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Old 29-06-2015, 18:30   #1
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Batteries in Parallel

G'day All,

I have 6 X 100 Amp Hour Deep Cycle House batteries linked in parallel for a 12V system, and have recently had it suggested that by mixing up the negative leads, linking them randomly as opposed to being paired with their positive leads, battery life can be extended and battery efficiency enhanced. Does anybody have experience of this or put in to practice ?
Cheers MC.
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Old 29-06-2015, 18:48   #2
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Re: Batteries in Parallel

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank
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Old 01-07-2015, 07:28   #3
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Re: Batteries in Parallel

Assuming you are using adequate gauge cables, the voltage differences due to wiring imbalance are small compared to inherent battery variations over which you have no control. Making fine adjustments in wiring is like putting lipstick on a hippopotamus.

Even under starting currents any imbalance gets corrected within a second by battery to battery current once the starting is completed.

Organize your wiring for the minimum total length and best mechanical arrangement.
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Old 01-07-2015, 07:55   #4
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Re: Batteries in Parallel

Not true. Although the differences in cable resistance are small, high current during starting can actually result in meaningful voltage drop and imbalances between the batteries when they are connected randomly. There is a best way to wire batteries in parallel. Go to:

www.smartgauge.co.uk/batt_con.html

for a good explanation of this.



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Old 01-07-2015, 10:11   #5
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Re: Batteries in Parallel

It is a common misconception despite being perpetuated and mis-quoted frequently.

Its not that voltage differences do or do not exist during starting, but the fact that they are small in comparison to the internal differences in battery impedance. You are going to all that trouble to save 1/10 volt during starting an engine when in fact the inherent battery parameters are an order of magnitude larger. If they had not been in parallel and you tested each battery for voltage supplied during starting loads, their voltage would differ much more than the minor drops due to wiring layout.

Within a second after starting is completed, the batteries will all be at the same voltage due to battery to battery current so any imbalance only lasted a few seconds. Each battery contributed energy for the starting function but once completed they all are AT THE SAME VOLTAGE so each had contributed its share of the energy that it could release between the initial voltage prior to starting and the rest voltage after starting.

Eventually you took xyz amp-hours out of the battery bank to start the engine. The net effect of wiring differences boil down to heating loss which again is insignificant. For maximum efficiency the wiring layout should minimize wiring resistance.
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Old 04-07-2015, 02:42   #6
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Re: Batteries in Parallel

This question is somewhat related to the forum topic. Assume you have two twelve volt batteries in parallel and two six volt batteries in series. Assume again that the total amp-hours are the same. Wouldn't the impedance of the twelve volt batteries in parallel be much less than the impedance of the six volt batteries in series. Wouldn't the charging resistance of the twelve volt batteries be much less? Thanks.
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Old 04-07-2015, 08:39   #7
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Re: Batteries in Parallel

All lead acid batteries are the same make up. 2 volt cells hooked in series. Three for a 6-volt, and six for a 12-volt. If the amp/hour rate is the same, two 6-volt in series is the same as one 12-volt.
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Old 04-07-2015, 11:37   #8
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Re: Batteries in Parallel

Quote:
Originally Posted by Mark Cusack View Post
G'day All,
I have 6 X 100 Amp Hour Deep Cycle House batteries linked in parallel for a 12V system, and have recently had it suggested that by mixing up the negative leads, linking them randomly as opposed to being paired with their positive leads, battery life can be extended and battery efficiency enhanced. Does anybody have experience of this or put in to practice ?
Cheers MC.
I am expert for solar,off grid instalation and small solar power plant.
and this sugestion is thru.
I and experts only for batteries in UPS,forklift systems have noticed that failure cells from the negative side of battery. and that is systems where parallel compounds made from 100-200 m2 cables and biger.
Also this problem noticed Rimac car in early development, but he solve the problem whit electronic.

you simple change place in battery and bay some time. also regularly check battery voltage.Normally lot depends on the manufacturer of cells and tehnology use. Casting lead: Gravity,medium presure or high presure machine
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Old 04-07-2015, 13:07   #9
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Re: Batteries in Parallel

Two 12 volt batteries in parallel would have 24 cells while two 6 volt batteries in series would have 12 cells. If the AH capacity of the 12 volt battery is one-half of the 6 volt the total output of both banks is the same - voltage & AH's. If you assume the impedance of each battery is identical then the total impedance of the six volt batteries is Z1 + Z2 = 2Z. The parallel battery bank's impedance is Z1*Z2/Z1 + Z2 = Z^2/2Z = Z/2. The parallel bank's impedance is one-fourth of the series bank. Thanks.
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Old 04-07-2015, 14:18   #10
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Re: Batteries in Parallel

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Originally Posted by sstuller View Post
Two 12 volt batteries in parallel would have 24 cells while two 6 volt batteries in series would have 12 cells. If the AH capacity of the 12 volt battery is one-half of the 6 volt the total output of both banks is the same - voltage & AH's. If you assume the impedance of each battery is identical then the total impedance of the six volt batteries is Z1 + Z2 = 2Z. The parallel battery bank's impedance is Z1*Z2/Z1 + Z2 = Z^2/2Z = Z/2. The parallel bank's impedance is one-fourth of the series bank. Thanks.
I have to correct my arithmetic before somebody else does. The parallel bank has 12 cells and the series bank has 6 cells. Thanks
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Old 06-07-2015, 20:31   #11
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Re: Batteries in Parallel

I can't come close to understanding that heavy math. So it must be wrong.
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