Battery Chargers

John, it wasn't the trickle tag that worried me it was the 6.5 Amp 
rating.  Recharging a sealed battery at too high a current may cause a 
rapid build up of gas, increasing the risk of explosion.

There are many different approaches to charging batteries but a good 
rule of thumb is to recharge at 10% of the battery capacity.  Eg. for 6.5 
Amp.hour battery (a good size for spotting) use a  650 mA charger or 
thereabouts.  Then charge for about 14 hours - 10 hours to recharge + 4 
to account for losses.  Cheap chargers are a bit of a compromise, unless 
you monitor the current you are never quite sure when it is fully 
charged.  AT least with a 12V plug-pack overcharging is unlikely.   

Cheers,
Llew Rintoul.