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Old 10-02-2015, 23:44   #1
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Location: SF Bay Area
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Choosing batteries and balancing charging

I am evaluating the merits of different batteries for a long distance off-grid cruising. Batteries will rarely reach 100% because it takes much longer for the batteries to accept the last 10% of charge. I am wondering if its a good trade off to buy the 250 AH Trojan 105 RE batteries because they have 25% more life cyles then the T145s? The T105s would give me a 450 AH house bank as opposed to 520AH from the T145s.

Another consideration is that a bigger bank will need more energy to charge them. I only have 360 watts of solar panels so the rest of the charge will have to come from the engine or I may get a wind generator.
A tech at Trpojan told me that I should have 1.5 watts of solar for every AH in my batteries. Not likely to find room for that much solar on a 36.5' boat.

I read Maine Sails artricle on 6v flooded and really appreciate his insights. He saved me from getting AGM Group 31 batteries when I had room for GC2 Trojans. On my last boat I had Trojan 6v, but only used the boat for racing and weekend trips. They never let me down.

Any opinions would be mos welcome! Big shout out to Maine Sail!!
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Old 11-02-2015, 00:53   #2
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Re: Choosing batteries and balancing charging

The Trojan T 145's are 10 lbs heavier, then the T105's they are the same dimensions except for height. The height is measured from the bottom of the bat case to the top of the terminal stud.

But this is not always the measure of the actual plate heights, as noted the 145's are 10lbs by weight more mass in plates, but only less then 1 inch taller. So that means the well at the bottom of the plates on the 145s is less the that the 105's.

The 145's are 260 amp hr, and the 105's are 225 amp hr, both at the 20 hr rate. The 520 you quote is the reserve minutes of the 145's at 25 amp load, the 105's are 447 reserve minutes, at the rated 25 amp load.

T-145 10.30 X 7.11 X 11.90 X 72 lbs

T-105 10.30 X 7.11 X 11.07 X 62 lbs

The 145's are built with more plates, thinner then the 125's that are less plate, but thicker.

The 145's have the lowest internal resistance(pukert factor) of all the Trojans. Trace Engineering did a study of the same some 25 years ago, and the 145's had a Pukert factor of 110-115, the 105's a 125, and the L-16's a 1.30.

So in the end it depends on what the design system is. Operating in a low Pukert load in partial SOC, the 105's are a good fit. Operating high Pukert...ie inverter loads the 145's are a better fit. But the are both dependent on not going below 50% SOC

The Cycle Life is dependent on the charge regime, charge early, and charge fully. And both batteries do better with a bulk charge of 14.8, reduced to 14.6 volts upon reaching absorption voltage.

Operating in a partial state of full charge, results in more plate shedding, which favors the 125's, because they have deeper wells.

Lloyd




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Originally Posted by Onemoreproject View Post
I am evaluating the merits of different batteries for a long distance off-grid cruising. Batteries will rarely reach 100% because it takes much longer for the batteries to accept the last 10% of charge. I am wondering if its a good trade off to buy the 250 AH Trojan 105 RE batteries because they have 25% more life cyles then the T145s? The T105s would give me a 450 AH house bank as opposed to 520AH from the T145s.

Another consideration is that a bigger bank will need more energy to charge them. I only have 360 watts of solar panels so the rest of the charge will have to come from the engine or I may get a wind generator.
A tech at Trpojan told me that I should have 1.5 watts of solar for every AH in my batteries. Not likely to find room for that much solar on a 36.5' boat.

I read Maine Sails artricle on 6v flooded and really appreciate his insights. He saved me from getting AGM Group 31 batteries when I had room for GC2 Trojans. On my last boat I had Trojan 6v, but only used the boat for racing and weekend trips. They never let me down.

Any opinions would be mos welcome! Big shout out to Maine Sail!!
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Old 11-02-2015, 01:04   #3
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Re: Choosing batteries and balancing charging

I just noticed that you said the Trojan RE 125's.

The RE series of the Trojan batteries have a lower specific gravity of electrolyte when fully charged.

This means they suffer less from PSOC, but also have less voltage when the bat temp is lower then 77F. This works good in the Renewable Energy situations, because battery rooms are typically isolated from extreme conditions.

They can also be a good choice in warmer climates, but they will suffer, voltage drop as the temp drops below 77F. So in the Northern climates, in unconditioned battery spaces, you have to de-rate the amp hr, based on the volt/temp of the actual battery operating temps.

Lloyd
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Old 12-02-2015, 21:30   #4
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Re: Choosing batteries and balancing charging

Thanks for all your great information. I am wondering how much of a voltage drop there would be in 35 degree weather? Thats what can be expected in the SF Bay Area and NZ during the winter. In the tropics it would be much warmer.

Also, I noticed that Costco is selling Interstate GC2 batteries. They are 208 AH and rated at 1000 life cycles for just $84.00. At that price I could get 6 and have a 624 AHG house bank for 550.00 including tax. Although I would have to give up and modify storage space for them and charge them too! Discharging them down t0 75% would be 156 AH to replace.
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Old 12-02-2015, 21:54   #5
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Re: Choosing batteries and balancing charging

Of course the amount of amps you have to put into a battery bank every day is mostly related to how many amps you take out of it every day. In my case I keep my electrical requirements small so my recharging requirements are small. If you haven't enough real estate for a large solar array then consider wind (I don't like windmills, but thats my problem) and/or engine charging and/or honda generator charging (my preference).

From my past ten years of electrical experience i've come to the conclusion that I should have the largest bank of golf cart batteries I can carry (6), the largest solar array I can put up (260W), the lowest electrical drain I can live with (but the admiral won't give up the 12v fridge, even though it's by far the biggest draw), and some alternate ways of charging the batteries when the solar panel isn't enough (honda generator with a battery charger, or, worst case, run the engine).
I'm no electrical genius, but I don't think I have to be; just need to know enough to build a system I can live with. And a lot of that knowledge comes from reading about the experience and advice of others coupled with my own personal experience. Even saying 'Peukert' makes me think of 'puke'....
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