# Are deep-cycle batteries the same ones used in photovoltaic systems ?



## dtrip (Dec 12, 2012)

For example, those are for photovoltaics: 
http://translate.googleusercontent....-225ah&usg=ALkJrhi5RnceHiIpMKcCgKIrbrHB5cUpnQ

(it uses Google Translate for automatic translation, so don't take everything it says literally) 

Are those good for EV's too ? 


If yes, then how are they used in an EV, since they have a rather low voltage (12 - 24 V). Perhaps join many of them in series to create, say, the 96 or 120 Volts an electric motor requires ? Is that how they could be used ? 

Sorry if the answer is no  

Thanks
Dimitris
Greece


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## Ziggythewiz (May 16, 2010)

Yes, PV uses deep cycle batteries. No, they're usually not the same as used in EVs, but they can be. PV usually needs longer life, low cost, and low amps. EVs need high amps, low weight, and try to maximize the others.

No EV battery can run a car by itself. They all need strings of batteries to get useful voltage. A typical lead EV will have 10-24 batteries while a lithium car will have 38-60 cells or more.


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## dtrip (Dec 12, 2012)

Thanks for your reply! 

Yes I understand what you mean. The batteries are 12 - 24 Volts, too low for running a car motor. 

[1] Is there some website/brand name selling deep-cycle batteries for cars ? So I can see what characteristics we are talking about ? Also for motors ? 

[2] Some guy I was talking to yesterday, insisted that if I wanted to use deep-cycle batteries, a controller is not enough and that it would also require an inverter. Is that true ? What does the inverter got to do with anything ? I mean, does the controller actually care what type of battery is feeding him ?


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## Ziggythewiz (May 16, 2010)

[1] Most people using deep cycle (lead) batteries are using golf cart or similar. There are others I've heard of buy they're usually way too expensive.

Lots of different motors out there. Kostov is a popular brand in Europe.

[2] An inverter lets you use an AC motor. Most of us use DC motors because it's typically cheaper. There are no AC batteries, so you're feeding either your controller or inverter with DC either way.


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## dtrip (Dec 12, 2012)

Thanks alot that's very useful, 

Why don't they mention the maximum Amperes that batery cells can sustain ? 
They only mention Ah and Volts, but is this enough ? 

For example, suppose I connect in series twenty 6V golf cart batteries, and make up 120 Volts. Suppose I connect a 10 kW motor there. That would draw 10.000 / 120 = 83 Amperes. Is that Ok ? What if I connect a 15 kW motor ? 20 kW ? Where does the smoke starts coming out ?


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## Ziggythewiz (May 16, 2010)

It depends on the battery. Many lithium batteries will tell you how much current it can draw in burst (3-10 seconds) or continuous use.

Most lead batteries will tell you in cold cranking amps (CCA) but GC batteries may not say because that's just not expected in typical use.

What a battery's limits are depends on the specific battery, and would only be determined based on maufacturer specs or testing.

83A should be fine for any golf cart battery.


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## dtrip (Dec 12, 2012)

Ziggythewiz said:


> 83A should be fine for any golf cart battery.



Gee you are really encouraging me here ! 

You think I could do away with eight of those in series ? 
http://batterypark.gr/prod.php?pr=265

Thats 8x12 = 96 Volts, for a 10 kW motor its about 100 Amps, would that be Ok ? I tried the Trojan website also, it does not mention max Amperes. 

Is the capacity they mention their total capacity, or the one I can actually draw without problems ? 

10 kW is my maximum motor possible (Im researching for a lightweight two-seat trike. It will be too fast if stronger).

Gee, really thanks man, you have already helped a lot

Dimitris
Greece


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## dtbaker (Jan 5, 2008)

for a go-kart or anything where there is a chance of tipping... you want to avoid any chance of getting acid on your humans! Do not use flooded lead acid batteries unless you do a VERY good job of enclosing them in polypropylene (acid proof) box. You should consider using AGM deep-cycle batteries even though they are more expensive and won't last as long.

You eliminate all hazard, lower weight, and get much longer life with Lithium, but it costs more up front.....


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## dtrip (Dec 12, 2012)

Thanks for your suggestion. By AGM you mean GEL type ? 

Also, could you name some good brand of Lithium batteries ? Or manufacturer ?


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## Ziggythewiz (May 16, 2010)

I wouldn't bother with AGM, Trojans, or any other expensive lead batteries. Those are likely nearly as much as lithium, which will be far lighter and last much longer.

Sinopoly and CALB are good brands, you probably want 60AH or larger. For 96V you need 30 cells, should be ~$2200.

