How many watt hours did I use ?

[ScooterMan101]

Went on a ride today, I have a 36/48 volt motor that I am running on 48 v
The Display is the S-LCD3 Display sold by BMS Battery.

It does not show the amps used during the ride .
nor
Does it show the amount of watt hours used for the ride.

Starting Voltage was 53.8 volts , and finish Voltage was 47.1 volts.
The battery is supposed to be an 11 amp hour battery , but not sure of what is inside of the Cheep Case/Blue Shrink Wrap.

In the Description it says that charge voltage to 58.8 volts, but it never did charge up over 54.2/54.4 volts when new, and now it is only charging up to 53.8 volts

the Description also says Discharge cut off voltage, is 38.8 but it has not gone under 43 volts, unless during a quick takeoff , or up steep hill.
This is the battery 2 years old about 90 charge / discharge cycles mostly around 70% or less discharge.

http://www.electricmotorsport.com/e-bikes/bike-battery-pack-48v-11ah-linicomn-with-charger.html

 

[Sunder]

Here's some ball park maths

58.8v / 4.2 = 14S

53.8 / 14 = 3.84v.

Unfortunately without knowing which chemistry is in there, 3.84 could be as low as 50%, or has high as 70%. Given that they set their BMS to cut at 2.7v, I'd guess 70%

47.1v /14 = 3.36v

Again, we have the issue of chemistry, but I don't know of any chemistry that has more than about 10% left at 3.3v. Most have almost zero.

So if I were to bet money on it, I'd guess you used between 60 and 70% of the rated capacity. Let's call it 360ish watthours +/- 25%. You can tell that this is an extremely imprecise science. Just buy yourself a cheap Watt meter instead of playing guessing games.

From the sounds of it, (refusing to charge higher), that at least one cell is way out of balance, causing the others to overvolt and trip the BMS to stop charging. Put it somewhere safe - as in fire proof, and leave it on the charger for a week and see if the peak voltage rises. If it does, keep it on there until it no longer does. It's a VERY slow process, because if only one cell is faulty, it needs to bleed off milliamps from 13 other cells over time before allowing the whole pack to charge again. Of course, if the one faulty cell is self-discharging faster than the BMS can bleed off energy, well, it'll only get worse over time - even on the charger.

 

[ScooterMan101]

Sunder ,

I am understanding some but not all of the math,

I can see by your calculations and the description of that higher 58.xx volts , that I have a battery that they previously sold,
My battery case was black, and even when new it stopped charging at 54.2 volts,
So
I do not have a 14s , I have a 13s pack.

Now them being 18650'''s I have no way of knowing which cell is low/not charging since there is no balance wires/plugs , coming out of the pack like Hobby Lipo's , to plug into the charger. In this case a bulk charger .
The Balance Charger always stopped at 54.x volts, and says 54.6 on the sticker. I even tested it a year ago and found close to that on the Multimeter.

I have been wanting to get a few wire harness and a couple of other items from H.K. so I will look for that cheap watt meter you speak of, but will have to wait until the wire harnesses and connectors that I want are back in stock.

Where do you hook up that cheep watt meter ?

Edit : looks like the little meters from H.K. show you real time watts/amps/volts
and one also records peak and low,
But
Not cumulative watt hours used.

Do you have one that does record and store cumulative watt hours used ? of know of one ?
Any of the displays other than the Cycle Analyst that can be hooked up to a standard/generic controller , and that records and stores cumulative watt hours used ?

 

[amberwolf]

Lots of them do; ones I've used are Watts Up, Turnigy Watt Meter. (a google search will turn up places to buy them).

None of them I've seen except the Cycle Analyst will save the info once power is disconnected (like if your battery cuts out due to BMS shutoff), unless you hook up a separate battery to them via their Aux connector.

You plug them in between the battery and the controller.


Various discussions, not all of which are relevant:
https://endless-sphere.com/forums/search.php?keywords=watt+meter&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=wattmeter&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

 

[dogman dan]

Hard tell what exactly is going on with your battery. The charge voltage spec looks like 14s, but the LVC matches 13s better.

