Life of Lead Acid Batteries

Post anything about batteries here. Lead acid, rechargeable, whatever.
Dave Thacker
Posts: 62
Joined: Tue Apr 16, 2013 8:18 pm
Location: Tipp City, Ohio

Life of Lead Acid Batteries

Post by Dave Thacker » Tue Apr 16, 2013 9:58 pm

Troy,

I'm a battery and charging professional, I live in the Radio Control world and own Radical RC. I've got quite a bit of experience with batteries and thought perhaps I could help you and your readers over some common issues with 12V lead acid batteries used with inverters and other off grid purposes. This information is provided in general rule of thumb format. So, let us begin....

An important concept to remember about lead acid batteries is their life is shortened in direct per-portion to how deeply they are discharged and how long they are left discharged. Conversely, the greater a percentage of the time they are full, the longer they last. Every minute they are not 100% full, they are sulfating. The more discharged they are, the faster this occurs. If you want to get maximum life out of them, you want a very large bank so your typical discharge (over night or cloudy day) is something small like 10 to 15% maximum of the total capacity. The less percentage of discharge the better. In the morning, you want to fill them quickly so they are essentially full all day (full the maximum amount of time over their life). From a replacement battery cost and reliability sense, over time, it's going to be cheaper to own excess solar panel so you can punch them up quickly and hold them full all day.

The idea of having enough battery to get through the night, essentially running them down 1/2 way or more every night will mean you'll be replacing them on a rapid schedule. This will be very expensive. I think those cells your using are about 70 amp hours @6V each. With 4 of them, your probably sporting about 3360 watt hours (280amp hours) of battery. So, I'm guessing on a fridge with your other loads, they would degrade about 50% in performance (storage capacity) every month or so.

I've owned two houseboats and it is important for them to run off the grid for days at a time. The last boat, I had a 2000 watt inverter and 4 8D truck batteries. These were anomony type cells (have to service with water periodically) and are great for this purpose. Having an account with a battery distributor, I was able to obtain them all brand new as blemished batteries for about $80 each. A great bargain considering they are about 200 amp hour @ 12v each. So, I had about 800 amp hour of capacity or about 9600 watt hours of energy available. 8D truck batteries are large and intended to survive while slowly discharging in a slowly idling diesel tractor all night for many many nights.

Obviously I had lots of small incidental loads to service just like you, Laptops, cell phones, camera charging, occasionally a friend with a CPAP machine and etc...

Some interesting facts and examples. Your inverter is multiplying the 12v DC to 110V AC. To increase the voltage, the amps drawn must be multiplied by an equal amount. So, if we want to multiply the voltage by 10, it will take 10x as many amps at 12v as we are demanding at 110v. Simply, 1 amp 110v appliance running on an inverter will draw about 10 amps (10 x 1amp) from the 12v battery. So, simple low wattage/low current things like cell phone chargers are fine, heavy duty things like hair dryers, electric heaters and microwaves will draw much much more. Many 110v appliances have a label that tells you the watts but not the amps. If you know the 110v watts, a simple way to figure it is divide the watts by the 12volts of the battery to arrive at how many amps this costs are 12v. Example: 1500 watt heater to warm a bathroom. If you divide 12v into 1500watts, you get a 125amp load on your battery. Yikes! Most appliances with heating elements will be about 1500 watts. So, an RV Fridge running on 110v, hair dryer, larger microwaves, electric coffee pots and such. 125amp load is HUGE on your 12v battery bank. Putting a load like that on your battery bank for 15 minutes (1/4 hour) will liberate 1/4 of 125 amps or about 31 amp-hours out of your bank. So, if you want to make a pot of coffee, and don't want to use more than 10% of your bank, you need a bank of at least 310 amp hours in size. AND you have to start with the bank full, AND you need to be able to recharge that bank with your energy source in as short a time as possible.

