72V 100A 60Ah 4.3kWh 10s24p 200lbs.....

[16v4nrbrgr]

Dude, I'm a Mechanical Engineer, and have taken many courses on digital and analog electronic circuits, as well as electric powertrain systems. If you simply refuse to accept any advice I have for you, then that's okay, but realize that you need to understand completely what the limitations are of your electric drivetrain and power control systems are BEFORE hooking up any wires, or the components will either let the smoke out, or not last the duration advertised if used improperly. If you keep everything within specs, they can be virtually maintenance-free for years.

If you do this type of crap to anyone offering you advice based on experience and education, then I'm sure that you will make a lot of avoidable mistakes being hard headed and ignorant of the truth. Open your mind and learn from others, and you can achieve anything, that's what I have learned anyways. Abandon your ego for a minute and read some spec sheets thoroughly, understand all of the information presented, do the math for your particular schematic, THEN buy stuff and hook up wires.

 

[miked826]

Dude, I'm a Mechanical Engineer, and have taken many courses on digital and analog electronic circuits, as well as electric powertrain systems. If you simply refuse to accept any advice I have for you, then that's okay, but realize that you need to understand completely what the limitations are of your electric drivetrain and power control systems are BEFORE hooking up any wires, or the components will either let the smoke out, or not last the duration advertised if used improperly. If you keep everything within specs, they can be virtually maintenance-free for years.

If you do this type of crap to anyone offering you advice based on experience and education, then I'm sure that you will make a lot of avoidable mistakes being hard headed and ignorant of the truth. Open your mind and learn from others, and you can achieve anything, that's what I have learned anyways. Abandon your ego for a minute and read some spec sheets thoroughly, understand all of the information presented, do the math for your particular schematic, THEN buy stuff and hook up wires.

I said it once and I'll say it again:

"So if I pour 12 gallons of water through 1 hose then pour 12 gallons of water through 10 of the exact same hoses tied together side by side, then you're saying that the water pressure at the other end of the 1 hose and the water pressure at the other end of the 10 hoses tied together will be exactly the same?"

I really don't need to say anymore than that because the notion that the above is possible is just ridiculous and ludicrous.

 

[miked826]

Dude, I'm a Mechanical Engineer, and have taken many courses on digital and analog electronic circuits, as well as electric powertrain systems. If you simply refuse to accept any advice I have for you, then that's okay, but realize that you need to understand completely what the limitations are of your electric drivetrain and power control systems are BEFORE hooking up any wires, or the components will either let the smoke out, or not last the duration advertised if used improperly. If you keep everything within specs, they can be virtually maintenance-free for years.

If you do this type of crap to anyone offering you advice based on experience and education, then I'm sure that you will make a lot of avoidable mistakes being hard headed and ignorant of the truth. Open your mind and learn from others, and you can achieve anything, that's what I have learned anyways. Abandon your ego for a minute and read some spec sheets thoroughly, understand all of the information presented, do the math for your particular schematic, THEN buy stuff and hook up wires.

Take a nice long look at this pic. A nice long look.

 

[Mike B]

What 16V is saying is correct, current is equal in a series circuit. Those batteries are suspect though if continuous current is only .3C. Most of the batteries I have seen are rated for 1C.

At low speeds when motor back EMF is low, much less current is drawn from the battery as compared to the current being delivered to the motor as controllers operate as high efficiency switching power converters. This will allow huge amounts of current to flow at low speed for acceleration needs.

If the battery is 70 volts and the load has only 7 volts across it then I can supply 100 amps to the load while only drawing 10 amps from the battery.

 

[16v4nrbrgr]

Back EMF limits current at high motor speeds, so the highest current draw will be accelerating from lower speeds or from a stop. At high motor speeds back EMF limits the current flow so the demand will be lower when the motor is allowed to spool up to top speed with minimal load to minimize the time spent heavily loaded at lower motor speeds, when most of the power is consumed.

The current flow is inversely proportional to motor speed, either way, about 75 of those batteries would be needed if 2000 cycles are expected from them. LiFePO4 is weak in regards to current delivery, Lipo batteries are very strong in this respect, as well as SLA batteries, especially when coupled with supercapacitors to minimize the voltage draw down from the Peukert effect.

DC Controllers are basically just pulse-width modulators, with the duty cycle at full throttle being 100%, the max battery voltage will be supplied to the motor, but the duty cycle is chopped to control motor speed, so max current will be determined by the analog circuit design along with the back EMF from the motor, unless a programmable controller is used with a current limiting function, of course if you need to choke down your current then you are limiting the actual power output of your drivetrain in order to save the batteries from self destructing. Current limiting programming can be used to hook strong batteries to a weak motor to prevent low rpm, high load from frying the motor with excessive amperage, which will toast the winding enamel and short them internally, making the windings a ball of useless copper.

 

[miked826]

What 16V is saying is correct, current is equal in a series circuit. Those batteries are suspect though if continuous current is only .3C. Most of the batteries I have seen are rated for 1C.

At low speeds when motor back EMF is low, much less current is drawn from the battery as compared to the current being delivered to the motor as controllers operate as high efficiency switching power converters. This will allow huge amounts of current to flow at low speed for acceleration needs.

If the battery is 70 volts and the load has only 7 volts across it then I can supply 100 amps to the load while only drawing 10 amps from the battery.

