Only getting a fraction of battery capacity

[Mike90250]

The standard specific gravity should be assumed, unless you are in a tropical area, or a frozen area, where the SG is adjusted to provide longer battery lifetime, but variation in capacity. You would should have been notified when you bought the batteries if they had a non-standard fill.

[Bala]

I would just use the standard sg figures from battery university site. It will get you close enough if not spot on.

[angelakelly]

Thanks for that. I read up some at Battery University from one of the links Bala gave me, and I see what you both are saying about trying to use voltage. I'm going to get a temp adjusted hydrometer tomorrow and try to get a better handle on just how much the battery is being charged. Also read that sticky on how to use a charge controller to essentailly go full bore to try to get as much charge as possible into the battery.

One thing I haven't found yet is the SG for the batteries I have when they're at full charge. The article at battery university lists the standard, but different manufactures alter that at times, and I can't find any real technical detail on my walmart batteries. Do you know offhand if there's a way to determine that experimentally? I.E. wait till I see bubbling and when all cells show the same SG reading, then that reading is the max?

I'll get a handle on this! I'm already actually seeing how the charging issue would match my numbers. Usage=solar input + about 30 percent when I track my numbers via voltage, but if I'm only getting 80 percent charged, or its varying, that could cause me to hit the 50 percent range much earlier than I expect. Add this to the issues of reading voltage as an SOC indicator, and my problem actually fits within that.

Thanks for the help and the suggestions!

[Mike90250]

You cannot rely on voltage to determine state of charge. You can have one cell in a battery be lower or higher than the others, which throws off the voltage reading.

Charging, you need to replace at least 120% of what you took out the day before, and if you have any daytime loads, those reduce the power going into the battery.

For flooded cells, increase the Absorb time to at least 4 hours, and see if after a couple days, they are holding a charge better. If this has been going on for more than a week, you may have already damaged the batteries by allowing them to sulfate, and the general cure is to buy new batteries. Study the Battery University pages a lot, gobs of good info there

[angelakelly]

Awesome, I'll do that, and thank you both for all your help. I appreciate you taking the time to work with me.

[Bala]

The hydrometer needs to measure SG, Specific gravity. The reading will vary depending on what the manufacturer did, SOC and temp.

You are looking for each cell to be the same.

SG will tell you SOC at any time, no need to rest batteries. it can be done while charging.

Have a read of this for what to expect for SG and its relationship to temp.

https://batteryuniversity.com/learn/...tate_of_charge

[angelakelly]

Alright, I'll take that advice. It has seemed to me as well that 2-3 hours of charging doesn't make sense with the two batteries I have and as low as the voltage went. In fact, that's part of why I'm posting here, the numbers I have no matter how many ways I've verified just do not fit logic. It make sense to go back to the beginning and find a more reliable way to check charge and see if the batteries are getting fully charged. Can always pick this back up later if needed.

Just to to clarify, I"m checking each of the cells to make sure that the pH indicates a 14.7 charge at the end and also checking that the batteries will hold that charge overnight, wouldn't the charge have dropped overnight to the resting 12.7 volts?

[Bala]

For hydrometer use, glasses at least, face mask, gloves, whatever makes you feel safe. Just be careful and precise when doing it and you should have no problem. if you get acid on you water is your friend. if you get it on your clothes they will get holes in them.

I have used a saying for many years in that, " You can theorize till the cows come home and still be wrong"

I have not tried to work your math.

From what you have posted I just see a unknown start point, you dont know if the batteries are actually getting fully charged. Because of the size of battery and the amount of panel wattage you have and as little as 3 sun hrs I doubt they are.

You need a mains charger and give them an equalize charge separately and ensure they are actually fully charged and in good condition via hydrometer readings.

[angelakelly]

You know, you may have something there. I had noticed in the horrible manual for the chargers that it will go into float after a certain amount of time has elapsed beyond getting up to 14.1V, and I had one experience when this was verified. One of my panels had come loose about halfway through that hour or two that it took to go from 14.1 to float, and the one that had come loos and been reconnected didn't to go float four about half an hour after the other. And thinking about things, while I haven't noticed a really low charge starting out, there could be enough of a charge on the batteries that I simply don't notice that it goes from 12.9 to 12.7 to 12.4 much more quickly than it should.

I'm a little intimidated at the idea of taking a hydrometer reading. I have a hydrometer from brewing, but...eh, it's acid and all that.

