What a battery monitor may not tell you

[Davydd]

Originally Posted by markopolo

I recall davydd reporting more than once that Advanced RV stopped charging to 100% in favor of charging to 99% ............

It hits 100% on the Silverscreen but quickly settles out to 99%. ARV described to me when they reprogrammed it that it was 99%. Same with 90-91% at the lower end. You do wonder how accurate any monitor is.

[booster]

Originally Posted by RossWilliams

Here is a quote from the article after he describes several real life scenarios:

"There are many scenarios we can paint that can cause some of these monitors to reset falsely & prematurely thus creating more counting errors.

For the average boater, simply turn off or program out auto-sync…

For the die hard electrically minded individuals out there it is possible to program auto-sync to still work, but this is a recipe you’ll need to figure out for your own system and your system only. There are far too many variables to give a cookie-cutter recipe for auto-sync especially when we start mixing in solar or wind etc.."

I take that to apply equally to the average rv owner. For someone with lithium batteries having the monitor reset to 100% SOC when it is really at 65% SOC may not be a huge problem. But someone with AGM batteries may end up running their batteries to 0% SOC and permanently damaging them.

Turning off the auto reset calibration is the single worst thing to do on a battery monitor, IMO, as it will destroy the accuracy by creating the charge efficiency accumulating errors the author claims to be getting rid of. All measurement systems need a reference point to count from and calibrate to, and for battery systems a totally full battery is that point. Why would you choose to ignore it and let the accuracy get progressively worse?



If the auto reset is nont being done, either the monitor is set up wrong in the settings, or the charging system is indequate and the monitor is telling you that. Very plain and simple.


Many of us have actual experience over varied systems with monitors so have a decent understanding about them, including what they can and can't do, and how to properly set them up.



I have one question..How many tests, evaluations, setups, or years of use have you done with a monitor(s)?


If you think a properly setup battery monitor on AGMs is going to reset at 65% SOC, you just don't understand how they work. Perhaps you are confusing the case of if the battery is in very bad condition and has lost 35% of it's ORIGINAL capacity, and is now a smaller capacity battery. You would then set the battery capacity to 65% of what it was because that is the current 100% full capacity of the worn out battery. The article actually explains this, and it is the correct and accurate thing to do, and it would be good for the battery, not bad.



I know you won't accept any idea that a monitor is useful, as your mind is made up, but many of us would not be without.


How do you know what your SOC is, and how accurate is it?

[avanti]

I couldn't imagine operating my rig without a proper monitor. It would be like trying to drive your car without a dashboard. Even putting aside the visibility into battery SOC and condition, you are also blind to the effects of operating your power consumers. How much did the heater and fridge REALLY consume last night? Does using the microwave to thaw hamburger really make a significant difference? Is it worth turning off the inverter all the time? TV? Keurig? Without a monitor, you literally have no idea. It is simply not practical to answer most such questions by calculation from the specs.

[GeorgeRa]

My starting point was with second generation of Link 10, missing from this chart is Trimetric from Bogard Engineering which surfaced in 1992.

[booster]

Isn't Rod Collins the guy that also wrote the articles about how much he liked the Smartgauge? If so, he has had been down on monitors for quite a while, and although he has a good reputation, you do start to wonder about conflicts.


At the time of the Smartgauge article, we were hoping that it would generate more interest so we would get some good, in RV, test results from someone, but that has just not happened. I would think the shuntless, easy to wire Smartgauge would be natural for the populace if it worked well, but nobody seems to use it.

[markopolo]

It might help some here to know much of theory presented in the marine how to article was first presented on the original smartgauge site in 2005 or 2006. Whilst new to some here it's old info to others. Being old info doesn't invalidate it but knowing that does put it in perspective.

Was anyone even talking about charging to ending amps back then?

Two quotes from the site re: Ah counters

SmartGauge Electronics - SmartGauge compared to Amp Hours Counters

We may have given the impression we do not like them and see no use for them. This could not be further from the truth. The engineer who designed the SmartGauge uses one on his own boat.

For non-technically minded people they simply do not work as battery state of charge meters.

Note the qualifier in the second quote and apply it to the ever increasing amount of information available today. It's not that difficult now to gain an understanding of how to use an Ah counter type meter and what to use it for.

