12volt or 6 volt

[philip van praag]

Originally Posted by philip van praag

4. Do not fully discharge flooded batteries (80% or more). This will damage (or kill) the battery.

5. Many experts recommend operating batteries only between the 50% to 85% of full charge range. A periodic equalization charge is a must when using this practice.

taken from the link you provided

[DeepFrz]

Philip, the document states that 80% discharge is the "maximum", not to be exceeded discharge. It is not the normal operating discharge level. The document states that the normal operating discharge is 50% or less.

What is it that I am missing here?

[philip van praag]

Originally Posted by DeepFrz

Philip, the document states that 80% discharge is the "maximum", not to be exceeded discharge. It is not the normal operating discharge level. The document states that the normal operating discharge is 50% or less.

What is it that I am missing here?

you are not missing much only that most people work on 50%
with trogens you can go to 80% yes at 50% they will last longer but if its a trade of with weight to power, and price and life are not the key factors there are other ways to look at it
4x6v 400amp =1600amp 50% usable =800amp 10 year life
4x6v 400amp=1600amp 80% usable =1280amp 5year life
which do you chose?

[DeepFrz]

Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor.

Deep Cycle Battery FAQ

[IMG]file:///C:/DOCUME%7E1/Phil/LOCALS%7E1/Temp/moz-screenshot.jpg[/IMG]

[philip van praag]

Originally Posted by DeepFrz

Deep Cycle Battery FAQ

[IMG]file:///C:/DOCUME%7E1/Phil/LOCALS%7E1/Temp/moz-screenshot.jpg[/IMG]

your graph backs my maths so is a personall choce
if you want the amps but dont have space or weight capasity this is a solution its not without cost but that was not the point

[Starbuck]

Originally Posted by peter@hervey-ba

I was thinking of upgrading to 4 x 6 volt Trojan L16H (420a/h @20a/h rate) As I understand things, this would give me a usable 402amp/hrs.

Cheers. Peter

Peter, I think your math is a bit off.

The 6-volt T-105 is rated a 225 amp-hours at the comparing-apples-to-apples 20-hour drain rate. But when you connect two of them in series the voltage doubles while the amp-hours remain the same. Therefore:

Two 6v T-105s connected in series yields the same 225 amp-hours, but now @ 12v.
A second set connected in series yields an additional 225 @ 12v.
(Notice the voltage doubled, but not the amps)

You just used those 4 T-105s to create two 12-v batteries.

Now when you connect those two 12v batteries together, this time in parallel instead of in series, the amps will double while the voltage remains the same.

The yield is 450 amp-hours @ 12v in one large house bank:
225 a-h @ 12v (1st pair of T105s) combined w/ 225 a-h @ 12v (2nd pair of T-105s) in parallel = 450 a-h @ 12v.

Assuming you limit the discharge of this arrangement to 50%, you get 225 a-h of usable 12v power between charging cycles.

For context: please note that phillip's quote about 80% discharge is Trojan's warning about preventing damage to the batteries, and it's true as far as it goes; but, it's also obvious by looking at the chart that economically, the 50% discharge depth is the best compromise point between number of average charge-discharge cycles (1000) the battery will deliver over its life, and the usable amp-hours you can extract from each cycle.

And yes, these type of batteries are favored over other arrangements because "better" is derived from the economic/practicality/availability benefits they offer, not because "better" means they're better at running your onboard systems.

Fair Winds,
Jeff

[44'cruisingcat]

Everything else being equal, total $, amp/hours etc, I'd go with the 6 volt batteries. I've had individual cells fail a couple of times - if it happens to a 12 volt battery you have to replace the entire 6 cells, if it happens with a 6 volt you only have to replace 3 cells.

[Pblais]

We use 4 T-105's and we had them on the first boat too. Using a 50% rule you won't get 10 years. You could get 6 to 7 years, but it depends on how many cycles you use and if you fail to maintain fluids and if you over charge them and the other things batteries don't like. They were very popular when they were priced a whole lot less than now. I would prefer an AGM bank but from a space perspective I can't fit 2 - 4D batteries and my charging gear can't do a smart charge AGM profile. In that context using AGM's would be a poor choice for me.

A bank of 4 Trojans is a good size to work a fridge with a crew of two. You can recharge it in a reasonable time too. The bigger the bank the more it takes to recharge. Reduction of power usage allows this to work well with combined wind and / or solar.

[Starbuck]

Sorry, Peter: so much of this thread is about the Trojan T-105, I used it in my earlier post, though now I see you were considering the L16H. The formulas remain the same, with slightly different input.

You'll have 420 a-h @ 12v.

[Pblais]

if it happens with a 6 volt you only have to replace 3 cells.

That it true to a point. You can't use just one 6 volt battery so you have to series 2 at a time. At that point one bad cell may not show up easily unless the fluid level reveals it early. If it is a shorted cell it won't be obvious. You then have a new 6 volt added to an old one that used to be paralleled to a bad one. The dissimilar nature of batteries based on age alone is not a good condition. To outward appearances by your charging regulator it appears only as one battery. One bad cell tends to overcharge all the others. One dead cell drops the bank voltage 2 volts and that will signal a high demand for charging. Unless you can operate totally independent banks you can't isolate different batteries either by type or age. The cost of total isolation is not insignificant.

