Why should I use 4 @ 6v GC batt's?

[degreeoff]

Hello all,

I have been going over this for a bit on my 1985 Cat 30 thats going through a total refit. Is there a reason that I who will use a 12v fridge, perhaps a 6500 btu air unit and lights (hopefully for at least 1 night a week) should go with 4 6v batt's VS 3 12v of simalar amp hours? I will have a dedicated start battery too.

I have looked around and searched but found no real answer to this question. I also plan on a alt upgrade to 90 amp VS 55, a 60 watt or more solar panel and of course a shore power charger. I know I am no purist here but I do like comfort while out at sea.

Thanks

Josh

[tommays]

You can get a better value with the 6 volt batterys AND there must be a reason they still build so many machines like floor scrubers ect powered this way

[erps]

A consideration for some folks is that it's a lot easier to handle two six volt batteries than one 12 volt battery with similar amp capacity. We had an 8D battery in a previous boat and it was a bugger to move around.

[btrayfors]

Josh,

If you're thinking about running the A/C from your four golf-cart batteries (total 450AH @ 12V), you are unlikely to be successful doing that.

For example, the Mermaid M6 draws 6.3 amps AC when cooling. Add at least another amp for the seawater pump, for a total of 7.3A @ 120VAC. That's the equivalent of 69.5 amps @ 12.6VDC plus the inverter losses of at least 10% or a minimum of 76 amps.

If you run your A/C overnite for only the 8 hours you sleep, that's 8 x 76 = 608 AH. A 450AH battery bank only has a usable capacity (at 50%) of 225AH, or about one-third the power you'd need.

The statement on Mermaid's website about running their M6 with a 450AH battery IMHO is both ambiguous (total capacity or actual draw?) and misleading.

Bottom line: you need A LOT of battery capacity to run an A/C, even a small one. In general, it's not practical.

Bill

[mitiempo]

Josh
The 6 volt golf cart batteries are the best value in a battery and more durable than most. With 4 you will also be getting a larger bank than with 3 12 volt batteries unless they're quite massive.. Trojan T105 is 225 AH so this way you will get a 450 AH bank. They are the highest life cycle battery Trojan makes in flooded type by a large margin. And they're easy to handle as well as to find a place for. I agree the air conditioner makes no sense except at the dock.
Make sure you install a good 3 stage external regulator for the new alternator - or for that matter if you currently don't have one you're hardly using your current alternator to capaciity. With an internal reg an alternator is really designed for a start battery and output drops off quickly. With a 3 stage external reg this won't happen. Good time to add an ACR or Echocharge to take care of the start battery and get the charge wiring direct to the new bank and not through the battery switch as well. Hope this helps.

[degreeoff]

Ok so far so good alot of good info. Thanks!

Now here I have 4 6v's and a small 12v for starting, what pieces do I need other than batteries?

ACR ? (Ummm I no not what this is) Switches? External reg? (another one or a replacement for what comes on the alt) where would I find these and about how many bones will they set me back? If I am missing anything let me know I want to do this once for the next 5-6 years when I will sell her and go bigger....;-)

[night0wl]

Not completely on topic, but anyone know the best place currently to score value priced Trojan T-105's online right now?

[erps]

Originally Posted by degreeoff

Ok so far so good alot of good info. Thanks!

Now here I have 4 6v's and a small 12v for starting, what pieces do I need other than batteries?

ACR ? (Ummm I no not what this is) Switches? External reg? (another one or a replacement for what comes on the alt) where would I find these and about how many bones will they set me back? If I am missing anything let me know I want to do this once for the next 5-6 years when I will sell her and go bigger....;-)

Typically, your alternator should be hooked to your house bank. To charge your starting battery, some folks turn the battery switch to "both or all" to charge it up, but you run the risk of forgetting to switch back to your house bank and depeleting your start battery while on the hook. For that reason, other folks charge their start battery through an echocharger or some sort of a battery isolator that combines the two banks when there is a charge present, but otherwise keeps them separate.

If your alternator is internally regulated, it probably has a cheap regulator on it designed to charge starting batteries. One of the best upgrades I did to a previous boat was to install a 100 amp externally regulated alternator and a three stage regulator. Balmar is a popular choice for external regulators and they sell alternators too, but I think they are over priced.

[mitiempo]

Josh
An ACR (automatic charging relay) is a device installed between your house bank and start battery. It will open when a charging current is present (from alternator, shorepower or other source) and pass charge on to the start battery. When there is no charging current it will close and the batteries will be isolated again.
The internal regulator in an alternator is not designed to charge a deep cycle bank but a start battery. A proper external regulator will keep the alternator output high for bulk charge when the batteries are down a ways, reduce the current for acceptance and float for the last 15% of charge just like a good shorepower charger. I think your 55 amp alternator with a good 3 stage regulator is a better purchase than a larger alternator - unless you also get the external reg for the larger alternator.
All charge should go to the house bank (the 4 6 volts) - the ACR takes care of start battery automatically. Depending on the age of your Catalina the alternator output may go through an ammeter on the panel. It should be wired direct to the house bank with a good size wire. If this is so replace the old ammeter with a voltmeter. It will tell you the same thing - that the alternator is charging.
You only need a one bank charger with this system so this may save some money. I like Xantrex but you'll get some recommendations for Iota as well and they are also a good choice.
You might look at a good battery monitor as well so you know where you stand.
Below are some choices. The blue Seas ACR is 80.85, the Victron monitor is 195.50 and the external reg is 311, all at Jamestown Distributors.

[mitiempo]

Josh
The best place for wire and battery cables (custom made $1.00 per lug for labor) is Genuinedealz > Marine Wire, Boat Wire, Boat Cable, Marine Grade