Why is taking 12v from one batt bad?

[Happyland1410]

Another option, if you had multiple simultaneous small loads, would be to balance them between the 2 batteries. Obviously this would require a separate ground for the items on one of the batteries. We have been running the radio, emergency lights, and siren off of just one battery on our fire department's deuce for many years and battery life has not been too bad. I agree with others that this is not the best solution but it can be done. I like the inexpensive 24v to 12v converter referenced in post #13 above. I may see about getting one of those for our fire truck to be a little kinder to the batteries.

 

[SEAFIRE]

In the Fire Service this has been written about, debated and talked about since fire departments started running deuces. How to get 12V from a deuce for radios, sirens, & emergency lights?

Many fire departments around here still just hook up to the 1st battery for 12v. I've seen a battery blow a hole in the top of it because the 2nd battery gets overcharged while the 1st one the 12v comes off of is drained.

Originally both of our current deuces had the 12v off the first battery set-up with optima gel cell batteries in the optima 6TL adapters. Both trucks responded to a 24hr grass fire response some years back, the emergency lights ran the whole time on both trucks. Afterwards, one truck had a bad 2nd battery, on the other truck both batteries were ok, go figure.....

24v to 12v convertors seem to be the best set-up, running a seperate 12v system just means extra batteries, another belt and alternator to worry about, etc.

Another option we used to do which was mentioned already, was swap batteries around every month or so.

The optima gel cell are way tougher than the military U6TL batteries. The Marine model optimas have an additional set of threaded posts you can hook other stuff to.

We get heavy duty 30 amp 24v to 12v convertors for $240 from a local Motorola dealer. I know they are pricey, but they work the best for us.

Again just my 2 cents....

 

[Happyland1410]

We get heavy duty 30 amp 24v to 12v convertors for $240 from a local Motorola dealer. I know they are pricey, but they work the best for us.

I'm curious how the specs on your 24v to 12v converter compares to the inexpensive one referenced earlier? As you know, on a volunteer department with very limited funds, $37 sounds a lot better that $240.

JR.com: Pyle Plug In Car 720 Watt 24V DC to 12VDC Power Inverter W/ PMW Technology in GPS Power Inverters

* PMW Power Technology
* with 4 Ways Protections (short circuit, over load, high voltage and low voltage)
* Converting efficiency: >85%
* Input Voltage:24VDC
* Output Voltage: 12.5v-12.8v DC
* Rating Load:30A
* Converse Efficiency: 87%
* Dimensions: 5.5" x 5.5" x 1.8"

 

[tbearatkin]

A 30amp = in a perfect world 3000 watts. vice your 7.2 amp 720 watt. You will have to figure out how much juice you need to run your accessories.

I used a black and decker 400watt to run my laptop in my 12 volt truck and I am pretty sure that is the reason why my alternator decided to go bad. Don't know enough about them to prove it but it seemed to happen within 2 months of using it. Most likely my truck had a light duty alt in it and needed a heavy duty one if I was going to use a converter.

I had to use a convertor because the laptop would only charge with cord that came with it. No aftermarket device would charge it. I had to have the compaq brand power cord and the car lighter converter was $100+ at the time.

 

[Oilleaker1]

I have two M37's that I run a 12 volt heater and small defroster off the first battery. Both trucks have a battery disconnect when not being used. I fuse all right at the battery. All is off when the disconnect is turned off. I've never looked back for 2 1/2 years, never charged the batteries, and never swapped them. The batteries were used when I put them in. If you are hobby guy like me and don't drive every day all day, I wouldn't worry much. If you install the units for hire, I'd go the converter route. Some are a resistance type and get hot, so take heed. Heavy draw items, you may have problems. John

 

[sewerzuk]

A 30amp = in a perfect world 3000 watts. vice your 7.2 amp 720 watt.

?

Not quite...
30amp=3000W ONLY if the voltage is exactly 100v; this isn't a standard voltage for anything...

Power(watts)=I(current) x V(Voltage)

or for an AC system:

Power(watts)=I(current) x V(Voltage) x Power Factor

What you are describing is a 12v to 120v inverter...something totally different than the 12v converters discussed in this thread.

 

[sewerzuk]

I run a battery equalizer in my deuce; here's a link to the thread. It's about halfway down page 1:
http://www.steelsoldiers.com/deuce-...5511-all-stuff-i-did-my-deuce-right-here.html

 

[tbearatkin]

Yep your right sewerzuk get so used to dealing with 110/120 ac volts I forgot that the amp draw had to be converted when reducing it to 12volt and your amps available go up.

However not sure what the continues watt draw is for the Motorola since no model number is given but that Pyle model only has a Output of 360W Continuous and a surge of 720W so once again you have to know the amps of what you are wanting to run.

I hate false advertizing what they are really selling is a 360watt converter but as long as you do your research up front in regards to how much juice you need you should be okay.

 

[scottjhl]

As always an interesting discussion on 12v.

