Question: Batteries in Parallel, all loads from main + & -

[captstu]

There is one seldom experienced problem with parallel batters that hit my boat and nearly caused a serious problem:

Very occasionally, one of the cells in one of the batteries shorts - when this happens, you suddenly have many 12 volt batteries trying to charge one 10 volt battery.

When this happened to my 900 Ah AGM battery bank, the shorted battery got very, very hot - charred the material around it - and emitted a very biting, probably toxic gas that smelled strongly sulphuric.

Fortunately, I was able to switch off most of the back, remove the wires from the defective battery, and get it off the boat. Had he have not detected the problem very shortly after the short began, I believe the boat would have been lost.

Fuses, circuit breakers, or current limiters are absolutely essential for every battery in the bank, especially when the back capacity grows in 2 KW increments as mine did with very large AGMs.

So far as I can tell, this isn't in the regulations or the ABYC guidelines - but I don't know why not.

[Tikka]

Mr Big
Answer is simple, YES you can connect + anywhere, where is convenient,
You "+" line has the same property across the system.

[Wotname]

Originally Posted by Tikka

Mr Big
Answer is simple, YES you can connect + anywhere, where is convenient,
You "+" line has the same property across the system.

This is only true if your system has 0 ohm conductors and terminals.

I haven't seen such a system for awhile now...

Mr Big, some of other posts provide better solutions to your problem IMO.

[StuM]

Originally Posted by Wotname

This is only true if your system has 0 ohm conductors and terminals.

I haven't seen such a system for awhile now...

Mr Big, some of other posts provide better solutions to your problem IMO.

Not to mention 0 Ohm internal resistance batteries

[dave948]

At less than .078 ohms per thousand feet of cable I wouldn't worry too much about not having "0 ohm cable" . Electrically all the points of connection are the same.
Also fuses are much more reliable than breakers and would be my 1st choice for circuit protection.

[jwcolby54]

Originally Posted by captstu

There is one seldom experienced problem with parallel batters that hit my boat and nearly caused a serious problem:

Very occasionally, one of the cells in one of the batteries shorts - when this happens, you suddenly have many 12 volt batteries trying to charge one 10 volt battery.

When this happened to my 900 Ah AGM battery bank, the shorted battery got very, very hot - charred the material around it - and emitted a very biting, probably toxic gas that smelled strongly sulphuric.

Fortunately, I was able to switch off most of the back, remove the wires from the defective battery, and get it off the boat. Had he have not detected the problem very shortly after the short began, I believe the boat would have been lost.

Fuses, circuit breakers, or current limiters are absolutely essential for every battery in the bank, especially when the back capacity grows in 2 KW increments as mine did with very large AGMs.

So far as I can tell, this isn't in the regulations or the ABYC guidelines - but I don't know why not.

I had this happen to a riding mower battery. It read 9 volts across the battery.

The only failsafe for this is to have a fuse between each battery and a buss bar, then a main fuse between that buss bar and the rest of the boat.

You are a lucky man that you were aboard when it happened.

[CarlF]

I can't remember who told me about connecting positive and negative feeds at the opposite end of a bank but I always have. I did a quick internet search and found these:

The Lifeline battery manual figure 5-2 page 13

http://www.lifelinebatteries.com/manual.pdf

And this link:

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

I don't know enough to evaluate whether these are right.

[Ironman162]

My sixpence worth is its not the thick wiring that burns but the thin ones.
Im inclined to fuse each circuit rather than the supply wire. The supply wire is switched to serve the house or start the engine.
My boat is wired like that for a very long time without any trouble.
In a car for example, the starter motor circuit is along the same lines.
Its a bit off the topic I know and yes I agree with the busbar approach. It makes trouble shooting much easier.

[Wotname]

Originally Posted by StuM

Not to mention 0 Ohm internal resistance batteries

Yes
I should have included that - thanks for the reminder

Originally Posted by dave948

At less than .078 ohms per thousand feet of cable I wouldn't worry too much about not having "0 ohm cable" . Electrically all the points of connection are the same.
Also fuses are much more reliable than breakers and would be my 1st choice for circuit protection.

And what are your thoughts regarding this "The problem is that in very low resistance circuits (as we have here) huge differences in current can be produced by tiny variations in battery voltage."

Which has been shamelessly cut and pasted from the Smart Gauge link others have provided.

[Maine Sail]

Originally Posted by jwcolby54

I had this happen to a riding mower battery. It read 9 volts across the battery.

The only failsafe for this is to have a fuse between each battery and a buss bar, then a main fuse between that buss bar and the rest of the boat.

