A123 pouch 48V 20Ah pack with BMS

[circuit]

Is there anyone interested in the pack, similar to one I have used in my scooter conversion?
Price for one 48V (16s) 20Ah pack with BMS could be somewhere around 1600 USD, depending on overall quantity.
The BMS has over-voltage charger cutoff, over-discharge motor cutoff, monitoring of each individual cell, early balancing (it balances the pack in main charging stage, thus drastically reducing overall full charge time), balancing current of 1A.

[jimw1960]

I would be interested in the circuit board you used to connect the battery tabs? Is that custom made?

[circuit]

I would be interested in the circuit board you used to connect the battery tabs? Is that custom made?

Yes, everything is custom made. That circuit board is BMS itself. That is, BMS is mounted directly on cells and no additional box is needed.

[jimw1960]

I think you could do a good business selling just the circuit boards. Would you be willing to sell those and how much would you charge?

[oatnet]

Nice Build, with the best cells available to ebiker's today.

-JD

[circuit]

I think you could do a good business selling just the circuit boards. Would you be willing to sell those and how much would you charge?

At the moment I can't say exact numbers, but I guess it could be around 350 USD for ~16s-24s board. Possibly cheaper in higher volumes.
Is this price in "acceptable" range?

[jimw1960]

$350 could be a reasonable price, depending on the functions (HVC, LVC, balancing?) and power capabilities of the BMS.

[circuit]

At the moment functions of the BMS are:
* LVC (2V)
* HVC (3,65V)
* early balancing (1A bleeder), starts at ~50% SOC (state of charge) - this is the main advantage if compared to almost any other BMS
* unlimited power.
* gradual power decade on near-to LVC condition - it won't cut off you unexpectedly in middle of traffic, will give some time to stop safely.

You may ask why and how power is unlimited. Thing is, all decent motor controllers do have current limiting and additional limiting is not needed. My BMS does not have power switches on battery line, + and - of the battery pack connects directly to motor controller's "power" input. All you need is a standard fuse between battery pack and controller to prevent fire if wires or controller goes down. This allows to make the BMS very compact and save some energy that could be wasted on power switches.

You may also ask how LVC works if there are no power switches. Most decent motor controllers (all ebike controllers I know) have two red (BAT+) wires: thick and thin one. Thick one connects only to power mosfets inside the controller and thin one connects to internal voltage regulator to supply the logic. Thing is, if supply is removed on thin supply wire, the controller switches off and consumes absolutely no power, zero amperes. That means thick red supply wire (black as well) can be always connected to battery pack and draw no current, while thin red supply wire goes thru BMS - it is connected to BAT+ when: ignition is on, no LVC condition detected and charger is not connected. BMS switches power to thin red wire off when ignition is off, LVC condition detected or charger is connected. Thin red wire requires very low current and thus a small mosfet inside the BMS. I have tested this on many controllers, including GoldenMotor, Crystalyte, Infineon (Lyen).

HVC and charger control is done in similar way. Decent chargers do have "AC sense" output and "power" input.
AC sense is needed for BMS to know when charger is connected either to AC line (if onboard charger is used) or to battery pack (if portable charger is used). AC sense signal can be taken from charger (if it has this function) or simply as a switch on charger's connector, to know when cable is connected to vehicle. Actually AC sense signal can be not used at all, BMS can function without it. But it's recommended.
Charger's on/off is controlled via charger's control input, if it has this function. If not, additional module can be added to BMS to switch AC line or DC line (between charger and battery).

[Beavinator]

That is a super clean design! I absolutely love it! I have been thinking of doing a build with these cells for a while and your board solves my biggest issue. Nice work!

[circuit]

Thanks! I really appreciate it.

[joepah]

Is there anyone interested in the pack, similar to one I have used in my scooter conversion?
Price for one 48V (16s) 20Ah pack with BMS could be somewhere around 1600 USD, depending on overall quantity.
The BMS has over-voltage charger cutoff, over-discharge motor cutoff, monitoring of each individual cell, early balancing (it balances the pack in main charging stage, thus drastically reducing overall full charge time), balancing current of 1A.

Hi I tried your website but there wasn't an "English" button translation.

Are you still offering?

[circuit]

Hi I tried your website but there wasn't an "English" button translation.

Hi joepah.
Sorry, the website is only a blog and I don't have any sales over there. If you'd like to read it, please use this automatic translation service (just paste a link there): http://translate.google.com/#lt|en|

Are you still offering?

Current situation is this: I need to redesign the BMS for mass-production and I need to order cells in high quantities to get acceptable prices. The problem is that I managed to get only a few requests. I still design the BMS during my spare time, but this is very slow, as I have many other work, that actually feeds me.
Release date for commercial BMS, at this work rate, could be around January 2012...

[Bikin_Bob]

I'd be very interested! Also in a version wehre one could put packs in sereis for 40Ah. What about using the Goodrum/Fechter BMS? I'm no expert but are there shortcomings of this BMS not suitable for A123 cells?

[bigmoose]

circuit, very nice battery/BMS integration! I believe you have a product there! What price can you get the 20Ahr A123 cells for?

[circuit]

A couple of months ago I had a quotation for ~40USD/cell (20Ah, B grade), but this is cell only, with no shipping and no taxes (from China). Import taxes are around 25% (on top of merchandise and shipping). If I'd have to resell them, there would be some warranty service, testing, assembly of the pack etc... So the total price might be somewhere at "BMS + 65$/cell". It is still very hard to say exact numbers.
I might sell just the BMS, but this quickly gets very complicated and time consuming to explain everyone how to hook it up, how it works, etc... User's manual always is not enough and product support is very hard. And, of cause, free replacements, when user does something wrong and fries the product. So I'd prefer selling whole assembled pack and sleep better.

[Doctorbass]

hello Circuit,

Any updates?

I might be interested in 2 boards or more depending on the price.

cells price droped to 24-25$ per cell shipped .

I got 180 to work with...

Please give us any update.

Also could you make a version for 2p and 3p ?

Doc

[docnjoj]

Hi Circuit
Your board certainly solves one major problem working with A123 pouch cells in a very elegant way. Any hope for us "slowpokes" with only 12 S?
otherDoc

[circuit]

Guys,

I really appreciate that you like my solution. I am working (and my company is) on a commercial solution, but this will take some time, as we still have a lot of work with our current BMS. So, E-bike suitable BMS (A123-friendly and standalone versions) might be released in summer at best. It will have a cell preheating, bluetooth connection to PC and Android phone on the handlebar (speedometer, range estimation, statistics, cell voltage graphs, etc).
Solution will be modular and stackable, 4-12 cells per board. Power consumption at standby less than 100 µA. For a feature list, please take a look at our current BMS system:
http://www.elektromotus.lt/wiki/index.p ... Itemid=155
Hardware will be new, but features and software will remain similar.