Battery Life

[Gary_C]

I have been living on my job site in my camper this winter. I have four 6 volt batterys (Trojan T 125's) hooked up in a two bank 12 volt system feeding an inverter. I had replaced all four batterys a year ago January because of a faulty cable connection that caused the batterys to be undercharged and frozen. But back in December when it was really cold, I could not get but 80 amp hours out of the batterys before the controller shut down on low voltage. And when I checked the water levels, there were ice crystals in some of the cells but only at below zero temps.

So at the dealers request I brought the batterys back and he gave them a full charge and I tried them again and still only 80 some amps to discharge levels. So he replaced them and the new ones, don't know the brand but they are white with red tops. and these will put out 180+ amp hours to discharge. But after just about three months of operation, they seem to have dropped to just over 100 amp hours capacity. At the cost of these dang things, this is going to get expensive to replace these things at least every year.

And I do have a Zantrex 2500 watt inverter with a Hart interface/controller that controls the entire charge/discharge cycle. And I also have two 50 watt solar panels and they will charge as much as 7.8 amps in strong sunlight, but that is not in the winter. It was hard to keep them clean of snow and the sun was too low and mostly behind the trees for them to work much in the winter.

Here is a picture of the control setup.

 



So what kind of life are any of you other off grid people seeing from your battery banks and what kind of batterys are you using?

[doctorb]

I am not off-grid, but I am also disappointed in the battery life I am getting from new 6-volt deep cycle batteries.  We use them in 60 or 72 volt systems for "electric" fishing on our reservoirs, which do not permit gas engines.  We used to get 3-4 years out of a set, and used to have very prolonged run times if you didn't crank it wide open all the time. 

Now, I get 2 seasons max, and my daily run time is decreased.  I have not changed any of the equipement on the boat, and use the same routine for maintenance as I did before.  I can't explain it except to say that they don't seem to build them like they used to.

[John Mc]

How low are you letting the charge get in the batteries? My neighbors have an off grid solar house and are very careful never to let the battery bank drop below 50% state of charge. Generally, they like to not even get it that low. The deeper you cycle lead-acid batteries, the shorter their life.

Also, leaving a battery in a partially discharged state is not good for longevity. If you discharge it, you want to charge it back up as soon as possible.

You may also want to look at a charger that has a "desulferator". Batteries tend to build up "sulfation" over time, which diminishes capacity. You can reverse this, to some extent with the appropriate type of recharger. Doing this as periodic maintenance can help, since if you let it go too far, it can be hard to bring the battery back.

[Gary_C]

That Hart interface completely controls the amount of discharge and will shutdown the inverter at a set voltage level. I can't remember the setting, but I think it is either 10.0 or 10.2 volts which allows use of some percent of capacity. Discharging below that level will shorten the battery life. But I never do that because it automatically dumps the load at the set level.

I was reading on a battery dealers (in Alaska) web site last night and they say that batteries work best at 68 deg F so that is one problem. My battery compartment is in an unheated and ventilated space so this winter those batteries were forced to operat at outside temps of up to 32 below zero at night this winter. On those very cold nights I left the generator run all night but even the generator would be running rough by morning cause the carb iced up in the extreme cold. I may have to find some battery heaters that are supposedly available. I hate to enclose the battery compartment because of the presence of hydrogen gas from the charging.

[wdncno]

We have been using used forklift batteries. Very heavy, but a lot of capacity even when  they will no longer support the 300-500 amp draw of a fork lift.  Also can sometimes be purchased for scrap price.  We got about 5 years of continuous service out of the last set.  That was running a small house and chargering with a generator.

[Dean186]

That Hart interface completely controls the amount of discharge and will shutdown the inverter at a set voltage level. I can't remember the setting, but I think it is either 10.0 or 10.2 volts which allows use of some percent of capacity. Discharging below that level will shorten the battery life. But I never do that because it automatically dumps the load at the set level.

Gary,  

With four Trojan T-125s connected as a 12 volt system, you would have a maximum capacity of 480 amp hours.   Ideally the battery bank should be discharged only to about 60 percent of their capacity, which would be a voltage reading of 12.2 volts.  The voltage reading of 10.0 volts is almost fully discharged and is much to low.  The set point should be no lower than 12.0 volts.  The Trojan T-125s are one of the best deep cycle camper batteries out there IMHO, and they should last about 10 years in a camper.

Since you say you don't remember the exact set point, it most likely is 12.0 or 12.2 volts.  How are you measuring the 80 amp hours of usage?  With a set point of 12.2 volts, one should get a usable 40% of the total 480 amps or 192 amp hours.  This would be a maximum number with new batteries and 100% charge, which can be a challenge.  Real camping numbers would look more like ((90%x480) x 40%) = 172 amp hours of storage capacity.

