Remaining noob questions after reading all noob guides

[gaf]

I'm building up a front-hub direct drive kit around my cromoly Surly Cross Check. Buying from ebikes.ca, so it's either the Crystalyte HS35 or the 9C 2807. Here are the things I still don't understand after 2 weeks of reading ES, our wiki, and ebikes.ca's guides and simulator.

1. Ping Battery says this about the 60V 10Ah LiFePO4 I was looking at: "Max Continuous Discharging Amperage: 20 Amps". and "Discharging Cut-off Protection: 30 Amps"
I was going to buy one of their 60V 10AH batteries to use with the 25A Infineon controller that comes as an upgrade to the 9C 2807. What happens if the controller tries to draw (continuously) more than 20A from the battery? The simulator puts my setup at 21 amps at 100% throttle at 0% grade, but at 30 amps for a 6% grade. Do I need to be concerned about this stuff for the sake of my battery, or does the controller sort it out? The wiki guide says this "a higher total capacity is needed to keep the C-rate low enough (e.g. with a 25A controller, get at least 15 Ah)". Can someone explain this?

2. How can one determine how much time it will take for a given battery to charge? Ping sells a 2.5A, 4.5A, and 7.5A charger. Is the 7.5 going to charge 3x as fast as the 2.5?

 

[maurtis]

1) The controller does not know the C rate of your batteries and tries to take what it needs. In this case, would be exceeding the max continuous C rating by a small amount. So I think that means the batteries would provide the power, but at the cost of greatly reducing their lifespan? Not sure, but I would definitely go with at least a 15AH battery for that controller to be safe.

2) Correct. If you have the 15AH battery and use half of the capacity (7.5AH), it would take a 2.5A charger 3 hours to push that back in. Or a 7.5A charger 1 hour.

 

[FfredDRredD]

good questions, nice research, looking forward to answers because i don't know either

 

[Supertux1]

1. The battery BMS has a cutoff circuit and so does the controller.

Whichever one you hit first is going to cut your power, and hopefully before anything gets damaged.
Ideally you want the battery BMS to a good deal more than the controller so that $100 part protects the $1000 part and not the other-way around.

Keep in mind that it takes an enormous amount of power to accelerate from a stop than it does to cruise along at a constant speed.
It may be fine if you pedal a bunch and then apply throttle, but I would be worried about it cutting out if you gunned it from a stop.

Even a slight grade is going to push your 10A setup to the maximum, so I would definitely consider the 15Ah battery because it will provide more overhead for those spikes that you'll get when accelerating from a stop or going up hills. Pair it with a CA with appropriate limiting and you can't go wrong.

2. Charging time depends on the cell chemistry and the efficiency of the charger. It's somewhat linear but gains taper off the higher you go, because cell resistance causes energy to be wasted as heat the higher the charge rate is. Fast charging limits your cell life just as much as fast discharging does. Slow and steady is best, if you have the time. If you want to really balance the cells it require leaving on the charger quite a long time no matter what rate you charge at.

 

[el_walto]

You can use a 15Ah or higher ping battery with a 25amp controller. A 25amp controller will limit the current draw of the entire system to 25amps, so it will not damage the battery. 25A/1500W is the max the bike will use, it will only use this much power while accelerating or going up hills.

If you get a 10Ah battery, you really should get a 20amp or less controller giving you 20A/1200Watts of power. If you run a 25amp or higher controller, you will quickly damage the battery.

Consider switching to a 48V 15Ah ping pack. 48V x 25amp controller - 1200W ebike. This is a good setup for a first front weel bike.

 

[arkmundi]

I'm building up a front-hub direct drive kit around my cromoly Surly Cross Check. Buying from ebikes.ca, so it's either the Crystalyte HS35 or the 9C 2807. Here are the things I still don't understand after 2 weeks of reading ES, our wiki, and ebikes.ca's guides and simulator.

Congrats on joining the ES community and consulting the guides BEFORE posting - you are a rare and exceptional person! And welcome!

1. Ping Battery says this about the 60V 10Ah LiFePO4 I was looking at: "Max Continuous Discharging Amperage: 20 Amps". and "Discharging Cut-off Protection: 30 Amps"
I was going to buy one of their 60V 10AH batteries to use with the 25A Infineon controller that comes as an upgrade to the 9C 2807. What happens if the controller tries to draw (continuously) more than 20A from the battery? The simulator puts my setup at 21 amps at 100% throttle at 0% grade, but at 30 amps for a 6% grade. Do I need to be concerned about this stuff for the sake of my battery, or does the controller sort it out? The wiki guide says this "a higher total capacity is needed to keep the C-rate low enough (e.g. with a 25A controller, get at least 15 Ah)". Can someone explain this?

