14.8 volt float, batteries still use no h20

landyacht.318 · April 2009

kyc 130 tm
Bluesky 2512i
IPN remote

2 Everstart 27's 230 a/h, 2 years old. This system is on a RV.

Only once in the last 2 years have I had to put h20 in the batteries, and very little at that. I used to have 3 batteries, but one developed a bad cell.

About 6 months ago I raised the float voltage to 14.8 volts to squeeze every amp into the batteries. I also set the float current high (4 amps per 100a/h of battery). By the late afternoon the batteries will not take more than .5 of an amp. A wall charger at this point goes directly into float mode even with the panel disconnected. It will put no more amperage into the batteries than the solar does. The voltage stays at or above 12.8 for an hour after the charge controller clicked off, unless the fridge's compressor is running.

I have to conclude that the batteries are indeed reaching near 100% SOC.

5 months ago I checked the h20 level, no change. Voltage at batteries with a separate voltmeter 14.65. Was able to see tiny bubbles in each cell at this voltage.

The other day bought a gallon of distilled h20 figuring they had to be low by now. No h20 needed.

I'm in a sunny area and my batteries usually go into float before 11:00.

When my one battery developed a bad cell, I went on a tirade about the Everstart's quality, and figured my remaining 2 batteries would also die prematurely. Surprisingly they have seemed not to deteriorate any further in the last 8 months or so. The overnight voltage drop is about the same with the same amp usage, and they always crank the 5.2 liter V8 extremely easily, even first thing in the morning.

None of the RV's systems ( 12/24/120volt compressor fridge, Engine electrical, LED lights, tv seem to be affected by this 14.8 float voltage,
Is the only danger of setting the float too high the boiling dry of the batteries (which does not even seem to be a factor in my case)?

icarus · April 2009

Re: 14.8 volt float, batteries still use no h20

Do you check the specific gravity with a good temperature corrected hydrometer?

T

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

icarus wrote: »

Do you check the specific gravity with a good temperature corrected hydrometer?

T

Cant say that I have, I'm more or less going of the fact that I cannot squeeze any more amps into the batteries to guess that they are reaching near 100% of their remaining capacity.

icarus · April 2009

Re: 14.8 volt float, batteries still use no h20

How did you determine that you had a bad cell if not with a hydrometer?

Hydrometer is a cheap but very accurate battery tool,, I highly recommend having,,, and using one every month or so.

Just "squeezing a few more amps" into a battery may indeed be counter productive. Battery capacity is strictly a matter of battery chemistry. Charging a battery is only done by taking electrical energy, and converting the chemistry in the battery to a more acid state. (In simple terms) The limit to voltage is the concentration of acid (specific gravity). I don't know this for a fact,, but I don't think you can marginally increase the SG of a lead acid battery above it's 1.265 basic chemistry, and therefore increase it's output capacity.

I think that over charging the battery,, even if you are not boiling it dry can degrade the plates and shorten it's life. I suggest that you read the following links if you haven't yet: http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
http://www.batterystuff.com/tutorial_battery.html
http://www.batteryfaq.org/
http://www.rpc.com.au/products/batteries/car-deepcycle/carfaq4.htm#charge

If you read them all you will know more than you ever thought possible about lead acid batteries!

Tony
Tony

mike95490 · April 2009

Re: 14.8 volt float, batteries still use no h20

Now that you have "Filled" the batteries, by squeezing every amp into them, you need to read up about EQUALIZING them. Then they will be full, and need water afterwards. Do you have a charger with EQ function ?

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

icarus wrote: »

How did you determine that you had a bad cell if not with a hydrometer?

I was swapping the batteries around in their locations and found that on one of the batteries, one cell was wet and crusty white around the top. This battery when removed from the parallel read less than 10.5 volts iirc. When I hooked a jumper from the other side of the shunt back to the battery, the monitor showed an~ 8 amp drain.

That battery continued to spew material from that one cell for another few weeks just sitting by itself. Frankly, it scares me to get near it, and I have not for many months now.

My charge controller does not have an equalize function, but monthly I disconnect every possible load and hot fused draw and I set the acceptance and float charging voltage as well as the maximum battery voltage to 16 volts and let it go for 2 hours or so. It easily gets up to 16 volts, 15.77v at the batteries with a DVM.

I can tell that night that the batteries hold their voltage longer.

I started The RV a few hours ago, while it was in float mode with .6 amps going into the batteries. 30 seconds after it started there was .5 amps @ 14.8 volts going into the batteries, with the panel putting out 3.2 amps total. After another 3 minutes (engine running)the battery voltage was fluctuating around the 13.8 mark with .3 amps going to the batteries, the charge controller in float mode, but outputting only .1 amps.

