48 replies to this topic

[Jsoboti]

Redarc actually recommends 4 or 6awg, depending on the length of the run.  Their install manual goes from 2 to 6, depending on the run. There's a little chart in it. 
And, same as you, only w/ redarc, it did not like the 10awg factory wiring.  Redarc and Mule both suggested I upgrade it, which I did, and problem solved. 
redarc does have a engine sense line, but it is not "required" unless you have a smart alternator. 
I don't have a smart alternator, but maybe connecting that line would have solved the issues I was having w/ voltage drop.. Not sure.. I just ran heavier wire. 

 

Did you just tie the engine sense line right into the positive feed line? I know my 2014 F-350 has a "computer controlled" alternator, but it seems that it is always putting out 13.75 volts and then if it senses it needs it can bump it up to 14.something.

 

Sounds like if the least it's going to put out is 13.75 then I don't need the engine sense line and the RedArc BCDC will just sense the increased voltage via positive input and power the unit on? 

[wicked1]

Did you just tie the engine sense line right into the positive feed line?

 

No, left it disconnected, per the manual.  If you need to use it, the engine sense line just needs to be connected to anything that gets powered when the engine is on.  If it sees any voltage on that line, it will think the vehicle is running and try charging off the alternator. 

So, if you did just connect it to positive, it would always think the engine is running.

[ntsqd]

Isn't there one on the page you just linked to?

https://www.ancorpro...conductor-sizes

 

The key thing about sizing per length of conductor is that you have to assume an acceptable voltage drop.  Most tables seem to assume 3%, which is an OK ball park estimate.   But like most things, the devil is in the details - for some things 3% may be too much drop (like charging a lead acid battery), but for other things you will be fine with much more drop (a DC-DC charger, or 12v->5V USB charger).   

 

There is a tendency for folks to quote these tables like it is some sort of hard and fast rule, without considering the details of the actual application. 

There is now that I look at it rather than just pulling the URL out of my links, but as you noted it doesn't account for voltage drop or for length. My point was that if you search the whole net for wire size ampacity that what you'll mostly find are NEC charts. Which DO NOT apply to DC current. Even if they did, they are so dumbed-down so that the length of the circuit isn't a factor because the wire is capable of a LOT more amps than the NEC charts state because a one size fits all solution was needed. Can't ask or rely on electricians doing calculations in the field. Give them a hard and fast rule so they can't make mistakes and they can't get into trouble if they follow the rules. I get why it is the way that it is, but were I an electrician I'd be pissed at a system that assumes that I'm stupid.

 

I agree, acceptable voltage drop is circuit dependent. If you use Ancor's own formula and the length is short enough the resulting ampacity will exceed that chart. Which is wrong? I'll take the calculation over a chart that has no stated assumptions. I'll take the calc over a chart that does state it's assumptions.

[rando]

There is now that I look at it rather than just pulling the URL out of my links, but as you noted it doesn't account for voltage drop or for length. My point was that if you search the whole net for wire size ampacity that what you'll mostly find are NEC charts. Which DO NOT apply to DC current. Even if they did, they are so dumbed-down so that the length of the circuit isn't a factor because the wire is capable of a LOT more amps than the NEC charts state because a one size fits all solution was needed. Can't ask or rely on electricians doing calculations in the field. Give them a hard and fast rule so they can't make mistakes and they can't get into trouble if they follow the rules. I get why it is the way that it is, but were I an electrician I'd be pissed at a system that assumes that I'm stupid.

 

I agree, acceptable voltage drop is circuit dependent. If you use Ancor's own formula and the length is short enough the resulting ampacity will exceed that chart. Which is wrong? I'll take the calculation over a chart that has no stated assumptions. I'll take the calc over a chart that does state it's assumptions.

 

Neither is wrong, they are just calculating different things.   The distance dependent calculation is just calculating the voltage drop for a given current based on the resistance per length times length.   The ampacity figure is based on the ability of the wire to safely dissipate the heat generated by a current flowing through the wire.    It is independent of length as it is heat produced per length divided heat dissipation per length so the length drops out of the equation.   

 

As the acceptable voltage drop is an arbitrary number (eg a 50% voltage drop is acceptable when running a 5V USB charger from a 12V battery), so you can essentially come up with any permissible current if you are willing to accept a lot of voltage drop.  However you shouldn't exceed the wires ampacity, as the wire will get too hot and could melt the insulation - this number is based on the intrinsic properties of the wire.   

 

Sorry that was long winded - TLDR: don't exceed the ampacity, regardless of what a voltage drop calculation tells you.

[makalutoo]

I installed a red arc 40amp dc/dc charger in my fleet, then upgraded the wiring to 2 gauge from the truck to the camper. I also have a Victron monitor installed so I have a pretty good idea of what is going on with the batteries. Here are rough numbers that I was getting for battery charging.

Original configuration from the factory. 10 gauge wire from non smart alternator through 30 amp automatically resettable fuse and blue sea battery disconnect. Camper batteries were getting between 6 and 2 amps charging. 6 when truck started and closer to 2 driving. Using my fridge and heater in the Alaska summer I could not keep batteries charged on a trip, even driving for hours some days.

