100v+ Battery Build.

[The Mighty Volt]

Hi there- I am building a 120v battery pack for the first time, with A123 the preferred chemistry.

In terms of : safety, efficiency, etc, what should I know, and what should I do, not-do.

This is not so much about battery technology, just more about how not to have an accident, and how not to cause things to blow up and damage expensive batteries/components.

Specifically, I would like to hear your opinions on fuses, kill-switches, insulation, isolation, earthing, fire prevention, damage-limitation, BMS placement etc.

This thread is basically about how not to get badly hurt at worst or lose money at best.

Thanks in advance.

 

[Lyen]

Hello Mighty,

It's a good idea to perform a series of single cell discharge testing prior you weld the cells together. The cells around the top and bottom usually get a little more stresses so consider place higher discharge or higher capacity cells there. I found that out by using my CBA III. Just my 2 cents.

http://www.westmountainradio.com/CBA.htm

 

[The Mighty Volt]

Thanks Lyen. Helpful, as ever.

But what is more high-discharge than an A123!!! lol

 

[liveforphysics]

Thanks Lyen. Helpful, as ever.

But what is more high-discharge than an A123!!! lol

HobbyCity LiPo comes in a form about 2x higher discharge for the same capacity, and over 3x higher discharge with respect to weight/volume.

Do you have some motivation for exceeding 100v, and with it, the limit of a TO-220 fet based controllers usefulness for performance applications?

 

[The Mighty Volt]

Thanks Lyen. Helpful, as ever.

But what is more high-discharge than an A123!!! lol

HobbyCity LiPo comes in a form about 2x higher discharge for the same capacity, and over 3x higher discharge with respect to weight/volume.

Do you have some motivation for exceeding 100v, and with it, the limit of a TO-220 fet based controllers usefulness for performance applications?

Hi LFP, thanks for the feedback, I want to build a bike with 5Hp, so following the simple, if flawed, philosophy of VoltsxAmps= {k}W =HP, I figured that higher voltage would bring me into the region of higher horsepower, with all other things being equal.

The bike I am building is a one-off.....I won't be doing this again, with a road bike. I got really PO'd with old 36v Ebay LiFePo4, the sheer incompatibility of it all with the shape of the bike, the weight of it, it's general asthmatic nature when introduced to the sheer uselessness of Irish roads, Irish weather etc.

When I drop the hammer.....I want the power to be there. Basically.

PS I am running a Lyen controller.

I am just worried about the practicalities of working with high voltage.

 

[The Mighty Volt]

How would something like this be wired in? Or more importantly, where?

 

[Fligh High]

Mighty volt , since this is for an e-bike and you don't get so much out of breath as would be with pedal power alone this is definately the thing you need if you are into smoking !!
Just wire it up to a 12v source and you are good to go What can be better as smoking a cigar , a cig or even a nice joint when you want to relax and explore the world on two wheels.......

WAAAAHAAAA I can already see it visually before me , that thing nicely fitted in a convenient location somewhere on the handle-bars ready to use :lol:

smoke away ! (I leave it for others to explain)

 

[Fligh High]

It gets even better :lol: :lol: just read what Mighty Volt wrote 2 posts above .....

it's general asthmatic nature

epic , EPIC !!!! (poor Mighty Volt , sorry but this is such a fantastic FROCK UP , can't help myself...... )

 

[The Mighty Volt]

It gets even better :lol: :lol: just read what Mighty Volt wrote 2 posts above .....

it's general asthmatic nature

epic , EPIC !!!! (poor Mighty Volt , sorry but this is such a fantastic FROCK UP , can't help myself...... )

Hey, I just typed "kill switch" into google.....I think most people got the message. At least you have a sense of humour, which is more than can be said for 99% of this forum

 

[liveforphysics]

Going past the 100v limit means you've gotta use IRF4115 fets, (or buy a Kelly$$$ or have a custom controller built). This means you cut your current limit by roughly 50% from what you can do with the same controller configured to be at <100v using IRFB4110 fets.

For example, if you've got an 18fet controller with IRF4110's, you may be able to run 100v at 100amp, 10kw (if the motor is wound correctly for 100v, if not, you may not get close to that). If you have the same 18fet, but you built it for 150v, now you're going to be lucky to have it hold 50battery amps at 150v (7.5kw). And again, this is hugely dependent on the motor wind, because at 150v, a lot of motors will see 250amp+ phase current (what the fets feel) when the battery current is below 50amps in.

Going over 100v is the pathway to epic fail IMO (unless a controller comes out designed for it, which these TO220 package fet controllers are very very far from.)

I'm a total performance nut, always looking for the most power possible, and I'm actually going away from 100v down to 75v. From a system perspective, it simply makes more sense with the parts available.

 

[The Mighty Volt]

Going past the 100v limit means you've gotta use IRF4115 fets, (or buy a Kelly$$$ or have a custom controller built). This means you cut your current limit by roughly 50% from what you can do with the same controller configured to be at <100v using IRFB4110 fets.

