deep cycle batteries: best brand for solar?

I know zip on the topic. Im doing research for my man and there don't seem to be forums out there that are not connected to a sales site. Any input would be lovely

Surrette.

But I wouldn't spend my money on solar batteries.
You will get a bigger bang for your buck if you go with a forklift battery.

I got mine through http://giantbatteryco.com/

You will pay much less per amp your with forklift and they are made to take a beating.

Melissa, I am making the exact same advice as Mark. Go with a forklift battery (unless of course your system is very small). I also recommend the same company. My research shows that you can't beat their prices, nor will other lead acid batteries outlast the forklift battery. Also, the pricing for the batteries at this company includes delivery. The company will also pick up a discarded battery free of charge. Forklift batteries often last 20+ years in this application. See the forums at windsun.com for some mention of forklift batteries in this application. Also see a blog post on www.sustainablepreparedness.com. There are many accounts all over the web about forklift batteries in solar applications, and all I've seen are favorable.

BTW, feel free to ask questions here, but the guys active on the forums are windsun.com are your best resource.

Melissa, you did not tell us the size of the system or your budget. If you are going small scale, I would suggest Deep Cycle Marine Batteries. I will not suggest a brand name because I have only tried 1 type and it is not available in your area.
The important thing is that it is a deep cycle type and not a regular car battery. This is because car batteries are designed to put out a lot of power for a very short time and if you run them down often they will have a very short life. Deep Cycle types put out a moderate amount of power for a long time and can be discharged to a low level many times.
If you want a large system and can afford a forklift battery, that is the way to go.

Surrette 5000-series with CS plates are actually heavier duty than a forklift battery. The design of your utility room will also determine what type of battery to use, as the typical 1300ah 24V forklift battery will weigh around 1,200 lbs.

Inverter selection and planned loading will play a factor. Forklift batteries will experience a lot of voltage "sag" under heavy loading from a 4 kVA inverter. Using parallel strings of Surrettes often provides much better full load performance. While voltage "sag" under load is not a problem for traction and lift motors, it becomes a serious issue with fully loaded inverters due to the efficiency curve of the inverter falling off the face of the earth when the voltage drops to 22.5V under full load.

A forklift battery is a single string of 2V cells, meaning every cell in the battery has to deliver the full amps of the load. If you consider a Conext XW4024 inverter pulls 179 amps @ 25.2V at full rated load, that same inverter pulls 229 amps @ 23.2V at full rated load. So the inverter full-load efficiency drops from 87% to only 75% when you get excessive voltage sag. The rule of thumb is to not pull more than 75 amps from a single string on an inverter system, otherwise you will not be able to use the inverter at full load for more than a couple minutes. So obviously a 4 kVA 24V inverter requires three strings of appropriately sized batteries to operate it at full load.

When the inverter overloads, it gets worse. The above mentioned Conext XW4024 as an example, can deliver 5.3 kVA for up to 10 minutes. At the rated input voltage of 25.2V, the amp draw goes up to 250 amps.

This is all very critical stuff in proper design for off-grid power systems. So don't go and buy a forklift battery and think you got it made.

Do not buy marine deep cycles. They are typically lead-calcium grid construction to reduce water loss and gassing under charging. They lose capacity very quickly after 400-500 cycles and are usually at less than 50% of original capacity within 2 1/2 years being daily cycled in an off-grid installation. Marine deep cycles are casual use batteries.

For an economy system I would recommend 6V golf cart batteries. Just about every manufacturer out there makes T-105 232ah replacements, and they're all pretty good quality. Most folks can get 4-5 years out of GC-2 batteries being daily cycled on a small off-grid system.
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Chris

Chris, this is excellent information. Thanks for sharing. Your thumb rules are roughly what I've heard from other sources (I heard stay under 100 amps from the battery assuming single strand, which is roughly what you listed when inverter losses are factored). For clarification, please confirm or correct the following: As long as the net discharge rate of the battery is limited, then voltage sag will not be a problem. The scenario I imagine is that the inverter is not used to power very large loads unless either generator support is used or if an opportunity load (PV array producing at a high rate). Of course, this is what I would do (make sure other sources support the battery/inverter system). Now, some others might imagine otherwise (you know what I mean - they might just get a big forklift battery, big inverter, and expect to power the home as if it's on the grid... come to think of it, many people might actually try this, so good on you for pointing out the details, ).

