[C320-list] FW: Re: Are 6V Batteries Superior To 12V Batteries

Mon Jun 26 04:18:01 PDT 2006

Jeff,

Having just been through the conversion, I agree with much of what you have written, especially the Pro's and Con's.

The golf car batteries currently in the area Sam's Clubs are an Energizer EGC2 made by Johnson Controls, Inc. JCI specs them out at 220 ah (6v) at the 20 hours rate, so in theory, I have 440 ah (+/- depending on discharge rate).

I was unable to find a flooded lead acid 4D at that capacity, since a they all seem to be the combo batteries for starting and must design for a reasonable marine cranking amps (MCA) rating. For example, the Exide Stowaway Marine 4D is 160 ah and the SeaVolt 4D at WM is 120 ah. Since I have an independent starting battery, I felt I did not need to compromise the house bank by using a combo battery. I also have the 2 banks of 6v golf car batteries in parallel, so I am halving the discharge rate for (hopefully) extra life, unlike before when I worried about saving one of the 4D's to be able to start the engine!!!

The way to get more ah from the 4D footprint seems to be to change the technology... WM SeaGel 4D gel at  183ah or WM AGM 4D at 200ah. But these would wind up costing me 3-4x what the golf car batteries cost me. 

Even the Exide Commercial 4D (COM-4D-P) is still a combo battery, however the reserve minutes are 320 instead of the 250 spec'd for the Exide Stowaway Marine 4D, so I suspect it is around 200-210 ah. For someone that wants to maximize the power available from 2 4D wet cell batteries, that would be the way to go, as Chris Burti has discovered.

Just some rainy day thoughts.... 

Regards....

Karl Mielenhausen

2000 C320 Hull#690 "Silver Lining"

New Bern, NC

http://members.cox.net/mielen/

From: Jeffrey Hare [mailto: catalina at thehares.com]

To: C320-List at catalina320.com

Date: Sun, 25 Jun 2006 23:01:02 -0400

Subject: Re: [C320-list] Are 6V Batteries Superior To 12V Batteries

Hi Warren, Putting a pair of 200Ah 6V batteries in series yields roughly 200Ah, not 400ah, since they don't add in this way. They only add when placed in parallel. So regardless of whether you go with 4 golf cart batteries or 2 4Ds, you'll end up with roughly 380-400ah either way. 6V battery pairs in series have their ... Advantages: =========== 1) Weight ~1/2 each 2) Price (maybe, see disadvantages) Disadvantages: ============== 1) Both batteries **must** have the same number of cycles on them, be the identical internal construction and mfgr to use in series. AND YOU MUST REPLACE THEM IN PAIRS or you're just tossing away money since the older battery will fry itself. 2) The Amp Hours available in the weaker battery RULES since they're in series. 3) Doubles the number of terminal connections. Most people rarely clean these terminals and connectors. If you're one of these people, 6V 
systems won't be providing you extended usable AH you expect due to increased resistance. (and it is significant). Now, for the AMP HOUR issue: Remember that the usable Amp hours depends a lot on the condition of every connection, and the rate of draw-down. There's a lot of "smoke and mirrors" in the Amp hour numbers, so don't be fooled there. They can use thinner plates and achieve better numbers at the expense of durability and cycles. Here's a Quiz: :) =================== ASSUME: A 200 Amp Hour (4D 12v battery) or (pair of 6V golfs in series): Question: If you remove 100AH from the battery, how much do you have left? Answer: DEPENDS ENTIRELY on how *fast* you removed that 100 Amp Hours! If you put a 100A load on the battery, it could be completely spent in under 10 or minutes or so. That's less than 60 amp-hours till dead battery. Yet, if you draw the battery down with a 1 amp load, 
you could go way over 200 hours before it's drained, maybe even 300 hours. That'd be 300 amp hours. This is why, if you want to get maximum usable amp hours out of your batteries, PUT THEM IN PARALLEL. It instantly cuts the draw from each battery in half and will give you more usable amp hours out of the battery. The ADDED BONUS here is that the slower you draw down your batteries, the less they're damaged by discharging, so LONGER LIFE. My recommendation is, and has been, Put 4Ds in parallel, add the biggest Automotive starting battery you like (900cca or better), go sailing and let the next owner deal with changing the house batteries.. :) -Jeff -----Original Message----- From: Warren Updike [mailto:wupdike at hotmail.com] Sent: Sunday, June 25, 2006 9:51 PM To: Catalina 320 Mail List Subject: Re: [C320-list] Are 6V Batteries Superior To 12V Batteries I can't disagree with much that's been 
said. However, I've not see the arguement on price and capacity. I don't know why it is but I understand golf cart batteries have about 200 AH capacity. Also, golf cart batteries can be found at Sam's Club, BJ's, and I presume CostCo for quite a bit less than equivalent 12V 4D from the likes of BoatUS. Price of about $60 seems to ring a bell. A number of people have replaced two 4Ds with four golf cart batteries. Total amp hour capacity goes from about 270 to 400+ AH for less money. Unless there is a kickker, that sounds like a good deal. Compare the dimensions of the golf carts vs 4Ds. I understand they are a bit taller, but otherwise fit in the same horizontal space. I chartered a 52' Tarten in BVI and the captain said he has 12 6V golf cart batteries on board because they are much less expensive to buy, weigh less (easier to install/remove,) and have more reserve capacity than equivalent marine deep-cycle 
batteries. Warren & Pattie Updike C320, #62, 1994, "Warr De Mar" Frog Mortar Creek, Middle River Chesapeake Bay

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