jrnymn7 wrote:
BFL13 wrote:
I posted a long time ago about the big losses from successive 50-90s and did some additional trails testing on that "progressive capacity loss"
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/24849190.cfm
I found that after about five 50-90s the capacity was down too far to get through the next night. The limit being you need enough to get through that night so you can do another 50-90 next morning. Since the regular time we needed a 50-90 was every two days with our particular AH usage, that meant the time limit was ten days to two weeks and we were stuck.
Next step was go home and do "recovery" on the batteries whose SG was so low you couldn't even find it :) Mex is right about the fun it is to do a "recovery" Takes a few days before you can go off-grid again for another ten days or so. One night with hook-ups is not enough time to do a "recovery"
The cure was solar. Shallow cycles and reaching high SOC (but not necessarily to full) means you can go weeks and weeks off-grid and not have progressive capacity loss that you will ever notice. Even so you should do an equalization every month to make sure you can still get back to "baseline SG"
I may still be a little confused about this 'progressive capacity loss issue', and am finding difficulty in phrasing my question(s). Please keep in mind I have no experience with dealing with this, as I was, if anything, over-charging with my peak 40, and never did below a 97-100% re-charge; usually ~ 85-100's every other day.
This progressive loss, is it due to sulfation, or some other related chemical reaction/phenomenon, or is it simply a matter of say using 50%, replacing only 45%, then again using 50% of that, and again replacing only 45%, and so on, until you simply run out of available power?
Thanks!
It's in the nature of battery chemistry. The plates on your battery are like the bowl of a bong... it gets' really sticky down there, with regular use, residue (sulfur in the case of your battery plates) sticking to the Lead Oxide. The plates need exposure to battery acid, sulfur build up from incomplete full top off recharges prevents that, kind of forms a chemical barrier, clogging up all the nooks and crannys.
When this happens, you lose battery capacity. It's like letting bathroom shower tiles and grout go with a thorough cleaning from time to time.
So you bring an aggressive cleaner in and lay on the elbow grease to get things spic and span. How do you do this with a battery? The light cleaning version, or regular cleaning, is a top charge. Charge with 15.0V until the amps drop way, way, way low.
If you got lazy, and didn't do enough 15.0V scrubbings between normal usage, now you have to do the heavy duty Mr. Clean version on your lead plates. First you do the regular cleaning with 15.0V, as much as it will take. Let it sit for an hour after that is finished.
Then you do the hard core cleaning with an Equalization charge. You try to charge at constant amps c/20 rate, and apply 16.0V at the equalizer charger, and measure voltage at the battery terminal for variance.
You want one of two things to happen in 30 minutes to 2 or 3 hours. Either your SG reaches 1.275 or better on the Weak sister cell, matching all it's brothers, or the voltage at the battery terminals reaches 16.0V. When either of those two happen, while you watch Mr.Clean cleaning like a peregrine falcon, you pull the plug on the EQ charger.
Really, it is that easy, when you are dry camping or off the grid. Some folks just skip the charge controller on their solar panel to do an equalization. Others get an old fashioned manual charger to 'git 'er done". The key is the ability to change the charging voltage manually, and keep an eye on things manually when doing the cleaning jobs... there just flat is no "set it and forget it" gizmo that will do it right... it's one of those types of jobs where if you want it done right, you have to flat out do it yourself.
With just a single Screwy T-1275 battery, or Screwy group 31 battery, I can see the SG on my 3 year old battery drop off with a Top Charge 15 to 20 points in 7 days of use. I might get 1.255 to 1.260 SG readings, when 1.275 is what I see after a good through 60 to 90 minute equalization.
If your run group 27, 29 or 31 batteries, or a T -1275, pretty much anything in a car battery shape that is not really really tall, chances are good you have a Screwy battery that is a major PIA to top charge and to equalize, and it becomes much much more critical to stay on top of the maintenance scrubbing and cleaning/ top charging /equalization of your batteries. Sorry, it's just the nature of the design of the batteries, other priorities took place in their design over form following function. The T-105 and T-16's, however are the cats meow for easy cleaning and maintenance. Ask anyone that has dry camped and owned and charged /maintained them.