[peteco]

Booster: hang in there, don't let the "odd poster" influence your posting.

One question: will a charger on float at 13.5v (my present Triplite) eventually fully charge a battery?

[markopolo]

Originally Posted by peteco

Booster: hang in there, don't let the "odd poster" influence your posting.

One question: will a charger on float at 13.5v (my present Triplite) eventually fully charge a battery?

I haven't been able to find any specific data re: the ratio of the completeness of lead sulphate conversion to/at different voltages during the charge cycle so I don't know for sure.

My thoughts: Assuming that the battery has already been through a less than perfect absorption phase then it still might not get fully charged at a float voltage but it will get to and remain substantially charged meaning likely good enough being that at some point it will again see higher charging voltages.

[booster]

Originally Posted by markopolo

I haven't been able to find any specific data re: the ratio of the completeness of lead sulphate conversion to/at different voltages during the charge cycle so I don't know for sure.

My thoughts: Assuming that the battery has already been through a less than perfect absorption phase then it still might not get fully charged at a float voltage but it will get to and remain substantially charged meaning likely good enough being that at some point it will again see higher charging voltages.

I have also not seen any definitive testing that would prove one way or the other if you can really finish a complete charge on float. The short test I performed in the first post was an initial test of just that idea though, and in that short time, the battery did not get full to float transition amp spec while on float even though enough amps had been returned to the battery. Longer float has not yet been tested, but I will try to work that in some place along the line here. One of the major goals of this thread was to point out this issue, which is very common with most chargers, and that a monitor won't be able to compensate for it, just tell you it is there, so you can fix it by improving the charging.



My GUESS, based only on associative things, is that the battery will not get totally full and/or will suffer hardened and unconvertable sulfating.


I am basing this on a trend in the lead acid battery business toward recommending a very high 15.5-16 volt extra stage at the end of the standard charge to float transition amps. They are very specific in saying that this stage has to come at the end of the normal full charge and not at another time, so it has to be on a very full battery. The age old equalization cycle that we all have heard about was also very specifically placed after a full charge was completed. Both the added cycles have been described as being to help convert the more hardened sulfate deposits with more voltage. I think pulse desufators do similar. Doing the stage at the end of a full charge may be needed to focus the power only to the unconverted sulfates and not to oxidizing things. Being at float forever will not convert that sulfate, and by the time the charge cycle comes around it will be even more unconvertible.



All of this is probably also part of the reason for multistage charging, coupled with added charging speed, which puts higher voltage on for the entire charge cycle (in theory).


I think the manufacturers are finally letting out some of what the knew for a long time, but didn't publish because the equipment couldn't do it. Extra stages, etc, or the Lifeline recommendations to charge at a higher amp rate of at least .2C for discharges of over 50% are all pretty recently let out to the public.


Again my guess, but it would appear that the best charging for lead acid will likely turn out to be high amps (.2-.4C?) and higher end of recommended voltage range transitioning at the float transition amps, plus a short mini equalize stage on at least the deeper discharges. Of course, we can't get a charger that would do all that yet, and it is questionable if we ever will before lead acid goes obsolete. I do think that fork lift battery chargers do most if not all of the above.


A tell tale recommendation may also point to a simple explanation. We are always told to "recharge a battery as soon as possible with a full charge". High voltage charging is fast, and float charging is very slow, so certainly float would lose that test.


Excellent question, though, and I hope we are able to learn enough to get a good answer to it.

[markopolo]

It's not clear to me that irrecoverable hardened sulfation can form at say 12.9 & above. I can find some support for and against that happening.

Crown & Optima seem to set a low bar: 12.4V!

https://www.crownbattery.com/news/su...ry-maintenance
https://www.optimabatteries.com/en-u...mber-batteries

My summer float voltage in the van has been 12.8V with automatic periodic boost to 13.2V (because no temperature compensation on the PD charger) for a while now & I keep forgetting to check the Trimetric before driving it. The Trimetric charged indicator lamp is lit when I return from driving the van for errands. For some reason I remember to look at it then. The combo of solar and high output from a cold alternator at first must be enough to meet my 14.3V & 1A or less acceptance set-point.

