion usage, down to way-low discharging.

In that context I'm sure regular balancing is a good idea, even when not "required."

Another critical qualification: At least regularly **monitoring** cell balance levels is required to see if balancing is needed.

Whether top or bottom, pick one and stick with it.

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Overclocker   10 kW

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Re: battery condition

Post by Overclocker » May 26 2019 12:00am

if you have high-quality matched cells w/ very good interconnects then balancing isn't usually needed for a very long time

but that doesn't mean you shouldn't be checking for imbalance frequently

docware   10 W

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Re: battery condition

Post by docware » May 26 2019 12:29am

Yes, regular checking of cells imbalance is in such case advisable, of course. And of course, BMS is still connected for emergency.

docware   10 W

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Re: battery condition

Post by docware » May 26 2019 1:13am

Odessadream, installation of simple cheap voltmeter can help you with remaining capacity reading (or state of charge – SOC). And you can better decide when to recharge again. Definitely not immediately after each ride. People here are giving you good advices regarding charging.
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I just recommend checking of the voltmeter with some multimeter.

Odessadream   1 mW

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Re: battery condition

Post by Odessadream » May 26 2019 11:29am

I read a lot of abbreviations like SoC, SoH, LFP what does that mean ?
BMS = battery managment system

Odessadream   1 mW

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Re: battery condition

Post by Odessadream » May 26 2019 11:37am

@docware I have the same bike display C965. I have my bike a short while now but the battery indicator never went below 3 dashes on the display. The display shows power but unfortanetly not the battery voltage. Where in the circut did you install the voltage indicator ? Or is there a more advance display than the C965 which gives the battery voltage ?

A

docware   10 W

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Re: battery condition

Post by docware » May 26 2019 1:00pm

Yes, there is for example 850C display among others, but not sure if it is compatible with your bike.
850C.jpg
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Unfortunately 850C isn´t compatible with my bike. Therefore I installed this cheap chinese voltmeter. Very satisfied with the voltmeter, much better information how full battery is.
Wired to the battery connector in the bike frame through fuse. The voltmeter is usually 3 wire, power wire has to be connected through resistor to get cca 12 V.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 26 2019 2:36pm


Odessadream wrote:I read a lot of abbreviations like SoC, SoH, LFP what does that mean ?
State of Charge
State of Health, residual capacity
LiFePO4

And yes CS is customer service

george1948   1 µW

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Re: battery condition

Post by george1948 » May 30 2019 10:43am

Hello. i have installed a 36v battery 250w-350w to a 36v controller with 250w motor.When the battery isn't connected to the controller when i push the battery button the lights are opening but when i connect it to the controller it stop working. Please help me.

john61ct   100 kW

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Re: battery condition

Post by john61ct » May 30 2019 11:31am

Are you sure it is fully charged? and that it is holding that charge? Have you got a different 36V load you can use to test, even just 100W?

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