Share |

Results 1 to 16 of 16

Thread: 6 volt vs 12 volt

  1. #1
    Associate Engineer
    Join Date
    May 2011
    Posts
    6

    Lightbulb 6 volt vs 12 volt

    We have an electric golf cart that we use as transportation in the community in which we live. My question is this: which will give me more range, 8-6volt batteries in series for 48 volts or 8-12 volt batteries in series and parallel for 48 volts? I currently have the 8-6 setup, but want to improve the range if at all possible.

  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,045
    Hi,

    Really nothing to do with voltage since they are both the same at 48. It *is* all about Amp/Hours. Get the batteries that have the highest rated A/H with the physical size that will fit the available space. To a small degree, it may also depend on how many A/H the battery can discharge at a given rate without heat damage to the battery. Some batteries are designed for high output over short duration, some are designed for low steady output over a long duration. Some have long slow recharge cycles and others short and fast.

    Life is all about compromise and electric vehicle range is at the forefront of compromise. If it were as simple as battery configuration, then Chevy would be making vehicles with more than a 40-mile range.

    Dave
    Generally, I will not give you the answer to your question, but I **will** guide you into discovering how to solve this yourself.

  3. #3
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Location
    Rochester Pennsylvania
    Posts
    387
    You want to make sure you are using "deep cycle" batteries which will also have the higher amp/hour ratings dave mentioned.

  4. #4
    Associate Engineer
    Join Date
    May 2011
    Posts
    6
    Thanks, guys. The two batteries I am looking at are the US Battery 2200XC for the 6-v or the Optima Blue Top 34M or the D34M for the 12-v, leaning toward the Optimas for longer life, even though they cost more to begin with. I appreciate your input. Any opinions on my choices?

  5. #5
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,045
    Quote Originally Posted by corvettedreamin View Post
    leaning toward the Optimas for longer life
    Can't help with the battery choices, but are the optimas LiP or Lead Acid? If LiP, be very careful with the charger design and the charging cycles. Not all batteries are created equal.

    Also might want to check on their extended high load discharge curve. The golf cart with 4 people going up a long incline will generate some heat in motor and batteries. Lithium is in the Alkaline metal group, meaning it will burn on contact with oxygen. A split battery case could get exciting.

    Dave
    Generally, I will not give you the answer to your question, but I *will* guide you into discovering how to solve this yourself.

  6. #6
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Location
    Rochester Pennsylvania
    Posts
    387
    Definitely would not use the 34M...
    The "D34M" would work... The "D" = Deep Cycle. The 2200XC batteries are also deep cycle and made to be used in golf carts. The optima's should be a good bit lighter so your total load will be less in your buggy which will count for something. From what I recall they have been used for a good while in states where it gets fridgid cold because they're dry and won't freeze and break. Dry ought to equal less weight?

    I'm not very good with electronics but it would seem to me that if you have room to put eight 12V deep cycle batteries in the thing... and a switch to switch from one group of four for 48 volts, to the other group... that you'd almost certainly gain distance with your "reserve tank"...? As compared to eight 6 V batteries for 48V...?

  7. #7
    Associate Engineer
    Join Date
    May 2011
    Posts
    6
    The Optimas are an AGM battery(absorbed glass mat?) and are lighter than the lead-acid. I thought about the twin banks with a switch, but I'v been told connecting them all in series and parallel would be a better set-up. Run two parallel, series, two more parallel and so on. The Optimas have the same foot print as the 6-v lead acid batteries, so they will fit right in.
    Again, thank you for your input, it is much appreciated. Any other ideas or thoughts are more than welcome!

  8. #8
    I find battery capacity best visualised as a rectangle - one side is volts, the other is amp hours. You can get a long skinny rectangle, or a short fat one by playing with the dimensions.

    The rectangle? It's the physical size of your battery.

  9. #9
    Associate Engineer
    Join Date
    May 2011
    Posts
    6
    Just to let you know, I have had the 8-12 volt system in place for about six weeks now with a four panel 240 watt solar chargeing system in the roof. It all seems to work quite well and my range is improving gradually the more it is used. I thank all of you for your input. The weight savings from the change in batteries totals 176 lbs. and the solar panels weight 44 lbs. total for a net savings of 132 lbs. It makes no difference in my top speed, but seems to have a little more oomph from the start. One interesting thing I have noticed is among the three battery gauges I have, (analog, a DeltaVolt LED Battery Fuel Gauge, and the ProStar Solar Controller has one) they all read differently as to the charge left in the batteries. At this point I am not sure which is correct, the analog reads the highest and the solar controller the lowes. Just thought you all might like to know what has been going on. Again, thank you and I look forward to your thoughts on any of this.

