Charging Batteries Question??

[K1esoxhtr]

I have two 12 volt batteries tied in series to create 24 volts for my trolling motor. I only have a regular 12 volt charger(not an on board unit)just a standard Sears 6/12 volt charger. Is there some way to set these up so I can charge them with disconnecting each one and charging them everytime indiviually, which could be quite often. Any input greatly appreciated. Thanks

[jeff reed]

Can't do it without disconnecting. You need an on board charger. Sorry

[JimmyJ]

With your current set up you will have to disconnect the two batterys from each other. However you do not need a onboard charger. I have a 24 volt system also and I purchased a 10 Amp 12/24 volt charger here in Northern Minn. from a place called L&M supply in Grand Rapids for $60.00. It works great. Has setting for different charging applications for 12 and 24 volt, is completely automatic (100% shut off when fully charged). It is a Schumacher Model # SE-70MA.
Jim

[TEAM_ALTO]

Yes you can charge two batteries connected in series with one charger. You have to charge one at a time. But you should use a charger with a floating ground(negitive wire not connected to charger case or AC ground), if your battery charger is an older one with a metal case I would not set it on a metal part of the boat. The reason for this is If your trolling motor battery is grounded to the boat and the charger negitive wire is grounded to charger case you'll get a short when you charge the second battery.

I have charged batteries using this way before without any problem, I even used two 12 volt charges at the same time to charge two series batteries.

This is the same as using a two bank onboard charger. A two bank charger is the same as two separate chargers with floating grounds getting its power from the same AC power cord.

[ddh]

Some one might have to help me out here too. My boat dealer told me to simply by another pigtail for the electric trolling motor. He said to just clamp the battery charger onto both of those leads, plug it into the electric trolling motor receptacle and turn the charger on. He said I can charge both batteries at the same time this way. It takes forever and a day but it seems to work. anyway, this is how I do it. Does anyone have any advice on that because it seems odd to me.

[SeaCat]

Not sure but I think I have ruined batteries by doing an equivalent thing. It is a good way to significantly reduce the life of your batteries -- especially if one is significantly more drained than the other.

In effect by connecting the charger to two batteries off the same lead you have created one battery. If one is at a lower charge level than the other the two will try to equalize the available charge and never get fully charged.

Used a Guest battery switch to let me use the trolling motor battery as an emergency starting battery. I used to use the "both" position on it to let me connect the charger to the engine battery and also charge the 2nd battery. Charger would show that both were charged and shut off, but the voltage guage on the boat never showed that they were really fully charged.

Batteries only lasted 1 1/2 seasons at most. Went to two chargers and have not had any problems. Batteries are on 3rd season and still going strong.

Ryan

[TEAM_ALTO]

What is happening is your batteries in your battery compartment are not connected in series but rather the individual battery terminals are wired to the trolling plug. Then on the trolling motor side the two batteries are connected in series.

Seacat is right that when you put in the plug with the pig tails and connect one charger to charge two batteries you can ruin a battery if they are not matched pair batteries. If one battery is not the same state of charge as the other one battery will boil out more water then the other.
Bob

[chatman]

you can use one charger and charge each battery one at a time...but, after using 3 automatic chargers for many many years like schumacher non-onboard 10 amp chargers (they are older technology, about 11yrs)i installed a guest 3bank charger and have found a big difference how the batteries have been maintained. they come up to full charge faster and are maintained at an slightly higher float voltage. plus now i only use one plug and don't have to hook up 3 batteries to the 3 chargers.....spend the money, you'll be glad you did in the long run. and your batteries will last much longer. leaving one battery sit at low charge while you charge the other will put that one battery at about 80% of it full charge capability in a short amount time. the cost of replacing batteries a few times will pay for a good charger.

[Phil T.]

Walmart sells them, too. Same charger, same price.

[Would this work?]

Place a fuse between the batteries the one going from neg of #1 to Pos of #2 then just pull apart the fuse and charge as normal, on battery then the next then re connect the batteries? dont know, just a thought...

[Bluewater]

How do the battery switches work on boats without onboard chargers? When I go to a location I will place switch to 1st bank, then on way back will place switch to 2nd bank. I assume they will then charge equally. Overnight I will place switch to "both". Do both batteries offer a charge if one should weaken if for instance the sump pump is running? Would I ever place to "both" when running to and from a location.

[BATMAN]

I once had a 12 Volt motor with 2 batteries.
I utilized a battery selector switch with battery
#1, battery #2 and a both batteries positions. Wire
battery one with fuse (40A) to position #1, battery #2 with
fuse (40A) to position #2. Jumper outputs of both of
these switches to positive pin of motor receptacle. Jumper
the negatives of both batteries together. Tie either of
the negatives of the batteries to the negative pin of the
receptacle. In either position #1 or #2 you get 12v on
either single battery. In the Both battery position you
get both batteries in parallel or 12v with double current.

This setup makes charging with a single charger easy if
you use a pigtail on your charger and charge directly
though the receptacle. You set the switch to battery #1,
charge it fully, then change the switch to battery #2 and
charge it fully.

I installed an Altus battery checker on the batteries. One
with battery 1 or 2 that matched up to the way I set up the
main selector switch on the batteries.

These selector switches are available from any marine store.
They are usually used on sailboats and larger crusiers. Typically
rated at 100 to 200 amps and run about 40 Canadian. I sure
the switches are US made though.

PS. Make a wiring diagram and have it checked out. 12 volt
batteris are potentially very dangerous.

Good Luck. BATMAN (Canada)

[GU]

http://www.uuhome.de/william.darden/carfaq.htm

To the orig poster,
The referenced 12/24 charger is the least expensive way to do it right. On-board is really convenient. Until you get a better charger:

If your fishing the next day, switch your set-up to parallel and charge your big ole 12 volt system. You will overcharge little if any with your setup & it beats trying to get back out to the boat to switch to the other battery. If you have time, charge separately.

The battery damage stuff is all correct, but I'll suggest most guys using your type of charger are not checking the batteries with a voltmeter after dropping the surface charge or checking specific gravity to determine when to stop, eh? How many actually calculate charge times based on the amount of discharge? Point is that IMO, if the batteries are matched, their condition is similar & your probably not going to cause much more harm charging together than separately because your always over or undercharging anyway.

just in case fyi - typical "fully automatic" chargers such as your Sears job do not shut off when the battery is charged.

Hope this helps. Have fun with the new TM.

[PTC]

Cabelas has a new line of economical onboard chargers. On the low end you could get a 2 bank 8 amp charger that would work for you for $90.

http://cabelas.com/cabelas/en/templates/product/horizontal-item.jhtml?id=0019015015766a&navAction=push&navCount=2&indexId=cat600056&podId=0019015&catalogCode=IE&parentId=cat600056&parentType=index&rid=&cmCat=&_DARGS=%2Fcabelas%2Fen%2Fcommon%2Fcatalog%2Fitem-link.jhtml.2_A&_DAV=%2Fcabelas%2Fen%2Fimages%2Fbuyinfo.gif&hasJS=true