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Latest info on my ebike....

Old 05-08-11, 04:53 PM
  #1  
sunnyday
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Latest info on my ebike....

top speed is 32 mph on FLAT paved road....which is quite fast considering I weigh 270 lbs and my bike weighs 70 lbs...

my 48 volt /20 Ah lifepo4 only has 3 complete cycles on it...so its still breaking in...

on a full charge, I got 22 miles on it, before the BMS cutout at 42 volts reading...11 miles was pedal assited by me, on hills, and the other 11 miles was basically all electric power without pedal assist. I imagine if I do pedal assist on all inclines/hills , I would be able to get 30 miles distance out a fully charged battery.

after about 30 miles, my butt starts to hurt anyways..so even if it could go 50 miles distance or more, I doubt i WOULD RIDE IT THAT FAR in one session.

all in all, im very happy with the ebike now. I figure it costs a few pennies to charge the battery ...With my solid airless tires, I think I have a setup that will be virtually maintenance free for many years.
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Old 05-08-11, 04:55 PM
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I think the overall best speed is around 16-18 mph...this is probably the sweet spot in regards to getting the most efficiency out of the battery / motor and insiginficant wind drag....once you get over 18-20 mph on these bikes, you are now wasting ALOT more battery energy/efficiency to combat the headwinds...
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Old 05-08-11, 10:19 PM
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Sangesf
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My battery from that seller fully charges to 45.9v and when I pull the charger off, drops to 44.4v and stays there until I put a load on the battery.
That's 3.7v per cell, exactly what I believe is perfect charge.
The charger does (did) cycle on and off intermitantly at the end of charge to balance the cells..
I'm guessing the BMS is doing it's job..
(the seller originally told me the bms is set for 3.9v per, but I know for a fact each cell group doesn't get a I've 3.7)

I am not sure if the battery truly is 20ah, but I will test it out tomorrow because I have a long trip to go on.. If it really is 20H, I should be able to get 26-28 miles out of it. (All flat, level roads here in Florida).
Will let you know tomorrow night.

Sunnday,
Hows the battery voltage after charging and then pulled off?
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Old 05-09-11, 07:26 AM
  #4  
sunnyday
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Originally Posted by Sangesf View Post
My battery from that seller fully charges to 45.9v and when I pull the charger off, drops to 44.4v and stays there until I put a load on the battery.
That's 3.7v per cell, exactly what I believe is perfect charge.
The charger does (did) cycle on and off intermitantly at the end of charge to balance the cells..
I'm guessing the BMS is doing it's job..
(the seller originally told me the bms is set for 3.9v per, but I know for a fact each cell group doesn't get a I've 3.7)

I am not sure if the battery truly is 20ah, but I will test it out tomorrow because I have a long trip to go on.. If it really is 20H, I should be able to get 26-28 miles out of it. (All flat, level roads here in Florida).
Will let you know tomorrow night.

Sunnday,
Hows the battery voltage after charging and then pulled off?


I have cycled the battery about 3-4 times now...and it is charging to 58.4 volts at full charge, but then drops down to 53.8 volts when I take it off charger...so im only getting 3.36 volts per cell....much worse then your 3.7 volts per cell.
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Old 05-09-11, 09:40 AM
  #5  
Sangesf
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Have you let it sit on the charger for an entire 24 hours yet?
It shouldn't drop back to that low immediately..
I was told the BMS for mine is supposedly set for 3.9 per cell, but I know it don't go that high...
Charger only gets to 45.6 which is 3.8 per, however, the BMS is definitely cutting off before that.
At 45.0v the charger turns green, and then does the on/off thing every minute or so (the BMS is balancing the cells).
It's possible your BMS IS set to 3.9 per cell group (or 62.4v) and if that's the case, then your charger is not going to be powerful enough to start the full BMS balancing..
I would say to do this....
Charge to full, then pull the charger off, disconnect the battery from the controller, pull the balance leads from the BMS and check every cell group with a multimeter and record the results..
(To test the cell groups, you start at the positive side of the charge plug on the battery with the positive lead from the multimeter and the negative lead from the meter to the first pin on the balance leads(if it shows high voltage you started on the wrong end of the balance leads, just start with the other end of the balance leads with the negative of your meter), then carefully go down the line of the balance leads and check each group, one by one. And at the last balance lead use the positive end of your meter to last pin on BMS and negative side of meter to the negative side of the charge port on the battery).
Report back what each group shows..
I have a feeling , you'll have some cells that are 3.9v each and some that are 3.2v-3.3v each. (Not balanced)

22 miles from a 48v 20ah is way to low..
I get 21 miles from a 36v 15ah battery. (And my bike is probably TWICE as heavy as yours, if not more.)
Comparing the WHs of each, you supposedly have 960wh and I have 540wh, which is almost half of yours..
That works out to 43.6wh/mile for yours while mine is 25.7wh/mile.
Something is just not right.