When I turn off the engine with the panel back in the sun, the battery voltage rises back up to 14.8 quickly.

Obviously the batteries are not quality or new or very healthy, but they are getting fully charged to whatever capacity is remaining in them. Unless Wally world batteries are using some sort of water miser re combination cap on them, they should be using h20, and they are not.

Most of the reason I set the float that high is that the controller would not stay in acceptance mode unless I set the Float current at 13.2v and .4 or .5 amps per 100 a/h of batteries. When set at that voltage and current the voltage overnight would drop 0.1 volts lower than the higher float voltage/ current, all other factors being equal.

I'll read the posted links for the info I'm still ignorant of.

I fully expected to have had to replace the batteries by now, but they are still doing their job surprisingly well. They do not seem to have any less capacity than when I removed the third one from the parallel 8 months ago, despite my attempts to boil them dry with a ridiculously high float voltage.

RCinFLA · April 2009

Re: 14.8 volt float, batteries still use no h20

These are lead-calcium plates versus the lead-antimony of the true deep cycle batteries.

Lead-calcium need watering much less then lead-antimony. Lead-calcium also have lower self discharge compared to lead-antimony.

You sound fine. When they get to less then 1 amp at 14.8v bulk they are charged and should be dropped to float level. Too high a float voltage, >13.8v, over time will accelerate plate sheading.

I have 40 of the Maxx 30 batteries for my 48v system in a ten parallel by 4 series arrangement. I had one battery fail after 4 1/2 years with a high leakage cell. I water them once a year but mine are primarily UPS use.

Don't discharge them too deeply (<50% SOC) and they should last for a reasonable time.

niel · April 2009

Re: 14.8 volt float, batteries still use no h20

i think an eq charge is unnecessary as this overcharge by way of a high float charge kind of fulfilled that. put the controller back down to a normal float charge as you aren't really adding more amps, but are raising the voltage of the cells higher than normal. charged cells don't gain any amps and will continue to boil. this is what an eq charge does as it brings low cells equal to the others that are already charged for the low cells will be the only ones getting a charge. you won't need to do this very often and usually only for an hour or 2 when you do this. watch your water levels as these batteries will develope sulphation quickly when the plates are exposed to the air.

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

The problem when I lower the float voltage to 13.2 and the current to .5 amps per 100 a/h of battery is that overnight the voltage drops 0.1 volts more, leading me to believe they are not getting fully charged.

If I raise the float current, it spends no time at all in acceptance. The second it reaches the acceptance voltage, it drops into float.

My fridge compressor kicking on and off I think plays havoc with the Charge controllers brain. It can indicate 8 a/h from full then the fridge kicks off, the voltage soars, and it instantly says 0 amp hours from full, 100% charged. When the fridge kicks back on it can't always stay in high float but needs to go back to bulk.

When I set the float high it keeps the voltage from going on an extreme roller coaster. Varying from 14.8 to 14.3 or so. If I set it low the fridge causes it swing from 13.2 up to a short lived 15.3 and back down to 13.2.

The sound of my ventilation fans continuously changing speeds is annoying.

Maybe quality fresh batteries would hold their voltage better when the 2.7 amp fridge kicks on flattening out the roller coaster, but replacing these batteries now would be a waste as they are still doing their job acceptably well.

icarus · April 2009

Re: 14.8 volt float, batteries still use no h20

Personally, I think you are worried too much about the detail. The CC meter or battery monitor is not equipped to deal with the quick draw down from a compressor starting for example.

I think the only real thing that matters is,, on balance,,, are you getting fully charged every day. Are you putting in roughly the same number of AH/day that you take out. Who cares if the meter shows .1volt lower in the morning every morning,, if it come up to full by the end of the day? Same with the % full number from the meter?

I would set the voltages according to the battery specs and leave alone for a while and see what happens. I suspect that you will find that everything is fine. The fact that toe CC doesn't go to float does not mean that the batteries are not "fully" charged. If you put your battery in float,, put a 5 amp load on it for a mintute,, (1/100 ah if my math is right), the CC will drop out of float,, out or absorb (acceptance, sounds like a BS controller) and go back to bulk. This is not an indication that the settings are incorrect or the battery is defective.

I suspect that you are shortening the life of the battery bank by doing what you have been doing,, because you are worried about absolutely all the ah you can dump in the battery. In that case,, get more batteries or more panels or both next round.

