BMS and controller for Li-po

[Dias]

Hello again guys, after hours of reading, googling and crawling internet Im here to get some tips again. Ive finally decided to give a chance to Li-Po. Ive found this (currently going for super-cheap 45€ in EU):

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=66309

My enclosed frame could easily store 4 of these packs (59.2V/16Ah). I want to get a 48V/1000W - rear hub DD (probably a Magic Pie, 72V would be too much for me I think). I want to be nice to these batteries and I would probably charge them to 3.92V (usually my trips will be 10km downhill and 10km uphill, so the ~60% capacity should be enough). 16x3.92V would reach 63V and Ive read that MP4 is able to handle 63V with its internal control unit. Is this correct? Or should I get another drive with external control unit (future upgrade possible). I could get 3 packs and run the 48V drive with just 44V battery, but I think this would make the bike too lazy.

About Lipo+BMS I was unable to found enough info. I would need a BMS for 1) balancing packs, 2) charging all the packs at once by connecting just 1 cable into my bike. I thought about installing a Lipo charger inside the bike but I would still need to charge them all at once.

Thanks

 

[Drunkskunk]

OK. Lots of problems here. Lets start with the obvious. You don't need rocket fuel to power a low power, low speed bike, and you really don't want the risks involved.

Under charging you packs so you have only 60% capacity is like throwing away 40% of your money. Most BMS won't balance the cells until they reach full voltage, so you wouldn't be able to use the BMS to charge the bike, so a single charger solution would be out. you would need to charge the cells individual with a charger designed to balance as it went.

Stripping the packs to their individual cells would allow you to make a 14S pack that you could charge fully, and use a conventional BMS to charge it with.
But it's still a bad idea to rely on a BMS for charging Lipo. You would need a way to monitor the cells your self before and while they charged. There is no situation where lipo can be made safe enough to charge unattended.

And you're still trying to run a psychotically unstable chemistry for a bike that has no need of it.

Since you are willing to throw away 60% of the battery, why not get a battery that you can use 100% of? a 52v 11.5Ah NMC battery would be stable, safe, less problematic, and have the same capacity as the 16S 16AH Lipo at 60%. After you figure the costs for the BMS, chargers, and monitoring equipment needed to make Lipo less suicidal, there isn't likely a huge difference in cost.

A sane battery plus a basic charger runs €408 / $450 http://lunacycle.com/batteries/pack...bike-pack-11-5-or-13-5ah-slim-line-rear-rack/
Shipping from the US for that specific pack might be high, but there are likely many EU sources.

 

[Dias]

Ah you again drunkskunk ..you have to be really patient to reply to my dumb post again. I already mentioned once in my other post - I have 55mm wide frame which can store batteries. I had serious trouble looking for affordable 18650 solution and I am not into point welding at all. I would like to order a custom pack, but again - in here its too expensive. I managed to find a good site (batterijservice.nl - NCR18650PF for 3.19€) which sells pre-welded parallel packs (almost for free). I could simply connect in series. I tried to order them but they told me that theyre not getting any 18650 batteries any soon cause of large companies buying all of 18650 cells. Nkon.nl only have INR18650-MG1 for 2.79€ with presoldered tags for 0.40€. I would still have to find a solution to place all of these batteries in 2-3 columns. Simply - Lipo is easier to get.

If you know about european battery seller which would sell 5P packs for a good price, please tell me

Anyways - Ive read about li cells (http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries) and if Im correct, using them at 3.92V would make them last approx 8 times longer for that 40% capacity loss. Ive seen a programmable charger for this but idk if there is a BMS that would work with the idea i had...

Back to thinking (or googling) about 18650 (their availability)

P.S.: http://lunacycle.com/batteries/packs/52v/52v-panasonic-ebike-pack-11-5-or-13-5ah-slim-line-rear-rack/ looks almost perfect, a little low Ah but if I could order it's guts themself it would be great (I know 60% lipo would be even less, but the lifetime would be 2x-3x better and cheaper)

 

[wesnewell]