[booster]

Originally Posted by markopolo

It's not clear to me that irrecoverable hardened sulfation can form at say 12.9 & above. I can find some support for and against that happening.

Crown & Optima seem to set a low bar: 12.4V!

https://www.crownbattery.com/news/su...ry-maintenance
https://www.optimabatteries.com/en-u...mber-batteries

My summer float voltage in the van has been 12.8V with automatic periodic boost to 13.2V (because no temperature compensation on the PD charger) for a while now & I keep forgetting to check the Trimetric before driving it. The Trimetric charged indicator lamp is lit when I return from driving the van for errands. For some reason I remember to look at it then. The combo of solar and high output from a cold alternator at first must be enough to meet my 14.3V & 1A or less acceptance set-point.

It would be interesting if you could kick the charging voltage up to absorption (14.4?) after a prolonged period of your charge protocol to see how many amps it takes at that point and how long it takes to get to transition amps at full charge. Then run a discharge cycle and recharge to transition amps, let it sit until the surface charge is off, and then run another absorption cycle to see how many amps it takes and how long to get to transition amps. Comparing the amps taken initially and time to transition should give an indication of any difference in float holding good charge (not necessarily finishing a charge though) and the benefit of a periodic boost of absorption voltage. I think the whole thing is very easily to misunderstand because whenever you put absorption voltage on a rested battery it will refill the surface charge needed to go from float voltage to absorption voltage, which is not really battery capacity in the true sense as I think it is more capacitive than chemical storage.

[markopolo]

Given that we all seem to rely on the 20 hour AH rating which is a discharge down to 10.5V or maybe even 10.02V and few of us want to go below 12V would that affect how we use a battery monitor and what info we program in?

I realize that the rating is done under load but it's not a huge load.

[booster]

Originally Posted by markopolo

Given that we all seem to rely on the 20 hour AH rating which is a discharge down to 10.5V or maybe even 10.02V and few of us want to go below 12V would that affect how we use a battery monitor and what info we program in?

I realize that the rating is done under load but it's not a huge load.

That is a question that has come up before, and I did talk to both Bogart and Magnum about what "most" user do.


The whole idea if I understand what Marko is asking correctly, do you want the monitor to tell you what % of SOC you have compared to the 20 hour rate where 0% would be totally dead at 10.5v or would you rather have the monitor read the % of USABLE state of charge based on how far down you feel comfortable drawing down the batteries?


Bogart and Magnum both said it is completely personal choice for individuals that set their own, but that the good professional installers set it based a lot on how they think will be best and least confusing for individual customers. For instance if a boat customer was not at all interested in anything more than is power available they would program usable power, with the battery ah capacity setting at whatever they felt was the best balance of usable power vs battery life. If the final customer is one that would always go right to the end, they might use a 50% SOC or 1/2 the actual 20 hour rate for the setting because they would find it likely that the user would go past anyway by some and wouldn't want to have that be the last 20% of capacity. My guess would be that in marine applications where they know that the batteries will cycled in a always below full area, the pro installers would also reduce the amount of recharge needed to cause a monitor calibration to full so that 80% actual SOC could read 100% at that point because that would be as full as it ever got (high end of quick charging range). This is just speculation, though.



For essentially all of us, we can just set it however we want to see it. I set ours to the full battery capacity so it is actual SOC by definition, but it could easily be set at 20% actual also as long we know it. In our daily use I almost always am using the ah in and out instead of SOC, anyway, as I find it more useful. I look at the ah in/out screen and know how much (approximately because of charge efficiency) recovery charge is needed to full batteries. That makes it easy to have a good idea if the solar will get us full that day, and/or if I need to use the engine charging if we are driving, or other power decisions. For the most part, we don't really even need to look at the use any more as it is very consistent, as are the various charging cycles from the three sources. Some days we have net loss due to low solar input, but with our low use and large capacity it doesn't matter unless we want to stay more than about 5 days getting that complete loss of charging.



