Trojan T-105 vs. Lifeline

[Oceansailor]

I have app. 200A alternator capacity. I can’t remember once when the Lifelines accepted 200A. This on 880Ah bank. The Balmar regulator is set at 14.4 V and that is also the voltage at the terminals.

As my new batteries will be flooded batteries Trojans T-105 (same capacity as the Lifeline). I will increase voltage to 14.9 V.

Will I experience a significant change in time charging from 50 % SOC to 80% SOC?

I’m hooping that the voltage difference will make up for the increase in resistance.

Is there a significant difference going from 80% SOC to 100% between Lifline AGM and Trojan T-105.

[sailorboy1]

I never seen my 440AH T105 bank accept more than about 73 amps at when they are at about 80% SOC (never seen my batteries less than 75%). Acceptance drops to about 60amps by the time the batteries get to 85% SOC. I have my absorption set to 14.8V.

[a64pilot]

Your batteries were either sulphated or more likely your alternator wasn’t putting out 200 amps.
When at 50% SOC my 660 AH Lifeline bank will accept 185 amps for fifteen min or so. 185 amps is what my two shorepower chargers can make. My 165 amp alternator can make about 90 or so and stay within the temp parameters I have it set to. Actually subtract about 10 to 15 amps for house loads.

If I start my charge at about 75% SOC or so they never get close to 185 amps.

The higher acceptance rate for AGM batteries really don’t matter much, especially when you stack that against they are less tolerant to short cycling. So with AGM batteries, you really need to charge them longer than normal flooded batteries, just the opposite of what you would think with the higher acceptance rate.

[rgleason]

The higher acceptance rate for AGM batteries really don’t matter much, especially when you stack that against they are less tolerant to short cycling. So with AGM batteries, you really need to charge them longer than normal flooded batteries, just the opposite of what you would think with the higher acceptance rate.

"AGM...less tolerant to short cycling" ..."so charge them longer than normal flooded"

So you have to charge them to a higher SOC? Like 90%C?

How do you know they are less tolerant to short cycling? Literature? Experience?

So I am guessing you would be less likely to use AGM when the battery bank is undersized for the loads? Kind of counter to the advantage of higher acceptance rate 40%.

I was thinking it would be very nice to have some way to measure "cycling" and to see on a graph the battery SOC across time with use data such as number of discharges below 30C 50C etc and number of charges above 80C, 90C 95C etc. Most recent charge= 96C etc

[Oceansailor]

Originally Posted by a64pilot

Your batteries were either sulphated or more likely your alternator wasn’t putting out 200 amps.
When at 50% SOC my 660 AH Lifeline bank will accept 185 amps for fifteen min or so. 185 amps is what my two shorepower chargers can make. My 165 amp alternator can make about 90 or so and stay within the temp parameters I have it set to. Actually subtract about 10 to 15 amps for house loads.

If I start my charge at about 75% SOC or so they never get close to 185 amps.

The higher acceptance rate for AGM batteries really don’t matter much, especially when you stack that against they are less tolerant to short cycling. So with AGM batteries, you really need to charge them longer than normal flooded batteries, just the opposite of what you would think with the higher acceptance rate.

Today my batteries are sulphated. I see maximum 140A go in and it tapers down to under 100 whitin 20 minutes.

This is with watermaker 40A + other consumers 20A running. This is why I know the alternators are putting out 200A. Charge do not increase if a turn off watermaker.

The problem I have is that I did not really do any real testing when the batteries was new. It is when batteries starts to get old you start to worry.

Another explanation might be that I was not at 50 % SOC very often. That normally only happens on passages.

But back to the original question. I understand that you think there will not be a significant difference between AGM and flooded as the charging capacity is
Limit to 200A?

The other question is with regards to the last 20 % that will only take place on sunny days with solar. Will there be a difference in time to reach 100% SOC?

[Locquatious]

The amp rating of alternators is often the max amps, at a certain high rpm, when the alternator is still cool, and when charging into a 12V battery. If the battery voltage is higher than 12V, the alternator is hot, and the rpms are lower than max amp production, the alternator output will be lower.
Often as the alternator heats up, the stator windings and the field windings will increase in resistance. When the field current drops, due to the greater resistance, the alternator output will drop. Some alternators have a temperature limiter in the voltage regulator that cuts or modulates the field current as the alternator approaches an overheat condition.
Alternator amp output is not a good measure. First because alt manufacturers publish the 12V rating just to look good. But you should avoid letting your batteries get down to 12V and when they are charging the voltage quickly goes above 12V. The alternator is better characterized by power output P=Amps * Volts. So if the alternator can put out 200A at 12V, it would be able to put out 12/14.8= 0.82 or 0.82*200A= 164A at 14.8V.
If you are exceeding the acceptance rate of a battery, the voltage rises quickly to the regulator voltage. Typically the regulator begins modulating the field current and the alternator average amperage will automatically be cut down to the acceptance rate of the battery system.

[Oceansailor]

Thanks for the explanation. It is an important point to understand that the alternators will only produce rated output for a short period of time. My alternators alternators are able to put out 200A even when they are hot.

Let’s discuss the original question. How much difference it is charging a large AGM bank vs a flooded bank instead? And will there be any significant difference for the last 20 % up to 100 % SOC? The last question is important as many cruisers use solar for top charging.

