Reconfigure Ping LiFePo4 battery?

[GCinDC]

Hi folks, Newbie here. I love this forum!

So, I have a 48V 500 Watt Golden Motors kit and Ping 48V 12Ah battery (his suggestion, per my kit).

My daily ride is only (2 x) 5 miles. (A couple of 10% hills on the way.)

Do I have too much battery for that distance? Could I reconfigure the pack for a higher voltage? If so, how??? They're the prismatic poptarts.

Thanks for your thoughts,

-GCinDC

[cerewa]

to the best of my knowlege, your pack consists of cells that are 4Ah, nominal voltage 3V. (actual operating voltage closer to 3.1V to 3.4V) If that's true, you could set it up as 72V 8Ah provided you had an appropriate BMS or some other way to avoid over-discharging individual cells.

The useable C rate of your battery depends partly on how long you want it to last. With a 72V setup, you're more likely to run at fairly high amperage on the flats (at higher speed more torque/more amps will be consumed in overcoming wind resistance, for one thing) and you're more likely to run at even higher amperage on uphills.

If the C rate (peak C rate and typical C rate) is reasonable, then you've got no problem. Well, provided you have a controller that can handle the voltage and you avoid overheating your motor.

[GCinDC]

Thanks! It's very tempting.

Ping told me my pack cells were 2C. I'd asked about another pack later, and he said he could sell a cheaper one, but it was last year's 1C cells...

I never understood how the tool battery packs can be made so powerful. I'm thinking of rigs like this: http://www.evalbum.com/1664

I'll see if I can take a pick with some duct tape peeled back. I have no idea how hard this would be.

[dogman dan]

I disagree with Ping, you can never have too much battery, unless it gets hard to carry. You can never run a battery at too shallow a depth of discharge. You can never run a battery at too low a c rate. Asuming you average 15 amps discharge rate, you already are slightly over 1 c. While Ping says 2 c is ok, I will say show me the test data, because all I see is test data for 1c. Be assured that higher c rates are likey to cost you cycles. Unfortunately we don't have an inexpensive 20 cell bms avaliable. If we did, ping would be able to offer higher voltage batteries. Since your ride is short, maybe 1 sla with the sla between the ping and the controller in series so the bms only passes 48v? So Ping, then the sla, then the controller?

[GCinDC]

I was unclear. Ping didn't recommend a battery smaller than 12 Ah for my 48V 500Watt kit. He only offered the 1C as a cheaper option for a SMALLER kit for my wife...

Anyway, I'm still trying to understand Volts, Amps, Watts, etc... so pardon my ignorance!

I get that higher V= higher speed.
I get that bigger motors pull more amps (like uphill), and also that more Ah are needed for longer rides.

But I'm not coming close to draining mine on a commute! So I was wondering if I could reconfigure the battery to optimize it...

...to the best of my knowlege, your pack consists of cells that are 4Ah, nominal voltage 3V...

cerewa, would that mean that there are only 3, to make up the full 12Ah? When I peeked under the tape, I saw tons of very thin ones, much thiner than real pop tarts...

The useable C rate of your battery depends partly on how long you want it to last. With a 72V setup, you're more likely to run at fairly high amperage on the flats (at higher speed more torque/more amps will be consumed in overcoming wind resistance, for one thing) and you're more likely to run at even higher amperage on uphills.

If I'm only using 1/3 of the battery each day, and recharge every night, will I more likely get 3 X 1000 cycles?

I'm just trying to understand this: to climb a steep hill, the motor needs x Amps. A battery smaller than 12Ah might not be able to deliver, but also will have plenty left over after that hill... ?

dogman, I was trying to think of how to get more speed out of the SAME battery, since I'm not using all of it. or am i?!

Thanks!

[cerewa]

cerewa, would that mean that there are only 3, to make up the full 12Ah? When I peeked under the tape, I saw tons of very thin ones, much thiner than real pop tarts...

Each cell may be folded over on itself several times.

A 48V12Ah pack that's made of 3V4Ah cells must be set up as 16-series x 3-parallel for a total of 48 cells. (note, most packs do not have the same number of cells as their voltage.. just a coincidence)

[dogman dan]

Mind boggling at first eh? I'm still a moron too compared to others here but I have understood some good rules of thumb to go by.

Basicly I'm trying to say, push the battery harder and it is likely to wear out faster. You now have the minimum amp hour size battery to power the motor. If you take it and reconfigure the battery to a higher voltage, you will cut the amp hour size in by one third. The strain on each cell will be one third more. This could be disasterous to the life cycle of the pack. A bigger amp hour size will make the pack last longer, since the strain on each cell is less.

You have 3 , 4 amp hour sub cells in each 3.4v cell in the battery. You could take one sub cell off each cell, and make more two pouch cells and have more volts, but you need a bms, and 16 cell is the biggest one that is not expensive. Surely this will change soon, but not yet that I know about. But anyway, you would still be risking a short lifespan if you make the battery any smaller in amp hours that it is now, even if it is the same number of cells.

As for your length of ride, and recharging. You will be riding farther than you do now, trust me on that. Your routine ride will stay the same, but you will find excuses to take the long way home when the weather gets real nice. Recharging after using just a portion of the capacity is a real good thing. You may double the number of cycles if you use less than 50% each ride. If you use only 33% each cycle, you may very well see 3000 cycles, IF, the discharge rate doesn't go too high. Since you are already using the minimum amp hour size, you may only see 2000-2500 cycles. Its gonna take you years.

