# What to look for when choosing a battery



## Coley (Jul 26, 2007)

For an EV, AH means distance, CCA means nothing, flooded AGM etc. mean what is the balance in your EV account.....


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## fshagan (Jun 4, 2008)

Are there differences in the number of discharges each type of battery can have? I've read some accounts that say flooded lead-acid batteries typically can take about 400 discharges, and that maintenance issues (not keeping the cells topped off with water in non-sealed batteries) can shorten that. That's over a year, but for a frequently used EV, not too much more than a year. 

AGM batteries are more forgiving of how they are installed, require no maintenance and are said by some to have longer life in a deep-discharge type of application. But if they don't really have that much longer a life, then it may not make sense to use them because of the higher cost.


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## adric22 (Jan 17, 2008)

I beat myself up for 2 months trying to figure out what kind of batteries to use. I looked into quite a few different kinds. Here are some of the points I discovered when looking at them.

AGM Batteries are good at high rate of discharge. Obviously, you don't have to worry about them spilling and can be installed in any orientation. However, I decided _not_ to go with them because they have poor lifespan (number of cycles they can take) and they cost twice as much as other kinds. Also they require battery balancers or individual chargers.

Lithiums are too expensive and very few people have used them. It is hard to find charging systems that work correctly with them.

NiMh is almost impossible to find and is very expensive.

Marine batteries are good at being deep cycled, but usually can't handle the high currents. So they usually have a very short life in an EV.

Flooded batteries seem very good at dealing with abuse, especially for a first-time EV converter. (Like I was) 

Eventually, I decided the most economical choice was going to be golf-cart batteries because they are tried and true and seem to work well in EVs. Unfortunatly, they are more difficult to install in the vehicle because of their size and they cannot be turned on their side. They have a decent lifespan compared to AGM, and are fairly inexpensive.

As for Amp-hours, how many you need will depend on your voltage. For example, a 72 volt system like mine I have 175 Ah and my max range is 20 miles. However, if I were running 144 volts, I'd probably be able to go with around 90 Ah for the same range.


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## favguy (May 2, 2008)

According to my Trojan battery dealer, golf cart batteries will last a very long time (5 to 6 years +) if you only ever discharge them to 50%, although discharging them to 70-80% will use them up in around 18 months


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## adric22 (Jan 17, 2008)

I've always heard about AGMs being a bad choice.. (One of the reasons I didn't use them) However. I found a guy on evalbum that has Orbital batteries in his.. I sent him an email and this was his reply:

"The Exide Orbitals have been in my car for over 6 years, They were seconds when I installed them a couple have lost capacity and were replaced 2 years ago. the rest have 90% of there original capacity and are still going strong."

So it sounds like they may be worthwhile.


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## favguy (May 2, 2008)

Exide orbitals do look to be a very good battery although they are very expensive. The only thing that counts them out for me is you can't get the huge Ah rating that you can from the big golf cart flooded batteries. But if you have a small range requirement they look quite good, and you have no maintenance to do!


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## major (Apr 4, 2008)

Coley said:


> For an EV, AH means distance, CCA means nothing, .....


CCA, Cold Cranking Amps, should tell you something about the power. The higher CCA, the higher the peak power from the battery. Of course, you can't believe everything you read, especially on a battery, so if power is what you're really after, get a sample of the battery and test it. But in my mind, CCA should relate to the battery internal resistance and therefore to the peak power.

Not a battery expert, but have used a few thousand.

major


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## ga2500ev (Apr 20, 2008)

major said:


> CCA, Cold Cranking Amps, should tell you something about the power. The higher CCA, the higher the peak power from the battery. Of course, you can't believe everything you read, especially on a battery, so if power is what you're really after, get a sample of the battery and test it. But in my mind, CCA should relate to the battery internal resistance and therefore to the peak power.
> 
> Not a battery expert, but have used a few thousand.
> 
> major


The only thing about CCA is that it's an attribute of starting batteries. The problem is that starting batteries are formulated to deliver a lot of power in short bursts. This is antithetical to EV use which generally required a long steady stream of power.

The bottom line is that any battery with CCA is probably a starting battery and should not be used. Look for deep cycle batteries.

ga2500ev


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## ww321q (Mar 28, 2008)

I have gel cell batteries and from what I have learned from reading comments from various places gel cell and AGM are very good EV batteries . BUT! care full charging is very important . If you charge at over 14.2 volts or at to many amps you will cook the battery . I think that is important with any battery . Regular lead acid batteries will take the most charging abuse but even then it will shorten their life . J.W.


