The Rad battery pack is made up of batteries, Battery Management System (BMS) circuit board, key switch, charging port, power connector, and battery meter.
The Rad BMS uses a Sino Wealth SH367008 Li-Ion Battery Management chip. Sino Wealth is a Chinese integrated circuit manufacturer. The spec sheet for the chip is in Chinese, but Google Translate does a good job.
"SH36700X has built-in high-precision voltage detection circuit and delay circuit to monitor voltage, current and temperature to ensure the safety of the pack. At the same time, the series of chips also have Balance function to extend battery life."
The Rad battery pack has 13 groups of 4 cells each, with the 4 cells connected in parallel and the 13 groups connected in series. Because of the parallel connection, each group of 4 cells is essentially one cell with 4 times the capacity of an individual cell. Unless otherwise noted, further use of the term "cell" refers to a group of 4 parallel-connected cells. To the BMS, each group is in essence one cell.
The Rad chip uses a passive switching shunt resistor method for balancing. It does not use active balancing. Balancing is done during charging only.
Shunt resistors are switched in to equalize the voltage of each cell by dissipating the energy from higher-voltage cells down to the lowest cell voltage. Resistors are connected in parallel with each series-connected cell through semiconductor switches. The switches are controlled by the Sino Wealth chip.
The shunt resistors draw only a small amount of current and would be ineffective at high charge current. Balancing must take place at the end of the charge cycle. This is almost certainly after the Rad Charge light has turned green. To balance cells, Rad instructs that the charger be left on for 12 hours, long after the green Charge light. I have observed the charger continue to supply current to the battery pack after the green light illuminates. If an aftermarket charger cuts off current at charge complete, the pack may not be balanced.
The circuit board has semiconductor switches to disconnect the battery under both charge and discharge conditions as a whole pack. There is no provision to connect or disconnect individual cells or groups of cells. The pack is disconnected under charge overvoltage, discharge overvoltage, charge under voltage, discharge under voltage, short circuit, and high or low temperature.
With the key switch in the Off position, the semiconductor switches are off. Turning the key switch on "wakes up" the chip and the discharge switches are turned on presenting voltage to the battery power connector. As long as the key switch is on, the BMS is active and drawing current, albeit small, from the battery. The key switch does not disconnect power directly, but basically tells the chip to do so.
Construction of the battery pack is high quality. The mechanical construction is very good, with a plastic holder for the cells that is very well secured, as is the circuit board. Battery connections are direct to the circuit board with welded straps. Components and connections to the circuit board are all environmentally protected (think humidity) with conformal coating - the blue stuff that you see in the photo.
Nice info and thanks for sharing!
Thanks for the peak inside the Rad battery pack. Are the cells 18650? What is the branding on the cells? Thanks
Thanks @DickB! Good info!
Quote from: vudude on May 21, 2021, 09:45:33 PM
Thanks for the peak inside the Rad battery pack. Are the cells 18650? What is the branding on the cells? Thanks
The cells are 18650, which denotes only the size of the Li-Ion cell (18mm x 16 mm), much like the designation AA. None of the visible cells were oriented so as to show the manufacturer, but Rad says that they use Samsung 35E cells:
https://bit.ly/3iAetTr
I'm not 100% sure exactly when balancing takes place; more guessing based on observations and Rad instructions. I may intentionally unbalance a cell and take some measurements to learn more, but that will have to wait as I am a bit busy for a couple of weeks.
Here is a good reference on various Li-Ion balancing methods:
https://onlinelibrary.wiley.com/doi/full/10.1002/est2.203
I have seen comments about how the Rad charger is of lesser quality than some aftermarket chargers. Based on what I see in the Rad battery, I have to question that.
Here is a competitor's battery pack. The silver rectangle is the BMS. It is taped to the cells, and there are over a dozen wires connecting the BMS to the cells. Compare that to Rad's construction. You can't tell from my photos, but the Rad plastic battery holder is securely screwed to the base. Dense foam pieces are used to isolate and protect the circuit board from the top of the case. Electrical connectors, such as from circuit board to the LED meter, use locking connectors, but are also secured with tape (second photo is Rad).