Last edited by Sangesf; 05-09-11 at 09:44 AM.
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Old 05-09-11, 12:39 PM
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sunnyday
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I already did check each cell...about a month ago....fully charged , off the charger about 30 minutes..each cell was 3.35 volts = 53.6 volts....

so each cell was balanced...but each cell was no where near 3.7 volts each...

now maybe its possible that after 20-30 full cycles, the cells will start to hold a higher charge , but so far each cell is at 3.35 V...

My aftermarket charger, is now taking the whole 48 volt battery up to a 58.4 volt charge...and then my charger shuts down...The fact that each cell is equally charged at 3.35 volts , 20 minutes after I take it off the charger , seems to indicate the cells are not out of balance and if my charger is taking the whole battery up to 58.4 volts, and then cutting off, then that should indicate the charger is working properly.

I could leave the battery on the charger for 24 hours, but I dont think thats gonna change anyhting, since each cell is equally balanced and the charger is taking the whole pack to 58.4 volts , then automatically shutting down.
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Old 05-09-11, 12:45 PM
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I got about 22 miles out of the last charge , before the BMS cutout at around 42 volts { under a load** . 11 miles of that was with some pedal assist on hills, and the other 11 miles was all battery powered , and no pedal assist on hills...

I think my biking route is much more hilly then yours.....and I noticed that any siginificant hill REALLY strains the battery..in other words...

a 2 mile route that has a 12-14 % grade on much of its terrain is gonna pull as much of a drain on the battery as a 6 mile route that is relatively flat terrain.
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Old 05-09-11, 02:16 PM
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Sangesf
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Something is amiss... They should not be dropping from 3.65v per to 3.35v immediately..
It seems as if the BMS is not allowing full current of 3-5 amps to the cell groups after they hit above 3.4v It seems more like they are hitting 3.4 and then the current drops to much less (prolly in the 350mA range {.35a**)

If you haven't got one yet, I would purchase a real time watt analyzer, such as the Turnigy or Watts Up, watt meter and log all the statistics of charge and discharge.. It will give you a good idea of the power your using and the charge statistics as well.
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Old 05-09-11, 02:41 PM
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sunnyday
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Originally Posted by Sangesf View Post
Something is amiss... They should not be dropping from 3.65v per to 3.35v immediately..
It seems as if the BMS is not allowing full current of 3-5 amps to the cell groups after they hit above 3.4v It seems more like they are hitting 3.4 and then the current drops to much less (prolly in the 350mA range {.35a**)

If you haven't got one yet, I would purchase a real time watt analyzer, such as the Turnigy or Watts Up, watt meter and log all the statistics of charge and discharge.. It will give you a good idea of the power your using and the charge statistics as well.
You and I discussed this in detail months ago...I thought you said that it is normal for the cells to drop to 3.35 volts once the battery is taken off the charger ?

You claimed that the 3.6-3.7 volts per cell , was not the working volts..and that voltage would immeidately drop to the 3.2-3.4 volt range under a load anyways..

my charger is taking the whole battery up to 58.4 volts...so the BMS seems to be allowing a full charge and the charger seems to be giving a full charge...
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Old 05-09-11, 05:19 PM
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it might be normal for your cells to drop to 3.35v. It might depend on just what kind of brand of lifepo4 they are. My Thundersky drop to about 3.50 v after going up to 3.70v. After sitting for a long time, they might drop to about 3.45v.
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Old 05-09-11, 06:30 PM
  #11  
sunnyday
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Originally Posted by morph999 View Post
it might be normal for your cells to drop to 3.35v. It might depend on just what kind of brand of lifepo4 they are. My Thundersky drop to about 3.50 v after going up to 3.70v. After sitting for a long time, they might drop to about 3.45v.
well I just did another charge...let the charger take it to 58.4 volts...let it sit for 2 hours, and the battery is now reading 55.2 volts....instead of 53.6-53.8 volts that it did before...

