Battery Charger at Purchase

[pennybags]

Umm.. I don't quite understand the point you are trying to make.

Would be interesting to know how the "smarts are going to be moved into the battery", that basically means the constant current / constant voltage "charger" will be in the battery if its going to control SOC which is just the constant voltage held at the end of charge and the bulk charge current which is the max current at the beginning. This means the entire charger is in the bike as the charger rectifies mains from 120v AC to DC at SOC voltage using a switching power supply.

No, that is not correct.

You can set the BMS to limit charging to % of the SOC. Greatly simplifying it but the BMS "voltmeter" component essentially needs to know what series pack it is (14S / 13S etc) and then % SOC will work off of that. Check out

This is pretty sophisticated - and you can actually cut out charging over a certain amps as well - very very similar to the satiator. Cant create "profiles" but definitely a big step up from whatever most users have today. This is not a new idea, and doesnt equal to "entire charger is on the bike".

If you still have a external power brick thats going from mains to say 58.8v DC for 52v batteries then it wont work with any battery out there and then you need a secondary buck power supply in the bike to cut 58.8v down to whatever final SOC your looking for say 56.6v for 85% charge.

The BMS can pause charging the pack once the pack reaches a specific SOC. Not sure why this is confusing.



1. Most / All ebike batteries need DC current.
2. All ebike chargers convert AC to DC (for the most part)
3. Tesla chargers are DC chargers IIRC
4. Regardless of what charger you have, the SOC needs to be defined somewhere. If it is not defined, it is assumed to be 100%

I have a Satiator charger too - and it is a GREAT charger. However just because it can do something doesnt mean it will be used like that.

I dont know about you, but all my battery packs are 52V, and except for probably 2 times over the last 4 years or so, I have never had to program anything on it. It is great, no doubt, but for an average user the benefits of "programmable" part are minimal at best. Heck, I would go so far as to say most people with satiators have not even downloaded the program, or connected to the charger at all. You know why ? because it needs a separate programing cable that doesnt come standard with the charger.

I am not trying to underplay the importance of a good charger like the Satiator. WW is trying to cater to the 95% of the market that wants a simpler / easier to manage solution. They need dead simple mechanism to set the SOC% and forget. WW is not there yet. but atleast they are trying something. I am sure their batteries wil work with the Satiator - but if i am reading Pushkar's post clearly, then looks like you don't necessarily need to.

 

[jharrell]

The BMS can pause charging the pack once the pack reaches a specific SOC. Not sure why this is confusing.

BMS are protection devices, they will turn OFF or ON based on voltage or current. They will protect your battery from overcharging or over discharge. They have either relays or in the case of most bike solid state mosfet switches that are either on or off thats it.

A CC/CV charger can hold a current or a voltage and still be on, its uses typically mosfets but instead of just being on or off they are switched on and off extremely rapidly (1000s of times per second) in a PWM fashion to "chop" the power then the output is filtered back to smooth DC. In order to properly and fully charge a lithium pack you need to bring its current up to your max desired or safe charge current and hold until voltage rises to max desired charge voltage and hold until current tapers to near 0. A normal BMS cannot do this, it simply sees the voltage hitting set max voltage and cuts out or max current being hit and cuts out, then maybe resets after a time and would trip again instantly unless the issue is resolved.

Conceivably the mosfets in a BMS could be driven in PWM fashion and act as a buck power supply along with more extensive control and filtering and cooling due the heat generated by doing this (this is why chargers get hot). This would be a replication of what the DC power brick would be doing a second time so there would be more losses in efficiency. I don't know of any BMS doing this since its cheaper and easier to just do it in the original DC power supply. I would be interested to see one that does and what the advantage and extra cost would be.

 

[pennybags]

BMS are protection devices, they will turn OFF or ON based on voltage or current. They will protect your battery from overcharging or over discharge. They have either relays or in the case of most bike solid state mosfet switches that are either on or off thats it.

If you watch the video you will notice that this is more than the "typical BMS" That is why we are having this conversation.

