UKJ Posted January 14, 2016 Posted January 14, 2016 This is from another thread, "The balancing function will not be triggered if any of the following is true: 1. batteries already un-balanced to certain degree 2. charger open voltage outside 66.9V to 67.6V 3. stop charge when charger's LED turns green." Does anyone know if this holds true for a KS14c 800w, 680w/hr mark 3? As I build RC heli battery packs and solder a balance lead to each and every battery is this done on this EUC as well? As far as I know the only way to do perfect balance charging is by having this wiring configuration which would mean that a 16 cell pack would have a + and - providing current AND 17 leads for balance, is this the case? Thanks, ukj
Keith Posted January 15, 2016 Posted January 15, 2016 Did you not already get this question answered? The charger has nothing to do with balancing on an EUC, it's function is to limit the current (constant current) and then limit the voltage once that has risen to the maximum pack voltage. At that point current will drop and the charger indicates green (usually) when the current has dropped below a certain level at which point the pack is deemed charged. The BMS board connected to, and part of, the battery pack has each of the 16 cells connected individually to it (your 17 balance leads! ) Compared with a high quality RC LiPo charger which truly "balance charges" I.e. Keeps individual cell voltage differences to a minimum during charging; most BMS have quite a crude balancing mechanism, which simply clamps each cell to a maximum voltage (often as high as 4.25V which,I think, is too high). Effectively there is a circuit, probably based on a Zener Diode, which shunts charge current around the cell once it reaches 4.25V thus holding that cell at voltage whilst allowing others to continue to charge. One problem with this is that the shunt current is limited (lower than 50mA in one spec I saw), so the ability of the BMS to balance cells is limited, if one or two cells are low the charger will go green whilst they are still charging, as the shunt limit current will be low enough to trigger the charge complete indication on the charger, leaving it on would allow those to catch up as the charger usually continues to supply current. Similarly, if one or two cells are high, the current limit in the shunt circuit can be overloaded allowing e voltage of those cells to continue to rise unless the BMS is clever enough to restrict the charge current itself in that situation - something I've seen RC chargers do, but haven't seen in BMS specs. Should the charger voltage get too high then the shunt for every cell will be active and the BMS will protect the pack, providing the voltage is not so high that the shunt current limit is exceeded - that is why the stated limit to charger open voltage. i do not know the actual specs for the KS BMS, not sure anyone else here does either?
UKJ Posted January 15, 2016 Author Posted January 15, 2016 @Keith To answer your question, no, it is not until now that I read your above post that I have a much better understanding of what happens during charging, thanks! ukj
dmethvin Posted January 15, 2016 Posted January 15, 2016 1 hour ago, Keith said: The BMS board connected to, and part of, the battery pack has each of the 16 cells connected individually to it (your 17 balance leads! ) i do not know the actual specs for the KS BMS, not sure anyone else here does either? Are you completely sure the KS BMS balances each cell individually? That's a LOT of balance wires for a 680Wh battery. My Firewheel pack (32 cells) balances in groups of 4. Here is a pic.
esaj Posted January 15, 2016 Posted January 15, 2016 1 hour ago, dmethvin said: Are you completely sure the KS BMS balances each cell individually? That's a LOT of balance wires for a 680Wh battery. My Firewheel pack (32 cells) balances in groups of 4. Here is a pic. Weird, I've never opened the pack that far, but I believed it was 2 * 8S per pack, with both pack in series... and there would be 2 cells in parallel when balancing. The trouble is, if you have 4 cells in parallel, and 32 cells total, you could only have 32 / 4 = 8 cells in series? I'm a bit sleep-deprived right now, so it could be I'm just not thinking straight here... Or is it balancing 2S2P per wire (using 7.2...7.4V per series)? EDIT: Looking at the picture again, that's 2 negative and 2 positive ends of the cells welded together... so it looks like it's one balancing wire per 2 cells, with the same balancing wire (of course) acting as the "virtual" ground for the next pair. I thought at first that the cells would be similarty welded in the other end too, but of course they're "zigzagging" through the pack (bad ascii graphics follows): Pack 1 Pack 2 ----- ------------ ----- <-> ----- ------------ ----- || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || ------------ ------------ ------------ ------------ ----- ------------ ----- <-> ----- ------------ ----- || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || || ------------ ------------ ------------ ------------
Chriull Posted January 15, 2016 Posted January 15, 2016 If you look at the batteries in detail you'll see, that only 2 cells are in parellel. The reason 4 cells are connected together is that the "positive End" of a "two pack" is connected to the "negative End" of the next "two pack"
esaj Posted January 15, 2016 Posted January 15, 2016 1 minute ago, Chriull said: If you look at the batteries in detail you'll see, that only 2 cells are in parellel. The reason 4 cells are connected together is that the "positive End" of a "two pack" is connected to the "negative End" of the next "two pack" Thanks, just noticed that and edited my post with a bit of ascii "graphics" to show how I think it goes...
