Troubleshooting Renogy 20A DC-DC converter?
- Thread starter Martinjmpr
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DaveInDenver
Middle Income Semi-Redneck
If it gets you what you want it's fine, albeit with the extra complexity.
You already have a decent charger in the DC-DC just my opinion the better effort is to figure out what's really going on. For one, that 9A might not be wrong. Have you verified that by discharging some and making sure? The current is supposed to taper.
I do admit that while my $0.02 is this way should be unnecessary there is an advantage in that stepping up the voltage on the long leg drops the current by a factor of 10. So say you need 500 watts. That's 36A@14V at the alternator into the inverter -> 4.2A@120V on an extension cord -> back to 36A@14V at the battery charger. You won't have as much voltage drop on that long leg. That's the small bonus for all this headache.
Just to be a broken record, there's no reason what you've done should not work. It's pretty much what I do in my truck without any issue. I have an 8AWG branch from the engine bay to a panel in back of the pickup bed that feeds a Victron 20A DC-DC in a portable box on a short 10AWG cable. My truck is an old Toyota with a notoriously low outputing alternator. At idle the voltage droops and the drop is significant, so I cannot idle either. But at highway speed I get full charging through the DC-DC.
Sort of to your basic idea, though, rather than a parallel charger it's completely acceptable to feed a DC-DC with a plain old power supply.
That's in fact what I do if I may have a mains option like a commercial campground or parked at someone's house. The supply I use for this is a Powerwerx SS-30DV but any supply capable of 25A works, standard Meanwell industrial supplies, etc. The main reason I use this one is that I was using it for ham radio and had it set at 13.8V.
A regular 12V industrial supply will be actually 12V and the one large enough I had handy (a 50A one) could not be tweaked beyond 12.6V. This is too low since my DC-DC is set to use >13.2V as a turn on and <12.7V for engine shut down detection. There's other supplies that have different voltage and ranges but I already had this Powerwerx not being used so problem solved. It's small and I don't always bring it with me unless I know I will have 120V available and it's therefore with the effort.
FWIW, I use solar to charge when I'm parked off grid, so the DC-DC is for driving or shore. My power needs are lower than yours, just the fridge, and a 100W suitcase solar panel covers me. Maybe an extended foul weather episode but it's not a major issue for me. This box easily runs a couple of days and I can return a lot of energy with a little bit of driving.
Sure, a decent charger can be 12V or 120V or solar.
Maybe, probably. With everything off at idle my guess is you'd have sufficient power to do this but without knowing the actual alternator performance and pulley ratio can't say for sure.
Generally speaking if you idle at about 700 RPM with a 2:1 ratio (so the alternator is spinning at 1400 RPM) I'd guess a 240A alternator would be able to supply about 120A or so. At 3:1 ratio, alternator RPM of 2100, it should be 75%, maybe 80% of rating. But like I say I don't know what Ford used, probably closer to 3 than to 2.
Yours may also be a smart alternator and will know to idle up with a heavy load, although I doubt it would need to for just this. By about 2500 RPM (alternator RPM, so engine x ratio) most alternators are getting close to rated and by 3000 RPM it should be 100%, so it doesn't take a lot of engine RPM to get full output.
Hard to say. In theory a 1kW inverter should work. I'd only suggest reading spec and reviews, manufacturers are notorious for fudging numbers.
My first reaction when seeing a less common brand is to assume 1,000 watts is it's max and it would not actually be rated for that continuously. Their manual is very thin and doesn't give me any hint either way. I'd assume this is a 500 watt inverter for your purposes, which would still potentially be fine up to about a 30A/12V class charger. Just not knowing for sure bugs me.
https://images.thdstatic.com/catalog/pdfImages/54/549337cb-0183-4a66-94cd-c33a9fb04a09.pdf
For comparison a better way to spec is perhaps this Renogy line.
https://www.renogy.com/1000w-12v-pure-sine-wave-inverter/
It is explicit in a pretty decent tech manual: 1000W continuous, 2000 watts for up to 1 second. Based on their specs I would have no qualms about suggesting their 700 watt one would actually work if you end up going down that path.
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DaveInDenver
Middle Income Semi-Redneck
I think we all sympathize. It's not a one size fits all answer. Using a DC-DC should be fine, although for 200 A-hr a 20A charger is a little light. If you run down completely that's still a 10 hour recharge idle even once you get all the kinks ironed out.
To be honest the suggestion above to hard wire an inverter and use a 120V battery charger is pretty reasonable way to solve the long cable voltage drop issue.
Ideally you'd use more like a 40A to 50A charger for your house battery and that's going to take more like a 4AWG run to the back. If you put the inverter close to the engine then you only need a short 4AWG to it. There is some risk to running 120VAC through your truck but it's not insurmountable with good workmanship.
