Hello. I'm looking at my options for single cell chargers(I'm going to design my own LVC for the cells), and it seems it's either a case of spending 80 dollars(Including shipping) for a balancer from hobby-city(which also needs a powersupply) or I can build my own!
Ideally, I'd need to charge roughly 20 cell groups "simultaneously"(can be approximated as further explained below).
If 2A is fine, then it seems the L200 chip can be easily adapted to create a 2A CC-CV charger with minimal parts - The projected cost per single cell charger is around $3. But, it'll need a power supply. If I were to use my 12V power supply from my dead computer's PSU, then it seems 24 A is available and so I could allot upto 12 2A chargers but I'd worry about the heat dissipation issues from 12V to ~3V on the chips and I'm not entirely sure what kind of heat sink I'd need and whether I have said heat sink available. 9 volt drop*2 amps ~= 20 watts each which I've heard heat sinking for above 10W is cost-wise impractical, but maybe I have something that'd work? I picked up two somewhat large heat sinks from the robotics meeting, so I think that might work. The other possibility is to pick up a 2 lb. 7 volt switching PSU that's adjustable between 6 to 9 volts and is good for upto around 60 amps, so that'd minimize heating issues while allowing for portability for opportunity charges, but that costs about 53 dollars. So, it's either the computer PSU + 12ish simultaneous charges for 40ish dollars or the 2 lb PSU + 20 simultaneous charges for 130ish dollars.
But, then there's more! I could possibly use a buck converter regulator as charger! The good thing about this is that I could use the power from my computer's power supply more efficiently. The bad news? It seems more expensive. The chip is 3 dollars, a 330 uH inductor seems to be around 3 to 4 dollars(ouch), and the electrolytic and other capacitors, resistors, diodes, mosfets/etc. probably adds another $2 per unit implying a cost of $9 per charger. But, the up side is that I could charge at upto 10 amps, I wouldn't have to worry as much about heating issues, and I could use my 12V computer PSU without heating worries(Although it's limited to ~250 watts, so I couldn't use 20 simultaneous chargers at 10 amps each but I could probably use 10). There's also the option of getting the $50 power supply so I can get 350W charging on the fly. But, it might be feasible to minimize the number of chargers by "switching" between cells, while still getting high charging currents. I.e., a charger feeds a cell group for 30 seconds, it then feeds another cell group for 30 seconds, it switches back to the first and the cycle continues. So, it seems I could build upto 10 of these chargers to satisfy my needs, and it'd come to 90ish dollars and the 2 lb PSU would be another 50 dollars.
So, in essence, it seems I can have slow charging 10 cells at a time for 40ish dollars(Or extremely slow charging for 20 cells use the switching idea for 50 dollars), slow charging for 20 cells for 80 dollars + a 50 dollar psu(so 130 dollars), quick charging for $90 and if opportunity charging is desired, 50 dollars extra for the PSU(140).
I'm not sure if the balancers being sold on hobbycity.com can run off my computer's 12V PSU, so a 200 watt balancer might require that $50 PSU(At a higher voltage) so I'm probably looking at a necessary $50 PSU with that, so the hobbycity one is at like a $140 minimum and they also charge at 200W, I believe.
Hmmmm... I'm liking the quick chargers which matters more for opportunity charging, so I'm trying to think of ways to minimize that cost. Maybe I could only build 5 and then I could use the "switching" idea to distribute the current as needed? Then the cost might be $50+15(switchers) = $65 which could run from my computer's PSU.
The other method is get 11 2Amp single-cell chargers that plug directly into the wall from voltphreaks for 120 dollars or so, and while that minimizes the effort needed for building and design, it's kind of slow and it's not as "compact" as my own custom design could be.
So, if you didn't mind building anything, what would you do for the single cell chargers?
Ideally, I'd need to charge roughly 20 cell groups "simultaneously"(can be approximated as further explained below).
If 2A is fine, then it seems the L200 chip can be easily adapted to create a 2A CC-CV charger with minimal parts - The projected cost per single cell charger is around $3. But, it'll need a power supply. If I were to use my 12V power supply from my dead computer's PSU, then it seems 24 A is available and so I could allot upto 12 2A chargers but I'd worry about the heat dissipation issues from 12V to ~3V on the chips and I'm not entirely sure what kind of heat sink I'd need and whether I have said heat sink available. 9 volt drop*2 amps ~= 20 watts each which I've heard heat sinking for above 10W is cost-wise impractical, but maybe I have something that'd work? I picked up two somewhat large heat sinks from the robotics meeting, so I think that might work. The other possibility is to pick up a 2 lb. 7 volt switching PSU that's adjustable between 6 to 9 volts and is good for upto around 60 amps, so that'd minimize heating issues while allowing for portability for opportunity charges, but that costs about 53 dollars. So, it's either the computer PSU + 12ish simultaneous charges for 40ish dollars or the 2 lb PSU + 20 simultaneous charges for 130ish dollars.
But, then there's more! I could possibly use a buck converter regulator as charger! The good thing about this is that I could use the power from my computer's power supply more efficiently. The bad news? It seems more expensive. The chip is 3 dollars, a 330 uH inductor seems to be around 3 to 4 dollars(ouch), and the electrolytic and other capacitors, resistors, diodes, mosfets/etc. probably adds another $2 per unit implying a cost of $9 per charger. But, the up side is that I could charge at upto 10 amps, I wouldn't have to worry as much about heating issues, and I could use my 12V computer PSU without heating worries(Although it's limited to ~250 watts, so I couldn't use 20 simultaneous chargers at 10 amps each but I could probably use 10). There's also the option of getting the $50 power supply so I can get 350W charging on the fly. But, it might be feasible to minimize the number of chargers by "switching" between cells, while still getting high charging currents. I.e., a charger feeds a cell group for 30 seconds, it then feeds another cell group for 30 seconds, it switches back to the first and the cycle continues. So, it seems I could build upto 10 of these chargers to satisfy my needs, and it'd come to 90ish dollars and the 2 lb PSU would be another 50 dollars.
So, in essence, it seems I can have slow charging 10 cells at a time for 40ish dollars(Or extremely slow charging for 20 cells use the switching idea for 50 dollars), slow charging for 20 cells for 80 dollars + a 50 dollar psu(so 130 dollars), quick charging for $90 and if opportunity charging is desired, 50 dollars extra for the PSU(140).
I'm not sure if the balancers being sold on hobbycity.com can run off my computer's 12V PSU, so a 200 watt balancer might require that $50 PSU(At a higher voltage) so I'm probably looking at a necessary $50 PSU with that, so the hobbycity one is at like a $140 minimum and they also charge at 200W, I believe.
Hmmmm... I'm liking the quick chargers which matters more for opportunity charging, so I'm trying to think of ways to minimize that cost. Maybe I could only build 5 and then I could use the "switching" idea to distribute the current as needed? Then the cost might be $50+15(switchers) = $65 which could run from my computer's PSU.
The other method is get 11 2Amp single-cell chargers that plug directly into the wall from voltphreaks for 120 dollars or so, and while that minimizes the effort needed for building and design, it's kind of slow and it's not as "compact" as my own custom design could be.
So, if you didn't mind building anything, what would you do for the single cell chargers?
), but eventually I need to add the wires and multipin plug, like I had in this setup:
