Radwagon 72v GMAC Phaserunner Build

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Bullfrog   100 W

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Re: Radwagon 72v GMAC Phaserunner Build

Post by Bullfrog » Jan 20 2020 9:10pm

RSwannabe wrote:
Jan 04 2020 9:29pm
Amberwolf - yes, it should be 17.7wh per mile. I corrected my previous post. The lights on the helmet are fully integrated into the structure and everything is smooth inside and out. I don’t think they impact safety in the event of a crash in any way.

In regards to the led strips, great minds think alike. Go back to the previous page of this thread and you’ll see I already added front white and rear red leds to the bike as you suggest. I have already received multiple approving comments about my new light setup from drivers and people walking by.
Ahhhh, I see why you are not having overheating problems compared to me, I am pushing an average of 36.4 Whrs per mile through my MAC and I am running a 13s battery.

Nice work...and thanks for all the documentation.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 28 2020 7:19pm

Bullfrog - Thanks. Its been a fun project and I'm loving riding the bike and how it performs now. I'm actually showing 16.6 WH/mile in my most recent charge cycle and 16.7 in the previous.

On a separate note, I've been seeing some interesting statistics regarding my regen braking. I've read plenty of comments and posts that regen braking is not worthwhile, or if it is, it's benefit is only so you can save wear on your brake pads and discs. I've read that you only get about 5% back at best, but I'm seeing far more than that. Attached are pics of my CA3 for my most recent charge cycle: I used 8.8 amp hours of battery (72v 10AH battery), but gained back 1.3 amp hours through regen, for a net expenditure of 7.5 AH in about 30 miles of riding. That's a regen recapture rate of 17.7% and is way higher than I have seen any other reports of, but I believe it. My riding is very hilly in city with lots of stops and starts, and I use only regen braking probably 98% of the time. I can do this because the GMAC geared motor regen braking is much stronger than what you get with a direct drive hub. The stronger regen also means its putting more power back into the battery. Also, the proportional regen control where I use the throttle lever to increase or decrease the amount of regen, gives me great control for faster or slower stops.

Anyone else seen results like this?
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AHicks   100 W

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Re: Radwagon 72v GMAC Phaserunner Build

Post by AHicks » Jan 28 2020 8:19pm

The advanced regen available with the GMAC and their matching controller is what attracts me to the GMAC potential. The regen available with this setup is NOTHING like what most people are talking about that's available with DD hubs - for the reason you mentioned. This thing is gear driven and turning 5 times faster than a DD making for a MUCH more capable regen function. Regen that's available right down to nearly stopped, vs. maybe 12-15mph for some comparatively meager braking from a DD.

It's not hard for me to see you're replacing a significant %/amount of battery power in use. -Al

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Re: Radwagon 72v GMAC Phaserunner Build

Post by goatman » Jan 28 2020 8:35pm

RSwannabe wrote:
Jan 28 2020 7:19pm
Bullfrog - Thanks. Its been a fun project and I'm loving riding the bike and how it performs now. I'm actually showing 16.6 WH/mile in my most recent charge cycle and 16.7 in the previous.

On a separate note, I've been seeing some interesting statistics regarding my regen braking. I've read plenty of comments and posts that regen braking is not worthwhile, or if it is, it's benefit is only so you can save wear on your brake pads and discs. I've read that you only get about 5% back at best, but I'm seeing far more than that. Attached are pics of my CA3 for my most recent charge cycle: I used 8.8 amp hours of battery (72v 10AH battery), but gained back 1.3 amp hours through regen, for a net expenditure of 7.5 AH in about 30 miles of riding. That's a regen recapture rate of 17.7% and is way higher than I have seen any other reports of, but I believe it. My riding is very hilly in city with lots of stops and starts, and I use only regen braking probably 98% of the time. I can do this because the GMAC geared motor regen braking is much stronger than what you get with a direct drive hub. The stronger regen also means its putting more power back into the battery. Also, the proportional regen control where I use the throttle lever to increase or decrease the amount of regen, gives me great control for faster or slower stops.

Anyone else seen results like this?
im running a phaserunner with a DD hub 17s 10ah battery. I got 13% regen the otherday. my other controllers would only give me 400 watts regen but by adjusting the phaserunner I saw 780 watts and the braking is awesome I rarely use the brakes. im only operating the regen with a push button are you using a separate thumb throttle for regen?

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Re: Radwagon 72v GMAC Phaserunner Build

Post by amberwolf » Jan 28 2020 11:06pm

as noted above, because the gmac is being spun up by gearing, and because you have lots of stops/starts plus hills, you'll see higher regen than typical.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 29 2020 11:56am

Ahicks - yes, I am of the opinion that not many people have experience with geared hubs without clutches that are therefore capable of regen braking. Almost all comments regarding regen braking are in regards to direct drive hubs. With the GMAC, I can use regen braking to bring me to a complete stop.

