House bank 6 volt vs 2 volt cells

[pbiJim]

Originally Posted by s/v Jedi

On construction: there is no comparison between a single cell and a battery with multiple internal cells. It is also silly to put that to discussion

I don't think that it's silly to put it into discussion if the person you are talking to is unaware of the reasons why single cell systems are better. I still fall into that category, but my mind is open & I'm working to improve my knowledge base on the subject. I think that I may still need a little more discussion.

[Jim Cate]

Originally Posted by boatpoker

10.5volts oddly enough equals .... 10.5volts. The source is irrelevant.

A fully charged 10.5 volt 5 cell battery contains a lot of energy. A 12 volt, 6 cell battery discharged down to 10.5 volts contains damn little energy.

There is a difference, and Jedi's point is that you may be able to utilize the energy in the 5 cell battery.

It is not irrelevant.

Jim

[Capt Hugh Wilde]

I am looking at Lifeline. Is that my best choice in AGM or is there another brand I should be looking at?
I have done alot of electrical systems but this is the first long range cruising boat I have done. If there is a better AGM I should look at, please let me know.

[deckofficer]

I've used these that are currently out of stock. The site does have some good articles though.
Solar Star Battery

Jedi, your always into high quality, high end stuff. What is your opinion on Rolls?
http://rollsbattery.com/public/specsheets/spec_83.pdf

[s/v Jedi]

Originally Posted by boatpoker

10.5volts oddly enough equals .... 10.5volts. The source is irrelevant.

You may need to know that power equals voltage times amps. Voltage is the same for both, but your empty battery can't supply any amps while the 2V cells can put out hunderds. 10.5 x 0 is 0W for your battery but 10.5 x 500 = 5,250W.

What you call irrelevant, I call the laws of nature and crucial. You're not an electrician or engineer in the electic/electronics field; why do you insist to be beat up by one on his home playing field ?

[Capt Hugh Wilde]

I thank all of you for what you have written. I am still considering both options.

[pbiJim]

So then, to short list it, what I am taking away from this so far is as follows:

Advantages for single cells:
1) Ability to charge individual cells to keep them balanced
2) Ability to remove/replace a single cell if it goes bad
3) Possibly some mechanical/structural advantages, but I am still not exactly sure about the details on that.
4) If you get a single dead cell, you can temporarily remove it from the system & have lots of amps available at a slightly lower voltage which will probably run some, but not all electrical devices on the boat fairly well.

Advantages of 6-volt batteries:
1) Fewer cables to hook up
2) Fewer possible bad connections due to fewer cables
3) Possibly a little less expensive
4) Easier to find in stock at most locations

[Capt Hugh Wilde]

Originally Posted by pbiJim

So then, to short list it, what I am taking away from this so far is as follows:

Advantages for single cells:
1) Ability to charge individual cells to keep them balanced
2) Ability to remove/replace a single cell if it goes bad
3) Possibly some mechanical/structural advantages, but I am still not exactly sure about the details on that.
4) If you get a single dead cell, you can temporarily remove it from the system & have lots of amps available at a slightly lower voltage which will probably run some, but not all electrical devices on the boat fairly well.

Advantages of 6-volt batteries:
1) Fewer cables to hook up
2) Fewer possible bad connections due to fewer cables
3) Possibly a little less expensive
4) Easier to find in stock at most locations

The 6 volt would have more connections due to having to be hooked up in series-parallel. There will be more cables not less.

[careka]

And why not just bring along a 2V cell in back up. does not take much space.
Just give it a puff now and then.

[s/v Jedi]

With single cells, you build your own battery. You can buy single cells in almost any capacity.

When you buy a 12 V battery, you buy it of the capacity you need, i.e. 100Ah. Nobody buys 4 batteries of 25Ah instead and connects these in parallel.

But when it comes to bigger capacities, people suddenly start connecting things in parallel well before it is needed. I can only come up with two reasons and that is to get things cheaper and ignorance.

Buying 900Ah single cells and connect these in series, is the clean and optimum way of doing it. Much less cabling, perfect load balancing, no parasitic effects etc.

[Fuss]

Originally Posted by careka

And why not just bring along a 2V cell in back up. does not take much space.
Just give it a puff now and then.

Give it a puff now and then..

Sounds like a good simple idea, but then you have to store it, maintain it (water) and somehow charge it.

If you started a thread on how to maintain the charge of an extra 2v cell alongside the other 2v cells, it would generate many replies, mostly I think saying not to have a spare.

Imagine the thread... Can I just parallell a spare 2v cell to one of the other 2v cells in my battery bank?... it would generate pages of discussion.

Then typically of boats, because you went to all this trouble, it would then never be needed.

[pbiJim]

Originally Posted by Capt Hugh Wilde

The 6 volt would have more connections due to having to be hooked up in series-parallel. There will be more cables not less.

I think that will depend on how many 6-volt batteries you choose to put in a given bank. I was thinking of a bank with 2 6-volt batteries vs. a bank with 6 2-volt cells. If you go to a bank with more batteries, then the number of cables may change, as you have suggested.

[twinboat]

Buy it dry and carry acid to fill it, if needed. Just kiding, guys

[Capt Hugh Wilde]

Originally Posted by pbiJim

I think that will depend on how many 6-volt batteries you choose to put in a given bank. I was thinking of a bank with 2 6-volt batteries vs. a bank with 6 2-volt cells. If you go to a bank with more batteries, then the number of cables may change, as you have suggested.

I have the space to build a 900 amp hr bank. I can do it with 6 -900 amp hr 2 volt in series or
6 - 300 amp hr 6 volts in series-parallel

The series-parallel set up would require 7 jumpers, 3 to series the 6 volt to 12 volt, and 2 each to tie the positive and negative poles together.

The 2V bank would use 5 jumpers, so 2 less.

[nimblemotors]

Just use two of these 900ah batteries, only 1 jumper...
Trojan 897 Amp-hour 6 Volt Deep Cycle Battery
Surely you can manage 415lb, if you can install a diesel engine, you can install these..

Which batteries would be easier to replace when out cruising ?