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Jul 29, 2020, 02:23 AM
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Is there any auto switch off LiPo chargers?


Got 2 Shimano Steps electric bikes with 36V Li.ion batteries packs in my family.

I've noticed that these Shimano Steps chargers EC-E6000 switches them self off completely
when battery pack is full. Obviously these chargers are intended / designed for unattended charge.

So far all those RC/hobby grade chargers I've experienced are not switching them self off
at full charge. You got to attend and disconnect manually as soon as the alarm sounds.

I charge attended but some times I'm busy and can't disconnect, a auto switch off charger would be handy!

Is there any hobby grade charger that got this feature? (can't find any).
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Jul 29, 2020, 09:08 AM
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All hobby grade LiPo chargers stop charging when the battery is full. They're still powered on, of course, but they're not charging. There's no need to quickly disconnect when the alarm sounds. No harm will come from leaving the charger powered on and the batteries connected after the charge is complete.

With that said, you shouldn't be charging LiPo batteries unattended in any case.
Jul 29, 2020, 10:49 AM
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Here is my take on batteries chargers in general:

1-All controllers are outside of battery pack so we have lightest weight to fly RC, for example.

2. BMS (Batteries Management System) in battery pack (in your case of scooter, I think), where the charger is just an AC to DC transformer. It is safer with a little of weight to moving around;

3. All controllers are in the batteries pack in the EV (Electric Vehicle), for example, the “charger” outside is just an extension cable that can “talk” to the actual charger inside the vehicle and cutoff the AC if needed. We call it EVSE (Electric Vehicle Supply equipment)

This is the reason 2/3 can be charged unattended.

Tai
Last edited by tai626; Jul 29, 2020 at 10:58 AM.
Jul 29, 2020, 11:18 AM
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Where a good proper charger costs thousands

a cheap PSU or DC-DC converter will do

controlled by a simple adjustable HVC cutoff

CC-only charging, can go a bit higher voltage than when holding a CV stage and get to the same SoC / cap utilization.

A bit lower than the vendor max charge spec being good for longevity, with sacrificing much range.

BMS or backup HVC protect the pack if the primary control fails.
Jul 29, 2020, 11:50 AM
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Panther6834's Avatar
Quote:
Originally Posted by lametec
All hobby grade LiPo chargers stop charging when the battery is full. They're still powered on, of course, but they're not charging. There's no need to quickly disconnect when the alarm sounds. No harm will come from leaving the charger powered on and the batteries connected after the charge is complete.

With that said, you shouldn't be charging LiPo batteries unattended in any case.
True...and NOT true...at the same time. It is true that hobby-grade battery chargers do automatically stop charging once capacity has been reached. And, it is true that "no ham will come".

However, there IS a need to disconnect the battery from the charger as soon as possible once charging is complete - power drain. Ever notice the difference between a 1S charging setup, and the charging setup of 2S, or higher? While power coming into the batteries is done through the primary battery connectors (XT60, EC5, Deans, etc), power is also departing the batteries through the balance connectors. Once charging is complete, the longer you leave the batteries plugged into the charger, the more power will be DRAINED from the batteries.

The fully-charged voltage of LiPo cells is 4.2V...a although, most chargers stop at 4.198V per cell, possibly for 'safety' reasons. When charging, the charger is, essentially, "pulling" power from individual cells, so as to keep them properly balanced. Once charging is complete, as long as the balance connector is still plugged into the charger, this will cause two things to happen - first, the battery will slowly drain, leaving it with a lower voltage; second, since the charger is, essentially, in "stand-by mode", it doesn't have the ability to regulate per-cell discharge, which can lead to the cells no longer being balanced.

I've purposely tested this, leaving select batteries in the charger for 15 minutes after charging was complete. The higher the pack's capacity, the less "problematic" this should be...but, conversely, for lower-capacity packs, this can leave you with considerably less power for your next run. When I tested this, a 5000mAh pack had individual cells ranging from 4.13 to 4.15V/cell (not too much of a loss). However, a much smaller 1300mAh pack had all individual cells below 4V/cell.

The moral of the story is, of you want maximum capacity, check your charger (while charging) often, and unplug (at least the balance connectors) after charging as soon as possible. If you're a basher/causal-user, you might not care about a little "lost" voltage...but, is you're a racer, EVERY mAh counts, and you can't afford to lose any power because you "forgot" to unplug your battery after charging.


~ More peace, love, laughter, & kindness would make the world a MUCH better place
Jul 29, 2020, 01:12 PM
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Sounds to me like you have a crappy and/or broken charger. A charger that drains a 1300mAh pack to under 4V/cell in 15 minutes after charging should be considered defective.

Normally the balance resistors are controlled by a transistor and only switched on by the charger when doing balancing. When in the "off condition" a modern transistor should have a leakage current of a couple uA at most. Even for a 150mAh 1S pack, that's negligible.
Jul 29, 2020, 01:23 PM
Frankenstein recycled packs
rampman's Avatar
Quote:
Originally Posted by John61CT
Where a good proper charger costs thousands

a cheap PSU or DC-DC converter will do

controlled by a simple adjustable HVC cutoff

CC-only charging, can go a bit higher voltage than when holding a CV stage and get to the same SoC / cap utilization.

