selecting battery

[cleanair]

Hi all, I set up a full suspension mtb with a 35 amp controller. Things I need from my setup:

* max speed: 28~32 mph (w/o pedal)
* range: about 25 m roundtrip (w/o pedal)
* type of ride: flat city commute
* carry trailer w/child (pedal assist)

I think for all I need I should hook my bike to a 110V AC outlet!!!! (plus an AC/DC converter :lol: )

Jokes aside, a powerful Lifepo4 pack, like Ping's 30ah, should do it. However, my concern is weight = 33 lb.! Can hardly imagine making turns!

If say I go for a Lifepo4 15ah pack, like Juiced Riders' (3/5C), yes much better weight @ 16.5 lb, but worried about stressing out the pack and range limited to a few blocks :wink:

Any thoughts?

 

[morph999]

at 30 mph, I tend to use about 1 AH per mile so you'll need about 25 AH at least. If you only go about 18 mph, you use less battery.

 

[dogman dan]

I gotta major problem with your plan to ride 30 mph with a kid in the trailer for one. But your kid, your decision.

That kinda range at that speed, you'll need at least a 48v 20 ah battery for sure. That would for sure be big enough if you slow down to a reasonable speed for trailering. I have no experience with trailers, but I can't imagine it being very safe above 15-20 mph. Even if it's just the big ol battery in there.

I carry a 48v 15 ah ping and a 36v 20 ah ping for long rides, and on my bike with 30 pounds on the rear rack, turns are made slow and carefully. But on the straight line, it's tolerable at 25 mph. When I carry both batteries, I tend to ride 15 mph to get range into the 60 mile or more area. At full speed, I'd still have about 45 miles at 25 mph.

Back to the speed issue, you might need a bit more than 48v to get above 30 mph anyway. Possibly one of pings 60v 20 ah batteries if you have a 72v controller?

On the other hand, if you have a crystalyte 5303 or 5304, you'd need 30 ah of ping to run the big motor and controller anyway. Or a battery with a higher c rate.

 

[cleanair]

dogman, part of my daily commute is to my son's daycare. trailer & kid stay there, and of course ride should be at safe speed, some pedaling to set the example :wink: .

Max speed is for the daycare-to-work part (still should be safe).

going back to my setup, I've got a 9C 2806 on 26in. Are you still suggesting Ping's 30ah?

What about Juiced Riders 15ah's this one is rated 5C w/3C cutoff.?

 

[morph999]

you still might need more than 20AH. I did 19 miles today with heavy pedaling on almost 10 AH of battery used. I have a 20AH battery, though. If you want to do it without pedaling, you'll need probably 30AH battery. Unless you can charge it at your work? If you can charge it at work, then you can get a smaller one. Lithium has 90 - 95 % usuable capacity but I'd only buy a pack where you are using between 50 - 80 % of it because it will last longer.

If your trip is 15 miles to work, then you recharge, and do 15 miles back. You can get away with a 20AH battery easily. If they won't let you recharge at work, you'll need a 30 AH battery probably unless you want to do 50 % pedaling and a slower speed.

 

[amberwolf]

Do you have any batteries you can test the setup with now? Even if you just put them in the trailer with long wires, for the test? Plus a watt meter?

Then you can find out how much power your setup will actually take at the speeds you want, with the trailer (including an equivalent weight load in it to what it will need to carry), and can then buy a battery that will satisfy you.

Realistically I doubt you will be able to get away with less than a 30Ah battery depending on how many miles at higher speeds you need to go with that trailer attached. The trailer will likely double the amount of power your bike alone takes, depending on it's rolling resistance and frontal area/aerodynamics, at higher speeds.

Also, if you have lots of stops and starts for traffic controls, it's going to seriously eat into your battery, if you are not helping it by pedalling at least a little--starting from a complete stop with a trailer (extra weight and rolling resistance, primarily) will take significant power.

 

[USAEBIKECO]

Looking at your specs you should buy a vpower lifepo4 48 volt 20 ah battery for around $600

I personally wouldnt go 48 volts because I feel its just too fast for a bicycle.

 

[cleanair]

Thanks amberwolf.

I did a test ride w/an old lithim-ion batt (37V 10ah 1C). It looks like the thing is swallowing all 35amps to start... once running, not less than 20~25amps. (w/o trailer).

So technically speaking, I should be able to play around w/my CA (drain brain) and limit amps to prefered current, depending on riding conditions (road, wind, weight, etc.).

If I limit current drain through my CA, perhaps the 15ah (5C-BMS limited to 45amps) pack could still be an option...

