Hey everyone! I've misplaced the charger for my Voltec 08-00712 portable worklight and I'm trying to figure out the correct voltage for a replacement. The worklight has a 2s2p 18650 battery pack and a barrel plug charging port. I suspect it might need 8.4V or maybe even 12V, but I'm not entirely sure since I couldn't get solid info from the manufacturer. I did some testing with a lab power supply: at 8.4V the battery terminals read ~4.4V, at 12V I got ~6.6V, and it jumped to 14V at 24V, which seems too high. Lowering to 14.3V gave me 8.2V, but I'm wondering if there's some voltage sag happening. Any insights would be greatly appreciated!
3 Answers
Yeah, I’d lean towards 8.4V too, based on your battery configuration. That’s a common voltage for a two-cell lithium set-up. Just make sure whatever charger you use is regulated to that voltage, as going higher can damage the battery. If possible, look at the chips on the board again for any markings that might tell you the specs. Always better to double-check!
Another way to look at this is that if your charger is giving around 14.3V and you're still only reading 8.2V at the terminals, it could indicate a problem with the internal circuitry. Definitely stick with the recommended voltage of around 8.4V for charging to avoid any risk of overcharging. Maybe consider getting a universal charger that lets you set the voltage manually so you can experiment safely!
It looks like you're on the right track! Generally, a 2s lithium-ion setup charges to about 8.4V, but if you’re measuring across the terminals and seeing lower readings, that's normal due to the way voltages can sag when under load. I'd guess a 12V charger should work fine, but if you want to be safe, look for a charger specifically rated for 8.4V for optimal results. Better to go with the voltage intended for your pack to avoid any issues!
Thanks for the clarity! So even though it's showing lower voltages, you're saying 8.4V should be my target for charging, correct?
Good advice! I’ll take another look at the board for any part numbers.