Max rated and phase current for 9,12,18 fet controllers

[amberwolf]

I wonder how voltage influences current capabilities as I am in the process on standardizing all my batteries to 52v/14s. Does this mean I can safely push more amps than I did on 72v as long as I keep the watts the same? Or is it a case of amps is amps no matter the voltage?

Your system will need to be capable of handling the higher battery-side amps it will take to create the same wattage. You can figure the new current by the inverse voltage ratio times the old current.

Meaning, your battery itself must be able to sustain the higher current, and supply the higher peaks, so if you were already maxing out the 72v battery, the 52v will have to be even bigger in capacity for the same c-rate, or use higher c-rate cells.

The BMS and interconnects also have to handle this higher current.

The wiring from battery to controller will have to handle the higher battery-side current, too, as will the ocnnectors.


The motor side stuff may already be fine--depends on whether the controller is going to use higher phase amps or not, to do the same job, and whether that stuff is already able to handle it.

 

[maanebedotten]

I like your idea of standardizing on a 14s/52v battery. There are some rules/laws in parts of the world that limit the voltage to no more than 60v or all kinds of additional safety and handling requirements kick in...that is probably the main reason 52v is becoming so popular. Just for those that don't know, a 14s/52v battery when fully charged will read 58.8 volts.

The rules in my country specifies a max voltage of 48. I guess they mean nominal since 13s batteries are common on bikes available in stores. This however has nothing to do with my decision to standardize on 14s as all my bikes are illegal for other reasons anyway
I mainly do it to be able to reduce the number of batteries and chargers i have to own and maintain. It got a bit ridiculous a while back when I had 36v lifepo and 36-48-52-72v li-ion.

 

[maanebedotten]

Your system will need to be capable

I am very aware how everything from battery to motor needs to be capable of the higher amps.

The specific case is my "joyrider" with mxus3k 3t motor. I run it at 72v(20s) 80A(bat)/200A(phase). It is a scary beast and much faster than I need/want. I rarely go above 40kph (25mph) so 14s is enough for speed. I dont want to lose too much acceleration up to that speed though so I have to up the amps considerably. I have tried it at 14s/50A(bat) which is what my currently highest power 14s battery can push and speed is fine, it just takes forever to get there. The controller is from powervelocity with 18X4110 fets.
How hard do you think I could push it on 14s? I have to get a new battery and if I can use my current controller at 100+ amps I think performance will be good enough while I save up for a more powerful controller matched to my new battery.

 

[Bullfrog]

Just a tid bit of data...no clue how or if it would pertain to your specific controller....the Infineon 18 FET with 4110 FETS comes shipped set to 60A Battery and 160A Phase current. IMO it is capable of more but how much more, I have no data to go on. I run an Infineon 12 FET 3077 FETs set to 50A Battery and 140A phase current...the 3077 FETs are a little more efficient than the 4110s but the 3077 should not be used over about 60v.

Have you considered trying a 10T or 12T MAC? The MAC provides more acceleration per battery amp than any motor available for an ebike. My 12T with a 14s battery and with a tire that is 723mm OD will run 27 mph on flat ground with me standing up. I ride standing up almost all the time due to arthritis in my lower back. A 10T will accelerate just as fast per battery amp and will do 2-3 mph faster but requires more phase amperage to equal the 12T acceleration.

Play with the Grin Tech Motor Simulator and compare your motor to a MAC if you think you might be interested. The MAC acceleration is great but it will only handle about 1,000 watts continuous without overheating. For short periods of time I have pushed 50A Battery/140A Phase at 52v and no problems whatsoever...the clutch and gears hold up just fine. The 1,000 watts continuous equates to about 29-30 mph on flat ground. A 29x2.6" Maxxis Ikon with the 12T MAC runs a little too hot...runs about 140-145F with an ambient temperature of 95F. The 723mm tire I am now running is a Vee Chicane 26x3.5". The 29" Ikon was 752mm OD.

A tire I like a lot is the Schwalbe Super Moto-X...the 27.5x2.8" is rated for more load than any bicycle tire I could find and it is ECE-R75 rated for 50 kph/31mph. The Maxxis Hookworm is another good tire but it is only available in a 26" and 29"...both 2.5" wide.

