Use of Car Batteries in Solar Application

balee123balee123 Posts: 86Solar Expert ✭✭
I understand the design differences between car batteries and deep cycle batteries and their intended purposes. That being said, would it be possible to have a battery bank that is made exclusively of car batteries, such that you have enough batteries to only discharge them to say 15% DOD instead of the 50% that deep cycle batteies are designed to handle?

In other words, can a "car battery bank" function as well as a deep cycle battery bank if you don't discharge it too far?

If so, what would be the maximum that one should discharge a "car battery bank" in such an application?

I'm guessing that the described "car battery bank" would not be as good as a deep cycle one, but how bad would it be?

Theoretically, if you made your "car battery bank" large enough, you'd could discharge it less than 5%. It would essentially be "shallow cycle" battery bank.

Would a very large "shallow cycle" battery bank behave like a much smaller deep cycle battery bank in terms of life span, or are there other problems to worry about.

Comments

  • nsaspooknsaspook Posts: 396Solar Expert ✭✭✭
    Re: Use of Car Batteries in Solar Application

    Even if I could get the batteries for free or at a very low cost i wouldn't do it as the "shallow cycle" (using 20% on one battery vs 5% on four batteries) charge efficiency factor is poor (about 60% instead of 85% with deeper discharges) with all the extra interconnects costs, fusing and maintenance costs.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Use of Car Batteries in Solar Application

    "Anything" is possible... But lets look at your requirements instead.

    Do you have a steady supply of "salvage" car batteries and they are basically "free" to you? Would a battery that was cycled 20% and lasted a year or so be statisfactory for your needs?

    Is this a small system (one car battery) or a large one (12 batteries in parallel or series)? Note that if you have "mixed" batteries with, possibly, a short life--You may end up spending a lot of time monitoring/debugging your system to find dying batteries and replacing them.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Use of Car Batteries in Solar Application

    It's more a problem of the way the batteries are discharged and recharged. In most off-grid applications the load pulls the batteries down over several hours, usually at night, and they then have to sit partially discharged (or still being drawn from) until the sun rises and the charging process begins. Deep cycle batteries are meant to do this. Automotive batteries are meant to have sudden, heavy, but short discharges (starting the car) and then be recharged with high current immediately.

    They will work, but since they'll be spending time in a discharged state that isn't what they're designed for the lifespan will be adversely affected. How much so depends on all the factors involved, including DOD and length of time before charging as well as charging current.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    i don't understand why you would even consider using car batteries when there's cheap golf cart batteries out there you can get.
  • Earnest TilleyEarnest Tilley Posts: 56Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    I had that same question awhile back i know a guy at a salvage yard that could get me 12v batteries for $10 each i thought i could get 20 and do that to. I looked at the marine batteries and seen that they have a 3 year warranty and are made for exactly what i wanted to do. If i had to replace 4 or 5 of those $10 batteries it might be worth it but if i wanted any serious power over along period of time i had to get marine batteries. If your going to run anything other than maby a 100watt light with the car batteries i would defiantly go with a marine battery plus your going to have to keep checking and rechecking your batteries to see which one you will have to replace at least once a week with those $10 batteries not worth the hassle to me.
  • balee123balee123 Posts: 86Solar Expert ✭✭
    Re: Use of Car Batteries in Solar Application
    niel wrote: »
    i don't understand why you would even consider using car batteries when there's cheap golf cart batteries out there you can get.

    I guess I should explain the reason for my question. It's based on one of the many "doomsday" senerios that are spoken about on this forum. It's not that I am trying to get away with not spending money on good deep cycle batteries. In fact, I plan to have a battery system based on golf cart batteries soon. It was really a thought experiment based on having a solar electric system, but only having access to batteries from cars after the deep cycles have gone bad. So based on what people have been writing it sounds like it is possible, but it would require a lot of monitoring and the batteries will have a shorter life span than golf cart/deep cycle batteries.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    balee123 wrote: »
    I guess I should explain the reason for my question. It's based on one of the many "doomsday" senerios that are spoken about on this forum. It's not that I am trying to get away with not spending money on good deep cycle batteries. In fact, I plan to have a battery system based on golf cart batteries soon. It was really a thought experiment based on having a solar electric system, but only having access to batteries from cars after the deep cycles have gone bad. So based on what people have been writing it sounds like it is possible, but it would require a lot of monitoring and the batteries will have a shorter life span than golf cart/deep cycle batteries.

    in an emergency you can use them, but they won't last long trying to use them in the deep cycle applications we use in solar. you will get some cycles out of them, but exactly how many i can't say and even that would vary as batteries vary too. of course that's a what if and isn't something you want to design your system with in the first place.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Use of Car Batteries in Solar Application

    I wouldn't worry too much about doomsday. The 11,237 times it's been predicted so far in my lifetime have all proven false.
    And if it does happen, the car batteries may not be so readily available either as everyone will be scavenging for them.