Actually he's only correct for a SINGLE battery. Not 10 of them. If 1 battery can discharge 12A then 10 of them can discharge 120A as the load is spread over 10 batteries.

If you pour 12 gallons through a 10" diameter pipe then the water pressure is gonna be 10x less than pouring 12 gallons though a 1" diameter pipe. That's just called reality. LOL

 

[16v4nrbrgr]

IF in parallel, not series, learn.

 

[miked826]

Back EMF limits current at high motor speeds, so the highest current draw will be accelerating from lower speeds or from a stop. At high motor speeds back EMF limits the current flow so the demand will be lower when the motor is allowed to spool up to top speed with minimal load to minimize the time spent heavily loaded at lower motor speeds, when most of the power is consumed.

The current flow is inversely proportional to motor speed, either way, about 75 of those batteries would be needed if 2000 cycles are expected from them. LiFePO4 is weak in regards to current delivery, Lipo batteries are very strong in this respect, as well as SLA batteries, especially when coupled with supercapacitors to minimize the voltage draw down from the Peukert effect.

DC Controllers are basically just pulse-width modulators, with the duty cycle at full throttle being 100%, the max battery voltage will be supplied to the motor, but the duty cycle is chopped to control motor speed, so max current will be determined by the analog circuit design along with the back EMF from the motor, unless a programmable controller is used with a current limiting function, of course if you need to choke down your current then you are limiting the actual power output of your drivetrain in order to save the batteries from self destructing. Current limiting programming can be used to hook strong batteries to a weak motor to prevent low rpm, high load from frying the motor with excessive amperage, which will toast the winding enamel and short them internally, making the windings a ball of useless copper.

Maybe youre just really over-thinking this? It's really not that hard a concept to grasp. Any Radio Shack employee could explain it to you. LOL

If you pour 12 gallons through a 10" diameter pipe then the water pressure is gonna be 10x less than pouring 12 gallons though a 1" diameter pipe. That's just called reality. LOL

 

[miked826]

I'm not rich by any stretch of the imagination and I don't gamble but I'll will be dumping 300A for up to 30 seconds into my $1100 65V 40Ah 18 LiFePo4 cell battery pack with zero ill affects to that pack or it's cycle life. Without any remorse or hesitation. Let the chips fall where they may.

 

[miked826]

IF in parallel, not series, learn.

You are again confusing "Ah Capacity" with Discharge Rate. Like I already said before. That rule only applies to "Ah Capacity" as clearly shown in this pic that I will put up again.

And you are still ignoring this reality. Not sure why that is. LOL

"If you pour 12 gallons through a 10" diameter pipe then the water pressure is gonna be 10x less than pouring 12 gallons though a 1" diameter pipe."

 

[miked826]

Basically you're saying is that whether I have 1 single battery cell or 100 battery cells wired in "Series" that the Discharge Rating (Amps that can be dumped through the pack) not the Ah Capacity, is going to be exactly the same? Really? LMAO

 

[Mike B]

Yes, exactly.

If a cell is rated at a certain discharge capacity then that's all you get no matter how many you string in series. The same current flows through all the cells because they are all in series. You get more voltage, but not more current.

In parallel you get more current but not more voltage.

Laugh all you want, it's not going to change the laws of physics.

What, you think that if you string 10 cells in series you will get 10X the voltage AND 10X the current?

Now that's really funny.

 

[miked826]

Damn. I be wrong. I needs a higher "C" rated battery. I have erred!

http://www.gizmology.net/batteries.htm

 

[miked826]

Yes, exactly.

If a cell is rated at a certain discharge capacity then that's all you get no matter how many you string in series. The same current flows through all the cells because they are all in series. You get more voltage, but not more current.

In parallel you get more current but not more voltage.

Laugh all you want, it's not going to change the laws of physics.

What, you think that if you string 10 cells in series you will get 10X the voltage AND 10X the current?

Now that's really funny.

No not 10X current. I only expected 1X the current (40Ah).

Damn. I be wrong. I needs a higher "C" rated battery. I have erred in my ways!

http://www.gizmology.net/batteries.htm

 

[miked826]

I sure as the sun rises in the morning, would have done exactly what I said I was gonna do without hesitation and gone up in a ball of flames going down the road. LMAO

 

[miked826]

I can only get momentary 80A maximum out of this battery wired in "Series". 80A @ 65V is nothing to sneeze at, but it's just not what I'm looking for.

 

[miked826]

Chart below clocks the time it takes for a battery to completely discharge itself from a short circuit.

 

[biknut]

I've been eyeing these but I don't know anything about the company.

http://www.bmsbattery.com/87-72v#?1#?1#WebrootPlugIn#?1#?1#PhreshPhish#?1#?1#agtpwd

 

[miked826]

I've been eyeing these but I don't know anything about the company.

http://www.bmsbattery.com/87-72v#?1#?1#WebrootPlugIn#?1#?1#PhreshPhish#?1#?1#agtpwd

I was looking at the same website about 20 minutes ago. I haven't heard anything bad about BMS Battery. They're in China. They're batteries look good and affordable to me. I know their batteries won't be able to handle what I want to throw at them but few LiFePo4 batteries will be able to do so, so it's not saying much.

 

[Mike B]

A 40 amp continuous discharge rating would be what I would expect to see from a 40 AH battery. A 1C rating.

With 2C (80 amp) momentary. That should be fine.

A 12 amp (.3C) rating means a limp battery.