200 amps to the rear of a power wagon?

[Roloc]

200A is quite a lot of power, and the cable size required to support that would be expensive and heavy, so my first question is do you really need that kind of amperage capacity. :)

1) Is the plan to put a second battery in the camper? If so, how do you plan to charge it? If charging off the alternator using a DC-DC system then you really only need to tie the batteries together with wire sized to handle the output of the DC-DC charger. Then you could just run your accessories off the second battery, and not need large wires to the front battery.

2) What is the expected total draw of all your accessories? LED lights and a fridge don't draw that much, so even if you were running them off the main battery in the engine bay I think 200A would be overkill. On the other hand, if you are using an induction stove or larger air compressor that could increase your needs.


Even if the Garmin PowerSwitch and fuse block are each rated for 100A that doesn't mean you'll ever realistically need that kind of power. You can definitely use a smaller wire to power them as long as it is protected with an appropriately sized fuse, it just means that you wouldn't be able to load both to their maximum capacity at the same time.

First off let me say you're absolutely correct it is probably more power than I will need. I am trying to future proof it a bit so I only have to do this once. So the Garmin power switch fully loaded would be 100amp and the fuse block would be 100amp so I am running 200amps just so if I hit those I don't have to run another main. Kind of buy once cry once... that being said I plan on hooking my portable air compressor up via a Anderson plug, and potentially install a compressor for my suspension air bags, we boost, fridge, and also planning on plugging my trailer into it when I need to have electricity there so It is possible with the fans heaters, water pumps etc I get there but as you said not likely I have all that on at once. I always heard to go larger than you need on the wires so that if you do it doesn't start a fire so that is why I listened to the 2/0 advice instead of my ignition 1AWG.

Now the grounds I think I have figured out as I talked to a couple other people as well. I will run a negative to negative connection to both batteries. Then my redarc BCDC charger will go to the same ground the main battery goes to (it has to in order to detect when it is in use). Then I will ground the rear busbars to the truck frame that will save me from having to run all of that 2/0 wire back to the ground up front. I am going to eventually add a Anderson plug to charge the second battery off of solar from the rear as well but that will obviously need to be a separate run of cable and will be much smaller.

 

[slomatt]

I always heard to go larger than you need on the wires so that if you do it doesn't start a fire so that is why I listened to the 2/0 advice instead of my ignition 1AWG.

You've probably already consulted a 12v wiring chart, but here is one just in case. This chart assumes pure copper wires (not CCA) with a wire insulation rating of 105°C. You then need to decide if you want a maximum 10% or 3% voltage drop and how long your wire run will be before you can look up the proper wire gauge. The really important thing is to protect the wire with a properly sized fuse or circuit breaker placed as close to the battery's positive terminal as reasonably possible.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

The fuse protects the wire from over heating due to excess current. Another cause of an electrical fire can be if the wire shorts to ground, such as if a sharp edge of the frame cuts through the insulation over time. This is why the fuse should be close to the battery to minimize the unprotected length of wire.

 

[M Rose]

You've probably already consulted a 12v wiring chart, but here is one just in case. This chart assumes pure copper wires (not CCA) with a wire insulation rating of 105°C. You then need to decide if you want a maximum 10% or 3% voltage drop and how long your wire run will be before you can look up the proper wire gauge. The really important thing is to protect the wire with a properly sized fuse or circuit breaker placed as close to the battery's positive terminal as reasonably possible.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

The fuse protects the wire from over heating due to excess current. Another cause of an electrical fire can be if the wire shorts to ground, such as if a sharp edge of the frame cuts through the insulation over time. This is why the fuse should be close to the battery to minimize the unprotected length of wire.

According to his specs from the first post and the chart you posted, I still come up with 2/0 wire needed. Also this chart assumes both the positive and negative sides are being run, dropping to only the positive cable, you need to increase by 2 wire gauges in diameter to make up for the losses generated by steel frames.

 

[Roloc]

According to his specs from the first post and the chart you posted, I still come up with 2/0 wire needed. Also this chart assumes both the positive and negative sides are being run, dropping to only the positive cable, you need to increase by 2 wire gauges in diameter to make up for the losses generated by steel frames.

yup and those specs haven’t changed just trying to figure out the grounds.

so if I were going to run the negative wire all the way back to the front where would I ground it? The negative terminal of the second battery? Then run a cable between the negative of the main battery and the second battery?

