Your top ten priority features for battery pack?

Suirsuss

Suirsuss

10 µW
Joined
Mar 29, 2013
Messages
5
Location
Tennessee
Guten tag ES

Currently I am designing a battery housing for an object creation class and could use some help addressing
and prioritizing user needs.

heres my short list of categories :
size/max range - location/ bike handling - weatherproofing - security - aerodynamics - aesthetics ... any others?

More specific needs would establish an objective view of what is most desired by users rather than me generating my own needs.

stuff like the housing should look horrid to reduce likelihood of theft, box should have a lock... the housing should still allow other items to be carried or even more specific needs like ''the housing needs to weigh less than 10% of the total battery weight .''
 
Light weight and reliable!
 
arkmundi said:
Assuming you're talking about just the battery casing. In addition to above - its needs to be crash proof. In order:
steel or carbon fiber, easy access to battery for charging & reassembly, theft-proof, crash-proof, aesthetics
Click to expand...

well i guess Im not referring explicitly to the battery pack only ..maybe i should change the thread title to component housing... maybe I would discover some unforeseen constraints like .. x component should be more than mm from from Y thing due to heat
 
If on a dedicated ebike - it should be in the down tube / front triangle.

If modifying a none-ebike with a pack -
Aesthetics (somewhat subtle and no visible duct tape).
Size (small and light and still allows me to pedal if mounted between my legs)
Weatherproof.
Good Power (capacity and immediate output).
Frame mounted to keep centre of gravity low and bike well balanced.
Toughened case if in the line of fire (spray /debris from front wheel / in front of down tube).
Ability to be disconnected easily (switch)
Ability to be removed from the frame easily
Ability to be charged easily (no taking packs out, disconnecting individual cables - just a power and balancer plug for the whole pack).
Ability to be upgraded with new cells relatively easily.
Have an integrated lipo sack inside to hinder fire.

The front pouch on this bike is what I'd like to create on my own bike:
http://www.erikaskin.com/index.php?/projects/bend-moped/
3_bendweb.gif
 
For me, a battery pack has to be:

Crash proof
Light weight
High C rate and fast charging
Quick release
Standard on all my bikes

I see no other 5 priorities to make a top ten :wink:
 
In my case (trike)...

Good BMS that balances well.
Fireproof.
Removable from bike for fleet swappability
Waterproof battery box for physical protection - with carrying handle or strap
Modular construction - easy to replace individual cells and connectors/screws etc.
Isolated from other pack (diode)
Inexpensive
2C rating.

Using 15Ahr 48V Headways packs - 16S
 
no bms is stupid. why would you make that important. just an indication you have no respect for the power it can produce when shorted or how much damage is done by over discharge or risk of fire from over charging if you have lipo and bulk charge. how would you balance the pack without a BMS unless you had to use multiple balancing chargers or some other wire swapping parallel/series setups until the wires finally short out and catch the pack on fire?

first thing would be to select the voltage you will need, decide if you use lipo or lifepo4, how much capacity you will need for the job, and then figure out how to place it in the frame. for lipo you wanna have some way to remove the pack while it is on fire so you can get the pack away from the bike and the apartment building you are charging in. i recommend nomex sleeves around the lipo packs so they can be pulled out and carried while on fire. have a shovel around inside you apartment so when it does catch on fire it is easier to carry outside or into the bathtub.

then the cosmetic stuff. not first, but last. first things first, imo.
 
chvidgov.bc.ca said:
In my case (trike)...

Good BMS that balances well.
Fireproof.
Removable from bike for fleet swappability
Waterproof battery box for physical protection - with carrying handle or strap
Modular construction - easy to replace individual cells and connectors/screws etc.
Isolated from other pack (diode)
Inexpensive
2C rating.

Using 15Ahr 48V Headways packs - 16S
Click to expand...

Cost is the one thing everyone looks at. I'm surprised it took so long for anybody to say it.

I don't really think 2c is a requirement to look for though. It don't get much worse than that.


A pack has to have a bms. Avoiding one is going to need some serious explanation, Followed by some education. It is exactly what they are for. Battery Management System. The alternative is doing it yourself. The endless swapping of wires that is excess work leading to the eventuality of getting it wrong and telling everyone it was the batteries fault. There is a very strange mentality towards bms units displayed by a worrying number of people here. I myself was advised not to use one. I think by satin?
 
not everyone likes a bms dnum ;) it's my honest opinion

I have my own way of maintaining my pack

here are some of the safety features I've build in:

