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Old 05-10-2020, 07:22 PM   #43
xxx
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6 v Vs 12 v

Quote:
Originally Posted by seb1899 View Post
Thanks to all who have 'helped to educate me" If two 6's are the best way to go because of plate size capacity etc. why did the automotive industry abandon the 6V battery?

My old old ('53 Plymouth Mayflower) is 6V and the hand held spot light that is a genuine Mopar accessory is 6V.

I am not trying to promote an argument just wondering why 6V was abandoned if it is better in this (RV Application)
The reason is none of the above. First of all, it is economics it has to do with the power factor higher voltage means the wire size is smaller. 12 volt systems supply the same POWER at half the current. Current determins wire size. Wattage equals volts times amps. 12 volts times 10 amps = 120 watts. To get the same power with a 6 volt system you nerd to pull 20 amps hence larger wire and higher cost.
Now there is VOLTAGE DROP. Bad connections = large voltage drop. If you loose 2 volts on a 6 volt system you loose 1/3 of your power. Watts is what does the work. A loss of 2 volts on a 12 volt system you only loose 1/6 of your power.
Manufacturers went to 12 volts for two reasons. Cost of copper wire and less chance of a large power loss because of a large voltage drop. In the end 12 volts is cheaper and the bottom line is larger.
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Old 05-10-2020, 07:49 PM   #44
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parallel 12 volt batteries adds the amp hours...
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Old 05-10-2020, 08:09 PM   #45
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Quote:
Originally Posted by twinboat View Post
I⁶ones in series. That also keeps the starter cable size smaller.
.
There it is!
Cable size (aka wire size) throughout the entire vehicle.
Twice the voltage = half the amperage = wires that are half the size, terminals that are half the size, fuses that are half the size. This means half the copper and wiring harnesses that are much smaller AND lighter.
Also, power transmission is more efficient at higher voltages.
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Old 05-10-2020, 08:45 PM   #46
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By now, this is a chorus, but I'll chime in.

In the world of flooded cell (lead acid) batteries...these observations change when applied to other battery technologies.

Why two 6 volt in series rather than 2 12 volts in parallel.

The advantage of 6 volt batteries.
~ Slightly more robust build.
~ True deep cycle...not "marine" or mixed use.
~ Slightly more usable amp hours in the battery bank.

A good, reasonably priced 6 volt "golf cart" battery will weigh in around 64 to 68 pounds. A competitive 12 volt true deep cycle may weigh in around 60 pounds. As with 1960's vintage Cadillacs, that "ground hugging" weight matters. Thicker plates and "more lead" make for stouter batteries.

Here's a fair Apples-to-Apples comparison:
12 Volt true deep cycle Group 31: https://www.batteriesplus.com/productdetails/sli31mdc
6 Volt true deep cycle type GC2: https://www.batteriesplus.com/productdetails/sligc115

Exactly the same price.
This pair of 12 volts offers 200 amp hours - you get to use 50% (rule of thumb) for 100 total usable AH.
This pair of 6 volts offers 230 total AH (it does not double, because in series the voltage doubles) for a net usable AH of 115.

15 more AH doesn't sound like much until you realize that a standard group 24 12 volt battery that comes on the tongue of most new RVs can only deliver a grand total of about 35 USABLE AH. 15 AH is damned near half of a group 24...extra for the same price: $130/battery. Battleborn LiFePo's by the way run close to a Kilobuck a piece.

So, when the sparks hit the wires, you have enough extra "in the tank" to run your furnace overnight in temperate weather.

Downsides of 6 volt batteries? If one dies, you're toast. With 2 x 12's you can always run on one if the other dies. With 2 x 6's, you can't run on 6 volts.

Now the "gold standard" for inexpensive battery banks is 4 x 6 volt GC2's. Best of both worlds. If any one fails, you still have a pair that can make 12 volts. And, as battery banks go, the make available to you 230 AH of usable power, which is quite a bit if you don't do something silly like suck them dry with a big inverter or have an RV with a "residential" (compressor) fridge.
If you're one to be tethered by a power cord to RV parks, no big deal. But if you boondock, a residential fridge is a real joy killer. If you boondock, you need a 2 way fridge that will run on propane.

A simple, brutal, fact of life. 2 x 5 gallon tanks of propane (actually 4.5 gallons each) contain MORE THAN 20,000 AMP HOURS OF ENERGY. Damned near 100 times (about 87 times) the energy of the gold standard 4 x 6 volt golf cart battery bank!! BATTERIES SUCK as energy storage devices.

With that in mind, those 15 extra amp hours in the pair of 6 volts look mighty good.
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Old 05-10-2020, 09:50 PM   #47
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Your title fits me too.

I learned a few new things from reading
your posts.
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Old 05-10-2020, 10:08 PM   #48
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If you really want an education on rv electricity, check out rvtravel.com free weekly newsletter, specifically, Mike Sokol's electricity articles. Here's a link to his great 12 part series on rv electricity.
https://www.rvtravel.com/tag/no-shock-zone/page/27/
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Old 05-11-2020, 07:18 AM   #49
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Analogy for the non-technical: Think of volts, amps, ohms, and watts as water coming out of a faucet. Volts is water pressure. Amps is how open the faucet is. Ohms is the flow friction between the nearest pump and the faucet. Watts is the amount of water flowing out of the faucet in a given time, a product of pressure and how open the faucet is, reduced by flow friction which increases with the length of the distance between pump and faucet.


