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Dual battery replacement

cooper999

Member II
Hi all,

I'm planning on replacing my dual purpose batteries, and I want to make sure that I'm dissconnecting them and reinstalling in the correct sequence. I've typically been told to disconnect the negative terminal first, then the positive (for automotive batteries at least). Does this hold true? Complicating the matter is the extra cable (white, see photo) linking the two positive terminals. Should I disconnect this after disconnecting the negative terminals on both batteries?
Any insight is appreciated-just trying to avoid getting shocked.:egrin:

thanks!

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Shelman

Member III
Blogs Author
Your batteries are hooked up wrong.. At first I thought they were wired in sieries but what it looks like to me is that somebody decided they wanted to combine the two batteries into one single bank by wiring them in parallel which is like using your battery combiner switch on the all/both position all the time.
The battery wiring looks like it was originally set up to have two separate 12 volt batteries. you could stay with this system (simply by removing the white jumper) or you could upgrade to a true deep cycle battery bank. You cannot get a true deep cycle system with one stand alone battery however, for a true deep cycle system you need to combine multiple 6 volt batteries (similar to what someone tried to do here but in sieries instead of parallel) hooked up in series so that they double the voltage and make one 12 volt battery bank. Think of it like the way you insert two d batteries into a flashlight one behind the other to double the voltage power and make the bulb brighter. if you put the batteries side by side and draw off the positive end of both batteries at the same time the power is not doubled but there is twice as much battery life but at half the voltage power compared to stacking them end to end. (thats both d cell batteries pointing the same way) Again put them end to end and you have the life of one battery but twice the voltage power. Thus turning two six volt batteries into one 12 volt battery.
So..... What it looks like is somebody wanted a deep cycle battery bank but instead of hooking two 6 volt batteries up in sieries they hooked up two 12 volt batteries in parallel. And then to complicate matters worse they hooked the second factory original positive lead from the battery "one two all" switch up in the middle of the bank.

So my advice is to either simply remove the white wire and return to the mediocre system of two non-deep cycle batterys, or install two new 6 volt batterys for a true deep cycle system, and disconnect the large red wire that is sharing the post with the white wire and cover it with heat shrink to protect it from accidentally becoming energized. This way you would have only one battery bank, but it would be a true deep cycle bank much more usable power.

I would also recommend the jumper (white wire) to be the same size as the main battery cables.

Also you should really fuse your batterys at the the posts (or within 7") and use a real nut on the battery post instead of the wingnuts.


Links below are good reading to get you started towards understanding the system on your boat.

http://www.pbase.com/mainecruising/battery_fusing
http://www.pbase.com/mainecruising/battery_meltdown_averted
http://www.pbase.com/mainecruising/installing_a_smart_plug
 
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Shelman

Member III
Blogs Author
I think the more common danger when messing about with batterys is accidentally creating a short circuit, like bumping a wrench into a positive and negative post simultaneously. Or like a friend of mine did, holding a positive lead in his hand that was touching his wedding ring and then bumping the ring into the engine block which is of course grounded. his wedding ring instantly turned red hot on his finger, it wasn't pretty. I have heard that you should remove the negative lead first but I think it has to do with blowing up a battery not about getting shocked. The danger of a battery exploding is one reason why it is recommended you wear safety glassed while working with your battery.

http://articles.latimes.com/1999/aug/26/news/hw-3902
 

cooper999

Member II
Goodness. The wonderful things you inherit from previous owners! The surveyor inspected the battery setup and his only comment was to cover the positive terminals with boots (which we should have and will do when I replace batteries). So, basically, they are functioning together in their present configuration via the white wire across the positive terminals? We do have a switch to draw from one, the other, or both, but effectually they are both being drawn from no matter what position the switch is in? If I do remove the white wire, is it safe to assume they will function independently?

thanks for your reply!
 

Guy Stevens

Moderator
Moderator
I don't think the white wire is a jumper

I looked at the photo and the two white wires seem to go to those two circuit breakers whose function I cannot derive from this photo.
So they are not jumped together if that is the case. The fact that they are both white wires is strange on a boat, but that is another discussion.