I'll throw in the Pure Sine wave inverter for the fun of it.... But again its pricey

 

[SoundGuy]

May Favorite way to go about it is to use a cheap 24v to 12v converter. There is usually an adjustment inside that will allow you to turn the voltage up to 13.8 volts and then use that to charge a separate 12v battery with a 1/2 ohm resistor in series with the positive terminal to prevent overloading the converter. If you get the PWM (Pulse Width Modulation) Type, you may not need the resistor as many have current limiting built in. This way you can run as much as you'd like off the batter and it will charge the battery as needed. Also the PWM converters are more efficient and do not draw too much current on the 24vdc side. (Cheap ones will draw the same amount of current on both sides. Good ones draw half the current on the 24vdc side.)

 

[SEAFIRE]

Sorry, the converters are not motorola brand, they are made by ICT, we get them from the local motorola land mobile dealer, my mistake.

Here is the web site

ICT - DC-DC Power Converters

30A
ICT2412-30A

 

[Oldfart]

This is kinda like saying, if you eat alot of Taco Bell you will get diarrhea. If you take a bunch of Tums it will help. But if you just don't eat at Taco Bell (you have other better choices that may cost more), it's a non issue.

You could just charge each battery separately after each use. But who wants to do that...

To be really kind to a battery pack, one should charge each cell independently of the rest, but who really wants to do that. The very difficulties described in charging an imbalanced 2x12 volt series battery pack can be found between cells in a 12 volt battery. A parallel battery pack follows the same internal resistance rules with the more resistant battery usually becoming sulfated while the less resistant battery boils itself to pieces. This is all about cost benifit comparisons, i.e. cost of replacing batteries versus the life of the battery in the application. The safety considerations are what normally dictate when a replacement should be made. Too much out gassing and you can blow the top off a cell.

 

[Awesome Possum]

Look at batteries this way: A 12V battery is a series of 6 2V batteries, and 2, 4, 12, or 960 etc batteries are simply adding up to one big battery, whether they are in series or parrallel, or both (yes, you can do it.) If you want the least expensive 12 V system, simply add an extra battery you can charge separately at home, preferably a non-spillable AGM, maybe under the passenger bench or just about anywhere. Yeah, it ain't high tech, but it'll work. Add a solar panel if you just gotta' have the high tech part!

 

[6x6guy]

I have used 24 to 12 volt converters on several of my trucks, rated at 25 amps - for all the lights
and 12 volt power accessories for several years now- just got tired of replacing batteries.
Memphis Equipment was the company that I had purchased them from and have no problems with the charging of the system or the longevity of the batteries.

 

[islandguydon]

There are converters and inverters, they have 2 separate functions. Converters are used when you have all DC equipment to raise or lower the DC current. Inverters are used when your changing from DC to AC.

I installed a DC to AC INVERTER to power up to 1000 watts/ 2000 surge watts @ 30 seconds for starting a heavy load. I hooked up to the front battery and only use the inverter when the engine is running. There is little draw if any noticeable when pulling 500 watts with the amprobe and the engine off. I like the set up, make sure you hook up the "chassis ground" very important to the life of the inverter.

I found a nice spot under the air handle, fits tight and leaves 1.5" for the door.

 

[islandguydon]

Wow thank you guys! It does make sense now! I'm thinking about putting a separate alternator and battery in to run a 12v system. I don't want to run anything big but a few lights (which I guess could be considered big), and charge my cell, etc. I definitely won't take power off one battery now though!

I have a 9000 Lbs winch and a 12VDC inverter running off the front battery, I feel the thread comments are correct about the even charge rate, but you only use the winch, what 3-4 times a month and the inverter very little and 200 watts for lights is nothing when you have a 100 Amp alternator running. I am also confident you will drive the truck often so the battery's will always be charged anyway, I think you will be OK, Just my opinion.

Just make sure you have the truck running when these are in use and you will be fine.

 

[JeffShoots]

If you just want an accessory port to charge your cell phone, or run a GPS, or even a stereo as long as you aren't running a big amp and subwoofers, there would be no problem at all.

Been running my iPod / cell phone for a long time now like this.

 

[Stalwart]

CUCV aren't a problem as their charging system is MEANT to have a 12V tap. All the rest will have an eventual toll on the batteries.

Use a converter, equalizer, add a 12V battery and charging system or tap the grounded battery and pay the price of shorter battery life. Your choice, it's your truck after all.

 

[tbearatkin]

CUCV aren't a problem as their charging system is MEANT to have a 12V tap. All the rest will have an eventual toll on the batteries.

Use a converter, equalizer, add a 12V battery and charging system or tap the grounded battery and pay the price of shorter battery life. Your choice, it's your truck after all.

I don't have a duece YET. Its been a few years since I drove one and we had CM's that did the maint.

But the is the correct thinking process. The Deuce and normal 24volt vehicles have one alternator/generator that provides 26 volts to the batteries which is why there is a impact on 12V from one battery. The CUCV have two alternators that provide 14.5 volts to each battery on its own so it does not matter as the system act like a regular 12volt vehicle. (24volts is only used for the starter and for jumping other 24 volt vehicles and military radio)

 

[quickfarms]

all of this assumes that both of the internal resistance batteries are exactly the same which is probable not the case in reality. They are probable very close.

Another item that directly affects the battery life is the voltage regulator. The solid state one is much easier on the batteries and will greatly increase the battery life.

If you want to just charge your cell phone then hook it up to the low side battery.

If you want to run high amp accessories such as lights and sirens I would use a converter.