6 volt vs 12 volt

[corvettedreamin]

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.

[PinkertonD]

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.

[RWOLFEJR]

You want to make sure you are using "deep cycle" batteries which will also have the higher amp/hour ratings dave mentioned.

[corvettedreamin]

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?

[PinkertonD]

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.

[RWOLFEJR]

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...?

[corvettedreamin]

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!

[Bruiser]

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.

[corvettedreamin]

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.

[PinkertonD]

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?"

[corvettedreamin]

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.

[Kelly_Bramble]

"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?

[PinkertonD]

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.

[corvettedreamin]

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.

[Bruiser]

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.

[ggicollegeindia]

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.
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Link removed - Not allowed...

[Cap Sud]

Hello all I have read with lots of interest all the previous... and i have a new question that may be moved to the right thread if necessary.

I live on a sailboat and my diesel engine failed recently so i replaced it with a golf cart 48 volts motors. url removed...

The device has enough power to push the boat, but i face a problem with stocking energy. Since I have a limited space to pile batteries, I actually use 8 lead acid in serie parallel. The batteries are 730 crank deep cycle with 100ah. The motor eats 40 amp at its lowest speed and 200 at top speed (I have melted contact poles in 2 minutes doing that). So i was expecting to be able to push the boat for near 2 hours at minimum speed, but reality shows that i can use it for about 10 minutes and the drop in power is quite fast.

At top speed, the motor gives me about 2 minutes then drops down

I am trying to find the best setup to drive the boat for at least one hour on a full charge. Of course, i cannot enter ports with no power and hit everyone else... :-)


Question 2: when i connect 2 packs of 48 volts in parallel do i double my AH ?

Question 3: Can have one pack of 4 batteries of one capacity let's presume 100ah and the other something else let:s presume 200ah?

Thanks

Since I am quite on the move, you can reach me by email or skype. Just let me know in private.

[Cap Sud]

motor model D&D ES-10E-33 Motor, with dcx400 Alltrax Motor Controller

[Kelly_Bramble]

First, you’re probably operating in a saltwater environment – which is rough on electrical equipment. I doubt that the golf cart electric motor is rated for a high salt environment so expect a short life out of the electrical motor.

730 crank deep cycle with 100ah rating and you need 48 Vdc to power the motor at 40ah slow speed.
So, four 12 Vdc batteries in series for 48 Vdc to power the motor. Then you have another bank of four series connected batteries in parallel to double-ish your 100 ah.

Therefore, 200 Ah / 2 hours = 100 amps for a full discharge

but,

40 amps for two hours = 40 amps x 2 hrs = 80 Ah or almost 50% discharge of the batteries. – Which is about what you want..

Reality is that if you are draining the battery in ten minutes you are either pulling more amps than you think or the batteries are not rated at what you think they are – or both.

Melting poles? Insufficient cable sizes or poor connections or both.

You need to verify the battery ratings as well the electrical motor draw. Then verify your cables are big enough.

Doubling your battery capacity will not give you 2 hours run based on what your description on what is you actuals.

Seriously, a small outboard on a swing bracket might have been your least expensive and most practical solution to a broken diesel engine.

[JAlberts]

While Kelly has covered all of the significant pints of the issue, with regard to the melting poles, remember the poles on each these batteries are designed for the max current of the individual battery, plus a bit of safety factor. They are not designed to carry the maximum current from 48 v of 4 batteries connected in series.