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Battery recharging - external to outboard

wynjim55

wynjim55

Regular Contributor
Would it be safe to attach a mains power battery charger to a battery installed on a boat while it is still wired in but isolated from the outboard motor by use of an open switch? I don't intend to permanently wire in the charging unit, just trying to make it more convenient than removing the battery from the boat after each use.

Charger / Battery / Outboard (starter motor)
charging.jpg
 
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mikcrwbr1: my battery sits under the fixed rear seats on my boat and the +ive terminal is at the back, to remove the +ive terminal I have to disconnect the -ive and unclamp the battery to get to the +ive terminal. I'm just trying to make recharging simpler hence the desire to use the switch. The one you linked looks like a good one, I picked a cheaper one as it is only to disconnect the cable and it only needs to run maximum current while the starter is cranking, with no other load at the same time (radio, lights, fish finder, etc) it should be ok. I do like the look and function of the one you linked as it would allow for a second battery for backup starting, I only run one battery though and don't need the added functionality of that switch. Thanks anyway.

guyjg: I was hoping to only sit the charger in the boat when it was needed, it is for a trailer stored boat. I understand that the optimal situation is to have the charger wired to the battery, currently I have to remove the battery from the boat and have been using the alligator clips that came with the charger. If this was a lived aboard craft I would certainly be using a better charging unit permanently wired in. Thanks for the comment.
 
I might look at removing the alligator clips I currently have and replace them with eye terminals I can attach to the junction points on the diagram above. The cable from the junction points to the battery is a lot heavier gauge than the charger output leads.
 
If you are using the charger when the engine is not running and the key off there is no reason for a switch...if there is a reason i been breaking a rule for 50 years...just dont crank the engine with the charger attached...if the charger is dedicated to just charging the boat then add a permanent pigtail to the battery and replace the clips in the battery with a matching plug or receptacle....trolling motor plug and receptacle works well but will cost you about 30 bucks..i have a emergency portable light that i put one of those plugs on...the other option is for one of the trickle chargers that Guyjg mentioned.. i am running 3 of them on a campboat for the batteries on aux stuff like the sewer treatment plant and bilge pump..they come with an inline disconnect plug that will do what you want..a word of caution here...if you are going to leave them on a battery 24/7 get the 1 amp one...1.5 max..i have had a 2 amp one that would eventually boil a battery dry...i do now rely on those type chargers to charge a trolling motor battery overnight..
 
Thanks for the tips all, I use a 2.5A unit only for as long as is necessary to return the battery to full charge as indicated by the LED on the charger, occasionally I check with a multimeter to see that the charger is correct. I only ever leave a battery on charge overnight if I am sure it has had a hard time cranking a starter motor continuously without time for the charging system to help bring things back up (such as fixing problems at home and using the starter lots without being able to run the motor), and know for sure I will get up early to check progress. I know not to "overcharge" batteries by leaving things connected too long, I wouldn't suggest a charger as high as the one I have, apart from overcharging I've heard that more gentle charging is preferable anyway. I just didn't check the specs when I bought this unit to be honest (assumed cheap would mean low output without properly researching matters - have had this charger for some time - when it dies I'll replace it with a more suitable unit but the last one I had went for years not being used as often as this one). I really don't want to leave this in the boat, it's only a day-use boat and the charger also sees use on other applications, but the insulated connection tail suggestion sounds good.
 
i meant to say i do not rely on these chargers to charge a run down trolling motor battery overnight...
 
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