So far, I'm convinced that a forklift battery is the best value. It's not necessarily the toughest thing out there, but my research has me sold that there is nothing better from a $/KWh perspective. Please correct my misconception if you know better. Thanks Mr. Olson.

Just to put some of this in perspective:

If you are drawing so much from your forklift batteries that "sag" is a problem--then you are not talking about a system that should ever be set up with just golf cart batteries.

When you design your system--don't design it so you are operating at maximum potential. Build a lot of extra capacity into it.

Put less load on it than it is rated for. Buy more battery than you think you will need.

For example, I try to never draw my batteries below 94%. They just cycle between 94 and 100 % each day.
That way they should last 20 years.

if you draw them down and discharge them "deeply", then they will only cycle a few thousand times and you will be buying new ones before you know it.

So, if you have the money, buy the Surrettes.
If you want to economize a bit, buy the forklift batteries--but buy the largest capacity you can. (I have two 24 volt batteries that weigh 1800 lbs each... running a 48 volt system)
We moved them by putting some metal pipes under them and rolling them on the pipes to get them in place.
However, back when I lived in a mobile home--that wouldn't have worked.
So where you are going to place them was a great point for Chris to bring up.


Either way you can design a system that will run a fridge/freezer/lights etc.

If you just want to have some lights on solar and maybe run a computer a little bit--then the golf cart approach could work.

If you are researching what might work, try going to wholesalesolar.com and looking at the off grid package deals. They will have already configured everything and that will help you know what you need.
then you can dream accordingly (:

Forklift batteries are definitely the best bang for the buck. You will spend roughly double for the same kWh capacity if you choose 5000-series Surrettes. However, the Surrettes are more efficient. One of the downsides with forklift batteries is that with their tall jars they are prone to stratification issues. Forklift batteries are designed to be charged by industrial IUIa profile chargers. There is no RE equipment on the market today that can do the IUI charge profile. So they require frequent equalization charges (about every 30 cycles) to keep them healthy. This uses up a LOT of power (and fuel) because most off-grid folks end up having to do it with the generator.

Surrettes never require EQ unless the SG in the cells varies by more than 20 points. And the Surrettes will run about 50% more cycles than the typical forklift battery in their life before they get to 50% of their original capacity (considered end of life). People who run forklift batteries for 12-15 years only do so by cycling the battery very shallow and not ever needing more than 20% of its amp-hour capacity. Otherwise the typical forklift battery (GB Industrial, Crown, you name it) are rated for 1,500 cycles to 80% DoD. Their typical lifespan on forklift duty is 5-6 years.

So there's a little more to consider than "a forklift battery is the best". To summarize:

Downsides to the forklift battery;
it requires overhead lifting equipment to move one
they require more frequent EQ's.
as the battery ages it will require close to 200% of the amp-hours in vs what you get out at end-of-life

Downsides to Surrettes;
they are expensive

Upsides to forklift battery:
best kWh storage capacity for the buck

Upsides to Surrettes;
two reasonably strong people can move a 5000-series battery by hand
more efficient charging over its life - as the battery ages it will require about 150% of the amp-hours in vs what you get out at end-of-life.
--
Chris

mark andrews wrote:If you are drawing so much from your forklift batteries that "sag" is a problem--then you are not talking about a system that should ever be set up with just golf cart batteries.

