Search found 105 matches

by erth64net
Jan 01 2015 12:57am
Forum: E-Bike Technical
Topic: What's your Wh/mile or Wh/km
Replies: 18
Views: 2019

Re: What's your Wh/mile or Wh/km

DAND214 wrote:Where you've been for the last 5 years?
Hiding :shock:

I suppose I should have said that I have an itch to scratch, as I re-evaluate my power-assist design. Despite finding plenty of casual references when searching the forums, I couldn't find a specific thread since 2009.

Thanks for sharing.
by erth64net
Dec 31 2014 11:59pm
Forum: E-Bike Technical
Topic: What's your Wh/mile or Wh/km
Replies: 18
Views: 2019

What's your Wh/mile or Wh/km

The last thread I saw discussing eBike power-over-distance efficiency was back in 2009, and I'm really curious where numbers have gone over the past 5 years.

I've consistently drawn 12-15Wh/mile while zipping the Recchetta around. What's your efficiency?
by erth64net
Oct 06 2014 2:41am
Forum: Battery Technology
Topic: Retiring my first LiFePo4 pack
Replies: 13
Views: 1420

Re: Retiring my first LiFePo4 pack

Oops, didn't see the reply emails/notices - sorry for the delay. Any estimate on the number of cycles? How hard did you typically push it - discharge rate, depth of discharge, etc.? It saw a lot of use at first, although as life caught up with my project, I haven't used the pack much these past coup...
by erth64net
Oct 01 2014 11:27am
Forum: Battery Technology
Topic: Retiring my first LiFePo4 pack
Replies: 13
Views: 1420

Retiring my first LiFePo4 pack

Just thought I'd share this picture. I purchased this 24V/20Ah LiFePo4 pack from the eBay seller "pingping227" back in September 2008. They now sell through their website: http://www.pingbattery.com . Here in October 2014, this six year old pack is finally ready to retire. http://i.imgur.com/1TMFiQQ...
by erth64net
May 02 2013 4:53pm
Forum: Battery Technology
Topic: Minimalist BMS
Replies: 6
Views: 877

Re: Minimalist BMS

dmwahl wrote:You've got the crowbar circuit shown there, that will drain your caps down to 0 since the triac will continue to conduct until they're empty. The circuit above with the BJT is the one you want.
Eeek! Alright - I've edited the original posting and corrected the image. Thanks for catching that.
by erth64net
May 01 2013 10:43pm
Forum: Battery Technology
Topic: Minimalist BMS
Replies: 6
Views: 877

Re: Minimalist BMS

...take a look at the high current shunt regulator in TI's datasheet for a starting point. Check out my modular bms thread, I'll be posting schematics once I'm confident it works properly. Might give you some ideas. Thanks for the heads-up on your BMS thread . For the lurkers, the regulator schemat...
by erth64net
May 01 2013 2:49pm
Forum: Battery Technology
Topic: Minimalist BMS
Replies: 6
Views: 877

Re: Minimalist BMS

Make sure you account for the temperature coefficient over the full range, in the case of the one you chose the zener voltage will go down as the temp goes up, so it is unlikely to cause overcharging. You'll need to include a resistor or something to limit current as well, those zeners are only rat...
by erth64net
May 01 2013 1:40pm
Forum: Battery Technology
Topic: Minimalist BMS
Replies: 6
Views: 877

Minimalist BMS

Searching through the forums, I can see that Lee Hart is well known...although not much has been discussed about his minimalist battery regulator design that integrates just a visual indicator, resistors and a few zener diodes. For my initial test case, I'm considering use of 2.4V 500mW zener diodes...
by erth64net
Apr 30 2013 12:54am
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

Ok...that could make a nice launch assist - but if the truck was sans-batteries, what was your secondary power source? Diesel fuel. It was a hybrid. Cummins diesel engine primary power and electric assist using ultracapacitor electric energy storage. Well, now you've really piqued my intrest, and n...
by erth64net
Apr 30 2013 12:17am
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

1 Megajoule is a lot of energy. Dare you to drop a wrench across the bus bar. :twisted: What wrench? :shock: I'm not sure what Maxwell uses, but a crude version of a BMS circuit could work to balance the charge and prevent overvoltage on individual caps. Nice thing about caps is they don't need rea...
by erth64net
Apr 30 2013 12:13am
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

Here is a bank of boostcaps I did a few years ago. There are 156 cells and 155 balance boards. The opposite side looks similar with a bus bar and balance board on every other cap terminal. What was the application? Commercial class 4 hybrid truck. No batteries. Energy recovery (regen) / launch assi...
by erth64net
Apr 30 2013 12:11am
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

major wrote:I'm still having trouble with your use of terminology.
Please see: BCAP0010 spec sheet (also linked a few times earlier in this thread).
by erth64net
Apr 29 2013 11:28pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

major wrote: Here is a bank of boostcaps I did a few years ago. There are 156 cells and 155 balance boards. The opposite side looks similar with a bus bar and balance board on every other cap terminal.
What was the application?
by erth64net
Apr 29 2013 11:27pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