Guy
:)
 

Shelman

Member III
Blogs Author
That makes a lot more sense! good eye Guy :egrin:
Good thing there are professionals scouring this site to keep the amateurs like me in check lol.
Basically my whole previous comment can be disregarded.
 
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cooper999

Member II
Just to close the loop here (because I know everyone is on the edge of his/her seat), I ended up replacing both batteries with no issues. Guy, you are correct-the white wires aren't jumpers and go to the switches in the bottom right of the photo. Thanks for replying (all three of you)-much appreciated!
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Our boat has a molded-in battery compartment and came with a pair of group 24 12-volt batteries.
I measured carefully and there was just enough room for a plastic battery box holding a pair of golf cart batteries. I recently replaced those, after nine years... with two more Trojan T-145+ golf cart batteries. 260 AH.

If you have the height I would heartily recommend the changeover to the pair of six volt batteries.

And yes, we do have a separate emergency/starting battery -- it's an Optima agm spiral cell I put in a decade ago. Still going strong.

There are probably several "right ways" to rig up a battery bank, and one thing I love about this site is finding out how other owners have solved problems in the Real World... !
:)

Regards,
Loren
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Cooper,

While you're in there, rig up battery tie-downs. Some scrap webbing works, probably just screwed to the pan.

Most surveyors look for that, so you might as well comply just for show.
 

cooper999

Member II
Thanks for the insight, Loren. As things stand, the battery compartment is pretty height-challenged. Actually, to compensate for the height of the terminal towers, the PO (previous owner) cut holes out of the wooden cover beneath the berth cushion and covered it with a piece of plywood (1/4" thereabouts) thinner than the width of the cover. Not ideal.

Our boat has a molded-in battery compartment and came with a pair of group 24 12-volt batteries.
I measured carefully and there was just enough room for a plastic battery box holding a pair of golf cart batteries. I recently replaced those, after nine years... with two more Trojan T-145+ golf cart batteries. 260 AH.

If you have the height I would heartily recommend the changeover to the pair of six volt batteries.

And yes, we do have a separate emergency/starting battery -- it's an Optima agm spiral cell I put in a decade ago. Still going strong.

There are probably several "right ways" to rig up a battery bank, and one thing I love about this site is finding out how other owners have solved problems in the Real World... !
:)

Regards,
Loren
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Fitting bigger batteries into our designed spaces is often a challenge.

I find that the cover can often just lie on the deck surface, or even be raised more proud than that, without much effect on the cushion. Worth a test.

A proud cover also means you can remove the seating lip necessary for a flush cover--which gives a bit more room inside the box.

(Yours is molded in, I see, so that doesn't apply here...)
 
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EGregerson

Member III
motor

I have a bit of a worry with the motor installed in a closed chamber with the presence of hydrogen gas (produced by the batteries); are the motors sealed (by the manufacturer) to prevent any arcing or spark?
 

markvone

Sustaining Member
Battery Fuses

Cooper,

Another thing to consider if you change batteries or re-configure the box/pan for the taller Trojan 6volts is that your main battery positive cables should have fuses within 7 inches of the battery terminals per ABYC standards. I was able to easily add Blue Sea battery terminal fuses to my batteries this winter because I (just barely) had the vertical clearance under my cover. Here is a nice description of what I did from MaineSail's website, he contributes to the site regularly:

http://www.pbase.com/mainecruising/battery_fusing

While my boat hasn't caught fire in the past 35 years, it seems electrical issues are the prime cause of fires on boats. When something breaks or I'm working on the system for another reason, I try to upgrade my AC and DC systems to comply with current ABYC standards or to replace older equipment.

Mark
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Fan

I have a bit of a worry with the motor installed in a closed chamber with the presence of hydrogen gas (produced by the batteries); are the motors sealed (by the manufacturer) to prevent any arcing or spark?

Not sure what you mean by "sealed" but the whole engine compartment on our boat (and most Ericson's) is - or should be - force-draft exhausted by the vent fan all the time the engine is operating. This does several desirable things... like provide some additional cooling, control the heat build up around the alternator, and remove any oily odor from crankcase blow by.

Loren
 
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