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## ga2500ev (Apr 20, 2008)

ww321q said:


> I have gel cell batteries and from what I have learned from reading comments from various places gel cell and AGM are very good EV batteries . BUT! care full charging is very important. If you charge at over 14.2 volts or at to many amps you will cook the battery.


Sealed Lead Acid batteries only have emergency vents. If you vent the battery, it permanently loses power capacity. Overcharging will render them useless.



> I think that is important with any battery . Regular lead acid batteries will take the most charging abuse but even then it will shorten their life . J.W.


To a degree. Generally overcharging a flooded lead acid will boil off the water, which can be replaced.

ga2500ev


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## Coley (Jul 26, 2007)

I am running 4 used Gel, MK POWER batteries that came from a friends wheelchair. They are 2 and 3 years old, but still hold a charge well.
They are also only 53lbs each.

They can be recharged in 2 1/2 hrs with my use of only 25% of their power per 10 mile run. One hour will bring them back close enough for a 6 mile run.
Along with these, I am running one 95 AH LA and one MAXX 29 LA @ 125 AH.

I am in the second week of testing them (over 200 miles) and I am going with 2 more Gel when I get the funds.


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## ww321q (Mar 28, 2008)

Coley I'm very interested in what you are doing with your batteries . I've wanted to do testing on mixed sets and I also have 28 old gel cells that I want to use in my conversion. Keep us posted on any thing that you find . J.W.


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## Coley (Jul 26, 2007)

Well, I found out that the gel batteries can be charged with a regular charger, just so you don't go over 14.1 volts.

They also seem to charge faster with my 20 amp charger.

They also bounce back faster with only a one hour charge.


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## John (Sep 11, 2007)

The OP was looking for batteries that deliver "all out acceleration". So I'm guessing he's looking for a performance solution rather than range. This needs a high amperage discharge with minimal voltage sag. I'm no expert and I’m sure someone here can correct me if I’m wrong. I would think carefully selected AGM's would be the battery to deliver what’s required. They are not a good range battery because they don't like being discharged below 50% (were as deep cycle floodies are OK down to about 80% DOD) but from what I understand they can deliver very high currents with minimal voltage sag due to a good Puerkerts exponent. This would make them the performance battery choice in lead acids. Just to muddy the waters the other thing besides battery type that affects the available discharge current is battery size. Generally speaking batteries with a higher Ah rating can produce more amps. So you could use a larger pack of floodies to get your available current up but with that comes increased weight which as you know will negatively affect your cars acceleration.
The current limit of your controller will have a profound affect on the available acceleration. When you start your run the controller will cut the voltage in order to keep the amperage below its limit. The higher the current limit the higher the voltage before reaching that limit which means both volts and amps are higher giving a much fatter kW available for acceleration assuming amps aren’t naturally limited by the battery. With controllers like the Zilla from what I understand you can use battery bank voltages higher than your motor can tolerate and use the controller to limit the voltage at full throttle on the motor side. This allows you to trade volts for amps.


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## Bowser330 (Jun 15, 2008)

I acceleration is the focus then AGMs is the choice.

John Wyland used them before he switched to lithiums.


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## Qer (May 7, 2008)

John said:


> They are not a good range battery because they don't like being discharged below 50% (were as deep cycle floodies are OK down to about 80% DOD) but from what I understand they can deliver very high currents with minimal voltage sag due to a good Puerkerts exponent. This would make them the performance battery choice in lead acids.




Hm. Very stupid idea; add a string of AGM in parallel of a flooded string? Take 12 times 12 Volt AGMs and connect them in parallel with 25(!) 6 Volt flooded through a diode. That would give you 144 Volt for the AGM and 150 Volt for the flooded, but since there's a diode between them, the AGM's are disconnected from the circuit until you accelerate enough for the voltage for the flooded pack to drop until the diode opens.

The difference in about 6-7 Volts will also mean that when the lead acid pack is at 80% DoD the AGM's will still be at 50% DoD! Perfect!


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## Coley (Jul 26, 2007)

The mixed combination battery pack is doing very well.

I start out in the morning with an 84 volt reading. The pack has sat all night, as I recharge for 2 1/2 hours, right after I get home. The pack shows 79 volts as I leave the driveway.

I run to town and only use a small amount of volts @ 40 mph. (5 miles)

I get to town and have a 76 volts reading.

I voltage check all of the batteries and they all are within .08 volts of each other. 

Makes no difference what the AH rating is. The MAXX29 shows the same voltage as the the GELS and the 95 AH also.

On the load tester volt reading, they all show good charge....12.66 volts.

On the quick load test, the 95 AH and the 125 AH both show more power left , but that is to be expected.

None of the GELS get warm either running or charging.

Well satisfied so far. Now I am looking for enough batteries to put the rear pack in.


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