# Question about solar battery maintainers

Registered Users Posts: 6
I have an electric fence energizer hooked up to a deep cycle marine battery that I bought at Walmart. I have also hooked up a 1.8 watt solar panel to the battery that should be trickle charging it at the same time. The energizer pulses out a current on the electric fence line to keep my dogs from escaping out into the desert.

I bought the battery in March 2009, and last week, I checked the voltage of the battery with my multimeter and the battery held a 4 volt charge. The last two batteries that I had charging the energizer were car batteries, also bought from Walmart, and set up the same way with the solar battery maintainer hooked up to the battery, supposedly trickle charging it. But they were going bad, so I read about deep cycle batteries, and how they can take being recharged over and over without too much of a problem, so I got one.

Now, I'm learning about "loads" and other electrical terms, so my question is: Can I hook up my energizer to the battery at the same time a solar battery maintainer is hooked up as well? Or should I go for a bigger solar panel, say a 5 watt, and get a charge controller? I was thinking of the Morningstar SS-6L.

That way I don't go back to Walmart every three months replacing a battery. lol

Thanks!

• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Question about solar battery maintainers

1.5 watts won't even keep up with the natural drain on the battery (self discharge) the fence charger itself has some draw, and I would contend that it draws more than 1.5 watts. Are you not charging it from any source?

What you need is a Pv big enough to cover the load of the charger, lets say for the sake of argument that it is 15 watts. So 15 watts * 24= 360 watt/hours/day. So you would need AT A MINIMUM a panel that could produce ~ 50% more than than, plus any number of days or reserve you desire. (suggest 3-5) The 50% represents average Pv efficiency and battery charging efficiency. So that would be 360*1.5=540 wh/day. If you average 4 hours of good sun (not many places average much more,(540/4=135) that would suggest a panel in the 135 watt range, MINIMUM. If you wish three days of reserve you would look for a panel of ~400 watts.

So now you can take these numbers and adjust them up or down to represent the real draw of the fence charger. 30 watts then make that 270-800 watts. 7.5 watts, 65- 200, and so forth.

Of course you can supplement the solar with grid or generator power as needed.

The reality is that most people underestimate their loads and over estimate the amount of solar they really get.

http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

If your battery is reading 4 volts, you probably have wrecked it, sorry to say. Read up on loads, design and build a proper Solar charger, sized for the battery and the load.

Good luck, and welcome to the forum,

Tony

PS If you build a real solar system you will also need a charge controller to prevent another battery killer, over charging.
• Registered Users Posts: 6
Re: Question about solar battery maintainers

Thanks, Tony, for your advice. In reading your reponse, you said "1.5 watts". I think you meant "1.8" watts, in reference to my Sunforce 12 Volt Battery Maintainer.

I went outside to see what the input load was on the charger, and on the sticker it says this:

Input: 12, DC, .09A

In researching the determination of watts from volts and amps, the formula I found was: watts=volts x amps. So with that, I derived that the wattage of the charger is 1.08 watts ( 12 x .09 = 1.08 ). Is that correct?

If so, then using your information:

1.08 watts X 24 hrs = 25.92 watt/hours/day

25.92 X 1.08 watts load from charger = 27.99 wh/day

Los Angeles averages about 5 hours a day of sunshine. (I used Los Angeles because there wasn't a Palmdale, CA statistic, which is where I live.) So....

27.99/5 = 5.598 ~ 5.6 watts

So I would need a 5 to 6 watt solar panel to handle my needs. Are my calculations correct?
• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Question about solar battery maintainers

You're learning quickly more so than many,

Your are right in that VXA=W

So your daily use would be ~28wh/day.

But two things to note, solar panels typically put out ~80% of their name plate rating under IDEAL conditions, so you have to derate at least 20%. Also, for every watt you take out of a lead/acid battery it takes about 1.2 watts put back in, just to stay even. Additionally, all batteries will have some self discharge rate.

So, not counting any reserve, you would need to add ~28wh/day PLUS 40%, or about an additional 12 wh for a total of ~40. So in five hours you would need ~8 watts or a bit more. Add in a three day reserve and you will need ~25 watts.

Does this help?

Tony

PS As many have learned over the years on this forum, don't trust my math!
I'm sure someone will chime in with more "real" numbers,
T
• Registered Users Posts: 6
Re: Question about solar battery maintainers

Well, I'm just trying to justify cost effectiveness here. I can afford a 5 watt solar panel, but not a 28 to 30 watt. It wouldn't make sense for what I'm trying to do. At this point, I'd rather return the battery to Walmart, and use that money to buy a solar-powered fence charger, which would be cheaper than getting a higher-wattage solar panel.

