How much total pack voltage drop per day is normal? I think I’m seeing around .05v per day with the bms and an anti spark equipped esc (Stormcore) plugged in. Should I unplug the very thing from the pack and see how much it self drains just sitting?
Delta has also increased to .008v, I know the pack isn’t charged and isn’t balanced at full charge probably, but in general what’s considered a max acceptable delta? (I’ll go ahead and guess you might say “it depends on your tolerance for risk”, but I’m really just asking for a rule of thumb here since I have no frame of reference)
Absolutely. There’s no way the pack voltage drop can be checked if we have unknown amounts of current being drawn by any attached electronics. The pack must be fully disconnected from everything.
After the first 24 hours (after charging) in my experience the voltage drop is typically about 3mV/day for a cell for a freshly charged cell. Multiply that by the number of cells/p-groups in series for the pack voltage drop. For a 12S pack that’s about 36mV per day.
This number can vary…2mV…4mV…but your drop shouldn’t be a lot more than this (per cell per day).
This will slow down by a LOT as the cell voltage drops. There is very little capacity change (leakage) needed for a certain voltage change at full charge. But at lower cell voltages there needs to be a really big capacity change (lots of leakage) to get this same amount of voltage drop.
I know you just want a single easy to use number but there is no rule of thumb, not even wild guesses. It completely depends on your pack and how you will use it (cutoff voltages, etc.).
Lots of people will give you their completely guessed rule-of-thumb number but that’s just because we hate not having one. It’s not based on anything other than they haven’t had problems with a pack having that delta. It’s a useless for anyone else.
Bottom line…smaller is better. 8mV is tiny though…tiny.
I’m not nearly as concerned about the actual delta as that depends on how charged the cells are and what balancing they’ve had. I’m usually only concerned if the delta is growing quickly over time.
For example, if you had a 8mV delta for the pack 24 hours after charging this week but next month you had a 50mV delta I would be thinking that you had one or more cells that had failed or were reaching the end of their life.
But if you had a pack that has had a 50mV delta (24hrs post charge) for months then I wouldn’t be worried at all. I would just think that’s what your balancer finishes the pack at.
Personally, because of different balancing algorithms and effectiveness, I feel that a delta of 30mV near full charge is not a problem. At 50mV I would be paying more attention. At 100mV I would be checking for “leaky” p-groups and/or what my balancing settings were. I love seeing a balancer finish off with the pack at a 2mV delta but that is just my OCD. It’s not actually needed.
Hmm…I guess those are rules-of-thumb after all.
But they are just my personal choices. Some people freak out when a delta gets over 10mV. Choose the delta you feel comfortable with based on how your pack is behaving over time. It’s much less of a concern with a higher pack discharge cutoff voltage and/or a decent balancer than it is if you bring the cells down to 2.5V or something very low when riding and/or don’t balance often or at all.
I have this chibattery 10a charger with what I think is an XLR(?) plug. I’d love to switch the plug to work with my existing charge port and match my 4a charger (2nd pic)
Is this easily doable? What’s the name of the plug on the 2nd pic? Can that connection handle a 10a charge?
Wasn’t sure where else to post this… appreciate any advice.
That looks like an SP13, and they’re rated for 13A IIRC.
Pretty easy, you pretty much chop off the old connector, determine the polarity and pinout of the charger cable and connector respectively, and then solder it together accordingly.
Gonna need a picture of your specific BMS to answer this. They used to use JST XH connectors, but they recently changed to a locking JST, and I haven’t confirmed what that one is yet.
Either way, you can almost certainly find what you need on Digikey, Mouser, or Ebay. If it’s JST XH:
Either that, or you change your lipo to AS150s. It’s a bit of a bitch to get 8awg wire into XT90s cleanly w good joints. Those wires soak up a bunch of heat. If u have trouble, dm me and I’ll show u how I went about it.
What soldering station do u have?
Edit- also, print or buy a case for the Kweld. Much safer to operate
That’s what I did and it’s a royal pain, don’t even attempt it unless you have a 100W soldering iron or better with a chisel tip or you’ll just melt the XT90
