Golf Cart 24 to 12V Voltage Reducers..Useful?

[NJT5047]

A friend of mine has a 24 to 12V voltage reducer that he bought to use on golf cart.  Seems to be 20 amp continuous 12V feed.   
Looks like a simple solution to my chassis radio, XM, backup cam, and other driver area 12V needs. 
Do these things use any power when there's no load on the 12V side?
Or, do they idle along using power in "wait" mode? 
Neighbor was going to use it to power an interior light and a radio on his golf cart.  His spousal component, who is obviously in charge of the golf cart, doesn't want a radio mounted on the golf cart.
I'm getting a good bit of "center tapped" 12V load on my crank batteries....looking for a way to keep both batts feeding everything.
Seems as though the longer I keep the bus, the more electronic junk I'm hanging on it.  Oh yeah, add the laptop and a small inverter to the 12V load too.
Any ideas how much a power a Vanner 50A equalizer uses while sitting?  Just curious.   
I reckon I could hook the golf cart power reducer to my house power and see what the monitor says about idle power use?   
This thing is a Transpo...or something like that.  Was not expensive.
Apparently 24 to 12V voltage reducers are common on golf carts. 
Any thoughts welcome!   
Thanks, JR

[Sean]

JR,

If you are trying to save a few bucks, this device will do what you want.  However, a better solution is a battery equalizer, such as those made by Vanner.

All such devices use power even when "idle."  That being said, if you only need the 12v loads while driving, you could switch the converter on and off with a 10-amp relay powered from your ignition switch, or, better yet, from the relay terminal of the alternator.  Of course, your radio will lose its memory if you do this.  (The constant load of the radio memory is another reason why your converter will be using power all the time, otherwise.)

FWIW.

-Sean
http://ourodyssey.blogspot.com

[NJT5047]

Thanks Sean.  I've got a 50A Vanner equalizer between the batteries.  It was an OEM item.   
I have no apparent problem with the setup as it is.  Just unsure about how much power the Vanner uses vs what a small voltage reducer would use. 
My monitor does not "see" the Vanner...so I have no idea what the control power use may be for a Vanner.  All these little bits of battery use add up. 
Regarding the radio channel memory...we don't want to lose that capacity. 
BTW Sean, would you care to share why my DirecTV decoder works on the inverter one weekend, and then may not operate on the same inverter a week later?   It will always function on the generator or power pole....but it is right fickle on the inverter.  Doesn't want to turn on...once on, it works. 
Reckon a small UPC would solve that issue?  Are UPCs suitable for a modified sine inverter? 
I have a Trace DR2424, which is a modified sine-wave.   The Aquos LCD TV works great on the inverter...as does all other 110VAC electronics in my coach.  The TV has a transformer power supply similar to a laptop...that may explain why the TV works, but the sat reciever at times will not.  It worked two weeks ago in Mt Airy, NC without a problem, but wouldn't work this weekend.  Wouldn't turn on. 
I use my barn receiver in the bus and hooked it back up in the barn tonight...works fine. 
Any ideas on the sat thingy would be appreciated! 
Thanks, JR

[Sean]

JR,

With regard to understanding the power draw of your Vanner:  a properly wired battery monitor system, such as the Tri-Metric or Link-10, will provide you with this answer.

A proper battery monitor will measure battery current at the negative (ground) side of the system.  So it will not matter if power is extracted at the 24-volt or 12-volt side of the system -- the entire draw, in amp-hours, will flow through the ground point.  If you shut down all your loads, both 12- and 24-volt, you can then see what the "idle" draw of the equalizer is.

As for your DirecTV decoder, I am at somewhat of a loss.  This unit most likely has a switching power supply, not unlike your computer or tv, and should not be overly sensitive to the modified-sine-wave output of your inverter.  That being said, it is possible that the waveform of your inverter is just enough out of tolerance that the decoder will not start up.

There are several things you could try.  There are inexpensive power-line filters that might help.  The draw is low enough that a small 1:1 isolation transformer would be inexpensive and might do the trick.  Or, just try unplugging and re-plugging the unit after the inverter has settled down a bit.  Without looking at your decoder and/or throwing a 'scope on your inverter, it's tough to say.

Lastly, let me say that if you already have a 50-amp Vanner on the batteries, the additional 20-amp converter is certainly not necessary.  While the idle current of the smaller unit may be less than that of the Vanner, you have already identified that you will need to use the center-tap anyway, due to the radio memory, so you might as well stick with the equalizer solution.

-Sean
http://ourodyssey.blogspot.com

[Dallas]

JR,
Have you checked to see if you have a good solid ground between the inverter, (not just the -12V on the battery cable connected to the inverter), the coach body, and the satellite dish?


This is just an off the wall thought about why your sat reciever works only once in a while. It seems possible that the LNB, since it works on DC power gets it's ground from the bus body and provides it to the receiver.

That would require the inverter body be grounded to the bus body?

