DC to DC converter necessary when switching to lithium batteries?

[jkordzi]

I'm in the process of planning the upgrade of my 5.0TA to lithium batteries. I tow with a 2017 GMC Canyon. So far I think I'm going to have to upgrade the WFCO converter and the Go Power solar converter. I'd like to better understand the concern about potentially frying my truck's alternator due to overheating it when it charges the lithium batteries. I've seen the Victron video and read posts from folks who have installed DC to DC chargers to limit how much current come from the alternator. But if my truck has a fuse on the line in the connector that provides power to the trailer, wouldn't that provide adequate protection to the alternator? Yes, I don't want the fuse to blow, but could that be used as a test of whether a DC to DC charger is necessary? Thanks and more questions about this project to follow.

[Vermilye]

Originally Posted by jkordzi

I'm in the process of planning the upgrade of my 5.0TA to lithium batteries. I tow with a 2017 GMC Canyon. So far I think I'm going to have to upgrade the WFCO converter and the Go Power solar converter. I'd like to better understand the concern about potentially frying my truck's alternator due to overheating it when it charges the lithium batteries. I've seen the Victron video and read posts from folks who have installed DC to DC chargers to limit how much current come from the alternator. But if my truck has a fuse on the line in the connector that provides power to the trailer, wouldn't that provide adequate protection to the alternator? Yes, I don't want the fuse to blow, but could that be used as a test of whether a DC to DC charger is necessary? Thanks and more questions about this project to follow.

It is very unlikely that you will "fry" your alternator in a tow vehicle; the problem is more likely in a motorhome where the run between the alternator is short.

That said, a couple of advantages the DC to DC converter provides:

1. Allows you to set the charging voltage - many tow vehicles produce voltages at the trailer battery too low to fully charge lithium batteries. You can set the DC to DC converter output to 14.4V - 14.6V to fully charge and balance lithium batteries. Some versions of DC to DC converters are 3 stage chargers, allowing you to set absorption & float voltages, as well as providing bluetooth data to your phone.

2. While not a major problem, if the trailer batteries are at a higher voltage than the tow vehicle, without a DC to DC converter or added diode the trailer batteries will discharge into the tow vehicle. You may find you actually lose battery charge while connected to the tow vehicle. A DC to DC converter (or diode) isolates the trailer from the tow vehicle, something that may be an advantage as the tow vehicle electrical systems become more complex.

[jkordzi]

Thanks. I should have mentioned that I believe most newer GMC trucks (mine included) have a tow/haul mode switch that bumps up the voltage supplied (here's a nice post: https://www.escapeforum.org/forums/f...cles-5244.html). So I think the voltage at least is probably in the right spot.



So where/how do you install the DC to DC converter and do you have a favored source?

Originally Posted by Vermilye

It is very unlikely that you will "fry" your alternator in a tow vehicle; the problem is more likely in a motorhome where the run between the alternator is short.

That said, a couple of advantages the DC to DC converter provides:

1. Allows you to set the charging voltage - many tow vehicles produce voltages at the trailer battery too low to fully charge lithium batteries. You can set the DC to DC converter output to 14.4V - 14.6V to fully charge and balance lithium batteries. Some versions of DC to DC converters are 3 stage chargers, allowing you to set absorption & float voltages, as well as providing bluetooth data to your phone.

2. While not a major problem, if the trailer batteries are at a higher voltage than the tow vehicle, without a DC to DC converter or added diode the trailer batteries will discharge into the tow vehicle. You may find you actually lose battery charge while connected to the tow vehicle. A DC to DC converter (or diode) isolates the trailer from the tow vehicle, something that may be an advantage as the tow vehicle electrical systems become more complex.

[Vermilye]

I have a Victron Energy Orion-Tr Smart 12/12-Volt 18 amp 220-Watt DC-DC Charger, Isolated (Bluetooth) mounted under the driver's side rear seat (in a a 2017 21C). I added a fused #6 hot from the batteries to the tongue jack & break away switch since the DC to DC converter is one way & they are normally fed from the charge line.

[splitting_lanes]

I have a canyon and a 5.0, with the Victron DC/DC converter. I haven’t installed lithium batteries yet, but I bought it lithium ready.

The DC/DC converter (as escape installs it) is installed in the front of the trailer where the jack switches are. I’d look in your drivers side hatch and see if you have access to the main 7 pin power wire coming in. If you find a 10 gauge red wire accessible, that would make the installation easier than the alternative, putting it next to the batteries.

Putting the DC/DC converter by the battery means running a wire up to power the jacks. I’d avoid that much work for the relatively low charging amps you’ll gain doing it.

[richm]

I use a Victron 12/12-18 Orion-Tr to charge a lithium battery in the rear of my 5.0TA, taking power from the 7-pin cable that connects to my tow vehicle.

Here's something to consider. The voltage drop between the tow vehicle battery and the lithium battery in the rear of my trailer are significant. I typically see 10V going into the Victron when it is supplying 15A to the lithium battery. The reason I mention this is, it would not be possible to charge the trailer battery from the 7-pin without the Victron.

