Efficiency setting/Ending Amps in relation to aging batteries

[Smitty77]

(I deleted this thread from under the Classic 150 and moved it here.)

We are RV'ers, with 800AH's of X's4 Lifeline L16's. 1200W 48V Solar feeding the bank via the Classic 150. Also have the Magnum MS2812 in the mix while on Shore or Generator Power.

Our battery bank is 3 years old. As I understand it, Lifeline says to compensate for aging batteries, by altering Efficiency settings(?). I changed our Efficiency value 94% for our gently used (Very seldom not 100% SOC during the day. And while Boon Docking we usually wake to between 70-80% SOC, and over the last 3 years, Boon Docking represents about 15-20%. So, our three year battery bank, is still relatively young, compared to say a boater that is very seldom on Shore Power, may reach 100% once a week, and 50% SOC is quite common. The 'how used mileage' can make a difference.

Ending Amps would be 4 amps for our bank (.5 X if this was a new battery bank. But with three years old batteries, my thinking is that the Ending Amps should be adjusted to compensate for battery aging(?).

How much would you guys SWAG the adjustment to my Ending Amps value? Suggested value?

I'm very much a rookie on all of this, so my thinking maybe way out in left field, or belong in DC:)!

Best to all, and TIA,
Smitty

[Robin]

I am not an expert either, but yesterday I was listening to Steve Higgins from Surrette talking about using end amps as a possible problem. He was saying that using end amps may not allow for a long enough absorption time. Now I always thought the reason for end amps was to take the guess work out of it?

[zoneblue]

Bob has occasionally mentioned the idea of doing x mins past EA, for reasons related to the above.

I got the impression that EA increases over time. Ie as the battery ages, the charge acceptance taper rises, not lowers, thus if you set it too low it will never trigger and fall back to absorb time. When in doubt check SGs from time to time and adjust things as required.

One other thing, is that around here some of the installers increase the absorb voltage by 0.1V per year of the batterys life.

[Smitty77]

It was a comment in the WhizBangJr on setting End Amps, that made me concerned that I not set it with the wrong amount. Same basic comment, about too much, or too little - and you may never end the charge, or you may never fully charge:)!

I called Lifeline, and from talking it out with them, they said yes to compensate for battery age. Great. But by how much? And, no definitive answer from that question... Thus my pondering here for those with greater experience on all things batteries:)!

And SG measuring in Lifeline's is difficult to say they least. I would need to follow the Lifeline battery voltage health test, to get close knowing true Efficiency (or in this case, degradation) compared to a new battery.

I'd like to use Ending Amps, and thinking instead of the New/Fresh battery bank setting of 4Amps, of bumping it to 4.25 - 4.75 Amps range, to be sure I don't under charge the batteries. But, that is where I'm dangerous, as I'm know I'm not always getting all of this stuff yet. And that range of Ending Amp value is my SWAG:)!

And due to the bank now being 3 years old, but relatively non abused batteries, so I consider them to be younger, I've bumped up Absorb to 2 1/2 hours from 2, just to be sure I'm really getting them to above 100% SOC as far as returning used Amp Hours.

Ending Hours vs time Absorb Hours settings? So, my thinking was if the battery bank is fully charged form the Magnum charger on Shore Power. That the Classic/Whiz Bang Jr combo would quickly determine the batteries are fully charged, via some value I enter for Ending Amps, then shift the Classic 150 to float way earlier then 2 1/2 hours of Absorb Time...

It's neat that MidNite has the Ending Amp option, but could do more damage then good, if the values are not loaded correctly...

I think? (And probably trying to overthink things...)

Best,
Smitty

[zoneblue]

Mate, 2hrs is not nearly long enough. A bank that size when in any reasonable DOD will need 3-6 hours of absorb.

Are you saying these are AGM L16s?  If so then the following is the recommended procedure for setting EA and abs time.

0. Choose a sunny day when float is assured.
1. Disconnect all non essential loads.
2. Make sure the classic is set to use WBJr for absorb termination.
3. Set absorb time to 10hrs, and EA to 0. (temporarily).
4. As absorb starts either log using any of the logging tools available to you (local app, mymidnite etc), or every half hour take a battery charge current reading, and draw yourself a graph on excel.
5. What you looking for is the point that the charge acceptence tapers to flatline. Taht is your true end amps. Youll need to add 0.5A to this figure to ensure a reliable trigger.
6. Reconfgure the classic to use this value.
7. Set the absorb time to a suitable safety fall back value. If this particular day the bank was about as low a DOD as you tend to go, add one hour to the actual time it took to reach EA flatline. If it was lightly discharged that day added another hour or two as needed to ensure that EA always gets first shot.

Clear?

[Smitty77]

Thanks Zoneblue...

Yes, they're L16's Lifelines.

And this method sure looks like it takes the 'guestimation' out of the determination. And I could repeat it every year, to see if the aging of the batteries has moved the point of EA from where it had been set.

I'll do this a couple of times and pick a value.

That being said, my neighbor (Here where we're parked for a few months in Yuma, AZ.) asked me 'Why bother with EA?'. He said he thought the controller would be smart enough to 'Stay in Absorb for the set time. Or, until the batteries voltage met the Absorb voltage level. Whichever came first, would shift the controller to Float mode.' I've tried reading down thru the MidNite manual, and dang if I spotted anything that said it would shift to Float once Absorb voltage level was met?

(Oh, and on the Absorb level. When boon docking, I set Absorb to 3 to 3 1/2 hours. When on Shore Power, I set it back, or even turn off the MidNite. The Magnum MS2812 Charger seems to do a good job on keeping the batteries charged. Even when plugged in, nighttime usage of lights, and the 12V draws, will consume 40-60A. So the Magnum will cycle on as needed to bring the battery level back up to 100% SOC. So some steady exercise, while still lightly using up Lifecycles.)

Thanks again,
Smitty

[zoneblue]

Hopefully from my post you can now see how EA works. In the midnite world the absorb termination (the transition to float) is determined by which ever comes first, EA (if set) or absorb time. EA is by far preferable because it tailors each absord to how deeply discharged the bank was that day. A fixed time, which all other controllers use (if they have EA its based on CC output amps, some of which are going to loads, thus not worth relying on, unless you have no loads or constant loads) will sometimes be too short, sometimes too long.

However.... you have two (or maybe more charge sources. This is where things get colorful.
Whenever there are multiple charge sources, you need to:
- try to set them all with the same setpoitns, ie absord voltage, and float voltage
- make sure they are all temp compensated using the same setting 5mV/*C or as specified, with teh sensors placed on the same battery.
- calibrate the sources  using a reliable multimeter, ie if one of the sources runs low, up it a bit
- for EA, as said above youre unlikley to find an equivalent to the classics EA algo, thus you have no choice but to make the best of it. If the inverters charger is considered the secondary source, then set the absorb time to the lower end of what your absorb takes on average.

Its never going to be perfect, and it doesnt need to be. Even if the two chargers squable a bit it doenst matter. The other will just rest, get lazy and put its feet up.

HTH.