 

[maanebedotten]

The powervelocity controller has some upgrades that makes it capable of a bit more than most affordable 18x4110 controllers. 10awg wires and thick copper added to the traces. It was advertised as capable of 100 battery amps, now i see their similar model is advertised at 80 amps. My battery can not push more than 80a so I have not been able to try higher.

The mac is a good motor with good performance on low to medium power setups, but the gears will instantly turn to peanutbutter with the kind of power i am used to on this bike.

 

[Bullfrog]

If you are going to a 52v battery it is going to be difficult to get one with more than 50A capability unless you build it or use LiPos. The BMSs that EM3ev and Luna use are limited to 50A or less.

Using the Grin Tech Motor Simulator...I ran the MXUS 4503 against a 10T MAC both with 52v, 50A Battery, and 200A Phase current...neither motor can use over about 165A Phase with a 50A Battery. The MAC will accelerate faster from 0-20 mph than the MXUS. Above 20 mph the MXUS will accelerate faster but only because the MAC is approaching top speed sooner.

I am not positive the MXUS 4503 is your motor but you can easily run yours to compare.

If your goal is to run 25-28 mph then the MAC would be a better choice IMO but if you want to go over 28-30 mph, a hub motor would be better because the MAC will start to get hot. Long climbs and the MAC will get hot as well but for short periods of time you can put 50A through the MAC with no problems. I did run 60A for a little while but my BMS kept turning my battery off...the MAC did fine.

72v is a little too much for the MAC IMO...you can do it but it will get hot if you are not helping by pedaling.

I am not suggesting you buy a new motor...just want you to understand the capabilities of the MAC. With the 5:1 gear reduction it produces FIVE times the peak torque of a similarly sized hub motor or the same torque on 20% of the amperage the hub motor would take for equal torque...in theory. In reality the MAC is smaller than most hub motors so it isn't quite a 5:1 ratio.

As far as the gears and the clutch...I have had mine apart after running 60A for a little while and 50A for months and I can not even detect any wear...much less peanut butter .

 

[maanebedotten]

If you are going to a 52v battery it is going to be difficult to get one with more than 50A capability unless you build it or use LiPos. The BMSs that EM3ev and Luna use are limited to 50A or less.

The only battery manufacturer I trust enough is em3ev, I have several batteries from them and If I can get Paul to custom make a pack for me in the 150-200A range I will definitely consider it. Otherwise I will just make the pack myself. I have a spotwelder and some experience making smaller packs, but I can not match the quality of a pack from em3ev, so I would prefer to pay a lot more for a pack from them. The rigidness and cell-level fusing their technology provides is hard to match in a DIY build.

Using the Grin Tech Motor Simulator...I ran the MXUS 4503 against a 10T MAC both with 52v, 50A Battery, and 200A Phase current...neither motor can use over about 165A Phase with a 50A Battery. The MAC will accelerate faster from 0-20 mph than the MXUS. Above 20 mph the MXUS will accelerate faster but only because the MAC is approaching top speed sooner.

If you read my post, you will see that i am not at all happy with the performance I get from 52v/50a. It is after all less than half the power I am used to at 72v/80a. Even if I was happy with that power, the mac would just not be enough, I am fat and my bike is heavy so no geared hub will last long. Per the calculator the 10t mac ends up at over 90 degrees C even on flat land at 25mph so it is just not an option at all for this bike. I do love the geared hubbies though, I am very happy with my bpm2 on a different bike, and the mac is even a bit better, but for heavier bikes and speeds above 20mph they just can not cope with the load over time. Even if the mac could take 100A it would not be able to touch the performance of my mxus above 10 mph. Punch off the line is fun, but considering I spend at least 90% of my riding time above 10mph I value 10-25mph performance more.

I am not positive the MXUS 4503 is your motor but you can easily run yours to compare.