A CC/CV charger can hold a current or a voltage and still be on, its uses typically mosfets but instead of just being on or off they are switched on and off extremely rapidly (1000s of times per second) in a PWM fashion to "chop" the power then the output is filtered back to smooth DC. In order to properly and fully charge a lithium pack you need to bring its current up to your max safe charge current and hold until voltage rises to max desired charge voltage and hold until current tapers to near 0. A normal BMS cannot do this, it simply sees the voltage hitting set max voltage and cuts out or max current being hit and cuts out, then maybe resets after a time and would trip again instantly unless the issue is resolved.

You have a better understanding than I do. All i am trying to say is what is mentioned on the video and the parameter setting. This appears to be more than a typical BMS so it is worth checking out if there are any additional issues.

Conceivably the mosfets in a BMS could be driven in PWM fashion and act as a buck power supply along with more extensive control and filtering and cooling due the heat generated by doing this (this is why chargers get hot). This would be a replication of what the DC power brick would be doing a second time so there would be more losses in efficiency. I don't know of any BMS doing this since its cheaper and easier to just do it in the original DC power supply. I would be interested to see one that does and what the advantage and extra cost would be.

I am pretty sure the logic is being repeated - it has to. However in terms of "loss of efficiency" - its not significant enough to matter for most people. Assuming 14 cents/kwh (avg cost in the US) with 1% loss in efficiency per charge cycle, with 600 cycle life time, that is $0.84 loss over 2-4 years! Even at 10% efficiency loss that number is ~$8.8 . That is equivalent to 3 gallons of gas worth of driving. People are doing that every week (if not every day).

 

[jharrell]

If you watch the video you will notice that this is more than the "typical BMS" That is why we are having this conversation.

Again that is no different than any typical "smart" BMS I have seen unless I missed something, he even says in the beginning of the video "the purpose of the BMS is to protect the battery from critical events" it also does passive cell balancing which is a different topic but important for proper charging. Most BMS's now days do balancing although there are new ones doing active balancing however they still need a good external CC/CV charger. Almost all modern ebikes have a "smart" BMS with high/low voltage high current cutout parameters programmed in along with passive balancers, the one in the video happens to have a bluetooth interface to see and program those parameters with your phone that is all, some skateboards and ebikes do that as well.

I am pretty sure the logic is being repeated - it has to. However in terms of "loss of efficiency" - its not significant enough to matter for most people.

True, but it also adds cost and weight and bulk to the bike so why do it? The advantage of not having to tell the charger you want an 85% charge vs 100%? doesn't seem worth it, I can just switch it on the charger.

I like the Grins flexibility and build quality but even a charger that just has a 80/90/100% switch is fine as well, just trying to find out what is meant by not needing this stuff in the charger and how thats going to work its somehow built into the bike. For me I would rather keep the bulky AC to DC system off the bike as a separate replaceable component that I can optionally carry with me as needed. I really see no advantage to splitting the rectification from voltage and current control and no one seems to be doing that even in the EV space but am open to possibilities.

 

[jharrell]

If you want to see and learn what a charger does with respect to current and voltage Grin has a great charger simulator (they also have a great motor simulator as well). Again no BMS I am aware of will do this.

Here is a 52v 85% charge profile at 5 amps: https://ebikes.ca/tools/charge-simulator.html?pct=85

 

[stw]

Yikes! There are more reasons to use a Satiator than different voltages...

The reason I'm ordering a Satiator is mainly for the ability to select/program an 80-85% charge level (for battery longevity) rather than have to watch the charger when it gets close to 80% and unplug.

The second reason may become useful if I decide to get a second battery for an upcoming conversion: The GMAC with Baserunner controller works with a range of batteries, if I understand it correctly, so I'm thinking I should have a charger that works with a range of batteries too(?).

The bit of video I saw on the Grin site suggests there are lots of e-builder reasons to have a customizable charger like the Satiator. I'm new to e-stuff and still learning. Maybe I'll get into it that much and be glad for the capabilities. Maybe I'll just be glad not to wait up at night looking for the 80% value on the charger.

 

[tomjasz]

I do have a couple of eBikes, kitted by me. I recently sold my BBSHD motors in favor of BBS02B motors. I also bought two MAC motors and use Grin controllers and CA3's. I have batteries I need to use or lose, so the ability to run a range of battery voltages is important to me. However, I bought my first Satiator when I only had 36V batteries. Those well-managed packs are now over 6 years old and still power a 250W motor with very little sag,

I am a Grin "fanboy" one reason being their software is available for iOS (MAC).