Only getting a fraction of battery capacity

[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]

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!

[Bala]

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

[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.

[angelakelly]

Okay, so following up on this, I got a temp corrected hydrometer. It's one of the bulb kinds with a plastic needle that rises to the correct reading. My two batteries are between my seats, so while the forward battery was easy to read, the more inner one required an angle I couldn't quite get, so those readings weren't as reliable.

I wanted to test what Bala suggested- that when the charger goes into float, that doesn't mean a full charge. They were right.

The SG readings across the board were 1.225, which corresponds to a 75% charge. This doesn't surprise me, as I've been charging 5-6 hours with almost 100% cloud cover, though the last hour or two that thinned out and I"ve had some periods of direct sun. This wasn't meant as a rigorous test however. It was meant to practice a little at taking readings. I'll be doing a much more focused testing come Wed when the skies are supposed to be clear. Since Bala mentioned that I could test while charging, I'd like to try to confirm the SG at the various voltages, what it's state of charge is when the system goes into float, and then what it takes to get close to 100% charge. I expect that what I'll find is that those voltages are surface charges, and that the rise in SG doesn't correspond to them in the way I've been thinking of it- and will probably end up better understanding the one sticky that talks about "smoke" charging... basically going full bore as much as one can and using the SG to determine when charging is complete. I don't know, I'm still getting my feet wet on this.

One question. While the charges of each cell seemed to be the same, On one of the batteries, the outer two cells seemed a little lower than the middle four, and those middle four seemed to have climbed up the chamber a little. Is that normal?

[Bala]

The different level of fluid in the cells may just be that they were not the same to start with.

Generally the need to equalize is determined by cell sg being out of balance but as they have been getting undercharged they really need an equalize charge but that will require more panel power than you have.

https://batteryuniversity.com/learn/...alizing_charge

Do you have these batteries connected to the Van alternator? for charge while driving and what type of Van is it? The alternator charge systems can vary a lot from make and model.

[angelakelly]

I don't, no. However that might be a good way around things. I can look up (or test) my alternator specs, np I also have the option of spending a night at a campground once a month that has a hookup. Would just need a decent battery charger.

[Bala]

You should have your car alternator connected to the house batteries so you charge while driving. You can get a lot of charge in a short time.

Depending the the make/model it makes a difference to how the system can be set up. If it is a late model it may have some sort of smart charge type alternator.

It may just need a Voltage sensing relay VSR or it may need a DCDC charger.

I have a late model Ford and it has smart charge so I have a Redarc DCDC charger with solar input.

Big difference in $ depending on what it needed.

[Mike90250]

You need to insure the batteries have not stratified - meaning layers of dense acid sink to bottom, and plain water floats to top. Regular charging bubbles gas through the cell and stirs it up, as would a trip around the block followed by a good day of charge. If you have not been getting enough charge, or driving, the likelyhood of stratified is strong. That does nothing to improve the life of the battery, the bottom of the plates corrode faster because of the strong acid.

[angelakelly]

And if I use that technique where I set all the charging phases for my CCs to max and keep the current going full boar for the day, I might or might not be able to get enough charge to circulate the electrolyte. Sounds like doing as much of the equalizing as I can with what I have might be better than doing nothing until I can afford other means. I've a quick question. I know charging current is C/10, and while I don't know the true 20h capacity for these batteries (They state 101Ah @1A), I figure I'd need 8.5A-10A going in. Is that per battery? Since these are in parallel, it seems like I'd need to treat the two batteries as a single 202Ah battery for charging purposes. Am I right on that? If so, perhaps I can do the equalizing one battery at a time. In good sun, I'm pushing 10-12A with the panels I have.

Thanks to you both for your help.

[Bala]

And if I use that technique where I set all the charging phases for my CCs to max and keep the current going full boar for the day, I might or might not be able to get enough charge to circulate the electrolyte. Sounds like doing as much of the equalizing as I can with what I have might be better than doing nothing until I can afford other means. I've a quick question. I know charging current is C/10, and while I don't know the true 20h capacity for these batteries (They state 101Ah @1A), I figure I'd need 8.5A-10A going in. Is that per battery? Since these are in parallel, it seems like I'd need to treat the two batteries as a single 202Ah battery for charging purposes. Am I right on that? If so, perhaps I can do the equalizing one battery at a time. In good sun, I'm pushing 10-12A with the panels I have.

Thanks to you both for your help.

IMO you are onto it,

I would separate them and give them all that 10 to 12A for as long as they need it. They will get to hot if there is a problem, but I doubt that will happen. Just use your hand on the side to feel temp.

Basically at the moment they are dying on you, the sooner you do something to get them fully charged the better.

[Mike90250]

Do you have a generator to charge them with, or can you start your vehicle and use jumper cables to charge them ?

Generally, you can charge flooded lead acid batteries at very high rates until they are at about 80% full, then you have to throttle back or you will overheat them

[angelakelly]

No generator or jumper cables, but I could (and probably should) get some jumper cables anyway. With the cables, I could let the car idle and use that to charge the batteries up? How would that work? Would I keep it going til the battery started getting hot, etc? I ask though, because according to the SG, even with the clouds I was up at 75percent. We're just really trying to hit it up to get the electrolyte mixed?

[Bala]

For the jumper lead option you need to be above idle.

If your van does not have a high idle function then you will need to sit there or put something on the pedal to keep the rpm at 1000 to 1500.

If it is a late model with a smart charge system the negative needs to go to chassis not battery post.

Some vehicles electronics are not happy about jumper leading. You can get leads with surge protection. But best to check for your vehicle.

Monitor the voltage, the batteries should not get hot as the car system will not charge to high.

If they get hot stop as you have a battery problem.

[angelakelly]

So, the second thing I wanted to test was how well the resting battery V corresponded to the SG. I figured that would give me a clue about how bad the stratification issue is. The voltage behaved like normal. Last night when I went to bed it was at 12.3, and jumped up to 12.4 when I turned off the computer. This morning it was at 12.4 resting. I took a SG and came out with about 1.210, which corresponds to about 65% charge vs 70% as indicated by the voltage. Considering the precision and accuracy of my hydrometer, I'd say that was pretty close.

In this case, the hydrometer is the issue. It's got a series of ticks, each one 25 points from the next. Even if my technique is perfect. I'm estimating the last couple of digits, and such estimations become less reliable beyond the halfway point between the set values. I wish there was a better way to read this? Perhaps with a refractometer? Of course, then, you're dealing with taking a few drops of electrolyte out of the cell each time you do the reading. It's messy and you're depleting fluid. For beer and wine, refractometers are great.

Do you think it's safe to say that I can (within reason) rely on the voltage once it's rested, but when it comes to the charging, I really need the SG? It seems that with my small loads, I'm not impacting the readings very much. The influence of the solar panels, however, is pretty dramatic.