I agree with you on the generator question. You already have half a generator under the hood of the truck so doubling up on that is less better. In my last post I didn't realize you had 200 A-hr that you run down so fully. That tilts towards the inverter solution a little more. I'd probably take the time to wire a big Anderson plug on the battery, maybe a SB120 with an inline fuse, instead of jumper cable alligator clamps for connecting an on demand inverter.
I'd still personally not want the complexity and just bite the bullet with a larger 12V run and bigger DC-DC or a permanent 120V method. Whatever the solution I'd use one that works the same whether you're driving or just parked idling. But that's only an opinion, there's more than one way to solve this.
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Congratulations on Dave’s advice and now having a functional DC-DC for one of your batteries!
If I already had a DC-DC charger installed, I would not do the direct wire method since that seems more than enough amps based upon your past experience with that battery.
Yes, the brown cord from front to back on a previous picture is a cheap, burn your house down, 20’ 16 gauge extension cord with the ends cut off and Andersons installed. I already had Andersons on short wires to the batteries. Direct connection. About 6 amps. About 12’ of #10 wire gives a little over 20 amps. Fused, if permanent.
Back to the 120vac inverter at the start battery, extension cord to the rear, and a battery charger (power supply) plugged into the extension cord. That’s what you see in the pictures below. The 20’ white extension cord is another el cheapo #16.
The pictures below also show that 40 amps of battery charging at the rear required 43.9 amps of charging current from the vehicle into the inverter up front. Not too shabby. Works for me with a 130 amp alternator at idle. Another picture shows 72.3 amps when I adjusted the charging amps to 70. A clamp-on DC ammeter is a valuable tool.
That means that however many 12v amps you need at the rear requires a few more from the front (alt). Using the about 10:1 rule of thumb for inverters, 120v, 15amps into your camper means about 150 amps from your vehicle/alternator. 15 amps X 10. That means about 150 alternator amps to produce 15 amps from an inverter to equal a 15 amp 120vac trailer hookup.
That same 10:1 means my 40 charging amps equals about 4 amps through the extension cord.
The 1000 watt inverter you mentioned could provide about 8 amps of 120v and require about 80 amps from the vehicle, and provide about 80 amps of battery charging at the camper.
My 10 year old camper trailer’s converter (inverter) outputs less than 14vdc except for short equalization periods that are higher than the lifepo4s supposed maximum. I need to investigate further.
I plan to use the power supply (charger) seen below instead of the trailer's converter when shorepower is available, or gggrrrr, when I HAVE to fire up that noisy-ass, supposedly quiet inverter generator.
If I already had a DC-DC charger installed, I would not do the direct wire method since that seems more than enough amps based upon your past experience with that battery.
Yes, the brown cord from front to back on a previous picture is a cheap, burn your house down, 20’ 16 gauge extension cord with the ends cut off and Andersons installed. I already had Andersons on short wires to the batteries. Direct connection. About 6 amps. About 12’ of #10 wire gives a little over 20 amps. Fused, if permanent.
Back to the 120vac inverter at the start battery, extension cord to the rear, and a battery charger (power supply) plugged into the extension cord. That’s what you see in the pictures below. The 20’ white extension cord is another el cheapo #16.
The pictures below also show that 40 amps of battery charging at the rear required 43.9 amps of charging current from the vehicle into the inverter up front. Not too shabby. Works for me with a 130 amp alternator at idle. Another picture shows 72.3 amps when I adjusted the charging amps to 70. A clamp-on DC ammeter is a valuable tool.
That means that however many 12v amps you need at the rear requires a few more from the front (alt). Using the about 10:1 rule of thumb for inverters, 120v, 15amps into your camper means about 150 amps from your vehicle/alternator. 15 amps X 10. That means about 150 alternator amps to produce 15 amps from an inverter to equal a 15 amp 120vac trailer hookup.
That same 10:1 means my 40 charging amps equals about 4 amps through the extension cord.
The 1000 watt inverter you mentioned could provide about 8 amps of 120v and require about 80 amps from the vehicle, and provide about 80 amps of battery charging at the camper.
My 10 year old camper trailer’s converter (inverter) outputs less than 14vdc except for short equalization periods that are higher than the lifepo4s supposed maximum. I need to investigate further.
I plan to use the power supply (charger) seen below instead of the trailer's converter when shorepower is available, or gggrrrr, when I HAVE to fire up that noisy-ass, supposedly quiet inverter generator.
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Martinjmpr
Wiffleball Batter
I like the idea of hard wiring an inverter but there simply is not enough space under the hood to put one and I don't want something that is connected all the time anyway, it's just not necessary.
