Is getting 12v from a 24v 70 series really this easy? (1 Viewer)

[luigibella]

The IPF lights on my rig set up by the previous owner are hooked up to 24 volts even though they are made for 12 volts. Time to fix that.

Talking with a friend who knows a lot more than me and he suggested that as one battery reads 12v and the other reads 24v, we could take a direct output from the battery that only has 12v to power the lights. Perhaps replacing the series battery connector to one with a Y for the 12v output.

I see everyone else using a 24v to 12v converter, but would this work in theory?
My apologies if it’s a dumb question, I tried researching but found no relevant answers.

 

[RHINO]

Yup, that simple. Both batteries are 12v btw, pull your power off either one individually and you have 12v. But you need to run that lighting circuit dedicated, wire, switch, relay, fuse ect. separate from the car wiring, switches, fuses ect, not good, thats why people run converters.

 

[AirheadNut]

Technically that would work, but it is a good way to kill your batteries. In a 24v system both 12v batteries are quite sensitive to any charge or discharge imbalance and pulling 12v off just one battery for accessories will cause premature failure of both batteries. That’s why most people run a 24-12 converter to power their 12v accessories.

 

[Felde]

@AirheadNut 2x
If 12V is taken from 1 battery this one will always draw some internal current to balance with the 2nd battery. On start, the weaker battery will suffer. Results in low lifetime.
I even put a load balancer to make sure both batteries get equal charge. In some LC 24V the batteries are mounted quite distant and the long connection doesn't help on equal charge.
120W/10A or 240W/20A DC-DC converters are cheap-cheap. They do draw a little mA on idle, thoug. But my truck can sit fir for 2 weeks with it on, without any issue. If that doesn't comfort you, put a 24V relay in the ignition switch line and switches the DC-DC.
Cheers Ralf

 

[FelixKruzza]

I have the same issue with my IPF light when I got the truck, they wired it on a single battery since its a 12v lights on a 24v system. What I ended up with is rewired with the same IPF wiring harness but with 24v H4 bulbs. The bulbs are the same as the headlight with H/L beam. Hella lights still sell H4 24V bulbs in 100/90 watts.

The IPF relay is controlled with 12V from the radio. Lucky enough that my radio is 12V. The load side of the relay does not care if its 12V or 24V. The amp draw are half in 24V system, so lighter load. Plus its only 2 H4 bulbs. Wire the load side with 24V to even the draw from the 2 batteries.

Now I have 4 headlight with H/L beam and can control it separately. Really helps since I have an ARB bullbar and kinda block the factory headlights. Plus halogen is not that bright compare to modern headlights.

 

[george_tlc]

To OP. Your friend is giving bad guidance. Do NOT draw current from only one battery in a 24V series connected system. Sure way to kill batteries and to cause the low battery (the '12V one') to undercharge while the high battery overcharges and boils.

Get 24V bulbs for your lights.

There are plenty of threads pointing out the issue of drawing current from only one battery in a 24V system, none end with good results.

cheers,
george.

 

[JDM Journeys]

Agreed with all above. Batteries aren't cheap anymore. But good LED's aux lights are happy to take your 24volts and broadcast it. Hella 500's (the led version) are a nice reasonably priced example, as long as you swap the included 12v relays for 24v.
Or, as suggested, swap the bulbs on an existing 12v setup. Easy peasy.

 

[luigibella]

Thank you everyone for the great advice!

A couple follow up questions if you don’t mind:

1. Am I correct in understanding that all I’d have to replace is the bulbs with 24v bulbs and the 12v relay is okay to stay as is?

2. How easy of a solution is wiring in a 24v to 12v converter? I found this one on Amazon with what seems like pretty good reviews. Could this be put inline in the engine bay between the batteries and the Power Outlet where the IPF lights are pulling from or does the wiring going to the control button inside the cab also need to be stepped down?

So sorry if these questions are overly basic, I have (obviously) a very limited understanding of correct wiring but I’d like to get everything done right.