Actually, GC-2 series golf cart batteries have fairly thin plates and they can put out some serious amps with less "sag" than a forklift battery can. They are excellent for newbies to off-grid. They are pretty tough and will take a lot of abuse and deep cycling, they can go up to 30 days at a time without being fully charged, and they're cheap because they build them by the truckload and there's a LOT of competition in the golf cart battery business. Everybody and his brother builds T-105 replacements.

For somebody new to off-grid battery systems I always recommend them because no matter how much you preach on how to care for batteries the newbie is going to wreck their first set within the first 4 to 5 years anyway. I like to see the off-grid newbies practice on GC-2's before they drop the big bucks on good ones.

Buy more battery than you think you will need.

Wrong. Dead wrong. Do NOT buy battery capacity unless you have the proper RE capacity to charge it. This is the worst mistake newbies make. Batteries are the single most expensive expendable item for off-grid systems. Most off-grid folks spend more money on batteries alone than people who have utility power spend on double the kWh that the off-grid family uses. You size the battery to the loads and no bigger. You size the RE equipment to the battery, and if in doubt spend more on generating capacity. You size the inverter to carry the normal peak loads, and preferably buy a good one that has generator support for overloads. And don't be afraid to use the inverter - inverters run at poorest efficiency at less than 20% load. If you buy a 3.5 or 4.0 kVA inverter and run it at only 200 watt load all the time you are throwing your battery capacity right out the window and letting it go up in smoke. This is the efficiency curve for a SW Plus 2524, as an example, and note that it requires minimum 400 watt load on this little inverter before it reaches peak efficiency

For example, I try to never draw my batteries below 94%. They just cycle between 94 and 100 % each day.
That way they should last 20 years.

if you draw them down and discharge them "deeply", then they will only cycle a few thousand times and you will be buying new ones before you know it.

I hate to tell you this, but you are killing your batteries. You are cycling them on the absolute LEAST efficient part of their charge/discharge curve. FLA batteries that are not cycled deep enough to keep active plate material exposed will die young. They get anemic and weak just like people that set around all day. I don't know how long you been doing this, but I think I'd throw an amp-hour test at them and see what they got left. If they are down to 70-80% of their original capacity, cycle them to 1.75 VPC and recharge about three times and they'll come back. If you're below 70% capacity already, you are in for some serious work to bring them back because they've already gone into their death spiral. Batteries on grid-tie/battery backup systems must be AGM because FLA will die in short order living their life on float. Once a FLA deep cycle battery is put into service it MUST be deeply cycled at least once a month. At that DoD you can't even get adequate absorb time to keep electrolyte mixed.
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Chris

Chris,
Thanks for your input. I think we mostly agree on everything.

I wasn't suggesting they buy more battery than they need or can charge, I was suggesting most people starting out "thinking" they can do more with less than they really can.
So they should go on line and research it.

Next, however, is where we have been taught different things and I'd like to know what you think and on what you base that.
I was looking at the often quoted UNM (I think) study suggesting that if you kept the battery in the top 10 % you could expect at least 6,000 charges.
if you use the top 20 % then you only can expect 4,000 charges.

It sounds like you are saying it should be more deeply discharged at times. So, how often do you think it should be more deeply discharged and how deeply are you thinking?
Has anyone studied this?

Lastly, do you have a source of EDTA for batteries. Have you found that helpful when they get older?

Thanks

mark andrews wrote:
Next, however, is where we have been taught different things and I'd like to know what you think and on what you base that.
I was looking at the often quoted UNM (I think) study suggesting that if you kept the battery in the top 10 % you could expect at least 6,000 charges.
if you use the top 20 % then you only can expect 4,000 charges.

It sounds like you are saying it should be more deeply discharged at times. So, how often do you think it should be more deeply discharged and how deeply are you thinking?
Has anyone studied this?

Lastly, do you have a source of EDTA for batteries. Have you found that helpful when they get older?

