# Lead-acid Battery selection



## dragonsgate (May 19, 2012)

yodahea said:


> Hi,
> I'm building an EV in Africa.
> I have successfully finished the mechanical part like fixing the motor to the transmission...
> Now I'm about to buy batteries. I can only find 12v lead-acid batteries in the market.
> ...


 With lead it won't be a thousand pounds anymore. Sounds like you are not running a large pack so lithium might be fit your budget. 12V batts will not give much range at all. 6V are better and the trade off would be 8V. If you must get lead and you can find them Trojan are the best LA's in my opinion.


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## yodahea (Feb 4, 2015)

Thanks for the reply. I am more confined to the use of lead-acid batteries due to their accesibility. So, the min amp-hour rating for lead-acid batteries with minimal acceleration and speed requirements (basically a car that moves around at parking speeds) is what I wanted to know.


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## Sunking (Aug 10, 2009)

If you have to use Pb, look for AGM, not gel, but AGM. FLA batteries have quite a bit of internal resistance compared to AGM making them a better choice for traction applications. Downside is AGM cost more and do not last as long as FLA. 

The other downside to any Pb only 50% the capacity is usable, and once you throw in Peukert correction factor that 70 AH battery you are thinking about is only going to give you at best 20 AH of usable capacity if even that. Pb batteries are just not made to deliver discharge currents in excess of 1C. Even C/2 is beyond their capability and for you that is only 35 amps on a 70 AH battery. I am afraid it is going to be a hot turtle that cannot go far.

I have no idea what voltage you are running but a modern golf cart today is 48 volts @ 160 AH, weighs 1000 lbs with batteries, goes about 20 mph at best (can go faster at the expense of range) with a range of 12 to 15 miles with new batteries.


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## major (Apr 4, 2008)

Hi yoda,

Well, you gotta do with what you can get. Recommendations:

1.) Buy from a reputable battery dealer who will stand behind the product and hopefully be able to assist you in a sincere manner rather than just taking your money.

2.) Test the batteries. Learn to test batteries for capacity primarily, but also internal resistance would be nice. This means a load test for a duration, not a simple voltmeter or cranking amp tester. Be able to use a repeatable test on each battery when new, and then periodically during the life cycle.

3.) Choose a battery which is a good value in your area. If you are looking for more than a couple dozen cycles, then it need be a deep cycle battery. I suggest perhaps you use a FLA (flooded) because it is more forgiving than AGM. Should you lose electrolyte the AGM is garbage whereas you can fill the FLA. Also then you can check specific gravity in the FLA. 

4.) Choose a lower cost option for the first battery set opposed to the high performance high cost option. With Pb-acid, we used to call it batterycide; the murder of battery through misuse and inexperience. 

Too bad you're forced into Pb-acid, but we all were years ago and made do. Lithium is sooo much nicer.

Good luck,

major

BTW, here's a Pb-acid test and install I did a few years ago. http://www.diyelectriccar.com/forums/showthread.php?t=78826


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## yodahea (Feb 4, 2015)

Thanks major, that was helpful.
I am starting a blog here on my car.
https://evafrica.wordpress.com/
I will keep you posted.
-Yoda


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## samwichse (Jan 28, 2012)

Ah, you should have put the blog link in your first post.

I always liked the Starlet... like a same-period Corolla with a foot chopped off of the body.


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## jumpjack (Sep 9, 2012)

A "road" EV requires an average of 150 Wh/km, but I suppose we can consider 80 Wh/km for your vehicle, which is the typical consumption of what is called a "neighbour EV".

You can consider approximately 1,3 km/h speed per each V of your battery; so, for "parking speeds" (max 30 km/h ?) you'll need a 24V system.
As "not a lot of range" I assume 30 km, hence 30x100 = 3000 Wh.

To build a 3000 Wh / 24V system you'll need 125 Ah split among some strings of 2 batteries each, hence I think *4 batteries rated 60Ah/12V* is what you need: 2 series of 2 batteries each.

4 batteries x 60 Ah x 12V = 2880 Wh


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## dtbaker (Jan 5, 2008)

yodahea said:


> Thanks for the reply. I am more confined to the use of lead-acid batteries due to their accesibility. So, the min amp-hour rating for lead-acid batteries with minimal acceleration and speed requirements (basically a car that moves around at parking speeds) is what I wanted to know.



if you are going to go with lead.... go with golf cart batteries. they come in 6,8,12v. There are plenty of 8v-200+ah flooded lead batteries available for cheap. Try getting some used ones from a golf course shop if you just need a cheap demo.


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## yodahea (Feb 4, 2015)

Thanks everyone for the recommendations. I read them all.
Unfortunately, I can't find Go cart batteries in Ethiopia, not many golf courses i guess.
Now, after a good search of the market, I have these three
(1) 12v *65A*h *deep cycle* lead acid batteries
(2) *100Ah* standard lead acid (*car *batteries)
(3) *150Ah* standard lead acid (*car *batteries)

I have the funds to buy any of those. (My system is to run at 72v, so I will need 6 of those.)
Which would you suggest*??*


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## dtbaker (Jan 5, 2008)

yodahea said:


> Thanks everyone for the recommendations. I read them all.
> Unfortunately, I can't find Go cart batteries in Ethiopia, not many golf courses i guess.
> Now, after a good search of the market, I have these three
> (1) 12v *65A*h *deep cycle* lead acid batteries
> ...


give your low range requirements, I would go for the 65ah 12v deep cycle. regular auto starting batteries won't last very long at all.... less than 500 cycles most likely. The deep cycles may give you 700 or so cycles if you maintain them well.


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## yodahea (Feb 4, 2015)

Thanks for the advice! If it will be a question of 500 cycles vs 700, I think I will put price and Ah first and then 'deep-cycle or not' second.


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