Could be heat. If you had about 4v drop at full power with a 52V battery, that's 200W of heat to dissipate, which is quite a lot, especially as the inner cells are surrounded by other hot cells, so no chance of losing their heat. If you ran at high power for a long time, like you do on a crank-drive bike, the battery would get hotter and hotter.
further investigation of battery cutting out before set LVC
- Thread starter minexplorer
- Start date
If any cell/ groups are bad they will/should charge to 4.2v and then after being left for a few hours or over night any capacity loss will show up as the voltage drops off.
will check that for sure
i was impressed with the 30Q s as battery would barely get warm after 2 mile hill climbs or long stretches of WOT. others were claiming GA batteries were getting hot under similar conditions.for a long time now tho ive been only using max for short blasts on hills. battery temp is Something else i can check to see if its changed,thanks
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thanks sturmey.im trickle charging the cells all to the voltage of the highest one 3.50v with a 450ma mobile phone charger.then ill give it a full charge and a good balance.they should all reach 4.2v hopefully then.
Hi. When a battery in normally been charged, it will be noted that there is a constant current stage (about 60% of charge) and then a constant voltage stage, which brings the battery up to full charge.
Now, from my observations, the problem with cell imbalance is that even if a cell is 0.1 volt higher, it can trigger a BMS shut off before the constant voltage stage and hence stop charging with less than 60% of the battery capacity.
This was very noticeable in my case, the 7ah battery that use to take over 3 hours to charge, time started to reduce until eventually it only took 2 hours before charger light turned to green.
By the way, if you are using the BMS sense wires to drain down any of the high cells, you need to limit the current to perhaps only an amp or two, as the wires are fairly light.
you are right, i did some math and worked out i was loosing the use of 5v of capacity due to a cpl of cell groups triggering the LVC early. the battery not balancing because of that 0.1+ volt difference of 7 of the14.
update.
after using a mobile phone charger to equalize all the cell groups i put it on a full charge. the charger finally went into balancing mode for the first time in the year ive had the 52v battery. didnt know battery has to be switched on to enter balancing mode and it was quite out of balance.
All the cell groups now read 4.1v total 57.6v. previously 7 at 4.2v 7 at 4.0v-4.1v total 58.2v. After over 24hrs off charge the voltage hasnt dropped all still 4.1v.
Although ive lost .6v capacity i guess this is due to some of the cells being unable to reach 4.2v anymore .So the BMS has dropped those that can to their level. Is this drop in capacity overall from 58.8v when new to 57.6v after 1700 miles 11mths use unusual? im thinking maybe the hard use..being a 30amp bbshd,along with always draining fully and not getting balanced has caused more than just age wear?
is it possible a few discharge charge/balance cycles will creep it up a little . will have to see if it will now go to the LVC of 42v. before one of the unbalanced 4.0v cells was stopping it going lower than 45v.
Any opinions appreciated
after using a mobile phone charger to equalize all the cell groups i put it on a full charge. the charger finally went into balancing mode for the first time in the year ive had the 52v battery. didnt know battery has to be switched on to enter balancing mode and it was quite out of balance.
All the cell groups now read 4.1v total 57.6v. previously 7 at 4.2v 7 at 4.0v-4.1v total 58.2v. After over 24hrs off charge the voltage hasnt dropped all still 4.1v.
Although ive lost .6v capacity i guess this is due to some of the cells being unable to reach 4.2v anymore .So the BMS has dropped those that can to their level. Is this drop in capacity overall from 58.8v when new to 57.6v after 1700 miles 11mths use unusual? im thinking maybe the hard use..being a 30amp bbshd,along with always draining fully and not getting balanced has caused more than just age wear?
is it possible a few discharge charge/balance cycles will creep it up a little . will have to see if it will now go to the LVC of 42v. before one of the unbalanced 4.0v cells was stopping it going lower than 45v.
Any opinions appreciated
Your charger doesn't have any sort of balancing mode. It's a standard CC/CV charger that holds the current at a constant value (written on it) until it approaches the maximum charge voltage (written on it). It then switches over to hold the maximum voltage constantly by applying whatever current is necessary up to the maximum.
It's the BMS in the battery that does the balancing. There's a bleed resistor on each of the 14 channels. On each channel, there's a transistor to control the bleed resistor. The transistor opens whenever the cell voltage is above a threshold value of about 4.15v. It will allow about 100 miliamps to drain through the bleed resistor to ground, until the cell drains down to the 4.15v, when it switches back off.
That's why your battery is 58.8v hot off the charger, then goes down a bit.
During the time the bleed resistors are open, you can feel the BMS getting warm, because the excess charge is transferred into heat. It's also the reason why it's imperative that you always charge your battery to 100% until you get the green light. If you charge to cell voltages below 4.15V, no balancing can happen.
The 4.15v is an arbitrary value for the sake of explanation. It varies from one BMS to another. In principle, they all work the same, but there are some differences in the voltage values that the switching occurs.
Just for the sake of the full story, were you experimenting with charging to less than 100% to try and extend your battery life?
It's the BMS in the battery that does the balancing. There's a bleed resistor on each of the 14 channels. On each channel, there's a transistor to control the bleed resistor. The transistor opens whenever the cell voltage is above a threshold value of about 4.15v. It will allow about 100 miliamps to drain through the bleed resistor to ground, until the cell drains down to the 4.15v, when it switches back off.
