Choosing a DC-DC charger - truck camper with LiFePO4

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theodk asked Mar 25, '20

Choosing a DC-DC charger - truck camper with LiFePO4

I'm looking into buying a DC-DC charger for my truck camper, but I'm unsure which one. Here are the details of my setup:

- Truck: 6.5L diesel engine with 100A alternator, 2 AGM starter batteries (12V parallel)

- Camper: 200Ah LiFePO4 batteries, 8AWG wiring on the DC input

- Alternator outputs around 13.5V, LiFePO4 batteries need around 14.5V (i.e. stepping up the voltage is a must)

Based on those details, it seems like the Orion-Tr Smart 12/12-30 would fit the bill, but I'm concerned about the following:

1. Does the Orion-Tr Smart require a remote connection to operate, or can it switch on and off based on input voltage reading alone? I'm going to install the charger on the camper, so I won't have access to the ignition switch, so the only way to determine if the motor is running is by measuring the input voltage - can the Orion-Tr Smart do that?

2. Is 30A reasonable for 8AWG wiring with a 100A alternator? It seems to me like it would be OK, but the charger will be far from the alternator (probably around 5-10m of wire).

3. Is the Orion-Tr Smart the most cost-effective solution for my use case? Another option is the Orion-Tr (without the smart part), but I'm not sure if it can handle LiFePO4 charging.

Thanks in advance to anyone who can help me with this!

orion-tr smart Orion DC-DC Converters not smart alternator

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Justin Cook answered · Mar 26, 2020 at 12:23 AM

Hi @theodk, I can answer those questions pretty succinctly:

1: Yes, the Orion-Tr Smart can function perfectly well in fully-automatic mode (just leave the factory jumper installed in the provided remote bridge and, after you've finished programming it, install the remote bridge). The turn on/shutdown voltages are fully configurable for automatic operation.

2. No, you will need heavier-gauge running from the start battery (important to note that the DC-in comes from the start battery, not the alternator), particularly at that long of a run. The Orion-Tr Smart delivers 30A of charge to the house/aux battery, but that means it will pull somewhere between (depending on a lot of factors) around 38-45A from the start battery, and the cabling needs to be sized accordingly. The Orion's terminals will accept a maximum 6AWG wire into them, but for your length of run (calculating for the higher number, 10m length so 20m round-trip) you should run 1AWG or 1/0 from your start battery to something like a couple of Blue Sea PowerPosts near the Orion, then use those to step down your wire gauge to 6AWG.

3. The Orion-Tr Smart is definitely the most cost-effective trustworthy solution available. I specify trustworthy because there are certainly no shortage of Amazon-special off-brand DC-DC chargers that are far cheaper... but you get what you pay for. The Orion is robust, effective, efficient, and cheaper than a Sterling BB1230 (with more power delivery and a better warranty too), so as long as you connect it properly, taking care to use appropriate gauge wire, good connections, and appropriate fusing, the Orion-Tr Smart is a fantastic solution for your use-case.

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theodk commented · Mar 26, 2020 at 12:46 AM

Thank you very much, @Justin Cook - Bay Marine Supply USA, this is super helpful. This completely solves questions 1 and 3. Regarding question 2 (wire gauge vs distance), I think I may have to take the performance drop and go with the 12-12/18 instead. The camper and the truck are both wired in 8AWG and it would be a hassle+expensive to rewire. I could install the charger near the starter and output at a higher voltage to make up for the distance, but then I'd have the charger next to a very large diesel engine; I can see overheating being a big issue at that point.

If you have any thoughts on this, I'd love to hear them, but let me reiterate that you've been incredibly helpful already! Thanks!

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Justin Cook ♦♦ theodk commented · Mar 26, 2020 at 12:52 AM

@theodk well... it's important to narrow down that run length as best you can... there's a really big difference between a 5 meter run (which is 10 meter round-trip) and a 10m run (which is 20m round-trip).

Urgh, but I just ran the calcs and even at 5m, 10m round-trip, that 8 is no good. Any chance there's an unused second 8AWG wire that you could use in addition? Two 8s make a 4 (ish), and at 5m one-way, that would be acceptable....

I concur about not putting it in the engine bay, though, that's not a good idea. As close as reasonably possible, certainly, but keep the charger in the habitation area preferably.

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theodk Justin Cook ♦♦ commented · Mar 27, 2020 at 01:03 AM

Hi @Justin Cook - Bay Marine Supply USA, I just ran some back of the envelope calcs, and I think I have a passable solution. Since I have a truck camper, there is a plug that connects the camper to the truck. This plug is factory installed, and I gather it's not much better than the 8AWG wire. Therefore, I think I should install the charger on the truck side, i.e. before the plug, and let the plug handle 30A max. Thus, my plan is as follows:

- 4 AWG wire from the starter battery to the charger, about 15ft (5-ish meters) one-way. This wire will handle up to 45A and reasonably hot temps inside the engine bay. I have some 4AWG that I think I can repurpose, or I'll just buy new wire off Amazon or something.

