idea for go-baby-go button

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mlt34   100 kW

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idea for go-baby-go button

Post by mlt34 » Mar 04 2016 2:27am

I'd really appreciate some feedback on an idea for a sort of "nitrous button" for my ebike. My setup is a dual motor Q100h build @14s with 20A limit for about 1000W peak and getting about 29 mph hot off the charger. My daily commute covers everything from small roads to 4 lane city highways. On the big roads it would be nice to get another 4-5 mph at certain times when I need to overtake or get off the big road quicker. 16s would do it but I don't want to add another 14 cells to my 14s7p battery as it's already big and heavy, plus I don't need that extra speed 90% of the time. So my idea is this: What if I add a small 2s lipo pack, maybe 2AH, to my bike on a switched circuit so it is normally bypassed, but when I hit the 'turbo' button it is suddenly wired in series with my pack (probably with a relay) to give my controllers 16s instead of 14s. I'd only need to charge the little guy occasionally as it would get sporadic use. And the lightweight and small size means it is barely noticeable and can even be left on the bike when I bring my main pack inside to charge each day. Thoughts?
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Re: idea for go-baby-go button

Post by Sunder » Mar 04 2016 4:05am

Theoretically possible: You'd need a NO relay joining cell 14 to 15, and a NC Relay joining cell 16 to load, which switch around when you flick the switch, but are you sure the Q100H is the motor to do it on?

You have to remember that voltage drives speed, current drives torque - so unless you're topping out the speed, there will be limited benefit of jumping voltage. In fact, if you weren't already near the top speed for 14S, you'll probably just turn the majority of extra power into heat, and burn out the motor - 1kw is already near the limit for a Q100H.
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mlt34   100 kW

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Re: idea for go-baby-go button

Post by mlt34 » Mar 04 2016 5:53am

Regarding the power, it's actually a dual motor setup, so each motor is at about 500 watts. I hit top speed while staying under my 20A CA imposed limit, so I've still got plenty of room to increase speed 4-5 mph, even if I bump up the CA limit a bit. At 20A right now, each controller and motor is pulling only 10A which is child's play. Much more than 4-5 mph extra though and yea I'd probably start decreasing efficiency at a higher rate.
Are you planning your first electric bicycle conversion? I wrote a book that teaches beginners everything they need to know about building their own ebike.
Then I wrote the book (literally) on building custom lithium batteries.
I also write for EbikeSchool.com, a site that does mainly how-to style articles and other informational write-ups. Check out our youtube channel for great how-to battery building videos.
Lastly, I run www.Vruzend.com, which sells solderless 18650 battery kits, 18650 cells, li-ion chargers, BMSs and more!

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Re: idea for go-baby-go button

Post by Drunkskunk » Mar 04 2016 10:27am

Possible, but next to impossible. but you have to switch off the battery system in the process of the relays moving. When the power is off, the controllers will reset. When they power back on, they may see the throttle at full and decide that is a fault. that would cause them to go into fault protection and not work.

to make this work, you would need to switch the battery off, reconfigure the circuit path, and switch back on faster than the controller could depower from the current left in it's capacitors on the low voltage side. If you do it too fast, or have a relay fail, you might actually short the Lipo battery. That wouldn't end well. (unless you're a spectator. :mrgreen: )

MOSFETs could be switched faster and safer, controlled by an Arduno or Raspberry Pi to get the switching done in sequence as quickly as possible. A large capacitor could be added to the low voltage side of the controllers to maintain power while switching.
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Re: idea for go-baby-go button

Post by amberwolf » Mar 04 2016 2:44pm

One other consideration is that if the spring of the contacts is not enough, relays can "bounce" or disconnect under vibration or mechanical shock, so if you expect that sort of thing on your rides at all, you're probably gonna wanna use either solid state relays, mosfets, or "vibration-proof" relays of some sort. ;)

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Re: idea for go-baby-go button

Post by Leebolectric » Mar 04 2016 4:53pm

just get used to hlaf throttle...then surprise yourself with full throttle... :wink:
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Re: idea for go-baby-go button

Post by Racer_X » Mar 04 2016 5:40pm

Yup I like this answer.
Leebolectric wrote:just get used to hlaf throttle...then surprise yourself with full throttle... :wink:
You could also just go with 18s and run on speed level one or two. Then surprise yourself with level 3 when the need comes ups.
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Re: idea for go-baby-go button

Post by liveforphysics » Mar 04 2016 8:14pm

Part of the beauty of electric is the opportunity to not be penalized for having big performance available at all times while still being a watt sipper while cruising/commuting.