Which would you say is of higher quality?
has anyone built and ran a 14s battery on their stock rad bike?
preferably radwagon 4 or built around the same time so compatibility conditions would be the same?
will the bike run ok or will it show an over voltage error of some sort?
Curious why you would want a higher-voltage battery.
Thanks for the detailed explainer Dick. Are you affiliated with Rad or is this just your inner nerd unable to help himself?
I've built a few 48V cell packs successfully from recycled and load tested laptop batteries for a Sun EZ recumbent I converted back in 2015. Your observations are spot on and much appreciated.
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.
Quote from: DickB on May 27, 2021, 04:56:54 AM
-- I ride every day and put on well over 4000 miles a year.
Offtopic, but it would be more than interesting to know how your Rad bike has survived doing such high mileage? Perhaps on some other topic here. I've done around 1500 miles on one year so far, all working still great.
I only have 400 miles on my Rad. I just got it a few weeks ago. Previous miles on a mountain bike.
This is an EXCELLENT article you have written. From one Nerd to another!
As suspected, the BMS is the likely culprit behind people's dead batteries when they leave them for extended periods of time(if the key switch is left in the on position).
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.
What would cause a good battery to drain while unused till it goes bad?
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!
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.
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.
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.
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.
Is this old style battery or the intergrated one ?
Quote from: Mori55 on November 12, 2021, 03:14:14 PM
Is this old style battery or the intergrated one ?
Rover 5.
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.
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.
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.
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?
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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?
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Yes.
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."
BTW since my first post I have identified the BMS chip in the Rad Standard battery and studied it's spec sheet, as well as reverse-engineered much of the BMS circuit, so I have learned more about how the BMS works.
Happy New Year, everybody!
I keep reading - from various sources - about battery maintenance and charging; some very specific recommendations about when, how often and how much to charge, etc. Sometimes there is a difference of opinion (though I trust the knowledge of people on this thread.) I am still waiting for somebody to tell me that none of it matters, that ebike batteries are designed to compensate for any charging "mistakes" owners make. My guess is that the majority of ebike riders out there just go out and ride and then leave the battery on the charger until it's full or even until they go out for the next ride. Or just charge it when it runs out.
My biggest question is why the advice about balancing the battery is not included in the owner manual, or even on a separate sheet of paper when you receive your bike. I happened to see it mentioned in the forum somewhere before I got my bike and then had to dig a little bit to find the instructions on the site.
Balancing information is included in the Owner's Manual. Which model Rad do you have?
Proper charging does matter if you want to get the most performance and longevity out of your battery. The thing is, many riders are using only a fraction of battery capacity, and won't notice a degradation in capacity. For example, I ride 12 miles a day PAS 1 -2, and use only about 15% of battery capacity. If improper charging reduces my battery capacity say 20% over six months or a year, I'll never notice it. If I take long rides at high PAS levels, I will notice a 20% reduction in capacity. It depends upon how one rides.
This is kind of a late reply , but may be helpful to someone eventually. First off, I've been into just about every nook and cranny of my RR1 and I've come to the conclusion that Radpower put a lot of thought into their designs. Yes , there are lower cost parts in places, but in those places, it makes sense . They absolutely put quality and safety in places where it matters most. The battery is a good example. It's not over engineered, but it's designed to not go up in smoke the first curb you hop off of. The cells used are the Samsung 35E as mentioned before. I know a lot of people want faster charging. This cell is one of the best on the market IF you charge it slow. It'll last 1000+ charge cycles in the right conditions. .2C is your best bet if you want it to last as long as possible. That's about 3 amps . The upper limit I would go would be 6amps . Some very thorough testing shows this battery will be "shot " quick if charging above .5C or 6.8 Amps.
