Notifications
Clear all
Topic starter
2021-05-18 2:33 am
hi all. dunno if this question goes here. but this is the situation. i bought from a neighbor a toy car where for my kid to ride on. they where getting rid of it cause it couldn't charge anymore. so i got it. first i checked the power adapter with the multimeter and it wasn't delivering a constant 12v current it was oscillating 3v, 7v, 11v, 4v, etc... so i jump started the batteries with my power supply and cut the wire of the adapter connecting it to my power supply and started trying to charge the batteries with it. at 12v it wouldn't pull any current, when i reached 15v the batteries started charging, pulling 200ma. after around 30mins the batteries started pulling 300ma so i lower the voltage to 14v and it went back to pull 200ma. i kept it like that for 2 hours. the batteries charged but not completely. i could used the car today for about 5mins and it went off. my question is. can i safely charge the batteries with my power supply at 14v? (still they won't charge at 12v) i think the charge control is inside the car but im afraid to burn the batteries, more than that, to start a fire. can i buy then a 14v charger and use it to charge the car with it? the specifications of the original charger are 12v 700ma.
thank you for any help.
This topic was modified 3 years ago by talamasca
2021-05-19 5:08 pm
It will be important to know what type of batteries are in the car. If the pack contains li-ion of li-po batteries a 12V pack will usually have 3 batteries in series (3S) and as many in parallel as needed to provide the current requirement. There should also be a BMS (Battery Management System) that keeps the batteries from over charging and discharging. The optimum charging voltage for an 3S pack is 12.6V.
If for some reason pack is made up of nicad batteries a 12V pack takes about 10 batteries in series to get to 12V. The optimum charging voltage for 10 nicads in series will be 14.5V.
2021-05-20 1:19 am
You can charge a battery with a power supply as long as you can monitor the current and adjust the voltage. I do that with lithium-ion batteries.
Usually if the battery needs charging it will be a constant current and at low voltage. As the battery charges at that low voltage you will see the current decrease, then you can turn up the voltage a bit more to get the current back up. Once the battery gets close to being topped off (for a lithium-ion cell it is 4.2 volts) you can set the voltage its rated voltage and you see the current decrease.
Also I have a protection boards on my packs so if the power supply does something bad the board still protects the batteries and my house. : )