connect charger to: mains first or battery first ?

[monster]

hi guy

i was always tought to connect to battery first to avoid sparking the battery connection with chargers that float up to high voltage with no load. is this still the prevailing logic with chargers that only float up to end of charge voltage?

 

[Zoot Katz]

The instruction sheet that came with my Nexcell 24V 4A NiCd/NiMH chargers clearly states to plug in the charger, turn it on and let it do its self test before connecting the battery pack. It has XLR plugs and I've never seen a spark when using them.

 

[ElectricEd]

My 6A charger provides a spark with either method. However, IMHO you should turn on the charger first and then connect the battery. As you can never be sure of charger's output design, hanging 50-60V onto an output with nothing coming in on the input may cause a failure.
SATA connectors on Hard drives have elongated pins that make first contact when being plugged in. These are ground and +ve with a resistor between it and the the real but slightly shorter +ve supply. This resistor allows a soft start to the powerup sequence, reducing in-rush current.
It's probably not a good idea to change to a different connector for reasons of standardisation, but you could use a resistor in series with the charger and have a switch across it. Have the switch open when connecting and close it for the charging sequence.
Use a 1K 10 watt resistor. This should reduce the splatt and will be able to handle the heat if you forget to close the switch.

 

[rkosiorek]

i think that this is too general a question. the answer will depend on the design of the charger.

many sophisticated chargers that do a self test or check battery conditions and ambient temp need to be powered up before being attached to the battery.
most simple CC/CV designs don't care which is connected first. some which automatically determine polarity want the battery connected first.

best to read diretions that came with the specific charger. failing that it seems safer to connect the AC first, then the battery.

rick