2007 190P lithium upgrade

[Treker20]

Hello everyone, After much reading and checking out wiring in my 2007 190P chevy Roadtrek, I have decided to upgrade to 2 100HR Lithium batteries. Thanks to all the knowledgable people that have posted about their upgrades. I am attaching a very rough sketch of a wiring diagram i made for this installation. My new batteries will be installed in the existing battery storage compartments on the outside of the vehicle. I will be using Renogy 100AH auto heating smart batteries, along with the renogy 2000W pure sine way inverter/charger and 40A DC/DC charger. I worked in the electrical field all my life, but DC is a foreign language to me.
My number one question right now is regarding the negative wires from both DC/DC charger and inverter charger. Wiring diagrams I have seen show a separate negative cable run between the battery and the chargers. From the best I can tell right now, my triplite I/C has the negative grounded to the frame. Is there any reason I can not do this for both of the new chargers or do I need to run a cable to the battery?

My drawing shows an Isolator from the alternator /Van battery. I have read a number of you saying that you have installed a cut off between the alt/battery and the DC/DC charger so if alternator can not keep up with the load it can be disconnected. Is there any reason I can't keep the isolator in circuit and run a separate switch wire to the coil of the isolator to operate it.?

Also wiring sizing from In/Charger to batteries. several sites said I need a 3/0 cable, and some say 2/0 will work over the same distance. It is roughly 8-10 between batteries and IN/CH. Instructions say 2/0 but they don't mention distances. Dollar wise and Physical size wise i am hoping to stay with 2/0.

For now that is all the questions I have but I am sure there will be many more as i go along.

[CanuckRV]

I am just working on a very similar install. Your inverter will be drawing 166 amps you need to use at least 1awg to the inverter and it should be protected by an appropriate fuse.
I ran 2awg for everything else as my chargers are separate, but you could get away with 6awg for the dc/dc charger I personally would run wire for the ground that's a lot of amps to run through the frame.

[avanti]

IMO, you should ALWAYS use a chassis return for any DC circuit that runs for any significant distance. The ampicity of a proper chassis connection is far greater than any practical wire size.

The web is full of advice to the contrary, but I believe that it is all wrong. There is a reason why this has been best practice in all professionally-designed vehicles for the past 100 years. It is safer, cheaper, better-performing, lighter and easier than running dedicated return wires.

You may fairly ask why so many of the installation instructions of so many devices say otherwise. As far as I can tell, these instructions are aimed toward DIY installers who (in the opinion of these manufacturers) can't be trusted to locate or fabricate proper ground points. One can see their point, since it is common to see random pieces of sheet metal or any-old-bolt used as ground points, and there is nothing more difficult to diagnose than a problem caused by an inadequate ground. They see it as to their advantage to insist on an easy-to-specify wire, no matter how inferior, since doing so costs them nothing and may save them some grief in customer support.

The bottom line is that if you can't be trusted to design and execute a proper chassis ground, then go ahead and run the wires. But, if you CAN be so trusted, a chassis ground is superior in every way.

[hbn7hj]

Originally Posted by CanuckRV

I am just working on a very similar install. Your inverter will be drawing 166 amps you need to use at least 1awg to the inverter and it should be protected by an appropriate fuse.
I ran 2awg for everything else as my chargers are separate, but you could get away with 6awg for the dc/dc charger I personally would run wire for the ground that's a lot of amps to run through the frame.

I have 400AH in lithium with a 1500 watt inverter. The largest wire is to the inverter and it is four gauge. No A/C by battery. Works fine. Three AC battery chargers paralleled have 6 gauge each.

[CanuckRV]

Please do it right a fire in a RV is not something you want.
Use Ohm's law to find your amps and watts
https://ohmslawcalculator.com/ohms-law-calculator
Here is an interactive chart to find out wire and fuse sizing Circuit Wizard - Blue Sea Systems

remember while 12v is a low voltage its amps that kill you and we are using very high amperage its better to error on the side of caution.

[booster]

Originally Posted by CanuckRV

Please do it right a fire in a RV is not something you want.
Use Ohm's law to find your amps and watts
https://ohmslawcalculator.com/ohms-law-calculator
Here is an interactive chart to find out wire and fuse sizing Circuit Wizard - Blue Sea Systems

remember while 12v is a low voltage its amps that kill you and we are using very high amperage its better to error on the side of caution.

