22 replies to this topic

[Bwht4x4]

I'm replacing my original FWC-supplied Exide dual 12 volt group 24 AGM batteries that came with our camper in 2013 with two Lifeline 6 volt AGM batteries (220 ah).  Is there a need to upgrade the original wiring in the battery compartment to a larger gauge?  I believe it is currently 6 gauge, which from what I can tell from my research is more than adequate.  It doesn't seem like up-sizing the wire is needed based on the max amp draw we could place on the system.  If I turned everything on I have in my camper I don't think I could get more than a 15 amp draw.  I don't have or use an inverter ever.

 

Thoughts?

 

 

[Stokeme]

With my basic understanding, I would say no, leave it alone. My guess would be the wire is 8, though, not 6. Also, just doing the box would have minimal effect. Re-doing the entire line from roof to box, with heavier gauge, would offer the greater benefit. Nightmare scenario.
It looks like your parallel cables are heavier? Just to throw this out there, I used these 4 gauge pre-made cables to interconnect my batteries. If you have 6, that should be plenty good, as that interconnect run is very short.
https://www.amazon.c...e?ie=UTF8&psc=1

My 2 cents, plenty of guys on this Forum have better knowledge ... looks nice!

[Bwht4x4]

Thanks for the info Stokeme.  The pict I provided is the old 12 volt setup.  Like you mentioned, I was thinking of upsizing the battery interconnect cable to a 10 inch to 12 inch section of 4 or 2 gauge, but I'm not sure if it's even needed.  I'm going to go out right now and see if I can determine what gauge the existing wires are.  

[Stokeme]

Sorry, did not notice you were going to 6V. So, I assume you will be running them in series to obtain 12 V. Everything else mentioned remains the same. FWC may use 10 gauge, vaguely recall not even 8 ... would still recommend to leave as is ... use heaviest gauge possible that works with your controller/battery connect & one gauge heavier with your battery connect.

Edited by Stokeme, 28 June 2020 - 06:04 PM.

[Bwht4x4]

Just went and took a look at what the wire gauge is.  It looks like nearly all of it is 8 gauge, except for the black wire that goes from the battery in the upper part of the photo to the shunt in the lower right of the photo is 6 gauge.  I think I'm going to get the new batteries set in place and then have a custom battery interconnect cable made out of something much thicker.  My buddy has an AM Solar kit with the same batteries and they used 4/0 cable for the battery interconnect cable, which is huge!!!

[Vic Harder]

I can't see your picture for some reason.... that said, in principle,  just a battery arrangement change won't necessitate a thicker wire gauge.  

 

Since you do need at least one new wire to hook them up in series, I'd beef up that one wire to as thick as you like... Anything over 4 g would be overkill, never mind 4/0  wow.  

 

FWIW, I'm using 2g in my setup (in the battery box and between the 3000w inverter and the batteries), with 4g from truck to camper.  Important to note that my batteries are in parallel, not series!

 

Edited by Vic Harder, 28 June 2020 - 08:24 PM.

[Jack]

Unless you are going to attach an inverter (12 VDC to 120 VAC), 6 gauge or even 8 gauge is fine - but see note below on charging.

 

The two main criteria for picking wire gauge are current capacity and voltage drop.

 

The maximum current through the FWC fuse block is 30 A, so 10 gauge is fine. If you are running an inverter directly off of the batteries, you need a wire gauge to handle the current draw by the inverter. A 700 W inverter can draw up to about 55 A, so you would need 6 gauge wire - and this would be true for the cable between the two 6 V batteries. All copper wires have some resistance and so they act a very tiny bit like a heating element. As long as you don't run more current that the wire is rated, you can't feel the heat, A thicker wire (lower gauge number), say 8 gauge to 6 gauge, for a 10 ft length, will save you less than 1 W.

 

Voltage drop is important for battery charging and battery isolation. Because of the wire resistance, the voltage at the end of the wire is less than the voltage at the source. A thicker wire has less resistance so the voltage drop is less. This is why solar charge controllers should be close to the battery (shorter distance, less resistance) and/or use thicker wire (less resistance) so the charge voltage is what the battery needs. The exception is for solar charge controllers that can sense the voltage at the battery (Victron) - they source a higher voltage such that the voltage at the battery is what is needed.