Tony

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

icarus wrote: »

I would set the voltages according to the battery specs and leave alone for a while and see what happens. I suspect that you will find that everything is fine.

Tony

That what I did when the system was newly installed, and with new 3 batteries.
I believe the fact that it was skipping acceptance altogether caused the batteries to prematurely sulfate due to being undercharged despite the monitor claiming to put back into the batteries what I took out nightly.

I've been overvoltaging the 2 batteries for over 8 months now, but with a single 130 watt panel I doubt I've been overcharging them. They use no water. They don't heat up.

Perhaps I am shortening their life by causing premature shedding with such a high float voltage, but maybe continuously undercharging them ( no acceptance stage) might arguably damage them more.

niel · April 2009

Re: 14.8 volt float, batteries still use no h20

for a float voltage you could go to 13.5v or 13.6v, but you are doing your batteries no good in overcharging them. heavy loads coming on will drop the voltage every time and if it bothers you with the flickering on the lights more batteries and pvs will help, but some drop will occur regardless. your alternative would be to regulate the voltage lower to the lights if they're dc. if ac you're somewhat stuck with a drop.

icarus · April 2009

Re: 14.8 volt float, batteries still use no h20

One of the things that you haven't mentioned,, (or I overlooked!) is what is your daily average usage? Is this a off grid situation that you use 24/7 or an RV that you use on the weekends etc? How much do you routinely draw them down? Do they get fully charge on a daily basis?

Looking at the walmart site,, I can't get a lot of information about everstart batteries, except that they are made by Johnson Controls. From what I have been able to read, they don't seem to have a stellar reputation for longevity. (Like a lot of Walmart stuff IMHO!)

Tony

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

"what is your daily average usage?"

14 to 22 a/h overnight, every night. 100% off grid although I do have access to the grid. Last night was an exception where I used 44 a/h by running the laptop for 7 hours. I reached float mode around 3 pm today, tilting the panel around 2 pm. It has to be a really heavily overcast day for my batteries not to reach a claimed 100% daily.

Though the 2 batteries claim to have 115a/h each, I have the a/h set in my monitor at 200 a/h total capacity.

I cannot notice my DC LED lighting dimming with the compressor fridge cycling during the day. I rarely ever use them in the day anyway, they might even be regulated. They do not fluctuate at night with the 0.2v drop the cycling fridge usually induces. It is the sound of my exhaust and intake DC fans that I find annoying as they fluctuate with the compressor cycling during strong sunlight situations when they are set to max speed

When I do wind up replacing these 2 questionable quality Everstarts, I will definitely lower the float voltage and current.

I do have room for 3 group 27 or if the dimensions on the Crown deepcycle PDF are accurate, 3 group 31's, but I think I do not have enough panel to meet the minimum charge requirements of 3 paralleled 140 a/h batteries.

And judging by my usage I do not need any more panel, 98% of the time.

I do appreciate the input to my original question of if I am damaging my batteries by setting the float so high, the consensus being that It could speed up the plate shedding even if I am not using any water and that I'm not really squeezing any more amps into them even if I think I am.

My real issue is that my controller will not stay in acceptance unless I lower the float current to a very low level, and then I notice that my overnight voltage drops .1 volt lower, leading me to believe they are not being fully charged with that lower float voltage and current.
So I crank everything up and let the batteries decide how much they can take. As far as I can tell they are as happy as an old , sulphated, low quality, quasi deep cycle , regularly used battery can be.

In fact I am going to blame the batteries themselves for the acceptance skipping dilemma, logical or not.

icarus · April 2009

Re: 14.8 volt float, batteries still use no h20

With a battery of that size,, I don't think that you will be able to avoid having the fans change pitch as the voltage drops or rises a bit with the fridge. I don't know what you are using these fans for,, but I have had success with my LP fridge by using 24vdc fans on the condenser. The 12vdc fans that I used to use made just enough to bother me. The 24 vdc fans move enough air to cool the condenser,, but make almost no noise at all. (These are computer muffin fans).

Question is,,, do you have 2-230ah batteries,, or 2 115ah batteries making 230ah. In the former you should have ~ 25 amps of solar panel MINIMUM,, to be in the suggested charging range for a wet cell battery. In the latter,, you would need ~12 amps. Your 135 watts will yield ~9 amps,,, a little little light for the latter example,, very light in the former.

