Amp draw questions on Ping 72v battery

[chris22104]

Ok, I have my bike all set up and running with a Ping 72v 15ah lifepo4 pack and bms, Lien 72v 4110 controller, and an ampeds bikes 26" dd rear motor. I just installed my ca-dps and halogen headlight, and took it for a ride tonight. No limits have been set on the speed controller or my ca yet. At full throttle and when at full speed (41.6 mph max speed,) I'm still drawing the full 50 amps, with a peak spike (on this 3 mile run) of 96 amps! I used 3.47 ah. I was hoping when up to full speed, the amp draw would be lower, but not so. From everything I've read on this forum, Ping's batteries should not exceed 22.5 amp draw. When I let off the throttle enough to bring the draw down to 23 amps or so, I'm not even close to the speed I need to be at, for my long commute. My ride is very rural, straight flat roads with no intersections, turns, lights, or stop signs. Open flat land everywhere. Even 30-35 mph is too slow for me. So my questions are: If I keep everything where it's at and continue my full throttle long runs at 50 amp draw, how much less life (cycles) can I expect from my battery? And If I wanted to maintain this 40+ mph speed for the full battery cycle (basically, full throttle long runs,) obviously lifepo4 is not the answer, right? What kind of batteries would hold up well to a steady 50 amp draw? What kind of bms? I know the motor and Lion speed controller can take it, but I guessing my ping battery will be the weak point, right?. Advice?
Thanks!
Chris
PS: Since I installed the ca tonight, now my cruise control wont engage! Nothing else has been changed, and it worked fine prior to the ca. Thoughts?

 

[RVD]

2c is about safe for ping lifepo 4 which is 30 amps. for 50 amps you need lipo or a123...

 

[dogman dan]

Well you are stuck with that ping now unless you sell it immediately for a large finacial loss. A few more cycles like that and it's value is zero.

I'd say take the risk, and set the CA to max at 30 amps. Rather than kill it fast at 50 amps, it would be better to just send it free to someone here on the forum that is poor and could use it fo a long time. Really, no particular point in trying to run it at too high c rate. With almost 100 cells in there, at least one won't hack the 3c discharge rate and start failing. It could happen that all the cells turn out to be strong enough, but the odds are a few won't. But we do have examples we have heard of here of people pulling 2 c for more than a month or two. So I'd say your odds of getting through as much as a year at 30 amps are reasonably good. Give it a try, after all you are stuck with that battery now in any case.

30 amps continuous should be able to get you wound up to a decent speed, I have been able to maintian 30-35 mph with 72v using a 20 amp lyens controller.

Since you say you want the full 50 amp ride, you will have to invest in something able to provide it eventually. Headways or A123 for lifepo4, or lipo. Lipo usually is run without much bms, just low voltage warnings of various kinds.

How far is your commute? with the really high discharge stuff like lipo, perhaps you could even make your battery 10 ah?

 

[dnmun]

buy another 15Ah from ping and put in the other side.

 

[Doctorbass]

I installed 45A C-lyte controllers on 15Ah 48V ping battery v2.5 and they work really well.
7 total electric bike with that setup..

Peak amp on the C-lyte 60A.. burst power during hill climb 2500W

I can say that the Ping 15Ah 48V battery CAN take 2500W burst no prob

Never noticed any lost in capacity since two years

Doc

 

[dogman dan]

I'm still amazed at those that have done what you have Doc and get away with it, but some have had less fun outcomes. Giving folks advice before they buy, I'm still pretty conservative.

I have no doubt that a 48v 15 ah ping with all 48 cells in perfect shape can do a lot. But one weakling cell in there would increase the c rate on the cells in the paralell string by quite a bit. The problem is the real world odds of having a runt in the pack, that packs it in when used above 2c.

Since he owns it now already, there is nothing to lose now by trying it. He's talking long continuous high c rate, so I still don't think much more than 30 amps would be advisable. I could definitely see it lasting long enough at 30 amps.

The quick and dirty solution for him may be to paralell some more better c rate lifepo4 with the ping. But he's packing quite a few pounds of battery already.

My own personal experience with really abusing a ping was in the death race two years ago. My 48v 15 ah ping V2 had about 20 cycles on it. With a 30 amp controller, and hammering it with spikes 13 turns to the lap, it sagged like a bloodhounds ears by the end of the 12 lap race. I thought it was completely discharged, but it was only about 2/3 discharged. It had sagged like it was 95% run down. For the next two weeks, it failed to take a full charge and capacity was down untill it fully balanced several cycles later. The battery is fine now, but that race full of amp spikes did at least take the battery way out of balance.

