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Charging Strategy? Battery status inaccucies?


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Hi,

I have a Gotway MCM3 and I like it very much. Yesterday I went to work with it and there the battery (according to the app) was at about 40%. I charged (or thought I did, maybe I did something wrong). When I wanted to go home it said it was at 20%, which meant I couldn't ride it home. I went back charged for about 8min. To use it to go to the bus. It then said it was 60% full. At home, I charged it until the charger LED turned green. Then it said it was 80%. Later on, I connected it again and the LED was red for a while and then turned green. It still said 80%. I use the non-social gotway1.0 app.

Is there any accuracy in the state of charge indication when switching on?

Did you find a trick to check whether it is fully charged?

Do you have a means to charge fully?

Thanks!

 

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9 minutes ago, olkiluz said:

... It then said it was 60% full. At home, I charged it until the charger LED turned green. Then it said it was 80%. Later on, I connected it again and the LED was red for a while and then turned green. It still said 80%.

Seems like a problem with the charger, some connections or the battery.

9 minutes ago, olkiluz said:

I use the non-social gotway1.0 app.

Is there any accuracy in the state of charge indication when switching on?

Not too much :)

The charge indication of the wheels is based on voltage measurement. At http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge is stated that cells needs a rest of ~4 hours (after charge/discharge) so that this voltage method works accurately.

For 67,2V Gotways for example charge % are (?were?) calculated more or less as (taken from wheellog)

0% for Voltages below 52,9V

100% for Voltages above 65,8V

inbetween as charge_% = (Voltage - 52,9V)/13 * 100%

9 minutes ago, olkiluz said:

Did you find a trick to check whether it is fully charged?

Measure the voltage of the battery pack. Or if you trust the voltage measuring of the mainboard und the firmware take the voltage reported in the app. The nearer this voltage is to 67,2V (or 84V for 84V wheels) the fuller charged the battery is (after the abovementioned resting period).

You can use a chargedoctor to monitor the charged energy and voltage/current. ( http://hobby16.neowp.fr/2016/11/07/charge-doctor-v2-firmware-v-2-03-2/ from @hobby16 )

9 minutes ago, olkiluz said:

Do you have a means to charge fully?

Should be done from time to time so the cells in the battery pack have a (better) chance to balance.

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Also, the voltage tends to settle (go lower) after you pull the wheel off the charger. If you check it right after it comes off the charger it will be higher than if you check it a couple of hours later. To reduce stress on the battery I tend to charge my wheels to less than full using a Charge Doctor. If I know I want maximum range for a ride I will do a full charge just before leaving so the cells won't be sitting at full voltage for a long time. There are some good articles at Battery University about Li-Ion batteries:

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

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