2x 8S headway (=48V16Ah), 2x ?A BMS, 1or2 charger(s)?

[Quajochem]

Hi
I red alot about battery configurations, but I can't seem to figure out what BMS to use if I split my pack into 2 8s packs with each their own bms, wired in series.
Right now I have laying around a 16sBMS 60A continues current.

I want to be able to draw about 40amps cont. regardless if I put the packs in series or parallel.
And I want to be able to charge it with one 48V charger while wired in series. Or would it be much better to use 2 (isolated) 24V chargers?

And if I have 2 8s packs with BMSes, how much amps cont. would they need to be to not shut down if I draw around 40amps from the connected packs? Would 2x 20+A 8s BMS in theory be enough, or do they both need a 40+A 8s BMS?

I hope I made myself clear enough

 

[Ypedal]

ouf.. mass confusion going on here...

the BMS's max amps is only the higher limit it will allow before cutting out.. you can draw less without any problem, as long as you dont try to draw more.

you canot flip from 48v to 24v on the fly with a 16 cell BMS..

If you make 2 packs, 8 cells each( 2 seperate 24v packs ) , with each it's 8 cell BMS, those BMS's need to be able to deliver 40 amps if used individually.. hooking 2 packs with BMS's in parallel may be a problem, this is where diodes come into play...

 

[Quajochem]

I know the 16s bms is of no use offcourse..

Yeah and I will use diodes. That put aside, do separate BMSses, when used together in series or parallel always register the total amp rate drawn from the controller or is it 20A for each BMS, 40A / 2?

And will the charging be more accurate if 2 separate chargers are used?

 

[Ypedal]

are all 16 cells going to be used at 24v only ? or do you need to use 24v on one bike. .. and for some reason 48v on a different bike ?

 

[Quajochem]

all on one bike, but I want to be able to switch back and ffwd between series and parallel, AND I want to be able to use the packs on other ramdom bikes for testing and such. I just want 2 working batteries and be able to draw 40 amps cont from them without the bms shutting down.
And I was just curious if the bms registers 40 amps when its parallel with another similar pack.

 

[parabellum]

Would 2x 20+A 8s BMS in theory be enough, or do they both need a 40+A 8s BMS?

1)You need 2x 8s packs each having own BMS for parallel/serial capability (if BMS is desired).
2)You need 40A or more on each BMS to discharge 40A in serial connection.
3)You can charge your packs in series with 48V CC/CV charger, but diode mode must be done previously. Preying to not let fail 1 of your BMS with open charge input is recommended. I personally would prefer 2 isolated 24v CC/CV chargers.

 

[dnmun]

you cannot swap out a 48V battery with a 24V battery using the same controller.

your duplicate thread mentioned bottle batteries?

if you have the 16S BMS and a 48V charger and a controller that works on 48V nominal, then you should build that and skip the playing with 24V since the controller will not work at that low a voltage.

this diode stuff is totally bogus too. do not put diodes in the current path unless you are mixing different chemistry packs in parallel. which nobody does anyway, so you should eliminate diodes from any consideration in this 48V system.

 

[Ykick]

For testing purposes why not just manual balance or go Lipo? Lipo strength is when testing various voltage & current applications. Easy to configure and they really don't need BMS if you keep a decent eye on 'em. Fairly small and lightweight too.

Plus, if you get a quality RC charger to go wth your Lipo you can also use that on various Headway configurations and/or practically any battery troubleshooting and managing needs.

 

[parabellum]

you cannot swap out a 48V battery with a 24V battery using the same controller.

Depends on controller, I drive my Lyens 18fet 4110 from 8s-24s LiPo, have not tried less then 8s.From other angle dnmun is right, you should check if your controller is capable of that. If your logic circuit is under volted, it can fail to close Fet, creating short and blocking your motor.

do not put diodes in the current path

I finally got what is your problem with diodes!
Diode does not go in current path, it is placed in parallel to BMS output. Actually the diode is not participating in normal working condition(no current flows trough) , it kicks in when pack stops being serial energy source (BMS switches off the pack) and starts being serial load (being parallel to source in reverse voltage condition).
Diode is also sometimes necessary for serial pack charging, it lets the second pack to get to full charge if other switches off before it happens. But it depends on how your BMS is interconnected (charge input, discharge output). In some cases diode can even make harm while charging.

 

[Quajochem]

That other tread I started is not a duplicate tread, it's about a bms physically shaped more like a cube instead of a leaf, so it would fit inside a tube better.. like 8x8x4cm? Cooling will require some tube modding but I'll figure that out too, shouldn't be that hard).

And I don't know where to put te 16s BMS if I decide to use a 2 pack system, one on the right and one on the left about 20cm a part under front carrier..like bombs ready to drop... controller in between so that's why I want 2x BMS, (2 modules, interchangable geometric shaped, I like that) and I want to be able to take the batteries off in a minute or so for charging and to prevent my bike being stolen when leaving it somewhere unguarded... So with just 1 BMS there would be too much connectors and wiring going on...

