# 6V versus 12v



## headrush (Jan 20, 2008)

Here is a question that has been going through my mind over and over again;

Which is better a group of 24 6v 200 amp/hr or 12 12v 35 amp/hr batteries (is there Deep Cycle 12v with higher amp/hr rating?)?

And why does 12v seem to be the batteries of choice?


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## mattW (Sep 14, 2007)

The 24 6V batteries are better since they will give you the same pack voltage but with much more stored energy (= longer range). There are higher Ah 12V batteries, here is a 216Ah example. The reason that most people go with 12V over 6 is because the pack ends up being slightly smaller and lighter and requires less wiring, i.e. its just a bit easier. 6V batteries are generally made with a much tougher construction that 12V and have been found to be more reliable in number of cycles than 12V ones. So 6V batteries are 'more' deep cycle than 12V and generally have higher Ah ratings.


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## headrush (Jan 20, 2008)

So the negatives for 6v is more wires, more batteries and possibly more space and weight. The positive is more range, longer life, and stronger construction. 

So if I were constructing an EV at 144v then it would probably be better to try and run one with 24 6v batteries rather than 12 12v. If I can squeeze them in and make them fit.

Are the chargers more expensive or more complicated for a 6v array?

I do notice your 216Ah is about $660 at 112.2lbs (51kg) before shipping. Where a 6v MK with 200Ah is going for $229 at 68lbs (30.91kg). So if my calculations are correct, I would get 12v, 400Ah, and 136lbs (62.73kg) for $458, before shipping and... tax.

Again it seems that the 6v system is looking better and better.


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## rankhornjp (Nov 26, 2007)

headrush said:


> So if my calculations are correct, I would get 12v, 400Ah, and 136lbs (62.73kg) for $458, before shipping and... tax.
> 
> Again it seems that the 6v system is looking better and better.


Actually, you would have either: 12v 200Ah (series) OR 6v 400Ah (parallel). You can't add volts AND amps, it depends on which way you wire them, which one adds up.


I contacted my local battery shop (The Battery Source) and they have the US2200 6v, 225Ah, 59lbs, for about $80 a piece if you buy more that 20. Check them out if you have one near you. http://www.batterysource.com/


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## headrush (Jan 20, 2008)

Well continuing with this thread, the idea is which is better. The next question I have is what is a Puekerts? I have never heard of this before, and I am lost on what it calculates, what it means in the EV world and how you determine it.


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## davej401 (Jan 30, 2008)

Ok here is another one. If I only have room for 12 batteries would it be better to go with the 72 volt (6 volt bats) system using a higher amp hour rating. Or would it be better to use a 144 volt (12 volt bats) system with 3/4 the amp hour rating of the 6 volts. I have the 6 volt set up lead acid 220 amp hour now but I am looking at switching to 12 volt amg probably yellow tops.


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## elevatorguy (Jul 26, 2007)

headrush said:


> Well continuing with this thread, the idea is which is better. The next question I have is what is a Puekerts? I have never heard of this before, and I am lost on what it calculates, what it means in the EV world and how you determine it.


Puekerts is explained in the wiki under battery 101a, near the bottom of the lengthy battery explaination. It is how quickly a battery will discharge under high loads, lower number is better. 


Note how batteries that have a high Peukerts Exponent will quickly run out of 
capacity with high loads. Here, the low-exponent battery will last over 100 
minutes with a 50 ampere load, while the high-exponent battery will last about 
20 minutes. Thus, anytime you deal with large loads relative to the battery 
capacity available, chose a low-exponent battery. This is why many wheel-chairs 
and other electrically motorized vehicles use AGMs. 

This chart answers why starter batteries are built to have a low Peukerts 
exponent. Otherwise, they'd simply not be able to an engine for more than 
a few seconds. However, the thin plates that allow flooded cells to work as 
starter batteries also make them too fragile for deep-cycle use.


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## headrush (Jan 20, 2008)

Okay I get this. Your article and the article from this site helped a lot. Also their equipment look interesting as well.

So let me recap what we have been saying:

6v batteries will give you a longer range because of their higher amp/hour rating. They will last longer on average, and they are cheaper per battery than their 12v cousins.

But 6v Batteries are a bit heavier and they take up more room. 

So would it be safe to say that the 12v batteries might be better in a car, small car, because of the size and weight restrictions, but 6v batteries are better in larger vehicles that can handle the space and greater weight.

Any comments, questions, or advice on this?


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