 

[chris22104]

My ping is a new v2.5. I've actually run it full throttle (drawing 50 amps) for 3 to 8 miles about 15 times now, without a problem. I didn't realize I was drawing that much current at full speed, until I received and installed my CA (before the last run.) The pack is made up of 24 cells at 3.4 volts each (I believe.) The bms works great and there is an led for each cell (illuminates when each cell is full.) I will set the limit at 30 amps on my CA and see what speeds it will take me to. The battery is in two parts now (about 12"x6"x3" each) and must weigh 40 lbs total. I can't and don't want to add to it. I'd rather switch out the battery to a better chemistry capable of a repeated high discharge rate, but I would like to have or make a bms for recharging/equalization purposes. Are A123 cells the same chemistry as lipo? If not, which would be better for this type of discharge? Best source for matched cells? Prices? What about sources for a bms or kit? Has anyone here made their own bms? Pics to come.....

 

[dogman dan]

A123 is lifepo4, but better quality with higher c rate than ping pouches. If you just can't stand the slow speed of 30 amps, then tweak it up to 35. If you want to stay with lifepo4, then A123's or headways is what you want. Since you have not had immediate problems, like noticable voltage sag or badly inbalanced battery taking forever to light all the leds, I think you have a pretty good set of cells. That's good, so you may be able to go higher amps than I recomend for longer than I expect. I would expect from what I have heard others doing, that 30 amps should last a year.

It's hard to say what will happen, only one cell in there unable to take the high c rate can bring the other two cells down with it. Then one cell group that is discharged early shuts off the bms. So for that reason I recomend 1c discharges as much as possible, for those who are more interested in maximizing the lifespan to avoid another battery expense.

 

[chris22104]

Thanks dogman,
I'll test the 30 amp and 35 amp settings, and report back my speeds (and pics.) Can lipo's handle a faster discharge better? And what about making or buying a bms for them?

 

[chris22104]

Maxxis hookworm 26 x 2.50 tires at max 65 psi. At 30 amps and at 35 amps, I got the same max speed; 32 mph. Go figure. It just takes a bit longer to get there, (and not as much oomph going up light inclines.) My average speed was lower, but that's because I came to a few stops at the same locations when testing, and it took longer to accelerate back to full speed at the lower 30 amps. So, for battery longevity purposes, I guess I'll keep it limited to 30 amps. I still want to find out more about lipo's, comparitively to a123's, and availability.
I don't know how to add multiple pix, so here's the direct links:
http://img.photobucket.com/albums/v457/julian108/ebike101.jpg
http://img.photobucket.com/albums/v457/julian108/ebike102.jpg
http://img.photobucket.com/albums/v457/julian108/ebike103.jpg
http://img.photobucket.com/albums/v457/julian108/ebike104.jpg
http://img.photobucket.com/albums/v457/julian108/ebike105.jpg
http://img.photobucket.com/albums/v457/julian108/ebike106.jpg
The bike is stable and smooth at full speed, and I never have to touch the brakes when slowing down (with the regen set at full,) until about 10 mph when the regen cuts out. The CA luminator headlight is phenomenal at night, and brighter than my car's brights! I highly recommend it, and you can have your CA wired for a direct plug in! And thanks to the guy who suggested the large display CA over the standard size (in an earlier post it sure make it easy to read while at speed! Now for a full throttle (at 30amps) straight line, non-stop, overall range test, till cut-out at 63v! Will report back with findings...

 

[chris22104]

OK, road tested at full throttle (CA set at 30 amps,) from full charge till dead. Results: 30.5 miles going into a 10-15 head wind the whole way. Speeds ranging from a low of 19mph going up a big steep hill, to 32 mph on a slight downgrade. A perfectly straight run, minus only 2 lefts and 2 rights. Avg speed around 26 mph. Had to stop 2 or 3 times (traffic lights.) I'd like to repeat the test the same way in warmer weather, on a calm day (no wind.) Gotta balance the rear tire/rim; way out. Reflector on rear rim spokes probably doesn't help, so that goes first. Otherwise, awesome! At dusk, with the CA luminator headlight, I was lighting up signs 500 feet away! Two oncoming cars actually flashed their brights at me!

 

[wesnewell]

I couldn't find a 72V battery on pings website. Are you talking about his 60V packs? What's the cell count? 20s? 20s lifepo4 is pretty weak compared to 20s lipo. 18s lipo charges to 75.6V, and 20s to 84V. For your questions about lipo and A123, you wouldn't have to worry about amp draw with either. The big difference will be price and size. Lipo is relatively inexpensive by comparison. Also lighter and smaller in size. For what you want. I'd go with 15ah 24s lipo charged to 100V. 100A draw from it would be nothing, and the extra voltage and wh would let you go as fast as you want. 27s A123 would work too. I'm assuming your controller can take 100V.