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Old 26-06-2014, 09:13   #31
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by Maine Sail View Post

It is no secret that higher voltages mean faster charging for all batteries but it has to be done within reason........
And Mr. Sterling makes this point: "Also bear in mind that this test was charging a 100Ah battery at 150A, in real life with 4 x 100Ah batteries you would need a 500A alternator or battery charger to be able to reproduce this test run, so, it is unlikely that one would have a charging source that good."

The real point of his experiment was not to get batteries to take more current using unrealistic voltages, but to show that higher reasonable voltages are actually good to use. Keep in mind that this article is older and written when many chargers were using lower voltages, or could not provide enough current to achieve higher voltages quickly. And there were a lot of wive's tales in the user community.

I saw nothing in that article that is not considered "normal" today.

Mark
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Old 26-06-2014, 11:05   #32
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by mitiempo View Post
I disagree with this. While you want a minimum for efficient charging there is no maximum. The battery is the determining factor not the charging current. A charger cannot be too large.
It's good to have some discussion on here from you instead of just being SHOUTED AT by colemj. He just seems to ruin some threads.

I don't believe you support Mr Sterling's 160 amps into a 100 Ah battery? Look at Trojans recommendations for FLA maximum voltage and current from their data sheets. The max current is 10-13% of the capacity C. Rolls quote 10%C at the 20 hour rate [15%C at the 6 hour rate]. Only Lifeline recommend HIGHER than 20% C, and even at 50%C this will hold for quiet a while before battery acceptance reduces the current. (See Btrafors real world testings). As you see from Mr Sterling's Advanced Charging you can put in a huge current for a short while, but this is not what the manufacturers recommend

Having a large charger with FLAs is pointless because they will self regulate, but with AGMs and a large charger they wil self regulate at a much higher current so you will get more Ah in more quickly. So if you charge FLAs at 10%C and Lifeline AGMs at 50%C then they will accept more Ah up to and slightly beyond the end of the Boost stage.

But I was disregarding all this in my posting #9 when I was saying to the OP that Lifeline AGMs will charge faster than Trojans because of Charge Efficiency and not because of a larger Charge Acceptance Rate. Nobody seems to have taken that on board.

I apologise if Maine Sail took offence to my comments on Mr Sterling, but most professionals in the UK would agree with me. It depends what dictionary you use and maybe what side of the pond you are on. Charging a 100 amp battery at 160 amps is a 'foolish, or very stupid' thing to do, and pretending this is 'ok' is even worse. Clearly he is not 'mentally retarded' which is another definition of 'Idiot'.

Sorry about the 50C temperature I quoted. This was fairly easy to interpret wrongly, but if he had done it with a thick plate deep cycle battery then who knows what would have happened. His battery went up 14 degrees starting at 18C. If it was here in the Med where temps start at 35C, then he would probably have got to 50C. Not a good idea for prolonged battery life. Battery life cycles are reduced by something like 50% for every 10 deg C rise in temp above 25C.
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Old 26-06-2014, 12:13   #33
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by mitiempo View Post
Trojan recommends 10% of C as a charger that will do, not as a maximum. The battery is the determining factor. At a given voltage it determines the current it will accept, not the charger. A charger cannot be too large.

From Trojan:
What that quote from Trojan says to me is that a 10% charger is minimally acceptable but no more than 20% for larger chargers.
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Old 26-06-2014, 13:07   #34
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Re: Lifeline vs. Trojan Charging speed

How fast can you charge a lead acid battery, how much current can you apply.

From Rick Young EE and CF member

The answer: A charging current equal to the value of the number of Amp-hours missing from the battery will not excessively gas or heat the battery. This is the so-called "Amp-hour Law" which was proposed many years ago in the literature. Now what's interesting about this concept is that a charge curve following this "law" forms what is called the curve of Epsilon, an ever decreasing curve of charge current. What is also interesting is that when using 3-step chargers having an appropriately set absorption voltage and a sufficiently large charge source the resulting curve will almost approximate the Amp-hour law. When precisely following this curve you can safely recharge an 100% discharged battery in 3 1/2 hours with many AGM and GEL cel batteries and closer to 4 hours for flooded batteries. All lead-acid batteries designed to deliver heavy discharge currents (like you need for cruising with a microwave oven, etc) will be capable of folloing this "law".

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It's to bad Rick no longer comments on this forum.

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Old 26-06-2014, 14:31   #35
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Re: Lifeline vs. Trojan Charging speed

Anyone who is interested in this can read that Sterling experiment. If they do, they will find that your interpretation of what you read is in stark contrast to what he published.

For example, he was not charging a 100Ahr battery with 160A of current like you keep claiming. His graphical data and writeup clearly show that the most current ever accepted by that battery was 160A - and that only at the beginning. His data shows that current dropping quickly to 60A, and would have been below 25A rather quickly if he had let it go - you can infer the speed of that by the linearity portions of the SOC graphs.

He was only able to even do this because he chose a small battery and had a very large charging source that could keep up with the battery's natural acceptance rate and drive the battery to 14.8V quickly. His point in doing so was to show with actual data that no harm is done by using higher absorption voltages during charging.