[a64pilot]

Originally Posted by rgleason

"AGM...less tolerant to short cycling" ..."so charge them longer than normal flooded"

So you have to charge them to a higher SOC? Like 90%C?

How do you know they are less tolerant to short cycling? Literature? Experience?

So I am guessing you would be less likely to use AGM when the battery bank is undersized for the loads? Kind of counter to the advantage of higher acceptance rate 40%.

I was thinking it would be very nice to have some way to measure "cycling" and to see on a graph the battery SOC across time with use data such as number of discharges below 30C 50C etc and number of charges above 80C, 90C 95C etc. Most recent charge= 96C etc

No, you need to charge them to a higher SOC like 100% as often as you can, and probably equalize monthly. If you can’t often get to a real true 100% SOC you may be disappointed with AGM.

Justin Godber is my source he is I guess the GM at Concorde / Lifeline.
Also read as much as you can that Maine Sail has on his website on batteries, he seems to specialize in Lifeline, I think a lot of that may be due their excellent manual and literature they have published though.
Poke around here, there are other good articles too
https://marinehowto.com/how-fast-can...ry-be-charged/

This is specific to this question though

[a64pilot]

Originally Posted by Oceansailor

And will there be any significant difference for the last 20 % up to 100 % SOC? The last question is important as many cruisers use solar for top charging.

I don’t think so, read Maine Sails article. I wouldn’t advise buying an AGM bank on the theoretical faster charge rate, yes it’s real, it does exist, just it’s not all that much faster, and AGM’s need to be fully charged more often than regular flooded batteries.
Buy an AGM cause a regular battery won’t fit, or maybe you have to put them in an inaccessible location where watering isn’t possible, or other reasons, but not for faster charging.

[Locquatious]

Originally Posted by Oceansailor

T Let’s discuss the original question. How much difference it is charging a large AGM bank vs a flooded bank instead? And will there be any significant difference for the last 20 % up to 100 % SOC? The last question is important as many cruisers use solar for top charging.

See Charging Information For Lead Acid Batteries – Battery University The topping charge is essential to prevent sulfation. Since the AGM's have a higher acceptance rate one would expect that the bulk charging would occur faster. Solar should be fine, if the solar system has the current capacity when the regulator is set to the proper topping voltage. Then when the topping charge is complete (i.e. the topping current drops to a minimum level) the solar regulator should revert to the float charge voltage. One might expect that the AGM, with the larger charge acceptance surface area, would accept the topping charge more quickly than flooded batteries.

In other words, suppose the solar panels can provide 20A at a 14.8V topping voltage. When the alternator topping current drops down to 20A, shut the engine down and the solar panels will take over the remaining topping charge. If you shut the engine down too soon when there is higher topping current, the solar panel voltage will drop below the topping voltage.

[Oceansailor]

I tend to agree with a64pilot that in real life there is no significant difference in charge time.

One of the limitations is that most boats do not have the charge capacity to take advantage of the higher absorb rate from AGM.

Flooded golf cart batteries accept 14.9 V. I think that compensates for the lower resistance. My first bank was 645 Ah flooded DEKA. I do remember more or less the same output from the alternators as I have today with the 880 AH AGM. I’m sure it can be explained by the fact that with a smaller bank the SOC was many times lower when the charge cycle started. I do find myself cycling the batteries shallower with a larger bank. Starting charging at 65 % SOC is inefficient compared to 50%.

The solution might be to go back to a smaller bank and accept the fact that there will be more and deeper cycles. Mainsail do write that batteries are murdered and not cycled to death. I do agree with that statement. Batteries independent if they are AGM or flooded die by PSOC.

Another advantage with a smaller bank, would also be that it is easier to top up with limited solar capacity.

[john61ct]

Yes they will be slower than new AGM in the 50-80% curve, but maybe a half hour?

But much more resilient to PSOC abuse amd longer lived.

[a64pilot]

Originally Posted by Oceansailor

Another advantage with a smaller bank, would also be that it is easier to top up with limited solar capacity.

Actually with Solar it’s more of a time limit than anything else, remember in Maine Sails test it took over 5 hours when charging with a BIG source to get completely charged, but only 12 min longer with half the size of source. Of course Solar wise, they were both big.
Most likely your not going to get to 100% SOC without kicking them hard early in the morning with an alternator or Honda running your shorepower charger.
But you do that twice a week, and at least twice a week you can get to truly, fully charged, which is twice a week more often than many do.
Really for full time cruising, a little Honda or other generator is just hard to do without, how else you going to equalize?

If you look at almost any manufactures life expectancy, twice as big a bank discharged to 75% as opposed to being discharged to 50% will last longer than twice as long.
Lifelines chart, it’s likely to be sideways, sorry but with the IPad to get the whole thing that is what I had to do.


Another issue with deeper discharges, is most people don’t get fully recharged when discharging by 25%, what are the odds of being fully recharged if they go deeper to 50% ?

[kmacdonald]

The 6 volt golf cart batteries are the best bang for the buck but there are valid reasons to have AGM or lithium. Depends on priorities, climate, charge abilities, etc.

[a64pilot]

For me it was as simple as GC2’s won’t fit.