| Author |
Message |
TomNPat
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 2:53 am: | |
We carry a 36 volt golf cart, use it as such on occasion, but have 6 ea. 6 volt golf cart batteries. Want to find a switch that would easily change output to 12 volt for connection to inverter, especially when traveling. This would also be useful for remote power needs while we are on the job and using it as a golf cart.
Would require a positive and negative change once each set of two batteries. So where would I find such a thing, electrical experts? |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 3:26 am: | |
Tom,
I'm not sure what you are asking for here...
You have a 36 volt golf cart, and a 12 volt coach -- these two systems are not "compatible" with each other.
If you want to generate a 12-volt take-off point from the golf cart, you can use a DC-DC voltage converter, designed to take 36 volts and produce 12. Probably pretty expensive for the currents you are talking about.
You can also "tap" the cart bank after the first two batteries (often how 12-volt lights and other accessories are run on electric carts). This will, of course, result in the first two batteries having different cycles than the other four.
If what you want is to be able to "reconfigure" your bank of six volt batteries to produce either a 36-volt or a 12-volt output using the whole bank, you will need to build up a 6-pole, double-throw (6pdt) switching system capable of carrying the full cart current (probably in the neighborhood of 300 amps DC).
There is no such thing as a 300-amp, 6pdt switch, so you will have to make this using 300 or 400 amp dc rated "reversing motor starters" (really just mechanically interlocked contactors). Retail, this type of switch would cost a couple grand, easily. You might be able to find the contactors you need on, for example, eBay, for around $70-$200 each (you will need four of them, or two pairs), and wire them up with welding cable or similar. You probably want ones with 12vdc coils, which will likely be hard to find, so you should budget for additional replacement coils (I would guess another $30-$50 each on an auction basis).
All in all, I would think this is a lot of money and a lot of work for very little gain...
-Sean |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 5:42 am: | |
Yours would be another case where Manual Labor would make far more sense than designing & building some automatic electric thing.
Simply get a harness built (not expensive) to hook all the terminals together in the prefered Deep Cycle , series parallel arangement.
Disconect all the golf cart leads , slip on the power the House harness , and enjoy the capacity of your 400 lbs of batts boondockin!
FAST FRED |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 9:39 am: | |
yeah...Don kinda had that Idea...useing the cart batteries as house batteries while boondocking |
Vin (Billybonz)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 11:47 am: | |
Tom, Try searching solar power sites. I know they make converters that use 12vdc in and output 36vdc. You could try here...not an endorsement, just a suggested link. I've never done business with them.
Vin
http://shop.altenergystore.com/itemdesc~ic~SORCV12%2F36%2D1B~eq~~Tp~.htm |
Gary Stadler (Boogiethecat)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 12:14 pm: | |
Tom, If my take on what you want is what Sean said, to be able to reconfigure your 36 volt battery bank to 12 volts at the flick of a switch...
I politely disagree with Sean- you can definitely get 300 amp 6pdt switches- though they aren't super common, they do show up at surplus stores and ebay fairly often. Here's an example although this isn't quite exactly what you're looking for...but it's the class of switch you'd be looking for. I have one on my electric minibike for just this purpose and it works fine.
http://www.surpluscenter.com/item.asp?UID=2005022010495123&item=11-2118&catname=electric
You can also buy them new although they'd be fairly pricey. If you want to do that, I'd be happy to find a source for you.
On another note, here's an interesting way to reconfigure a battery bank instantly from 12 to 36 volts with only two simple 300 amp SPST contactors!! This may work for you although it's more suited for the speed control of an electric vehicle, which is what I figured it out for many years ago before solid state controllers were easy to make:
http://www.heartmagic.com/EVbatteries.jpg
You'd need two simple SPST contactors big enough to handle your load, and 4 diodes capable of the same ratings. It's a trick circuit that if you look at it, it will output 12 volts with all 3 batteries in parallel, if both contactors are opened (Well, slightly less than 12 volts due to two diode drops). If the contactors are both closed, it reverse biases all the diodes and puts all 3 batteries in series for a 36 volt output. (If only one contactor is closed, it will output 24 volts!)
The caveat here is that you'd either need three isolated 12 volt chargers (because only one of the batteries can be connected to ground but not the other two) or a 36 volt charger, which would only work if the contactors were closed...
Have fun figuring it out!
gary |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 8:25 pm: | |
Gary wrote "you can definitely get 300 amp 6pdt switches- though they aren't super common"
Gary is absolutely correct. Somehow, in my little pea brain, I was thinking "remotely operable switch" meaning a 6PDT, 300-amp *relay*, and those don't exist (at least, I was never able to turn up any in many dozens of hours of research). As Gary points out, *manually* operable high-current switches are available in almost any number of poles. My bad.
I do think you'll find that 300-amp switches are still pretty pricey. But if you find one, give me a shout and I can help you with the wiring diagram to do what you want.
And Gary -- I assume those are some big-a** diodes in your drawing!
-Sean |
TomNPat
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 21, 2005 - 12:48 am: | |
Thanks guys,
Had figured on manual knife transfer switches but the alternatives (that fit the budget) are welcome. We could just duplicate the battery bank but the weight and room is costly, that is why we are asking.
Thanks for all your help.
TomNPat |
Craig (Ceieio)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 21, 2005 - 10:58 pm: | |
Those diodes must look like golf balls, or maybe baseballs!
You could also solve the charging problem with a big DPDT switch that would disconnect the battery (-) terminals from the diodes and connect them to ground for charging.
Maybe you could even re-config those huge diodes into a bridge rectifier to make a huge battery charger.
OK, I am returning to passive mode now. :-) |
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