diy solar

diy solar

Alternator to battery wires

D

davelondon

Guest
I'm installing a Balmar 48V, 100A alternator in my expedition vehicle, and I need to decide which wiring I'd like to connect it to the batteries with. It will be a long run (10-15m) and it'll be along the chassis rails under the vehicle, so a pretty harsh environment. What type of cable do I need?

For 100A @ 15m with 1% loss, I'll be needing a 150mm2 conductor according to this calculator.

Is "double insulated" cable OK or should I be thinking about armoured cable? I guess that would be tricky to route around the chassis components because it's not flexible.

This stuff looks good but the spec sheet says it's only rated down to temperatures of 0C... I want the truck to operate down to -30C.
 
That's going to be $$$$

Secondly, I would prefer tinned or similar leads, since that limits the amount of corrosion on the copper. Usually for marine environment, but I would consider underneath a vehicle to the same category, so I would recommend looking into the marine-rated stuff.
Rain is 'relatively easy' to handle, but with -30 operations underneath.. salt and snow are basicly THE killer for any electrics, similar to sea/marine environments....
That usually is also fine stranded, which is preferred for a vibrating environment.

Also, consider running 2x70mm2 conductors, 150mm2 is hard to handle to say the least. 2x 70mm is much easier to handle, and there is decent availablility of lugs and so on. For additional protection you might run it through a conduit.

Since you're referring to mm2 and linking to a UK site and your nickname, I assume you're in the UK :)

Just some googling:
 
  • Like
Reactions: Zil
What DJSmiley said. /\
Adding 48 volts is not fun to play. I would shield the cable in maybe PVC conduit.
 
Polar Flex is good stuff, but the jacket is rather soft. Run it in a protective wire loom to minimize abrasion.
 
100 amps
100 feet(15 meters x 2)
48 volts
< 3% loss

I get 1 AWG minimum which is approximately 50mm2.

 
I didn't recalculate, but I think that's more accurate.

http://www.polz.info/leitungsrechner/ says 4.46% loss with 50mm2.
I think you will be good with using 70mm2, or 2x50mm2 if you want to be on the safe side.

With 30m of total wirelength that still saves a nice amount.

If I check at the previous linked site it's 5 GBP/meter saving. Assuming with 2 wires the total run would be 60m cable, that's 300 GBP cheaper
(Still, 4 wires of 15m is 60m x 10 GBP is 600 GBP)....
 
100 amps
100 feet(15 meters x 2)
48 volts
< 3% loss

I get 1 AWG minimum which is approximately 50mm2.


That works for most of us that shoot for 3% or lower voltage loss. Dave said he wants a 1% loss in the original post, which is going to require 2/0 to be in the 1% "range" (less than 2%, but the actual number is 1.66%).

100' of 2/0 welding cable would cost me about $400. Would I use welding cable underneath a vehicle? It would depend on how well I can protect it. I have a boxed frame on my truck and I can run the cable through the frame instead of on the outside of the frame.
 
That works for most of us that shoot for 3% or lower voltage loss. Dave said he wants a 1% loss in the original post, which is going to require 2/0 to be in the 1% "range" (less than 2%, but the actual number is 1.66%).

100' of 2/0 welding cable would cost me about $400. Would I use welding cable underneath a vehicle? It would depend on how well I can protect it. I have a boxed frame on my truck and I can run the cable through the frame instead of on the outside of the frame.
Actually using OP's calculator I get 150mm2 for 1% voltage drop.

150mm2 ~= to 300MCM.

This is a piece of 250MCM for scale.
20211203_105313.jpg
 
It’s OK I was expecting this cable run to be expensive so my liver is already boxed up and ready to ship out.

That’s great news that two smaller cables will do the same job as one larger.

In that case then this stuff looks good… still expensive though…
 
100 amps
100 feet(15 meters x 2)
48 volts
< 3% loss

I get 1 AWG minimum which is approximately 50mm2.


Hey, question: with this calculator, should the distance I enter be the total length of both positive and negative wires? e.g. 30m? Or just the total length of each - e.g. 15m? It says "power source to load" so I assumed it was just 15m...
 
Hey, question: with this calculator, should the distance I enter be the total length of both positive and negative wires? e.g. 30m? Or just the total length of each - e.g. 15m? It says "power source to load" so I assumed it was just 15m...
"4 - Enter length of cable run required [power source to load]."

That indicates one way.
I compared it to my calculator of choice and the one way length tallies.
 
Last edited:
Hey, question: with this calculator, should the distance I enter be the total length of both positive and negative wires? e.g. 30m? Or just the total length of each - e.g. 15m? It says "power source to load" so I assumed it was just 15m...

The calculator on the Bay Marine Supply web page is the round trip length. It says that in the box to the right of where you enter the length. If the calculator you linked to needs round trip, it doesn't say one way or the other. If you compare the two calculators and enter similar numbers, I come up with needing to use the one-way length in your calculator.
 
In 2004, we purchased a used Honda Odyssey to pull small campers. I used eTrailer (I think) and they provided all the wiring needed from our Odyssey battery to our WFCO along with the ability to shut off the charging when the ignition was off. We used 8 awg wire ran along the frame to an Anderson (?) connector at the ball, and 8 awg wire to the WFCO. I did use plastic wire loom to protect the wires and we drove on gravel roads nearly every camping trip. Two years ago the Odyssey finally died at 277,000 miles of which at least 100,000 miles were pulling our small campers.

I would inspect the wires at least once a year and never had a problem.

All we needed to completely charge the single lead acid battery (series 27 or 31) was about a 100 mile drive. Worked great until we retired and began boondocking more than just a weekend.

Food for thought,

Perry
 
It will be a long run (10-15m) and it'll be along the chassis rails under the vehicle, so a pretty harsh environment. What type of cable do I need?
Why on the frame and not inside the living box?

Inside the frame rails is usually pretty good protected.
e.g. 30m? Or just the total length of each - e.g. 15m? It says "power source to load" so I assumed it was just 15m...
I had a few projects - with just adding a few ground straps to the engine and using the frame as a return, without any issues.

And I already hear all the comments of multiple groundpaths - the alternator is your reference ground. It doesn't matter if you got 1 or 10 straps from the block to the frame. Many modern vehicles have more then one ground strap. It goes all the same point - the alternator.

When you create issues is actually - going from the alternator directly to the battery - and then ground that battery additionally on the other side of the chassis (some inverters/ chargers) are grounding.
 
When you create issues is actually - going from the alternator directly to the battery - and then ground that battery additionally on the other side of the chassis (some inverters/ chargers) are grounding.
Can you say that again but in slightly different words?
I'm having trouble parsing your meaning.
 
Alternator - battery not grounded.JPG

Can you say that again but in slightly different words?
here a picture of my mental image. You by not using the frame - you are potentially creating a secondary path- through a grounding inverter/or charger. Because the wire has the lower resistance then the frame.
 
Use DLO cable, it is very flexible and very tough, I ran it under my truck and added spiral protective wrap to it. I went 1/0 but for a 12v system.

DLO Cable
 
Yes that's an option, but space is at a premium inside the living box!
You were asking about a 15m cable so I assumed that your vehicle is 10m long or so.

Nothing where I would have thought space is at a premium. I built a off-road camper van and had all wiring inside, with only 6m long.

Now I got 7m box RV and I got so much space where I can not seem to know what to do with it
 
Back
Top