Just pick the right battery motor and controller and you're already there with no special tricks needed.
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Re: idea for go-baby-go button

Post by bowlofsalad » Mar 05 2016 2:32am

What is being said pretty much fits the bill, I'd just make it so whatever battery/controller combo you were using already could provide the maximum power you'd want without the unusual configuration. What I've used a lot of the time on electric bicycles are three speed switches that limit the maximum throttle input to whatever preconfigured setting I chose. The thing about the switch is it's placement and swift function that made it so useful.
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This throttle keeps the switch at a fingers reach at all times. I setup speed 2 for my typical cruising around, speed three might be your go baby go, I don't know if this is viable with your setup though, but it's likely good food for thought. I suspect that if you setup a cycle analyst version three you could make all this happen relatively easily.

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Re: idea for go-baby-go button

Post by dmwahl » May 16 2016 10:23am

I use one of those 3 speed switches on my KMX, speed 1 is for other people riding, and limited to about 25%. Gets them to about 15mph. Speed 2 is my normal cruise speed at 60% (~25mph) and speed 3 is 100%, which is around 40mph or so.

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Re: idea for go-baby-go button

Post by MadRhino » May 16 2016 10:42am

liveforphysics wrote:Part of the beauty of electric is the opportunity to not be penalized for having big performance available at all times while still being a watt sipper while cruising/commuting.

Just pick the right battery motor and controller and you're already there with no special tricks needed.
+1

It is easy to ride slower than your top speed :wink:
Build to top faster than you need, then you only need to tame yourself or add a 3 spd switch 8)
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Re: idea for go-baby-go button

Post by teklektik » May 16 2016 12:08pm

mlt34 wrote:...I hit top speed while staying under my 20A CA imposed limit,...
I don't get it.

Why dynamically fiddle with switching batteries when you already have a CA?
In the general vein of the above suggestions, just use the CA current limiting so 100% is 'go-baby-go!' and 80% or 90% is 'normal'.

If you already are using a CA 3-position switch to limit current and don't want to change that, then an extra pushbutton and resistor will let you keep that working the way it is to scale the 'normal' max current, but with an extra '4th position' activated via boost button.

The CA isn't limited to only 3 positions...
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Re: idea for go-baby-go button

Post by teklektik » May 16 2016 6:19pm

Nelson37 wrote:IMO, this might have worked if done from day one, but what the OP wants is to go Faster than his current top speed, rarely and briefly. SFAIK, the CA does not have this capability.
There are two parts to the OP's plan:
  1. add more battery to get more go
  2. switch in that booster battery on the fly - (use some big honking switch to switch the full battery current without upsetting the controller or CA)
There's nothing wrong with (1) but (2) is simply a Bad Plan in many respects.

The CA approach allows him to permanently add the booster battery to his pack (1) and dispense with the Rube Goldberg high power switching in favor of a small switch or button handling only a few milliamps (2). The CA is to resolve the switching conundrum, not somehow manufacture more speed from the original pack.

As far as the booster pack is concerned, on the one hand there is adding a small 14cell or equivalent booster pack to match the existing battery and on the other hand, adding a slightly smaller (?) battery and relatively large contactor. Even assuming the contactor approach will work (unlikely) it doesn't seem that approach offers any material weight or size advantage. The booster pack is not ideal, but it doesn't require rebuilding the existing pack and has no impact on the present pack mounting. Presumably there is a spot somewhere on the bike for the booster since he's already considering it.
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Re: idea for go-baby-go button

Post by DRMousseau » May 16 2016 6:23pm

Mind you, that I'm jus an ol' man on a bicycle,... and rather new to the "e-bike scene". AND,... I'm very understanding of the OP's desire. I would have installed a nitrous boost had I gone to IC engines instead of "battry power"! Instead, I studied (many thanks to the wonderful members here) and shopped carefully to be certain my needs would be met in my initial purchase.