A bit lower than the vendor max charge spec being good for longevity, with sacrificing much range.

BMS or backup HVC protect the pack if the primary control fails.
Anyone understand this? Sometimes trying to impress others works the other way Please, tame it down some

Quote:
Originally Posted by lametec
Sounds to me like you have a crappy and/or broken charger. A charger that drains a 1300mAh pack to under 4V/cell in 15 minutes after charging should be considered defective.

Normally the balance resistors are controlled by a transistor and only switched on by the charger when doing balancing. When in the "off condition" a modern transistor should have a leakage current of a couple uA at most. Even for a 150mAh 1S pack, that's negligible.
I agree and have never had a charger drain a pack when finished.

Rick
Jul 29, 2020, 01:38 PM
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Panther6834's Avatar
Quote:
Originally Posted by lametec
Sounds to me like you have a crappy and/or broken charger. A charger that drains a 1300mAh pack to under 4V/cell in 15 minutes after charging should be considered defective.

Normally the balance resistors are controlled by a transistor and only switched on by the charger when doing balancing. When in the "off condition" a modern transistor should have a leakage current of a couple uA at most. Even for a 150mAh 1S pack, that's negligible.
iChargers are anything but "crappy". It's not as if I was sitting there, waiting for charging to be complete, and then used a stopwatch to time an exact 15min time period. As I didn't actually time how long it sat there, it might have been longer than 15min. I estimated the times, based on estimating how long until fully charged, and then estimating 15min beyond that. As for discharging, I know that the iCharger discharges at closer to 3A. Sorry if my iCharger isn't "good enough" for you.


~ More peace, love, laughter, & kindness would make the world a MUCH better place
Last edited by Panther6834; Jul 29, 2020 at 01:48 PM.
Jul 29, 2020, 02:01 PM
Custom User Title
I stand by what I said.

Your response is a bit ironic considering your signature line.
Jul 29, 2020, 02:20 PM
Bombs away! Err...landing
Ira NZ's Avatar
Quote:
Originally Posted by Panther6834
iChargers are anything but "crappy". It's not as if I was sitting there, waiting for charging to be complete, and then used a stopwatch to time an exact 15min time period. As I didn't actually time how long it sat there, it might have been longer than 15min. I estimated the times, based on estimating how long until fully charged, and then estimating 15min beyond that. As for discharging, I know that the iCharger discharges at closer to 3A. Sorry if my iCharger isn't "good enough" for you.
Yeeeaaahhh...No.

If it's discharging your battery a significant amount over 15 minutes then something is wrong. I could see potentially some slight discharge if it's continuously monitoring the battery voltage, but that's more like days to be noticeable.

It's not good practice to leave the battery plugged in indefinitely after it finishes. But finish your lunch, coffee, rerun of Game of Thrones, whatever should be fine.
Jul 29, 2020, 02:58 PM
Proud to eat Kraut ;-)
Julez's Avatar
I'm using iChargers for more than 10 years or so now, and they do NOT discharge a pack when it is left connected after the charge is finished. As a matter of fact, no other charger I ever came across does this either.
What can happen is that the voltage sags a little after the charge current is stopped, but that is just because the cell voltage is the sum of the galvanic element's voltage and the voltage drop across the cell's internal resistance due to the charge current. When the carge current stops, the voltage drop does no longer add to the cell voltage, so all you get is the galvanic voltage which is a tad lower. Quite noticable on LiFe Packs.
So, there's neither a need to disconnect packs quickly nor to switch the chargers off after they finish charging.
I would not want them to switch off on their own because I like to have a quick look at the charged in capacity and the individual cell voltages to make sure everything went right before I disconnect the pack.
Jul 29, 2020, 07:01 PM
Registered User
Quote:
Originally Posted by rampman
Anyone understand this? Sometimes trying to impress others works the other way Please, tame it down some



I agree and have never had a charger drain a pack when finished.

Rick
I have to admit that I do not understand any of it.
Jul 29, 2020, 07:15 PM
Registered User

My FMA Cellpro 4 Chargers have been left connected for months.


On 2300 ma 4 cell packs of LIFEPO4. No noticeable loss ever
Jul 30, 2020, 01:00 AM
Registered User
Thread OP
Quote:
Originally Posted by Panther6834
.
.
However, there IS a need to disconnect the battery from the charger as soon as possible once charging is complete - power drain.
.
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MESF: All B5/B6 copycat chargers who does not switch off "properly" will drain more or less, if not disconnected.

MESF = "My experience so far"
Jul 30, 2020, 01:16 AM
Registered User
Thread OP
Quote:
Originally Posted by Julez
.
.
What can happen is that the voltage sags a little after the charge current is stopped, but that is just because the cell voltage is the sum of the galvanic element's voltage and the voltage drop across the cell's internal resistance due to the charge current.
.
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Thanks Julez!

This might be the/an explanation for assuming power drain + self discharge.
Guess I need to try measure if there is a discharge current after the Charger has stopped charging.

Why I assumed this possible power drain is that the same thing has happened with my cellphones!
If they are left charging overnight the charge has usually not lasted long. Got a Cat S40 who may
last over 10 days with a good charge (disconnected after full charge)!!!

I've tweaked the phone Android OS (unistalled everything not needed that drains battery).


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