What country do you live in?
https://endless-sphere.com/forums/viewtopic.php?f=3&t=66302
12s, 3 4s packs in series is fairly common for 48V systems and works really well with the 42V LVC of most 48V controllers. A bms for rc lipo needs to charge fully to balance the pack, so there's no way to only charge to 3.9V and get it balanced unless you use an rc charger. If you want to use 4 4s packs for 16s, then one thing you could do is use 4 battery medics and a 63V bulk charger, with the medics set for 3.9V. But unless you really need the little extra speed that would give you, 12s would be much easier to work with and still give you about a 45km range at ~35kph, with a top speed of ~45kph. Personally, all I've ever used is rc lipo on my ebikes for the last 5 years and would not use anything else. And I wouldn't even consider 18650's. I've been waiting 5 years for something better to come along that would produce the bang for the buck rc lipo has and there's still nothing that will. Here's a bms for up to 13s if you want to go that route.
https://bmsbattery.com/bmspcm/330-smart-bms-513-cells-in-series-bms-pcm.html#/212-discharge_current-20_40a
http://www.batterysupports.com/lion-lipo-nbsp-44v-nbsp-12s-c-32_42.html

 

[Dias]

Hello wesnewell and thanks for your reply. I am from Czech Republic - prices of batteries are ridiculous in here. I have no problem going with 12S build, I just thought the bike might be a little lazy. Everyone says go for 13s or possibly 14s. I wanted to use 3.92V because Ive read that lipo has very short lifetime in comparation to 18650 and I dont want to buy a new pack every year. Havent found any info about their real lifetime when used on low C rate with ebikes. Maybe you could tell me your experience with them? I live in an apartment so I would have to charge them inside - maybe I could get a temperature sensor with alarm to observe the pack.

Anyways the BMS from batterysupports looks like decent - there is no info on the other one. Well, I am about to order, cause Ive already spent like 50 hours+ reading stuff. Would this setup work? Or am I confused again hehe:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=66309 (3x)
http://www.batterysupports.com/44v-48v-504v-12s-30a-12x-36v-lithium-ion-lipolymer-battery-bms-p-268.html
http://www.batterysupports.com/432v-44v-504v-4a-lithium-ion-lipo-battery-charger-12s-12x-36v-p-167.html

 

[wesnewell]

That setup should work fine. I wouldn't worry about lifetime. I'm on my 4th year and ~25,000km with mine and I always charge to 4.2V per cell. But I never run them below ~3.7V per cell. Pulling 30A from a 160A rated pack should last a long time.

 

[Dias]

These numbers are pretty convincing. Thank you very much, gonna order this right now . I will post my ride when its finished - there are couple more problems I need to solve

 

[motomech]

I agree with wesenwell about using 12S lipo, I have been for years.
But I would use Battery Medics rather than a BMS.
After a ride I bulk charge to around 4.00V or so and let the BM's to balance and bring down the storage Voltage to 3.95V or 3.90V.
Then right before I go out, I charge them to 4.10V or so.
But my bulk charger is really fast and it only takes 10 or 15 minutes.
I'm on my second year with this group of Lipo and it's still strong.
Here is my set-up;
https://endless-sphere.com/forums/viewtopic.php?f=2&t=75672&p=1153668#p1153668

And I wouldn't put too much stock into the Battery University info. Lot's of mis-infomation there.

 

[Ykick]

12S is a very good RC Lipo eBike format. Running naked is not that big of deal if you’re prepared to watch and check cell voltages before every charge/discharge.

I’m fond of the CellLog 8M for quick, easy cell checks. You’ll wanna disable the “boot screen” to save time going from brick to brick.

Eventually, you may wish to upgrade to BMS and allow that to automatically manage bulk charged packs? But, it’s probably best to understand what the BMS is actually doing after you’ve been manually managing it for a while.

 

[Dias]

Thanks for response guys. I want things as safe and simple as possible and if you could tell me about better BMS/charger/any other protection, I wouldnt mind spending money for that. I thought this BMS can do all the stuff.

Considering Battery Medics/Cell log - I dont want to reconnect anything more than I really need to. I will use the bike every day, having to reconnect more than 1-2 wires would be annoying (not to mention I would have to open the frame every time). I just want to plug in the charger, let BMS charge cells equally, unplug and be ready to go. I wouldnt mind an integrated battery checker on that BMS - but Im not sure if something like this exists lol. If it could send 12S info via bluetooth it would be perfect .

 

[Ykick]

The good thing about cell checkers is that you don’t need to break down the main power lead series connections to use them.

Yeah, you may need to buy some JST extension harnesses to reach outside enclosures, bags, etc., but you can take cell readings with the pack ready to ride.