He then makes the very clear point that it would be rare indeed that anyone would actually have this level of charging ability in practice. However, he demonstrates that even with lesser current charging sources, using higher voltages allows more usable current to be restored to the batteries before full charge is reached. By higher voltages, he means the voltages in common use today - they were not necessarily in common use when this was written.

In other words, he is simply showing experimental results supporting the charging regimes in common use today. Since Lloyd posted Rick's thoughts on amp-hour law, it is obvious that Sterling's results also support that. You can see the Epsilon curve clearly in Sterling's first graph.

Now, here is where Sterling gets tricky in the name of marketing, and where your comprehension may have been confused. He does not provide any time scale when making his point about charge acceptance speed on his first graph, and chooses to make his second point about charged stored on his second graph by picking a point in time that did not represent a full charge of the batteries - and then running those different SOC's flat. If, instead, he chose to fully charge the batteries at different voltages (13.8-14.8V), he would have found that all of them would run the load for the same time.

Sterling's results are as true for AGM's as they are for FLA's - it doesn't matter the form of LA the battery takes. It also doesn't matter that he was not using a deep cycle battery. If he had, no harm would have been done to it - it certainly would not have boiled hot like you suggest - it merely would have not shown his point so dramatically. Instead, the surface charge on it would have built so quickly, that the current acceptance would have plummeted. Also, the differences in charge stored would have been less in the short time he chose for his second point.

So, in summary, Sterling proved commonly accepted physical charging characteristics of a FLA, then did a bit of slight-of-hand to imply that his chargers could perform this function while "others" may not. None of that is false, it just isn't the sole truth.

Where Sterling did good was in helping to convince people that large charging sources and higher voltages are good things - particularly when the batteries are not being fully charged each charge cycle. I see too many boaters with 600+ Ahr battery banks and 20A chargers set at 14.2-14.4V, and using 50-75% cycles. He seems to have failed to make that point with you, but it is no reason to call him an idiot no matter which dictionary you use.

The debate about whether FLA's should be charged at 0.1C or 0.25C is meaningless because it is a rare boat that gets to 0.25C, let alone above that. Additionally, as others have pointed out (so you don't have to take only my word), the battery will determine the acceptance rate if the voltage is limited. There is no such practical thing on a boat as too "large" of a charger. Mr. Sterling is making the point that there is such a thing as too small of one.

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Old 26-06-2014, 20:20   #36
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by colemj View Post

The debate about whether FLA's should be charged at 0.1C or 0.25C is meaningless because it is a rare boat that gets to 0.25C, let alone above that. Additionally, as others have pointed out (so you don't have to take only my word), the battery will determine the acceptance rate if the voltage is limited. There is no such practical thing on a boat as too "large" of a charger. Mr. Sterling is making the point that there is such a thing as too small of one.

Mark
I don't believe that it is a "...rare boat that gets to 0.25C, let alone above that."

Rare among offshore cruisers but not the majority who only spend weekends and an annual 2 weeks or so away from the dock. Many boats have 2 group 27 batteries - one for starting and one for house loads. The start battery is only down .5 AH or less after an engine start and recharged to full quickly so it is not a factor. That leaves one group 27 of about 100 AH. Many AC powered chargers are over 30 amp output - 40 being very common.
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Old 26-06-2014, 23:23   #37
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by colemj View Post
And Mr. Sterling makes this point: "Also bear in mind that this test was charging a 100Ah battery at 150A, in real life with 4 x 100Ah batteries you would need a 500A alternator or battery charger to be able to reproduce this test run, so, it is unlikely that one would have a charging source that good."

I have made a 1600ah agm bank with 320a of chargers and 275a alt. we only managed to get around 400a charging. (normally the gen isn't on if the engine is but I had to try with both!) bank was wired in double 4/0 to handle 600a

so we got less then the 40% number you normally see for charging agm. batteries were at 60% or so SOC.
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Old 27-06-2014, 08:39   #38
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by mitiempo View Post
I don't believe that it is a "...rare boat that gets to 0.25C, let alone above that."

Rare among offshore cruisers but not the majority who only spend weekends and an annual 2 weeks or so away from the dock. Many boats have 2 group 27 batteries - one for starting and one for house loads. The start battery is only down .5 AH or less after an engine start and recharged to full quickly so it is not a factor. That leaves one group 27 of about 100 AH. Many AC powered chargers are over 30 amp output - 40 being very common.
Yes, I meant it was rare for a cruising boat - most of which have banks of minimal 400Ahr capacities.

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Old 27-06-2014, 08:41   #39
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Re: Lifeline vs. Trojan Charging speed

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Originally Posted by smac999 View Post
I have made a 1600ah agm bank with 320a of chargers and 275a alt. we only managed to get around 400a charging. (normally the gen isn't on if the engine is but I had to try with both!) bank was wired in double 4/0 to handle 600a

so we got less then the 40% number you normally see for charging agm. batteries were at 60% or so SOC.
Please ask the mods to delete this post - and move yourself closer to the Kool-Aid.

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