You are very unlikely to ever be hurt be 12v DC in an electrocution, IMO as your internal resistance to flow is too high. In the industrial world I worked in for many years, the latest rules mostly started at 50 volts, and most of that was because of arc flash explosions on wiring at 50 volts. 110 volts can hurt you for sure, and many consider 220 volts to be among the most dangerous.


That said, 12v DC can certainly kill you if it starts a fire, and high current levels needed to get adequate power can generate lots of heat, and high heat can cause fires quite easily. You can also get burned on a hot connection. It is always a good idea to test the connections in a system with an infrared thermometer to look for hot connections, fuses, breakers, wiring, and such. I found a couple on my 440ah setup after I built it about 5 years ago simply because I had a stainless washer on the wrong side of a 300 amp fuse connections (a common error on that type of fuse I found out later as it looks like that is how it should be). The system was charging at nearly 250 amps at the time I did the check.

[avanti]

The various dangers of electricity is a complex topic, and there are a lot of misconceptions floating around. The "current kills" thing that everybody repeats really is misleading for the reason @booster states. You need BOTH a current and a voltage to be dangerous (but, of course, you can't have one without the other). Unless both are over some threshold, there's no danger. 12V isn't enough to make it into your body, so it can't kill you in the normal ways. Similarly, the zillions of volts you get from a doorknob can't kill you either, for lack of amps. But, with enough voltage, even milliamps can kill you, especially if it runs through your heart.

When it comes to vehicles, probably the greatest danger is having your finger burned off by a ring that shorts a high-current source. Please take off all jewelry and disconnect the ground before starting.

[Treker20]

Originally Posted by avanti

IMO, you should ALWAYS use a chassis return for any DC circuit that runs for any significant distance. The ampicity of a proper chassis connection is far greater than any practical wire size.

The web is full of advice to the contrary, but I believe that it is all wrong. There is a reason why this has been best practice in all professionally-designed vehicles for the past 100 years. It is safer, cheaper, better-performing, lighter and easier than running dedicated return wires.

You may fairly ask why so many of the installation instructions of so many devices say otherwise. As far as I can tell, these instructions are aimed toward DIY installers who (in the opinion of these manufacturers) can't be trusted to locate or fabricate proper ground points. One can see their point, since it is common to see random pieces of sheet metal or any-old-bolt used as ground points, and there is nothing more difficult to diagnose than a problem caused by an inadequate ground. They see it as to their advantage to insist on an easy-to-specify wire, no matter how inferior, since doing so costs them nothing and may save them some grief in customer support.

The bottom line is that if you can't be trusted to design and execute a proper chassis ground, then go ahead and run the wires. But, if you CAN be so trusted, a chassis ground is superior in every way.

Thanks Avanti, That makes sense about the Grounding. I really don't want to have to run a separate return, But I can't say I could be trusted to design and execute a proper chassis ground. If I was to use the chassis for the ground, I would fasten the ground wire to the location that the current wire was fastened to, make sure the area is clean and rust free and that connection was tight. I am thinking i should only have 2 points of connection, one where batteries are grounded and one where current IN/CH is grounded. To me that should do it. Thoughts?

[Treker20]

Originally Posted by CanuckRV

I am just working on a very similar install. Your inverter will be drawing 166 amps you need to use at least 1awg to the inverter and it should be protected by an appropriate fuse.
I ran 2awg for everything else as my chargers are separate, but you could get away with 6awg for the dc/dc charger I personally would run wire for the ground that's a lot of amps to run through the frame.

Canuck, IMO the 1 awg is too small. The 90 degree current rating is 145A, but could be even lower than that depending on the temp ratings of the connection points. 2/0 is rated at 195A at 90C and would have to be fused to at least 200 based on the 166A draw. My concern is with voltage drop. I am sill trying to get my head around the different charging voltages, but potentially a 3% drop would drop 12V to 11.64.Running 2/0 is going to be a PIA, but 3/0 or more would be even more difficult. since my batteries are 8-10 away from the charger Voltage drop is a concern. Ideally I would move my batteries closer, and I think i would be possible to do that, but then they would be right next to gas tank spout , which would make me very nervous.

[avanti]

Originally Posted by Treker20

My concern is with voltage drop. I am sill trying to get my head around the different charging voltages, but potentially a 3% drop would drop 12V to 11.64.