20 ah/day is ~ 8% of battery capacity if 230 ah,, ~4% if 460. If these are essentially T-105 size (golf cart) a pair of them should last forever in your usage, so the fact that you have some failures in two years speaks to either crappy batteries, or not so good battery management. (No offense intended) I have one set of 225 ah trojans that are on year 11 using ~20 ah/day for the first 8 years. Now they are on stand by service powering a fridge ignitor and the occasional light now and again.

Tony

landyacht.318 · April 2009

Re: 14.8 volt float, batteries still use no h20

Tony,

2 115 a/h batteries.

The fans:

http://www.newegg.com/Product/Product.aspx?Item=N82E16811999344

They are variable speed/ sound. Up to 110 cfm. I use one as a shady side air intake, and one for roof exhaust. They are able to keep the RV at or below ambient temps on all but the hottest late afternoons. I've tried a lot of different makes and models of this style of fan. They vary greatly in how much air they move for current consumed and decibels produced. The silverstones move the most air for the least juice, and have a variable speed control. The lower speed settings also consume less current as hoped. By far the best Muffin Fan out there.

I also have a 24 volt fan under the coils on the fridge, running very quietly 24/7 at half the design speed. A 1 inch 12 volt muffin fan runs 24/7 inside the fridge. Both of these fans reduce the interior temp and the duty cycle of the fridge significantly.

My noise complaint about the fans is when I have the float voltage and current set low and the fans at 3/4 speed or faster.

Scenario. Fridge off. 13.2 float volts, fridge turns on. voltage drops at first to 12.9 then CC cranks up the amps till the acceptance voltage reaches 14.4 or.8 it then quickly drops back down to 13.2. When the Fridge turns off, the voltage quickly rises to well over 15 while the cc figures out how much to restrict the current, then quickly drops back down to 13.2.
So for a few hours the voltage is going from 12.9 to over 15 over and over with the fans speeding up and slowing down. More than a little nerve racking while reading on my day off.

If I set the acceptance and float at 14.8 the voltage only fluctuates from 14.9 to 13.8 and only half as often and not as quickly.

Guess I could put a voltage limiter on the fan's circuits, But frankly when it's real hot outside, I notice and appreciate the extra CFM the higher average voltage induces.

I know I've got more battery now than panel, and maybe that's why it seems to me that my 2 parallel batteries seem to be degrading less quickly than when I had 3 in parallel, But that one battery could have had a shorted cell for 4 months before I realized it.

I really liked having 345 a/h of batteries when boondocking on a beach in Baja, but never needed that much capacity. Now due to the proliferation of thieving meth addicts down there I no longer travel to Baja and have even less need of that much capacity.

A third battery is able to be isolated, but unless I was expecting days of clouds, it never got isolated. Now in my engine compartment where that battery goes is an empty shelf. And now I'm trying to decide weather or not to buy 3 new batteries, or just 2 when I need to.

I do not have the height requirement for 6 volt batteries, and when I first bought and set up the system I was unaware of the minimum charging current requirements for large battery banks. I thought you just had to replace the amps used. I was more concerned the panel could keep up with the demands of a 2.7 amp fridge so I went a little overboard adding extra insulation and hyperventilating the cooling fins trying to keep the duty cycle to a minimum. From 1 am last night to 10 am this morning the whole RV used 4 a/h. Granted it was a cool evening, but still I'm impressed with the duty cycle.

Anyway thanks again for the responses.

Kamala · May 2009

Re: 14.8 volt float, batteries still use no h20

icarus wrote: »

From what I have been able to read, they don't seem to have a stellar reputation for longevity. (Like a lot of Walmart stuff IMHO!)

Tony,
How far away is your nearest Wal-Mart? Can't see you as a regular shopper. :roll:

Craig

icarus · May 2009

Re: 14.8 volt float, batteries still use no h20

Craig,

For a variety of reasons,, I am not only not a regular customer,, I am not a customer at all. As it turns out,, there is a Walmart in the nearest city,, 150 km away. We make it to town about once a month.

Tony

hillbilly · May 2009

Careful what you read on amp meters...

Just to reiterate what Tony said about batteries being charged as a chemical reaction. I think you are obsessing way too much on what your amp meter is reading. Be very careful on that end as they can get you into some trouble if you take them too literally. They can be handy as a really rough guide as to how deeply you've discharged a battery, and very roughly how many hours of charging they may need to get close to a full state of charge. I think once you've spent some time monitoring your batteries, those amp hour readings become more and more irrelevant. Also I would repeat Tony's other key piece of advice on this matter: get a GOOD hydrometer (no cheapo thing with colored balls or dials), as they are really your most accurate way to measure the state of charge on your batteries .
Good Luck

14.8 volt float, batteries still use no h20

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