I have bought the headways already so I will go with lifepo4, maybe on my next build I will go lipo..
I just wanted to know about the amps and stuff so I know that now, thanks.
You're right about the controller not handling 24v so i'll drop the parallel setting..

Now I'm looking for a small size 40A BMS (80x80x40mm).

As far as testing goes, I might do that with lipo, but the 'testing' I am talking about is all about bikes that will be sold legally on the local market, max 500w, max 25km/h, so any battery will do on those.. It's just about finding new clean solutions for non electric city bikes (typical dutch bikes with carriers, mudguards, heavy, relatively cheap no suspension and slow geometry) wich I will make electric.
I am working on a cheap modular kit with few wires/parts to put on a normal bike and sell to normal non demanding people.
So i'm setting up a small business together with a friend of mine who has a bicycle store, I like this business model:
http://www.bikebuilders.nl/ Look at the bikes, they look ok to me, I am not allowed to sell faster bikes.
I know I won't get rich any time soon, but I don't mind that, as long as I don't loose alot of money..

In the future I want to totally design a new model (more looking something like the A2B, or at least designed for being electric from the ground up) but that's just not happening in the next few months.
The next few months I am gonna tweak maybe 3-5 'slow' bikes, by changing them into (boring but sellable) pedelecs, and for the sake of some fun, go alittle faster on my own existing bike while I am at it, trying out some new shapes for battery casing and such, to possibly swap the concept later onto a different bike wich I will sell..

I still haven't got my head around on what the Dutch people will like more, is it lipo (small lightest but less durable) or lifepo4. I always thought lifepo4 was becoming the norm over here, but I think maybe a made a mistake with lifepo 4, because they are not nearly as reliable as I thought they were, only bigger, heavier and more expensive.... atleast they are safe...

I guess I just like the concept of really big cylindrical batteries that look like duracell batteries and nothing more, reminding me and others of the old days

 

[Quajochem]

For testing purposes why not just manual balance or go Lipo? Lipo strength is when testing various voltage & current applications. Easy to configure and they really don't need BMS if you keep a decent eye on 'em. Fairly small and lightweight too.

Plus, if you get a quality RC charger to go wth your Lipo you can also use that on various Headway configurations and/or practically any battery troubleshooting and managing needs.

You know I might just do that, I am sick of buying different voltage chargers all the time just for testing. So this charger you're talking about is one you can ajust easily to any voltage upto say 80v and current aswell?

And I don't trust myself running without BMS yet, I could care less about the LVC set too low on the controller because I know I am carefull on that part, but the rest is still too much abacadabra for me :lol:

 

[Quajochem]

you cannot swap out a 48V battery with a 24V battery using the same controller.

Depends on controller, I drive my Lyens 18fet 4110 from 8s-24s LiPo, have not tried less then 8s.From other angle dnmun is right, you should check if your controller is capable of that. If your logic circuit is under volted, it can fail to close Fet, creating short and blocking your motor.

do not put diodes in the current path

I finally got what is your problem with diodes!
Diode does not go in current path, it is placed in parallel to BMS output. Actually the diode is not participating in normal working condition(no current flows trough) , it kicks in when pack stops being serial energy source (BMS switches off the pack) and starts being serial load (being parallel to source in reverse voltage condition).
Diode is also sometimes necessary for serial pack charging, it lets the second pack to get to full charge if other switches off before it happens. But it depends on how your BMS is interconnected (charge input, discharge output). In some cases diode can even make harm while charging.

Ain't it nice to have that diode discussion out of the way hehe (I already knew that)

And O I forgot to mention I got the Lyen 9FET, so maybe it runs on 24 volts I'd have to check the software for the lowest LVC setting....
(Still waiting on my motor so no time for real testing yet :? )

 

[dnmun]

i don't have a problem with diodes. you continue to tell people they have to install diodes in parallel with the BMS for some reason.

i have explained several times that the diode does not do anything. i have asked you to draw up the equivalent circuit to prove your point that the diode is needed. you refuse to do so.

it does not help people who have no experience with electronics for you to confuse them with issues that don't merit incorporation into their designs. you do so without demonstrating in any way why this extra diode is needed to be placed in parallel, except for the special case you have developed to use 8S-24S for some unknown reason, which does not apply to anyone else.

 

[Quajochem]

It was something about the current flowing backwards through the BMS wich it's not designed for wasn't it?
I don't see no harm in soldering on 2 tiny extra things, but if it's really not neccecairy I would be wasting my time, not that I am not wasting it already
If they were only neccecary for when you stick 2 different voltage packs parralel I would definately install them, because I like messing around, and I have a 36V pack laying around, 24+24+36= haha (just joking I apparently do not understand this fully, but I do know some basics about elctronics, like how to make DC from AC with 3 eeehhh 4 diodes.... It's a long time ago though)

 

[Ykick]

For testing purposes why not just manual balance or go Lipo? Lipo strength is when testing various voltage & current applications. Easy to configure and they really don't need BMS if you keep a decent eye on 'em. Fairly small and lightweight too.