That raises an interesting question:
Do any of these B2Bs provide voltage-sense inputs the way the Balmer does? IMO this is a very important feature anywhere where voltage is critical. Line drop is inevitable, and changes over time.

[booster]

Originally Posted by Treker20

Canuck, IMO the 1 awg is too small. The 90 degree current rating is 145A, but could be even lower than that depending on the temp ratings of the connection points. 2/0 is rated at 195A at 90C and would have to be fused to at least 200 based on the 166A draw. My concern is with voltage drop. I am sill trying to get my head around the different charging voltages, but potentially a 3% drop would drop 12V to 11.64.Running 2/0 is going to be a PIA, but 3/0 or more would be even more difficult. since my batteries are 8-10 away from the charger Voltage drop is a concern. Ideally I would move my batteries closer, and I think i would be possible to do that, but then they would be right next to gas tank spout , which would make me very nervous.

One thing to remember is that the voltage drop is not a constant. Any given drop is specific at any given voltage and current, so if you are using a constant voltage source for charging, like an alternator, as current drops near the end of charging the voltage drop will drop with it so you get to a full chargea at full voltage setpoint. You certainly need to keep resistance low enough to not overheat the wiring though, so size the wiring gauge to that parameter by using the Blue Sea Circuit Wizard on their website and be sure to enter any reducing factors like in conduit, sleeving, etc. Also put the time at 30 minutes or more so it shows continuous charging results.

[hbn7hj]

Originally Posted by CanuckRV

Please do it right a fire in a RV is not something you want.
Use Ohm's law to find your amps and watts
https://ohmslawcalculator.com/ohms-law-calculator
Here is an interactive chart to find out wire and fuse sizing Circuit Wizard - Blue Sea Systems

remember while 12v is a low voltage its amps that kill you and we are using very high amperage its better to error on the side of caution.

Calculated out to 4 gauge. Max amps is 100 to the microwave and run is 2ft.

Charging is three X 6 gauge at 100 amps.

[Treker20]

Originally Posted by booster

One thing to remember is that the voltage drop is not a constant. Any given drop is specific at any given voltage and current, so if you are using a constant voltage source for charging, like an alternator, as current drops near the end of charging the voltage drop will drop with it so you get to a full chargea at full voltage setpoint. You certainly need to keep resistance low enough to not overheat the wiring though, so size the wiring gauge to that parameter by using the Blue Sea Circuit Wizard on their website and be sure to enter any reducing factors like in conduit, sleeving, etc. Also put the time at 30 minutes or more so it shows continuous charging results.

Booster, thanks for the info, Interesting results. depending on criteria, wire size changes from #2-3/0. I have been using ampacity of 166A based on the draw of 2000W at 12V to figure wire size and VD. The criteria that changes the wire size are duration and sheathing. Both of Those make sense. I assume that even there plastic sheathing with the spilt would affect the wire sizing. Since the only major current draw would be the microwave, and that would only run for maybe a max of 10 minutes, i don't see why I would need to figure 30 minutes. You mentioned it was because of charge time, but the 2000W IN/CH max charge amps are 65, and DC/DC charger is 40 A. I don't see why that would be a factor. When I use 65 A for 60 minute duration, wire size drops to 4.

Instructions for IN/Ch say to use 2/0 and keep as close to batteries as possible.

[Treker20]

Originally Posted by hbn7hj

Calculated out to 4 gauge. Max amps is 100 to the microwave and run is 2ft.

Charging is three X 6 gauge at 100 amps.

HBN, good point, but i was sizing based on total potential draw of inverter.

[Treker20]

Originally Posted by avanti

That raises an interesting question:
Do any of these B2Bs provide voltage-sense inputs the way the Balmer does? IMO this is a very important feature anywhere where voltage is critical. Line drop is inevitable, and changes over time.

Avanti, could you explain this a little more?

[avanti]

Originally Posted by Treker20

Avanti, could you explain this a little more?

Sure:
Some chargers (such as the Balmar regulator/charger) have a "voltage sense" input. This is a high-impedance input that reads the battery voltage while drawing almost no current. Since there is little current, there is little voltage drop, even with a very small wire. The idea is that by running such a wire from the battery to the charger, you give the charger the actual voltage at the battery, rather than the pre-voltage-drop voltage that it is actually putting out. It can thus raise the voltage to compensate for the voltage drop of the high-current (and possibly long) charging wire.

