# Utility vehicle conversion - battery choice



## pbiebach (Jun 29, 2010)

I am in the process of converting an mule utility vehicle see link,
I will probably be using a motor such as the K91-4003 or SEPEX D&D ES-32C-7 48-72VDC and am trying to decide on a battery choice.

the vehicle is used around a farm and is not required to operate at high speeds on a road, so range in Km is not really a relevant number low end torque and reliable low speed (under 35 km/h) operations are.

I'm looking for recommendations as to what batteries I should be looking at.

Can I use 12 V to minimize the # of batteries or is 6 volt required. 
so far I am looking at Trojan T105s or similar US batteries

I'm hoping not to spend much more then 1000 $ on batteries

any insights are much appreciated.

thanks, 

phil


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## dimitri (May 16, 2008)

pbiebach said:


> I'm hoping not to spend much more then 1000 $ on batteries


The real question is HOW OFTEN are you going spend less than $1000 to keep replacing those Lead Acid batteries.

LiFePo4 has a higher sticker price, but cheaper than Lead in a long run and has huge technical advantages.

For a small utility vehicle like that , LiFePo4 pack cost should be reasonable, but of course depends on how tight your budget is.


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## juddmeyers (Jul 14, 2010)

Trojan T-1275 will save you some batteries over the 6 volt, as it is a 12, but the 82 pound weight vs. 62 for the T-105's means you won't save much on weight.


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## ewdysar (Jun 15, 2010)

juddmeyers said:


> Trojan T-1275 will save you some batteries over the 6 volt, as it is a 12, but the 82 pound weight vs. 62 for the T-105's means you won't save much on weight.


Almost all lead-acid have similar energy density (Wh/lb.), +/- 10%. So a pack with a lower capacity weighs less, 6V, 8V or 12V doesn't make much difference.

Eric


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## pbiebach (Jun 29, 2010)

thanks for the replys, 
how much capasity will I need, I was thinking about 100 Ah actual use so the 185 rating for T-105s would keep me from deep discharges.

How do LiFePo4batteries compare, how many Ah rating will i need?


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## ewdysar (Jun 15, 2010)

pbiebach said:


> thanks for the replys,
> how much capasity will I need, I was thinking about 100 Ah actual use so the 185 rating for T-105s would keep me from deep discharges.
> 
> How do LiFePo4batteries compare, how many Ah rating will i need?


Lithium batteries can be regularly be discharged down to 75-80% while maintaining a lifespan in the thousands of cycles. So for 100A usable, you would want about a 125Ah pack.

They do cost 3-4 times the cost of FLA cells per Wh, but only about twice the cost of AGM. Since you can get away with a smaller pack, the cost gets even closer.

Eric


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## vpoppv (Jul 27, 2009)

You need to sit down and give serious consideration to how far you will go and how much use you need to get. I'll give you my example: I only need to go 1.7 miles. I knew this before I started my conversion. I looked around at all the other conversions, and listened to a lot of advice, and started off with 6 big ol' 12v group 29 deep cycle marine batteries. I got my 1.7 miles allright, and then some! I've gone 6 miles before, could probably go twice that, but really, seriously only need 1.7 miles. Since then, I have reduced to much smaller group 24 batteries. They still easily get me my 1.7 miles. I am considering going to lawn mower batteries! That's a LOT of lead to be carrying around if you have no intention of using it. I'm not saying you don't need 6 volts or Lithium, just saying that you should fit your pack to the use it will receive. Going too big is heavy, inefficient, and stresses components unnecessarily. Going too small will give you poor performance and short lifespan.


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## JRP3 (Mar 7, 2008)

Take a look at my 6x6 conversion with 4 12v 65Ah Odyssey AGMs. I didn't want floodies splashing around in an off road vehicle so I went with more expensive AGM's. If I did it again now I'd go with 60Ah lithiums. I can go at least 6 miles, but I just use it around my property to drag logs and haul stones and dirt and have never come close to running out of charge.


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## Duxuk (Jul 11, 2009)

With 185Ah floodies you won't get 100 useable Ah in the likely time frame in which you will be using the vehicle. My 72V pack gives 62Ah in one hour but you can't use all of that. Using more than 40Ah will stress the batteries and show up the imbalances between individual batteries. I have done >26 miles but for battery life I'm going to keep it below 15 miles. If I only do 10 miles I can go as fast as I like with no "range anxiety"!

My pack is 6 12V 110Ah Elecsol carbon fibre floodies (1000 discharges to 80% DOD) They cost me £600 and were custom built. The standard versions give 47Ah. 

Elecsol now make AGM carbon fibre (see Tayna batteries website). They are more expensive, have a lower one hour rate but can be run flat >1000 times!

Andrew.


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