Its not well understood that increasing the capacity of your battery, increases both the stored amp-hours AND the delivered amps on the draw down. But, limited by the BMS, which Ping does include with your battery. Its a good group, battery & BMS. I'd tell them exactly what motor you're driving and take what they recommend. Yes, a 15 amp or 20 amp battery would be better. But for the motor & controller you're getting, I believe you'll be OK. If motor, controller and BMS are all rated at 30 amp max, which I believe they are.

2. How can one determine how much time it will take for a given battery to charge? Ping sells a 2.5A, 4.5A, and 7.5A charger. Is the 7.5 going to charge 3x as fast as the 2.5?

Yes. Get a really good charger. There are a variety of chargers available on the market. You can take the one Ping gives you, or go to batteryspace.com or others. Pay for a quality charger. Get a good bulk charger, not a balance charger, as the Ping BMS will take care of the over-charge circuits and balancing for you.

 

[RoadWrinkle]

I know you did not ask this, but thought I would mention with the cromo set-up (forks two) you most likely have forged dropouts so you will be able to safely run the torque your hub motor will produce, but I would still invest in some good (both sides) torque arms so you can run around without worrying about a catastrophic front end failure (assuming you have a good front wheel and spoke tension). :wink:

 

[dogman dan]

10 ah ping with a 20 amps controller can work, but it will wear out faster than a 15 ah. If you ride hard, it could be very fast.

My experience leads me to invariably recommend at least 15 ah pingbattery with a 20 amps controller.

 

[gaf]

I know you did not ask this, but thought I would mention with the cromo set-up (forks two) you most likely have forged dropouts so you will be able to safely run the torque your hub motor will produce, but I would still invest in some good (both sides) torque arms so you can run around without worrying about a catastrophic front end failure (assuming you have a good front wheel and spoke tension). :wink:

Yes, of course. That is not a thing I'd enjoy worrying about. I didn't know it was even possible to run a front hub with no torque arm.

Thanks everyone for the responses. It sounds from your advice like I could probably buy the 60V 10Ah Ping if I had to, but that spending too much time above 20 amps (by encountering even slight grades daily) would hurt its lifespan, either a little or significantly depending. However it also sounds like I could prevent this by using the Cycle Analyst's current limiter. The 48V 15Ah is tempting since it means I get to keep my warranty, ebikes.ca doesn't warranty hubmotors run above 48V.

Can someone link me to a LiPo battery that is similar to the Ping 60V ones? I am having trouble sorting through Hobbyking's site. I can probably manage charging one without exploding it, and will get a battery fireproof case in the event I do. I can't really afford the 15Ah 60V Ping, and I'm already giving up one of the main advantages of the LiFe bat if I run it close to its current cut-off often.

Consider switching to a 48V 15Ah ping pack. 48V x 25amp controller - 1200W ebike. This is a good setup for a first front weel bike.

Yes, I will consider this.

1. The battery BMS has a cutoff circuit and so does the controller.

Whichever one you hit first is going to cut your power, and hopefully before anything gets damaged.
Ideally you want the battery BMS to a good deal more than the controller so that $100 part protects the $1000 part and not the other-way around.

Keep in mind that it takes an enormous amount of power to accelerate from a stop than it does to cruise along at a constant speed.
It may be fine if you pedal a bunch and then apply throttle, but I would be worried about it cutting out if you gunned it from a stop.

Even a slight grade is going to push your 10A setup to the maximum, so I would definitely consider the 15Ah battery because it will provide more overhead for those spikes that you'll get when accelerating from a stop or going up hills. Pair it with a CA with appropriate limiting and you can't go wrong.

2. Charging time depends on the cell chemistry and the efficiency of the charger. It's somewhat linear but gains taper off the higher you go, because cell resistance causes energy to be wasted as heat the higher the charge rate is. Fast charging limits your cell life just as much as fast discharging does. Slow and steady is best, if you have the time. If you want to really balance the cells it require leaving on the charger quite a long time no matter what rate you charge at.

Three excellent points, thank you. None of this had really occurred to me.
Unfortunately, if I take this bike out on tour, or do an intercity jaunt downstate, I'll have to charge as quickly as possible. It seems likely I'll be abusing this first battery, and I wonder if I should be investing in a Ping.

