12v batteries vs 6v

[Hankthelank]

anybody have any past experience or suggestions? 6v seem to weigh less for the same number of ampere hours. Plus 6v i would think would be easier to install and can fit into small areas.

[sandy daugherty]

I managed to stuff 760 Amphours into by battery box using 6 volt L16s, but they weigh 123 pounds apiece, and are 17" tall. I suspect that the ratio of amphours to weight is linear, so it doesn't really matter much whether you use 12v or 6 volt batteries: buy them by the pound!

[AnchorageGuy]

Been running 6 volt golf cart batteries on both my banks for about 800 amp hours and they take up less room, weigh less and are a whole lot less expensive to replace than the old 8Ds. Been using this set up for about 10 years. We get about 6 to 7 years out of a pair.

[cory_reinking]

Using multiple 12V batteries for a 12V systems means putting the batteries in parallel. Your individual batteries will have different internal resistance even if they are the same type from the same manufacturer from the same batch. So one battery will take more of the change and give more towards your load. These differences will get worse over time as the batteries age. You will get longer life out of your batteries if you can manage to run them only in series. They drawback with a strictly series based bank is that you will loose the entire bank if one battery or cell goes bad. It can also be difficult to get the AH you are looking for in a series bank. I installed 6 - 2V batteries in my boat with 504AH of capacity. They are from Concord and have worked quit well. They are also the exact same form factor as their 6V golf cart batteries.

[Pblais]

I've had both. 6 volt or 12 volt it may come down to weight and size. I would rather lug 4 6 volt batteries than 2 - 12 volt batteries even if the tonnage adds up the same. 4 trips is a little easier on the back. There is not any difference in much of anything only based on the voltage. Chuck, I wouldn't even look at an 8D the idea scares me enough. I had 4D's AGM's last time and was happy though not ecstatic hauling them aboard. I sold the boat before they needed to be removed. I have golf carts now again and while I miss not dealing with water levels they are a necessary evil you deal with regularly or you pay for the error dearly.

The issue of one bank vs two can be the same no matter what you choose. I have a combiner that is normally combined should I see a problem in time I can cut out half the batteries. I had that with the AGM's too. Could always help at some point.

[CaptHead]

I have to agree on the 6 Volt batteries over 12 volts. I have 6 Trojan T-125's and they are over 5 years old now with no problems. I have an 1800 watt inverter that they power when I need to and this combination really lasts a long time. I do charge my batteries a lot different than most however, I don't leave my charger on longer than 3 days and that will me once a month unless I am on anchor and using the house bank.

Yes, I have the 4 stage charger and I read the hype. I just don't leave it on and consequently, use very little water because they don't have a constant charge. I usually get 7 to 8 years from each bank. Next change I am getting 10 Trojans.

[Pelagic]

Originally Posted by cory_reinking

Using multiple 12V batteries for a 12V systems means putting the batteries in parallel. Your individual batteries will have different internal resistance even if they are the same type from the same manufacturer from the same batch. So one battery will take more of the change and give more towards your load. These differences will get worse over time as the batteries age. You will get longer life out of your batteries if you can manage to run them only in series. They drawback with a strictly series based bank is that you will loose the entire bank if one battery or cell goes bad. It can also be difficult to get the AH you are looking for in a series bank. I installed 6 - 2V batteries in my boat with 504AH of capacity. They are from Concord and have worked quit well. They are also the exact same form factor as their 6V golf cart batteries.

I think quite often that space dictates the choice as in my case only 8D would fit nicely in the old space because of height restrictions

I had the option to use a deep area for high 2 volt AGM’s for the large size House Bank (1040Ah @ 24v) but as Corry pointed out, you loose one, you loose them all

I am curious…. if you wire them series/parallel does that help to balance out the individual battery use?

[bstreep]

Hey folks, don't forget about "Ohm's Law". I THINK I'm right here:

2 - Trojan T-125s are 240ah each. When wired in series, for 12V, they NOW only provide 240ah in TOTAL. Right????

[theonecalledtom]

I thought aH's were 1 amp, 1 volt, 1 hour so 1Ah at 12V == 2Ah at 6V. This means a 2 X 6V 240Ah hour batteries in series to get 12V will provide 40hours @ 1 amp draw (the total rating is still 480Ah).

Am I wrong?

[GordMay]

Originally Posted by bstreep

Hey folks, don't forget about "Ohm's Law". I THINK I'm right here:
2 - Trojan T-125s are 240ah each. When wired in series, for 12V, they NOW only provide 240ah in TOTAL. Right????