 

[george_tlc]

^ 24V everything, relays, lights, etc. The relay coils (the thing that activates the relay contacts) need to be 24V since they will be activated with 24V signals.

Converting 24V to 12V for lighting isn't really efficient... Just get 24V bulbs or as someone mentioned, move to LED lighting that can run 12V-24V. More light, more efficient. Costs more though, than just putting 24V bulbs in your existing IPF lights - that's the easiest solution.

cheers,
george.

 

[robmobile73]

From experience, if you tap positive between the batteries for 12V even with a light load it will kill one of your batteries. I did this to get 12V for my radio thinking that it was such a small load that it wouldn't matter. Within 2 weeks I had to roll start my LC to get home. Upon arrival one battery was at about 9V and the other at 16v with the engine running. Both batteries had to be replaced within 3 months.

40Amp voltage converter is cheap on AMZN and many LED's will run 24 or 12V. Voltage converters do draw some "idle current" even with no load on them. Mine would flatten the batteries in 7 days of sitting. Don't wire it always on. Some voltage converters and LED's can cause radio interference/weak reception. Some electrical parts out of China labeled 12/24V will run, but die prematurely when operated on 24V..........Good luck!

 

[JuanJ]

Thank you everyone for the great advice!

A couple follow up questions if you don’t mind:

1. Am I correct in understanding that all I’d have to replace is the bulbs with 24v bulbs and the 12v relay is okay to stay as is?

2. How easy of a solution is wiring in a 24v to 12v converter? I found this one on Amazon with what seems like pretty good reviews. Could this be put inline in the engine bay between the batteries and the Power Outlet where the IPF lights are pulling from or does the wiring going to the control button inside the cab also need to be stepped down?

So sorry if these questions are overly basic, I have (obviously) a very limited understanding of correct wiring but I’d like to get everything done right.

Hello,

It is better to leave the 24V electrical system unmolested, especially lighting. A couple bulbs are cheaper than an electrician.

A 12V converter is better suited to stuff like a radio. It will drain the batteries a bit quicker if your truck sits unused for more than a week.

If your intended application goes beyond the radio, consider setting up a separate electrical system with a third battery.







Juan

 

[JDM Journeys]

Hello,

It is better to leave the 24V electrical system unmolested, especially lighting. A couple bulbs are cheaper than an electrician.

A 12V converter is better suited to stuff like a radio. It will drain the batteries a bit quicker if your truck sits unused for more than a week.

If your intended application goes beyond the radio, consider setting up a separate electrical system with a third battery.







Juan

Juan speaks the truth. This is exactly how I did it as well. DC to DC 24->12 converter to third battery, and then 12v things are happy. You can even do cool things like switched power using the 24v to trigger a relay to open a 12v circuit. Good times!

But I still run LED fogs via my 24v system up front.

 

[Felde]

Hi
You can keep the 12V wiring harness of your aux lights and run 24V on it. Relays need to be replaced by 24V coil-side, though.
Bulbs to go to 24V or respective LED.

If you need 12V for auxiliaries, e.g. stereo, you may wire in a DC DC converter either
a) permanently (which has the issue of idle load flattening the batteries after 1-2 weeks) or
b) via a relay (24V coil) controlled by ignition key.
In any case you need an extra fuse close to the battery and another fuse(box) behind the DC-DC converter (12V output side) to the auxiliaries.

b) can be done this way:
Normally, the cigarett lighter is controlled by ignition key 1st position (even before the ignition / engine lights come on). You can steel +24V from there to the relay coil. A new main wire goes from battery +24V, trough a fuse (as close to battery as possible) , trough relay's load-side on to DC-DC converter 24V input side. By this, the DCDC only comes on when the ignition key at least is in pos 1.
Cheers Ralf

 

[MontyLC]

Hello I'm in the same

Hi
You can keep the 12V wiring harness of your aux lights and run 24V on it. Relays need to be replaced by 24V coil-side, though.
Bulbs to go to 24V or respective LED.