If you really only need 10kW max you could even just use 40AH cells, so $1500, but your range would be lower.


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## Sunking (Aug 10, 2009)

Well I am going to chime in here and take some heat. But with 30 years in battery plants, Solar, ect I have a different POV.

*NO THEY ARE NOT THE SAME despite what others will tell you.

*In the Lead Acid Family there are 3 categories being *SLI* (Starting Lighting Ignition), *Hybrid* (Marine, RV, Golf Cart, EV), and *True Deep Cycle*. 

** SLI Batteries* are just what they imply. A battery that is designed to crank an engine and get it started. They are constructed with multiple thin spongy plates to provide maximum surface area which lowers the internal resistance as low as possible. Low resistance means it can deliver very high short burst of current with minimum voltage sag or voltage drop. That is great for starting engines, and then recharged very quickly with high amounts of current from the alternator. It is exactly what your vehicle needs, but sucks for RE and EV applications. If you try to cycle them, those thin spongy plates dissolve and end up in the bottom of the battery jar in 100 or so cycles or less. DO NOT USE SLI batteries for RE and EV applications except in an emergency. Enough said as you should get the point. 

** True Deep Cycle Batteries* are exactly opposite of SLI batteries, and generally the best choice for everyday use in RE applications, and a POOR CHOICE for EV (OK in Ev for 12 volt accessory equipment). They have fewer but very heavy thick smooth plates made to last a long time or up to 4000 cycles if discharged no more than 20 to 30% before being fully recharged immediately. The trade-off is they have limited discharge and recharge current rates. If you discharge then to fast, or too high of a rate, they will have excessive voltage sag or voltage drop. They should not be used in EV applications for this reason other than 12 volt accessories. Any True Depp Cycle battery WILL NOT HAVE a Specification for CCA, MCA, or RC. They will only be specified with a Amp Hour Rating at various discharge rates in Hours. 

** Hybrid Batteries* are useful in some RE, and most EV applications. Like the name implies they are a cross between SLI and True Deep Cycle battery. They have fewer thicker plates than SLI batteries to obtain some deep cycle capability, and lower internal resistance for decent high current charge/discharge rates. However the plates are not as thick and heavy as True Deep Cycle batteries. So what you get is trade-offs.

They can deliver/take higher discharge/charge currents than True Deep Cycle, but not as much as SLI batteries. On the other hand they do not have the high number of cycles as True Deep Cycle batteries. For the FLA hybrids you can discharge them as high as C/4, and some cases C/2.

AGM hybrids are extremely expensive and resemble SLI batteries more than True Deep Cycle. They are used in UPS systems, Golf Carts, Floor machines, and *Electric Vehicles* where moderate amounts of high current is required with some fair cycle life. Hybrid AGM's have very low resistance and can take a C/1 or higher charge\discharge rates. The downfall of them they only have 300 to 700 cycles in them in most cases, and should never be discharge to less than 50% DOD. Hybrids are best used in RE systems that are infrequently used with high discharge rates like Emergency power and UPS systems, or in EV's and Golf Carts.

The Hybrids come with Marketing names like RV, Marine Deep Cycle, Golf Cart, and on. The dead giveaway is in the Specifications because they will have rating like CCA, MCA, and RC in addition to the AH spec. If you see a battery claiming to be Deep Cycle and has a RC MCA, or CCA rating; It is a HYBRID.

Now I will give you two indisputable examples. Everyone knows the Trojan T-105 right? Well the T-105 you know of is a Hybrid Golf Cart Battery. But did you know Trojan also makes a True Deep Cycle T-105RE? Check it out for yourself. The T-105RE is heavier in weight because it has heavier thicker plates. A whole 5 pounds more lead.

Need more proof?
Trojan L16P
Trojan L16RE


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## Sunking (Aug 10, 2009)

dtrip said:


> Thanks for your suggestion. By AGM you mean GEL type ?


No they are not the same. Both are lead acid batteries. AGM = Absorbed Glass Mat. Never Ever Use a Gel battery for any high current applications period. 

If you are going to use a lead acid battery in an EV AGM is the way to go because they have very low internal resistance which means they can deliver very high discharge currents without excessive voltage sag. They can also be charged very quickly.

But take note not all AGM's are alike. Some are SLI, others Hybrid which is what you would want for an EV, and others are Deep Cycle which you do not want to use for an EV.


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## Zappo (Sep 1, 2011)

Sunking, So 30 years of background with batteries makes you some kind of battery expert? 

Oh wait, it does!

Great information. Thanks for sharing.