That is my exact motor. I have it in a 19" mc rim with a 3.5" tire making it effectively about 25"-26" diameter. Total weight of me+ bike is at least 130kg, maybe more. I have not weighed either in a good while I also often ride with a passenger so everything has to be able to cope with 200kg total weight. After spending hours on the motor calculator I realize it will be hard to get the performance I want with 52v so long term I might have to look for motor options or just keep this bike at higher voltage.

 

[Bullfrog]

You can safely run the MAC up to about 145C...I have run mine for a couple hours between 145-150C when I had it in a 29" rim with a 29x2.6" Maxxis Ikon tire. I always tried to keep mine below 110C until Justin at Grin Tech told me he had run a MAC on his dyno at 145C and did not have any degradation. No guarantees if you exceed 150C :lol: . My bike and I together weigh 125 Kg if it is before lunch :lol: .

A Direct Drive is a lot better for continuous high amperage...no argument there.

I wish you luck with the custom battery from EM3ev I have not been able to get them to produce anything "custom".

I agree they make the best and that is the only manufacturer I currently use.

EM3ev does offer a connector where you can run two of their batteries in parallel...I have not tried it yet but that might be an option if you have a controller that can handle the amperage.

 

[maanebedotten]

I have considered running several 50A packs in paralell for higher amps, but knowing myself it is only a matter of time before I eventually hook up a fully charged pack to an empty one.

The parallel harness from em3ev is only 60A max. I asked if they could make a 100A one for me but no luck. I assume it is just some diodes to prevent high current between packs so I could probably make one myself, but I have not researched it enough to know if there are any safety issues. I do have this nasty habit of doing foolish stuff from time to time so I try to make my stuff as foolproof as possible. Taking standardization to the next level by only having similar 50A packs and paralleling as needed for more power is the ultimate dream so I must read up on the subject.

I don't have high hopes Em3ev will do a custom pack for me , but have not asked yet. They used to have a 72v 80a shrink-wrapped pack listed with a non-smart bms, but it is no longer on the site. I think they don't want to deal with high power stuff in general.

 

[Bullfrog]

"doing foolish stuff from time to time"....I resemble that remark :lol: .

Just so I don't mislead anyone reading my post about the MAC temperatures...If anybody wants to run a MAC motor, I recommend running your parameters through the Grin Tech Motor Simulator and although you can run a MAC at 145C, I would highly recommend you don't do anything that has a predicted temperature above about 130C steady state. The motor simulator gives you steady state temperatures. You need a little room in case you hit an incline, a strong headwind, or you loan your bike to someone that is heavier than you are. The MAC can easily increase 20C if you are riding along on flat ground at 130C and climb a long fairly steep hill. I use 1.5% grade just to give me a little extra room and still try to stay below a predicted temp of 130C .

Just had to cover my ass :wink: .

 

[maanebedotten]

To get this thread back on topic:
How does phase current come into play? If set equal to battery current, will this allow higher battery currents?

 

[Bullfrog]

Phase current is three interlaced Sine waves a 120 degrees apart. Battery current is just the sum of the three phase currents at any point in time. Both the battery and phase currents can be the limiting factor depending on your battery, controller, and how your controller settings.

Regarding your question, a low phase amperage setting will limit battery amperage and a low battery amperage setting will limit phase amperage. Your controller just takes the battery amperage and sends it to the three phase wires at the appropriate time...the total power (battery voltage X battery amperage) can never be more than what your battery is supplying. Your controller drops the voltage and increases the amperage...that is how you can have more phase amperage than battery amperage...but the total power (VxA) can not be increased.

For instance your 4503 MXUS motor...with a 52v battery and a controller set to 50A Battery and 160A Phase....at zero rpms the motor draws about 45A battery and 160A phase currents with the phase amperage being the limiting factor. Once the motor start turning the phase amperage almost immediately starts dropping and the 50A battery setting becomes the limiting factor.

This is a very generalized statement but usually the phase current is the limiting factor at low rpms and the battery amperage is the limiting factor at high rpms assuming an "average" set up. If you change the voltage or severely limit the battery current or the phase current things can change.

There is a lot of good info on the Grin Tech web site under the "Learn" tab: https://www.ebikes.ca/learn.html Justin (Grin Tech founder/owner) is one of the sharpest guys I have come across regarding electric motors.