I'm considering the use of Maxwell Boostcap Ultracapacitors to capture braking/regen energy, and to assist with initial acceleration. The caps are relatively heavy so using them to accelerate means accelerating more weight. This will not be a good tradeoff unless the added weight is not that signif...
by erth64net
Apr 29 2013 11:15pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

Some amusing related videos ... http://www.youtube.com/watch?v=GPJao1xLe7w http://www.youtube.com/watch?v=z3x_kYq3mHM Yea, this idea is exactly what reignited my consideration of boostcaps; I'm already successfully using a couple of 6 cell 2600F packs on both my wife and my cars...although without ...
by erth64net
Apr 29 2013 8:04pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

I think the real challenge is to get power in and out of the capacitor bank over a wide voltage range. They start out at zero volts and the voltage increases as you charge them, unlike a battery. Yes, an ultracapacitor's linear charge/discharge voltage curve is a very valid concern. Although with a...
by erth64net
Apr 29 2013 6:25pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Re: Considering Maxwell BoostCaps

- What's the maximum possible charging current when using Maxwell's balance boards ? Maximum charging current is way more than you could ever regenerate. It would be over 1000A. 1000A over circuit board traces? Highly doubtful... Ultracaps are obviously capable of incredible charge/discharge rates,...
by erth64net
Apr 28 2013 8:09pm
Forum: Battery Technology
Topic: Considering Maxwell BoostCaps
Replies: 22
Views: 2550

Considering Maxwell BoostCaps

I'm considering the use of Maxwell Boostcap Ultracapacitors to capture braking/regen energy, and to assist with initial acceleration. The points not clear are: - What's the maximum possible charging current when using Maxwell's balance boards? - Is the derived energy density worth the cost and space...
by erth64net
Aug 15 2011 12:04pm
Forum: E-Bike Non-hub Motor Drives
Topic: Programmable Linear Hall Effect as PWM generator?
Replies: 0
Views: 337

Programmable Linear Hall Effect as PWM generator?

For signaling an ESC's throttle, has anyone considered using a self-compensating (temperature) programmable hall effect sensor as the PWM source? I'm thinking along the lines of a Micronas HAL 2850 , which supports anywhere from 30hz to 2Khz PWM periods...although I could use some help determining i...
by erth64net
Apr 11 2011 10:40pm
Forum: E-vents
Topic: Portland - PSU Friday, April 22 Earth Day Event
Replies: 31
Views: 5033

Re: Portland - PSU Fraday, May 22 Earth Day Event

Tom tipped me off to the event (thanks!). Not sure if I'll have my latest incarnation ready by then, but now I have a target date to shoot for :D

BTW: Anyone doing anything with hydraulic motors?
by erth64net
Dec 04 2010 9:24pm
Forum: E-vents
Topic: Portland, OR: Meet and Greet...
Replies: 71
Views: 12202

Re: Portland, OR: Meet and Greet...

webfootguy wrote:I'd really like to bring my Twike but I have a failed BMS board and I can't drive it on one battery pack. I may try to show up anyway.
Oh my...that thing is awesome! Even better, is that it only has a 3KW motor...*ahem*brushless*cough*outrunner*ahem* :mrgreen:
by erth64net
Dec 04 2010 1:53pm
Forum: E-vents
Topic: Portland, OR: Meet and Greet...
Replies: 71
Views: 12202

Re: Portland, OR: Meet and Greet...

Wow, intrest is spinning up & the weather is going to be great (for winter weather that is).

The CNC is carving a commissioned part now, and then with any luck the latest motor mount will be ready for my own bike. WHOO!
by erth64net
Nov 29 2010 5:56pm
Forum: E-Bike Non-hub Motor Drives
Topic: Why left-handed drives? Disk + Sprocket?
Replies: 9
Views: 1205

Re: Why left-handed drives? Disk + Sprocket?

Divide by 1.732 to get the Kv for Wye. Yep...in hindsight I realized that the Kt would jump with the respective drop in RPM/V for WYE... Ok, let me make sure I've got this correct: Delta Kv=332 RPM/V WYE Kv=~191 RPM/V (Kv/1.732) At 24 Volts (V) thats 4584 RPM (Kv*V) For WYE, Kt=.04999Nm of torque a...
by erth64net
Nov 29 2010 4:54pm
Forum: E-Bike Non-hub Motor Drives
Topic: Why left-handed drives? Disk + Sprocket?
Replies: 9
Views: 1205

Re: Why left-handed drives? Disk + Sprocket?

If I ran a Scorpion 4025 16T motor on 24V at a peak of ~80A (~8,000RPM), through a belt/chain reduction to a sane mid-drive output RPM of just 80 (matching my typical cadence)...I wonder what the torque would be at the hub? Knowing the velocity constant (Kv) of your Scorpion 4025, you can calculate...
by erth64net
Nov 29 2010 4:20pm
Forum: E-Bike Non-hub Motor Drives
Topic: Why left-handed drives? Disk + Sprocket?
Replies: 9
Views: 1205

Re: Why left-handed drives? Disk + Sprocket?

The central idler on a Bacchetta looks like an absolute natural for a Cyclone style mid mounted motor driving the chain line. One chain from chainrings to motor, one from motor to rear cassette. Yep :D I guess this needs a Schumacher style reduction gearbox and then a double freewheel with 13 or 14...