01-07-2010, 11:44 AM | #1 |
Not Yet Wild
Join Date: Dec 2009
Posts: 6
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Battery Questions
Fairly new to forum and have been doing as much reading as possible before chiming in with questions.
What are the PRO's and Con's on a 36V or 48V system if 12V batteries are used instead of 6V or 8V? The reasons for my questions are this. I am a sound GURU and can come up with some good sized speaker enclosures (ie subs) to mount in the battery compartment if batteries were consolidated (ie 6V or 8V converted to 12V). The more I learn now, the better off I will be when my build begins (Actively looking, BTW). |
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01-07-2010, 04:44 PM | #2 |
Gone Wild
Join Date: Oct 2009
Posts: 486
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Re: Battery Questions
Well it is pretty easy once you understand some basic. Motor speed or RPM is directly proportional to voltage, and torque is inversely proportional to voltage and dependent on the current.
So just going from 36 to 48 volts without changing the motor or controller will give you more speed, but no more torque. The only way to get more torque is by using a higher amperage controller. DC motors are kind of funny. The highest torque (and current) is at 0 rpm's and decays pretty much at a flat line as RPM's go up. RPM's go up as voltage rises and current falls. So what you end up with maximum power in a DC motor occurs at half voltage and RPM. As RPM goes up from that point, current, torque, and HP fall. Now the next thing to look at is battery capacity vs range. A battery is rated in Amp Hours and Voltage. If you multiply the AH by the voltage will give you watt hours. Watt hours is directly proportional to your range. More capacity in watt hours = more range. Pretty simple. But like every thing there is a catch in life, there is no free lunch. A typical 36 volt golf cart uses Trojan T105's They are 6 volts at 225 AH So the capacity is 6 batteries x 6 volts x 225 AH = 8100 watt hours. A lot of folks that go from 36 to 48 volts use 8 volt batteries so they need 6 of them to make 48 volts. The battery that fits that bill is a Trojan T 875 rated at 8 volts @ 170 AH. So the capacity is 6 batteries x 8 volts x 170 AH = 8160 Watt hours or 60 watt hours more so you get a little bit more rand, about a block or two using 200 wh/mile as a efficiency figure. If you use 12 volt batteries say Trojan 1275 @ 150 AH you get 48 x 150 AH = 7200 watt hours which is quite a bit less. |
01-07-2010, 06:18 PM | #3 | |
......................
Join Date: Apr 2009
Location: FT Lauderdale FL.
Posts: 16,416
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Re: Battery Questions
Quote:
Well said ------- |
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01-07-2010, 06:42 PM | #4 |
Getting Wild
Join Date: Jan 2010
Location: Central MS
Posts: 98
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Re: Battery Questions
So the way to go would be a 48 volt system running 8 6 volt batteries right? Anyone done that? I'd sure like to know how to make them fit...
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01-07-2010, 06:53 PM | #5 |
Not Yet Wild
Join Date: Dec 2009
Location: Beaufort,SC
Posts: 55
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Re: Battery Questions
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01-07-2010, 07:01 PM | #6 |
Getting Wild
Join Date: Jan 2010
Location: Central MS
Posts: 98
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Re: Battery Questions
I bet. I doubt there is anyway to get them all in the battery compartment huh? Was it just wired through the body to that bag compartment or was something special done?
Is there any down side to this? I am ready for new batteries and this is something to seriously consider. Should give you 32% more runtime based on numbers above using a T105. Anyone here done this? |
01-07-2010, 07:03 PM | #7 | |
Getting Wild
Join Date: Dec 2009
Location: The Villages, FL
Posts: 144
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Re: Battery Questions
Quote:
6 x 8 x 170 = 8160 (old) versus 8 x 6 x 225 = 10800 (new) which looks like an additional 13ish miles. This is a handy formula to have to describe range. Thanks! |
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01-07-2010, 07:44 PM | #8 |
Getting Wild
Join Date: Jan 2010
Location: Central MS
Posts: 98
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Re: Battery Questions
Aj - Are you putting your 2 extra batteries in the bag compartment as well? Or something different?
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01-07-2010, 09:07 PM | #9 |
Not Yet Wild
Join Date: Dec 2009
Posts: 6
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Re: Battery Questions
Wow... I am glad I asked the questions...
I have not done my research on the OBC. Would the switch to qty of 8 6V batteries cause any conflicts with charging??? I can see where the golfer/ neighborhood cruiser would want the extra range. Next question... regarding battery life, would switching to 8 batts tend to extend battery life if maintained properly? |
01-07-2010, 09:11 PM | #10 |
Getting Wild
Join Date: Jan 2010
Location: Central MS
Posts: 98
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Re: Battery Questions
Hey Div - I'm gonna start another thread so the title will reflect what this topic has become. I want to know the ins and outs on how to do this as well.
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