# Why pay big bucks for batteries for my go cart?



## strantor (Sep 4, 2011)

I'm planning a 48V go cart project. I can get deep cycle marine batteries at walmart. they are about 65lb each (est.), 12V, 110ah, 875cca, for 81$ each. I would need 4 of them in series, so:
260lbs
48V
110AH
875A max
324$

then there's these LiFePO4 batteries for 68$ each. 3.2V each, so I would need 15 in series, but they're only 40ah, so I would need 3 string of 15 in parallel to get the same capacity as the marine batteries. 45 total cells would weigh 150lbs and cost 2,728$

is 90lbs weight reduction really that important to some people that they would spend 2400$ extra just to acheive it? or am I not aware of some other reason why the LiFePO4 batteries are far superior than the marine batteries?
please, enlighten me
Thanks


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## Ziggythewiz (May 16, 2010)

For a go-cart I don't think it matters much. For an EV marine DC's will only last about a year but in a go-cart you'll probably hit shelf-life (3-5 years?) before hitting cycle life (~300).


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## major (Apr 4, 2008)

strantor said:


> I'm planning a 48V go cart project. I can get deep cycle marine batteries at walmart. they are about 65lb each (est.), 12V, 110ah, 875cca, for 81$ each. I would need 4 of them in series, so:
> 260lbs
> 48V
> 110AH
> ...


Hi stran,

I did a competition go-kart last spring. Used 48V of 96 Ah Li battery. That was good for about 70 laps (about 1/4 to 1/3 mile lap). And those were fast laps. There was another 20 laps in there. We pulled him in and swapped battery in a pit stop because he was slowing a half second a lap. 

I think you'd be good with 60 or maybe even 40 Ah. Depends on what your goal is.

That much extra weight on a go-kart is huge. And with the Pb-Acid, you will never get the full Ah rating at load due to Peukert. Maybe count on 50% of rated Ah. With Lithium you get to use almost all of it 

But on the downside, you'll need a BMS with Lithium  Extra cost and complexity.

People don't like this advice, but here goes. Build your cart and use cheap small lead-acid batteries. Like U1 lawn tractor starting batteries. Like $20 each. Get the darn thing running. Measure the current and voltage as you drive it. Get a handle on what your power and energy requirements really are. Then strap on a couple of concrete blocks to simulate the extra weight of Pb. Then decide on the expensive battery. And if you go Pb-Acid, I'd consider AGM.

Regards,

major


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## strantor (Sep 4, 2011)

major said:


> Hi stran,
> 
> I did a competition go-kart last spring. Used 48V of 96 Ah Li battery. That was good for about 70 laps (about 1/4 to 1/3 mile lap). And those were fast laps. There was another 20 laps in there. We pulled him in and swapped battery in a pit stop because he was slowing a half second a lap.
> 
> ...


 No, I think that's good advice. Sounds like real world, "been there, done that" advice. valuable info, thanks!


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## Woodsmith (Jun 5, 2008)

Similar to my tractor.

I have 48v made up of four used Optima red tops sourced from the car breakers yard. Simon Rafferty got them for me. The yard sells them to him at £3 each and buys them back as scrap for £2 each.

So long as you check they have a good charge and capacity then you are good to go. The cost is so small that a few extra and some duds are negligable.


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