On-Board Charger

[reelapeelin]

SET-UP...boat has 4 batteries...1 cranking, 1 accessory, and 2 trolling motor batteries...1 on-board charger, presently hooked up to trolling motor batteries only...charger has 2 legs

WANT TO SPLIT each leg using 2 Perko 1 & 2 position switches so as to switch from charging trolling motor batteries to cranking and accessory batteries(will unplug charger while switching)...switches only have poles for positive leads, so I'm thinkin' negative leads permanently from charger to both batteries on each leg

ANYBODY got opinions/experience re this set-up?

[macojoe]

Have no experince!! Sorry! But I have always heard, and done it this way. That you should disconect the - not the + as the pos will cause spark when turned on and off and that neg. will not??
Just a thought.
Good luck!!

[reelapeelin]

thanx for the reply maco...but i'm gonna UNPLUG charger before switchin'...i figger that'll keep the sparkin' down

[chumbucket]

From the sounds of what you described, you should be using two selector switches. Negatives are always common and do not pass through the selector switches. Only positive cable lead switching. Not clear on whether you want to be able to charge all four batteries or just two. It also sounds like you've got a two bank charger. They do make four bank chargers but they get a little pricey. I would think that for normal use during the boating season, you should only be concerned about charging the two trolling motor batts. During winter months, the batteries should be removed from the boat and stored indoors prefferably not on a concrete floor. Set them on some plywood or something. Then you can charge them on a rotating basis. I usually trickle charge them for one day per month. It's not good for batteries to drain to the point that the acid turns to water then freezing occurs.

[chumbucket]

Another question. Is your trolling motor a 24 volt motor and the two batteries for the trolling motor wired in series instead of parallel like starting & deep cycle batts?
Need more info to help ya out. Was this setup already in the boat when you bought it or did you install it?

[reelapeelin]

hey chumbucket...sorry i'm so long gettin' back...you got some good questions...just wanna charge 2 batts a time...i did install myself and been workin' great for over 4 years...now using portable charger to heat up 2 batts not on on-board charger...if i can successfully switch each leg of ob charger then i'm really slickin' out cause it's a plug and forget deal!!!

my biggest question is how are the batteries gonna get along permanently wired on negative only side while functioning separately when not charging...sounds complicated to me, but i think it'll work

[chumbucket]

Yeah, what you're wanting to do is a little complicated but I would think that the charger leads could be run through a switch to change from one set of batts to the other. There is a potential problem with the common negative posts, but that's a concern whether charging or not. When multiple batteries are tied in together, the two are only as good as the weakest battery. It's important to maintain them equally because the weaker of the two will drain the good batt.

[reelapeelin]

thanx Chum...now we're gettin' to the heart of my concern...but i've also been told neg only leads cannot draw down good batt from bad batt(neg only=no flow of power)
anyway, that's what i'm hearin'

[chipde]

hi folks - just reading thru this thing -
I'm an EE - and can assure you that there's no problem hooking all the - poles of your batteries together !

only concern I have is making sure that you DO NOT HOOK UP THE 4 BATTERIES TO THE CHARGER AT THE SAME TIME - this might create a problem for your charger since you put 4 batteries in parallel which decreases the resistance you put on that charging circuit - that might be overloading the charging circuit and burn it..
e.g. if you normally run 2 batteries on the charger and you add another 2 you basically half the resistance to the charging circuit.
So make sure, that the way you configure the switches to the batteries, do not allow you to connect the 4 batteries to the charging circuit at the same time.

something like this using 3 switches would work: make sure switch1 is not a (1,2,or both) switch, but a 1 or 2 switch !! switch2 and 3 can be (1,2, or both) switches..

charger+ --->in switch1>output1>in switch2>output1>batt1
>switch2output2>batt2
>in switch1>output2>in switch3>output1>batt3
>switch3output2>batt4

[reelapeelin]

Hey Chipde...you da man!! That's just the feedback i was hopin' for...the 2 switches i've already bought are 1, 2, off, and both...obviously it's the both position that'll get me in deep trouble, knowing that i'll be SURE not to use that position(going back to Boaters World tomorrow...maybe i can swap 'em)
The big thing for me is that the neg connections wont cause problems...thanx for that

[chumbucket]

chipde, good info!
I know it's not related to reelapeelin's question, but for my own knowledge; When batteries are tied together in parallel I know just a common negative won't drain the stronger battery, but if the positive lead selector switch is in the "All" position, couldn't this potentially be a problem without an isolator? I'm just curious because I ran into that problem in the past running both batts on all while running to charge them both. One battery was quite a bit older than the other and ended up eventually draining and shortening the life of the newer batt. I'm a loy more careful now to maintain the two batts equally. Isolators are pricey and I would rather not add too much more to the boat in that respect.
Just curious and thought you'd be able to shed some light on that as well.
Thanks.

[chipde]

Yes, That's definitely a problem if batteries are in parallel without any isolator - they will drain each other - even if the batteries are of the same quality they will drain each other like a yoyo..
I only use the "all" or "both" position when charging up on longer trips, and when starting up after long periods of storage.

I always run a single battery at a time when on anchor and running equipment.. or when running back after I exhausted one hanging on the line..

[chumbucket]

Thanks chipde. That's what I thought and I operate them the same way.

[reelapeelin]

got some things to do this week, but i'm gonna try to set this up in the next few days

thanx for all the info...i'll post how it goes