Let me ask you this though, if not getting fully charged is the issue, wouldn't my recharge be a good deal less than discharge? After all, there would be more juice going out than was coming in, and eventually, the battery simply wouldn't have a charge at all. Every time I compare, my charge in comes out to about 30% more than the charge that went out the night before.

[Bala]

How long has this set up been in use??

Going into float is not full charge, it may be 95% but it depends on the charge controller.

You are using budget batteries and controller so as I suggested I would be looking to get a hydrometer and get them to a known full charge and go from there.

I have a folding panel I use for camping, its controller does not do bulk well.

The hydrometer will also tell you if you have a bad cell or uneven cells.

Also disconnect the two batteries after charge and see if they hold the same V overnight.

Sunking has suggested for years that battery manufacturers have gone away from multistage charge profiles to what he has, or is, termed max smoke. I think there is a sticky on it.

I put new batteries in last yeas and a new controller. The new controller hardly ever goes into float, it just holds absorb unless they are very very charged.

[angelakelly]

I was wondering about that as well- that perhaps the controllers switching to float doesn't imply what I think it does (ie that the batteries are fully charged). I tested that one time. I let it go to float, I then let the batteries rest for six hours and looked at the voltage. It read 12.7V, which is exactly what it should have. I also just looked at the controller, having only now started my nighttime computer use. It also reads 12.7. If it wasn't getting charged, I would expect the voltage to be lower in both cases.Also, when I compare usage from one night with how much charge goes in during the charging cycle, they're within reason. about 10Ah going out, about 12-15Ah going in.

If I'd been using the laptop half an hour or so and looked and saw 12.3V, then yeah, I'd be inclined to think that they hadn't fully charged, but that hasn't yet been the case.

[Bala]

I suggest that are just not getting enough charge.

I would be trying to keep the charge V at over 14 all day and move the panels to chase the sun to get as much charge time as possible.

When you take a cap off they should be bubbling and as long they they dont get hot they will be fine.

Ideally they need a mains charger and a hydrometer to get them to known full charge.

[angelakelly]

If your batteries are as the photo looks when I google them you should be able to use a hydrometer to check for SOC.

It is quite possible they are not getting properly charged.

What Voltages do the regulators charge to?

What time of day do they go into float?

How many hrs a day of good strong sun do the panels get?

Are you using power from the batteries while they are charging?

1. The regulators have (supposedly) four stages-though I've observed three. The bulk charge, which is at full Amperage. The controllers will keep pushing the voltage up to 14.2, which is where it will stay for an hour or so until it goes into float charging. Over time at 14.2, the current tapers off until by the time it goes to float, it's about 1.0A or so of current going in. Upon switching to Float, it will drop down to 13.7

2. I don't always charge them the same time during the day, It will take from 2.5-4.5 hours to switch to float charge.

3. At least three hours of good sunlight, generally. Most often 5-6, but I seldom need that long.

4. Generally no, and certainly I did not when I was doing my tests. I tracked both usage and how much was put back over a series of a few days to get at my numbers. During that time specifically, I was careful not to do anything that would convoluate the numers, so the usage, for example, was read at the end of day, and then reset the next day for the charging sequence, and that sequence was only begun once the sun was high enough in the sky to give a decent charge rate. No other devices at all were drawing during those times, save for the controllers and the monitor.

[Bala]

If your batteries are as the photo looks when I google them you should be able to use a hydrometer to check for SOC.

It is quite possible they are not getting properly charged.

What Voltages do the regulators charge to?

What time of day do they go into float?

How many hrs a day of good strong sun do the panels get?

Are you using power from the batteries while they are charging?

[angelakelly]

I appreciate you doing that and your replies. It's kind of you to look the battery up. The website doesn't list the capacity, but it prints the numbers on the battery 101 Ah @1a. I'd put this information in the _specs_ section of my post. I found out after the fact that that @1A is a little marketing ploy (though I typically only draw 1.5A give or take), and the real Amp Hour rating @20H tends to be around 85Ah. That's these batteries in a nutshell; I wish I'd seen the Sam's Club ones, as I'd have much more faith in the posted rating.

Even worst case though, the batteries being 85Ah, I've got two of them in parallel, and I'm only getting 10-12Ah before I'm nearing the 50% discharge.

If I were to take the actual usage, say about 12Ah before I get down to 50 percent, that means I really only have 12Ah batteries and that just doesn't make sense. It's why I think I'm missing something big conceptually. I'm just not sure what.