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## Sunking (Aug 10, 2009)

Zappo said:


> Sunking, So 30 years of background with batteries makes you some kind of battery expert?
> 
> Oh wait, it does!
> 
> Great information. Thanks for sharing.


You are welcome, but not sure I would say expert. I have worked in the Telecom & Electric Utility industry most of my career up until 2003 when I got laid off. In that time from 1979 I built a lot of Telecom and Utility DC Battery Power Plants primarily with Lead Acid batteries. It allowed me to work closely with a lot of battery manufactures.

After being laid off I started my own biz, a Design/Build firm and our clients are the Telecom and Utility sectors doing the same thing I did before. When I did that I got the opportunity to build a lot of Solar Battery plants for cellular Telephone companies which use lead acid batteries. 

So for LA family I have a lot of experience with, and even dabbled with NiCd, NiMh, and NeFe a bit. I have a healthy interest in EV's. I do not own a EV, but I do own a commercial NEV, and a custom built racing Golf Cart. Yeah I know that sounds strange having a racing Golf Cart but it does have a 60 volt LFP 100 AH battery pack. It goes about 40 mph which is not real fast, but scary fast for a golf cart. It will pop wheelies, burn rubber, climb a tree, or pull cars out of a ditch. It has some torque.


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## dtrip (Dec 12, 2012)

Hey thanks guys , it is very nice of you to help me out, especially Sunking.

However I did some research last night and it seems that lithium is the way to go. Although much pricier, it is much lighter and can be discharged more. 
For me, pros outbalance the cons (=price). I thought Lead-Acid could do better, but it is just too heavy for my lightweight vehicle. I raised my budget from 2000 Euros to 4000 Euros. 

I am opening another thread about my project. 

You have been all of immense help.


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## Sunking (Aug 10, 2009)

dtrip said:


> Hey thanks guys , it is very nice of you to help me out, especially Sunking.
> 
> However I did some research last night and it seems that lithium is the way to go. Although much pricier, it is much lighter and can be discharged more.
> For me, pros outbalance the cons (=price). I thought Lead-Acid could do better, but it is just too heavy for my lightweight vehicle. I raised my budget from 2000 Euros to 4000 Euros.
> ...


Well what you are discovering is Energy Density as it it is the most important spec of an EV battery. A LA battery only has about 30 to 45 wh/Kg and can only be discharged to about 50% DOD or else very short life. Lithium has about 100 wh/Kg and can be discharge to 80% DOD without significant cycle life reduction.

What all those numbers mean is a 50 pound Lithium battery in a EV can do the same work as a 150 pound LA battery.


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## rmay635703 (Oct 23, 2008)

Sunking said:


> No they are not the same. Both are lead acid batteries. AGM = Absorbed Glass Mat. Never Ever Use a Gel battery for any high current applications period.


I am using greensaver batteries (gel) in a high current application, but they are a tad unusual as gel goes.

10k on the clock so far. Winter voltage sag sucks though.


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## McRat (Jul 10, 2012)

Thanks SunKing. That was a great post.


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## Sunking (Aug 10, 2009)

rmay635703 said:


> I am using greensaver batteries (gel) in a high current application, but they are a tad unusual as gel goes.
> 
> 10k on the clock so far. Winter voltage sag sucks though.


!0K what? Cycles, hours what? Got a link to the battery?

They very real issue of Gel batteries is they are extremely sensitive to being over charged, and there slightly lower voltage profile. Most are limited to a max C/20 charge rate which is not practical for most application. Certainly not for an EV and completely useless in a Renewable Energy application.

If charged too quickly or over charged dries out the gelled electrolyte which forms cracks and voids. Think Jello. Those cracks and voids are permanent damage and it accumulates. You can literally destroy a brand new battery with 1 single charge. 

Granted there are some Gels that can handle larger charge currents, but due to the expense (almost 2 or 3 times more than FLA, and even more than AGM) lower voltage profile, and limited cycle life I advise leaving them on the store shelf. 

Only real application niche for Gels is Emergency Egress Lighting or Alarm systems where they remain on a Float Charge with limited initial current of about 13.1 to 13.2 volts on a 12 volt nominal battery. Normally with a FLA and AGM is up around 13.6 to 13.8


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## dtrip (Dec 12, 2012)

Sunking said:


> Well what you are discovering is Energy Density as it it is the most important spec of an EV battery.


Yes, especially for a lightweight vehicle, it becomes critical. 

I was aiming at a two-seat vehicle for 2000 Euros. --> no way man ! 

Now I changed my requirements to single-seat vehicle for 4000 Euros.

I hope I wont have to change to half-a-seat vehicle for 8000 Euros !!!


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