• Banned Posts: 17,615 ✭✭
Re: Question about solar battery maintainers

Solar fence chargers aren't all that cheap:

http://www.princessauto.com/farm/fencing/electric/2430082-energizer-25-miles-6vdc-solar

Of course that's Canadian \$ (not including our excessive sales taxes) and in Canada. Your actual price may vary. Could be cheaper than panel/charge controller/battery.
• Solar Expert Posts: 9,362 ✭✭✭✭✭
Re: Question about solar battery maintainers

VW installs 5W maintainers into their windshields when shipping overseas. Dealers
(or their lot jockeys) sometimes sell them on ebay. They aren't weather tight, but
parking them under a old window to keep rain off, would work, I'd guess you need
2 of them. search for VW solar @ ebay
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Question about solar battery maintainers

the ah rating of the battery needs consideration as well. this is the 20hr ah rating and not cca. the minimum charge should not be less than 5% of the battery ah rating. if you are drawing power at the same time you are charging then add that draw to the 5% minimum for your new minimum charge.
if the battery you got from wal mart is the big one then this is 115ah and that would need 5.75a with no load on it. 5.75a x 17.4v = about a 100w pv. adding any power draw to that will up the pv requirements with a battery like that. if you can't afford the pvs how are you going to afford replacing the battery all of the time? it's going to be a big expense no matter what unless you stop letting you dogs run there or put up a real fence.
i'm not to sure on the reliability of that controller either.
• Solar Expert Posts: 1,398 ✭✭✭✭
Re: Question about solar battery maintainers

When you say sticker says 12v @ 0.090 amps I assume that is the power required of the high voltage generator.

That is a little over a watt. I would guess current would be a bit higher at a lead-acid float charge level of 13.2 vdc.

I have Walmart marine class 30 battery (125 A-H). When charged the float current is about 0.030 mA at 13.2 vdc. These are lead-calcium batteries which have a lower leakage then the lead-antimony batteries used for deep cycle off-grid systems.

The leakage does go up with temperature.

Another question is what is worse case high voltage generator consumption. Any leakage path may make the consumption higher. A rainy day, particularly after a dusty dry spell that has coated the insulators with dirt, when wet, may raise the load (and rainy day means clouds, means little solar charging). Any weeds that grows up and touches fence may also increase load.

If you have the smaller marine battery it is about 70 A-Hr. It should say on the battery. Even with this battery, assuming only using half capacity would still give you over twenty days.

You should have a 5 watt panel and some kind of charge controller to prevent overcharge on battery. (keep float at 13.2 vdc)

Also, a little advice about buying off-the-shelf lead acid batteries. I have a small pocket voltmeter I have calibrated and I check the voltage on the battery before I buy it. Sometimes they have sat on the shelf for months.

1) don't buy it if date code is over 2 months old.

2) don't buy if battery voltage is less then 12.5 vdc.

Charge the battery for a day before using it. Rested, off charger for 4 or 5 hrs the fully charged no-load voltage should be 12.7 vdc.

Once you have it installed and running, check the voltage every few days for a month or so. In the morning battery should not be less then 12.5vdc. In afternoon, with good sun day it should be at charge controller float voltage 13.2 -13.5 vdc. If in afternoon you are still less then 12.7 vdc you are not getting enough charge and going net negative on power consumed versus generated by PV panel.
• Registered Users Posts: 6
Re: Question about solar battery maintainers
RCinFLA wrote: »
When you say sticker says 12v @ 0.090 amps I assume that is the power required of the high voltage generator.

That is a little over a watt. I would guess current would be a bit higher at a lead-acid float charge level of 13.2 vdc.

I have Walmart marine class 30 battery (125 A-H). When charged the float current is about 0.030 mA at 13.2 vdc. These are lead-calcium batteries which have a lower leakage then the lead-antimony batteries used for deep cycle off-grid systems.

The leakage does go up with temperature.

Another question is what is worse case high voltage generator consumption. Any leakage path may make the consumption higher. A rainy day, particularly after a dusty dry spell that has coated the insulators with dirt, when wet, may raise the load (and rainy day means clouds, means little solar charging). Any weeds that grows up and touches fence may also increase load.

