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Old 07-12-2015, 05:26 PM   #1
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Default Lifeline battery testing results

Since we will usually be using our new batteries with moderate discharges of hopefully under 50% most of the time, I decided to run a test of the batteries and charger to see what to expect in the real world once they are installed. Hopefully, it will also give some insight to how they will behave off of the engine and solar charging also. The cable length issue and getting the charger to start bulk automatically were already fixed when this was run.

The batteries are Lifeline GPL4CT 6 volt GC2 case batteries wired series first than parallel for a total of 440ah at 12 volts. Charger is a 100 amp Magnum setup for return (ending) amp float transition and with 14.5 volt absorption that is temp controlled.

The batteries had been charged totally as series pairs, not together, as the state of charge was quite different between them. It was done as return amp transition, so they were as full as they would get.

I used a hotplate running through the Magnum 2000 watt PSW inverter for most of the draw down, running at 65 amps with some off time when the hotplate thermostat cycled. Some was also done testing things like DW's home hair dryer to see how much it would pull and if the batteries could do it. (173 amps of DC). On average it was at about the 8 hour discharge rate, which is much faster than we usually use power as we would be in the 100-200 hour rate.

The 65 amp load dropped the voltage by about .5 volts compared to rested batteries. I only had two spots to test, at the start and finish, but it was the same at both.

I monitored the current coming out of each of the batteries over the entire discharge time, and it was never more than 1 amp difference between them. I was very surprised, and happy, about that.

At the end of the test, stopped when 220ah had been removed, the batteries were reading 12.13 volts. They recovered to 12.3 volts after a couple hours rest. This is very surprising as the 12.3 volts on the 8hr discharge curve would only be 32% discharge, not the 50% indicated by the 220ah removal. It is even less than expected if we were at the 20 hour rate where it would indicate a 40% discharge. Either the batteries are performing way better than predicted, or the chart is wrong, or I am doing something wrong, as that is a pretty significant difference.

Here is how it looks on the state of discharge chart

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File Type: jpg Lifeline SOC chart.jpg (90.7 KB, 43 views)
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Old 07-12-2015, 05:54 PM   #2
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Previous post had the discharge information, this will have the recharge information which is, at least to us, what counts more.

I basically just turned on the charger and let it go, monitoring the amps it was putting in and the amp hours it was accumulating. I also checked the balance of amps between the two sets of batteries, as I did when discharging, and they again were within one amp of each other over the entire test. It all looks pretty much what you might expect, except the time in absorption is much longer than any of the timed charging charts that I have seen would indicate.

Here is a graphing of the test, which ran 12+ hours to complete the charging to the return amp minimum. At the end, it still was not at the minimum amps at 14.5 volts, so I moved it down to their nominal of 14.3 and it came in. Lifeline states the minimum amps of .5%C should be good at all voltages, but I just don't see how that could happen.



The charger stayed at full output for about 100 minutes then transitioned out of bulk to absorption. At about 250 minutes the charging amps really started to go low, but then dropped very slowly from there. The normal bulk plus 2-4 hours absorption would have left the batteries quite a bit short.

I have read a lot places that the deeper the discharge, the more absorption time you need to get full again, even though the bulk takes you to essentially the same SOC point in recharge. This discharge was under 50%, so it would be interesting to see if it stretches out even more at a deep discharge, or by using ending amps, it just makes all the absorption cycles as long as the deep ones would be.

What this does show, is that it is going to be kind of difficult to get totally full in a day of driving, although certainly not impossible. For a discharge of this depth, the engine would probably get you to absorption in about an hour, so you would still need around 11 hours of driving or enough sunlight to generate the under 5 amps it takes to finish the charging, plus of course what the van is using.

You would get very close on almost all days, I think, but could be a few hours short. That is a minimal amount of capacity lost, and is also a better charge than probably 98% of shore chargers do. By getting that close nearly all the time, I would think would make an occasional shore charge very effective.

I think the only times we would be operating in the less than very close to full range would be if you were on solar only, no driving, and the conditions weren't perfect, as the solar would not get to absorption soon enough in the day to have time to do the long hold time.

With this information, if it duplicates in the van, we should be able to very effortlessly be able to stay off grid as much as we want, and still take good care of the batteries.

I think Marco's statement that he thinks most batteries are being undercharged (which I agree with completely) would certainly be backed up by this test.
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Old 07-12-2015, 06:21 PM   #3
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It's so useful to have that battery manual from Lifeline with clear guidelines.
Below 0.5% current flow in at 77F and at 14.3V is what is specified.

Most of us don't get battery manuals with the batteries and we're left guessing. If I keep upping the voltage more amps flow in ....... when / where do you stop when you don't have that info in a manual? (rhetorical)

What output do you expect from your new alternator? I'm guessing that will speed things up coupled with your typical use being much less than the 8hr discharge rate you used in the testing.
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Old 07-12-2015, 07:19 PM   #4
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The manual is very nice to have, surprisingly they don't send one with the batteries, just a little bifold thing that doesn't say much.

The absorption voltage, and the ending amps that go with it, are probably the thing they need to settle on, and get all the literature, and personnel, on the same page.

The tech manual says (I will use all 12v equivalent) 14.3 +/-.1 volt, and in one place the ending amps of .5% is right with that spec. Other places they just say the .5%, with no voltage reference, other charging info in the manual is the same 14.3v.

On the batteries the sticker says 14.3+/-.1

The little bifold sheet also at 14.3+/-.1

But--the spec sheets for almost all the individual batteries that are on the website show 14.1 to 14.6 or 14.2 to 14.6 absorption volts.

When I couldn't get to the .5% initially, I called and asked what voltage that .5% should be at(I thought maybe it was really for float or something), and the tech said for the entire charge range, which would be either 14.3 +/-.1 or 14.1-14.6 volts depending on what literature you believe. I specifically asked if I should be able to get there at the 14.5v I was running, and he said yes.

I have to believe he was incorrect in what he said as the amperage has to change, as mine did. It went form 2.6+amps to 2.2 by changing .2 volts. .5% is a very low return amp setting. Magnum recommends setting at .05C (5%) Which is just plain silly.

I do believe the higher voltages are probably the preferred ones, at this point, and the literature hasn't caught up yet. A couple of years ago when I was talking to Lifeline, they mentioned they were thinking of increasing the voltage to 14.6 or 14.7 volts to help with capacity loss and short charging. They probably don't want to say that as an across the board recommendation, as that would be pretty high for a full charge cycle on top of full batteries, and that can easily happen in most systems. Other AGM manufacturers have been increasing to 14.6/14.7 volts, so I think most will wind up there soon.

The alternator thing is still up in the air. I have no idea how much it will deliver through the smallish wiring, and combined with getting the alternator itself hot. I am hoping it self limits to under 200 amps (250 alt) and 180 would be nice. In reality, it won't save all that much time off of a complete fill to ending amp cycle, even if it was at 200 amps, as the Magnum does 100 amps and only took 1.5 hours to go to absorption and be below 100 amps. It would be of benefit if we are off grid and running in the middle of the SOC, and need to get some capacity back with the engine, though. Idling does about 120 amps, based on the microwave tests, so we could get a days capacity in about 30 minutes at idle. Might be worth it to help prevent a very deep discharge, or maybe not.
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