Regarding location of the Victron, note that the Victron measures the battery state of charge by measuring voltage at the output of the Victron. For instance, the charger shuts off when the output voltage reaches the float voltage setting. This will work far better if the wiring between the Victron and lithium battery are a larger gauge and are shorter. If instead, there is a significant resistance, the Victron may do weird stuff, like cycling on and off repeatedly while nearing full charge, as the output voltage at the Victron rises with the charge current, then drops when the charge current shuts off.

[TTMartin]

Originally Posted by jkordzi

Yes, I don't want the fuse to blow, but could that be used as a test of whether a DC to DC charger is necessary?

Yes, the fuse will eventually blow.

It might not blow when you 'test' it, less you discharge the lithium battery first. So, you could test it, think you are 'okay' and when your lithium battery is discharged and actually needs charging by the alternator the fuse will blow. Murphy's Law will ensure that happens at the worst possible time.

Just do it the right way and add a DC to DC charger.

[Vermilye]

Originally Posted by TTMartin

Yes, the fuse will eventually blow.

It might not blow when you 'test' it, less you discharge the lithium battery first. So, you could test it, think you are 'okay' and when your lithium battery is discharged and actually needs charging by the alternator the fuse will blow. Murphy's Law will ensure that happens at the worst possible time.

Just do it the right way and add a DC to DC charger.

Whether a DC to DC converter will reduce the tow vehicle current on the charge line depends. In some cases, it will cause the tow vehicle to produce more current than the trailer side.

A DC to DC converter will limit the output current to the converter's rated value, ie in the case of the Victron 12/12-18 to around 18 amps. It will not limit the current draw on the vehicle side. If the tow vehicle voltage is low, it will draw more current in order to meet the voltage / current output requirements.

[TTMartin]

Originally Posted by Vermilye

Whether a DC to DC converter will reduce the tow vehicle current on the charge line depends. In some cases, it will cause the tow vehicle to produce more current than the trailer side.

A DC to DC converter will limit the output current to the converter's rated value, ie in the case of the Victron 12/12-18 to around 18 amps. It will not limit the current draw on the vehicle side. If the tow vehicle voltage is low, it will draw more current in order to meet the voltage / current output requirements.

Then the Victron 12/24-10 is probably a better choice.

[Vermilye]

Originally Posted by TTMartin

Then the Victron 12/24-10 is probably a better choice.

No, that is a 24V output DC to DC converter. Output range is 20V - 30V, too high for a 12V lithium system.

If you are concerned about drawing too much from the truck charge system, the Victron Orion 12/12-9 will limit the current, however is is not a "multi stage Charger" - while you can adjust the output between 10V - 15V, it does not have adjustable stages, and no bluetooth.

[brroberts]

My solar controller and battery monitor are Victron, but my dc-dc charger is a 20 amp Renogy which can be limited to 10 amps if selected.

[jkordzi]

So I can compare it to the Victron, can you point me to it? Thanks.

Originally Posted by brroberts

My solar controller and battery monitor are Victron, but my dc-dc charger is a 20 amp Renogy which can be limited to 10 amps if selected.

[brroberts]

Here’s the Google link:

https://renogy.com/12v-20a-dc-to-dc-...ttery-charger/

[jkordzi]

Thanks. Looks like it may be a slightly better performer and better value than the Victron.

Originally Posted by brroberts

Here’s the Google link:

https://renogy.com/12v-20a-dc-to-dc-...ttery-charger/

[edlynnrich]

My VictronConnect app cannot find my 12/12-18 converter. Any suggestions? Let me know if you need more info.

Ed

[Vermilye]

Originally Posted by edlynnrich

My VictronConnect app cannot find my 12/12-18 converter. Any suggestions? Let me know if you need more info.

Ed

Make sure it is powered by the tow vehicle or other 12V source. The device remains off until it sees input voltage.

[jkordzi]

To those of you who have installed the DC to DC converter, have you run a new larger line from your tow vehicle to it, or do you just depend on the power from the 7 pin connector? If just the latter, do you think that even after the DC to DC converter bumps up the voltage that you get enough current to significantly charge the trailer's lithium batteries? Thanks.

[TTMartin]

Originally Posted by jkordzi

To those of you who have installed the DC to DC converter, have you run a new larger line from your tow vehicle to it, or do you just depend on the power from the 7 pin connector? If just the latter, do you think that even after the DC to DC converter bumps up the voltage that you get enough current to significantly charge the trailer's lithium batteries? Thanks.

I just use the power from the 7 pin connector, no special vehicle wiring. Like brroberts I am using the Renogy 12V 20A DC to DC On-Board Battery Charger set to 10 amps.

If you run your refrigerator on propane when you travel your solar panel is probably enough to power the trailer without power coming from the 7 pin connector's power pin.

[brroberts]

I have run 6ga to the back using a trolling motor plug. The truck has smart charging and a direct line delivers more current in my situation. I do run the fridge on 12v when driving.

[alanerickson]

The victron is 18 amps output, so when you do the power, voltage, current calculations for the input it comes out to roughly 22 amps on the input. After searching the web a bit I found the documents and for my Ram while fused at 30A, for continuous they say only 70% of that or 21 amps (continuous). It doesn't sound like a lot of people have trouble with the Victron and "factory" auto wiring, but it's a little too close for me, and I'm going to replace it with the Renogy.