You can also do balancing but not in the traditional way with an RC Charger. What I sometimes do is charge 2A through balance wires for a low cell using a (1S) charge function.

You can also use wall wart, USB, power brick, etc. But only if you know what you’re doing.

Anyway, gotta start with a good cell checker and a way to reach the balance plugs. After a while you’ll begin to get the complete picture and better able to plan for and install a decent BMS protected system.

Forget about a BMS handling any significant balance functions though. Even if they have enough bleed balance current to do any meaningful balancing, (which they don’t) you don’t want all that heat packaged up sitting close to your cells anyway.

RC Lipo doesn’t normally need much balancing and if it does, there’s a problem cell and/or you’re pushing them too deep of discharge on a regular basis.

Best thing about BMS is that it will “let you know” there’s a problem before anything becomes too critical. I've been glad I had BMS a couple times over the years of daily operation. But still gotta troubleshoot and correct what’s going on before continuing to use the battery pack.

 

[Dias]

Ive just found Speedict Neptune Lite which sounds like what I need (except I wanted to use iPhone for this). There is a thread about it here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=73354&hilit=speedict+neptune

They mention model 3 which has GPS and speedmeter and will be able to monitor up to 15S cells voltage, temperature, balance cells and send info via wireless to an android phone. Sounds like all-in-one device that would satisfy my hunger for Magic Pie 5 with its integrated bluetooth controller. A simple controller would be enough if I used Neptune. What are your opinions about it?

 

[Ykick]

I don’t know anything about that Speedict deal. It “might” be cool/useful but seems to still be in development. IMO, much more work and unknowns’ than just doing like most of us have done. Which we’ve tried to explain to you.

If fancy is your thing I’ve tried one of these - http://www.flytron.com/icell/269-icell-battery-cell-monitor.html

Cool up to 8 channels, but one channel went out of calibration on my unit. It comes in handy for some situations (checking a suspected cell for excessive sag under eBike load) but it’s not a daily commute sort of thing.

Nowadays for most troubleshooting I merely use a logging CellLog 8S (not to be confused with the non-logging 8M) whenever I wanna see what a series string’s doing in a battery pack.

 

[Dias]

Not about being fancy, this box would be inside the frame anyways. I just think its very useful. ICell looks good, but its just a monitor without balancer and again - only 8S. Maybe I dont understand what you want to say, but Im pretty sure 8S battery monitor wont be able to monitor 12S setup :?. I ordered a battery medic from HK to learn using lipo, but Im definetly not gonna use it forever. Idk if there is a 48V charger compatible with both lipo/bms. At first I would need to charge 4S through JST-XH to 14,4V and after getting a BMS I would need a charger for 12S setup.

My future ride could look similar to this: http://novakola.cz/images/galerie/kolo-2015-18.jpg . I really really dont want to open the bike everytime for a monitoring procedure and rewire 12S to 8S/4S monitor/charger. Installing the pack and balancing it manually for the first time + once in a month is ok. Opening, charging and balancing it manually every single day would make me throw the bike out of the window soon. If there is a good BMS that would do everything I need (including monitoring info through BT/wifi and possibly a thermometer), Im gonna buy it for sure.

 

[Ykick]

In case I didn’t make myself clear, BMS balancing RC Lipo is lame at best, dangerous at worst. If RC Lipo needs balancing, something’s wrong. BMS is rarely the best way to balance RC Lipo anyway.

I’m not saying you must open things up (long leads tucked away can workaround) and I most certainly advise AGAINST reconfiguring series/parallel connections. That’s an accident waiting to happen. I suppose we just have a failure to communicate here?

But if you’re not willing to closely monitor RC Lipo eBike battery pack the wise thing is to consider another type of battery pack. Hobby Lipo isn’t anything to stuff inside an enclosure and forget all about. And it's definitely not something to rely on a BMS with only 80mA balance current to correct a wonky RC Lipo brick.

And I’m not recommending the iCell. I merely presented it as a wireless monitoring option that I've personally used before. If you wanted more than 8S, add a 2nd iCell device for up to 16S total. Waste of money IMO but since you brought up multi-channel BT monitoring...

I think I'm best done here. Good luck...