Obviously there are multiple ways to skin this cat but I'm looking for one that requires the least amount of modification to my truck. As a plus, an off-vehicle solution has the advantage of being "portable" to another vehicle.
WRT the two times the batteries in the trailer ran down, both were somewhat unusual circumstances.
In the first one, in September, we were still using the 4+ year old FLA batteries that came with the trailer when we bought it. Making matters worse, we were camping in Oregon and while the weather was good - in fact, I'd say spectacular - we were under a 200' canopy of trees and even with a detached 100W solar panel augmenting the on-board 100W panel, I never had more than a few minutes of direct sunlight each day. The warm weather actually worked against us in terms of power consumption because it forced the 12v refrigerator to drain the batteries more quickly than if it had been chilly.
The second time, at Key West, my big mistake was in not bringing the detached 100W solar panel. Even though we had ample sunlight each day, the roof-mounted panel was on the "wrong" side of the trailer. The trailer has an arched roof and the front of the trailer was oriented to the West. The panel is on the right side of the trailer which means it was oriented to the North. Compounding this, we were there in late November when the sun is near it's lowest point on the horizon. Bottom line, we never got more than about 1.7A from the panel on the roof. If we had pointed the trailer to the East, which would have put the solar panel under more direct sunlight, or if I'd brought the portable 100W panel, it would likely have put in enough power to offset the draw from the fridge.
So, it seems likely that the ability to charge the batteries from the truck is not something I'm likely to need MOST of the time. Our upcoming trip to Texas this week will have us at sites with electric hookups every night so there's no issue there with power.
In any case, I'll continue to explore this and I appreciate all the suggestions and recommendations people make. This is why I like Ex Po, there are a lot of very knowledgeable people who are willing to think "outside the box" to get things done.
DaveInDenver
Middle Income Semi-Redneck
Indeed Martin, in your use case using a temporary inverter as a fail safe is a fine way to go. No question better than dragging a generator around for what-if.
I don't rely on the inverter solution but I do carry that AC/DC Powerwerx power supply sometimes for basically the same "just in case" reason.
I'm with you on interconnectivity and mix-and-match solutions. Kind of why I suggested having an Anderson SB120 (or bigger) on your battery.
I put SB175s on our cars and jumper cables but also inverters, spare batteries and everywhere. It's quick and safe, no worries of mismatched studs and terminal sizes, dropping a nut in the dirt, wrong polarity in the dark or a clamp shorting to the body. It's like garanimals for electrical.
I don't rely on the inverter solution but I do carry that AC/DC Powerwerx power supply sometimes for basically the same "just in case" reason.
I'm with you on interconnectivity and mix-and-match solutions. Kind of why I suggested having an Anderson SB120 (or bigger) on your battery.
I put SB175s on our cars and jumper cables but also inverters, spare batteries and everywhere. It's quick and safe, no worries of mismatched studs and terminal sizes, dropping a nut in the dirt, wrong polarity in the dark or a clamp shorting to the body. It's like garanimals for electrical.
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Martinjmpr
Wiffleball Batter
Dave: That's pretty much what I'm looking to do. I assume I'd need those big two-handed crimpers you have for wires of that gauge?
Speaking of which, do you have a link to them? It seems that 8AWG is about the biggest wire I can crimp with my current crimper. I don't mind investing in a bigger crimper I'm just not sure where to look.
Speaking of which, do you have a link to them? It seems that 8AWG is about the biggest wire I can crimp with my current crimper. I don't mind investing in a bigger crimper I'm just not sure where to look.
DaveInDenver
Middle Income Semi-Redneck
You do need bigger crimpers for SB120 and larger, although they don't need to be particularly special. For the PP15/30/45 and SB50 using the Anderson specific crimpers is pretty important for them to be reliable but the SB120 and larger are just regular hex crimps.
To answer your question the heavy duty crimpers I have are FTZ model 94284 and my intermediate crimper is an Iwiss model HX-50B.
If you don't want to buy tools you can have a welding supply or battery shop crimp them on. For the most part SB175 terminals require a 50mm^2 hex crimper die. If crimpers are calibrated to wire gauge this will usually cross to the 1/0 AWG size hex. The smaller SB120 usually requires a 35mm^2 die, which may be marked as 2 AWG.
I would suggest buying at least one extra terminal if you can if you're using crimpers you're not familiar with since the marking and quality varies quite a bit (like those Iwiss, not top shelf tools). Sometimes a set of dies marked 50mm^2 are not quite that and you'll find the 35 or 70 works better. So having that one extra for a tester comes in handy...
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