 

[leeloo]

Who is going to supply those 200 amps ? Just curious. You plan to install a second alternator ?
most DC-to DC converters rarely go over 40 -50 amp and only for short periods. with a 40 amp DC to DC you can charge easy 200 amp of lifepo4..
So you get 40 amps to back , get a DC to DC and install the aux battery there. The peak draw is supplied by the aux battery, you don't need to charge it back instantly.. You need more power in the back, you install a bigger battery, or add another one..
Even 40 amp on this smart alternators is no small amount and it can kill the alternator prematurely if it is a sustained draw..I honestly rarely seen even on big vehicles stock alternators larger than 120 amps. And 120 amps were like maximum for short periods only..

 

[Roloc]

yup and those specs haven’t changed just trying to figure out the grounds.

so if I were going to run the negative wire all the way back to the front where would I ground it? The negative terminal of the second battery?

Who is going to supply those 200 amps ? Just curious. You plan to install a second alternator ?
most DC-to DC converters rarely go over 40 -50 amp and only for short periods. with a 40 amp DC to DC you can charge easy 200 amp of lifepo4..
So you get 40 amps to back , get a DC to DC and install the aux battery there. The peak draw is supplied by the aux battery, you don't need to charge it back instantly.. You need more power in the back, you install a bigger battery, or add another one..
Even 40 amp on this smart alternators is no small amount and it can kill the alternator prematurely if it is a sustained draw..I honestly rarely seen even on big vehicles stock alternators larger than 120 amps. And 120 amps were like maximum for short periods only..

yeah it’s going to be a second battery charged by a redarc bcdc charger so a combo of alternator when the car is running and solar power when running and off.

But it isn’t like I’ll have 200amps going all the time but I don’t want to have to do the mental math every time I turn something on to calculate my amps to see if the next one will blow a fuse or not or worse melt a wire.

 

[leeloo]

What red arc do you have ? The exact model. So if you have the Redarc 1240, the biggest one they have on offer, it will draw max 40 amps. In the manual you have from it, also available online, they will give you the specs with a little headroom of course. . In case of the 1240 they recommend 60 amp rated wire and fuse. More that that is useless, the DC to DC will not be able to draw that kind of amp. It will never go that high and it is pointless.
So between the main battery and the DC to DC that stays in the back and as close as possible to the aux battery you need maximum 60 amp rated wire and fuse. You can put the earth where ever on the chassis as long as it is checked and solid. I did this installation on 3 vehicles.
I kind of doubt that you will have any DC to DC able to draw more in the near future. .. 40-50 maps is as big as they get for many reasons, first there is no market for them and second very few alternators ( unless you talk about some very special rigs, huge trucks ) will be able to support them. with a 1240 DC to Dc you can charge battery banks larger than 200 AMPS . Quote from the manual "BCDC1240D is used for battery bank sizes over 200AH "

 

[Roloc]

What red arc do you have ? The exact model. So if you have the Redarc 1240, the biggest one they have on offer, it will draw max 40 amps. In the manual you have from it, also available online, they will give you the specs with a little headroom of course. . In case of the 1240 they recommend 60 amp rated wire and fuse. More that that is useless, the DC to DC will not be able to draw that kind of amp. It will never go that high and it is pointless.
So between the main battery and the DC to DC that stays in the back and as close as possible to the aux battery you need maximum 60 amp rated wire and fuse. You can put the earth where ever on the chassis as long as it is checked and solid. I did this installation on 3 vehicles.
I kind of doubt that you will have any DC to DC able to draw more in the near future. .. 40-50 maps is as big as they get for many reasons, first there is no market for them and second very few alternators ( unless you talk about some very special rigs, huge trucks ) will be able to support them. with a 1240 DC to Dc you can charge battery banks larger than 200 AMPS . Quote from the manual "BCDC1240D is used for battery bank sizes over 200AH "

It is Redarc BCDC1240D It will be an AGM battery and the mount I am getting will hold a size 47.

Please take whatever I say next as ignorance and I am not trying to disagree I just don't know. Isn't the max draw on the battery (in this case 200amps peak) different from the charge power. of the alternator? To be clear there will not be a 200amp draw on this constantly. I just am designing it to support that much at peak.

In my mind I could draw 200amps with this setup at a spike of say 5-10 minutes which the battery would be able to give easily and then you can charge it back at 50 amps over a greater period of time.