How come I did not get a Samsung or Panasonic battery on my rad 6+ as they advertise on there website, instead I received a DLG battery, when I called rad they tried to tell me that was the container Co for the battery total BS! :'(
Quote from: Gizmo on January 30, 2022, 06:08:26 AM
How come I did not get a Samsung or Panasonic battery on my rad 6+ as they advertise on there website, instead I received a DLG battery, when I called rad they tried to tell me that was the container Co for the battery total BS! :'(
Have you opened it and looked at the individual cells? If they're the purplish-pink color they're most likely Samsung's . There's nothing outside the case that indicates which cells are inside that I'm aware of.
Companies buy the cells from Samsung and assemble their own packs. They're almost as never an indication on the external case of the battery pack. This method is industry standard.
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Hello Dick...I have a 2020 Rad Mini 4.....I can use the battery on peddle assist 1 and 2....I get near the house and use the throttle and the bike dies...The group has been very helpful and many are saying its the BMS....some times i can lift the battery out of the cradle and the display will go back on when i set it back down...I will roll into the garage after it dies and the Fluke says 52 volts....sometimes i roll in and it says 25 volts...The battery will go to 54 volts to 25 volts in a heartbeat...Is there anything i can do short of buying a new battery...I can get a reading of 25 volts put the charger on for 5 mins. and get a reading of 52 volts....researching the pros and cons of an aftermarket battery to save money is a chore...Thanks,Jeff
Quote from: flaco1801 on March 07, 2022, 05:30:16 PM
Hello Dick...I have a 2020 Rad Mini 4.....I can use the battery on peddle assist 1 and 2....I get near the house and use the throttle and the bike dies...The group has been very helpful and many are saying its the BMS....some times i can lift the battery out of the cradle and the display will go back on when i set it back down...I will roll into the garage after it dies and the Fluke says 52 volts....sometimes i roll in and it says 25 volts...The battery will go to 54 volts to 25 volts in a heartbeat...Is there anything i can do short of buying a new battery...I can get a reading of 25 volts put the charger on for 5 mins. and get a reading of 52 volts....researching the pros and cons of an aftermarket battery to save money is a chore...Thanks,Jeff
I can guess, but a few tests are in order to determine if it is bad cells, bad BMS, switch, connectors, or wiring.
I got a battery from another member and it was displaying similar symptoms. One of the cell groups was bad - low voltage. The bike would work for a few seconds, then shut down. The BMS was fine and doing its job - shutting down under low voltage conditions which were aggravated by high current draw.
On the other hand, a multimeter will read about 25 volts if the key switch is off. This is because a very small leakage current flows with the key switch off, and the resistance of the multimeter drops the voltage that it sees. If your key switch is intermittent, that could be the problem. Your 25V reading is a strong clue, so I would start there. I would bypass the key switch (one way is to unsolder the wires on the key switch and solder them together) and use the throttle. Or just try turning the switch off and on a few times when you see 25V.
Next I would test the cells.
To test the cell groups, open up the battery, connect a voltmeter across each opposite pair of terminals in turn as per the photos. You'll be making 13 connections and measurements. On the circuit board you will see B- or B0, B1, B2 etc. Test B0 - B1, then B1 - B2, etc. You should see the same voltage within a tenth of a volt on all cell groups.
Be careful. If you short out any pair of conductors to each other, bad things will happen - sparks, very high current, heat, melted conductors.
Since you have already taken the battery apart, in great detail. I'm curious to know: is there any slack space inside big enough to say hide an Artag in? Thanks!!
Yes.
Great post and thanks very much Dick.
About the YZPower charger that Dick cited earlier: Has anyone purchased this and did it work OK? I would like to have a fast charger with me for long rides when I need to give the battery a mid-ride charge. The 2A charger from Rad takes about 2 hours for each hour of riding and I would like to double that and get at least an hour of riding for an hour of charging. So I'm looking for experiences with the YZPower charger.
Thanks,