6v or 12v what's the diff?

[grewvin1]

I notice some have 6v batteries in series this work better than a couple of 12v? what if any are the advantages?

 

[JustJason]

6V batteries typically have more reserve capacity/amp hours for their physical size than 12V batteries do. That being said, unless your working on a golf cart or this is a sail boat, I wouldn't worry about it. On bigger boats a single 8D is good enough for most people.

 

[bruceb58]

It's because no one makes a 200A hour 12V battery which is why you put 2 6v 100A batteries in series.

 

[thumpar]

I think the CCA would be lower but for accessories the 6v are great. A neighbor of mine uses 2 6v on his RV camp trailer and prefers them over 12v.

 

[HT32BSX115]

It's because no one makes a 200A hour 12V battery which is why you put 2 6v 100A batteries in series.

Or, you could connect two 100 Amp-HR 12v batteries in parallel...............

 

[bruceb58]

Or, you could connect two 100 Amp-HR 12v batteries in parallel...............

Duh...I didn't read the OP's question correctly.

 

[HT32BSX115]

I think the CCA would be lower but for accessories the 6v are great. A neighbor of mine uses 2 6v on his RV camp trailer and prefers them over 12v.

Yeah. CCA is not the "same" as AMP-HR rating......

 

[thumpar]

Yeah. CCA is not the "same" as AMP-HR rating......

I understand that. That comment was just to point out that I would not try to use them as the "starting" battery.

 

[achris]

It's because no one makes a 200A hour 12V battery which is why you put 2 6v 100A batteries in series.

If you put 2 x 6v batteries of the same capacity (in this case 100AHr) in series, you will end up with 12v 100AHr (not 200AHr). If you wanted 12v 200AHr from 6v 100AHr batteries, you'd need 4 of them wired in series-parallel...

Chris......

 

[WrenchHead]

Achris got it right. Two batteries in parallel (like when you use jumper cables) double the reserve but not the volts. In series (a different connection than jumper cables) they double the volts but not the reserve.

 

[bruceb58]

If you put 2 x 6v batteries of the same capacity (in this case 100AHr) in series, you will end up with 12v 100AHr (not 200AHr). If you wanted 12v 200AHr from 6v 100AHr batteries, you'd need 4 of them wired in series-parallel...

Chris......

Yep...you are correct. Not thinking today.

 

[fishrdan]

Supposedly (old wives tale?), 2- 6V batteries last longer than 2-12V batteries of similar capacities. 2x6V-200amp vs 2x12V-100 amp. Though, I'm not sure if this is available power or battery service life... Doesn't make sense to me, unless the 6V batteries are of better construction and it's service life...

2x12V, pro = 1 dead battery will still leave the 12V bank operational, con = the dead battery will eventually kill the other battery.
2x6V, pro = 1 dead battery won't kill the other, con = 1 dead battery will make the 12V bank inoperable.

It's because no one makes a 200A hour 12V battery...

An 8D battery is around 225 AH... Though, I wouldn't want to be lugging a 135# battery in-out of the boat (anymore).

I had one in my boat long ago, freebie from one of my friends.

 

[bruceb58]

The Trojan t-105 6vs are around 225AH depending on the draw current. The equivalent 12V is around 105 for a 27TMH. The weight difference between those 2 batteries is within a pound.

You go to any RV forum and there are many debates about doing 2 12V in parallel vs 2 6V in series. Supposedly, the 6V batteries have thicker plates especially at the terminals so people swear they last longer because of that.

http://www.trojanbattery.com/pdf/TRJN0111_ProdSpecGuide.pdf

 

[H20Rat]

Supposedly (old wives tale?), 2- 6V batteries last longer than 2-12V batteries of similar capacities. 2x6V-200amp vs 2x12V-100 amp. Though, I'm not sure if this is available power or battery service life... Doesn't make sense to me, unless the 6V batteries are of better construction and it's service life...
2x12V, pro = 1 dead battery will still leave the 12V bank operational, con = the dead battery will eventually kill the other battery.

Fewer cells in the 6v batteries. End result is better construction & heavier plates. Also, depending on your failure state, you can have a 12v battery short out. That will kill the other 12v battery relatively quickly.

 

[Howard Sterndrive]

easier to lift two 6V in and out I suppose. Other than that, just disadvantages in my opinion, trying to strap 2 batteries down in boxes and more external connections to corrode.

 

[fishrdan]

Also, depending on your failure state, you can have a 12v battery short out. That will kill the other 12v battery relatively quickly.

Correct, and this will most likely happen at the most inopportune time, when the boat is being stored for awhile and there is enough time for the bad battery to ruin the good battery.... I've had this happen before, but now have a battery switch separating the 2 parallel batteries so they are not paralleled during storage.

 

[K-2]

Try a couple Trojan T-105's for house power and you'll never go back to 12V except for starting.