it may take a few more comp0lete cycles to get the battery up to proper voltages.
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Old 05-09-11, 07:05 PM
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Sangesf
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Put the charger back on and leave it over night and then check voltages of cells again..
You are correct in what I said earlier, but that was before you put it through some cycles..
It seems to me, you're apprehensive to leave the charger on the battery..
Trust me, it won't hurt it at all..
Leave it on for at least 6-8 hours, if not more, and I bet the cells will get up to and stay at 3.6 or higher.
Best bet is too leave it on for 12 hours or more.

Have you (recently) left the charger on for more than 2 hours after it turns green?
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Old 05-09-11, 07:40 PM
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Morph,

Sunnyday bought the SAME (type) battery as I did, from the same seller on eBay. (His is 48v 20ah, mine are 36v 20ah.)

I put mine through many cycles in just 4 days (over 20) and left the charger on for 12 hours each day.
The 36v charger charges at 45.9v 3a until 43.8v is reached (3.65v avg per cell group) and then the BMS kicks in and it limits the amp output/input to about .35a until the BMS starts balancing of the cells (that's the part where the power supply goes green and jumps to 45.0 volts (45v .18a) and then you see the charger go from green to red and back to green until All cell groups reach 3.75 and then no more green to red to green and voila! Fully charged and balanced!
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Old 05-09-11, 07:43 PM
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sunnyday
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Thumbs down

Originally Posted by Sangesf View Post
Put the charger back on and leave it over night and then check voltages of cells again..
You are correct in what I said earlier, but that was before you put it through some cycles..
It seems to me, you're apprehensive to leave the charger on the battery..
Trust me, it won't hurt it at all..
Leave it on for at least 6-8 hours, if not more, and I bet the cells will get up to and stay at 3.6 or higher.
Best bet is too leave it on for 12 hours or more.

Have you (recently) left the charger on for more than 2 hours after it turns green?
tell me your opinion on how much distance I should get out of my fully charged 48 volt lifepo4 battery ?

total weight of me and bike is about 340 lbs....

If I pedal assist on hilly roads, do you think I should get at least 40 miles distnace before BMS cuts out at 42 volts ?

are you happy with the lifepo4 you just got off ebay ?
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Old 05-09-11, 08:06 PM
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You should get about 38.5 miles before cutoff, once all your cells are fully balanced.
I have a feeling ONE of your cells groups is not getting fully charged yet. (I think that's your "weak link".)
Once you get that group up to speed, you won't have a limited distance anymore..

FYI.. I just today tested my battery.
Results are as follows...
On my normal 36v 15ah battery, I average between 21 and 22 miles at a 15-20a (1c-1.3c) draw.
Or approximately 25-26wh/mile.
On this new 36v 20ah battery, and a max pull of 20a (1c), I got 29.5 miles or approximately 24.4wh/mile. Which got me thinking... I almost never achieve less than 25wh/mile (Especially since today, there was alot of headwind)
Then I remembered... This is really a 21ah battery, so I ran the numbers again..
Instead of 20ahx36v=720wh, I have 21ah times 36v which is 756wh and then divided by 29.5 miles is 25.6wh/mile.

So, ultimately this battery is working perfectly and up to spec!

Yey!

Last edited by Sangesf; 05-09-11 at 08:13 PM.
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Old 05-09-11, 08:35 PM
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My wh/mile varies between 15-25 When I have a headwind I pour the power on. If someone asks what the range of ebikes are I tell them 35wh/mile. Better that they get a bigger battery than one too small.
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Old 05-09-11, 09:36 PM
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My testing involves "worse case" scenarios for flat terrain riding.
Full throttle
Headwinds
170lb bike
170lb me
Etc..
I almost never go above 30wh/mile...
I guess with moderate hills 35wh/mile is a good point of reference.
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Old 05-16-11, 09:29 AM
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sunnyday
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well it looks like after 10 cycles on my battery..it is now holding a charge at about 56 volts...compared to 53.6 volts when i first got it...evidently even these batterys have a break in period....like most other batterys.
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