If you look at 2 - 6 volt golf carts as a better than average sized group 4D 12 volt the price difference is not that great any more. I sure would not want to haul 4D batteries on and off the boat though. When you add up the cost of proper cables to parallel them it also rises the total cost. I do use them myself but the cost factor is not as great as it used to be. The T-105's used to cost about $60 and so were really a great deal for a 225 ah battery some years back. Price one today and they may still have a slight advantge but not a huge one.

[bobfnbw]

True to a point but.....

All batteries used to cost a whole lot less, and now cost more. I don't think that T105's cost more than they sued to compared to similar batteries. They all went up with the price of lead.

I did a very carefull and detailed analysis recently of battery types for my situation and still consider the T105s' to be the BEST, when you consider price to amp hour rating. They will last around 5-6 years if taken care of properly. They will not like being discharged to 80% more than occasionaly and it WILL decrease the overall life expectancy.
I really don't get the idea that AGM's are a better battery. EVERYTHING I have read about them to me points to problems in a deep cycle useage. If maintaince free and no off gassing is what you want, then Gell cells are better for that. AGMS are good for the occasional sailor, but not a cruiser who cycles his/her batteries often.
And price to amp hour wise, they are 2-3 times more expensive and from what I have read from people that used them, will not give you the cycles a wet cell or gell cell will.
For my money, even with the extra cabling, the hydrocaps or water misers, the Trojan T105 is the best battery for the money available.
If money was not a issue for me, then a ROLLS Surrett battery, wet cell, would be my choice, but I would Pay some one to install them. Cause my back is not worth the possibility of injury.
And if designing a boat from the ground up, then I would go, like the dashews, with large traction batteries built for locomotives, or forklifts, and put them low in the bilge, and they would be considered part of the ballest, and at over 1000 lbs, last for thousands of cycles, as deep as you would want to take them. But like anything else, you have to take care of them.

Oh and remember, using the 50% rule, a 220AH battery will only give you ~90-100 AH of usable power. Cause you will most likely cycle them between 50-85%. That last 15 % will be hard to justify, unless you have a lot of wind and solar, and your needs are few. But as you go up in power useage, it will be harder to fully charge them. So a bank of 6 T105's will give a cruising boat that uses 150ah/day about 2 days before needing to recharge, unless you have solar and/or wind. Then you can go longer.

I guess it just depends on what your focus is. A boat that stays marina bound a lot and powers a lot, go with agm's or gell cells.
A cruiser, go with deep cycle heavy lead acid batteries, installed properly with good venting and with good access so they can be properly cared for.
There will always be many opinions about this. It just depends what your focus is.

Cheers,
Bob

[Pblais]

The AGM advantage is the lower internal Resistance allows a faster charging profile. It then takes less engine hours to reload the battery. That means the indirect cost of running the engine is lower and converts to lower costs. It's not easy to really add up all the costs with battery usage. If you can take actual costs of production out of the formula you can cook the numbers to make anything look better.

What I do know is if you drop AGM batteries into a system without modifying how you charge them you will have poor results. You can abuse any battery system and blame the battery.

[camaraderie]

Bob...I disagree with your AGM analysis completely. AGM's ONLY are worthwhile economically if you are on the hook and charging and recharging several times a week.
The fuel savings in recharging and lower engine/generator maintenance costs offsets the additional costs of the batteries. In no other circumstance do they make economic sense...though they may be preferred for many non-economic reasons.
As fuel prices rise...their economics make even more sense.
VonWentzel has a speadsheet that lets you compare the relative costs of any batteries over their lifetime based on you own boat and own system and usage pattern. You can read about the model and download it here:
Battery Cost Model Inputs and Outputs: Gel, AGM, Flooded
********
Celestial...the "American" brand you refer to is simply rebranded East Penn batteries and are the same as Dekas or West Marines. Good batteries...but not "the best". The advantage vs. the WestMarine batteries is a considerably lower price. Stateside...Deka's are more easily found and provide the same cost benefits.
******

Finally...good quality wet cell OR AGM Batteries can BOTH be easily ruined even in systems that are set up properly. Just don't bring AGM's back to 100% on a charge cycle at least once every couple of weeks. Just leave your flooded's on full time charge at the dock and never equalize them and check the water once a year!
AGM's have the advantage of needed minimal maintenance once the system is set up properly but they are less tolerant of an improper charging regimen. Batteries typically don't die...they are murdered.

[Starbuck]

Originally Posted by bobfnbw

Oh and remember, using the 50% rule, a 220AH battery will only give you ~90-100 AH of usable power. Cause you will most likely cycle them between 50-85%. That last 15 % will be hard to justify, unless you have a lot of wind and solar, and your needs are few.

I forgot to include that last consideration, so my choice of the word usable was premature: of course Bob is right.