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post #11 of 33 Old 03-27-2013
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Re: Battery Bank – Parallel or Series

It does make a difference, especially in larger battery banks.

Here's a good discussion:

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Bill
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post #12 of 33 Old 03-27-2013
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Re: Battery Bank – Parallel or Series

Hi Bill,

Thanks for the link. I'm still trying to noodle it out and there are some interesting ideas in the link. Maybe I'll change my battery setup this year.

Scott
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post #13 of 33 Old 03-27-2013
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Re: Battery Bank – Parallel or Series

Quote:
Originally Posted by btrayfors View Post
It does make a difference, especially in larger battery banks.

Here's a good discussion:

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Bill
And these differences are measurable over time with the equipment Bill & I use.

I think EnerSys/Odyssey Battery sums it up nicely.

Odyssey Battery Technical Manual - Parallel Connections

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."



Rolls
Trojan
Deka/East Penn
Odyssey
US Battery
Crown
Lifeline

and many others, all suggest & show taking loads from opposite ends of a parallel bank or opposite corners of a series parallel bank. It is the suggested installation by every battery manufacturer I know of when wiring parallel or series parallel. As banks get larger star tapping winds up being more efficient but is harder to do correctly.





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post #14 of 33 Old 03-27-2013
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Re: Battery Bank – Parallel or Series

Mainsail,

I see your quoted info as a failsafe issue, which is a good point and reason enough to connect the leads to separate batteries. I'm still trying to noodle out why connecting them that way would make a difference as to there longevity.

Scott
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Re: Battery Bank – Parallel or Series

Quote:
Originally Posted by NautiG View Post
I'm still trying to noodle out why connecting them that way would make a difference as to there longevity.
To use a car analogy, it's like rotating your tires. The front ones get more wear since they are the ones turning the vehicle. To even out the wear, you move the front ones to the rear and vice-versa. If you don't rotate, then your front tires are gonna live a shorter life than your rear ones.

Same thing for batteries.


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post #16 of 33 Old 03-28-2013
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Re: Battery Bank – Parallel or Series

Quote:
Originally Posted by NautiG View Post
I'm still trying to noodle out why connecting them that way would make a difference as to there longevity.
Sometimes having other people do your research and following their recommendations makes sense and is the way to go.

Then follow the links and read some more.

When I first was introduced to this concept, I, too, said, why. Easy answer is that it gets the electrons all flowing through the entire string of batteries instead of just the first one.

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Re: Battery Bank – Parallel or Series

Quote:
Originally Posted by NautiG View Post
Mainsail,

I see your quoted info as a failsafe issue, which is a good point and reason enough to connect the leads to separate batteries. I'm still trying to noodle out why connecting them that way would make a difference as to there longevity.

Scott
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Because the end connected battery sees more use/activity than the others especially when you have batteries with low internal resistance. Now stack poor terminations on top of that, corrosion on the posts etc. etc. and the batteries don't "load share" as well as when cross connected. When not under load they all eventually balance out but when taking a charge or being loaded they usually do not share and share alike.

I quite often take measurements of used batteries that are both end connected and cross connected. The cross connected batteries are almost always is significantly better balance. The end connected batteries always show the "connected" battery in the worst shape and then it moves towards best shape. This is because the first battery is seeing more work and the "circuit" simply wants to move though it rather than through the bank to complete the circuit.

It is not common to find the far end of the string still within spec but the first battery to be toast. My test equipment does not know from Adam how the batts were connected but it tells the performance story quite well...

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Re: Battery Bank – Parallel or Series

I love it when I get something right

Lessons learned are opportunities earned.
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post #19 of 33 Old 03-29-2013
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Re: Battery Bank – Parallel or Series

One thing to add to this scenario is that all the jumper cables have to be the same length. Thanks. Steve S.
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Re: Battery Bank – Parallel or Series

Hmmm. I remain skeptical that the wiring of the leads makes much, if any difference in battery longevity or performance.

The Smartguage link provides a lot of numbers and a theory, but no calculations because "the calculation is incredibly difficult to do." This despite promising at the outset of the article that he will show us the "maths".

Mainsail provides some anecdotal evidence that battery life and performance will be degraded. However, after using the google machine to research "parallel battery bank wiring", I do not see a consensus that this is true, or that there is one correct way to wire the leads.

In fact, one of the links I found was to a rather lengthy cruiser forum discussion of the issue in which Mainsail was one of the participants. There didn't seem to be any consensus among the "experts" in that discussion. And the thread seemed in danger of devolving in to Solarstick territory.

I may switch up my wiring just because, why not? But I remain unconvinced that it would make any difference. If it really makes as much a difference as the Smartguage people insist, I think there would be more agreement that this is true, and some solid experimental evidence to back it up.

Scott
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