    Except me. I'll be the guy with the target painted on my back and the sign around my neck that says "shoot me first". :p
  • cruiser guycruiser guy Posts: 87Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    Another question on this same train of thought.

    I had a pair of GEL Deka Solar 230 AH batteries but wanted more power so I got six 200AH truck batteries instead. Am I setting myself up for problems? I check them monthly for fluid levels and try to keep them well charged. This is a 24v system that is totally stand-alone (the grid stops 150kms away and it isn't constantly reliable anyways).

    The six truck batteries were a little more than the pair of GEL cells were so when you look at the per AH cost the truck batteries are much better.

    Proper deep cycle batteries are going to be almost impossible to find here in Sierra Leone.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Use of Car Batteries in Solar Application
    Another question on this same train of thought.

    I had a pair of GEL Deka Solar 230 AH batteries but wanted more power so I got six 200AH truck batteries instead. Am I setting myself up for problems? I check them monthly for fluid levels and try to keep them well charged. This is a 24v system that is totally stand-alone (the grid stops 150kms away and it isn't constantly reliable anyways).

    The six truck batteries were a little more than the pair of GEL cells were so when you look at the per AH cost the truck batteries are much better.

    Proper deep cycle batteries are going to be almost impossible to find here in Sierra Leone.

    This is a different case. Economics comes into play here. You could get the deep cycle batteries, but at how much more expense? The main problem with the auto type batteries is that they won't last as long being used this way. But if the others cost twice as much and these last half as long ... you use the truck batteries.
  • PhotowhitPhotowhit Posts: 4,728Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    Proper deep cycle batteries are going to be almost impossible to find here in Sierra Leone.

    If you have a port, likely you'll be able to find proper deep cycle batteries, when I lived in Florida, L16's where often called boat batteries, here in the mid west they are identified as floor scrubber batteries...lol.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    Photowhit wrote: »
    If you have a port, likely you'll be able to find proper deep cycle batteries, when I lived in Florida, L16's where often called boat batteries, here in the mid west they are identified as floor scrubber batteries...lol.

    would that be because you have to drag them across the floor?:p they also can double as a boat anchor. (please don't take me seriously here.)
  • cruiser guycruiser guy Posts: 87Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    Photowhit wrote: »
    If you have a port, likely you'll be able to find proper deep cycle batteries, when I lived in Florida, L16's where often called boat batteries, here in the mid west they are identified as floor scrubber batteries...lol.

    That would be true if the port had those modern inventions like forklifts and the like. This one does not! It's cheaper to have an army of guys working for a buck or two a day (it also provides more folks with work, and I AM serious).
  • john pjohn p Posts: 814Solar Expert ✭✭
    Re: Use of Car Batteries in Solar Application

    For people living in countries like USA ,Australia most of Europe its hard to understand whypeople dont do the accepted"normal" thing. Like using deep cycle batteries.
    I use "truck" batteries myself.dont care if they dont last as long or need every few days watter topping up. THEY ARE PRACTICAL.
    Why? In Philippines like all third world countries some things are almost impossible to do.In the west you just go on net or on phone and order what you need and using credit card pay for it and an effecient transport company will deliver the goods in mabe 2 days.Ok ? Or you can go to a good battery supplier and buy the items you need and take with you. , Great huh?And what the west accepts as normal.
    Now for 80% of the world all that is not possible. Usually only major multinational stores accept credit cards and only in person. In all other towns credit cards are not accepted at all.
    Battery stores only exist in a small way in major cities and you need to go in person and pay cash, then somehow try to arrange a bus line to take them to your town. then you still have to get them home ..
    You see some problems ???
    Now truck batteries are available "everywhere" as every truck and bus uses them. In 3rd word countries they are cheap,usually about half the price compared to western countries. {the sales person and the battery facttory worker mabe each earns about $200 a MONTH.
    You only have to go to mabe 2 to 4 hardware stores to get enough "identical " batteries.
    A local bus will home deliver them.for very low cost. At home you have some worker check them every few days for you if you are not there cost mabe $1 for each weeks topping up.
    I find if you only use the first 20% of the charge they last over 2 years and you get about 50% trade in on the next lot.

