12Volt Alt on 24Volt System

[FJota]

I am thinking about mounting a second alt on my 24 volt HJ61 to handle all the 12volt accessories. I would then run a 3rd battery. This way I would have plenty of power to run lights, trailer wiring, stereos, gauges and anything else 12 volt. At the present time I have a couple of power converters. I think the one converters is on the way out.

Will I have any issues regarding the common ground or should I keep them isolated?
Are there any other concerns that I should be aware of?

Thanks
Chad

 

[denis]

You can't easily isolate the ground on an alternator, that said the common ground should not be a problem if the two systems are fully isolate.

 

[motorcoach123]

Chad
You might consider running a battery equalizer/vanner (link below) that would keep your present two 'series batteries' balanced as well as provide 12V accessory power off the balancer itself. Much simpler than mounting a second alternator/battery system, not sure about difference in $

Gord


http://www.vanner.com/htm/pro_01.htm?series_sku=3195361503151112&a=a&pt=3

 

[FJota]

I have thought about using my power converter to charge a 3rd battery but I don't think it would keep up with much of an amperage draw. Has any one done this? What amperage is your power converter?

 

[Greg_B]

Looks like an interesting load balancer/converter.

My only caution with running any load balancer full time is you stand a good chance of not being able to start the truck after a few days standing. Especially if it is very cold and the batteries are under more stress. The load balancer will recognize the weaker battery, and draw down the good one. One day you go outside, and the truck will not start, however the batteries are nicely balanced.

You can overcome this by have the load balance line through a relay (if the converter can handle that line switch on and off) to come on with key power, so load balancing only happens when the truck is running.

Always keep in mind your alternator is 30amps @ 24V. Figure your max load (middle of winter, heater on high, wipers on, headlights on highbeams, etc) then see how much is left over (leaving a margin for your alternator so you don't cook it). Ya, not a lot left to use, and what is left you need to be aware of and needs to be managed.

There are folks running 3rd deep cycle batteries charged from a converter. Best would be to run it through a minder, but I know folks that have not.

hth's

gb

 

[Freewheel]

These are questions I've been working on for a while and I can give you a few answers. You can get isolated ground alternators, they are usually for marine use and are more expensive. I have not had any problems, though, running the 12volt stuff to a common ground (I have put large diodes in a few key spots, though, so that current can't flow "backwards"

I looked hard at my HJ engine bay and couldn't figure out how I would elegantly put another alternator and battery in so I went with the 20 amp voltage converter and small 6ah gel cell battery - just big enough to keep the memory on the radio. I ran into a number of problems with the small battery discharging backwards through the converter and putting too much of a load on it to charge properly. I discussed this in another thread which I'll copy here.

I've got a simple converter (on an ignition switched relay) on mine, but I've also got a nifty little gadget that I found necessary in my install. Made by Samlex, It's a passive battery backup power router. Cost $61 CDN. It routes 12V to your accessories and to your backup battery ( to charge it) When the power from the main batteries/alternator is cut off (like when you turn the car off) the backup switches to the 12 v single accessory battery to run your 12v accessories.
I put this in because my converter would not charge the battery properly AND run the radio. ( My auxilary battery is a small 6ah gel cell, and it basically just provides power for the radio memory.)
The converter is a Samlex SDC-23 20 amp 24-12volt converter $109 CAD
the Battery Backup module is BBM-1225 item # 08151 $61 CAD

I had to modify the current limiting resistors in the BBM-1225 so it would not fry the little gel cell - It is designed to charge a full size automotive battery.

Both of these units fit nicely under the dash above the glove box.

I don't know where you'll put a full size battery - thats why I went with the gel.

Oh,and I made the 24-12v converter ignition switched cause I was afraid it would wear on the main batteries if it was left on all the time.

So for your situation, if you still want to charge a full size battery, this may be the way to go. It will depend on your current draw though. The battery and your accessories will be sharing the amperage available from the converter - so when your blazing hard on your 12 volt accessories, there won't be as much power available to charge the battery.
It seems there's a general consensus on the board that you shouldn't go higher that 20 amps for a converter (as Greg says above -your alternator has 30amps at 24 volts which is the equivalent of 60amps at 12 volts- so a 20amp converter can take up to 1/3 of your available current. So you'll have to figure out how much you want running through the 12v system.


I

 

[Greg_B]

I put this in because my converter would not charge the battery properly AND run the radio. ( My auxilary battery is a small 6ah gel cell, and it basically just provides power for the radio memory.I

Interesting. Load balancer/converters typically do not like a large inductive load off the units, so to address this and the mem presets we have worked with a customer and Solar Converters, and have just started offering a strict 24/12 converter @20 amps which has a small lead to supply power for mem preset and clock only. The main converter can be hooked up to turn on and off with key power, leaving this small lead as constant 12V for the preset. The unit can be installed to run the converter full time as well. With full time or key'd power it will stop supplying 12V when it senses less then 24V input; thus saving the starting system.

Your small gel cell is a nice simple solution as well.

gb

 

[FJota]

If I were to mount a 12 volt alt on my 12ht, I should rubber mount it from the engine? What will happen if did not? I really don't want to melt anything down. I just want a reliable 12 volt source

I was thinking about mounting it were the york is in the pic.

