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Whats the latest in DC-DC charging on a vehicle that doesnt break the bank?

Maast

Compulsive Tinkerer
Joined
Oct 31, 2019
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Washington State
Whats the latest best value DC-DC charger from the starter battery to the house bank? The latest I remember seeing was a 50A from Renology but that sucker is 300 bucks, is there anything out there thats a better value that doesnt require connection to the ignition switch?

Havent been posting much lately, I'm doing a 6.0L Chevy Express 3500 Extended van build for a late-20s homeless couple that are living out of a almost dead 1995 car thats past its last legs. They've been doing work for a few years for a neighbor and one day I got to talking to him and learned they were living in that beat to snot car for 4 years and their story broke my damn heart - lost job, lost kids, and it just got worse from there.

Bought a 15 pax express van on a public surplus, ripped out the seats and have been doing hot water/shower/sink/portapottie/bed/stove/diesel hot air heater build and I'm now at the power systems. The OEM van alternator is a 145A output and the house bank is 280AH LFP from leftover new cells I was testing before I went with the BYD modules.

Havent done solar panels yet either but I pretty much know exactly what I'm going to do there.

BTW, I'm not a complete sucker for a sob story. I've got a huge job going where I'm building a 95 foot 8' high retaining wall across my back hard and filling it w/ about 18000 yards of fill to level it up so I can build a shop back there. I'm hiring him @ $15 an hour to move and spread dirt and help me build the wall but 75% of his pay is being held by me to recover the cost of the van & build and I'm holding the title until he gets to 80% of the cost (though I havent told him the 80% part).

I spent 6 months sleeping under pine trees when I was 20 so I realize just how hard it is to get back on your feet when you have no address and no good way to get clean enough for a job interview, safe place to stash your stuff, or the ability to get to work consistently on time. 30 years ago and it still puckers my butt when I think just how close I got to going down for the count before I got back on my feet. Can't imagine having a family in that situation.

At any rate I'm trying to keep the costs down and keep the total under $2500. I've been able to do a lot w/ ebay and craigslist but $300 for a single component sticks in my craw. Aliexpress'll take too long.

Any thoughts?
 
First, its heartening to see your support for the couple. (y)
Next, not sure how relevant it would sound given variance in weather conditions in your part of the world, but why not put that money to buy pre-cared additional solar. That 280 Ah should not take much time to charge quick with a moderate (500-800 Watt) roof solar install (+optional portable Panels).
Reducing dependence on that old used alternator would keep things easier in the long run, where due to excess drain that alternator might strain itself and jeopardize travel plans.
Placing provision to switch-over to Grid, when⚡supply is available should help.
 
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First, its heartening to see your support for the couple. (y)
Next, not sure how relevant it would sound given variance in weather conditions in your part of the world, but why not put that money to buy pre-cared additional solar. That 280 Ah should not take much time to charge quick with a moderate (500-800 Watt) roof solar install (+optional portable Panels).
Reducing dependence on that old used alternator would keep things easier in the long run, where due to excess drain that alternator might strain itself and jeopardize travel plans.
Placing provision to switch-over to Grid, when⚡supply is available should help.
Unfortunately we're in the Pacific NW west of the cascades, we dont have solar for half a year :) Well, we do but you have to have a honking big array to get a usable amount of power out of it, far more than a van rooftop can fit.
 
Just occurred to me that we can probably parallel the 40A units. Two $200 units but that provides redundancy for a critical system and we get more amps into the house bank. Still bites the budget but livewithable.
 
Just occurred to me that we can probably parallel the 40A units. Two $200 units but that provides redundancy for a critical system and we get more amps into the house bank. Still bites the budget but livewithable.
Sure, looks like a plan.
Additionally how about putting a second alternator into that accessories belt, just for charging Home Battery Bank?
 
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What about feeding a solar charge controller from the alternator?
Alternators produce way lot more Amperage for a domestic SCC to handle, but yes a matching SCC could help.
Second Opinion from other forum members, who use alternators for charging RV banks could shed some more light on prospective Issues/solutions.
 
What about feeding a solar charge controller from the alternator?
I dont think a SCC can handle the direct output from a alternator, the output on those things is extremely dirty. Interesting idea I'll have to look into it.
 
Do you need solar too? Renogy has one but it's only for 12v systems.
 
Bogart's SC-2030 SCC can be used to tame the alternator output to 30A

mark
 
What about feeding a solar charge controller from the alternator?
MPPT controllers require some voltage differential between the out (house battery) voltage and the input (alternator). In this application, that differential won't exist. Either a DC-DC boost converter or a good quality current limiting PWM controller would work. If using a PWM controller, have a switch to select solar or alternator and save some $s.
 
MPPT controllers require some voltage differential between the out (house battery) voltage and the input (alternator). In this application, that differential won't exist. Either a DC-DC boost converter or a good quality current limiting PWM controller would work. If using a PWM controller, have a switch to select solar or alternator and save some $s.
That 280Ah sounds to be in 4S configuration. Alternators generally product around 14.5V so should be able to feed LiFePo4 @ 13.5 without much hassel I believe. Main issue remains of regulating and taming the high Ah(150Ah) alternator supply to under 30, without blowing SCC.
 
That 280Ah sounds to be in 4S configuration. Alternators generally product around 14.5V so should be able to feed LiFePo4 @ 13.5 without much hassel I believe. Main issue remains of regulating and taming the high Ah(150Ah) alternator supply to under 30, without blowing SCC.
Alternators put out 14.5V at high revs and for a short time immediately after engine start. ATt other times, it is usually 13.5-13.8. Besides, 14.5V does not provide the voltage differential required for most MPPT controllers.
The unit suggested by @mkaye has an onboard shunt and limits current to 30 Amps. Not sure if other PWM controllers in the market can limit current in the same manner.
 
Bogart's SC-2030 SCC can be used to tame the alternator output to 30A
This is perfect, even has a 30 second delay but it does require the Trimetric 2030RV-F Battery monitor when used with LFP cells which brings the price back up to $280 or so. Looks like the 40A renogy is the best bet. Won't be that big of a deal to run the d+ to the accessories fuse at the truck fuse panel. Or I might rig a zener diode to trigger the d+ turn-on signal to 13.4 volts at the starter battery. That'd also let me not have to run another wire up to the front.
 
This is perfect, even has a 30 second delay but it does require the Trimetric 2030RV-F Battery monitor when used with LFP cells which brings the price back up to $280 or so. Looks like the 40A renogy is the best bet. Won't be that big of a deal to run the d+ to the accessories fuse at the truck fuse panel. Or I might rig a zener diode to trigger the d+ turn-on signal to 13.4 volts at the starter battery. That'd also let me not have to run another wire up to the front.
The SC-2030 does not require a TM-2030 to work with LFP. A TM-2030 is needed only for creating a customized charging profile. SC-2030's built-in AGM profile is very close to commonly recommended LFP profile - absorb @ 14.3V, float @ 13.2V
 
The SC-2030 does not require a TM-2030 to work with LFP. A TM-2030 is needed only for creating a customized charging profile. SC-2030's built-in AGM profile is very close to commonly recommended LFP profile - absorb @ 14.3V, float @ 13.2V
Except you don't float LFPs and there is very good evidence that if you do, even at reduced voltages, you reduce cell lifespan.
 
a float of 13.2V is not high enough to get current flowing in a LFP battery
 
i read an article by nordkyn - mentioned in another thread
their testing showed no charging really occurred <13.2V, but i can't seem to locate it
i know i read it somewhere
i didn't mean that no current would flow <13.2V, just charging current
 
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