You are a lucky man that you were aboard when it happened.

The problem with this is the fuses between will not blow if designed to handle normal systems loads eg; engine starting, windlass, winches etc.. When one battery shorts internally, to essentially become a 10V battery, that battery begins getting chronically over charged and this is what creates the heat and gassing.

There is rarely enough current in these situations, flowing into the shorted battery, to pop a fuse because it can't drive enough current with the small voltage differential. This is why the ABYC does not require fuses between each battery.

[Wotname]

Originally Posted by Ironman162

My sixpence worth is its not the thick wiring that burns but the thin ones.
Im inclined to fuse each circuit rather than the supply wire. The supply wire is switched to serve the house or start the engine.
My boat is wired like that for a very long time without any trouble.
In a car for example, the starter motor circuit is along the same lines.
Its a bit off the topic I know and yes I agree with the busbar approach. It makes trouble shooting much easier.

Yep, it will work but at the expense of battery life and as such is not best practice.

The way to OP boats is wired can be vastly improved with only a small effort and IMO, we should give him the option of best practice. He will then decide how much less he is willing to accept.

If he had only one battery (like most cars), the advice would be different .

[Maine Sail]

Originally Posted by bluegreen

To answer your exact question, no. It wont make any difference. Everything connected to that parallel "node" sees the same voltage. Current will flow determined by resistive loads, not placement. Making the bus bars is the same theory and easier to work with but you asked Can I and yes you can.

Actual battery manufacturers disagree with this......

EnerSys, the inventors of the Odyssey TPPL AGM battery as well as the inventors of the Optima orbital AGM battery, and the leaders in standby back up systems, military applications and other industrial battery applications spells out correct parallel wiring better than I can.


Quote = Odyssey/EnerSys Technical Manual:


"Parallel Connections


It is common to have batteries connected in parallel to

achieve a desired amp-hour capacity. This is done by

connecting all the positives to each other and all the

negatives to each other.


Typically the positive and negative leads to the load

are taken from the same battery; usually the leads from

the first battery are used. This is not a good practice.

Instead, a better technique to connect the load is to take

the positive lead from one end of the pack (the first or last

battery) and the negative lead from the other end of the pack.

The two methods are illustrated above. Solid lines and

arrows indicate positive terminals and leads; broken lines

and arrows indicate negative terminals and leads.


In both illustrations, the positive leads are connected to

each other; similarly the negative leads are connected to

each other. The only difference is that in the first illustration

the positive and negative leads to the load come from the

first and last batteries. In the second case, both leads to

the load are tapped from the same battery.


The first schematic is recommended whenever batteries

are hooked up in parallel to increase battery capacity.

With this wiring, all batteries are forced to share both charge

and discharge currents. In contrast, a closer inspection

of the second schematic shows that it is possible for only

the battery whose terminals are tapped to support the load.

Implementing the first schematic eliminates this possibility

and is therefore a better one."








Trojan shows the same with series parallel wiring..

[Wotname]

Originally Posted by bluegreen

To answer your exact question, no. It wont make any difference. Everything connected to that parallel "node" sees the same voltage. Current will flow determined by resistive loads, not placement. Making the bus bars is the same theory and easier to work with but you asked Can I and yes you can.

Maine Sail has already refuted this so there is no point in me adding anything except to say "Welcome aboard CF".

I note this is your first post and although I don't know if you have been a long reader or not, it behoves us to welcome you in a friendly manner. You will find that we have vastly different opinions and knowledge on many subjects and as cremates go, we can be a rambunctious and motley lot at times. Nevertheless I have "educated" here and the experience is mostly enjoyable.

One thing for sure, there are true experts posting valuable information all over the threads of CF and I trust you will work out who they are and perhaps also will be one of them.

Welcome

[Wind River]

I believe the question has been answered here so I will make another note.

Having a yellow wire for the positive lead to your windlass may be just to help you distinguish it from other positive cables, but yellow wire in a 12 volt system is usually used for negative connections.

It might be a problem for someone working on your boat at the other end of that wire, thinking it is a ground connection.

[boater 86]

I used 4, 6v, trogen gulf cart batteries 2 in series = 12v, two banks over 400 amps. Used w/ west marine wind generator and 180w of solar power, Connected by combiner/regulator monitor, Almost never needed more power, (wind generator n/g sailing down wind). Used 2 alternators to avoid side wear on crank shaft. At least 2, 3 position bat. switches, proper size wire, shrink tube, Circuit Breakers. Only used engine when using water maker or anchor winch.-- Raggedy Ann, Caliber 33