 

[arutgers]

I have thought about using my power converter to charge a 3rd battery but I don't think it would keep up with much of an amperage draw. Has any one done this? What amperage is your power converter?

I have such a setup. The converter charges a 60Ah third battery. To prevent drawing current when the car is idle, I have attached the converter to the ACC position of the ignition switch. My converter is 10A. Not too much, but enough for my applications: a radio, a 12V trailer. Sometimes I use an air compressor for about 10 minutes at 30 Amps. It then takes 30 minutes to fully charge the battery.
I have tweaked the converter a little to make it supply enough voltage to charge the battery fully.

Gr Ton

 

[lowenbrau]

I too use a 24-12v converter to charge a third battery when the engine is running. I run all my accesories off it.

One of the locals added a 12v one wire alternator and simply connected it to the low battery in the 24v string and connected all the accesories to that battery. The voltage regulators took care of making sure everything stayed balanced. I was sceptical at first but couldn't argue that it wouldn't work.

 

[bj70_guy]

I too use a 24-12v converter to charge a third battery when the engine is running. I run all my accesories off it.

Bruce, where did you mount your 3rd battery?

 

[lowenbrau]

Bruce, where did you mount your 3rd battery?

Its on a bracket mounted to the rollcage behind the passenger seat and between the drawers and the quarter panel

 

[FJota]

I too use a 24-12v converter to charge a third battery when the engine is running. I run all my accesories off it.

One of the locals added a 12v one wire alternator and simply connected it to the low battery in the 24v string and connected all the accesories to that battery. The voltage regulators took care of making sure everything stayed balanced. I was sceptical at first but couldn't argue that it wouldn't work.

Did he have any problems using a common ground?
I would like to do this but go to a seperate battery. This way I could install a deep cycle battery for the accessories. If the battery is run down I can still start my truck and charge it back up.

 

[lowenbrau]

Did he have any problems using a common ground?
I would like to do this but go to a seperate battery. This way I could install a deep cycle battery for the accessories. If the battery is run down I can still start my truck and charge it back up.

Common ground, yup

 

[bj70_guy]

Its on a bracket mounted to the rollcage behind the passenger seat and between the drawers and the quarter panel

No qualms with having a battery in the cab?
I'm deciding what to do for my 12V needs, and having the extra battery would be nice, as opposed to just using the 20A 24-12V converter for power.

 

[arutgers]

No qualms with having a battery in the cab?

No, never noticed any, and I am using this setup for several years. But ofcourse it's important not to overload the battery.
My Mercedes 209D also had a battery beneath the driver seat, and that's a stock setup.

Gr Ton

 

[haffi]

I had a 12volt aux alternator and third battery installed in my old 62. no problems with common ground.

I might post some pics of my setup this evening if you are interested.

I highly recomend this mod

 

[FJota]

I had a 12volt aux alternator and third battery installed in my old 62. no problems with common ground.

I might post some pics of my setup this evening if you are interested.

I highly recomend this mod

haffi
That is good news. Pics would be great. I am really looking forward to this mod. I am tired of the stereo cutting out when I have a trailer on and make a brake application.

 

[haffi]

In my opinion 12volt alternator is the only right way to power your 12 volt stuff.

Before I had overloaded two or three 24-12volt converters so I had pretty bad experians with that.

I used the 12 volt to power the radio, amplifier, 12 volt cooler, all extra lights (backup, spotlights and a searchllight), mobile phone, VHF radio, water pump for a water to air intercooler, all the original interior lights, the headlights and the heated seats.

The best part was that I could power the radio ond lights witout worries about draining the start power. I used a 75 amp/hours deep cycle battery.

The alternator was a 80 amp Bosch. I installed it over the power steering pump, under the upper cooler hose and re routed the lower hose over the alternator.
I welded a extra pulley to the power steering pulley to make space for the extra belt.

Well some pics, I will try to answer any questions you might have.

Used silicon hoses to re route the cooler pipes.

I used this red battery for few days before I bought me a deep cycle battery.

The yellow light is the charge light for the 12 volts. I made me a 12volt acc, fully swithed on and park lamps power with 24 volt releys.

Used the fully switched on for the charge lamp, and the heated seats, the acc for the radio and the park lamps to power relays and switches for aux lights.

To make the original 24 volt interior lights 12 volt I opened the fuse box and soldired a new wire with 12 volts to the dome fuse instead of the 24 volts. Then just replaced the 24 volt lightbulps with 12 volt bulps.
Then I noticed that the clock in the dashboard was dead, so I had to connect it to another 24 volt power source since it is on the dome fuse with the lights. I also re wired the cigarette lighter with 12 power.

I did the same thing to the headlamp fuses, but for the high beams to work I needed to change the dimmer relay with a 12 volt one, I used a relay from a toyota corolla. And of course changed the bulps.

I dont have that cruser any more so I cant shoot better pics. Dont have any of the bracket I made to hold the alternator.

I had some troubles to stretch the belt, in the beginning. Finally I got bored of the noises from the belt and made me mechanism similar to the orginal toyota stuff. Used a long, treaded bolt to stretch the belt properly. I dont have any pics of that.

 

[FJota]

Thanks for the pics. This is exactly what I was looking for. I like the position of the alt. May have to change my plans alittle.Hope to get started in the next week or two.