Mark, there is a critical flaw in your thinking there. After you have been off-grid for over a decade you learn that your true cost in batteries is in how many kWh they store and deliver back to your system over their life. Not in how many cycles you get, or how many years they last. It is actually better to size the batteries a little on the smaller side and work them harder - cycle them deeper - for best efficiency and least cost/kWh. We have a fairly large battery here, but it can only carry our normal loads for one day from 100% to 50% SOC with no incoming power (58 kWh theoretical capacity - 24 kWh to 50% DoD - 11.5 kWh to 80% DoD = 35.5 kWh useable capacity in actual power delivered to the load).

Surrette has several white papers on cycling deep cycle batteries and they recommend minimum 50% DoD at least once a month for batteries that are not being adequately cycled. According to Surrette, deep cycling "cleans" the plates by exposing new active plate material that otherwise gets hard coated over by lead sulfate that collects on the grids in inactive cells due to stratification of the electrolyte and not enough chemical reactions taking place in the battery to keep it healthy.

The brand doesn't matter - there has been no changes in how lead-acid batteries work in over 150 years.

The other thing is that amount of "charges" you get vs what the battery has for remaining capacity are two different things. That's why I would recommend a deep cycle amp-hour test on your batteries if they have been inactive for a long period of time, and not being cycled.

Jamie Surrette says FLA batteries are a "use it or lose it" type of thing - they age and die regardless of whether or not you use the battery to its full potential. The ONLY way you will get 20 years out of those batteries is if you need only 10% of their capacity. As they lose capacity over time you will be able to use them beyond the point where they get to 50% of their original capacity (considered end-of-life) if you shallow cycle them. But you will spend more on batteries over the long term than you would if you buy the bare minimum, work them hard, and replace them more often - AND by working your batteries harder you are working with a fresh set of batteries more often that have more capacity for heavy loads.

Instead of buying a couple new 1300ah 24V forklift batteries you could've bought four Rolls 12CS11P's for $4400 bucks, work the snot out of them and they'll still last 10 years. The CS plates in the 5000-series Rolls batteries are considerably heavier duty than forklift battery. Forklift batteries often have tubular grids and are more prone to stratification from RE chargers that don't put out enough power to properly charge one. The 5000-series Rolls is a dual container battery with "jars" just like your forklift battery, and you can replace individual "jars" if one goes bad over time. The 5000-series Rolls batteries have sailed the Atlantic in fishing trawlers and yachts for close to 30 years and they are THE only kind of batteries most boat captains will buy for their boats, where having a battery failure at sea is not an option.

Edit:
Mark, I forgot to comment on this:

mark andrews wrote:
Lastly, do you have a source of EDTA for batteries. Have you found that helpful when they get older?

Frankly, I don't know of any manufacturer that recommends using it. The reason is because it does not work. The active materials (lead and antimony) in your battery change physical form during charge/discharge. As the battery ages, regardless of whether it is used or not, you will get growth and distortion of the grids, and shedding of active grid material into the electrolyte where it settles in the sump**. Once the active material has fallen out of the plates, it cannot be restored into position by any chemical treatment.

A lead-acid battery, in many ways, is like humans. It's going to age and die no matter what you do to try and prevent it.

** I mentioned this above because this is going to be a serious problem with your shallow cycled battery. You absolutely MUST absorb that battery for the correct time during a charge or you will not get adequate electrolyte mixing in the tall cells of a forklift battery. Cycling to only 10% DoD means that if you absorb for the proper time, you are going to severely over-charge the battery and cause excessive grid erosion. The process of discharge causes sulfur in the electrolyte to combine with the lead on the negative grids and form lead sulfate. This causes the electrolyte to become less dense (loses specific gravity). Charging the battery reverses the process and puts the sulfate back into solution in the electrolyte.