-no series / parralel swithing => eliminate user errors
-fireproof!
-CA LVC
-controller LVC
-main fuse
-each pack has a pcb with trace fuses so each cell has it's own balance fuse
-each pack has it's own cellog monitor with alarm + visual indication of each cell
-balancing using battmedics and a 25p sub-D plug (dual cellvoltage indication in case the medic or the cellog fails) and when needed I can use an Rc charger without opening my batterie case

there is still a lot of stuff that can go wrong, it's not idiot proof, it's not perfect but a BMS also has it's cons and pro's

I rather use what I use now then relying on a bms without any visual indication

if something goes wrong then I'm the blame for it, I can't blame the BMS i don't have ;)
 
Cost. No. more than $0,50 per Wh.
At least 10C discharge rate with 20C burst.
No on board bms to give false since of security and run cells too low.
Smallest possible.
Lightest possible.
Modular for easy replacement of bad cells.
Ability to reconfigure for different voltages in seconds.
Ability to remove from bike in seconds.
Secure good center of gravity on bike.
 
10 Priorities... hmm

  1. Compact: Highest power density/volume <- very important
  2. Economical: Lowest cost/mass <- so is this
  3. Reliable: Good quality manufacturing with great product history <- absolute must
  4. Connectivity: Solid Connectors & Wires & Taps <-implied by #3
  5. Performance: Delivers/Receives Current over a broad range in marginal weather <- so is this
The rest is gravy...

  • Quick Shipment: Not really a feature as it is a service.
  • Rugged - but that's sort of covered in Reliability
  • BMS? That's extra. Mine don't come with one.
  • Packaging - such as a bag or box? I make my own to suit.
  • Crash proof? Honestly - the onus is upon the owner to provide protection :p
Only the first 5, maybe 6 make my list.
Good to go, KF
 
dnmun said:
no bms is stupid.
Click to expand...

I could turn it back: Stupid people need a BMS, conscious people are better and faster at managing batteries than any electronic system. :wink:
 
A BMS is not an option. It's a must. But using or promoting non-working BMSes is just plain dumb. So until a working and reasonably priced BMS exists, the best thing is to not have one.
 
Tinto said:
If on a dedicated ebike - it should be in the down tube / front triangle.

The front pouch on this bike is what I'd like to create on my own bike:
http://www.erikaskin.com/index.php?/projects/bend-moped/
3_bendweb.gif
Click to expand...

Very interesting bike. I can't see the motor. Is the battery that lump in the middle? That seat doesn't look comfortable! :shock:
 
Our batteries are for mobile application and should be built rigid shake proof
and with plenty of cushion
Also placement as low on bike as possible
 
BMS or no bms is a bit like automatic transmission or stick in a car. Both work great, both work better than the other in specific situations. Neither choice is Dumb or for dumb people.

Anyway.

Number one priority always should be, and often hasn't been, THE BATTERY MUST BE ABLE TO RUN THE BIKE WITHOUT MURDERING ITSELF. Too often the price point of a small battery leads to a choice where the battery is good enough when new, but any loss of capacity due to age, misuse, or poor quality takes it off the cliff. Loss of 2 ah capacity, and now the battery cannot last long at the new rate of discharge. It's just designed cutting the size too fine to stand up to real world conditions.

After that, it's very nice if you get the rest. Longer cycle lifespan potential, less risk of fire, better quality control of cells, both in manufacturing and in matching cells to build the pack.

Good assembly, ask Boeing about that. Bad design can be an accident waiting to happen. This category also includes reasonable crashworthiness. Nothing survives every crash, but a poorly spot welded 18650 cell pack is not going to pass the test. I don't mean you can't build a robust 18650 cell pack, I just mean some have not. If half the cells disconnect because the box drops a few feet on shipping conveyors, it already failed. If a battery is sold "naked" then the onus is on the owner to mount it with some protection for it. But it's not on the owner for the battery to be able to survive a few bumps in the road. Good assembly means it doesn't disassemble itself if you hit a pothole or the postman drops it a foot as it kicks to the next conveyor.


On to the housing itself.

It should be reasonably weatherproof, removable, but lockable. You get all that with the typical alloy box you have seen. There is no reason other than economics to have to make it so ugly. But don't go crazy with style, and double the cost simply because you like round better than square. A standard, cheaper to make box can always hide behind a stylish body panel.

Most likely, it has a bms. If not, then it might come with a set of plugs making it easy to attach a charger than contains the bms functions for charging and balancing.

Id like to see a diagnostic port become the industry standard. Whatever plug format is used, the idea is that you could open a door in the battery box, and access a plug to read the voltage of each individual cell group in the pack. Currently, this would most likely be 6s or 8s female jst plugs that play with devices like a cellog 8. Then if the owner was not up to it, at least a technician would not have to disassemble the battery box to diagnose an out of balance battery pack.
 