If you need 12V for auxiliaries, e.g. stereo, you may wire in a DC DC converter either
a) permanently (which has the issue of idle load flattening the batteries after 1-2 weeks) or
b) via a relay (24V coil) controlled by ignition key.
In any case you need an extra fuse close to the battery and another fuse(box) behind the DC-DC converter (12V output side) to the auxiliaries.

b) can be done this way:
Normally, the cigarett lighter is controlled by ignition key 1st position (even before the ignition / engine lights come on). You can steel +24V from there to the relay coil. A new main wire goes from battery +24V, trough a fuse (as close to battery as possible) , trough relay's load-side on to DC-DC converter 24V input side. By this, the DCDC only comes on when the ignition key at least is in pos 1.
Cheers Ralf

Hello I'm in the same situation, I just bought a BJ74 with the head unit wired through the battery with a load of other wires (guessing for amp and sub) in just a huge mess so decided to rip everything out and start over. Was thinking of buying an Aerpro 24v to 12v converter, but not sure where to connect to. My cigarette lighter and Clock are always on, is this normal or do I need to rewire that too? Any help is much appreciated, been wrapping my head around this for a while.

 

[Irish11]

Hello I'm in the same

Hello I'm in the same situation, I just bought a BJ74 with the head unit wired through the battery with a load of other wires (guessing for amp and sub) in just a huge mess so decided to rip everything out and start over. Was thinking of buying an Aerpro 24v to 12v converter, but not sure where to connect to. My cigarette lighter and Clock are always on, is this normal or do I need to rewire that too? Any help is much appreciated, been wrapping my head around this for a while.

I read up a lot on this before I jumped in. First I took mine back to stock and then added in a 24v to 12v stepdown. Here are some good reads on the subject.

​

Installing new 12V stereo head unit in 24V HJ60 | IH8MUD Forum​

​

Running a fridge on 24v | IH8MUD Forum​

​

Converter/Radio install in BJ71 | IH8MUD Forum​

​

HJ61 and a 12V radio.. | IH8MUD Forum​

​

Builds - JDM 73 | Page 4 | IH8MUD Forum​

​

Ultimately I copied @elkaholic's setup but didnt need to have the 12v constant because I have a 24v stereo (you can find them for heavy equiptment shops like CAT and other tractor manufactures) 1986 BJ73 - Spanish Import to US - Under New Management - https://forum.ih8mud.com/threads/1986-bj73-spanish-import-to-us-under-new-management.823346/post-9467821 and got a Pyle converter and followed his diagrams for wiring. I did add a 12v fuse box in the kick panel inside the cab (you have to relocate the wiper relay, but it works)

 

[george_tlc]

^ if you want your batteries to last, the only connection to the positive on the low battery (the one that has the vehicle ground connected to its negative) should be a lead that runs to the high battery.

i.e. you should treat the two series 12V batteries as a single 24V battery with NO loads connected at the mid point. Any 12V load connects to the output of your 24V->12V converter.

cheers,
george.

 

[Felde]

Hello I'm in the same

Hello I'm in the same situation, I just bought a BJ74 with the head unit wired through the battery with a load of other wires (guessing for amp and sub) in just a huge mess so decided to rip everything out and start over. Was thinking of buying an Aerpro 24v to 12v converter, but not sure where to connect to. My cigarette lighter and Clock are always on, is this normal or do I need to rewire that too? Any help is much appreciated, been wrapping my head around this for a while.

