Slave 24v to 12v conversion?

[gunsgreg]

I must preface this by saying I am not electrically inclined so I thought I might get some advice here.

I have a nicely functioning 24v slave receptacle on my M923A2 5 ton. Is it possible or practical to install a slave on my civilian 12v Hummer? Possibly with a 24v to 12v converter downstream from the Hummer slave receptacle? I do not understand how a high amp converter and / or slave system functions, does it go both ways? Any other possibilities? If there is no good way to make them play together I'll keep them separated...

Sorry if a dumb question but I think I am at least smart enough to ask rather than burning something down...
Thanks

 

[74M35A2]

A converter would not be able to handle starter current. May work ok for just charging.

I installed a duplicated slave port and wired it to the first battery in series so it is a 12V slave port for jumping civilian junk. Just labeled one 24v and the other 12v.

 

[gunsgreg]

Thank you 74M35A2. So the slave port you are using for the 12v is also a standard one pin NATO unit it just has 12v coming out instead of 24v?

 

[74M35A2]

Correct. Below is link and pic. I found a very handy area to mount it, since the cab corner has an impressed are that would be hard to replicate. My "slave cables" have a 500A NATO single pin connector on one end, and traditional jumper cable clamps on the other. I used fine strand welding cable to keep them flexible and easy to roll up tightly to store.

Sure, it is not as handy if doing an MV-MV jump, but I only own one MV anyway, the cables can now be clipped to anything, 12V or 24V.

http://www.steelsoldiers.com/showthread.php?144044-12V-Jump-Port

 

[tim292stro]

I'll take a moment to point out that if you put an industry standard slave port on a vehicle, anyone other than you who plugs into it is going to expect it to work the way the industry standard suggests (read this thread). I say this because if you're putting a 24V NATO plug on a truck that is wired for only 12V (but looks like the military version that really did have a 24V NATO port), then first "helpful" Steel Soldier or MV enthusiast to see your slave port and plug in before you notice will kill your truck.

There are industry standard 12V jump ports used by tow trucks all over the place (they use Anderson Power Products or similar connectors).

 

[steelandcanvas]

There are industry standard 12V jump ports used by tow trucks all over the place (they use Anderson Power Products or similar connectors).

Best idea yet. No mistakes this way.

 

[gunsgreg]

Point (s) taken and appreciated.

 

[gunsgreg]

I'm a 24v guy living in a 12v world. Trying not to turn my electrical ideas into a
Est wise arc welder...

 

[tim292stro]

As for the Voltage converter idea - a diesel engine on a HMMWV will pull about 800CCA with 24V and about 950-1100CCA with 12V. A step-down converter (24V batteries, 12V load) would have to support that load directly (you're looking at a current output level that is just not "cheap"). If you were to try the other direction (12V batteries, 24V load) your batteries would have to be able to source double the current demand of the load:

Power = Volts x Amps

A 24 Volt starter pulling 800 Amps is (800A x 24V = 19.2kW), to pull that 19.2kW from a 12V supply you'd need a battery and converter that can do: 19200W / 12V = 1600Amps (double the current, half the voltage). You're looking at something like two Group 31's in parallel to do that.

Easier to have a 12V jump port on your M923 for your Hummer, or get a dual voltage jump pack. - which takes about as much space as one NATO Slave cable set. Cut off the clamps and add an Anderson connector to make the clamps changeable with a NATO plug. Done

 

[goldneagle]

As for the Voltage converter idea - a diesel engine on a HMMWV will pull about 800CCA with 24V and about 950-1100CCA with 12V. A step-down converter (24V batteries, 12V load) would have to support that load directly (you're looking at a current output level that is just not "cheap"). If you were to try the other direction (12V batteries, 24V load) your batteries would have to be able to source double the current demand of the load:

Power = Volts x Amps

A 24 Volt starter pulling 800 Amps is (800A x 24V = 19.2kW), to pull that 19.2kW from a 12V supply you'd need a battery and converter that can do: 19200W / 12V = 1600Amps (double the current, half the voltage). You're looking at something like two Group 31's in parallel to do that.

Easier to have a 12V jump port on your M923 for your Hummer, or get a dual voltage jump pack. - which takes about as much space as one NATO Slave cable set. Cut off the clamps and add an Anderson connector to make the clamps changeable with a NATO plug. Done

I actually did that with my 12/24 volt battery charger at home. I installed a "Anderson connector" on the wire leads and made 2 cables with "Anderson connectors" on one end and either a NATO plug or clamps on the other end. That way I can charge my trucks using the NATO receptacle.

 

[Recovry4x4]

I have Anderson connectors on many items. The M1010/ambulance even comes with a yellow 175A Anderson in the patient compartment. There are color standards for Anderson's dealing with volatage but it isn't always followed.

 

[zebedee]

This may be a surprise to many, I got some raised eyebrows at the GA rally on said topic, but NATO slave receptacles in the rest of the world are NOT specific to 24v. It is expected that the operator can read.....

They are the same for 12 and 24v. Just like truck to trailer wiring : there is a stencil, data plate or now stickers, that states what voltage the vehicle socket/plug is so that appropriate voltage/trailer is used. NB. This was correct before LED's - I do not know if things have changed since LED introduction.

Wreckers carry only two interstart cables - NATO-to-NATO and NATO-to-'crocodile clips' (alligator clips). Not all NATO vehicles had interstart sockets so civi battery jumping was the option. Voltage was checked and the appropriate socket on the wrecker was selected or if slaving general vehicles (not a wrecker), a similar voltage vehicle was used.

Australian M816. Both 12v and 24v sockets. NB. NO STENCILS as "You were expected to know every last nut and bolt of YOUR truck and only you and your oppo (Soldier 'B') was allowed to use it." Direct quote from the Recovery Mechanic who used this actual truck in the Army - truck now at Bandianna museum. (Only wreckers in the Australian army were dedicated to drivers - other vehicles had stencils for 'any' driver ie., tyre pressure.)


I could see that this may be an issue - especially when there is an apparent need to stencil 'diesel fuel only' etc., or other such "derr" statements. (UK, Euro, Commonwealth military standards for filler caps/jerrycan ID's etc., are red for 'Petrol' and Yellow for Diesel. Just as the colour coded 'manhole covers' in all US gas station forecourts)