This can all be done at low voltages below the point where the battery starts to gas. But the reason a proper charge cycle uses higher voltage is to force a minimum current rate of C/10 (at the 20hr rate) into the battery, which causes more rapid chemical reactions to take place - and to remix the electrolyte so the heavier (more dense) electrolyte doesn't end up at the bottom of the cells and water at the top. You will permanently damage a battery in less than a year if you let it become stratified.
--
Chris

Chris Olson wrote:We have a fairly large battery here, but it can only carry our normal loads for one day from 100% to 50% SOC with no incoming power (58 kWh theoretical capacity - 24 kWh to 50% DoD - 11.5 kWh to 80% DoD = 35.5 kWh useable capacity in actual power delivered to the load).

The above quote is another thing that might throw some people off, who do not know how to calculate it. So if this confuses you, you can study the Peukert Effect, or Peukert's Law, starting here:
http://en.wikipedia.org/wiki/Peukert%27s_law

--
Chris

Chris Olson wrote:
Instead of buying a couple new 1300ah 24V forklift batteries you could've bought four Rolls 12CS11P's for $4400 bucks, work the snot out of them and they'll still last 10 years. The CS plates in the 5000-series Rolls batteries are considerably heavier duty than forklift battery. Forklift batteries often have tubular grids and are more prone to stratification from RE chargers that don't put out enough power to properly charge one. The 5000-series Rolls is a dual container battery with "jars" just like your forklift battery, and you can replace individual "jars" if one goes bad over time. The 5000-series Rolls batteries have sailed the Atlantic in fishing trawlers and yachts for close to 30 years and they are THE only kind of batteries most boat captains will buy for their boats, where having a battery failure at sea is not an option.

I have been speaking to Steve at GB Batteries ALOT today. He was extremely helpful. He even tried to help me revive my dying battery, but alas, it is beyond saving. I truly appreciate all of Chris' feedback; he clearly knows what he is talking about after reading his posts on various forums however I'm not sure i understand why a Rolls 5000 is better than a GB battery. At least by looking at the plate thicknesses, the GB battery has positive plate thickness of .270" and negative plate thickness of .185 for the 12-85-15. The Rolls 6-CS-25P has plates of .260 and .180 respectively. Am I missing something? I know they are different AHs, does that matter for thickness? Also, the GB rep was insistent that they use plates, not tubes as Chris has indicated before.

Thank you,
Josh

Looking for battery recommendations for a small (60W) setup. Just getting started with solar and wondering if a deep cycle marine or golf cart batteries would be suitable for a newbie.
Thanks.

I would go with a golf cart battery before the marine type. They'll likely be a little more expensive, but much more robust (more forgiving of abuse). Good place to start IMHO.

hello all. I thought I would weight in on this one.

First, I am an electric forklift operator, and do have too say that the battery in my truck is taking a real beating. Not watered enough, discharged right down too 1 % charge - until the truck stops lifting . . and so far it's 18 months old and still going - basicly being worked 24/7 everyday - charge / rest / go again . . . do I say forklift batteries are the best . . I don't know... but they can crank out the power . . .

Second - a few of the guys are really pumped up about the new telsa battery - apparently you can get a battery that powers your entire house ! Problem is - when I ask em how they are going to put the power back into that battery , they just stare at me. . . - you have to be able to charge that battery back up in a reasonable amount of time, it you are not making enough power too charge the battery after you use it - your going to kill it.

third - I don't think anybody has said this so far, so i will . . . stick with a set of cheapo batteries at first . . if you go out and buy the above mentioned 4,000 $ battery, and it takes you 6 months too kill it . . . your out 4,000 $ . . on the other hand, if you buy some cheapy batteries from costco or some other place, for 2,000 $ and still fry em . . you have half the $$ lost . . I have also heard that if the batteries stop working for you, within a certain amount of time they are under warranty . . you return em and get a new one . . (so I have heard) , , , I am a newbie too solar as well, and I am getting cheapy batteries just for that reason . . .

Just my thoughts on this.

Oh ya, Arizona Wind and Sun Rock's ! They have a solar power forum over there and they are a great help.