For the same number of watts (usage), half the volts requires twice the amps. Twice the amps requires (roughly) twice the cross-sectional area of the wire (not twice the diameter). Another factor is the length of the wire between the power source (battery in this discussion) and the consuming appliance (light bulb, refrigerator, engine starting motor). The longer the wire, the greater the resistance to the flow of current (ohms) and the fewer amps the voltage will push through the wire. Also the resistance produces heat and too much heat will melt the insulation on the wire and cause a lot of excitement. Therefore longer wires require larger diameters to carry the same amps. There are thus two factors controlling the wire gauge necessary: amps, and length. The reason for going from 6 to 12, or from 12 to 24 or 48, is to reduce the size of wire needed, cutting costs, making wire runs easier to construct. I know nothing about this, but I suppose high-tech batteries are lighter for equal capacity and 48-volt batteries may now or soon weight no more than a standard 12-volt.
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Old 05-11-2020, 07:38 AM   #50
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Quote:
Originally Posted by jimmoore13 View Post
By now, this is a chorus, but I'll chime in.



In the world of flooded cell (lead acid) batteries...these observations change when applied to other battery technologies.



Why two 6 volt in series rather than 2 12 volts in parallel.



The advantage of 6 volt batteries.

~ Slightly more robust build.

~ True deep cycle...not "marine" or mixed use.

~ Slightly more usable amp hours in the battery bank.



A good, reasonably priced 6 volt "golf cart" battery will weigh in around 64 to 68 pounds. A competitive 12 volt true deep cycle may weigh in around 60 pounds. As with 1960's vintage Cadillacs, that "ground hugging" weight matters. Thicker plates and "more lead" make for stouter batteries.



Here's a fair Apples-to-Apples comparison:

12 Volt true deep cycle Group 31: https://www.batteriesplus.com/productdetails/sli31mdc

6 Volt true deep cycle type GC2: https://www.batteriesplus.com/productdetails/sligc115



Exactly the same price.

This pair of 12 volts offers 200 amp hours - you get to use 50% (rule of thumb) for 100 total usable AH.

This pair of 6 volts offers 230 total AH (it does not double, because in series the voltage doubles) for a net usable AH of 115.



15 more AH doesn't sound like much until you realize that a standard group 24 12 volt battery that comes on the tongue of most new RVs can only deliver a grand total of about 35 USABLE AH. 15 AH is damned near half of a group 24...extra for the same price: $130/battery. Battleborn LiFePo's by the way run close to a Kilobuck a piece.



So, when the sparks hit the wires, you have enough extra "in the tank" to run your furnace overnight in temperate weather.



Downsides of 6 volt batteries? If one dies, you're toast. With 2 x 12's you can always run on one if the other dies. With 2 x 6's, you can't run on 6 volts.



Now the "gold standard" for inexpensive battery banks is 4 x 6 volt GC2's. Best of both worlds. If any one fails, you still have a pair that can make 12 volts. And, as battery banks go, the make available to you 230 AH of usable power, which is quite a bit if you don't do something silly like suck them dry with a big inverter or have an RV with a "residential" (compressor) fridge.

If you're one to be tethered by a power cord to RV parks, no big deal. But if you boondock, a residential fridge is a real joy killer. If you boondock, you need a 2 way fridge that will run on propane.



A simple, brutal, fact of life. 2 x 5 gallon tanks of propane (actually 4.5 gallons each) contain MORE THAN 20,000 AMP HOURS OF ENERGY. Damned near 100 times (about 87 times) the energy of the gold standard 4 x 6 volt golf cart battery bank!! BATTERIES SUCK as energy storage devices.



With that in mind, those 15 extra amp hours in the pair of 6 volts look mighty good.
Well written
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Old 05-11-2020, 09:37 AM   #51
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Quote:
Originally Posted by jimmoore13 View Post
The advantage of 6 volt batteries.
~ Slightly more robust build.
IMHO, you are not giving 6V golf cart batteries enough credit ! Properly maintained, they will endure many more discharge/charge cycles than any car/light truck sized 12V battery.
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Old 05-11-2020, 09:53 AM   #52
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In parallele you add the AMP and in serie you add the volts.
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Old 05-12-2020, 12:19 AM   #53
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Quote:
Originally Posted by seb1899 View Post
First let me start with the fact that I know nothing about electricity except ON and Off.

The house batteries in my unit are 2 6V in series and I was wondering why it is 6V in series rather than 2 12V in parallel?

Is there a good reason for this?
By now you have heard every version of pros and cons of both a pair of six volt or a pair of twelve volt batteries. If I were in your shoes based on my experience and the posts in your thread when it comes time to replace or upgrade your batteries I would recommend you talk with a batter specialist and look at your options.
If I were you and you had room for four batteries I would stick with the HD deep cycle 6 volt batteries similar to what you have. This way you have two 12 volt banks of 6 volt Batteries. If you only have room for two I would consider the largest pair of 12 volt batteries I could use this way you always have at least one 12 volt power source in the event of a battery failure. If you can do four batteries all the better.
I personally have 8-6 volt batteries or 4-12 volt pairs and plan to double that and add a solar charging system. My coach is total electric so more is better. Just my two cents.
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Old 05-12-2020, 01:04 PM   #54
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A minor point.

There's been considerable effort put into describing the difference in amperage between 6 volt and 12 volt circuits.

Let's be clear, that's a moot point in this discussion. The RV circuit is 12 volts. Other than antiques, there are NO 6 volt RV circuits.

2 x 6 volt golf cart batteries in series make, wait for it, 12 volts. The ONLY place this volts/amps disparity might come into play is with the wire joining the positive terminal of one 6 volt battery to the negative terminal of the other 6 volt battery. EVERYWHERE else in the circuit is 12 volts. You might need to buy about 2' of #2 AWG to make the battery to battery connection.

That holds true with 4 x 6 volt golf cart batteries in series/parallel to ultimately have a 12 volt output.

Double the amps at half the voltage DOES NOT APPLY in an RV application except where the two 6 volt batteries are joined in series.
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