Goatman - It is interesting to see that you are getting 13% recapture with your DD setup. That is a higher number than I have seen others report. With my GMAC, I have it set to allow up to 1500 watts of regen back into the battery. I am often seeing 500-1500 watts regen during braking. I have hall sensor switches on my brake levers, so whenever I pull the brake levers the regen braking engages. To brake, I just lightly pull one of the brake levers which is enough to engage regen, but not have the brake pads engage the rotors. When I have the brake lever lightly pulled and regen engaged, I can then use the thumb throttle to vary how much regen braking I get. Full thumb throttle gives me maximum regen. The base level regen (no throttle) is still stronger than the regen my previous DD hub motor was capable of (the stock Radwagon setup showed up to 750 watts of regen possible). Full regen with the GMAC (with full throttle used) feels like I've grabbed a pretty good handful of brakes. While it may sound overly complicated, it is all very intuitive (for me at least) and easy to use in practice.

Amberwolf - Yup.

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SamRich   100 W

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Re: Radwagon 72v GMAC Phaserunner Build

Post by SamRich » Jan 29 2020 4:01pm

That's a very clean build! You can barely tell that's it's electric.
I think I might steal that string LED idea. Thanks for sharing all those pics!

If it's ok I thought I'd share a few pics of my similar build.

Had my Radwagon for nearly 2 years now.We bought it used on CL (2016 model I think). The previous owner had made significant changes - new wheels/battery/motor/controller, which I didn't use for this bike. So basically started with a bare Radwagon frame.

First off I built a triangle 52V 30Ah (14S10P PF) battery housed in polycarbonate cover - bike has 30-50 mile range at decent/fun speeds (no speed limiter). The battery (BMS) has bluetooth capability and display to indicate battery temp, speed, remaining capacity and estimated range as well as individual cell voltage for diagnosis.

Second, the 1500 W motor is laced to a rear moped rim and 3" moped tire which pretty much eliminates the risk of rear flats. The controller is a 50A sinewave "dumb" controller for Aliexpress, but has been solid with regen.

Added steel fenders that clear the wider tires and four piston Magura MT5e hydraulic brakes. Finally, added wireless speakers for the kiddo behind the front seat.

Since then I also built a 72V 20s7P 30Q pack that fits in the same PC shell, but the 52V pack works great for now.

The PC shell:
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Heated and folded
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Honeycomb holder and panosonic cells:
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during welding with k-weld:
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3D printed case for ANT_BMS display.
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goatman   100 kW

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Re: Radwagon 72v GMAC Phaserunner Build

Post by goatman » Jan 29 2020 7:48pm

72v 10ah battery and 1500 watts regen, how many amps are you putting into your battery, im at 16 amps, my cells can take 4 amps at fast charge and im 4p but I think my regen amps are at 30 amps.

I notice you connected the phaserunner to a heatsink, have you noticed any heat there from the 1500 watts of regen? isn't that where the heat from the extra regen amps would wind up

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Re: Radwagon 72v GMAC Phaserunner Build

Post by amberwolf » Jan 29 2020 8:10pm

goatman wrote:
Jan 29 2020 7:48pm
72v 10ah battery and 1500 watts regen, how many amps are you putting into your battery,
math. ;)

1500w / 72v = 20.8a

actual amps (and watts) depends on actual instantaneous voltage at any moment during regen, but if 1500w is an average, then the average amps is all you can determine from it. ;)

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Re: Radwagon 72v GMAC Phaserunner Build

Post by goatman » Jan 29 2020 9:54pm

amberwolf wrote:
Jan 29 2020 8:10pm
goatman wrote:
Jan 29 2020 7:48pm
72v 10ah battery and 1500 watts regen, how many amps are you putting into your battery,
math. ;)

1500w / 72v = 20.8a

actual amps (and watts) depends on actual instantaneous voltage at any moment during regen, but if 1500w is an average, then the average amps is all you can determine from it. ;)
the phaserunner is a little confusing to me, if 20.8 amps is going into the battery then I guess that a battery can receive more amps through regen than a battery charger because its only a burst of energy?. I suppose I could pump up the phase regen amps to 60 and battery regen amps to 20 but that may be a little hard on my spokes unless I use a thumb throttle to slowly activate the regen. I was worried about cranking up the phase regen amps beyond what the battery regen amps. the controller has to dump the amps somewhere so I figured it was getting dumped as heat in the phaserunners heatsink.

rswannabe is a 20s3p ga 10 amp/cell battery so I figured the extra amps were dumping into the custom heatsink

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Re: Radwagon 72v GMAC Phaserunner Build

Post by john61ct » Jan 29 2020 10:00pm

My understanding is, that regen energy shown is an exaggeration well above what's actually getting back into the battery.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by amberwolf » Jan 29 2020 10:23pm

on the ca, regen current (on the current readings page, that's "amin", if a negative number) is exactly the current flowing back to the battery, because it is using exactly the same shunt that it uses to measure the current out of the battery, to get the regen measurement, becuase the current is flowing on exactly the same path, just in reverse.