If you have the smaller marine battery it is about 70 A-Hr. It should say on the battery. Even with this battery, assuming only using half capacity would still give you over twenty days.

You should have a 5 watt panel and some kind of charge controller to prevent overcharge on battery. (keep float at 13.2 vdc)

Also, a little advice about buying off-the-shelf lead acid batteries. I have a small pocket voltmeter I have calibrated and I check the voltage on the battery before I buy it. Sometimes they have sat on the shelf for months.

1) don't buy it if date code is over 2 months old.

2) don't buy if battery voltage is less then 12.5 vdc.

Charge the battery for a day before using it. Rested, off charger for 4 or 5 hrs the fully charged no-load voltage should be 12.7 vdc.

Once you have it installed and running, check the voltage every few days for a month or so. In the morning battery should not be less then 12.5vdc. In afternoon, with good sun day it should be at charge controller float voltage 13.2 -13.5 vdc. If in afternoon you are still less then 12.7 vdc you are not getting enough charge and going net negative on power consumed versus generated by PV panel.

I have the Everstart 27DC-6 with 115 amp hour rating. You are right about "leakage", spiderwebs touching the electric wire and the ground, weeds, etc. I'm sure that is what killed this battery. And hooking up a 1.8 watt battery maintainer didn't help either, I'm sure. I've been walking the line, clearing paths to the ground that don't belong.

RCinFLA, I'm thinking of going with your consideration of getting a 5 watt panel with a charge controller (I'm looking at the Morningstar SS-6L) and returning the battery to Walmart to get a new one because it's still under warranty. I'm hoping this setup works, or I'm going to have to lug the battery back and forth to the garage for charging. That thing is heavy!
• Registered Users Posts: 6
Re: Question about solar battery maintainers

RCinFLA, in looking at the Morningstar SS-6L, its regulated voltage for a sealed battery is 14.1V. You were saying to keep it at 13.2V. Would I kill my battery with this charge controller? (mind you this website sells the thing) LOL
• Solar Expert Posts: 5,183 ✭✭✭✭
Re: Question about solar battery maintainers

gedanjj, I think you need to reread the Battery FAQs to get a good understanding

of the terms BULK charge, Absorb charge and Float charge..

they are all different and most Charge Controllers are designed to deliver at least 2 of these 3 types of charge (have not looked up the specs of your chosen model). that should answer your question.

Without the CC in the system any '12 v' solar panel will deliver a max voltage in the neighbourhood of 17 volts to your battery.

Eric

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Question about solar battery maintainers

"I have Walmart marine class 30 battery (125 A-H). When charged the float current is about 0.030 mA at 13.2 vdc."

.03ma? really? no way it's that low.
did you mean .03a instead, which is 30ma? even that is 4x lower than i'd ever recommend, but it is possible on a well taken care of new battery with that 30ma going 24/7.
• Solar Expert Posts: 5,433 ✭✭✭✭
Re: Question about solar battery maintainers

No one here is influenced by what the site host, NAWS, sells or doesn't sell. Folks here will suggest what is the best option in their opinion.

No matter how you crack the nut, if you expect for this (or any) system to work to some level of satisfaction, you have to obey the laws of physics. That is, if there is X amperage draw over Y time, you will need to put that much energy back into any battery system or the inevitable result will be the battery will die.

You can either buy the proper size solar panel, charge controller, and battery, or you can keep buying batteries. It is really that simple.

Tony
• Registered Users Posts: 6
Re: Question about solar battery maintainers

I want to thank everyone for helping out on this issue.

An update....I've decided NOT to go solar charging my battery for my electric fence. I found it simpler just to use a charger from Walmart to charge my marine battery from time to time.

When I started this thread, I forgot to mention about the status of the battery. It was hovering at around 3 volts left. When people on this forum started giving me links to read, I was afraid of going back to Walmart ONCE AGAIN to replace this battery. But I decided to buy a battery charger and see if I could bring the battery back to life.

At first, the charger said "BAD" on the display for the first two times I've charged the marine battery. But on the third try, it was able to fully charge the battery 100 percent! After charging it, and letting it sit for two hours, I hooked it back up to the electric fence energizer, clearing any paths to ground that were hanging off the energized wire (i.e. spider webs, grass, etc.) That was the second week of August. I've been turning off the energizer at night to conserve battery power. I can't believe it lasted this long.

So....once again, thanks for those links. I had to actually come back here to look for those links to look up something. I learned a lot about batteries. I thought I knew enough, but I was wrong.