m715mike
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What kind did you get? I'm interested in the "water tight" aspect!
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24v to 12v converter?
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Bravojmc
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SublimeMudTime
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I have one of the pulsetech distribution boxes too. they are NICE! but I have a 200A dual volt alternator so running the 12v off that box will not be an issue. plus it has their vodoo circuitry to help keep the batteries maintained...
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I'm using the Pyle 60 amp converter. The output is very stable and with 60 amps, I can use it to charge my separate 12 volt battery. I use this to run some small electronics, charge my trailer battery and power the electric breaks on my trailer. I only wish the output was adjustable. I would prefer to charge at 13.8 volts than 12. But so far I don't have any complaints...
shawnshumvee
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sounds expensive? But thanks for the advice.
gimpyrobb
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Thats whats great about mil-surp, It was only a couple hundred when they are usually 600. The batt eq was even cheaper at about $100.
baxter462
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FYI, this is what they do on the M939 series 5-ton trucks to get low speed for the heater blower. They run the blower on 24v for high speed, and 12v via a wire connected between the batteries for low speed. At just a few amps, it must not be as bad as we would intuitively think.
gimpyrobb
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I guess if they drove them off a bridge, it would be ok for you to do it too?
As the saying goes, they don't make them like they used to. They used to have resistors for the low speed setting. I guess they don't have too much budget to worry about either. I prefer to do it the right way and NOT kill my batts, feel free to do as you please.
As the saying goes, they don't make them like they used to. They used to have resistors for the low speed setting. I guess they don't have too much budget to worry about either. I prefer to do it the right way and NOT kill my batts, feel free to do as you please.
baxter462
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I think it is a little bit presumptuous to say a few amps of imbalance on lead acid batteries in series will "kill"them. I was just saying that it seems like people have been using the low blower motor setting on their five ton trucks for years without causing premature battery failures. Seems kind of odd to me that a truck engineered for maximum reliability would have a design issue known to "kill" batteries. I agree if the imbalance is too great, it'll cause one battery to overcharge while the one with the extra load on it won't charge, but a couple amps on a 100ish AH battery won't hurt anything.
With all that said, I don't think it is ideal to "center tap" the batteries to get 12v, but I also think a 24v to 12v DC to DC converter has some drawbacks too. I'd weigh out the pros and cons, and based on what I needed 12v for, I'd make my choice accordingly. For a tiny load like a cell phone charger or something I used very intermittently like the gun mount the author of this thread is using, I'd probably center tap the batteries. For a continuous, slightly larger load, I'd consider the converter. Splicing into my wiring and drilling mounting holes to install a converter would have to be worth it.
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Carrera911
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I use a sure power 40 amp equalizer for my stereo setup and it has worked well since December. I installed it neatly (imo) in the little compartment adjacent to the battery box. It is water resistant and only 150 bucks. It is powerful enough to supply even a winch and then top off the 12 volt battery after you're unstuck. I posted pics of the install in December on the what you have done lately forum. I have heard from electric golf carts it is a bad idea to tap off of one battery in a series circuit for even low power stereos and lights. See what happens is the alternator looks to meet the ~28 volt target. If you pull one battery down to say 12 volts then to meet the 28 volts it is looking for it overcharges the other battery to 16 volts. This is then bad for both the batteries in question.
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The cheapest way to get 12 volts for a low power device is to use a LM7812 regulator they can be fount on e-bay for about $0.10 and can power about 12 watts or 1 amp. For charging cell phones there are a number of usb chargers that work with 12-24 volts for about $5.00. I also found a couple of 12 volt regulators that can power up to 20 amps for about $10.00.
baxter462
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This is certainly the best all around option in my opinion. Small/intermittent loads are fine to be "center tapped" without any additional considerations, but larger and more continuous loads would need an equalizer or converter. A large/robust enough DC-DC buck converter would be expensive, and there are some load that just wouldn't be feasible with a converter (like a 12v winch).
Thank you Kc5MZD and Baxter462 for not being condescending and finding a quick solution that will please most people.
Like I said before, I did center tap, but only for the CB when off roading and the cell phone charger that I never used. I haved this on my Humvee for over a year without any issues
Like I said before, I did center tap, but only for the CB when off roading and the cell phone charger that I never used. I haved this on my Humvee for over a year without any issues
If you have a dual-voltage alternator - then this is the proper way to do it.
baxter462
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The CB will draw a lot more current than a LM7812 can handle. At 28.8v input voltage, a LM7812 could only handle a max of 700mA before the 12 watts of maximum power dissipation would be exceeded. You'll have to use one of the DC-DC 24v to 12v buck converters people on here have been talking about, once you determine the current draw requirements of the CB.
infidel got me
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That's basically the same one I listed in post #8-- but mine was half the price. At least you got the right one, and it will work fine for what you are wanting to power....
baxter462
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It isn't a 100% efficient conversion from input power to RF power out, plus there are things like meter backlights, the speaker, etc. I seem to remember a typical CB drawing a couple amps when transmitting. I haven't messed with one for years though. Your best bet is to measure the actual current draw under all conceivable conditions (transmitting, receiving with volume way up, etc.) If you're under about half an amp max, I'd say go for it. Just make sure you use a good heat sink on that 7805.
Oh, and I should clarify that the output of the 7805 will only allow a max of 8.4 watts at 28.8 input volts.
Oh, and I should clarify that the output of the 7805 will only allow a max of 8.4 watts at 28.8 input volts.
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I found a couple and tried them out. Using one gets hot when the radio is on even with no sound - just back lights. Using two get warm but heat up if the squelch breaks. They get verrrry hot trying to transmit. There is also a small voltage drop leaving less than 11.5 volts while trying to transmit. Also it takes over 14 volts before they can get to 12 volt out. They work good for small loads...
I will try to round up a few more and see how many it takes to make a 12v CB run on 24v reliably - next time I get board...
I will try to round up a few more and see how many it takes to make a 12v CB run on 24v reliably - next time I get board...