School me on the subject of dc dc charging at 12v system.

[ohv]

I am working on a 12v 300ah system in a milwaukee roller packout, diesel heater and combo refrigerator.

I see all the brands on Amazon for higher charging however if I'm just driving and have this battery that has its own mppt charger do I really need a dedicated device under the hood?

I will run a Anderson plug to the bed off 8gauge wire from the battery/fused/switched to give power where the refrigerator/battery would sit.

 

[gator70]

DC-DC charging has pros and cons. (1) add up all the costs to install one. See if that is worth the 20 amp charging. Above 20 amps, do you risk your alternator? Some folks say no, some say yes.

 

[ohv]

DC-DC charging has pros and cons. (1) add up all the costs to install one. See if that is worth the 20 amp charging. Above 20 amps, do you risk your alternator? Some folks say no, some say yes.

I do agree it's a bad idea to add the stress on the alt. I was budgeting for no more then 20amp and my main thought was keeping the dual batteries in the rig for starting power in colder times. I live in socal but spend a few weeks in Yosemite and Kings during the wintertime.

 

[gator70]

I do agree it's a bad idea to add the stress on the alt. I was budgeting for no more then 20amp and my main thought was keeping the dual batteries in the rig for starting power in older times. I live in socal but spend a few weeks in Yosemite and Kings during the winter time.

Based on your response - lists the parts and cost

 

[DirtWhiskey]

Stress on your alternator? Upgrade your alternator. There are no cons. Do it. Before solar.

 

[rruff]

Stress on your alternator? Upgrade your alternator. There are no cons. Do it. Before solar.

If your alternator is easy to replace, I'd agree... but some are very difficult to get to and replace... $$$.

Beside that, you do pay the fuel to run it. And if you idle your rig to charge, then it's very inefficient and hard on your engine as well.

 

[DirtWhiskey]

If your alternator is easy to replace, I'd agree... but some are very difficult to get to and replace... $$$.

Beside that, you do pay the fuel to run it. And if you idle your rig to charge, then it's very inefficient and hard on your engine as well.

I'm not sure I follow. I've never seen an alternator that is hard to replace, but I'm sure they exist. Vast majority of alternators can take a 20 amp draw out of the box, 40 amp might cause issues but you really should be doing a 40a DC DC if you're going to the effort. Installing a solar system is much more complicated than installing a DC DC charger. Fuse at the battery, cable run into a DC DC box, done. It charges as you drive. I never idle my truck to charge my house batteries. 400ah bank runs everything for a week.

If you plan on parking it for more than a week in one location, sure it's probably not the best. If I'm parked more than a week it's because I'm going on foot deep into the wilds, a time when I'm not using anything or creating draw on the batteries.

I always recommend charging house batts off the truck as the first mod, because the source of charge is always there when you're driving, then solar if it's needed.

 

[rruff]

It will depend on your use case. I park for 2 weeks stretches (on a trip lasting months) more than an hour from town, so I could get a good amount of charge with one... if I needed it. I don't use as much electricity as most though, and live and camp in sunny areas. I have about 2600 Whr in storage, and a 200W portable panel and never get close to needing more.

My truck is an example of an alternator that is hard to replace, based on the testimony of others. $1000+, mostly labor. I don't know what typically wears out on an alternator, and if an added modest use would even shorten its life.

 

[ohv]

I had an Amazon giftcard and went with a Victron Energy Orion-XS Smart DC to DC Charger. It can dial down and be configured as a power source vs charger.

I like it has a sense not to drain the main battery off the truck when it isn't on. 06 ram wh 5.9l. I have two 'full throttle' batteries.

 

[RVflyfish]

Before I do solar on my van, I’ll do an upgraded alternator, one that has more headroom even at idle like they use on ambulances. Then a 50A DC-DC charger. As DirtWhiskey said, it’s a lot less complicated (and cheaper) than solar.

 

[eugene]

And if you idle your rig to charge, then it's very inefficient and hard on your engine as well.

Only for carburetor engines. Modern EFI are very efficient and its not hard on them at all.

 

[craig333]

Solar isn't complicated. Easier to install than my DC-DC charger too. My charger so rarely sees any use I'm even thinking of uninstalling it.

 

[rruff]

Only for carburetor engines. Modern EFI are very efficient and its not hard on them at all.

The effect on the engine seems to be a murky area, but I'm pretty sure idling a 300 KW engine to produce .5 KW of electricity is not going to be efficient.

 

[eugene]

The effect on the engine seems to be a murky area, but I'm pretty sure idling a 300 KW engine to produce .5 KW of electricity is not going to be efficient.

Small generators are surprisingly inefficient compared to modern vehicle engines. I've seen people in extended power outages compare both and find the fuel usage was very similar.
But the main point is it won't harm the engine.

 

[rruff]

My truck warmed up and idling with no load of any kind burns about .5 gal/hr... so it definitely won't be efficient then. But when driving, the efficiency of a small marginal load to run the alternator should be good.

I'm having trouble determining if the alternator would wear out sooner (probably) and if so, how much. In other words how much of its lifespan is related to just spinning vs generating power?