Hope this makes sense and is of some use.  

Dean

[Dean186]

So what kind of life are any of you other off grid people seeing from your battery banks and what kind of batterys are you using?

Gary,  I thought I would also answer your question more directly, since you mentioned your installation was in a camper.  I have two Trojan T-125 in my camper charged by 160 watts of solar.  I am on my fourth year with this setup and they still perform like new.  I expect them to last several more years.

John Mc makes a good point about battery sulfation.  Sulfation of batteries starts when the voltage drops below 12.2 volts for a 12 volt lead acid battery system. Sulfation hardens on the battery plates reducing and eventually destroys the batteries ability to generate power.   This is why I try to never let my batteries drop below 12.2 volts.

Some chargers have a de-sulfation charge option, which is a controlled overcharge.  The de-sulfation charge can help considerably in some cases.  It is an option that I have on my camper charging system.  Make sure to read the chargers manual before doing the de-sulfation charge.  The important points are the amount of time one should leave the batteries in this state of charge, and to top off water levels before and after charging.

[John Mc]

Some chargers have a de-sulfation charge option, which is a controlled overcharge.

I thought that was known as an "equalization charge". The chargers I've seen that do de-sulfation use a "pulse" technology...

But I have to admit, I have little direct experience with this... just some reading, an dmuch of that was a couple of years ago.

[Gary_C]

Sorry I have not responded sooner, but I was back to work. While I was there, I reviewed the Heart Interface which is the lower black unit in the picture I posted earlier.

According to the instructions. the Heart Interface or Link 1000 controller will shut down the inverter at 10.5 volts. That is supposed to be at 50 % discharge. And it does have an equalize function though I have not used it because I do not have a good way to disconnect all 12 loads to protect them from the high voltages generated during equalizing.

The SEL button allows you to cycle thru four readings. In the picture it is in sleep mode. It shows volts, amps + or -, amp-hours, and time remaining.

With four Trojan T-125s connected as a 12 volt system, you would have a maximum capacity of 480 amp hours.   

 Real camping numbers would look more like ((90%x480) x 40%) = 172 amp hours of storage capacity.

I do remember that 480 amp-hours as the maximum capacity and I think you are right that around 180 is a normal capacity. But those Trojan T-125's were only putting out 80 amp-hours to 10.5 volts. And the new US Battery's are normally running over 125 amp-hours to 10.5 volts. And now that has seems to be dropping to closer to 100 amp-hours. And that has been thru the winter when temps were below freezing just about all the time and a few nights down to -30 F. And with the warmer temps and the furnace running less, it seems like it should be better but it's not.

I found a good web page with some battery ratings.     6 Volt Golf Cart Battery: The Top Six


According to that, the Trojan T-105 will give you more cycles but at a slightly lower rating.

It has been a real learning experience this winter living off the grid. I am just thankful that I bought that Honda EU 3000i generator. It has worked flawlessly all winter. Starts instantly and runs great. There was only a couple of nights when it was around -30 F that I had trouble with the carb intake icing up and I had to wrestle the generator inside and unfreeze the carb intake.

I did learn that an electric blanket will work fine on a generator but not at all on an inverter. I don't know why.

[Dean186]

Some chargers have a de-sulfation charge option, which is a controlled overcharge.

I thought that was known as an "equalization charge". The chargers I've seen that do de-sulfation use a "pulse" technology...

But I have to admit, I have little direct experience with this... just some reading, an dmuch of that was a couple of years ago.

John Mc,  You are right; the equalization charge is essentially a controlled over charge and not de-sulfation.   Desulfation uses high frequency electronic pulses.

My MPPT solar controller in my camper provides an equalization charge and not a sulfation option.

Both equalization and desulfation can prove beneficial for flooded/wet cell batteries.   One should not equalize gel or AGM batteries.

[Dean186]

Gary_C,

Charts for battery voltage and how it relates to percent charge can be found on the internet.  Charts on the Trojan website shows 60 percent charge is a voltage reading of 12.24 volts on a 12 volt system.  A battery voltage of 11.51 is 10 percent charge.  

The life of a battery will be significantly reduced when it is discharged to below 50 percent on a regular bases and a 10.2 volt reading is fully discharged.   To me, this explains why the camper batteries aren't lasting very long.

Another thing to consider is; the amp hour rating quoted in the manuals is for warmer temperatures, if I remember correctly it is a 80 degree temperatures rating.  The rating will be less with colder temperatures.  You quoted -30 degrees temperatures - yikes that is cold camping weather.

