12 Volt Inverter Meets 36 Volt Golf Car

[LowGear]

Dear veggie,

Logic and simplicity?  Sorry, not at Camp Aloha.

Casey

[cujet]

FWIW, I have a similar setup. However, I use my 48V golf cart at 24V to start aircraft engines and run the avionics. I simply hooked up to 3 of the 8V batteries.

I had intended on swapping the hookup, but never found a need. I have 2 of these same "club car" carts. The batteries on the one with the starting cable outlasts the other by years. This is because I rarely use the other cart (it's at the little airport). The "start cart" gets daily use and my current set of batteries are 8 years old and very strong.

[LowGear]

Hi Cujet,

This was my first thought.  Just hook the inverter up to the center battery and when I wasn't using the 12V draw the surrounding sister batteries would just charge her up to match the level of all three.  While the batteries are only about $200 each that's still $200 or a couple of very nice lunches even in Kona.

I know my incredible break-through in switching the relationship of the battery leads will work but finding the correct switch ran into the cost effective wall.

I've decided to get the guy running before I give much more thought and effort to the portable 120V AC source for the farm.  I've even considered hooking a wire feed system up to the 36 DC supply but that may not happen this decade.  One step at a time and Keep It Simple - Smarty.

Thanks for you experience and your suggestion just may be the easy way out.  I will report back once I cruse the driveway without cursing.

Cheers,

Casey

[RogerAS]

Hey all,

What about the old motor/generator combo's? Couldn't you build one? A 36V dc motor driving a cehapo gen head, or even an induction motor with run caps? All ya need is the right pulley and belt setup and there's AC when ya need it.

RS

[LowGear]

Hi Roger,

Thanks for the gray matter sweat.  With three group 27 batteries and a 60 pound motor hanging off the back you may appreciate that space is of a premium.  And I have the inverter - Paid For (did you hear the Angles sing?).

I was out fitting the motor bracket pattern this last week and realized I didn't know which way the motor rotated.  Today's chore.  Any easy suggestions?  There are four wire lugs on the motor.

(The wire feed attachment may get fitted before the inverter.  And that center battery is looking more like a sacrificial goat in the name of science more and more every week.  I could pick up three cheapski group 27s at Costco for under $200 - Yeah, I know this would be wrong and dirty science but the temptation is there.)

Gray Matter Ray Guns - Never Lock and Load!

Casey

[LowGear]

Wow!

I was just reading about rcavictim's buy of the decade and thought:

"Wait a minute, how about putting three 12 volt inverters on the rig (one to each battery and tying the 120 AC together- similar loads) or (the three inverters set in series across the 36 volts DC and tying the 120 AC together)?"

HUGH?  A moment of grace or what?

Casey

[rcavictim]

You could do that IF the inverters you use can be phased together.  That would involve getting inside the usual cheap ones and modifying two that would then be driven as slaves from one chosen to be the master.  Not a good job for the uninitiated or without some lab equipment like an o-scope, etc., and a modicum of experience with such things.  If you just take normal inverters and tie the outputs together you will most certainly let the magic smoke out in an instant.

[LowGear]

I think I'm pretty close to a solution.  Check out this relay on ebay:

http://cgi.ebay.com/12-V-DC-DPDT-40-AMP-POWER-RELAY-/390083564016?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5ad2cad1f0

Three of these would be the six battery terminals on the fabulous drawing below:

I've contacted them to see if they have a model that'll support a 53 Amp GE electric motor.  NO SWITCHING DURING OPERATION!

What do you think?

Casey

[LowGear]

I can't believe I've been on this project for two years and it's still not running.  I'm getting the crap unstacked from it this week and doing some real hands on this or that.  Enough Zen for this project.

A couple of thoughts.  I actually have gotten the battery shelves cut for three group 27 batteries.  I'm reconsidering going to four smaller batteries to get better performance out of the motor.  My last battery selection was three Costco deep-cycle units to do some testing.  This ATV will never be more than a few miles from home base and the charger.  I'm looking for cash friendly suggestions.  {I already have the post-its reminding me to stay on plan and get it done.}

I"m still holding onto the battery selector switches (see previous page) to switch from heavy current 12 volt for the inverter I have and back to 36 / 48 volt for driving around.  But I've noticed DC to DC converters that are used on golf carts and such to operate low current systems like lighting, computers, audio-video...  OK I'm kidding about some of the accessories but lights and horn for sure.  I may be going for street legalization.  I wonder if it'll qualify for the $10.000 federal tax credit?

Casey

[cujet]

I just re-visited this post and re-read my above post. I was not clear at all.

I simply used 3ea (out of the six) 8V cart batteries for my 24V "tap". It's not been a problem, I don't switch batteries and/or fiddle with it. If I drain the 3 batteries, I simply charge it up.

Yes, 3 batteries get more charge/discharge cycles. Yes, the other batteries might be 100% charged. Does not seem to matter. The system charges up just fine and battery life is excellent.

Lack of use is much more likely to kill your batteries. Like my other golf cart that does not see much use. It's batteries go bad regularly.

[LowGear]

Hi cujet,

The first thing that came to my mind was what if you ran the cart at 24 volts as well as your "starting" circut?  Yes it is going to be a slug but the three batteries will get worked out evenly.  If it's an older system like mine with big wire coils used as voltage drop resisters I'd guess it should be OK.  If you've got one of the electronic control systems then we're back in "I don't know land".  You might even opt for the two sets of three paralleled.

Thanks for the vote towards simplicity.  I just may hook my winch, another dead project put into this parts bin, and inverter up to the closest battery until something fails.  Smoke testing can be fun interesting.

Casey

[cujet]

While I don't use the 24V tap daily, I do occasionally use it for long periods of time, draining 3 of my 6 batteries.

I've just replaced a set of batteries after about 8 years of use. Interestingly enough, all of them were weak, bloated, and low on voltage. I'm not sure the 3 that had the 24V load were any weaker, or any better. It simply does not seem to matter in the end.

I've never been able to get "superb" life out of my golf cart batteries. Probably due to the Florida heat.

Unbalanced charging never seemed to be a problem.

I have charged the 24V set on occasion with an external charger. In an attempt at balance. Not sure that mattered either.

[LowGear]

If eight years isn't "superb" then we have very different expectations.  I'm 68 so getting the batteries to last to my 75th birthday would be SUPERB!

I'm still screwing around and not working on this unit.  I will finish the battery shelves this day - tomorrow - by Monday for sure - absolutely - is it going to rain this week end?

Casey