Currently,...
Cheap 29'er 7-speed cruiser from BB store (PLEASE forgive me)
Leaf Bike 1500w 48V rear hubmotor conversion kit on a 700c rim with Big Apple
Lunacycle 52V Panasonic PF 11.5ah "Performance Pack"

The Leaf kit controller allows 40A max (battery allows 50A continuous),... so I've got EVERYTHING I wanted, everything I hoped for, and more.

I often set cruise about 20mph, leaves me with some reserve if I need it. I luv arriving at a stoplight as the brake disengages cruise. Jus an ol' man on a bicycle. But when the green comes,... I AM GONE!!! Leaving the leading cars, they often accelerate a bit more even as they notice the ol' man on a bicycle is STILL moving out ahead!!! I'm in my "sweet spot",... and at about 25 or so they begin to gain quicker and are finally along side me at over 30mph!!! By the time the following cars are up to me, I'm doin near 40!!!! Now this is country highway stuff, where the speed limit is 45 or better. NEVER underestimate an ol' man on a bicycle!!! Motorists are often stunned and shocked in this scenario, and I luv it!!!

In the city,... under 35mph limits, I'm jus part of traffic. And a considerable bit quicker than most anyone else on a bicycle. Well,.... till a squad unit appears. Then I'm jus an ol' man on a bicycle,... peddlin' like all get out!!!!

I knew "upgrading" and modifying would be far more trouble than it's really worth. I'm glad I somewhat anticipated all my desires and needs in my initial purchase. Although I do sometimes wish for a disengagement of the brake switch,.... pavement burnouts with a locked front wheel at the stoplight would fun. And some punk in a quick car would likely capture much more attention and trouble than I,... hehehe.

I really gotta find me one of those "juiced" IC bikes,.... bet I'd beat 'em off the line AND in the stretch!!!!!
Nitrous,... HA! That's "old school" stuff today!!!! Who needs it!?!

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Re: idea for go-baby-go button

Post by Eteck » May 16 2016 6:56pm

What if I add a small 2s lipo pack, maybe 2AH, to my bike on a switched circuit so it is normally bypassed
When you're in turbo boost mode, how are you going to make sure they don't get over discharged ?

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Re: idea for go-baby-go button

Post by ddk » May 16 2016 8:48pm

my turbo boost is my second motor... as I normally run on one motor.

Are your controllers operable on 72V?
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Re: idea for go-baby-go button

Post by DRMousseau » May 26 2016 7:51pm

Well, I finally met a good match, and I had a fresh full charge!

The licensed, street-legal moped/scooter passed by at full speed with a nod to me, and I pulled out behind him from a dead stop at the corner. Took about a 1/2mi to catch up right behind him. Lookin in both his mirrors, he jus couldn't believe what he was lookin at. About a 1/4mi later, oncoming traffic cleared and I passed him with ease and a friendly wave,.... pedelin' air like crazy of course, "the old man" had to make it look good!

I pulled into the corner store drive well ahead of him, and he stared in amazement as he passed, at what appeared to him as an old man on a beach cruisin' bicycle.

I wonder if such a "button" could make passing wheelies! :D

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Re: idea for go-baby-go button

Post by cal3thousand » May 27 2016 12:03pm

Here's an idea:

Get a legit controller that has Field weakening, like a Sabvoton. It would give you that extra top end without adding batteries, changing motors, nor losing efficiency. The field weakening only occurs at the upper end of RPMs. Just have to fork out cash :(
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Re: idea for go-baby-go button

Post by chas58 » May 27 2016 1:59pm

I do this on my bike.

I have about 300-500 watts cruising with 1000w watts for short bursts of peak power. The extra power comes though my legs. It does rather surprise the cars though when I jump in behind them, and then draft.

Pickup truck drivers get real frustrated. it works best in traffic, where they are following someone and can't just floor it.
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