Hi
I would suggest to 1. bring the 24V setup back to close to factory standard and eliminates any 12V crappy installations.
Clock always on is normal, lighter probably too (depends on model).
Then 2. add a thoroughly designed separate 12V setup with a 24V to 12V converter.
To design this you should carefully think about where in the car you need what power for what type of appliances. Also consider whether there is a need for a dual battery setup. First you need to calculate the maximum power (Watt=Amps*Volts) your desired appliances would draw. This determines the size of DC-DC converter, main fuse rating and main wire gauge to use.
On general bases (and based on my own experience and mistakes):
- If a dual battery setup is considered (even only later): The dual battery will be 12V. Invest in a DC24-DC12 charger+converter right from the beginning. Otherwise you have to replace the converter by a charger later. (Which is rather not a cost- but a space- and wirering- issue).
- Place the main fuse next to the battery and connect directly to battery 24V terminal. Do not 'steal' from anywhere on the factory harness.
- The DC-DC converter puts a low but constant draw on the battery. Usually the rig can sit for more than a week with no issues, but on longer parking periods you may want to shut it all down. So put a main switch right after the main fuse. You could also place a relais controlled by ignition (see below), but most likely you want the 12V permanently on for camping, fridge and radio memory. I'd go for a manual switch.
- Run only one wire with 24V from the msin fuse & switch into the cab and place the DC-DC converters in the cab. Advantages: Your max load requires a less thick cable on 24V than it would on 12V, and there is little issue in crossing the firewall with one wire. Use an oversized cable, though, to limit voltage drop to the best possible extend.
- Put the DC-DC converter in the cab. Advantage: Lower ambient temperature is better for the device.
- As you draw from your starter battery, you need to monitor or (even better) protect your battery to maintain minimum capacity for a start. So put a voltage gauge and probably a battery protector in the main line. (Some DC-DC converters come with it).
- You will need a point for multiple fuses and distribution in the cab. So put a fuse box with required amount of slots in the cab, as close to the DC-DC output as possible.
- Run cables from that distributor fusebox to the consumers and connectors (radio, sockets, USB etc).
- If you want some 12V appliances to be switched by ignition key (e.g radio):
Place a decently sized 24V relais and wire it like this:
-- 12V from the fusebox to the relais' working circuit.
-- For the control (coil) circuit: 24V from ignition. The Toyota ignition usually has a position 0 (key just in & locked by this release knob), 1 (Certain consumers on, e.g. lighther), 2 (ignition on, run-position), 3 (starter).
Position 1 is what you want. Check which consumers turn on in this position. This may vary by model. In most rigs there is an ignition controlled connector on the harness already to fit a 24V radio. In my BJ73 the lighter is on this position, too. Steal 24V from such an appliances on it's connector, and feed into the relais control (coil). (This is the only occasion where to interfere with the factory harness connectors.)
-- If multiple appliances shall be switched by ignition, you may need a splitting connector or even a 2nd fuse box behind the relais.

- Make sure to apply proper electric Installation best practice ( crimped connectors, shrink tube, cable channel & fixation) and use properly calculated wire gauge, according to expected load.
On longer stretches, consider voltage drop and use oversized cables.

My 12V setup is designed for 240W total load (max load capability of the DC-DC converter). So my main fuse is 20A. My converter, 12V fusebox/distributer and battery protector (with build-in voltmeter) sit at the bottom of the center console. (Under this tray).
I have combos of 1 socket + 2xUSB 3.0 outlets in the trim panels on the front and on the back door, and I have a 2xUSB-inset in the 24V lighter. (Sockets are fused 10A, USB 5A, so that's 30A total -> my setup is not correctly calculated and undersized. I must not use all outlets in parallel at max load!).
There are nice USB outlets that feature a build-in switch and even a voltmeter.
I use USB appliances as far as possible as those draw minimum load, e.g. USB-based LED lights for camping, Bluetooth speaker. Only my fridge utilizes a socket.

