Need more juice for stereo???

No, i couldnt leave the topic alone either.
Cost vs. amp hours is at issue too. A 12 Volt Optima Blue Top runs about $150 and is rated 55 AH, 2 would be $300 and 110AH/12volt. A six volt 200 AH golf cart batt. is about $190 so 2 would be $380 but you get 12 volts/200 AH. Thats almost twice as long as the Blue Top Optima. So run the stereo on the golf cart batt and keep a good 12 volt w/ cca to start and a combiner for trouble free charging.
Of course you will need a larger boat to hold all those heavy batteries.

     OK, sorry I had to butt in again. For SURE, batteries added in series add the voltage and not the current. Say you have 2 6V 100amp hour batteries hooked in series. You would get 12V at 100 amp hours of capacity. 2 12V 50 amp hour batteries in parallel would give you 12V at 100 amp hours. If you look at size of a 6V 100amp hour battery, and a 12V 50 amp hour battery they are usually identical. 12V at 50 amp hours is the same power as 6V at 100 amp hours. Power here is referred to as watts. Adding 2 6V 100 amp hour batteries in series gives you twice the power since doubling the voltage. You cant double the current as you would be getting 4 times the power. This I am 100% SURE of, and wouldnt say so if I wasnt.

    Now where I am not 100% sure, is why they still hook 2 6v batts in series instead of 2 12V in parallel. This I think is due to the fact that golf carts and starting large diesels require tons of current. 6 volt batteries will offer less of a voltage drop internally due to the larger cells. 12V batteries have twice as many cells as a 6 volt in the same physical size causing the cells to be smalller and not able to handle the large current as well.

    Hope you all had a great 4th!! Still had fireworks going on the lake tonight!!

                                   Jeff...

I guess you are right about golf carts, however in the arena of many toys added to cars, buses, trucks it doesn't fly. If you go down to a West Marine today they sell 6 volt batteries to be used in series with boats with that the demand for power. If you charge batteries in parallel thru a switch one never gets charged up if you don't change over time and again, or without the switch.
I have set up 12 -24 volts series on diesel applications that start on 24 and switch back to 12 still to this day. As I said before cheap is cheap it won't be long it will catch up and go around. The older boats out there were never set up for all today toy's, I have two.
I thought this was a learning forum rather than I got one better than you, my mistake.

For what its worth...
The old school method of putting two 6volts in series actually came about because not so many years ago the only decent deep cycle batterys to be found were 6 volt batterys used in golf carts, so if you needed a reliable 12 Volt set up you put them in series. Nowadays you can get 12 volt deep cycles.. and two of them in parallel is a much better solution precisely because if one goes bad your still in business. Conventional wisdom has not necessarily caught up to the technology in some circles...

J_I_H:

Argh! Are we speaking on the same subject or using the same terms? Let's try it this way: Take two identical 12 volt batteries. Now, put a theoretical load of maximum voltage on one of the batteries so that it will be exhausted in exactly one hour. Now wire the two batteries in series: maximum load, at 24 volts, will exhaust the batteries in one hour. Now wire the two batteries in parallel: maximum load, at 12 volts, will exhaust the batteries in two hours.

I agree with: "I see no gain of having two 500 amphr 6 volt...."

PS. Your diagram (parallel) looks good to me.

However, I see no gain of having two 500 amp/hr 6 volt batteries over one 1000 amp/hr 12 volt battery.

I just don't know why anyone would want to series 6 volt batteries to increase capacity. Why not parallel two 12 volt batteries. This is what is normally done. In fact, with two parallel 12 volt batteries a disconnect switch can be added to disconnect your engine starting battery from your stereo when setting at the dock so you don't discharge your "main" battery. By doing this you can use a smaller 12 volt "motorcycle" type battery for your second "stereo power" battery. Switch in the smaller battery while running to recharge it.

The batteries where all in series and it was not a compination of paralell and series, they where even stacked on top of each other and ever single one had their own heating element as well as several sensors within the craddle that they where mounted in.

79...

Not sure where you are coming from on this, but I guess I can clarify my position and say that if you have amultiple battery bank (more than two) then you can indeed increase voltage AND capacity by doing a combination of wiring the batteries (or cells) in series and in parallel. Not on the same cell/battery, but some in series and some in parallel.

Just to make sure I am not all wet on this, I did some looking on the internet (and you know everything you read is accurate) to support my argument. Tell me again why I chimed in?

I'll weigh in (don't know why...guess just bored today). I agree with GottaSki. Batteries wired in series will increase voltage, but capacity remains the same.

When the batteries are wired in parallel, you are doubling the capacity but the voltage remains the same. You cannot do both... it's an either or kind of thing.

Two 6 volt batteries in parallel will give you 6 volts and 500 amps. Two 6 volt batteries in series will give you 12 volts and 1000 amps. End of quote.

not yet it's sitting on a craddle in the barn right now.

The voltage regulator could be going out in the alternator, you might want to have it tested.

the guage of wire will depend upon the amp, I use #8 on mine. Most newer amps have a fuse built into them so there is no need for a inline fuse.