Batteries?? 7 6v vs 4 12v vs 6 8v

[wbhess]

I have a feeling I already know the answer to this question but, I have 7 6v batts that are a hair over 2 years old and in great shape (36v PDS upgraded to 42v ((xct48500 and admiral motb2)). My local shop is selling a set of 4 USED US 12v batteries that are 2017s for $400. I was considering going up to 48v eventually but dont have the $$ for new batteries. Any estimates on what increases/decreases I'll see from doing the 7 6v to 4 12v swap? I'm assuming I'll get greater speed/torque but lower run times.

I think new, these batteries are $760 from the same place with cores..I have 4 12v toasted cores I can exchange with.

I like the idea of 4 12v over 7 6v (saves over 100lbs)

But I also like the idea of the extra run time with extra battery mass.

I know the best bet would be 6 8v but I'm just considering all options.

Most of my riding is loaded with 4-500lbs of ppl, kids, and dogs on paved roads wit the occasional hard gravel/grass/sand/hard gravel.

Cart is slightly lifted (3" spindle with 20x10-12 A/T tires)

[LukeL]

For me, the 6 8v would be the obvious choice. That configuration offers a lot more run time than 4 12v, and it will fit in your battery tray without modification.

[Roy Gurley]

6 8 volt for would be the ONLY WAY TO GO! With the 12's alot less run time!

[wbhess]

Do you guys think I would get more or less run time with 6 8v or 7 6v (given the batteries are of similar grade) ... there is probably greater mass with the 7 6v...not sure how much difference battery mass makes

I thought going from 7 6v to the used 4 12v would be beneficial because I could likely sell my 42v pack with 42v charger for significantly more than the cost of the used 48v pack and 48v charger. I didnt know how the run time/speed/torque would compare to my current pack

[orangeman6]

Where’s Johnnieb? 😀. He’ll give a very thorough answer, but I think you need to look up the capacity of both battery options to get a clearer picture of the pluses and minuses.

I believe you would see a 14% increase in speed and torque with the 48v pack. However, you are going to have a decrease in drive time. You read on here often about guys changing rxv’s from 4x12 to 6x8 because of the increased capacity. How much drive time you lose depends on the health of your current pack relative to the 4x12. You also have the issue of not knowing the true condition of that 48v pack.

[kernal]

Thoughts: Buying used batteries is very risky (financially) unless you have detailed info on their exact age,use and servicing. 12v batteries from "17 could be just short of 3 years old this month. Average life span of the 12vs is 2-3 years as reported on this board. Those batteries are worth $200 at best IMO and I wouldn't buy them in any case.

You have the best combo for a PDS cart now as reported by others here (because the stock motor is still happy at 42v.) Going to 48v should give an additional 15% speed and torque (mathematically).

What I would do: Keep what you have. Every time you service your batteries, pay yourself $10 (maybe $20 since your current pack is 2 years old) or so and when your current pack craps out you'll have the money or close to it for a quality 6x8v pack if you want to go to 48v then.

edit: AND what orangeman said

[cgtech]

Run from used 12v golf batteries. Their age & lower capacity will have you regretting the change as soon as the joy of the slight speed boost wears off. In your case, you would also find the voltage sag under load would be much worse than you have now. I cant think of any scenario where I would suggest converting TO 12v batteries, but many reasons exist to convert Away From 12v's.

[JohnnieB]

The best case scenario for the 4x12V will be: Fun while they last, but they won't last long. And they won't last long in the distance of travel on a single charge or the number of months before they'll have to be replaced.

As Jenny said: "Run, Forest, Run"

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Attached is a chart show the storage capacities of 36V, 42V and 48V battery packs made up from various 6V, 8V and 12V batteries.

If the 6V batteries in your 42V pack are 225AH, it has about 9.5kWh of storage capacity and if the US Battery batteries are model US-12V XC they are 155AH, so the 48V pack would have about 7.4kWh of storage capacity, or about 22% less storage capacity. That means the cart's range would drop by at least 25% and since the 12V batteries are already 2 years old (half or more of their nominal lifespan), the loss will likely be greater.

[wbhess]

Thanks everyone for the replies and talking me out of the used batteries. And thank you JohnnieB that mathematical explanation. It was exactly what I was looking for.

Perhaps I missed it but would 6 8v batteries yield better range than my 7 6v pack? I think my batteries are 220ah..maybe more, I havent looked in a while.

Acutally, according to the chart, if I had a 48v pack using 6 8v Crown CR-190, I'd have less kWH than a 42v pack using 7 6v CR-225? If I'm looking for greater range, should I stick to the setup I have? Will going to 48v only increase speed and torque?

[JohnnieB]

Originally Posted by wbhess

Thanks everyone for the replies and talking me out of the used batteries. And thank you JohnnieB that mathematical explanation. It was exactly what I was looking for.

Perhaps I missed it but would 6 8v batteries yield better range than my 7 6v pack? I think my batteries are 220ah..maybe more, I havent looked in a while.

Acutally, according to the chart, if I had a 48v pack using 6 8v Crown CR-190, I'd have less kWH than a 42v pack using 7 6v CR-225? If I'm looking for greater range, should I stick to the setup I have? Will going to 48v only increase speed and torque?

Yes, going to 48V will only increase speed and torque. Range and lifespan are determined by storage capacity.

A 48V pack of Trojan Ranger 160 (8V-204AH) or US Battery US 8VHATB XC2 (8V-205AH) will have 9.8kWh of storage, which is a bit more than a 42V pack of 6V-225AH batteries (9.5kWh), but those are super-premium 8V batteries and difficult to find as well as expensive.

A 48V made with eight of the highest capacity 6V batteries will give the greatest range, but are tricky to fit under the seat in a sepex drive cart and next to impossible in a series drive cart, so most people put one or two batteries in the bag well when they go the 8x6V route.

When I built my cart, a 30 mile range was my goal, I wanted to keep all the batteries under the seat and I had tiny tires (17" tall), so over revving the motor was a possibility and I went with seven 245AH 6V batteries for a 42V - 10.3kWh pack.

Of course, your range on a 10.3kWh pack won't be the same as mine since all carts are different.

That was in the DCX era and the DCX didn't have RPM limiting like the XCT does, so over revving is no longer an issue for sepex drive carts. (I still managed to explode the stock PDS motor with 42V and a DCX controller. )