That's why your battery is 58.8v hot off the charger, then goes down a bit.
During the time the bleed resistors are open, you can feel the BMS getting warm, because the excess charge is transferred into heat. It's also the reason why it's imperative that you always charge your battery to 100% until you get the green light. If you charge to cell voltages below 4.15V, no balancing can happen.
The 4.15v is an arbitrary value for the sake of explanation. It varies from one BMS to another. In principle, they all work the same, but there are some differences in the voltage values that the switching occurs.
Just for the sake of the full story, were you experimenting with charging to less than 100% to try and extend your battery life?
hi dave yeah i meant bms balancing not charger.i meant i could see the charger periodically turning on and off after green light.no never charged to less than 100% always green light plus few hrs, but i never had battery switched on during charging before.never saw the charger ever come back on ,this is the first time.
the battery used to be 58.8v but not been above 58.2v for a long time.now 57.6v.but the fact all cells are the same 4.1v is surely an improvement compared to the situation at the beginning of my thread.
Yes, that all makes sense. the only question now is whether the cells are shagged. I hope they're not, but all the info you've given doesn't give me enough reason to bet against it. Lets cross our fingers and see what happens during your next rides.
Sounds like they have lost capacity and will not deliver good range at high discharge.
If you try high discharge watch the voltage sag to see by how much.
Before I knew much about cells, rating and discharge etc,etc, I had a pair of 29E's and they were used a few times derestricted which did in for them. That was nearly four years ago, they lost capacity and only charged to 4.14v and still do today. They are good for local riding and have a range of 25 - 35 miles down from the 50 -55 originally, the 25 -35 mile range is conditional if I use PAS 3 then sag is a bad and range is <16 miles. So I stick to PAS 2.
If you try high discharge watch the voltage sag to see by how much.
Before I knew much about cells, rating and discharge etc,etc, I had a pair of 29E's and they were used a few times derestricted which did in for them. That was nearly four years ago, they lost capacity and only charged to 4.14v and still do today. They are good for local riding and have a range of 25 - 35 miles down from the 50 -55 originally, the 25 -35 mile range is conditional if I use PAS 3 then sag is a bad and range is <16 miles. So I stick to PAS 2.
Hi neal.i didnt ride far enough today for a full test.However i was pleased to see i used only 6.3v of the 57.5v full charge to do 14.2 miles. that inc plenty of hills,pas2 mainly approx 18amps.with fair bit of 21-24amps, WOT & bit of PAS1..a good mixture basically.voltage drop on the display was a max 4v at WOT moments.on charge at mo.looking fward to seeing if it goes to the LVC of 42v tomorrow and what full range will be.
when new this sort of use wld have given typically 21-23miles range. 27miles using mainly pas 1 approx 13amps and bit more power for hills.
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today rode 26miles on PAS1&2.was pulling 10-12amps on the last mile to home ,uphill all the way.voltage hovering around 44v without cutting out 45v at rest. Started out at 57.5v. when the battery was newer id get 27miles with similar power use. reckon it wld have gone down to the 42v LVC. Next run ill use plenty of full power.see how long it lasts. It certainly responds the same as it did when using WOT.
karls special sauce setting on bbshd 30amp controller (5 levels PAS)neal.
trying keep current at 55% & current decay 1 at the mo.
on the subject of KC & current decay. the settings dont seem to function as id imagine. on say 70% KC, EXCEPT PAS1,theres no reduction whatsoever of amps,even on the flat or slightly downhill,up to speed etc.gradually reducing the KC only has the effect of lowering the max amps in each pas level.which the bike then pulls continously in all but significant downhill,which causes a slight decrease. changing current decay steadily lower doesnt seem to have any effect.
today when i reduced the KC from 70% to 55% it just reduced PAS 1 max from 13-14 down to 10-12 & PAS 2 from 17-19 down to 14-16 . As i said tho its only on PAS1 that economy occurs and will drop to 5-6 on flat 0.5-1 downhill. All the other levels amp draw stay constant. The KC setting baffles me.
Ah, ok BBSHD.
Now you say not surprised about battery range, sound like cells are still reasonable.
Now you say not surprised about battery range, sound like cells are still reasonable.
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Hope so,going to give it a mix with plenty of full power today see if it can still gives 20miles.
i rechecked electroncycles battery charging instruction on their site and the leaflet with the battery.neither mention the batt must be ON to achieve balancing.my batt never got a proper first use balance of 12hrs stated as important nor any over its year of use,as it was always OFF during charging. I suppose this has caused the considerable imbalance,and harmed capacity ,with only 7 cell groups able to reach 4.2v when not balancing.And all at 4.1v now its finally getting balanced. Always running to the LVC prob hasnt helped,an occasionally leaving fully charged for cpl days...sadly its a learning curve?
Any thoughts on the way the economy ramp back with KC doesnt occur except on PAS1. it works better on all the PAS levels on my bbs01.An thats set at 100% KC?
ive brought this up as you know in previous threads ,but still no one can give an answer. settings just DONT function as the well known programming guides suggest they will.
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Seems all good.today blasted around using plenty of mid 20s amp draws,rough offroad, hills,stretches of road at 30mph. Covered 19miles with still 46volts at rest at the end. last few hundred yards was giving it blasts of WOT 30amps.didnt cut out at all despite the display showing voltage dipping below 41v. LVC set at 42v. this is as good as i got in the past.
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