Originally Posted by theonecalledtom

I thought aH's were 1 amp, 1 volt, 1 hour so 1Ah at 12V == 2Ah at 6V. This means a 2 X 6V 240Ah hour batteries in series to get 12V will provide 40hours @ 1 amp draw (the total rating is still 480Ah).
Am I wrong?

Trojan T-125's are rated 240A/H @ 6V.
When 2 are wired in series, you get 240A/H @ 12V.
Series wiring doubles Voltage, whilst parallel wiring doubles Amp-Hours (capacity).

[Lance]

Hi , Amongst my confusion I am trying to decide on a 12 volt or 24 volt system , and am wondering if I use my preferred 24 volt option how hard is it to produce the reduced 12 volt supply for the particular instruments only running on 12v ? Wiring in a DC to DC reduction is it too inefficient?
Hoping to get 8x3.2volt Lithium Phosphate bank .(light and compact).
I want the 24 volts to run high draw items and to increase efficiency on my inverter etc.
Going onto 12 metre Cat.

Regards Lance

[Sandero]

I don't think Paul's install issues should drive the decision. As unpleasant is it to haul heavy batts around you do it once in 5 or 6 years and perhaps you can get help etc.. or SHOULD get help. I did when I had to change out my 8Ds.

As pointed out the series solution leaves you SOL if one cel fails, but you could have a spare standy to fill in. It would be newer and maybe put the system out of balance, but it is also less expensive than changing out an entire bank.

Depending on the space, consider the following:

AGMs and Gels can be mounted "anywhere" in any orientation so battery box dimensions become less an issue. But you can't be running expensive heavy gauge cable allover the place either.

It is said that when batts work together they should be the same type, capacity and age. So this is a consideration when one cell or batt fails prematurely. I don't know the strategy for preventing or dealing with this except if they are completely separate banks and then they would not influence other banks.

Whatever you do, you should try to acheive a bullet proof system which the proper charging and monitoring regimen. This may include high output alternator(s), smart staged charging, equalization, additional regulated wiring, switches with clean connections and a digital monitor such as Link.

I have used wet, Gels and AGMs and find the later two types less trouble. I found the maintenance regimen for wet cells a pain, and messy. I have upgraded by main system and now have 8D AGMs which seem to be performing OK, but they have not really been put to the test of offshore and full time cruising work, as the batts are seeing solar charging on a mooring 4-5 days a week and weekend use.

I expect to see new battery technology coming in the not to distant future as the energy crisis places more demands for storage of electricity.

This will be evolving.

[Pelagic]

Originally Posted by Lance

Hi , Amongst my confusion I am trying to decide on a 12 volt or 24 volt system , and am wondering if I use my preferred 24 volt option how hard is it to produce the reduced 12 volt supply for the particular instruments only running on 12v ? Wiring in a DC to DC reduction is it too inefficient?
Hoping to get 8x3.2volt Lithium Phosphate bank .(light and compact).
I want the 24 volts to run high draw items and to increase efficiency on my inverter etc.
Going onto 12 metre Cat.

Regards Lance

Hi Lance,
Not a problem using the DC to DC as their efficiency rating is about 93%

All my batteries are 8D 12 volts

I have a 24 volt system for all my house needs (8 x 260AH wired series/parallel to give me 1040Ah)

Separate bank of 2 x 12 volt start batteries (2 x 200Ah wired series for 24v main engine start) that I can emergency parallel with the House bank

1 x 12 volt start battery for Gen w 12 v alternator that also feeds any 12 volt consumers like Nav/com and stereo so it also doubles as a radio battery.

The key is I have a 24v to 12v DC to DC converter that keeps that single 12 volt fully charged at all times when the gen is off......(most of the time)

[Joli]

If you combine two (2) 240 amp 6 volt batteries to make a 12 volt battery the 12 volt system has a 20 amp hour rating of 240 amps not 480 amps.

We like golf cart batteries but do not get as much life as others. Our season is very short and the batteries tend to sit for 8 months per year, not good. I do think the golf industry buys in volumes that many are thousands time the boating industry. The batteries are very refined and very good.

We use both 12 and 24 volt systems, the heavy loads are fed by the 24 volt system made up of (6) 80 volt golf cart batteries and the 12 volt system is fed by (4) volt batteries. We also use a converter to bring down the 24 volt system intot the 12 volt system. Both seem to work well.