On the electric blanket, when you say doesn't work, do you mean, there isn't enough amp hours left in the batteries, or it just doesn't function.  If it doesn't function, it could be that it doesn't like anything but a pure sine wave inverter, or at least a good modified sine wave inverter.

Stay warm,  Dean

[Gary_C]

I did just look at that handbook for the Link 1000 controller and thought the 10.5 was right. But now I am not so sure and cant find the manual on line. Perhaps it was 11.5 volts. I will check for sure later this week when I am back there, but of course I have no internet service up there so it may take a while to get back with the right settings.

On the electric blanket, when you try to run it on the inverter it will just buzz and no heat to the blanket. If you leave it on for some time, the control gets warm. It must be the circuits in the controller don't like the wave form of the inverter. And I have an almost new Xantrex 458 inverter that is rated at 3000 watts. It runs the TV, microwave, and other electronic things just fine, but not an electric blanket.

[Ianab]

Re the Electric blanket, sounds like you need an "old school" one with just a simple switch, not an electronic controller?

Ian

[mad murdock]

Gary C, I do not use batteries off grid, but I do know a bit about battery construction, and what factors effect battery service life, etc.  As has been aptly stated, close monitoring of discharge state, and not letting batteries get below a certain level will have a great effect on what usable life one gets out of a battery.  Another thing is battery construction itself.  I am speaking from my experience with 25+ years of aviation maintenance and operation background here.  The best batteries (as far as capacity, discharge/recharge cycle life, and overall performance have plate material that is very pure, and the real expensive batteries will have plates made from solid lead plates, rather than the lead powder pressed plates, with the mesh composite construction.  The solid plates are less susceptible to sulfidation issues, and have a much higher cycle life, the downside is that these type of batteries typically are quite expensive to build, and to buy.  This may or may not be of help to you.  The heavy industrial type batteries make excellent choices for aux. or off grid power systems.  In my area, if a guy can find the telecom batteries that the phone companies discard usually every 2 years, are good to build a system around, as the cells are HUGE, and you can string whatever you want for your system in 1 cell (2 volt) increments.  One of those cells (2 volts) weighs about 40 lbs, they have a ton of capacity, and good cycle life.

[Gary_C]

That's interesting. I may try to find some of those 2 Volt batteries.

[DarkBlack]

Some chargers have a de-sulfation charge option, which is a controlled overcharge.

I thought that was known as an "equalization charge". The chargers I've seen that do de-sulfation use a "pulse" technology...

But I have to admit, I have little direct experience with this... just some reading, an dmuch of that was a couple of years ago.

John Mc,  You are right; the equalization charge is essentially a controlled over charge and not de-sulfation.   Desulfation uses high frequency electronic pulses.

My MPPT solar controller in my camper provides an equalization charge and not a sulfation option.

Both equalization and desulfation can prove beneficial for flooded/wet cell batteries.   One should not equalize gel or AGM batteries.

Hey Dean there you go again Why do you keep posting as an expert when you obviously are not? Anyone can come back a day later after reading it on the net and then copy and paste it as if they knew it all along. I just don't see why you would want to do it. I mean really why?? If you really don't know something that's OK, you don't have to make it up. You tried to get me into a debate on another post where I already knew you didn't know what you were copying and pasting, That's why I didn't bother to debate with you.

[beenthere]

DB
How about if we just hear your opinion and let it go at that? 

[DarkBlack]

DB
How about if we just hear your opinion and let it go at that? 

You just got my opinion. I think posters should state opinions as opinions, and facts as facts... if they are.
Actually pretty simple.

[doctorb]

DB-

Since your interested in opinons as opinions and facts as facts, I would calmly, respectfully like to say that my opinion is that you seem to miss some of the worth of the Forum, as reflected in your posts.  It's not my Forum, but I can tell you that when bravado and arrogance overwhelm someone's opinion, that opinion is diminished in value, regardless of whether you are right or you are wrong.  This is not a sniping contest.  Disagree and respectfully converse about your differing thoughts, if you like.  Posts like the above, with attacks and criticisms, not about the post, but about the poster, are not educational, informative, or helpful.  They run counter to the manner in which ideas have been respectfully exchanged on the FF, IMO.  I do think that you have chosen an excellent screen name for yourself.  How about a little sunshine?  We would love to have you add to the conversation, without detracting from it.   Certainly, many of your former posts were contributory.  I'd like to continue along that line.  Just my opinion.  Doctorb

[Jeff]

I'd step in and say something but doctorb said it better than I would have.