For example, if you've got an 18fet controller with IRF4110's, you may be able to run 100v at 100amp, 10kw (if the motor is wound correctly for 100v, if not, you may not get close to that). If you have the same 18fet, but you built it for 150v, now you're going to be lucky to have it hold 50battery amps at 150v (7.5kw). And again, this is hugely dependent on the motor wind, because at 150v, a lot of motors will see 250amp+ phase current (what the fets feel) when the battery current is below 50amps in.

Going over 100v is the pathway to epic fail IMO (unless a controller comes out designed for it, which these TO220 package fet controllers are very very far from.)

I'm a total performance nut, always looking for the most power possible, and I'm actually going away from 100v down to 75v. From a system perspective, it simply makes more sense with the parts available.

Hi LFP, I couldn't agree more with you on the point about the system perspective.

My brother and a buddy attended a drag race yesterday with their Honda Civic Turbo.....350 BHP on Paper.......couldn't win a race. Why? ....they couldn't put the power down...wheelspin all the way. They would have done better with half the power.

I am using a Lyen controller, 4115 Fet's, 18 of them. That's the reason why I happen to be doing this build. I have the controller so I might as well use it. But I am cautious as I have moved into unfamiliar territory in terms of high-voltage, and being exposed to it in the form of a self-constructed battery. It's one thing to have a 100v system in your hands which is already insulated etc but to build it, align it and install it on one's own brings new risks.

On a technical aside....I plan to use a 5304....so where would that leave me in terms of the optimal voltage?

Thanks for your input!!

 

[liveforphysics]

You would be able to apply right about 2x the power with a 100v controller with 4110s. No joke.

 

[The Mighty Volt]

You would be able to apply right about 2x the power with a 100v controller with 4110s. No joke.

Are you saying that a 100v controller with 4110's is better suited to my designs?

Anyways.....seeing as you are king of {controlled} explosions......give us a few hints about wiring safely!

 

[liveforphysics]

Are you saying that a 100v controller with 4110's is better suited to my designs?

Yes in a big way.

Anyways.....seeing as you are king of {controlled} explosions......give us a few hints about wiring safely!

For the wires that carry high currents, use the best wire and connectors money can buy (because even at $5/ft, it's still cheap when you only need 8ft to do the whole bike). I personally don't like andersons, I think they are cheap high resistance toy connectors (most people love them). Pin and socket is my connector style of choice, you can find them on many of the RC connectors. Keep the wire length between the battery and controller as short as possible. Use big enough wire sizes that you don't need high-temp insulation, because it's never going to get hot. As far as insulation goes, getting shocked at 80-100vdc isn't really a big deal IMO. You feel it, kinda like a pricking tingle/burn feeling, but even across the chest, it doesn't seem like a big safety concern IMO.

 

[The Mighty Volt]

Cheers LFP

 

[John in CR]

Yes, "Dropping the Hammer" requires current. Voltage is for top speed.

What the hell is the kill switch for? That's only needed on brushed motors. On a brushless motor, all you have to cut is the power to the brain of the controller, which is a low current wire and any switch will work. Turn that off and the motor can't run. All you need is a fuse on the main battery wire, and a small switch on the controller start wire. Brushed motors need those big switches for safety, because a failure can result in WOT that can only be stopped by cutting the primary connection.

 

[The Mighty Volt]

Yes, "Dropping the Hammer" requires current. Voltage is for top speed.

What the hell is the kill switch for? That's only needed on brushed motors. On a brushless motor, all you have to cut is the power to the brain of the controller, which is a low current wire and any switch will work. Turn that off and the motor can't run. All you need is a fuse on the main battery wire, and a small switch on the controller start wire. Brushed motors need those big switches for safety, because a failure can result in WOT that can only be stopped by cutting the primary connection.

Maybe I am using the wrong terminology.....the idea of the key is to stop tea leaves taking your bike!! You break the connection, put the key in your pocket and then if they do cut the chains, at least they ain't getting away under power.

 

[John in CR]

I'd get a better and smaller key switch than those. Plus for good measure use the security feature in your Lyen controller that electronically locks your motor when you turn the controller off, so they'd have to carry it to make their getaway.

 

[spinningmagnets]

I have no experience with this, but...

From reading, I believe your hill-climbing goals could be met with 72V if the motor has at least 3 gears to use. You could use a despoked internally-geared hub as a transmission (Nexus?), or a custom BB-drive set-up similar to the Cyclone (no actual Cyclone parts, all upgrades). There are several impressive examples in the non-hub section. Best of luck...

 

[The Mighty Volt]

I have no experience with this, but...

From reading, I believe your hill-climbing goals could be met with 72V if the motor has at least 3 gears to use. You could use a despoked internally-geared hub as a transmission (Nexus?), or a custom BB-drive set-up similar to the Cyclone (no actual Cyclone parts, all upgrades). There are several impressive examples in the non-hub section. Best of luck...

Hi magnets.......I have decided to retain the full existing gear setup, Initially I wasn't but now I am. That might help efficiency a lot and my own natural 1 horsepower or so could make all the difference.

This means the cowling design for the battery storage has to be altered, and made wider to allow for the small amount of space surrendered to the bracket and pedals........