A BMS is not an option. It's a must. But using or promoting non-working BMSes is just plain dumb. So until a working and reasonably priced BMS exists, the best thing is to not have one.
 
See my previous post. For lightweight fire retardant material, use FIBERFLAX (about 23,5$ per pint & about 10$ per 12"x24" sheets)

http://www.aircraftspruce.ca/catalog/appages/fiberfrax.php?clickkey=161217
 
awesome this is some excellent data I love you all. :mrgreen: ... i might probe by asking what DONT you like about YOUR component housing ?
 
All mine are Home made, so any flaws are my own. I tend to use a plastic box inside a metal box. The plastic fits around the battery super tight, preventing any chance of chafing the pouch cells. Then the metal box is just protection from weather and crashes.

FWIW, in a way there is no such thing as running with out a BMS unless you are dumb. Dumb would be slap a battery on the vehicle, and ride it with no monitoring of the state of charge whatsoever.

So what I mean is, if you don't have a device monitoring your battery for you, you should be watching a voltmeter at the very minimum. So the "BMS" can be your own eyes and brain. But you do still need a device of some kind to give your human "BMS" some information.

I would hazard a guess that 99% of us running "without a bms" do have a voltmeter, wattmeter, a cellog 8 in a pocket, or at the very least an LVC in the controller that will stop the discharge in time provided a single cell has not died. If one cell in fact did die, no bms would have saved that cell. Just a controller lvc can be good enough to save the remaining live cells.

What a bms does best is stopping overdischarge of a cell that has less capacity because the pack got out of balance. However, a human can pretty easily detect an undercharged cell at the top of the charge, before the ride, if he bothers to do it.

So riding off unaware that you have not properly charged a battery is what is dumb.
 
Suirsuss said:
awesome this is some excellent data I love you all. :mrgreen: ... i might probe by asking what DONT you like about YOUR component housing ?
Click to expand...
Each Battery assemblage is constructed differently on my ride:

  • Commuter Pack holds 18 lil' 5S1P LiPo bricks (arranged as 15S6P/63V @ 30Ah) and is custom modified from two camelbacks fabricated to drape over the top tube, then covered by Marine Vinyl for water-resistant protection, and finally a wrap of HDPE for aero/aesthetic + easy to clean. It is very convoluted to synch down; literally takes me about 15-20 minutes to disassemble and almost twice that to put back together. I try to check it about once/quarter for balancing. It needs it now in fact. Going to rain this weekend, so I'll git'r done. I want to have some sort of optional Balancing circuit so I don't have to go through this hassle (requested in this thread). None of my other packs below have this issue.
  • Saddle Bags fabricated from two TIMBUK2 handlebar bags modified to drape over the top of the Commuter bag in the Triangle. This assembly holds 12 LiPos split evenly between the two, and is readily accessible for maintenance. It is the easiest bag to reach and to mount; plugs straight into the main battery harness in 60 seconds. It instant adds another 20Ah... 66% more distance. Balances out quickly by manual effort. Between the Commuter and Saddlebags, I can just about reach 100 Seattle miles. The only thing I worry about is spilling batteries; it uses a simple Velcro flap to secure containment; better to have an additional security strap, clasp, clip, or zipper - although it survived the entire trip to California and back without mishap. Because they are located directly behind the front fairing - aero doesn't affect them too much and they don't get wet when we're in motion.
  • Panniers can hold 18-24 bricks over the rear tire. I built a custom framework to pad and shield the batteries from the binding fasteners (acorn nuts). Because of the mass, I have to add an ATV-style tie-down strap to prevent the panniers from flying off the frame, which in turn creates an issue when I want to stop and fetch my water bottle or other bit of food. Lastly, too much weight over the rear wheel affects the rear suspension and causes torsion along the frame that wasn't designed for load at that location. I only use panniers when I am on cross-country. They are not particularly aerodynamic - however they are bright yellow and thus quite visible.
  • Trailer is custom-built for towing more batteries, and they are stored in twin Sears Craftsman Toolboxes. The trailer covering is a bit of a pill to remove; that occurs once a day when on the road to camp/decamp, and access to the batteries is as simple as opening the toolbox. The housing is strong, simple, padded, and secure. The trailer can hold 30, possibly more bricks - though I use the rest of the space for tools, parts, and clothes. The overall design looks a bit hillbilly though is quite aerodynamic and stable up to 44 mph downhill. I built into the trailer two rear-facing catches to hold my fleece or quick foods. Originally designed to be a pusher trailer, but had issues so I moved the wheel to my FWD ebike where it became a 2WD afterwards. The trailer has no suspension so items get beat without padding.

There it is, warts and all. KF
 
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