Keith Posted January 15, 2016 Posted January 15, 2016 4 hours ago, dmethvin said: Are you completely sure the KS BMS balances each cell individually? That's a LOT of balance wires for a 680Wh battery. My Firewheel pack (32 cells) balances in groups of 4. Here is a pic I was trying to keep things simple. Every series connected cell needs to be balanced I.e. 16 balance circuits for a nominally 60V pack. If there are 32 cells it is a 16S2P pack and there is no reason that the parallel pairs should not be welded together and balanced as if they are one cell of twice the capacity. As @Chriull has said your picture shows 2 cells in parallel with the negatives of two cells connecting to the positive of the next 2. If it is a 16S pack there will be 17 wires in total connecting the 16 series balance circuits.
zlymex Posted January 21, 2016 Posted January 21, 2016 To answer the question, we need either ask KS or open one of the shrink wraps and figure ourselves out. I did open the 680Wh pack of a KS-18A that might be relevant to KS-14. There are four protection ICs(SH367004) with balancing function. From the Chines datasheet(English version not found), it says if the voltage of any cell reaches Vob, it will start the balancing function for the cell. I did measured the voltage and it start at 4.20V. (Vob is programmable anywhere from 3.1V to 4.4V in 50mV step, and the balancing action is pulse modulated.)
Cranium Posted January 23, 2016 Posted January 23, 2016 On 1/21/2016 at 8:55 AM, zlymex said: There are four protection ICs(SH367004) with balancing function. From the Chines datasheet(English version not found), it says if the voltage of any cell reaches Vob, it will start the balancing function for the cell. I did measured the voltage and it start at 4.20V. (Vob is programmable anywhere from 3.1V to 4.4V in 50mV step, and the balancing action is pulse modulated.) Ninebot uses the same ICs. I'm trying to find an english version as well.
UKJ Posted January 24, 2016 Author Posted January 24, 2016 On 1/23/2016 at 5:53 AM, Cranium said: I'm trying to find an english version as well. Please post if and when you find please. ukj
Cranium Posted January 25, 2016 Posted January 25, 2016 16 hours ago, UKJ said: Please post if and when you find please. ukj I've learned quite a bit about the IC and how it is integrated into the Ninebot BMS over the past couple days. Let me know if you have anything you were trying to figure out that I might be able to help with. No luck on the english version but here is something I got off of google translate and formatted for the features: SH367004 features: · SEL0 / SEL1 pin switching section 3/4/5 series application · Precision voltage detection function: (for a single power-saving core) o Overcharge protection threshold voltage: 3.3V - 4.5V (50mV per step) § Threshold voltage accuracy: ± 25mV o Overcharge release voltage protection 1: 3.2V - 4.5V § Threshold voltage accuracy: ± 50mV o Over-discharge protection threshold voltage: 1.8V - 3.0V (100mV per step) § Threshold voltage accuracy: ± 50mV o Over-discharge protection release voltage : 1.8V - 3.4V § Threshold voltage accuracy: ± 100Mv · Two discharge overcurrent detection functions: o Discharge overcurrent protective threshold voltage: 0.05V - 0.3V (50mV per step) § Threshold voltage accuracy: ± 15Mv o Discharge overcurrent protective threshold voltage: 0.2V - 1.0V (100mV per step) § Threshold voltage accuracy: ± 100mV · Two charge overcurrent detection functions: o Charging overcurrent protective threshold voltage: 0.05V - 0.3V (50mV per step) § Threshold voltage accuracy: ± 15mV o Charging overcurrent protective threshold voltage: 0.1V - 0.5V (100mV per step) § Threshold voltage accuracy: ± 40mV · Discharge temperature protection: o Charging temperature protection threshold temperature: -20 ° C, -10 ° C, 0 ° C § Threshold temperature accuracy: ± 2 ° C (typ) · Discharge temperature protection threshold temperature: 50 ° C, 60 ° C, 70 ° C o Threshold temperature accuracy: ± 2 ° C (typ) · Balancing: o Balanced turn-on threshold voltage: 3.1V - 4.4V (50mV per step) § Threshold voltage accuracy: ± 25mV · Disconnection detection function · External capacitor can be set to delay the overcharge protection, over-discharge protection delay, delay discharge overcurrent protection delay and charge overcurrent protection delay. · Charge / discharge overcurrent protection delay 2 and delay the internal temperature protection Fixed · CTLC / CTLD pin priority control CHG / DSG pin output · Wide operating voltage range: 3V - 26V · Wide operating temperature range: -40 ° C ~ 85 ° C · Can be cascaded · Low power consumption: o Normal operating current consumption: 25μA (typ) o Low power mode current consumption: 4uA (typ) · Package: 24-pin TSSOP These go great with the block diagram and typical 5 cell schematic This information was re-posted from this thread:
zlymex Posted January 25, 2016 Posted January 25, 2016 7 hours ago, Cranium said: Overcharge protection threshold voltage: 3.3V - 4.5V (50mV a file) Those 'a file' thing is actually 'per step'
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