  10. #10
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,045
    Glad it is working out for you, but not sure why range should be improving.

    Any gauge that reads voltage is only going to give a rough idea of state of charge. You need an Amperage value to reflect the true condition of a battery. That's best done with Load-tester that actually dumps a huge load across the battery for 10 seconds or so then calculates the drop. I get tired of trying to explain that to the folks around here who are on solar/wind power for their homes. They have these $10 plug-in things from the auto store and call me and say, "no lights, but the battery monitor is showing 11v, why?"

  11. #11
    Associate Engineer
    Join Date
    May 2011
    Posts
    6
    Thanks PinkertonD. I gather there isn't some sort of gauge to read the amps while on the fly, or if there is, it is expensive. As to the range increase, the man who set this all up for me said the batteries needed to be broke in just like the new cars used to need back in the day. We wanted me to drive 5-10 miles a day and charge it. Do this for a few days then increase miles by five and repeat, and so on. Now I am going 40-50 miles over 3 or 4 days, leaving it in the sun when I can, then put it on the charger. Alot depends on how I drive it as to how many miles I get out of it. Legal speed for these is 19.9 mph, my cart cruises at 28-29 with a top out at 34.3 down a slight grade. The faster I drive it, the shorter distance I get (rocket science isn't it). Good luck with the folks who live around you and stay in the dark. Start charging a consultants fee, might end the calls or make you some pocket money.
    Last edited by corvettedreamin; 08-20-2011 at 11:39 AM.

  12. #12
    Technical Fellow Kelly Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    1,422
    "Break in the Batteries"? I have heard about Ni-cads, and lithium batteries not achieving a full charge except when a proper charge procedure is followed.

    Aren’t the batteries in your golf cart Lead-Acid?

  13. #13
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,045
    Yes, you can get an Amp gauge that will constantly indicate available Amperage, but it will be using power all the time as it will be measuring the voltage-drop across a resistive (getting hot and using power) element. Even then it will only be a guide to the condition of the batteries because the amount of current draw your motor needs, the only real tester is something like this...
    http://www.harborfreight.com/500-amp...ter-91129.html
    But the 10-second testing will probably suck about 2 miles of travel from the batteries.

    I'm with Kelly on the "beak-in" if these are lead acid batteries. Absolute nonsense. Even the almost-myth surrounding Ni-Cads has been taken well beyond what is real. NASA were the first to notice the Ni-Cad recharge behavior when they had a "ship" orbiting around the Moon. They began to experience weird charging characteristics due to the regular darkness and light schedules of solar charging on batteries that were not yet depleted.

    Been down the consulting road for most of my life. It is now nice to give a little back without expecting a pay check. Forty years of careful retirement planning has taken care of the other issue.

  14. #14
    Associate Engineer
    Join Date
    May 2011
    Posts
    6
    The batteries in my cart are Optima AGMs. My knowledge on all of this is next to nothing, so I have to trust the man who installed all this for me. He is a retired fleet maintenance manager for UPS. After replacing batteries on a yearly basis, the whole fleet he was over was change to Optimas and never had to change one in the five years before his retirement. As for the breaking them in, I think it was so I didn't just go out and drain them right away (my guess anyway). Thanks again for all your input, I'm learning from you guys.

  15. #15
    Hey, just a thought on load testing of batteries. The tester would suck a bit of juice out, but you could actually use the vehicle as the load. What you're chasing is a voltage reading at a certain load. For lead acid, you want to confirm that you're not going below 1.8 volts per cell under load, this is 10.5V on a 12V battery - below that you know your battery is gone. Above that, you're looking for the voltage vs time curve, ie time under load.

    In summary, you'll get an albeit rough approximation to this with a volt meter, while you drive.

  16. #16
    well, i prefer to you go with Sealed Maintenance Free (SMF) Batteries or go with Tabular Batteries with high Ampere (AH) of range because these batteries don't need more maintenance. There are nothing with Voltage. You can use 8 batteries of 6 volt or use 4 batteries of 12 volt, thing is same. You have to increase Ampere power to give you large backup.
    __________________________

    Link removed - Not allowed...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •