Re-fit Turnigys with on-board BMS?

[MotoMel]

I purchase lithium batteries for use in electric bicycles. Batteries specially created for this use are usually encased and have a pair of discharge wires and a 3-prong connector for recharge. These batteries are rated 36V or 24V and 10-14 AH.

The respectively volted charger that plugs into them is of the simple plug-it-in-and-go variety, with no programming or connections to balancing wires required. So can it be assumed that these batteries have an onboard battery management system (BMS)?

It would be great to consider using Turnigy's or other RC-type lithium batteries, whose physical configuration could be arranged to fit in various containers. But expecting the typical eBike customer to fiddle with programmable balancing chargers with all the extra wires and equipment is hardly realistic. Is there a BMS that can be packaged with the battery so that a simple charger can be used with them?

 

[docnjoj]

It looks like you are manufacturing a chainwheel with a left sided freewheel chain to power the bike. Methods and kfong both make devices that help reduce the need for some monitoring for LiCo (LiPo for hobbies) packs but with this chemistry nothing is foolproof. It must be monitored in a safe charging area. You will still need a balance charger but those 2 engineers I mentioned make devices that can hlep safety with HVC and LVC pre set. As usual just my 2 cents but read a lot and you will come to your own conclusions regarding customer safety and hobby batteries. These cells do not have a BMS like the ones you use.
otherDoc

 

[dogman dan]

Chances are, the batteries you use have a bms. Open one up, to find out for sure.

Think long and hard before you sell batteries you have "modified". One fire could ruin your life.

 

[MotoMel]

You're spot on, Dogman!! Thank you for the absolutely justified concern about battery fire and safety. Actually, that's part of what is driving this research.

What I am thinking about is encapsulating battery and BMS in rectangular or square aluminum tubing of various dimensions from 2" to 5" on a side, with tube ends capped and only connectors and indicators visible. Batteries would be cushioned with thermally-conductive padding, cut off (almost completely) from oxygen sources, and fully mechanically protected on all six sides by the 1/8" 6061 aluminum. The batteries themselves would not be altered in any way.

It appears that most or all lithium RC batteries, whether Turnigy or Zippy or another brand, are sold with +/- electrical leads and a multi-wire balancing information lead (which I presume carries information on cell voltage). To the best of my understanding, all the smarts of balanced battery recharging are held in the external charger (e.g. the 1010B), which receives its power from a DC power source (an AC or DC converter usually), and then connects to the battery(ies) via recharge cables and balance info wires a la:

.
But this makes for a very messy recharge environment.

So I am trying to make it more like AllCellTech's

which connects very simply to a standard lithium battery charger and presumably handles all balancing with smarts contained in the battery pack itself.

Does that make any sense? I like the AllCellTech batteries and will use them more, but want an option for a hard exterior protective case that has a size which the AllCellTechs will not fit into.

 

[docnjoj]

The key is sthe difference in chemistry. AllCell is LiMn or LiNi chemistry not Hobby Lipo and should inherently be safer. Using the hobby batteries like from Hobby King is much more of a fire risk. Enclosing them in a sealed box is also not a good move as they could explode like a pipe bomb. You really need to do some research if this is for resale and do what all of the "good" suppliers do like ebikes.ca and efikessf and others. Stay away from LiCo like hobby batteries. They have wonderful properties but safety is not one of them. How about A123 20 ah cells combined with agniusm's kits for hand assembly. No safety problems there.
otherDoc

 

[MotoMel]

Great information and suggestions, thank you. I have to date provided a retrofit kit w/o the batteries, but have been asked to look into supplying those as well. I will divert my attention to the solutions perfected by others and perhaps partner instead of being the direct provider. As always, these forums are invaluable resources beyond what questions I thought to ask.

Does anyone have misgivings about our placement of an AllCellTech battery, thermoconductively padded and in such a tube, with minimal air passage through Anderson connectors in the tube end? Is there any condition for which the battery needs greater air i/o?

 

[docnjoj]

AllCell is apparently high quality Japanese ? cells in a wax matrix to help control heat. The only problems I see are
1. They are expensive
2. They are low C rate.Just my 2 centavos.
otherDoc
On the other hand you didn't mention the type of cells you want to use with the AllCell padding/wax. I hope you are not thinking LiCo hobby batteries.

 

[MotoMel]

The AllCellTech units come complete with batteries embedded, and there would be no fooling with that. For the past six months or more, AllCellTech has been looking into a hard plastic shell for their batteries, but has not come to market with one as yet. The aluminum shell would add noticeably to the weight, but would greatly reduce chance of battery puncture or bash damage in a trunk bag or other common container.

What batteries and associated technologies do you use and/or recommend?

 

[docnjoj]

Well we use a combination of Ping and Fatpacks home built. I just finished a 20 AH A123 battery with a great kit from a guy in Lithuania, agniusm, and 20AH A123 cells. There is a long but interesting article how he developed this assembly kit but it is leading edge and substantially cheaper than AllCell for the best cells in the world. It is DIY for the assembly, but a competent couple of workers could probably make 5-10 batteries per day each once they got the technique perfected. Dynamite stuff!.
otherDoc

 

[dogman dan]

What makes sense, is selling it all as a kit. They assemble it, and then assume the liability. This is the USA and all.

Lico is definitely a more hazardous chemistry than limn.

 

[t3sla]

you will find a BMS within the batteries you have talked about, they have a 10pin JST type connector.

I've been meaning to re-purpose one of these BMS canister units with some zippy cells, converting a 36V canister to a 72V pack that is heaps lighter.

 

[MotoMel]

Tesla (and/or others) -

Would you help me understand how, if the BMS is onboard already, a simple battery charger safely operates without communication with the BMS.

Thanks. Mel.

 

[neptronix]

Please forget the idea of using cheap lico packs as a consumer product.
There are many, many safer chemistries whose most common failure mode is not this:

[youtube]ctY4oBrqK5U[/youtube]

^-- 6S 5AH pack going up in smoke.

http://www.esfrs.org/blackmuseum/polymerBatteryPack.shtml


Look, as an end user, we accept this risk and ( hopefully!!! ) have been educated that this could happen if we abuse the battery... so we take the responsibility if it fires up..

But for an average 'end user', you cannot expect them to know this stuff.. and if you educated them first hand.. they would probably not be interested in buying anyway.

 

[MotoMel]

Thank you all. You have disabused me entirely of the notion of deploying such batteries! MM