 

[leeloo]

I was just trying to understand your goal so I can advise you. Nobody is born with knowledge, I know some stuff about this because I did it on 3 vehicles..


the peak draw for the BCDC1240D is 40 amps. Not matter what you wish for, it is physics. Even at 40 amps, if it stays there more than 10 min the red arc will burn itself. Most of the times, and considering you will charge an AGM, (that is not the fastest charging type of battery you will draw maybe 25 amps ) . Any Lithium battery can accept the max that the red arc can deliver , the peak 40 amps. With some head room and to avoid loss of voltage they recommend something a bit bigger, 60 amps capable wire

length there is in m, but 9 m is about 29 feet , so an AWG 4 in your case will do fine.
On my Hilux pickup, before I got the redarc, I had a simple Voltage sensing relay, I had a 70 amp rated cable. In my case a 5 m wiring kit was enough, Hilux is about the same size pick up as a Ford Ranger in the US to give you an idea..
For the earth I had a 3 feet cable that I bolted on the tub.. it did fine. It was charging a 55 amp Lifepo4 extremely fast, from 50 % to 95 % in about 30 min of driving.
. Going for a 100 amp or 200 amp cable is serious overkill and waste of money . You are talking about amperages that occur in pure electrical cars only...
I hope this helps..

 

[Roloc]

I was just trying to understand your goal so I can advise you. Nobody is born with knowledge, I know some stuff about this because I did it on 3 vehicles..


the peak draw for the BCDC1240D is 40 amps. Not matter what you wish for, it is physics. Even at 40 amps, if it stays there more than 10 min the red arc will burn itself. Most of the times, and considering you will charge an AGM, (that is not the fastest charging type of battery you will draw maybe 25 amps ) . Any Lithium battery can accept the max that the red arc can deliver , the peak 40 amps. With some head room and to avoid loss of voltage they recommend something a bit bigger, 60 amps capable wire
View attachment 209606
length there is in m, but 9 m is about 29 feet , so an AWG 4 in your case will do fine.
On my Hilux pickup, before I got the redarc, I had a simple Voltage sensing relay, I had a 70 amp rated cable. In my case a 5 m wiring kit was enough, Hilux is about the same size pick up as a Ford Ranger in the US to give you an idea..
For the earth I had a 3 feet cable that I bolted on the tub.. it did fine. It was charging a 55 amp Lifepo4 extremely fast, from 50 % to 95 % in about 30 min of driving.
. Going for a 100 amp or 200 amp cable is serious overkill and waste of money . You are talking about amperages that occur in pure electrical cars only...
I hope this helps..

That does help and I appreciate the advice and I’m learning a ton here so thank you.

Just to further my understanding if I have a PowerSwitch and a fuse block that can support 100amps both why wouldn’t I engineer the system to support that much through the main wire? Is it just to save costs that’s important I agree but I already bought the wire so that’s out the window. Isn’t it safer to always size up your wire anyways? So I know I won’t be hitting 200amps all the time and maybe never but it just seems to me that going larger is always on the safe side of things when it comes to electricity. Maybe not the most cost effective but I am less likely to burn down my power wagon that way.

 

[leeloo]

the fuse needs to be as close to the amps of the BC DC to protect it. You want the fuse to blow as fast as possible, before damage and fires occur. . At 100 amps the redarc, which is pretty expensive will be long gone . You will need to wire in 2 fuses actually, one imediatly after the main battery and another just before the red arc. In your case the fuses need to be 60 amps, as described in the manual at page 3, link below.

https://www.redarc.com.au/Content/Images/uploaded/Manuals/BCDC%20Instruction%20Manual.pdf

You don't need that power switch . Is another failure point you introduce. But of course, you can if you want to. No idea what your particular use scenario is.
The redarc will detect when your car starts, waits a bit for the main batt to charge and starts charging the aux. If you have a solar panel permanently fixed on your vehicle, it will take first what ever power comes from solar and add only what ever is need it from the main. While on solar, if the aux is full, it will charge the main batt as well.
In my case the aux battery I have it in a battery box, connected to the red arc with a 50 amp rated anderson plug so I can remove it easy. When I am not on trip, I remove it and keep it on charger- maintainer in the garage, the redarc detects that it is removed and it shuts itself down, no longer drawing any power. So no need for the extra switch.


The wiring should be like this.. Positive terminal on main batt > aprox 20 cm of wire > 60 amp fuse > wire to the back > 60 amp fuse as close to the red arc as possible, max 50 cm I would say .