My main concern on the boat was being able to run the refrigerator 24 hours and not listen to a generator all day and to have the convenience of incidental 110v for toys like phones and cameras. It's also nice to run a drill or circular saw once in a while. Always a project underway on a houseboat. The off grid camper has a very similar problem, wanting to run a fridge and incidentals on limited solar input. With my system, I ran the generator only when we ran large loads like coffee pot or baking potatoes in the microwave. The boat could successfully run for a week with only 1 to 2 hours of generator time per day. And, I never took much out of the battery bank.

I looked up a similar fridge to what I had, about 10 cu ft like Sanyo model SR-1031W/S. If you click the downloads tab and load up the image of the Energy Guide, you'll see it uses 350 kw per year. A KW Hour is 1000 watts for one hour. So, in one year, this unit will consume 350,000 watt hours or 350 Kilo Watt Hours. In reality, the boat and the off grid camper are not air conditioned in the summer, the Energy Guide rating is probably assuming it's installed in an air conditioned space. So, energy use will be higher in summer, probably lower in winter. To keep it real simple, lets say energy use is 365kw hours in the real world. 1000 watts per day or 1kw per day. That means it will take at least 250 watts of panels 4 hours per day at full tilt to replenish what this unit used from the battery bank. 1000 watts divided by 12v means it will use about 84 amps out of our battery bank each day or 3.5 amps (84/24hrs) of that bank on average each hour. So, there we go, in 12 hours of darkness the bank will be drained by 12 hours x 3.5 amps or about 42 amps. If you only want to pull 10% off your bank overnight, it needs to be at least 420 amp hours in size just to service this refrigerator. AND, that's not considering other loads like a 12v mini fan to sleep under and the ipod you left plugged in and all the other incidentals. I installed mine in a wooden cabinet and it was lined with foam insulation. I unbolted the evaporator coil on the back and put a layer of Reflextix on the back. Pennys spent here meant less generator run time and longer battery bank life.

Using the above logic and understanding of how things work leads you to using a very large battery bank, My batteries lasted at least shelf life, I never replaced them in 8 years. Pretty shortly, this becomes the least expensive way to get the job done.

I get the feeling from watching your video's that your slowly arriving at similar conclusions and others may be aware of the shortcomings of the current setup. I noticed the gift of two new golf cart batteries. I'm sure they will go a long way towards sizing up your very undersized system. Your probably only 1/3 to 1/4 of the way there to the right battery bank size. This simple guide is intentionally using simple easy to remember rules of thumb. You can calculate this stuff with greater precision and also consider other things. For example, you probably lose about 5% of the energy in the conversion to 110v, and there are losses when charging, so 50 amps input to the battery won't quite get 50 amps in. However, all this precision is not required to get a good reliable setup going.

Dave Thacker
My blog site: http://www.radicalrc.com/blog

PS, Sharp readers will have noticed I mentioned running a circular saw on my 2000 watt inverter. This is a huge load like a hair dryer, microwave or coffee pot. However, it only takes seconds to zip the end off a board. So, the overall drain on the system is not large. It's the long running big loads that eat up your energy and workout your battery bank.
Dave Thacker
Radicalrc.com, Owner
Radicalrc.com/blog Blogsite

techman
Site Admin
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Joined: Thu Dec 22, 2011 11:49 am

Re: Life of Lead Acid Batteries

Post by techman » Thu Apr 18, 2013 8:19 pm

Thank you Dave for taking the time to write this awesome article.

I have some experience with batteries and volts, amps and watts.

But the real world stuff you mentioned is gold.

My batteries are actually rated at 215 amp hours each. But since they are connected in two series pairs, In have a total of about 430 amp hours. This should fit into your equation to be able to run the fridge at night.

I have been trying to use my 75 watt thermoelectric cooler 24/7 but the clouds are not working with me on this plan very well. With only about 10 amps on average coming in at any given time, I am sort of struggling. When I get a new MPPT solar charge controller going, I should have more power than I can use with these batteries.