I dunno, it's just a thought.

Dallas

[Stan]

If you want to turn off the Vanner when not in use, you can connect the radio directly to the 12 volt centertap on the batteries. The memory only draws microamps and the batteries will quickly balance when the Vanner is turned back on.

[DavidInWilmNC]

JR, I don't think there is a 'draw' on the batts when the Vanner is connected.  Does yours have a green light on it?  If so, and if both batteries are equally charged, it won't come on, which means that it shouldn't be using any power.  If the light is off, you should be able to remove all 12 volt loads and connect a multimeter in series with each of the EQ's leads.  That should tell you what draw, if any, the Vanner has.  That's how mine is supposed to work, anyway, but it's a current model 80 amp EQ. 

One thing you can do is to connect all that accessory stuff to your house batteries and connect your Vanner to those.  That's what I did for my 12 volt stuff.  When the alternator is charging, the house batteries connect to the starting batteries with a big (200 amp) cont. duty solenoid.  This give me lots of 12 volt capacity without the need for ony other battery bank as well as lots of 'easy' charging from the alternator.  Having the Vanner EQ. on your house batteries will also allow you to use a 12 volt charger to charge the 24 volt bank - hook the charger to the 'high' battery.  The only thing that's connected to my 12 volt start battery center tap is (or will be) an analog clock and the headlight wire.  I think that, in a conversion, the Vanner EQ is a waste connected to the start batteries.  Good luck with it.

David

[Sean]

"...I don't think there is a 'draw' on the batts when the Vanner is connected...."

I can assure you that there is.  The more modern the equalizer, the lower this "phantom" load will be, but ALL equalizers and voltage converters use SOME amount of power even when idle.  At minimum, on a very well-designed and isolated unit, this will be the power required to run the circuit that monitors the batteries (or loads) to make sure they are equally charged.

"...only thing that's connected to my 12 volt start battery center tap is (or will be) an analog clock and the headlight wire.  I think that, in a conversion, the Vanner EQ is a waste..."

Perhaps your coach has more modern electronics than mine (or perhaps you have a strictly mechanical engine and tranny).  My DDEC is 12 volt, and my ATEC is 12 volt.  Both of these devices also require an "always on" source of 12 volt power, as they both have memory that requires it.  For this reason, many manufacturers of 24-volt coaches spec an equalizer on the chassis batteries as standard equipment.  Once they've done that, lord only knows what other 12-volt loads they will add, just because they can (radio, backup camera, GPS, etc.).

FWIW.

-Sean
http://ourodyssey.blogspot.com

[DavidInWilmNC]

"...I don't think there is a 'draw' on the batts when the Vanner is connected...."

I can assure you that there is.  The more modern the equalizer, the lower this "phantom" load will be, but ALL equalizers and voltage converters use SOME amount of power even when idle.  At minimum, on a very well-designed and isolated unit, this will be the power required to run the circuit that monitors the batteries (or loads) to make sure they are equally charged.

With their original setup, I'm sure the NJT's had quite a bit of 12 volt items.  PA's, coin machines, etc would likely be present.  The old highway coaches didn't have EQ's, from what I can tell.  Maybe the later electronic ones did, but not the old mechanical ones that I looked at. 

If there is a drain from the EQ, it must be very, very low.  In three months of being connected to one, my year old 8D start batteries (being used as house batteries but not currently connected to any loads) take very little time to recharge.  By that, I mean several minutes with a >10 amp charger is all it takes.  It would seem that the only drain is the batteries' own discharge.  It's very easy to check this on my setup.  I'm using surface mount cartridge fuses for the inverter and equalizer.  I can just pull the 12V fuse and check the current there.  I'll do the same with the 24V fuse.  Vanner's website doesn't mention any drain, but that doesn't really mean much.  Their website doesn't have specific manuals for the 66 Series, which is what I have.  Anything I find when I search for battery drain due to a vanner battery equalizer says that there is none.  That also isn't conclusive.  What will be conclusive, to me, is to measure the draw.  It would be good to know how much, if any, there is.  Although not installed, I have a couple of small Battery Tenders that will maintain the charge on the start batts.  These 12 volt charger 'maintainer' will keep the batteries balanced while the bus is sitting. 

"...only thing that's connected to my 12 volt start battery center tap is (or will be) an analog clock and the headlight wire.  I think that, in a conversion, the Vanner EQ is a waste..."

Perhaps your coach has more modern electronics than mine (or perhaps you have a strictly mechanical engine and tranny).  My DDEC is 12 volt, and my ATEC is 12 volt.  Both of these devices also require an "always on" source of 12 volt power, as they both have memory that requires it.  For this reason, many manufacturers of 24-volt coaches spec an equalizer on the chassis batteries as standard equipment.  Once they've done that, lord only knows what other 12-volt loads they will add, just because they can (radio, backup camera, GPS, etc.).

