what is the difference between your min and max cell voltage.
If you are getting that 'recommend charging to full' that generally means it senses an unbalance in your pack.
When it thinks the pack is unbalanced your charge rate can go down.
Basically what happens is.
you charge the bike, the voltages go up, when one cell hits the max, but the overall spread is above, I want to say 50 mv, id have to check again, it goes into balance mode.
balance mode could be either a reduced charge current, so that the charge current itself does not excessively bias the actual cell voltages, or it is discharging the highest cells down a bit, then recharging the entire pack again until the next cell reaches the high point, then discharging the next cell/cells a bit, then recharging full pack again until hits high, next high cells... etc etc until ALL the cells are within the acceptable limit of spread.
Now, if the balance gets way of whack it might take a few days to get it back. Problem is, if the bike goes, I want to say an hour or so without power going IN, then it terminates the charge sequence. Even if it is not at 100 percent, it terminates the charge sequence. What YOU have to do then is remove power, and plug back in, that resets it and it starts charging again. and it will repeat that cycle again... and again, and again... until you finally hit a 100 percent charge, which is... when ALL the batteries are within the 50 mv span or whatever it is.
Where the problems start to come in is, when you get 1 or 2 batteries that way of whack for some reason. Lets say one cell is half a volt low... in order to get it to where it belongs, the way it currently works, it has to discharge ALL the rest of the high cells, recharge All the cells, discharge all the high ones, recharge ALL of them until it basically walks the voltage of that one cell up to the rest of them.
Lets for sake of a discussion say you have 80 cells in there,
lets say for sake of a discussion that the 'discharge' function, it can only dissipate a max of .. lets say 100 watts.
now, when you first initiate a charge. you may only have one or two batteries that are higher than the rest, so dissipating 100 watts out of one battery, man you can drop that voltage pretty fast. so you lower it 50mV then charge the entire pack up again, until next battery hits high cut off. Lets say now you have 5 batteries that are high.... discharging 5 batteries, ok, it's only 5 so you can still drop that 100 watts across 5 batteries and get the voltage down 50mv on them, before your hour is up. so you discharge them, they drop 50 mv and then it recharges the entire pack..... repeat ehh 3 or 4 times.
now you have 75 cells that are high and 5 that are LOW now. NOW you have to discharge all those 75 cells , thru that 100 watt load.... the voltage drop across all of them is going to be very low, since it's now 75 cells feeding it instead of a few. you are NOT going to get the 50mv drop across them in an hour. you have to dissipate 1 kilowatt of power..... thru a 100 watt load... in only an hour....... again,just throwing numbers out for sake of discussion.... the math don't add up, you can't discharge them that fast..so the hour times out, and the bike says, charge complete.
and it stays there until a new charge cycle is initiated.
so you start a new charge.... but instead of being half a volt low..... since you were able to take 'some' power off the high cells, it's only .45 volts low now...... so they all charge up.... then the top 70 dissipate... it times out..... you restart, it charges.. you are onw only .42 volts low on the low cells......... so you repeat again and again and finally walk the thing up to where it times out.... you charge it, it charges the entire pack, and viola, you are only .050 volts low on the lowest cell. ahh.... 50 millivolts... my cutoff point... now it will say, all batteries are in specs boot it the final time and then give you your charge complete, at which point the error messages should cease because YOU have FINALLY reached a 100 percent charged state.
The best way to 'fix this' is to buy one of those timers that you can set for say an hour on, 5 minutes off, so it just keeps resetting it over and over and over again... so YOU don't have to, so you can go off and do other things...like sleep.....
FWIW this is NOT just an Energica specific problem either, most the bikes operate this way, and if you get a shitty cell, this is about the only way you can fix it without opening the entire pack up and magtabbing the low one.
NOW.....
does having a low cell or 3 mean your battery is bad... NO !!!!!
They can drift over time,especially under high demand situations. ie racing rapid charging. back to back to back charge recharge without settling out and doing a good balance on them. If left unbalanced and cycled over and over and over. the unbalance will work itself to a greater value, until its to the point it's throwing hard errors at you.
another thing that can really monkeyfuck a packs balance is fast charging or even regular charging with a battery pack that is thermally unbalanced.... ie it was a hot day, now it's 28 degrees out..... the cells in the inner core of the battery are at 70 degrees. the cells against the battery pack wall are at 30 degrees... just because of the temperature difference, the voltages can vary .3volts or so. but they ALL are at the same percent of charge state. Bike don't know this, so thinks it's unbalanced and tries to force charge a battery that is not really unbalanced... now once the temperature settles out across the pack, the whole pack is wonky because you forced more power into an already charged cell and let power out of ones that didn't need it. This happens to cars fairly frequently too, but since weight is NOT AS much a problem on them, most of them have better BMS, to deal with this than a bike does.
If you are getting that 'recommend proceeding to a full charge' message, you will HAVE to actually GET the bike to a 100 percent charge and it terminates the charge itself, to make that go away.
A small unbalance is not horrible, but can grow and become a problem.
Aaron
Author
Topic: SOLVED: Can't charge at full speed (Read 12761 times)