Installed red arc dcdc charger. Got between 20 and 30 amps charging. Again, slightly higher when truck was idling. Very happy. I also connecting a 160 solar panel into the red arc and I get around 8amps charging from full sun.

I decided to upgrade my wiring to see if I would get the full 40 amps out of the redarc. I did, it was kinda a pain routing the large diameter cable and I only get a couple amps better charging out of it.

My theory is that the voltage drop from the 10 gauge was causing the isolator to chatter(connect-discontent) and reducing the available amps to the battery with the original setup. I very well could be incorrect in my reasoning, however.

If I were to do it over again I would skip the wire size upgrade. However, if it was an available option to start with I would have gladly paid the difference for upgraded components.

I am still disappointed that the dealer set the campers up this way knowing that so many people have issues with their house batteries not charging well. Good luck

[Vic Harder]

This is excellent data! Yes, the original wiring causes “chatter”. For folks with smart alternators, dc-dc seems to be the best solution.

[Gumbus]

This is excellent data! Yes, the original wiring causes “chatter”. For folks with smart alternators, dc-dc seems to be the best solution.

Hello Vic and Makalutoo.

I am new to WTW with my recent acquisition of a 2020 Hawk (2x AGM 79AH ea) on my 19' F250. Truck is set up with dual Alternators and batteries. Realizing that anything related to diesels is more expensive, I am very interesting in preserving those components. Current upgrades are Victron BMS 712 and Victron 100/30 MPPT (blue tooth) and SunPower 170w with my own install.

 

Based on you're discussions I am inclined to step up to a dc/dc charger and so the following questions.

- Is the 10 AGW wire from the truck gen sufficient or is 4-6 AGW worth the effort?

- Is the Victron Orion 30A DC-DC "non Isolated" adequate? Vic, you mentioned your that was your choice, also why "non isolated"? Red Arc is bit too $$ for me.

- When installing, do I bypass the Blue Sea isolator and toss it?

- Is this doable for an amateur? A lot of wires in there and don't want to screw it up.

 

Thank you for your insights. Very helpful.

[Vic Harder]

Hello Vic and Makalutoo.

I am new to WTW with my recent acquisition of a 2020 Hawk (2x AGM 79AH ea) on my 19' F250. Truck is set up with dual Alternators and batteries. Realizing that anything related to diesels is more expensive, I am very interesting in preserving those components. Current upgrades are Victron BMS 712 and Victron 100/30 MPPT (blue tooth) and SunPower 170w with my own install.

 

Based on you're discussions I am inclined to step up to a dc/dc charger and so the following questions.

- Is the 10 AGW wire from the truck gen sufficient or is 4-6 AGW worth the effort?

- Is the Victron Orion 30A DC-DC "non Isolated" adequate? Vic, you mentioned your that was your choice, also why "non isolated"? Red Arc is bit too $$ for me.

- When installing, do I bypass the Blue Sea isolator and toss it?

- Is this doable for an amateur? A lot of wires in there and don't want to screw it up.

 

Thank you for your insights. Very helpful.

Very doable.  Your plan is solid.  As for your questions:

- is 10g enough?  With the Orion DC-DC.. it should be at least.  You can monitor the results and upgrade to bigger wires later if necessary.  

- non isolated is fine.  The truck and camper are not isolated already since the wiring joins the "grounds" together.

- When you put in the DC-DC, yes, the Isolator is not needed.  It CAN be used if you use a method rando showed elsewhere on this site.  If I can find time this winter, I may build that system into my truck/camper.  But for now, I took out my isolator.  The downside of the DC-DC system is that your solar panels no longer charge the truck's batteries.

 

Get your parts and then post here when you've read the manuals and still have questions.  We're keen to help out!

[Gumbus]

Very doable.  Your plan is solid.  As for your questions:

- is 10g enough?  With the Orion DC-DC.. it should be at least.  You can monitor the results and upgrade to bigger wires later if necessary.  

- non isolated is fine.  The truck and camper are not isolated already since the wiring joins the "grounds" together.

- When you put in the DC-DC, yes, the Isolator is not needed.  It CAN be used if you use a method rando showed elsewhere on this site.  If I can find time this winter, I may build that system into my truck/camper.  But for now, I took out my isolator.  The downside of the DC-DC system is that your solar panels no longer charge the truck's batteries.

 

Get your parts and then post here when you've read the manuals and still have questions.  We're keen to help out!

Ooops, forgot to mention......

 

Definitely plan to go 2x LiFePO4 later when the AGMs get old and possibly add another SunPower 170w if needed. Does this alter my requirements for the DC-DC........ is the Orion DC-DC 30A still sufficient? 

 

Thought I would ask before I spend the $$$. If you give me the "ok" I will get and check back here.

 

Big thanks again

[Charlie]

I looked through this thread, and didn't see mention. I've been intrigued by Renogy's new dual-input battery chargers, that combine  both a solar input and a smart alternator input. It includes a MPPT solar controller. It seems like a great combination. They have both 30A and 50A models. Also includes bluetooth interfaces.

 

I really like my current Victron MPPT controller, but I could really increase the highway charging with this device. Does anyone have any intel on the new Renogy devices?