I have three 200 watt solar panels just waiting to be hooked up and charge my batteries.

Hopefully this will allow my batteries to fit into the ranks of long life span.

Again, thank you for the info. many people are learning from The Off Grid Project and from people like yourself.

Dave Thacker
Posts: 62
Joined: Tue Apr 16, 2013 8:18 pm
Location: Tipp City, Ohio

Re: Life of Lead Acid Batteries

Post by Dave Thacker » Thu Apr 18, 2013 8:54 pm

Techman,

I guess I missed your per-battery capacity by a bit. I'm not used to working with 6V cells. I should have been thinking, they are double the amp-hour capacity per unit volume (over 12v batterys) so I should have been guessing double on the amps. Oh well. I did somehow end up at about 75% of your actual capacity. Keep adding to that bank whenever you can.

That cooler your using is a neat thing when your driving down the road on a vacation with unlimited power from your truck, but, it's pulling more (I bet) than your refrigerator is going to pull. Those Peltier thermo electric devices are amazing for what they can do in a small space with minimal moving parts (fan on heat sinks) however, they are very inefficient.

Refrigerators are famous for surviving 2-3 days through a power outage (as long as you leave the door shut) because of the stored energy (It's actually a volume of artificially reduced-energy) of all the frozen goods in the ice box. Have you considered when you get a good couple of sunshine days, running the fridge, and freezing down some ice in the ice box (like a few 1/2 gallon milk jugs full of water) then just leaving it off at night (no midnight snacking!) and only running it while the sun shines? I am betting it will use less energy than your cooler and stay quite frosty. Also, you wouldn't be pulling your 12v system down overnight, only robbing it of a portion of the charge it's grown accustomed too.

Before you go to bed, you plug in all panels so first thing in the morning with low sun light, you have all the amps you can get. Obviously the slightly warmed up fridge will want to run steady for an hour or two when it first see's power.

Also, you could setup a small panel to drive a relay so the fridge comes on automatically when the sun comes up.

A short cut to get the fridge trial going would be to freeze a bunch of ice in the landlords freezer, after your fridge gets fully down to temp, throw in the ice. Now your charged (or more accurately - fully depleted of energy inside the icebox) and can get your experiment off to a good start.

The Harbor Freight setup is notoriously expensive on a per watt basis. I know somebody that uses one but I've never measured if the battery charger is really any good or not. Most 12v chargers are not regulated well enough and end up deteriorating the batteries. My friend tested his and the best he can ever get out of it (going to the battery) is 35 watts. On a per watt basis, they are uber expensive, on a square foot basis, they are huge. And, they are amorphous cells, they will decay in value over time. Maybe I should save some of these thoughts for a solar thread.
Dave Thacker
Radicalrc.com, Owner
Radicalrc.com/blog Blogsite

techman
Site Admin
Posts: 1322
Joined: Thu Dec 22, 2011 11:49 am

Re: Life of Lead Acid Batteries

Post by techman » Tue Apr 23, 2013 1:46 pm

Yeah, good solar points. Thanks

I think the HF panels are good for cloudy days. From what I heard, forget the charge controller though, it will ruin your batteries.

I can run the thermoelectric cooler when the sun shines directly off 12 volts. The fridge will not run with my inverter. I need a larger inverter.