 

[Roloc]

the fuse needs to be as close to the amps of the BC DC to protect it. You want the fuse to blow as fast as possible, before damage and fires occur. . At 100 amps the redarc, which is pretty expensive will be long gone . You will need to wire in 2 fuses actually, one imediatly after the main battery and another just before the red arc. In your case the fuses need to be 60 amps, as described in the manual at page 3, link below.

https://www.redarc.com.au/Content/Images/uploaded/Manuals/BCDC%20Instruction%20Manual.pdf

You don't need that power switch . Is another failure point you introduce. But of course, you can if you want to. No idea what your particular use scenario is.
The redarc will detect when your car starts, waits a bit for the main batt to charge and starts charging the aux. If you have a solar panel permanently fixed on your vehicle, it will take first what ever power comes from solar and add only what ever is need it from the main. While on solar, if the aux is full, it will charge the main batt as well.
In my case the aux battery I have it in a battery box, connected to the red arc with an anderson plug so I can remove it easy. When I am not on trip, I remove it and keep it on charger- maintainer in the garage, the redarc detects that it is removed and it shuts itself down, no longer drawing any power. So no need for the extra switch.


The wiring should be like this.. Positive terminal on main batt > aprox 20 cm of wire > 60 amp fuse > wire to the back > 60 amp fuse as close to the red arc as possible, max 50 cm I would say .

That's extremely helpful on the redARC thank you!

I will absolutely fuse the RedArc and the main cable to the back right there at the battery.

One thing that still throws me though and I am possibly not understanding the RedArc in this equation is that you seem to be implying that the redarc will be overrun with 200 amps but the constant draw on it will be as you stated far lower like probably less than < 10amps at a time. In that scenario the RedArc should be ok right? If it draws 200amps for 5-10 minutes then settles back down to the < 10 ampsI am not going to burn out the RedArc am I?

 

[leeloo]

you can have 1000 amps ready to go at the main bat , the red arc will only use 40 of them maximum, and only for short periods it can stay at 40, 10 min usually. It will never draw 200 amps unless there is a short somewhere, and that is why you have fuses. This is what it means when you hear "peak amps " or "peak power " ..
The only thing that will hurt the red arc in this scenario is higher voltage than what is rated for. It works kind of like a pipe with water..
Lets imagine you have a huge water tank with a very thick pipe, that can supply water to a city . If on that pipe you plug a tiny garden hose, no matter how big that pipe is, the water that is coming is only what ever that tiny hose can take. In this case, the huge pipe is your 100 amp wire and the tiny garden hose is your red arc..

 

[Roloc]

you can have 1000 amps ready to go at the main bat , the red arc will only use 40 of them maximum, and only for short periods it can stay at 40, 10 min usually. It will never draw 200 amps unless there is a short somewhere, and that is why you have fuses. This is what it means when you hear "peak amps " or "peak power " ..
The only thing that will hurt the red arc in this scenario is higher voltage than what is rated for. It works kind of like a pipe with water..
Lets imagine you have a huge water tank with a very thick pipe, that can supply water to a city . If on that pipe you plug a tiny garden hose, no matter how big that pipe is, the water that is coming is only what ever that tiny hose can take. In this case, the huge pipe is your 100 amp wire and the tiny garden hose is your red arc..

Ok I love that analogy and I think we're saying the same thing I am just doing a bad job of articulating it.

Say you have a pool of water and a very think pipe coming out and you only turn the thick pipe on once a week for 30 min but you leave the garden hose going all week and it shuts off when it is full, then theoretically you're fine right the pool will never empty. I am not talking about 200amps constantly. Just for short bursts at a time so I want to be able to pull 200 amps but not constantly. But you have got me worried that somehow the RedArc will blow up if I do that.

 

[leeloo]

Kind of like that. . Curent works like this..

Voltage is the water pressure . That will not change a lot. It will be around 13.2 - 14.4 V for smart alternators,( no matter the output, a small 80 amp like in your average SUV or some uprated monster for a 6.8l Diesel Cummins at 150 amps - the voltage is more or less the same). Current flowing is the amps, in your case how much water is flowing trough the pipe. You wire - your pipe - can do maximum 100 amps at that voltage - water pressure . But the redarc will never require more than 40. If that happens, it is an anomaly, a serious malfunction somewhere, a short circuit most likely, and this is why you have fuses, so you don't overheat anything, catch fire and destroy expensive things like the BC DC or worse, your car..

 

[Roloc]

Kind of like that. . Curent works like this..

Voltage is the water pressure . That will not change a lot. It will be around 13.2 - 14.4 V for smart alternators,( no matter the output, a small 80 amp like in your average SUV or some uprated monster for a 6.8l Diesel Cummins at 150 amps - the voltage is more or less the same). Current flowing is the amps, in your case how much water is flowing trough the pipe. You wire - your pipe - can do maximum 100 amps at that voltage - water pressure . But the redarc will never require more than 40. If that happens, it is an anomaly, a serious malfunction somewhere, a short circuit most likely, and this is why you have fuses, so you don't overheat anything, catch fire and destroy expensive things like the BC DC or worse, your car..

