Most cccv esk8 chargers I’ve encountered have a fuse for that.
Mind you that they only do this occasionally on long distance group rides. They just charge regularly at home if they don’t need to be fast.
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I keep finding references to using chargers in parallel but only if connecting them using a Charge Doctor device. You’ve seen riders paralleling chargers without anything on their outputs?
Yea, but that means paralleling is not advised. 
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yeah two riders in my local group does that.
stock ‘dumb’ chargers, and a parallel wire harness
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I’m dumbfounded. My experiences have been so different. Perhaps the less expensive chargers are using a different circuit type that handles this without issues vs the bigger chargers I was testing. I’ll need to hunt down a couple of model numbers and try it out. Thanks!
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LOL…I was muttering and cursing all day yesterday and when I woke up today about a delayed package but it has given me a bunch of time to dive in here!
It will not be a pleasant day when the client wakes up in a few hours though. But delayed packages are not my fault. 
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From what I gathered looking at this the problem is when the voltages doesn’t closely match. Of course they will never match perfectly
One idea I had is to never connect the chargers in parallel first, always charger 1 to pack and then charger 2, this way you don’t have the voltage difference at open circuit
And probably also good to disconnect one of them before reaching the CV phase
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Orr 4 high power diodes? Positives only go to positive and negatives to negative. I imagine if the power supplies give different voltage, one will shut down first while the other will still work for a little while, or bms will shut down and both turn green… dunno. @Battery_Mooch? Whad’ya say?
Only two needed, one on each charger’s positive terminal, forward biased. Some chargers won’t start charging unless they detect the cell’s voltage though and the diode prevents that.
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good talk and discussion Mooch… always great to have another mind(s) to bounce ideas and thoughts off of… as a community we all gain!!
thanks again
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Go hang out at Kung Fu Tea on St. Marks street if you want to see them do this live.
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Hi Mooch, Your reviews are a sort of gospel around here, so it’s awesome to address the legend directly.
I’m probably getting off topic here, but your experience with chargers stood out.
Do you always charge to ‘full’ voltage?
I’m probably splitting hairs and straddling the fence on using a fraction of a battery’s capacity in hovering around nominal voltage vs accelerating aging (cathode oxidization? dendrite formation?) at fully charged/discharged levels. Will both options end up giving negligible differences in total mAh passed through the cell?
The other half of that is that, unless you’re counting coulombs, it seems charging to less than full creates an unknown of how ‘full’ the battery is. LiFePo4 chemistry comes to mind with its flat discharge curve, and (I think?) any charging will spike the voltage by a couple hundredths/tenths of volts. Maybe that would level itself out over the course of a week. Maybe backup power UPS system can live with that characteristic, but that timeframe is a bit impractical otherwise.
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I think you mean only wired for charge
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That’s the feature I prefer on my llt BMS. I can forget the charger cus the BMS cuts it off at 4.21 per cell and only turns it back on when balancing causes them to go under 4.15
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To be clear, Bill is referring to something like this
I have done this a lot with the MDA 4A float chargers as sold by Evolve, Metroboard, enertion, etc…
I’ve done both. Though anecdotal evidence proves nothing… …it’s highly dependent upon the specific charger’s circuit as you noted above. I also had a 10A fuse on each charge port separately.
And yeah, this, I rarely do it. Only if I need a full battery in a jiffy
We would love to hear more about this 
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I do but I don’t really care too much about the effect of charging fully on cycle life as I usually want the longest run time before needing to recharge. If you are not otherwise stressing the cells you can gain a significant increase in cycle life by charging to a lower voltage, e.g., 4.10V or 4.05V for standard li-ion cells. But you will lose up to 10%-15% of your capacity doing this. There is always a frakkin’ tradeoff.
Staying within, let’s say, a 20%-80% SOC range will significantly increase cycle life but you will lose a LOT of run time.
Yup, charging to a lower voltage would reduce the available capacity and you’ll have to do a couple of tests to measure the actual capacity available.
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Thanks for the model number!
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as @b264 mentioned above… sciencing materials commonly used for P-Grouping, and series connections, would always gather a huge following just as your battery testing has…
I’d really like to encourage this science!
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Building bigger and bigger batteries so I can use less of them!
I like 4.10V as a compromise so I’m just falling off the initial voltage cliff. Any lower and I’m driving myself paranoid checking individual P-group voltages a lot more frequently, since I’m not (/shouldn’t be) hitting the BMS’s triggers until a group decides to fall on its face.
You said it
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