    There is no such thing as one type fits all. I have done some systems using Lithium ion phosphate cells and they need no maintainance and in use over 3 yrs now andcharged using PWM charger. but they cost a lot more than truck batteries and would be very expensive for a big system.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    john p,
    if they can get solar panels, they can get golf cart batteries.
  • squarebobsquarebob Posts: 25Registered Users ✭✭✭
    Re: Use of Car Batteries in Solar Application
    niel wrote: »
    john p,
    if they can get solar panels, they can get golf cart batteries.
    Maybe, but at what cost?
  • john pjohn p Posts: 814Solar Expert ✭✭
    Re: Use of Car Batteries in Solar Application

    getting golf cart batteries has exactly the same problems as getting true deep cycle batteries. golf carts are only used in major cities not smaller cities or towns.
    Its not easy getting solar panels either or charge controllers. In China you can live within one klm of a solar panel factory and not be able to buy solar panels. I know because I have some friends in China and they cant buy in their province charge controllers or solar panels and there are made there.All for export ONLY.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    hey, i never said they were cheap, but odds are the pvs were also hiked upward in costs for them just as deep cycle batteries would be. if the access is there for pvs then they can get batteries and it doesn't matter if they are from china or not as access is access. i'm quite sure ups didn't deliver their pvs so i'm confused why pvs are available, but not a deep cycle battery? so what if they don't have golf carts as most of everybody that buy the batteries don't have them either. i can understand some have difficulties getting some things, but getting batteries isn't any more difficult than getting pvs.

    no more discussion on this moot point.
  • PhotowhitPhotowhit Posts: 4,728Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    That would be true if the port had those modern inventions like forklifts and the like. This one does not! It's cheaper to have an army of guys working for a buck or two a day (it also provides more folks with work, and I AM serious).

    OK Guys,

    What part of 'Boat batteries' don't you understand? Boats don't want to run their generators or motors all the time, hence are pretty much an off grid system using a genny for charging. Please feel free to ignore the information, I do understand that transportation might be a problem, but I have found poorer people and areas tend to figure things out better than wealthy areas, as poorer people are more generous than wealthy when it comes to their time and effort.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • shellashella Posts: 23Registered Users
    Re: Use of Car Batteries in Solar Application
    john p wrote: »
    For people living in countries like USA ,Australia most of Europe its hard to understand whypeople dont do the accepted"normal" thing. Like using deep cycle batteries.
    I use "truck" batteries myself.dont care if they dont last as long or need every few days watter topping up. THEY ARE PRACTICAL.
    Why? In Philippines like all third world countries some things are almost impossible to do.In the west you just go on net or on phone and order what you need and using credit card pay for it and an effecient transport company will deliver the goods in mabe 2 days.Ok ? Or you can go to a good battery supplier and buy the items you need and take with you. , Great huh?And what the west accepts as normal.
    Now for 80% of the world all that is not possible. Usually only major multinational stores accept credit cards and only in person. In all other towns credit cards are not accepted at all.
    Battery stores only exist in a small way in major cities and you need to go in person and pay cash, then somehow try to arrange a bus line to take them to your town. then you still have to get them home ..
    You see some problems ???
    Now truck batteries are available "everywhere" as every truck and bus uses them. In 3rd word countries they are cheap,usually about half the price compared to western countries. {the sales person and the battery facttory worker mabe each earns about $200 a MONTH.
    You only have to go to mabe 2 to 4 hardware stores to get enough "identical " batteries.
    A local bus will home deliver them.for very low cost. At home you have some worker check them every few days for you if you are not there cost mabe $1 for each weeks topping up.
    I find if you only use the first 20% of the charge they last over 2 years and you get about 50% trade in on the next lot.

    There is no such thing as one type fits all. I have done some systems using Lithium ion phosphate cells and they need no maintainance and in use over 3 yrs now andcharged using PWM charger. but they cost a lot more than truck batteries and would be very expensive for a big system.

    at last someone who think along the same lines as me
    i live in the UK i have just got into solar in a big way i have posted on here and don't get why you can't use scrounged parts
    yes they won't last long but at least you have some power in an emergency
    i would like to make my system out of as much scrap material as possible i am in the frame of mind of having lights and something from stopping the kids from climbing the walls

    its all about what your priority's are like if you want to power your microwave or cooker then solar isn't for you
    wow needed to vent thank you for keeping it real
  • bill von novakbill von novak Posts: 797Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application
    shella wrote: »
    i live in the UK i have just got into solar in a big way i have posted on here and don't get why you can't use scrounged parts

    I don't think of the UK as very third world. I suspect you could get T105's pretty easily; they are common batteries worldwide.
    yes they won't last long but at least you have some power in an emergency

    All too often such banks are dead by the time you want to use them - especially with used (unmatched, different age) batteries.
    i would like to make my system out of as much scrap material as possible i am in the frame of mind of having lights and something from stopping the kids from climbing the walls

    I'd suggest a small generator would be a much better use of your money. But if you really want to just try stuff then there's nothing wrong with using car batteries - provided you treat them with respect (like any other battery) and don't expect too much from them.