Plus, if you get a quality RC charger to go wth your Lipo you can also use that on various Headway configurations and/or practically any battery troubleshooting and managing needs.

You know I might just do that, I am sick of buying different voltage chargers all the time just for testing. So this charger you're talking about is one you can ajust easily to any voltage upto say 80v and current aswell?

And I don't trust myself running without BMS yet, I could care less about the LVC set too low on the controller because I know I am carefull on that part, but the rest is still too much abacadabra for me :lol:

This is one RC Charger many swear by and a good read - http://endless-sphere.com/forums/viewtopic.php?f=14&t=23362&hilit=hyperion

iChargers are great units too. However, none that I know of will get you to 80V without splitting up into series strings.

This would not be for end users but for design work RC chargers are so useful and simply a good "tuition" into battery electric vehicles/devices.

 

[parabellum]

Ain't it nice to have that diode discussion out of the way hehe (I already knew that)

Sorry to trow it on your topic, it about 4th time I tried to explain this diode think to dnmun

i don't have a problem with diodes. you continue to tell people they have to install diodes in parallel with the BMS for some reason.

i have explained several times that the diode does not do anything. i have asked you to draw up the equivalent circuit to prove your point that the diode is needed. you refuse to do so.

it does not help people who have no experience with electronics for you to confuse them with issues that don't merit incorporation into their designs. you do so without demonstrating in any way why this extra diode is needed to be placed in parallel, except for the special case you have developed to use 8S-24S for some unknown reason, which does not apply to anyone else.

Here is educational picture for you. Hope you will get it finally and find another concern to freak out.

 

[dnmun]

you would never use two packs in parallel with different voltages. if you combine a 48V NiCad in parallel with a 48V lifepo4 then you would use the shottky diode with two legs on the input and one leg on the output. then each pack positive would go on one of the input legs and then the current from one pack does not flow into the other pack through the diode. in that case the schottky needs only withstand a few volts difference between the two packs, not a full 48V. but when current flows through the diode, the voltage drop causes a power loss. the forward bias is .4V so at 40A then it would produce 16W of heat to melt holes in your battery bag, and the power is lost to the motor.

current cannot flow backwards through the BMS under any circumstance. if the BMS shuts off then the output FETS will be turned off and will withstand any current flow.

 

[Quajochem]

I don't know nothing about RC chargers and wich one would suit me well, so that's another day of studying for me

 

[Quajochem]

Ain't it nice to have that diode discussion out of the way hehe (I already knew that)

Sorry to trow it on your topic, it about 4th time I tried to explain this diode think to dnmun

i don't have a problem with diodes. you continue to tell people they have to install diodes in parallel with the BMS for some reason.

i have explained several times that the diode does not do anything. i have asked you to draw up the equivalent circuit to prove your point that the diode is needed. you refuse to do so.

it does not help people who have no experience with electronics for you to confuse them with issues that don't merit incorporation into their designs. you do so without demonstrating in any way why this extra diode is needed to be placed in parallel, except for the special case you have developed to use 8S-24S for some unknown reason, which does not apply to anyone else.

Here is educational picture for you. Hope you will get it finally and find another concern to freak out.

Sorry but the pics don't exactly make things more clear to me, I guess they're just one notch too simple for me. I don't mind about you throwing it on my topic, go ahead! I want to learn more But if one of you happends to know a good source for a smaal BMS I would be more than happy!

 

[999zip999]

Ping sells them, bmsbattery and a number of other battery sellers. where are you located and how mant amps do you want protection for 40a, 60a, ect.

 

[dnmun]

ping is the only one who sells 8S lifepo4 BMS.

 

[Quajochem]

I am located in the Netherlands, Europe

 

[parabellum]

Sorry but the pics don't exactly make things more clear to me, I guess they're just one notch too simple for me. I don't mind about you throwing it on my topic, go ahead! I want to learn more But if one of you happends to know a good source for a smaal BMS I would be more than happy!

Thanks, I did it the simplest way I could, I even did 3 intents simplifying it and using color markers, all for dnmun

Your question should be small and reliable BMS.
Be careful with smart BMS from Bmsbattery.com, it is the worst junk. Have been testing two (and at least 1 other member as well) with horrible results, they randomly shut down with charge and discharge port open, leaving battery unprotected (without you knowing that). Bottle kind looks very similar. Stick to analog type if possible.

What are your BMS size limits?

 

[Ypedal]

Could email paco at

http://www.cyclone-tw.com/

he deals with 24v stuff that can deliver 40 amps for his kits.

http://www.cyclone-e-bikes.tw/product.php?pid_for_show=3266

 

[Quajochem]