 

The battery separator is the other voltage sensitive device in the FWC. The Sure Power 1314A needs to see 13.5 V to believe that the truck alternator is producing power and therefore connect it to the FWC battery. FWC fuses that line to 30 A. If you have 20 feet of wire (10 ft each way) at 30 A, that's a 0.6 V voltage drop. The alternator has to source 14.1 V for the 1314 A to see 13.5 V connect the the alternator to the FWC battery over the FWC 10 gauge wire. 8 gauge wire would have a voltage drop of about 0.35 V

[Jack]

Unless you are going to attach an inverter (12 VDC to 120 VAC), 6 gauge or even 8 gauge is fine - but see note below on charging.

 

The two main criteria for picking wire gauge are current capacity and voltage drop.

 

The maximum current through the FWC fuse block is 30 A, so 10 gauge is fine. If you are running an inverter directly off of the batteries, you need a wire gauge to handle the current draw by the inverter. A 700 W inverter can draw up to about 55 A, so you would need 6 gauge wire - and this would be true for the cable between the two 6 V batteries. All copper wires have some resistance and so they act a very tiny bit like a heating element. As long as you don't run more current that the wire is rated, you can't feel the heat, A thicker wire (lower gauge number), say 8 gauge to 6 gauge, for a 10 ft length, will save you less than 1 W.

 

Voltage drop is important for battery charging and battery isolation. Because of the wire resistance, the voltage at the end of the wire is less than the voltage at the source. A thicker wire has less resistance so the voltage drop is less. This is why solar charge controllers should be close to the battery (shorter distance, less resistance) and/or use thicker wire (less resistance) so the charge voltage is what the battery needs. The exception is for solar charge controllers that can sense the voltage at the battery (Victron) - they source a higher voltage such that the voltage at the battery is what is needed.

 

The battery separator is the other voltage sensitive device in the FWC. The Sure Power 1314A needs to see 13.5 V to believe that the truck alternator is producing power and therefore connect it to the FWC battery. FWC fuses that line to 30 A. If you have 20 feet of wire (10 ft each way) at 30 A, that's a 0.6 V voltage drop. The alternator has to source 14.1 V for the 1314 A to see 13.5 V connect the the alternator to the FWC battery over the FWC 10 gauge wire. 8 gauge wire would have a voltage drop of about 0.35 V

[Vic Harder]

As Jack points out above, the Sure Power 1314A senses battery voltage.  Let's say it does sense 14v at the truck alternator... it says "Yeah, I can connect the alternator to the camper battery".  And it does so.  You hear a "CLICK".

 

Current starts to flow over the 10g wire between the alternator and the camper battery.  A lot of current, say 30A.  That heats the wire up, and power (voltage) is lost trying to move that much juice over the small wire.  Such that, as Jack says... there is a .6V drop.  14v 0.6v = 13.4 volts.  NOT enough for the 1314A to believe that the alternator is putting out enough voltage to connect the two systems (even though the voltage has NOT changed at the alternator!).  You hear another "CLICK"

 

This repeats as you are driving your truck, blissfully unaware that charging is not happening, except for those short periods between clicks.

 

Thicker wire can help, as it could keep the voltage from dropping too much.  But that again assumes an alternator that puts out 14v or so.  Newer smart alternators won't do that as they are optimized for 12v to keep all the infotainment systems happy, and to improve fuel economy.

 

So you can see why the stock system with the 1314s is not going to work.

 

A better separator is with thick wires is good and works if you need bi-directional charging.  A DC-DC charger is likely better for most folks with newer trucks.

[Bwht4x4]

After talking with Lifeline and Iota today I'm having concerns the stock Iota DLS-30 will do a good job of charging my new 6 volt AGMs.  The charge profile of the Iota converter/charger is higher at both bulk and float according to the recommendations by Lifeline.  Even with any of the various IQ Smart Charging Modules the float of 13.6 volts is higher than what Lifeline recommends.  Iota did explain to me how to adjust the voltage of the DLS-30, but I'm not sure I want to open the case and attempt it.

 

The DLS-30 worked great on my stock 7 year old group 24 AGM batteries, so I may just leave it as is and install the new batteries.