there's nowhere else for that current to go, so it is going back into the battery.


whether the battery can handle that kind of current, or if it's bms can, is a totally different thing, and that depends on those devices themselves.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by goatman » Jan 29 2020 11:57pm

okay thanks, ill just max out the phaserunner settings and use the CA

RSwannabe   100 mW

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 30 2020 12:31am

My understanding is many BMS do not regulate regen current. Thus when “charging” a battery via regen through the primary output wires, it bypasses the BMS charging charging circuit. That is the case on my battery. In researching what was safe amount of regen amperage, I was told because regen is usually short bursts you can use a higher amperage than would be safe for prolonged charging. The short durations don’t allow the battery to get too hot or create dendrite structures. Justin at Grin indicated he has not seen issues with higher regen amperage hurting batteries.

In regards to the heat sink on my phaserunner, I’ve never even felt it get warm. I don’t think I run my setup near hard enough to really stress it. More research also indicates I’m far more likely to overheat the GMAC motor before the phaserunner gets too hot. And I’ve not gotten close to overheating the motor yet either.
Last edited by RSwannabe on Jan 30 2020 11:03am, edited 3 times in total.

john61ct   100 GW

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Re: Radwagon 72v GMAC Phaserunner Build

Post by john61ct » Jan 30 2020 12:36am

Are we talking 2-3C or even higher?

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 30 2020 12:39am

I believe my 20 amps max regen equates to a rate of a little over 3C (CORRECTION- it is actually a 2C rate. See posts below).
Last edited by RSwannabe on Jan 30 2020 10:48am, edited 1 time in total.

RSwannabe   100 mW

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 30 2020 12:45am

My 20 amps max regen is just under a 4C rate. (CORRECTION- it is actually a 2C rate. See posts further down). My Panasonic Sanyo GA cells have a charge constant of 1.675 amps. Thus a 3p battery configuration gives a 1C rate of just over 5 amps (5.025 to be exact). So 20 amp charge rate is 3.98C for my battery.

To be clear, I am not a battery expert. My research and talking to people like Justin and others with far more experience than I leads me to believe that charge rates of up to 4C for short bursts won’t be significantly detrimental. But I have no solid data to back this up.
Last edited by RSwannabe on Jan 30 2020 11:04am, edited 3 times in total.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by john61ct » Jan 30 2020 1:14am

Short bursts I guess is the key, as in a few seconds.

Once getting the cells hot, maybe not "damage" but reduced cycle life longevity of the back end.

If already being stressed by a lot of high C-rate discharging, might only be single digit percentages, NBD.

If the pack's otherwise being coddled might be more significant.

Definitely not a good idea as the cell temp is cold, as in winter.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by amberwolf » Jan 30 2020 1:53am

it doesn't exactly bypass the bms...it's still going thru it's fets. but if the bms uses separate charge and discharge ports, then it cannot do anything about overcurrent or overvoltage coming in on the discharge port (it will turn off the charge port when these happen, but it doesn't "know" it should turn off the discharge port because it shouldn't be coming from there).


if it has a single common charge/discharge port, then it can turn off the port upon overcurrent or overvoltage, so could protect against overexuberant regen currents or voltages. ;)



fwiw, if you have a bms with separate ports, you should be able to use sets of schottky diodes of sufficient power level on the output to block regen from entering the discharge port, along with another set to prevent output from the charge port, and then wire from the controller side of the diodes to the charge port diodes, so that regen current is run only to the input, and discharge current is only run from the output. my brain is shutting down some so i can't draw this out right now.

it shouldnt' be necessary to do this but if you wanted an extra safety feature....

the catch with the diodes is that they do drop voltage, and thus create heat, so the more current you push thru them the hotter they get, and tha'ts all wasted power.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by thepronghorn » Jan 30 2020 2:41am

RSwannabe wrote:
Jan 30 2020 12:45am
Correction, my 20 amps max regen is just under a 4C rate. My Panasonic Sanyo GA cells have a charge constant of 1.675 amps. Thus a 3p battery configuration gives a 1C rate of just over 5 amps (5.025 to be exact). So 20 amp charge rate is 3.98C for my battery.

To be clear, I am not a battery expert. My research and talking to people like Justin and others with far more experience than I leads me to believe that charge rates of up to 4C for short bursts won’t be significantly detrimental. But I have no solid data to back this up.
The capital "C" stands for capacity. Since you are putting 20A into a 10Ah pack, you are charging at 2C during regen.

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Re: Radwagon 72v GMAC Phaserunner Build

Post by RSwannabe » Jan 30 2020 10:46am

Thepronghorn - there you go, proving me right when I said I am not a battery expert! You are correct that I am charging at a 2C rate under maximum regen.

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