I think the mentioned part about the load at the 20 hour rating if interesting because the load will change the "rated" capacity somewhat so you could have a bit more or less actual energy left at 80% of ah rating used. Our average power use over a day would be at something like a 150+ hour rating, so our actual amount left at .8C ah use is quite a bit more than .2C as long as we are using it at our low rate. We have actually to this point not ever gotten to under about .6C ah down so we have lots of cushion if we need it with .2C to get to down .8C plus what extra would be there because of low load use to be at an actual .8C down.

[markopolo]

Thanks Booster. That answers what I was trying to ask. I'll continue to use the full 20 hr rating as the battery banks capacity in the settings.

[RossWilliams]

The AH rating from the manufacturer is new. You will need to adjust it downward as the battery ages. If you leave it at the manufactures rating you will soon be drawing it down further than you think. The point of the battery monitor is to avoid that.

[markopolo]

That's a good point. That's why the periodic capacity test is needed otherwise it's just a guess.

Can we make a guess? 2% per year for light use? 5% for heavier use?

I doubt Ross has a monitor. Has anyone ever installed a monitor in an E-Trek? We have to let this go and lets start over. It's easier for me to say that because I haven't been in the ring as much but I don't see any other way forward.

[booster]

Originally Posted by markopolo

That's a good point. That's why the periodic capacity test is needed otherwise it's just a guess.

Can we make a guess? 2% per year for light use? 5% for heavier use?

I doubt Ross has a monitor. Has anyone ever installed a monitor in an E-Trek? We have to let this go and lets start over. It's easier for me to say that because I haven't been in the ring as much but I don't see any other way forward.

I don't know if we could put a % a year or such on it, or even a number of cycles, in guessing at the capacity loss. I think the major cause of loss is poor charging either over or under, with over damaging faster and under a slower death. We know that under lab conditions and to amps based end of charge, folks like Lifeline say about 1100 cycles at 50% DOD until at 80% capacity, but we know that is short cycled, undercharged, systems you might get there in 300 cycles, and in badly overcharged you might only get 100 cycles to that point.



Our Lifelines are, I think, about 3-4 years old, and I did a capacity test to our reference point of 20% SOC last spring and it was the same as new, after breakin of 10 charge cycles. We do have very carefully controlled charging, though.


I do wish we could just let this go, but the record is getting dumped full of misrepresented and/or false information, which IMO is not good for anyone or the forum. I think anyone who comes back to this discussion in the future deserves to see the willingness to learn and share information of all that post, including those that only criticize. IMO, the refusal to answer simple, basic, questions while demanding NASA quality proof from others is just plain unacceptable. Of course that is just my opinion.

[RossWilliams]

I doubt Ross has a monitor.

Of course I do - four idiot lights over the door. When four are on its either charging or fully charged, when it drops to three lights it is at about 75%, when it gets to 2 lights you are around 50% and should charge the batteries and when one light is left you need to charge the batteries or shut everything off.

Is it accurate? About as accurate as 4 lights can be. As long as it isn't in the sun, on shore power or running anything. Checking voltages, the lights seem to reflect the actual SOC, although I don't know if I have ever checked with one light on. I assume the idiot lights are based on voltages too, so that doesn't prove much.

As for Etrek's, I think a lot of the newer ones with lithium batteries are using some kind of amp-counting battery monitor. Its really the only way to monitor usage for lithiums since their voltage remains relatively flat over most of the discharge cycle.

A battery monitor will certainly be more precise than idiot lights or checking the battery voltage. That doesn't mean the information is more accurate. There are lots of ways they can mislead you and it would pay you to know what they are.

[markopolo]

If you ever get a chance to confirm voltage to amount of indicator lights then post the info here if it's a Kib panel: http://www.classbforum.com/forums/f5...ghts-2295.html

The last info I found a few years ago showed 11.9V or 12.1V was three lights on. That's pretty low. It would be nice to know if it changed in more recent years.

[RossWilliams]

"The last info I found a few years ago showed 11.9V or 12.1V was three lights on"

My SOC chart for AGM's puts 12 volts as 75% discharged. Our batteries have never dropped below 12V in the time we have owned the rig, but we rarely get below three lights either. That doesn't happen until we hit 12.4 volts. Of course, with a solar panel its pretty rare I have ever had a clean voltage reading where the batteries were fully rested for a full day.