 

[gaf]

Its not well understood that increasing the capacity of your battery, increases both the stored amp-hours AND the delivered amps on the draw down. But, limited by the BMS, which Ping does include with your battery. Its a good group, battery & BMS. I'd tell them exactly what motor you're driving and take what they recommend. Yes, a 15 amp or 20 amp battery would be better. But for the motor & controller you're getting, I believe you'll be OK. If motor, controller and BMS are all rated at 30 amp max, which I believe they are.

Interesting. It is apparent I'm in the grey area of this battery's specs.
I'll shoot Ping an e-mail and post his/their response here.

Last question. What's usual etiquette on plugging your battery in at restaurants, stores, hotel lobbys? Do you offer fifty cents, do you say anything at all?

 

[arkmundi]

Last question. What's usual etiquette on plugging your battery in at restaurants, stores, hotel lobbys? Do you offer fifty cents, do you say anything at all?

I only charge at home. The cost of a typical charge of my AMP20 12S 36V battery is pennies, however. Many cafes offer electrical outlets so patrons can charge their phones. If an outlet is available, I'd just use it. But having enough battery capacity for your daily run is best.

Unfortunately, if I take this bike out on tour, or do an intercity jaunt downstate, I'll have to charge as quickly as possible. It seems likely I'll be abusing this first battery, and I wonder if I should be investing in a Ping.

Ah, I see. Yes, invest in the Ping, or one from em3ev.. Get a good LiFePO4 battery. Stay away from LiPo.

Mind you, that all Lithium cells have a C-rate, the amount of current they can stand without degradation on charge and discharge. You'll typically see something like 2C. This means it can go 2-times its amperage rating. So a 15ah battery can suck up or discharge 30 amps. If your charger is 7.5 amps, you see you're in the safe zone. When you buy a battery, read the data specifications and be aware of how far you can safely push it. The battery is the most cost intensive piece of your ebike and you'll want to protect your investment by extending its longevity. Don't abuse it.

 

[Ykick]

Is it too much to ask roughly "where" you may be located? You mentioned "state" but why do we need to screen your posts for clues and "guess"?

Several of us are frustrated and ready to boycott advice to people who're unwilling to offer basic logistics of needs regarding purchase/operation.

Nobody's looking to find your front door but country/continent and general geographic area seems the least people seeking advice can provide, IMO....

 

[gaf]

Is it too much to ask roughly "where" you may be located? You mentioned "state" but why do we need to screen your posts for clues and "guess"?

Several of us are frustrated and ready to boycott advice to people who're unwilling to offer basic logistics of needs regarding purchase/operation.

Nobody's looking to find your front door but country/continent and general geographic area seems the least people seeking advice can provide, IMO....

Sorry! I could have sworn I updated my phpbb profile but it is clear I did not. I am in Chicago, Illinois. This is an extremely reasonable request. Chicago is completely flat, but strong winds off the lake are common.

 

[mrzed]

A 60v 2807 is too fast for a front hub, IMO. I say this having run a 2807 front on a 48v/15ah ping. I found that slightly too fast and too harsh with no suspension on all but the smoothest roads. I've since moved to a rear drive with a shock up front and it is so much better. I liked my 2907 front better on a rigid fork run at 36v, because then at least the lower speed meant the lack of suspension mattered less.

 

[dogman dan]

I tend to agree with that. For a daily rider, 48v, that is charges to 58-60v, and runs mostly at 52-55v is plenty for a 2807.

It will work fine with a 20-25 amps controller and a 48v 15 ah ping. That's real world advice from thousands of miles doing it. The 60v would be a huge pig to carry anyway.

Your cruising top speed will be about 27 mph, and pull about 800w, easily handled by the 15 ah ping. Starts and stops will make amp spikes, but a reasonable controller will keep them from exceeding 2c. Max amps with a typical 22 amps controller is 1200w. Plenty when you need to get moving in traffic.

FWIW, I did those thousands of miles using a shock fork and front hub. Even with the shock, I came to prefer riding between 20-25 mph. Mostly this was finding I could enjoy the ride at 20 mph, while at 27 mph I was just scanning desperately for the next broken bottle.

It depends on your ride length, I still love to ride 32 mph for short runs. But the 15 mile ride to work got tiring at faster speeds. Slowing down and taking longer was actually easier for me.