This is a 15v power adapter which is ideal for charging many jump starters that have a dc input and will replace the original one supplied.
This is a power adapter which delivers continuous fixed 15v dc power output, it can be used to safely and reliably charge the battery in your jump starter.
We recommend using a 14/15v adapter to charger the 12v battery
Charging should be higher voltage than the 12v battery so as to prevent the battery wanting to discharge back into the adapter,.e,g, car 12V batteries charge at 13.8V. so ideally to charge your battery you need a DC 14V / 15V adapter.
Leaving the charger on any longer than 10 hours can damage the battery, so we recommend a 9-10 hour charge time but always keep a check that the battery doesn't overheat.
The original adapter that was supplied with your jump starter maybe 12v but its likely to be the old style heavy unregulated chargers, that usually deliver alot higher voltage than 12v to the battery.
Sealey Roadstart RS103 v2+ RS10 jump start Uk mains power supply adaptor cable - B06XFRZ88V