Safe battery charging.

[peterjohnston99]

Hi,
I have W202 with an almost, but not completely flat battery. There's enough charge to power the locks and interior lights but not to start the engine.
What I'd like to know is can I safely charge a maintenance free type sealed battery with an old fashioned, i.e non smart, 6 amp charger. The car is very soon to be scrapped so I don't even need it fully charged, but I do need to start it.
Many thanks to anyone who can advise, I've had a search around the forum but haven't found anything directly related to this.

 

[Dec]

Yes, connect the charger to the battery first, and then switch on the charger at the mains.

Dec

 

[grober]

Charge the battery out of the car as a precaution and just keep an eye on it. Any signs of overheating- switch off the charger and let things cool down- wear safety goggles/glasses if you have them.

 

[190]

If you have an accurate voltmeter monitor the charging voltage at the battery terminals. You should see it slowly rise over a period of hours as the charging current falls. The idea is to stop charging when the battery starts to gas as a sealed battery will eventually vent off through the pressure release and lose some electrolyte. Depends on the battery spec but if you stop charging at 14.3 volts that should be safe for any battery.

 

[peterjohnston99]

Much obliged for the advice. Eye protection is a given. I'm afraid I don't have a volt meter but will proceed with caution.

Many thanks,
Pete.

 

[MancMike]

If it's a 6A charger, and a 36Ah battery, it'd take 6 hours to fully charge, so 3 hours is roughly a half charge. So look at the battery capacity.

Amp hours work like this;
If something uses 1A, and you have a 1Ah battery, it'll last 1 hour. If you connect something that uses 500mA to that battery, it'd last two hours. A 2A draw would last 30 minutes. etc.

It's a bit different with charging, but generally the idea.