Inside the Rad battery and BMS

DickB · June 05, 2021, 03:17:23 PM

I don't think so.

With the key switch on and the display off, the controller is in "sleep" mode and drawing only 3 microamps from the battery - barely measurable. The BMS chip also has a "sleep" mode and also draws only a few microamps in that mode.

Jman · June 05, 2021, 10:17:53 PM

What would cause a good battery to drain while unused till it goes bad?

Altema · June 06, 2021, 07:48:29 AM

Quote from: DickB on May 27, 2021, 04:56:54 AM
I am not affiliated with Rad. I am an engineer and mostly just like to know how things work, so yes, I am a nerd. I do have an interest in maximizing battery life, as I ride every day and put on well over 4000 miles a year. And understanding more precisely what the State of Charge (SoC) is at any time. So knowing more about the BMS is helpful. I have also seen a lot of speculation on how the Rad BMS works, some of which is not correct, so I wanted to find out for myself more about it.

I found my long lost twin brother! 😂
Excellent article, and now I don't have to pull MINE apart! I have five batteries (only use one or two at a time though), and ride with a voltage/percent display attached to my Cycle Analyst. I've found that Rad components are conservative but very well made. I don't know if it's fair to compare the stock charger to aluminum cased aftermarket chargers, which are designed to look nice and be upgrades from stock units anyways.

One thing I really like about the Rad battery is that it charges fine with the battery switched off. All my non-Rad batteries require being turned on to charge, and I don't know how many times I've seen a Super73 owner cry "Oh no!" after realizing he had the battery turned off while trying to charge it during a rest break.

Thanks again for the post!

Altema · June 06, 2021, 07:59:48 AM

Quote from: DickB on May 26, 2021, 06:29:10 PM
Curious why you would want a higher-voltage battery.

There's little benefit if the rest of the bike is stock. You do get a 1.2 volt wider range from full charge to cutoff with a 52 volt battery, but your battery graph is not going to display correctly, and you can't adjust the low voltage cutoff point that the controller bases it's low power management programming on.

If you have the common 35 amp Bolton/EBW controller and display upgrade, then there is some benefit to it since Kv times voltage equals motor RPM, but it won't take you past the speed of the built-in RPM limiter on the Rad motor.

SoftwareTeacher · November 12, 2021, 04:45:34 AM

Dick:

I am unable to do electrical work. I am wondering if you know of a place that will check and repair the battery if needed. I am in South Florida.

DickB · November 12, 2021, 07:20:39 AM

I don't.

I have repaired a couple of batteries. One just had a bad electrical connection, one needed the power connector replaced. I'm in the process of working on a third, replacing a bad BMS with an aftermarket one. It appears the BMS suffered condensation damage.

I'm in lake Placid FL. Message me if you would like me to take a look at yours.

Ddaybc · November 12, 2021, 09:00:45 AM

This is an excellent thread. Thank you for posting it.
I especially like the referral to the cell balancing article as I'm a total novice to this kind of stuff but, like DickB and Altema, I like to know the how and why of how stuff works.
I've been following Rad since their start up and it's why I bought one of their bikes. Well made stuff for a reasonable price. Where I live bikes can start at $3000.00 but it's more common to see them listed for $4000.00 and higher. They use proprietary motors, parts etc. so you are stuck with them.

Mori55 · November 12, 2021, 03:14:14 PM

Is this old style battery or the intergrated one ?

DickB · November 13, 2021, 05:38:48 AM

Quote from: Mori55 on November 12, 2021, 03:14:14 PM
Is this old style battery or the intergrated one ?

Rover 5.

Sirch · November 16, 2021, 07:23:12 AM

Speaking of an aftermarket charger. What have you guys had luck with? I'm thinking of longer distance trips and I'd hate to have to sit and wait for Rad's 2amp charger to drip power back into the battery while I wait.

DickB · November 16, 2021, 08:28:28 AM

I don't have one, but if you don't want to spend a lot of money I would give this one a try. With a 5A fuse in the battery charge circuit I wouldn't go more than 4A. Make sure you check the polarity of the charge plug - I didn't see it listed. If looking at other chargers, be mindful of the float voltage. I've seen other 4A charges listed but with a higher float voltage, which I wouldn't recommend.

jaamskrad · November 24, 2021, 01:24:57 PM

Thanks for that description. I am charging my 2019 Rad mini batteries (2 bikes & 2 batteries each) with a Satiator charger which allows custom profiles for these batteries and generally charge to 80 or 90%. I know to charge to 100% periodically for the bms but was unaware it might require leaving the charger on for hours beyond the fully charged state to activate the battery balancing. I am thinking of using the Rad charger on each battery and leaving it on a couple extra hours...say, monthly? Any thoughts on that? Thanks.

Veggyhed · December 14, 2021, 08:11:42 AM

Quick question here. I read the post and I'm curious does the battery pack balance if the key is in the off position after the charger has reached charged and the green LED is on?

Sent from my Pixel 3a using Tapatalk

DickB · December 14, 2021, 08:52:58 AM

Quote from: Veggyhed on December 14, 2021, 08:11:42 AM
Quick question here. I read the post and I'm curious does the battery pack balance if the key is in the off position after the charger has reached charged and the green LED is on?

Sent from my Pixel 3a using Tapatalk

Yes.

DickB · December 14, 2021, 09:04:31 AM

Quote from: jaamskrad on November 24, 2021, 01:24:57 PM
Thanks for that description. I am charging my 2019 Rad mini batteries (2 bikes & 2 batteries each) with a Satiator charger which allows custom profiles for these batteries and generally charge to 80 or 90%. I know to charge to 100% periodically for the bms but was unaware it might require leaving the charger on for hours beyond the fully charged state to activate the battery balancing. I am thinking of using the Rad charger on each battery and leaving it on a couple extra hours...say, monthly? Any thoughts on that? Thanks.

You don't have to charge to 100% to enable balancing. The BMS chip balances based on cell voltage differences, not absolute cell voltage. If your charger limits charge % by using a lower float voltage, as long as you have some lesser current flowing at the end of the charge cycle, the BMS will balance the cells. From what I read about the Satiator charger, this is the case:

"Constant Voltage (CV): Once the terminals of the battery reach the full voltage for the charge profile, then the charger holds constant voltage while the resulting current into the pack tapers down towards 0 amps." (This will enable balancing in the Rad Standard battery.)

"Good quality programmable BMS circuits will usually attempt to balance the cells whenever they see more than a certain voltage spread between the highest and lowest cell in the group, and in that case there is no problem with partial charges. Similarly, good quality cells rarely drift out of balance in a series string, and can easily handle 100 or more cycles and maintain a perfect voltage matching even if the BMS circuit doesn't do any active balancing. But if you aren't sure of the makeup of your battery pack, then the protocol of occasionally giving a 100% top-up is a good bet to ensure both a long cycle life and evenly matched cell voltages."

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Inside the Rad battery and BMS