Ok awesome. Now if the car is shut off and I am drawing 200 amps MAX would that effect the BCDC in any way assuming I have the fuses in place in front of the BCDC which would be a 40amp fuse? Like that wouldn't blow the fuse or somehow go back up into the BCDC wire would it?

 

[M Rose]

Ok awesome. Now if the car is shut off and I am drawing 200 amps MAX would that effect the BCDC in any way assuming I have the fuses in place in front of the BCDC which would be a 40amp fuse? Like that wouldn't blow the fuse or somehow go back up into the BCDC wire would it?

The BCDC charger doesn’t care how many amps are being pulled from the batteries… The BCDC sees a draw while the engine is running and starts the charge process.
Also, I might have missed it, but what kind of batteries are you planning on running for both start and auxiliary batteries? If they are both AGM and they are both the same size, then the stock alternator can keep up without the BCDC charger. I mean the Diesel version of your truck runs dual batteries with the same alternator without any kind of smart charge controller. The only thing you need a charge controller for is adding solar power.

 

[Roloc]

The BCDC charger doesn’t care how many amps are being pulled from the batteries… The BCDC sees a draw while the engine is running and starts the charge process.
Also, I might have missed it, but what kind of batteries are you planning on running for both start and auxiliary batteries? If they are both AGM and they are both the same size, then the stock alternator can keep up without the BCDC charger. I mean the Diesel version of your truck runs dual batteries with the same alternator without any kind of smart charge controller. The only thing you need a charge controller for is adding solar power.

You didn't miss it cause I didn't say and am still researching that part. I was thinking going with AGM Optima yellow top which would be different than the flooded OEM battery in there. So they will be different types but I also want to add solar charging in there as well so that's how I got with the BCDC.

 

[leeloo]

Not sure from where you get this 200 amps thing. There is nothing that can draw 200 amps in a a normal car. that is a short. If that particular circuit is not fused, you catch fire, melt things, bad things happen . There are very few things that can draw even 40 or 60 on a particular circuit in a car. . Hence all over your car you have all this boxes of fuses and each circuit has their own fuse rated for the job. If the circuit powering your seat heating is suppose to draw max 20 amps, the wire and fuse will be rated a bit more than that at 25 o or 30 for example, and in one of the fuse boxes in your car you will have a separate circuit for seat heating and a fuse for the seat heating labeled as such - with a 25 amp rating..
You will have all this separate circuits all over you car for this very reason, to be redundant and safe, so if the seat heating brakes down and blows a fuse non stop, you bloody fuel pump still works and you are not stranded because you kid spilled juice on the seat..
So what if you have a induction cooker hooked at the aux battery that can dray a lot of power.. same thing.. it is after the BC DC and the aux battery and between the aux battery you will have a wire with another fuse..

 

[M Rose]

Not sure from where you get this 200 amps thing. There is nothing that can draw 200 amps in a a normal car. that is a short. If that particular circuit is not fused, you catch fire, melt things, bad things happen . There are very few things that can draw even 40 or 60 on a particular circuit in a car. . Hence all over your car you have all this boxes of fuses and each circuit has their own fuse rated for the job. If the circuit powering your seat heating is suppose to draw max 20 amps, the wire and fuse will be rated a bit more than that at 25 o or 30 for example, and in one of the fuse boxes in your car you will have a separate circuit for seat heating and a fuse for the seat heating labeled as such - with a 25 amp rating..
You will have all this separate circuits all over you car for this very reason, to be redundant and safe, so if the seat heating brakes down and blows a fuse non stop, you bloody fuel pump still works and you are not stranded because you kid spilled juice on the seat..
So what if you have a induction cooker hooked at the aux battery that can dray a lot of power.. same thing.. it is after the BC DC and the aux battery and between the aux battery you will have a wire with another fuse..

We aren’t talking about a normal car… we are talking an Overland Specific Truck. If I have my fridge running at max cool, A/C cranked, all 14 KC lightS going, and transmitting a full 100 watts of power, im drawing way more than 200 amps. I know, because I can stall out my 200 amp alternator when I press the TX button to do mobile FT8. And this doesn’t even count the amp draw of a winch, or a standard full-size truck starter. The 2018 Dodge Power wagon draws 700 amps…

Starter 700 amps
KC lights 25 amps/ pair
Coms radio 25 amps (assuming a typical up to 50 watt radio)
Fridge 15 amps
Trailer needs who knows, my TT draws a continuous 150 amps
Winch 500