Quote:
Originally Posted by breezeway95
The Ah screen on the RM-s is showing the cumulative number of amp hours that have gone into your battery bank. The Ah counters can be reset by pressing and holding the left and right buttons together for about 2 seconds. The solar Ah counter is showing what has come into the controller. This is separate from the battery 1 and battery 2 Ah counters since the SSDuo has the ability to charge 2 independent battery banks.
I do not see how adding more solar panels will cause any 'overcharging'(not the term I would use here). Every morning the sun comes out the controller will attempt to go through a full bulk-absorption-float cycle, this is regardless of how much solar power you may have. I suppose if your solar array is currently undersized causing you not to have enough power to get into absorption and float than you would 'overcharge'(again, not the term I would use here). Your batteries, as they become fully charged, will limit the amount of current needed to maintain the regulation voltage the controller is set for, assuming you actually have enough solar power.
With all of that said, if you have your batteries on some other charging source(like shore power or some other mains hook up) and you are floating for a very long period of time the SSDuo going through its daily full charge cycle may be problematic(if left to do this for a very long period of time). If there is no other charging source and this is purely solar you should be fine going through the full absorption-float cycle daily but you may want to exercise(discharge and then recharge) your batteries occasionally. I would suggest speaking with your battery manufacturer to see what they recommend as they will know best and not all batteries are created/designed equally.
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I think you may have misunderstood a couple of points in my original post, so I will try to clarify.
Re the AH counters. The counter from the panels is exactly what they say, except we don't know if they are going to stay with amps if you have higher input voltage from multiple panels. Not critical as it will obvious when the AH in are much lower than the AH out.
For the battery 1 and battery 2 outputs, the information they gave you is accurate some of the time, or maybe all the time, depending on your system wiring. The Duo does not measure amps right at the batteries. It measures the amps internally in the controller, so what the AH counters are measuring is the AH leaving the controller, which can be way different than the AH entering the batteries if there is any power use going on in the van during solar charging. Say that your 100 watt panel is putting out 5 amps in good sun, and you have 3 amps of stuff running in the van at that time. The AH counters are going to see 5AH going out of the controller, but the batteries will only get 2AH of it because 3AH of it went to the van use directly. This is why "monitors" and totalizers that don't measure the actual amps going into the batteries won't be very accurate sometimes for knowing how much you charged the batteries. Normally, most of us use the solar output AH as a way to evaluate solar harvesting amounts, not battery charging. Aside from the inaccurate charge information, there can be another issue with not measuring the amps at the batteries in that some controllers look at the amps going out to determine if they should go to float. If there is load taking some of the amps, the controller will think the batteries are still needing more charge when they may not need it. I don't think the Duo does any look at the amps, so it probably does not apply to this case.
More solar panels can definitely cause more chance of overcharge, for reasons similar to what you stated. I don't know if this would apply to the Duo or not, as the manual did not put any times on the charge profile to know what exactly it does. If you have small panel capacity compared to use, you will never get to float, so you would not overcharge because you won't even get full. If you have lots of capacity and shallow discharge because of a big bank, the solar will get to absorption quicker and depending on how the profile is controlled could be in absorption too long. Most controllers will intentionally use short absorption times to counteract this issue, which then leaves you short of fully charge, but not over charged. The biggest danger times with solar are when the batteries are already full, as they would be when the van is on shore power float, or even if the van is not being used and is just sitting in the sun with little or no power being used. In these cases, if the controller runs a full charge cycle, the batteries can see upwards of 4 hrs a day (typical absorption timer setting for solar), every day. I know of a couple of cases where Sunsavers took out wet cells in a couple of weeks that way. AGMs won't go dry and fail, but will be dried out and their life shortened. In these circumstances, more panel capacity would mean the solar would be more likely to be able to put out enough current even in bad sun to overcharge.
I would agree that with most solar installs that a solar only cycle every day with full charge program won't hurt things, but that is only if you are using enough power so the batteries need the charge time and aren't just getting full voltage on them when full. AGMs will only lose a tiny amount AH in storage, so would be essentially full every day when charging started from the solar, if the van was just sitting with no power use.
The question of whether batteries are better off being long term floated or cycled regularly when in storage has come up on the forum several times in the past, once just a little while ago. The manufacturers are very squishy on giving a for sure answer on the question, so we really don't know. What I am pretty sure of, though, based on what they said, is that if you chose to cycle the batteries you need to discharge them fairly rapidly to a level more than 10% down and then recharge them immediately. A slow discharge leaves part of the capacity uncharged for a long time, which can damage that part of the battery. Discharges of less than 10% are said to not be good for the battery, but we don't know the mechanism. It may not be true if you have very good charging equipment that won't overcharge things, but true on other chargers. Personally, I leave our Lifeline AGMs on float (at the lowest voltage in the recommended range for float) all the time when the van is not being used. Maybe once a month if I am in the shop where the van is, I will turn on a bunch of stuff to get the batteries down 20-30% and then immediately recharge to true full. I figure this kind of covers both ideas of what is best, but that is truly just a guess.
Amp hours meter display
Linear Mode