I plan to do just as you say though and keep ice on hand. Plus keeping the fridge and freezer full helps a lot.

mr bugsier5
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Joined: Sat Jun 15, 2013 12:36 pm
Location: Brielle , west coast of holland(europe)

Re: Life of Lead Acid Batteries

Post by mr bugsier5 » Thu Nov 07, 2013 7:00 am

most Inportant tip when connecting batterys in a battery bank series/parralel

it is most inportant when you use serie parraleled battery banks that you also connect the innerpoles together !

for instance,
bij use 4 times 6 volt batterys in 12 volt systems do not only connect the positive and negative on the 12 volt side , but also conect the seperate 6 volt cels in parralel, this wil prolong the Working life of the battery's, the more you keep them equal, the better it is !!
in loading and also discharging this wil keep both sets totally equal,

draw/load here +battery 6 v-/+battery 6 v-
con here con here con here
+battery 6 v-/+battery 6 v- draw/load here.

so connect both positive leads on outside, but also the middle conections!

also by bigger banks use opposite conections to draw and load!
keaping the batterys equal is a absolute must to have the most power from your batterys for the longest life expectance!

have fun wit the energy the sun or the wind is giving us !!
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

techman
Site Admin
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Re: Life of Lead Acid Batteries

Post by techman » Fri Nov 08, 2013 10:04 pm

Thank you for the info.

I am considering the best ways to connect my battery bank now. I will be getting some heavy gauge wire soon so I can connect the charge and load to opposite poles too.

mr bugsier5
Posts: 63
Joined: Sat Jun 15, 2013 12:36 pm
Location: Brielle , west coast of holland(europe)

Re: Life of Lead Acid Batteries

Post by mr bugsier5 » Mon Nov 11, 2013 12:17 pm

Hy Troy.
It is not neccecairy to replace the power connection via the buss bars, just reconnect the wires comming from the battery,s, put the 3 negative, and the 3 poitive wires together under one bold, youre wires are long enough to do so, only extra wire is needed to connect the 3 middle connections (6volts)together with two equal size wires , a so called equalize connection, to keep the battery,s exactly equal., becarefull ! , do not shortsircuit!,use isolated tools (use tape to insulate your tools.), you will extend the life of the batterys that way, the more power you keep, the better!
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

jos6i
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Joined: Tue Nov 12, 2013 12:42 pm

Re: Life of Lead Acid Batteries

Post by jos6i » Thu Nov 14, 2013 12:07 pm

I really thank you Mike for your pieces of advice. They really do work.
Even more, May I add in my humble experience just a bit more...
1. using some sort of desulfator, preferably electronic and or epson salt (just some spoonfulls to each cell, it really works).
2. trickle charging (little by little) will improve, get longer life our batteries, whenever they are big or small

mr bugsier5
Posts: 63
Joined: Sat Jun 15, 2013 12:36 pm
Location: Brielle , west coast of holland(europe)

Re: Life of Lead Acid Batteries

Post by mr bugsier5 » Wed Jun 25, 2014 4:56 am

jos6i wrote:I really thank you Mike for your pieces of advice. They really do work.
Even more, May I add in my humble experience just a bit more...
1. using some sort of desulfator, preferably electronic and or epson salt (just some spoonfulls to each cell, it really works).
2. trickle charging (little by little) will improve, get longer life our batteries, whenever they are big or small

my proffesional advice is :never ad anything tho a battery cell other than distilled, or demineralized water.
iff you do not undercharge your batterys the wil not sulfate!, keeping them charged the right amount is all, every battery that is sulfated is damaged, you can revive them somewhat (for instance whith a bedini charger), but the capacitance will go down , the mutch you thry , the will never be new again!!

and offcourse in case off lead acid battery's dont forget to equalize your bank frome time to time!

y will keep on hammering on it that iff you make a battery bank with serie/parralel batterys always conect all batterys together , and than in series, to keep them absolutly equal, it will increase the life expectancy off the bank, and wil give you more capacity and longer use.

example iff you use 4 6 volt batterys serie/parralel to get 12 volt at double amp hours also connect the 6 volt poles together!!

greatings Richard
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

techman
Site Admin
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Re: Life of Lead Acid Batteries

Post by techman » Mon Jun 30, 2014 3:09 pm

Very good point. I would never add anything to a battery besides distilled water. Unless I am converting a battery to a lead alum battery as John Bedini shows but that is a different topic in itself.

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