- There will be a very short 8AWG run just before the charger to ensure that it can fit into the charger. I'll just use a battery-type connection (I'll ring connectors on both wires) to connect the 4AWG to the 8AWG, then put other end of the 8AWG into the charger.

- 8 AWG wire from the charger to the plug, and from the plug to the house battery, about 10ft (3-ish meters) one-way. This wire will only handle the 30A output from the charger. This is the hardest part to rewire so 8AWG makes things a lot easier.

I'm having a friend check my calcs for peace of mind, but I figured I'd run it by you and see if it this sounds completely insane to you. If you could let me know, I'd greatly appreciate it.

By the way, are you at Bay Marine Supply in San Diego? You've been really helpful, I'll be sure to put in a good word about you as I meet other RVers.

Thanks!

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Justin Cook ♦♦ theodk commented · Mar 27, 2020 at 03:52 PM

@theodk, yep, that's us in San Diego! TBH we're pretty well-known around the country in the RV world already, but we always appreciate another good word!

Your plan looks decent; the 4AWG will carry 45A at 12v 30' round-trip with only 2.88% voltage drop... not great, but within spec. Plus, in reality, it's not going to actually be 45A 99% of the time, and it's not going to be 12v either... should be closer to 14v in reality, so this should work well.

Your 8AWG running 20' round-trip will carry 30A at 12v with a 3.23% voltage drop... not good... but then again, that'll never actually be 12v, it should be 13.5v or better, which puts it at 2.87% v-drop. Still not awesome, but within spec.

Just make sure to fuse or breaker both sides (with good Bussman or Littelfuse fuses or breakers, none of that Amazon knockoff junk) to protect those wire runs and you'll be good!

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Answer 1 · 2020-06-13T00:08:34Z

Hi @Justin Cook - Bay Marine Supply USA

I am from Brazil and I am very happy to have found friends and this Victron Energy community because I have been looking for help for a project of mine for a long time, which I explain below:

I intend to buy an Orion-Tr Smart isolated 12 / 12-30A (360W) or 12 / 12-18A (220W) but I have technical doubts about which one to buy and how it works!

Well, I have a S10 Chevrolet 4x4 Diesel 2019 Pickup with alternator of these new (smart) 140A and a "Camper" on top of the bucket we want to travel across countries, and I need to charge my batteries better during the trips and I don't want to depend on energy external electrical. So I have the following equipment.

- In the Pickup an original lead-acid battery of 70Ah (12V) with alternator of 140A.

- In the "Camper" four Lithium-Ion batteries (but I'm changing to 4 LifePo4 equals I think are better) of 12v - 125Ah each connected in parallel totaling 500Ah.

Ps .: In "Camper" I also have a 310W solar panel with an MPTT controller (not from Victron) connected to the batteries, which gives me in good sunny conditions, a current of about 23A. This is currently my only source of battery charging for the "Camper/Mini Motorhome" and I depend on the sun and good days. So I intend to connect the Pickup's alternator and battery with my Camper to help with the charging of the Lithium batteries while driving or when the engine is running. Looking for the solution, that's when I arrived at the solution of an Orion-TR-Smart, but which ?? Will it work? !!

Doubts:

1- In Orion's 360W datasheet, it shows that it delivers 30A at the output (and up to 40A), and you wrote in a post (@theodk) that at any given moment it would pull in the input (battery / alternator) from 38 to 45A. I ask, could that force the alternator, warm up a lot more and work harder at the limit? See that the Pickup when I drive at night and with rain for example and have everything on, like high and low headlights, headlamps, air conditioning, windshield wipers, radio, GPS, cell phone chargers, charging the Pickup battery more etc.etc. the alternator must be generating high currents, and having to send as many 45A as possible to the Orion-TR Smart wouldn't it be bad or do these alternators work very loose even at maximum loads of all electronics that the car originally requires?

Taking this situation into account, would it be better this 360W or the Orion 220W model that would pull less from the van / alternator?

2- Orion will be installed inside the "Camper" next to the batteries, and this should give about 6m of wires from the front of the truck's engine to inside the Camper. (I intend to use 5 or 6 AWG wire). I ask, do I need to take the two wires straight from the battery or could I just take a red one (from the battery's positive) and pull the negative back there straight from the chassis of the pickup truck and then go inside the Camper. In other words... CONTINUES IN THE NEXT POST ...

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