Sorry Bruno
But the calculations don't work the same way.
This means that for a 12Ah battery you have:
* maximum continuos discharge 30A
* maximum pulse discharge 120A
And for a 16Ah
* maximum continuos discharge 40A
* maximum pulse discharge 160A
The charge rate it is important to keep low so the life cicle is extended, I know that the regenerative is limited to 5A, but not sure about this number.
My watt meter shows me that with my pie the maximum current is 30A with is ok! Nice to know!
But without use my battery discharge much more than 0.5%, not sure how much, but is more. This could be because of the BMS system?
For; Max Continuous current, Max Continuous discharge current and Max Charge current, the calculations are totally different.
Using their spec's, I have an average of what they have after the BMS "which is off the wall" . But, after comparing with all their "sayings", is's 'ahhh' close.
Remember their are somethings you can not compound because of "series or parallel" configurations.
For instance; #C X mah / 1000 = Total Max current Discharge current (Amps). (This is before it has gone through the BMS).
Just remember, the BMS restricts the current in more ways than most can think of.
I think it was you who said: "you were getting 30A max off of your system on a 12 Ah battery". Well, with the proper calculations for their cells, the actual Max Continuous is only +/-40A for a 16Ah and =/-30A For a 12AhA, MOST LIKEY A LOT MORE - (This is using actual calculations, not GM's). If this the fact, you are getting exactly what you are suppose to be getting.
If you are getting 30A on your bike, then you are with in the "Max Area" of the pulse with-drawl of the battery. Due to the settings of the BMS you are just hitting outside the Max Continuous Discharge and are using more power than you should be really using and more power than you may really want to be using in total wattage/amps to conserve power for distance.
Now, they advertise their ratings at and come out to be 1.625C for Max Continuous charging = 6.5 Amps charge current, 2.5C Max Continuous discharge and 10C Max pulse discharge. But after searching all the spec's on their cells, the actual is: 1 - 1.5C for Max Charge Current = 4 -5 Amps Max charge Current, 2C for Max Continuous Discharge and 5C for Max Continuous Pulse Discharge.
This being, it would make your diagnosis above, one half (1/2) " give or take a few", lower than "MAX DISCHARGE CURRENT".
"Just because you have a long series of batteries at a certain current for recharge, don't mean you want to charge it fast with a lot of current just because you want to. To do so, will lower the longevity of the battery. ( This was just because of a lot of posts all over the place for those who want to charge fast.) The slower the charge, the longer the charge will last and mainly the longer the battery will last'.
Totally too tired tonight to give you the spec's. (Helped a friend move Thurs. and Fri. + my couple of side jobs today).
I will in the morning.
Don
One should should stick close to energy density and watts IMO.
Any given pack can only take so many watts and high temperature of pack damages the cells.
Lithium energy density approximates to 460wh per KG including and internal resistance you might land 440 watts out.
440 watts / 3.2v = 136 amps = per KG and 13 amps per 100 grams.
A 4 ah cells weighs approx 100 g and a 12 ah cell should output 4x13= 52 amps. This equates to less than 13 mins of run time, and as the cell discharges the internal resistance increases creating a higher voltage drop thus causing the cell to LVC and have unnecessary damage..
Voltage is not definable by any thing than the resistance that it travels along Really the smallest volt = infinite @ zero resistance and this explains why ion propulsion can propel objects at light speed in the presence of very little resistance or a vacuum.
Charging is the not the same thing..
You can charge a cell at 3.2v a 1 amp. 32v @ 100ma 320v @ 10ma and so on.
As long as you do not exceed the rated end voltage and charge wattage the cell will enjoy a long cycle life. This is how cells charging ability should be measured in watts not anything else IMO.
Cells degrade from heat.
There is no science around centigrade or Fahrenheit other one was the boiling point of water and another the flash point of paper. Its about time we made our own constant here. Every material inside the battery in the line of charge has resistance or lack of it creating a solid circuit. You could even look at each cell like a light bulb with 40 milliohm resistance producing heat.
4ah 100 gram cell
Cell discharged =2.4v,
Cell rests at 3.2v,
Floats at 3.4v
Cell resting = 0 watts = no heat
Floats at 3.4v @ 160ma
A typical cell cycle discharged @ 70% = 2.4v and charging on bulk 3.6v @ 1.6 amp charge = 1.2v over potential @ 1.6A = 1.92 watts between the 100gram plates.
But
About .4 ohm resistance per cell @ 3.6v will allow 9 amps into the 100 gram cell and with the 1.2v over potential = 10.8 watts.
If the cell heats to 35c with 2 watts how much will it heat at 11 watts. Linear model suggests 7 times the heat at 9 amps bringing cell temp over 70 degrees C this is way already too hot.
Cells are insulated and like military spec dictates more than double you ratings. With the heat no where to go heat pools up so 70c heads way over 140 degrees. OOOZE of stank and smokin. This is why charging is slower.
More about dischargeOn the above math a 4 ah at 70% cell can produce 8.96 watts per hour per cell. A charged 12ah cell will produce 25 watts per cell. 15 12ah cells to 70% dod will produce 403 watts.
At 100% discharge (dead cell) it equates to 12.8 watts per 4 ah cell X 3 parallel = 38.4 watts X 15 series cells (48v pack) = 576 watts
To test if I got it right. 48X12ah = 576 watts.
I nailed this one.
However getting accurate charging specs needs to be worked on the materials used in the battery and is way more complicated than I want to work out the physics to ATM.
The battery life.As the battery gets older so to the charge rating should change. Even on a hot or cold day you can milk the most out your pack if you know everything there is about what is going on.
In the hot summer you could limit the voltage per cell by .07v and by .1. Around 3.5v on a really hot day. In the cold you could push the cell to 3.7v.
You could go a 3.4v float charge at 10 amps and watch the current drop to 1 amp when its charged.
I used a 72v homemade voltage doubler on my 48v pack. I limited the volts to float at 54v with a regulator, and it pulled 3 amps from 72v supply @ 2.5 amps. My battery was full charged in almost the same time. Placing the charger I bought over the pack proved it was full as the light went green immediately.
High current at constant float voltages. This is the safest way to charge as you can not ever exceed the cell voltage. Even if you give the the pack 20 amps will not draw any more current than it needs to stay at float but when the battery is flat it will draw as much as you want to give it.
Constant current at bulk voltages is safe as long as the charger is a good one.
I think lithium charges fast with constant current charging and better with constant voltage. Many charger designers use both to maintain cycle life while fast charging.
Be careful charging too slow at bulk voltage mode at low amps as the battery can hang at 3.6v for too long and get warm and if electrolyte vents anything you lose life fast..