This is a very good feature, and I see no reason why a B2B couldn't have it. I was just wondering whether any of them do.

[Treker20]

Originally Posted by avanti

Sure:
Some chargers (such as the Balmar regulator/charger) have a "voltage sense" input. This is a high-impedance input that reads the battery voltage while drawing almost no current. Since there is little current, there is little voltage drop, even with a very small wire. The idea is that by running such a wire from the battery to the charger, you give the charger the actual voltage at the battery, rather than the pre-voltage-drop voltage that it is actually putting out. It can thus raise the voltage to compensate for the voltage drop of the high-current (and possibly long) charging wire.

This is a very good feature, and I see no reason why a B2B couldn't have it. I was just wondering whether any of them do.

Thanks Avanti, very interesting. is it the duo charge regulator that you are talking about in place of a dc/dc Charger.?

[Treker20]

Originally Posted by CanuckRV

Please do it right a fire in a RV is not something you want.
Use Ohm's law to find your amps and watts
https://ohmslawcalculator.com/ohms-law-calculator
Here is an interactive chart to find out wire and fuse sizing Circuit Wizard - Blue Sea Systems

remember while 12v is a low voltage its amps that kill you and we are using very high amperage its better to error on the side of caution.

Thanks for the info Canuck, using the blue sea chart i see how you came up with the wiring sizing. I am still confused as to how they come up with 1awg, when amps rating is below the potential draw. how close together are your batteries and chargers?

I just looked looked up ABYC and I understand the current ratings. They are basing on 1 conductor in Free air, where as NEC figures up to 3 conductors in raceways, cable or direct burial. when sleeving is added to blues sea chart, ampacity drops.

[avanti]

Originally Posted by Treker20

Thanks Avanti, very interesting. is it the duo charge regulator that you are talking about in place of a dc/dc Charger.?

Not certain what you are asking.

My current rig has a Balmar MC614, as do many second-alternator setups. It has a voltage-sense input.

For my next rig, I am seriously considering an "engine inverter" that will change the 12VDC to 120VAC used to drive the coach charger. This largely takes the voltage drop issue off the table, since the long run would be at 120VAC.

I didn't have a specific B2B in mind for my question. Just wondering generically.

[booster]

Originally Posted by Treker20

Booster, thanks for the info, Interesting results. depending on criteria, wire size changes from #2-3/0. I have been using ampacity of 166A based on the draw of 2000W at 12V to figure wire size and VD. The criteria that changes the wire size are duration and sheathing. Both of Those make sense. I assume that even there plastic sheathing with the spilt would affect the wire sizing. Since the only major current draw would be the microwave, and that would only run for maybe a max of 10 minutes, i don't see why I would need to figure 30 minutes. You mentioned it was because of charge time, but the 2000W IN/CH max charge amps are 65, and DC/DC charger is 40 A. I don't see why that would be a factor. When I use 65 A for 60 minute duration, wire size drops to 4.

Instructions for IN/Ch say to use 2/0 and keep as close to batteries as possible.

If you intend to use the B to B in that size forever and not ever and batteries and charge rate, yes, you can use that 65 amps. Anything you use in the van at the same time as charging would come off of the 40 amps of charging of course unless you separated load and charge which I don't think you intend to do. Are you looking to use your original engine to coach wiring from the front of the van to rear? If so, and the van came with a Tripplite, it would be a single #4 cable and have and 80 amp breakers (really a twin 40 on each end). If you remove the separator in the front be sure not to bypass the breaker on the coach charging cable.


On the 10 minutes of run on the microwave, you could use the shorter time, but also remember you may have other loads on a the same time so your consumption will probably be higher than the micro load to some extent, and you may also want to run something that would run longer or in combination with the micro. The cable from the batteries to the inverter is a probably a #2 battery cable if it wired like out 07 190 was. Going bigger on that cable would not be too bad if you get the extra flexible, fine strand cable, which is much easier to run in those circumstances as coming up through the floor. You would need to fuse that line at the battery at whatever the max current continuously would be for the cable as shorts don't happen all at once sometimes and could go a longer time.



The instructions say 2/0 for the inverter wiring because that would be what the max input of the inverter would be at full load run continuously and really isn't a bad idea to run a cable that is capable of that much input as the output AC wiring can accept 30 amps of 110v power which way more than the capacity of the 2000 what inverter at 3600 watts.