    As some background if you are wondering what the big fuss is - Anyone who works with renewable energy hears the same things pretty often. "I bought a big solar panel and I want to run JUST the air conditioner in my apartment." "I would get decent batteries but it's too hard and the auto parts store is right down the street." "So I got a battery and a solar panel! What do I hook together!" These questions make people cringe for several reasons:

    1) Any big battery is dangerous. A simple mistake will lead to at least burns and destroyed batteries if not a fire. Thus someone who has a bunch of batteries, solar panels and alligator clips makes people very nervous, because a) they don't want to give people advice that leads to them getting hurt and b) having solar get a reputation as a big fire risk is not good for anyone.

    2) There are lots of ways to connect a solar power system that seem to work OK but are actually pretty bad in terms of safety, efficiency and/or run time. Web sites like this try to help people do it safely, but the lower the experience level of the person doing the connecting, the more likely they are to not know basic electrical safety and design principles, and the more likely they are not to worry about such things. Thus when people hear "I don't want to be bothered going down to the battery supplier" they may worry that that will lead to "nor do I want to be bothered getting adequate gauge cables; I'll just use a lot of paralleled speaker cord."

    3) Most people here want to try to help other people be happy with their solar power systems, and experience has shown that most people just aren't happy with car batteries. Even if it's "just in case the power goes out" and "I won't discharge them that much" etc etc.
  • shellashella Posts: 23Registered Users
    Re: Use of Car Batteries in Solar Application
    I don't think of the UK as very third world. I suspect you could get T105's pretty easily; they are common batteries worldwide.



    All too often such banks are dead by the time you want to use them - especially with used (unmatched, different age) batteries.



    I'd suggest a small generator would be a much better use of your money. But if you really want to just try stuff then there's nothing wrong with using car batteries - provided you treat them with respect (like any other battery) and don't expect too much from them.

    As some background if you are wondering what the big fuss is - Anyone who works with renewable energy hears the same things pretty often. "I bought a big solar panel and I want to run JUST the air conditioner in my apartment." "I would get decent batteries but it's too hard and the auto parts store is right down the street." "So I got a battery and a solar panel! What do I hook together!" These questions make people cringe for several reasons:

    1) Any big battery is dangerous. A simple mistake will lead to at least burns and destroyed batteries if not a fire. Thus someone who has a bunch of batteries, solar panels and alligator clips makes people very nervous, because a) they don't want to give people advice that leads to them getting hurt and b) having solar get a reputation as a big fire risk is not good for anyone.

    2) There are lots of ways to connect a solar power system that seem to work OK but are actually pretty bad in terms of safety, efficiency and/or run time. Web sites like this try to help people do it safely, but the lower the experience level of the person doing the connecting, the more likely they are to not know basic electrical safety and design principles, and the more likely they are not to worry about such things. Thus when people hear "I don't want to be bothered going down to the battery supplier" they may worry that that will lead to "nor do I want to be bothered getting adequate gauge cables; I'll just use a lot of paralleled speaker cord."

    3) Most people here want to try to help other people be happy with their solar power systems, and experience has shown that most people just aren't happy with car batteries. Even if it's "just in case the power goes out" and "I won't discharge them that much" etc etc.


    i totally understand where your coming from and i don't see the UK as a third world country but that does not mean we all have that kind of money i am not saying to go into solar blindly i have done a lot of research and know its time to ask questions. in my area we get blackouts quite often not for a long time but when you have been spoilt buy having power you kind of get used to having lights when you want it not when you need it.
    i am tying this as an experiment i can understand you steering a total newbie in the right directions as i am a newbie. yes we live in the land of plenty but i still believe that solar power should be for all people not just for the people that have the money to buy the expensive stuff. we all have to start somewhere and if someone has to start with car battery's and they have been the information it is up to that person to decide.
    i have read a lot of posts on this forum and am loving it and i know the different type of battery's and why deep cycle battery's are best for solar application.
    i don't mind that you have to look after car battery's more and check the levels i do that anyway but that is my choice. in third world county's they use what they have and scrounge and make do with what they have and get on with it i have the same mentality but i want to be safe course i don't know what i am doing. don't make me feel bad for not having the money to buy the expensive equipment. as i have seen some of the prices. i just think that it is OK to start small and work your way up thats why i am on this forum too learn and ask questions. i too thought that you could power a lot things on solar power i know now what is possible it has not put me off just changed the way i think.
    hope this made sense
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Use of Car Batteries in Solar Application

    batteries are not rare, but just more expensive.

    i do not see how putting magnesium sulfate into a battery will revive it in any true sense. it may temporarily energize some batteries if it is a case of depleted electrolyte, but would still be very temporary of a charge and far from being at its rated capacity. the condition of the plates is more crucial for the power than the electrolyte as it could be eroded away, shorted out, or heavily sulfated.

    we have already acknowledged the higher cost of solar compared to the grid many times.
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