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Old 09-01-2007, 16:40   #1
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6V Trojan VS 8D Batteries

I think that my 8D batts are dead and unrecoveable. And I am looking to replace them with 6 Volt Trojan golf cart batts.

First, the golf cart batts are rated at185-225 AHR depending on the discharge rate according to the mfgs literature. So if I gang these together in series/parallel to get 12V the actual amp hours avail is the sum of the individual batt am/hr ratings divided by 2? Correct?

Ie. if I have 6 6V batts @ 215 A/HR ea = 1290 A/hr divided by 2 = 645 A/hr

So replacing by 8D's which are rated at 240 A/Hr ea for a total of 480 would give me considerable extra capacity.

Are there any other considerations I should take to mind about this change-over?

Alan Perry
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Old 09-01-2007, 17:07   #2
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Alan,

Trojan T-105 golf-cart batteries are rated at 225AH @ 20-hour discharge rate. Each one, as you know, is 6 volts (3 cells).

If you take 2 of these batteries and connect them in series (positive to negative), you get 225AH @ 12 volts.

Four T-105s connected in series/parallel would give you 450AH @ 12 volts.

Six T-105s connected in series/parallel would give you 675AH @ 12 volts.

Trojan also makes at least two other sizes, which are taller and have larger AH ratings. These might be appropriate, if you have the height clearance.

One caution: when you chain these batteries together, be sure to use REALLY LARGE and REALLY SHORT battery cables. I recommend size 1/0 or larger cable. If you orient the batteries correctly --either side-by-side or end-to-end -- each 12-volt "unit" can be constructed using a connecting battery cable which is about 6" long.

Make absolutely sure that connections are clean and tight.

Bill
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Old 09-01-2007, 18:39   #3
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the 6 volt golf cart batteries are taller than the 8D 12 volt. make sure they fit in your boat.
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Old 10-01-2007, 03:40   #4
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Battery Banks (series, parallel, or series/parallel) should always be configured so that Load Distribution Cables are connected to different batteries at opposite ends of the combined bank.

When connecting the batteries in parallel, the positive poles are connected to each other, as are the negative poles. The voltage does not change and the capacity (Ah) will be the sum of the connected batteries.

When connecting the batteries in series, the positive pole of one battery is connected to the negative pole of another battery. The voltage will be the sum of the connected batteries voltage and the capacity (Ah) will remain the same.

In the Parallel-Series connection, both types of connections are used. The parallel connection will raise the capacity (Ah) while the series connection will raise the voltage.
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Old 10-01-2007, 09:12   #5
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Hello again, Alan. Hope the prep is going well and all 'personal systems' are go, too.

Your math is correct as Bill and others have shown. I'd encourage you to start with T-145 batteries and work 'down' (T-125's and finally T-105's) as you may find you can load 4 x T-145 batteries aboard - perhaps modestly modifying your battery boxes if necessary - and enjoy multiple benefits: a bit more capacity than what your 8D's theoretically provided, a smaller foot print, less weight, and perhaps less cost.

I say 'perhaps less cost' (for 4 x 145's vs. 6 x T-105's) because I've found it very easy to locate T-105's at bargain prices (usually at an auto-electric shop where starters and alternators are rebuilt; they work with a different 'clientel' than chandlers and boat yards). E.g. just the other day I got a quote for T-145's from a local outfitter and he wanted ~$160 per T-145. A Tampa auto-electric vendor last sold me T-105's for $60 each in 2003, so even with price hikes the T-105 amps are going to be far more cost effective. Still...I'd suggest you run the numbers if 4 x T-145's look like they will do the job. Smaller footprint and less weight are still worth benefits.

When do you shove off? Being up your way, I assume the answer is 'summer'...

Jack
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Old 10-01-2007, 11:01   #6
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Quote:
I say 'perhaps less cost' (for 4 x 145's vs. 6 x T-105's) because I've found it very easy to locate T-105's at bargain prices
That's not so true any more. With the lead prices up these batteries are selling for about 50% more than they used to only a few years ago. While I think they are a good value they are not cheap. last fall I got a good deal at $96 per T105.

I would agree that a good measure of the compartment would help decide what can fit. Getting 4 really would be better than 6. For us 4 - T105's makes a nice size house bank. If you don't really need all the extra power it's better not to add the batteries. It just makes it harder to fully recharge the bank. Under charged banks are a bad thing and getting back the last 10% is a lot more time at lower charging amps.
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Old 10-01-2007, 11:58   #7
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Paul,

I paid $116 each for 4-105s last summer in RI, $96 was a bargin.
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Old 10-01-2007, 15:42   #8
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Thanks for all the input. My son works at a place that sells them and so I will get them for his employee price which is considerably cheaper than those prices mentioned. Cost and connection were low on my list of worries. What I was trying to get at and probably didn't make clear, I was wondering if there were any "hidden" issues in using these guys. Things that may not be apparent, like differing charging rates, lifespan, dependability and susceptability to vibration etc.

From what I've read on other posts about them people seem to be pretty happy. Any naysayers out there?

I have talked to the MFG and have their side and suggestions and to their credit the warranty is not affected by being used in a boat.

Alan
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Old 10-01-2007, 16:10   #9
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Alan,

In fact, they are marketed for marine use!

I bought 8 new T-105's last year also. Shopped around, and found that prices had markedly increased. I've been using these for 15 years, and had been used to paying $60-80 each. No more, unfortunately.

Only downside is the need to watch their fluid levels closely. Depending on your usage pattern, either Hydrocaps or WaterMiser caps are a good investment to greatly reduce the loss of water, and make maintenance much easier.

Hydrocaps are great, but have to be removed when equalizing (I can't use them because I have a system which does automatic periodic equalizing, even when I'm not around to remove the Hydrocaps). I just ordered a bunch of WaterMiser caps which are a bit cheaper and which do not have to be removed when equalizing.

Bill
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Old 10-01-2007, 16:24   #10
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As far as negative aspects. There are none specific to these flood batteries over others. They are a well made product. Clearly a first choice of most folks on the water using flood deep cycle batteries.

My last boat I switched from T105's to group 4 AGM's and I really like that setup better. It's less hassle and they recharge quicker but you have to adjust the charging gear for it. You can store them upside down backwards you name it. They cost a bit more but the lower internal Resistance has some payback too.

The new boat does not have the room for anything else and the charging gear was not set up to adjust for AGM's so I stuck with T105's instead of replacing regulators and chargers plus find another location for the batteries. They do need to be secured and don't like tipping, and need proper venting! All flood batteries need that.
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Old 27-03-2007, 12:33   #11
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T-105's $85/each from Safe Start* Home Page

They distribute down in South Florida.

Cheers,
Aaron N.
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