Good Luck on your project.
Cheers Ralf

 

[bj70bc]

Hi
I would suggest to 1. bring the 24V setup back to close to factory standard and eliminates any 12V crappy installations.
Clock always on is normal, lighter probably too (depends on model).
Then 2. add a thoroughly designed separate 12V setup with a 24V to 12V converter.
To design this you should carefully think about where in the car you need what power for what type of appliances. Also consider whether there is a need for a dual battery setup. First you need to calculate the maximum power (Watt=Amps*Volts) your desired appliances would draw. This determines the size of DC-DC converter, main fuse rating and main wire gauge to use.
On general bases (and based on my own experience and mistakes):
- If a dual battery setup is considered (even only later): The dual battery will be 12V. Invest in a DC24-DC12 charger+converter right from the beginning. Otherwise you have to replace the converter by a charger later. (Which is rather not a cost- but a space- and wirering- issue).
- Place the main fuse next to the battery and connect directly to battery 24V terminal. Do not 'steal' from anywhere on the factory harness.
- The DC-DC converter puts a low but constant draw on the battery. Usually the rig can sit for more than a week with no issues, but on longer parking periods you may want to shut it all down. So put a main switch right after the main fuse. You could also place a relais controlled by ignition (see below), but most likely you want the 12V permanently on for camping, fridge and radio memory. I'd go for a manual switch.
- Run only one wire with 24V from the msin fuse & switch into the cab and place the DC-DC converters in the cab. Advantages: Your max load requires a less thick cable on 24V than it would on 12V, and there is little issue in crossing the firewall with one wire. Use an oversized cable, though, to limit voltage drop to the best possible extend.
- Put the DC-DC converter in the cab. Advantage: Lower ambient temperature is better for the device.
- As you draw from your starter battery, you need to monitor or (even better) protect your battery to maintain minimum capacity for a start. So put a voltage gauge and probably a battery protector in the main line. (Some DC-DC converters come with it).
- You will need a point for multiple fuses and distribution in the cab. So put a fuse box with required amount of slots in the cab, as close to the DC-DC output as possible.
- Run cables from that distributor fusebox to the consumers and connectors (radio, sockets, USB etc).
- If you want some 12V appliances to be switched by ignition key (e.g radio):
Place a decently sized 24V relais and wire it like this:
-- 12V from the fusebox to the relais' working circuit.
-- For the control (coil) circuit: 24V from ignition. The Toyota ignition usually has a position 0 (key just in & locked by this release knob), 1 (Certain consumers on, e.g. lighther), 2 (ignition on, run-position), 3 (starter).
Position 1 is what you want. Check which consumers turn on in this position. This may vary by model. In most rigs there is an ignition controlled connector on the harness already to fit a 24V radio. In my BJ73 the lighter is on this position, too. Steal 24V from such an appliances on it's connector, and feed into the relais control (coil). (This is the only occasion where to interfere with the factory harness connectors.)
-- If multiple appliances shall be switched by ignition, you may need a splitting connector or even a 2nd fuse box behind the relais.

- Make sure to apply proper electric Installation best practice ( crimped connectors, shrink tube, cable channel & fixation) and use properly calculated wire gauge, according to expected load.
On longer stretches, consider voltage drop and use oversized cables.

My 12V setup is designed for 240W total load (max load capability of the DC-DC converter). So my main fuse is 20A. My converter, 12V fusebox/distributer and battery protector (with build-in voltmeter) sit at the bottom of the center console. (Under this tray).
I have combos of 1 socket + 2xUSB 3.0 outlets in the trim panels on the front and on the back door, and I have a 2xUSB-inset in the 24V lighter. (Sockets are fused 10A, USB 5A, so that's 30A total -> my setup is not correctly calculated and undersized. I must not use all outlets in parallel at max load!).
There are nice USB outlets that feature a build-in switch and even a voltmeter.
I use USB appliances as far as possible as those draw minimum load, e.g. USB-based LED lights for camping, Bluetooth speaker. Only my fridge utilizes a socket.

Good Luck on your project.
Cheers Ralf

thanks
that was easy to understand, i need to improve my setup

 

[robmobile73]

When you go with a 24-12V converter make sure you wire it to something that is only on with the ignition. If you don't it will kill your battery in 5-8 days from parasitic idle current from the converter.

You can buy a stereo that will run on 24V if you don't want to deal with the converter just for the stereo.

Splitting between the batteries for 12V will kill a battery eventually. A momentary load may be OK..Maybe, but not any constant load even if small.