 

[dogman dan]

15 ah of 5c cells in a 48v pack will run the motor fine. To get 45 amps you'd need only 3c discharge rate, so no need to limit amps. But to get long range at full speed, you'll need a big front gear so you can set a speed and pedal a bit faster than that to lower the amps the motor uses. 25 mile range is likely to be there at 25 mph, but at 30 mph you'd need about 48v 20 ah.

 

[icecube57]

On my bike i can get about 50m unassisted at 22-23. I have 60v 20AH Thundersky battery pack. If i ride constant wide open throttle I can do 35mph and do 25 miles unassisted. That 9C is more efficient than my Golden motor. When I ran my Golden Motor at 48v I was sipping .6AH a mile on the flats at 27-33mph I personally think a 48v 20AH would do you fine.

 

[tycreek]

* max speed: 28~32 mph (w/o pedal)
* range: about 25 m roundtrip (w/o pedal)
* type of ride: flat city commute
* carry trailer w/child (pedal assist)
....
Juiced Riders' (3/5C)

I have 2 48v 15ah packs and the newest one is the Juiced you reference (they both act/perform similar so far). With a 200w test load they both hit 650wh (90%) without tripping the BMS, where I figured that was enough of a test for me and pulled the plug.

On my 9mi round trip commute with 30mph peak running 20-25mph average, depending on the wind for the day, with either pack as a single they can hit the BMS cutoff point nearing home if I accelerate too hard. This behavior starts around 260-300wh or 40% of Ah rating. Typical day uses 37wh/mi +-1 where I try to keep take-offs near 2100w and back-off to a constant 1000w. Wh/mi drops considerably to 30wh or less when I lower the speed (800w) and acceleration under 1800w providing dramatically improved usable distance with a single pack.

With the double 15Ah (2x720wh) packs, the usable WH % increases. I say this because I observe good (my normal) acceleration without BMS cut-out into 900wh range or 60+% of the Ah ratings (have only gone that far, near your 25mi mark, a couple times). I assume this might have something to do with not consuming near the 3C max for an individual pack.

These are general observations and NOT perfect data logged tests, but might give you an idea for your battery requirements. Your combination could easily be more efficient, I don't know... but I do know I don't have enough Ah or WH to do what you are trying to achieve over a long period of time even though on paper I could be near doing it now.

There's some good technical battery data to be found here and elsewhere... take some of it and mix with your conditions ... then target about double that if it is for daily use JMHO.

BTW... Juiced Riders proved to me that they were good folk. I would have no hesitation buying from them again.

 

[icecube57]

Good thing he mention about the hard take offs. Some packs dont take that very well. And this will trip the bms very easily on some. Im still breaking in my Thundersky cells. They have/had a voltage sag to them aroun 3-4 C on the 20AH packs. But ive been cycling them and their performance has improved alot. They can hold higher voltages under a constant load and they will probably get better. I just drained my pack the other day. 3rd cycle and it was a performance ride. WOT and i was hovering aroun 57-58v. pulling 45A or so ast 35mph. It was able to hold this voltage for 80% of the ride. Before I i was getting a voltage sag/decline around 50%. Its one difference if you pack can peak at the C rating you want. But can it sustain it for long durations. Im not sure about the juiced pack. I have a friend that has one and his trips the bms plugging the pack in. I never had that issue with my 15AH ping. The ping pack I had was able do 3C without tripping the bms and helds a nice voltage.

 

[morph999]

Icecube, do you like the Thundersky's ? How do they compare to the Ping battery or is it still too early to tell? I love mine so far. I have about 25 cycles on mine.

Anyone interested in Thundersky performance. Here is a comparison with the Sky Energy batteries. I actually don't think I knew that the SE were better than the TS when i bought my batteries but I just wanted to get into lithium cheap so I'm still happy with my batteries. I only get a voltage sag from 42v to about 38v with a 35 amp controller so I'm happy with them. Elitepowersolutions says they are rated for 2C and these charts show that.

http://evworks.com.au/tech/ThunderSkyVsSkyEnergy/

 

[icecube57]

Compared to Konions they suck.LOL Compared to Ping. The rock interms of less complexity. My cells have only had 3 full cycles and 130 miles on them. I can sense they are getting stronger and more stable each charge. Im stikll gaining capacity. I put in an extra .5 on one of the pervious charge and .2 extra on the last. Balancing sometimes takes a while other times its quite easy. They happily do 2-3c with decent sag. The ping holds a slightly higher cll voltage under load compared to thundersky but considering how many cells ping has in parallel you can really compare. The IR is slightly higher on the ThunderSkys. Its to early to tell. Im just happy to have decent speed and sustained range. 50+ miles at 20mph and 30 at top speed of 30-35mph.