 

[motomech]

And to make the investment into caring for Lipo while stating that the intent is to change chemistries down the road make little sense. Start with what you want to end up with.
Add to that, the vibe we are getting is the OP doesn't want to spend the time to care for Lipo, I would say he needs a "plug and play" battery.
EM3ev and BMS Battery are good places to start looking.

BTW, The "Battery Medics" that I have recieved from Hobbyking didn't work. They are cheap clones that over-heat and the screen goes black.
The ones on Ebay are better, but the genuine Battery Medics are the best and I buy those from Hobby Stores like RC Progressive and Hobby Partz.

 

[Dias]

And to make the investment into caring for Lipo while stating that the intent is to change chemistries down the road make little sense.

You guys already convinced me lipo arent a bad way to go, so I dont mind investment and Im not thinking about going different way later.

EM3ev and BMS Battery are good places to start looking.

There a a lot of problems in getting batteries from China: 1) very long shipping times 2) taxes that will make the battery maybe even more expensive than if purchased here. Another problem is that European sellers are mostly out of stock of 18650 due to large companies buying all of them. Not to mention again that my frame is 55mm wide which is not sufficient to place 18650 in the manner 99% packs are made. Simply I already stopped thinking about Li-Ion and already ordered Lipo.

Hobby Lipo isn’t anything to stuff inside an enclosure and forget all about. And it's definitely not something to rely on a BMS with only 80mA balance current to correct a wonky RC Lipo brick.

I just need a simple solution to check batteries. When I want a device that would keep checking the pack all the time, you tell me Im going wrong way. Ok - I dont need BMS, but I need a monitor that I could use easily. Either during charging or during riding, I dont mind and I dont need fancy wireless stuff if there is a clean solution. I just considered a 12S wireless monitor useful cause I could sit in another room and see if there is nothing wrong during charging. And I wanted to be sure that cells are ok when I ride too, especially not to discharge them too much.

 

[Dias]

Anyways - I have found a charger you know for sure and might work: http://www.hobbypartz.com/75p-1220-charger.html

But I cant help myself and I still consider internal balancer/monitor much more comfortable way to go. If I used this charger I would still have to find a way to connect 3x4S balancing wires to the charger. I wouldnt mind if there would be a single wire solution for this. There are 2x 5mm wide holes for wires and if I could wire 3x4S balancing wires into 1 cable and had a 2x6S charger-to-1 cable...ahh screw this, this picture will say everything:

Unplugging the controller wont be a problem. But i still see a problem in balancing wires. Gonna crawl through HK and try to find a solution...

 

[wesnewell]

OK, if you want to use a 12s charger with 3 4s packs, you'll have to make an adapter as I did years ago. It's simply 3 4s plugs into 2 6s plugs. Here's how to wire it.

There's all kind of ways to safely charge rc lipo. This is just one. But if you don't have a 12s charger, then a bulk charger using a bms or battery medics is probably your best option.
You don't really need to monitor cell voltage while riding imo, just pack voltage. And that's just for a fuel gauge.

 

[Dias]

Thank you for wiring diagram, this I will need that for sure. But thats just one part...the other one is: how do I get wires out of the bike? I dont want cables (JST-XH) hanging out of my bike. I would like something like:

I just need to simplify the connector so I can easily plug and charge. Something like:

If I could charge and balance by just plugging charger to this connector, I could get a 12 balancing charger and use the bike without BMS with a simple monitoring device. I need to find a solution to pull this cable out of the bike to charge or make a waterproof gadget. Idk how everyone charges their enclosed frames. Havent thought about this before.

 

[Ykick]

You warned us....

 

[friendly1uk]

If your going to buy a 48v controller with display and wish the battery meter to work, your going to have to build a 48v pack. This is not 12s as is often said, as 12s is just 44v which will stop the meter working and limit your power for no real reason. 12s is the choice where a 36v controller is needed as they generally pop above 12s. If you do go ahead with 12s and a 48v contoller it's lvc won't let your cells drop below 3.5 which leaves a lot of charge unused. Remember these are 3.7 nominal, with half the charge available above 3.7 and half below. If you stop at 3.5 your still carrying a lot of battery your not using. While ensuring little of the cells life is spent half charged where it ages best.

Most BMS suppliers target 13s because 48v is a common industry standard. If you buy some old-skool design they generally won't balance till 4.2v per cell is reached, but if you buy a $20 programmable one you can have it set however you want.