Mechanical all the way!  My coach is much older and less sophisticated than yours.     The reason I say that there is no 12 volt draw except for the 'clock and headlight wire' is because a '78 MC-8 (as pictured in my avatar) is very unsophisticated.  That's one of the things I like about it, though.  I can't imagine any mechanical system as complex as a bus' being as easy to troubleshoot.  That's not to say that I'm all that good at it.  This is the first vehicle bigger than a 1/2 ton pickup that I've owned.  I do enjoy having an electronically controlled car, although there's an issue with the 'A/C amplifier' in mine, whatever that is - never a good thing in the summer!

David

[Don4107]

Something you might try with the Direct TV.  Plug it in with a good load on the inverter.  It may settle down the output waveform and/or voltage.  If that does not work try it with no load to see if it works better that way. 

[DavidInWilmNC]

JR,
As to the inverter and Direct TV problem... check on the e-place for small Xantrex inverters -sine wave, not modified s.w.- that are specifically designed for entertainment systems.  I believe they're 400 watts.  They have a built in transfer switch (or are either online like a high end UPS) for when the bus is running on gen. or power pole.  I wonder if it's something flaky in the receiver.  Good luck with it.

David

[Sean]

...
If there is a drain from the EQ, it must be very, very low.
...

Indeed.  Our ancient Vanners draw perhaps half a watt at "idle" -- not enough to even register on many ammeters, and probably overshadowed by the self-discharge rate of the batteries.  By the way, the spec sheet from Vanner for most of their equalizer models lists the "standby" current as "17 milliamps nominal at 28.4V" (direct quote from their literature).  I only mentioned it because JR seemed concerned about it.

In fact, our Vanners (we have one on the house and one on the chassis side) are wired in ahead of the main disconnect switches, so they are "on" all the time.  (The manufacturer-mandated disconnect procedure for these older units, involving disconnecting the equalizer ground before any other connections, makes wiring it any other way cumbersome.)

-Sean
http://ourodyssey.blogspot.com

[DavidInWilmNC]

Ok, so I checked the 'drain' that the Vanner EQ. has.  I disconnected the charger and there are no loads connected to the batteries (I'm working on the 120 volt elec. system at present).  First, I pull the 12 volt fuse.  The ammeter reads 0.2 amps initially - along with a small spark that always scares me.  It then drops down to .1 and will fluctuate between 0.0 and 0.1 with an occasional 0.2 amp reading.  Repeating on the non-10 amp range and plug on the multimeter gives the same results.  I replaced that fuse and pulled the 24 volt fuse.  I got 0.0 amps on both ranges with two multimeters.  This is to be expected with two identical batteries.  It be curious to know if the reading would be exactly the same if both batteries were charged with identical chargers simultaneously.  I'd say that, based  on these readings, I have a properly functioning Vanner 80 amp equalizer!     If .17 is what's specified by the manufacturer, the couple of watts 'being consumed' shouldn't make much, if any, difference.  I would agree with Sean in it's "...probably overshadowed by the self-discharge rate of the batteries."  I'll also agree that putting a disconnect switch on these is a royal pain in the butt. 

David

[NJT5047]

Thanks for the great information!   The MAK board has an excellent engineering department! 
Looks like the Vanner doesn't use enough power to be of any concern.
My 50A Vanner has no lights or controls. It is either hooked up, or not. 
As I understand, the correct way to disable a Vanner is to interrupt the ground lead first.   On my coach, the Vanner is between the batteries and hardwired directly to them.   It is whatever NJT in 1987 spec'd I reckon...although it looks new.  Probably replaced prior to selling the bus.
Regarding the sat receiver, the thing seems to work well on all but the inverter.  It will work on the inverter once it's fooled into turning on, but this may take ten minutes of dinking with it.  I don't spend 10 minutes trying to turn the thing on...but have, rarely, dinked for a while. 
The sense voltage on my inverter is low...the microwave clock comes right on with its "PF" for power failure whenever the inverter is switched on. 
May consider a cig inverter for just the sat receiver. 
All the grounds are good.  The inverter is definitely adequately grounded.   All other 110 VAC devices work normally. 
The receiver is a cheapo DirecTV item...may be that a higher quality receiver would work on the inverter. 
My batts require charging once a month to maintain 12.4 or better.  However, the radio, batt monitor (shouldn't be left on, but it often is), LP detector, and lights whenever we are inside the bus all create a load.
The batts charge up and in 24 hours they are 12.6 V each (after the charger is off and the batteries settle), but in two weeks, they'll be down to 12.3 or so.  Anything near 12V and they get charged.   Some of this is due to 4 year old house batteries.   The crank batts have zero load when the bus isn't being used and they'll stay charged for months.  I'll likely replace the house batts next spring. 
Dallas, the inverter is definitely grounded adequately.  Big wires and clean, tight terminals. 
Now off to Eplace to get one of the little ciggy sinewave inverters and try it!     
Thanks for all the information!   JR