In any case,, when one group of cells reaches a low voltage, the whole pack shuts down, the bms stops it.

My guess is you have a 13s battery. Check the voltage of your charger. If it is 54.6v or near that, you have a 13s charger. I'm betting you have 13s battery, and a set of specs in the ad full of mistakes. Very few batteries that look like yours will be 14s.. the industry standard for bike 48v batteries is now 13s.

Having the battery stop around 40v would be normal for a 13s.

Try to balance it better, by charging it, waiting half an hour after its full, still plugged in, then ride around the block and repeat the charge and wait process. This will help your charger restart charging, after its BMS has discharged any over full cells. This will help the lower cells catch up. Repeat this about 6 times at least.

See if you can get it to settle in, so an hour after the charge finishes,, the volts are very close to 54.6v. Or whatever the charger is set for,, if it puts out 54.2v for example. If it settles in full, it's also full and balanced. Then you can use the watt meter to find out what your real world capacity is. 9 ah,, 10 ah,, likely will not quite be 11 ah in real world use.

 

[ScooterMan101]

I do in fact have a 13s battery , I bought it 2. 6 years ago.
The Charger that came with it with has a sticker on it that says 54,6 v 2 amps.
However , since there has been so much talk about not charging a battery up to 100%
I have been pulling the charge plug out when it reaches between 53-54 volts.

This is the first time I am hearing about leaving the charger on, and plugged into the battery for a half hour after the charger shuts off .

Do the Cheep Chinese Bulk Chargers trickle charge when it senses full and is still plugged in ?

I just finished topping it off, it is not yet a half hour, so I will get back to edit this once a half hour is up and I have checked the voltage, would it read high, or because it was on trickle for a half hour would it read a more accurate settled down voltage ?

Today I will do the 6 top up charges with charger still on for a half hour each time, and operate it for a few minutes, between each top up charge, since it is raining I will put it on the repair stand and let it run for 5 minutes or so.

Then its on to doing some charges and discharges on the Hobby Lipo's I bought several months ago , that is another thread so I will post results of first charge and differences in each cell , and ask questions there since I now will be operating/charging/discharging two different cell chemistry's

Check the voltage of your charger. If it is 54.6v or near that, you have a 13s charger. I'm betting you have 13s battery, and a set of specs in the ad full of mistakes.

Try to balance it better, by charging it, waiting half an hour after its full, still plugged in, then ride around the block and repeat the charge and wait process. This will help your charger restart charging, after its BMS has discharged any over full cells. This will help the lower cells catch up. Repeat this about 6 times at least.

See if you can get it to settle in, so an hour after the charge finishes,, the volts are very close to 54.6v. Or whatever the charger is set for,, if it puts out 54.2v for example. If it settles in full, it's also full and balanced. Then you can use the watt meter to find out what your real world capacity is. 9 ah,, 10 ah,, likely will not quite be 11 ah in real world use.

 

[999zip999]

You might get 11ah or 10ah if discharged at 2amp. But at your bike ampage less.

 

[999zip999]

Those numbers are all over the place. Charge 58.6v discharge 38.8v and 2,000 cycles ? Good luck.

 

[dogman dan]

Undercharging like you have been, you likely have the battery out of balance now. So charging it full each cycle may be better. At least, charge it full periodically,, weekly, monthly, whatever depending how much you use it.

Undercharging is fine, but you still need to balance sometime, you could do that manually at 4v, but for a perfect balance, you much charge full. The damage from charging full is minimal. The damage occurs when you let it sit in storage full, in a hot environment. Winter storage full, usually a cold environment, so not near as bad.

Some chargers will shut off, then turn back on in 30 min or so, to keep recharging after the bms had drained a high cell or two. Others just shut off. Leave it plugged in just in case you have one that will turn back on. Then do the short ride, and put it back on. If you witness it turn back on,, then you can skip that part about ride it to make it turn back on.