Your battery is already optimum for your bike, and in my opinion, a bit small, I'd consider a 16 ah one the optimum, and 20 ah the gold standard. The bigger ah packs will simply last longer, and in the end be cheaper. I thought I had just the right size for my ride, but in colder weather, I found myself pedaling home the last mile with the battery dead a lot. I hadn't given any thought to two things, cold weather cutting my range, and seasonal wind direction. So I harp a lot about no such thing as too big a battery. To go higher voltage you need to go higher voltage and higher amp hour size because the wind drag is going to make the motor pull more amps. A good rule of thumb is one ah ping battery to each amp the controller pulls on average. That keeps you at 1 c. The way to find out the c rate without a meter is to time a ride and ride till the pack is used up. If it takes one hour, you are riding at 1c. If it takes longer, you are under 1c, yay, your battery will last longer. If it takes less than an hour, you are riding at greater than one 1c.

Do you need a battery for your wifes bike? Could it use the 48v ping? If so, maybe you would enjoy nicad batteries or nimh. No need for bms with those so get two 36v packs from ebikes-ca and go for 72v. Those batteries can tolerate the discharge rate better than duct tape lifepo4, so you can get away with a pretty small pack, like 10 ah or so. By the time they wear out, the choices in lifepo4 or lipoly may improve a lot! Maybe even supercaps by then?

[GCinDC]

Oh man, thanks for writing all that out, dogman!

It's starting to make more sense. I'm very glad to hear that my routine usage will lengthen it's life. I hoped so, but didn't know! And also that it's good I recharge it frequently. I've honestly been afraid to drain it! I guess I'll know when it gets really low, but I've heard of dark and unpleasant things happening to batteries at that point. Or will the "low voltage cutoff" protect a ping battery...?

I've definitely felt the power difference in cold weather. Ping told me there would be no ill effect until WAY below freezing... Is that true? I know it probably is for other batteries. If so, I'll bring her in at night!

Part of the reason I started this thread was because I keep reading (jealously) about the toolpack batteries, and don't understand the differences... how they get away with fewer Ah. I should have posted this under the battery forum I just discovered... But your line answers that:

"Those batteries can tolerate the discharge rate better than duct tape lifepo4, so you can get away with a pretty small pack, like 10 ah or so."

Maybe the next project.

I got my wife a BionX 250PL. I'd originally bought the 48V GM kit for her, thinking about steep hills and pulling trailers (we both have child seats on ours), but the whole thing was way to heavy for her and she wanted the exercise and ONLY used the motor up hills, so she was really getting a workout. Good news, because I'd fallen in love with the thing, and just needed to get her rigged up so I could have it. I was about to get her a BMC and lifepo4, but realized the price was already up in BionX territory, and a good deal on eBay popped up...

Now it's time to start designing a new battery case! I need to be able to lock the bike up in the city and need something more secure than black bag attached w/ velcro...

PS. It snowed here this morning and my brand new schwalbe snow tire clawed the ground all the way in to work!

[dogman dan]

Well now you are stuck with a good battery that will last at least 10,000 miles and possibly double that. Very likely the motor wears out first. Go for a long ride once in a while, like 2 or three times a year, to see if your pack has degraded. The lvc will protect it from damage as long as you discharge with bms. I've run mine down lots of times now that cold weather came, and the tailwind switched to headwind for the season. My new motor, brushless, really helped with that. I needed a lot of battery to run the brushed motor.

I find the battery has the most loss of range well below freezing. Just what happens if I leave the battery in the garage, or put the bike on the bus bike rack for a few miles. If I bothered to bring in the battery, I'd lose a lot less range. Sla's would be the cheapest way for you to play with higher voltage, but nicad or nimh would be the easiest to carry all the time.

Pings have pretty good resale value, but you won't get all your money back from sphere sharks. You might consider selling the whole thing as a complete bike localy when spring comes, If you get the bux back out, fine, if not , keep riding it. If you did cash out ok, you could start over with a 5304 and high voltage of psi cells for speed.

Old metal toolboxes are my choice for battery case. They can take some hunting to find. To protect the battery in a bag, you can take an aluminum cookie sheet, and cut the corners so you can bend it around the battery into a form fitting box with no top. It saved my ping in a crash ! Now I have the aluminum wrap, inside the metal box.

[GCinDC]

Since your post, it's been a busy morning for me reading up on the PSI threads... Thanks!

I'm happy for now. It'll take me a while to make sense of all this...

I've got to make the ideal battery case. And now that I've got the snow tires, the next thing will be getting a Cycle Analyst..

[dogman dan]

Another poor sucker hopelessly hooked on ebikes, and now reading the sphere too.

[GCinDC]

Man, I can't believe how much great stuff is up here. I'm inspired to start photo-journaling this obsession! The photos are like a movie: That guy's burnt finger... The package just arriving from china... hahaha... i'm hooked.

My wife saw me typing last night and asked me what I was doing. I think she was jealous...

[Almasi]

I never understood how the tool battery packs can be made so powerful. I'm thinking of rigs like this: http://www.evalbum.com/1664

Hey, That's my bike

I can say that I love my A123 setup (2 pack of 30 Cell,made in 10S3P that I can put series or parrallel) Even in very cold wheater (I drove it for 2 hours at -15 Celcius (5 degree Fahrenheit)) it was as good as it get in Summer (the bike was stored inside prior de ride...so the battery started warm.)

For my next bike I consider Lipo for their weight...but I'm affraid to burn the house while charging this inside otherwise I will stay with A123 because I have full confidence in them. (My friend left is bike 'ON' for over 3 months and that took the whole pack down to 3 volt for a 20S3P A123 setup...I was sure he killed all the cells...but after charging them I went for a ride... still had all the pack capacity (measured by the CycleAnalyst display)...they are AMAZING CELL)

There is one thing about the Ping pack, I consider one as a Extra pack for long ride, there are very cheap compared to A123 + charger setup, an look reliable from all the feedback I read.

Robin