Most baby toys take multiple C or D cells in series. They run about $1 a piece, and "can't" be recharged. I was able to recharge then about 3-5x using a bench PSU and a VERY low charge current (75ma), but it takes forever, and you loose about 30% of the remaining capacity each charge. One of my next projects is to use my battery tester to see how viable it is to recharge different alkaline cells, but I digress.
My son's swing, which takes $4 worth of batteries, only lasts about a week of regular use. I purchased a big box of old modem 18650 packs a few years back from BatteryHookup, and they were about 50¢ each, and can be recharged potentially thousands of times. You might see where I'm going with this by now.
I got a pack of small, 2 amp, boost converters ( https://a.co/d/ciwwtnE ) on Amazon for about $1 each, and soldered one up with an 18650 holder, mini blade fuse, and gator clips. The boost converter is the limitation for now, it steps up to a minimum of 5 volts, so it only works in things that need at least 4 cells in series, but that's a good portion of children's toys. Next, I'll get a buck converter that can drop the voltage down to be used in single battery devices.
I don't currently have a BMS installed on the 18650 slot, but the cell is charged in a dedicated 18650 charger, and I replace it every 2 days, before it gets below 50%. I'm not super concerned with damaging a dirt cheap secondhand cell, if there was a fire, it would most likely be in the charger, which is in a safe location away from my kids. As I typed that out I realized how bad of an idea that is, and now have a 1s BMS on the way. Seems dumb to take that risk over a $2 PCB.
My son's swing, which takes $4 worth of batteries, only lasts about a week of regular use. I purchased a big box of old modem 18650 packs a few years back from BatteryHookup, and they were about 50¢ each, and can be recharged potentially thousands of times. You might see where I'm going with this by now.
I got a pack of small, 2 amp, boost converters ( https://a.co/d/ciwwtnE ) on Amazon for about $1 each, and soldered one up with an 18650 holder, mini blade fuse, and gator clips. The boost converter is the limitation for now, it steps up to a minimum of 5 volts, so it only works in things that need at least 4 cells in series, but that's a good portion of children's toys. Next, I'll get a buck converter that can drop the voltage down to be used in single battery devices.
I don't currently have a BMS installed on the 18650 slot, but the cell is charged in a dedicated 18650 charger, and I replace it every 2 days, before it gets below 50%. I'm not super concerned with damaging a dirt cheap secondhand cell, if there was a fire, it would most likely be in the charger, which is in a safe location away from my kids. As I typed that out I realized how bad of an idea that is, and now have a 1s BMS on the way. Seems dumb to take that risk over a $2 PCB.
