I have been measuring the voltage at the charge port. I didn't think of the lower terminals which are much easier to get the voltmeter leads on! I don't have the RAD charger available at the moment (currently at my office) so I ran the test using the Luna charger- I may repeat RAD charger later.

I charged to both 80% and later 100% and after letting the battery rest for 15 minutes, measured the voltage at each location with the key in each position. Here are the results..

80% charge, key in 'off' position:
Luna display=52.8V
Charge port=29.6V
Lower terminals=27.9V

80% charge, key in 'on' position:
Luna display=52.8V
Charge port=41.4V
Lower terminals=51.7V

100% charge, key in 'off' position:
Luna display=54.6V
Charge port=31.2V
Lower terminals=29.4V

100% charge, key in 'on' position:
Luna display 54.6V
Charge port=43.4V
Lower terminals=53.9V

Conclusion: In each case the voltage reading at the charge port is lower which I assume is causing the Luna charger to cycle on and off regardless of key position. I wonder if these voltages are typical, especially for folks who had success charging with the key in the 'on' position.

It does appear there is some other circuitry that causes the voltage to read lower than the actual battery voltage at each location (especially at the charge port).

The battery performance seems fine, but perhaps a load test would give more information. Maybe time to reach out to Luna.

Quote from: Altema on February 05, 2021, 04:28:10 PM

Quote from: galvitron on February 05, 2021, 03:49:36 PM

Quote from: Altema on January 06, 2021, 12:10:10 PM

Quote from: wkindred on January 04, 2021, 06:09:44 AM

Quote from: vudude on January 03, 2021, 01:42:39 AM
I think there is good reason to use this 80% charge method. The Luna 48v advanced charger just arrived. After setting for 80%, 2A the charger charged to about 87% according to the volts, then went into this oscillation turn off 3-4 sec., turn on 3-4 sec., turn off 3-4 sec., turn on 3-4 sec., ..., can anyone confirm this is normal?
Seemed kind of weird to me!  Thanks

yes, the off / on cycle at the end of the charge is doing the final balancing of the cells in the pack. quite normal...

That particular on/off cycle, with the Luna charger on the Rad battery, is because the BCM (battery control module) of the Rad battery does not give back an accurate voltage reading unless current is flowing into it. It's a protective design, and Luna Cycle tech support informed me that the Rad battery key switch needs to be in the "On" position. So that's what I do now, and the charger just stops charging when it's done and stays that way without cycling.

I'm having this issue with the charger cycling on/off after reaching 80% even with the battery key switch in the "On" position. I have a RadCity Step-Thru 3 purchased in Sept. 2020. The original controller went out and the support person said the corresponding control wasn't available and sent a different one that's compatible (referred to as 'Controller 2020 - City HS' in the order). The controller works fine for the bike, but I wonder if it's the reason the charger is cycling.

I assume the original Rad battery charger works fine, and the only issue is with the Luna Cycle charger. You can eliminate the controller affecting the Luna charger by removing the battery from the bike, turning the battery on, and trying the charger. If the charger operates normally, then the controller may indeed be the cause. If the Luna charger is still acting up, I would contact Luna Cycle and make it clear it does it with the battery turned on.

Yes, the original Rad charger works fine. I tried charging to 80% with the battery removed and the Luna charger still cycles on and off with the voltage on the Luna display going from 52.8 V to 36.5 V. So the controller is off the hook. Measuring the battery directly with a voltmeter reads 41.7 V. The 52.8 V value must be correct because the bike display shows full bars, but why would the battery read the lower voltage even with the key in the 'on' position? Maybe it's a feature of the BMS? I'm hesitant to reach out to Luna because it seems like the Luna charger is working correctly, but keeps getting turned back on because of the lower (incorrect) voltage reading.

Quote from: Altema on January 06, 2021, 12:10:10 PM

Quote from: wkindred on January 04, 2021, 06:09:44 AM

Quote from: vudude on January 03, 2021, 01:42:39 AM
I think there is good reason to use this 80% charge method. The Luna 48v advanced charger just arrived. After setting for 80%, 2A the charger charged to about 87% according to the volts, then went into this oscillation turn off 3-4 sec., turn on 3-4 sec., turn off 3-4 sec., turn on 3-4 sec., ..., can anyone confirm this is normal?
Seemed kind of weird to me!  Thanks

yes, the off / on cycle at the end of the charge is doing the final balancing of the cells in the pack. quite normal...

That particular on/off cycle, with the Luna charger on the Rad battery, is because the BCM (battery control module) of the Rad battery does not give back an accurate voltage reading unless current is flowing into it. It's a protective design, and Luna Cycle tech support informed me that the Rad battery key switch needs to be in the "On" position. So that's what I do now, and the charger just stops charging when it's done and stays that way without cycling.

I'm having this issue with the charger cycling on/off after reaching 80% even with the battery key switch in the "On" position. I have a RadCity Step-Thru 3 purchased in Sept. 2020. The original controller went out and the support person said the corresponding control wasn't available and sent a different one that's compatible (referred to as 'Controller 2020 - City HS' in the order). The controller works fine for the bike, but I wonder if it's the reason the charger is cycling.