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Old 20-06-2012, 08:34   #1
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12v Electrical Systems (Class 101) helprequest

Where should I start the learning process?

At work I had my own little experiment 4 x 6v batteries (2 parallel and 2 in series) wired to a car adaptor and the smallest inverter I could find for charging my iPod. (the office safety manager was not impressed but never told me to disassemble it)

I understand the basics.

Parallel battery setup (12 + 12 = 12)
Series battery setup (6 + 6 = 12)
Both parallel and series battery setup ((6 + 6) + (6 + 6)) = 12
(lurking on this forum) I understand why the lengths of wire should be about the same. (resistance and loss)
So what is next?

For example is there a benefit of 2 x 12v batteries vs 4 x 6v batteries. I think the latter should have a deeper pool to draw from, but that is about the limit of my understanding.

Scott
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Old 20-06-2012, 08:59   #2
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Re: 12v Electrical Systems (Class 101) helprequest

There is no practical difference electrically. If they are all 200AHr batteries, for example, you will get 400AHrs @ 12v.
The 6v batteries will be each be lighter which makes carring them easier( but there is more of them) and 6v batteries (and 2v) are more often true deep cycle batteries, but there are still some true deep cycle batteries that are 12v.
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Old 20-06-2012, 09:32   #3
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Re: 12v Electrical Systems (Class 101) helprequest

Whats next....I'd say learn about how batteries are sized in relation to the demand/load, then how they are charged, i.e. smart chargers.
Then fuzes and breakers, i.e. types and sizes.
That should keep you busy for a little while.
Use our search function...the google box.
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Old 20-06-2012, 09:47   #4
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Re: 12v Electrical Systems (Class 101) helprequest

Battery Basics

Battery Fundamentals

BatteryStuff Articles | Guide to Understanding Flooded, AGM, and Gel Batteries
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Old 20-06-2012, 09:56   #5
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Re: 12v Electrical Systems (Class 101) helprequest

You're the man...well done.
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Old 20-06-2012, 10:09   #6
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Re: 12v Electrical Systems (Class 101) helprequest

Here's another one with tons of links:

Electrical Systems 101
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Old 20-06-2012, 10:10   #7
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Re: 12v Electrical Systems (Class 101) helprequest

One thing about series connected batteries. A high resistance connection at one of the post can cause the whole bank to get cooked/overcharged.

Especially when there is a large charging source. Last week a customer called me to tell me he had a problem. "all of my battery tops are cracked and leaking acid everywhere"

My initial diagnosis of the problem, was a run away alternator based on the fact the Mr Customer had just returned from a 6 hr run. This battery bank was 1 year to the week old. It was made up of 8 x 8 volt Interstate bats to make to make 32 volts, 4 x series, 2 x parallel. Mr Customer installed the bank. I installed a new Outback inverter, AC panel, 50 amp alternator and BatMon, along with bat fuses and bat switches. The bats were installed to a shelf not in boxes and cribbed only on three sides.

I counseled Mr. Customer on the need to put the batteries in spill proof boxes and secure to said shelf on all 4 sides as well as tie downs. He said "you don't worry about that I will put the bats in boxes, and secure them".

He paid $225.00 US dollars for each of these bats, a grand total of $1800.00. They were murdered after one year of life, they spilled and spewd battery acid all over the engine room, he's very lucky that the boat didn't burn to the waterline.

Final diagnosis after inspection and removal of the bats. 1st Mr. Customer had never gotten around to putting the batteries in boxes, or cribbed and tied down said bats. 2nd the jumper on one of the series connected bats developed a high resistance connection. This was caused by a poor crimp, and the fact the bats were able to move around while underway.

This connection turned one of the paralleled banks into a 28 volt nominal, said 50 amp alternators job was to charge the bank at 39.5 volts, this caused the alternator to actually charge much higher in amperage and voltage to bring the 28 volt bank up. This cooked 7 out of 8 of the batteries, the only bat that didn't crack and spew was the one with the high resistance connection.

To solve the problem, 8 new 8 volt Trojans to make the bank, all new battery cables made by me this time. All in boxes and secured properly. The alternator sent to the shop for testing, and a rework of the regulator to externally controlled, and the addition of of a Balmar M632 4 step regulator, with temp sensors for each bank.

I will only install smart charging/regulation, but if you don't install temp sensors to the smart charging sources then the charging source is going to do what it's designed to do...charge to 2.5 volts per cell(FLA's).

With out temp sensing, and with a high resistance at the cell level or the series connected bat you will end up with a potential fire, or at the very least murdered bats.

Lloyd
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Old 20-06-2012, 10:24   #8
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Re: 12v Electrical Systems (Class 101) helprequest

Thank you for all the great information. It's good to have homework sometimes.
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