I think a thread I did the other year is up your street. Search yginrut

 

[Dias]

Thanks for a tip friendly1uk. I think the disadvantage you mentioned about cells not discharging lower than 3.5V might turn into advantage in my case. I want to be nice to these batteries. I will have 16Ah pack for mostly 2x 12km runs with first 3-5km being downhill. I dont mind pedalling a little but I dont want to take a shower as the first thing when I get to work. But Ill try to get a programmable controller or get ready for the scenario when I would need an extra serie connected by purchasing 12/13S BMS.

Ykick: You made me read everything you wrote again. Im a little confused of your statements about BMS but I probably understand what you wanted to say all the time. Last try then I give up: I should get a BMS for daily operations and when a problem occurs balance the cells with an RC charger? If so I expect that RC charger is able to charge through "red and black" without balancing wires connected. I could use eg.: http://www.batteryspace.com/productimages/aa/20060523/PA010137.jpg attached to my frame?

Im sorry but english is not my native language as you probably noticed so I might not understand everything as it was meant.

 

[wesnewell]

Right, 42V is perfect for 12s rc lipo, which is at 0% soc at ~3.3V. 3.5V per cell will allow you to use 95% of the charge. You would only want it lower if you were using 18650 cells, which are at 0% soc from 2.7-2.9V depending on the make/model. At 3.7V, rc lipo is at ~10% soc. Nowhere near half charge.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

 

[motomech]

Lm sorry but english is not my native language as you probably noticed so I might not understand everything as it was meant.

It's not your english, but the fact you are telling us what is possible and not possible with Lipo. The difference is, we have been using it for years and you have NO experence!
Then you get way out there with crazy ideas like WiFI and charging though balance wires, etc. while you skip over understanding of the basics.
And when you say, you need a simple solution to charging Lipo, do you think we haven't working on this for years?
I suggest you start building your bike and keep studying Lipo in the mean time. Lord knows there if enough on this site to read.

Just one more time, here are some basic areas you need to consider.

1)Physical size of bricks in the space you want to use. The larger the bricks, the harder it is to fit capacity into a box of any shape. It is common to use Mock-ups of foam, a computer design app or in Flatland, paper cut-outs. Study the current thread "Show Us Your Home Made Battery Housings".
2) Yes, 12S, wesenwell is right, of course. It is the perfect Voltage for a 42V LVC. It's what I have been using for years and since I have 2WD with 2 batteries and can run one system down to LVC and get home on the other and I do this all the time. When I get home and ck the cel Voltages, most are between 3.5V and 3.6V, but sometimes a few start to "dive off the cliff", down to 3.2V or even 3.0V. If they don't go any lower, they will come back with normal charging. Any lower, special techniques are required and there is a chance the brick is ruined. I cannot emphesize the importance of a good LVC like 12S/42V
for peace of mind while riding on Lipo. Other than a Voltmeter(gas gauge), it really isn't necessary to monitor Lipo while you ride.
3)Chargers-The Thunder 1220 you linked to is no longer available. It has been "Out of Stock" for close to a year now. The only balance charger capable of doing 12S is the Thunder 1430C and it's close to $200 US, and it needs at least a 20V power supply.
You will need to use a bulk charger and the various Mean Wells(and clones) are the most common. The best Mean Well to use is the one linkled in my first post, the HLG. There are lesser, less expensive models, but most require some sort of modification. It's important that the power supply be of the "constant current" type. Since my controller provides the LVC, i don't need a BMS for that and I just use Battery Medics to balance and they work fine for me. You do not need to sit there and watch Lipo charge like watching water come to boil. You just need a system that will sense if a cel voltage gets too high and will shut down. That's why a CC charger is important. As it approaches end of charge voltage, it has already started to attenuate the current. HK offers a cel checker that has a high Voltage alarm for those who want extra security.
Search threads using key words Mean Wall, Bulk charging, etc.
4)Connectivity-You can add a single plug to that enclosure and there are threads here that show how to do it. I believe some use a DB-60 connector. But I would suggest that you try a different approach. That enclosure is accessed thru the flat side panel, no? Just use airplane style quick fasteners like the Duz. Some of us like to visaually ck the battery pack from time to time, ck'ing for any "puffing", loose wiring, etc.

I think this thread has run it's course and it's time to put it to bed.
You really need to do more reading and less writing.