DC to DC House Battery Charging?

[CountryFit]

op,
in addition to sterling as mentioned by twinboat, balmar MC-614 is another good one, check it out.

[cv4wheeler]

Originally Posted by 1bigmess

Ruining the engine without a decent load isn't good for it, either. At least change your oil earlier or start getting the oil tested to see if it's loaded with fuel.

My goal is to minimize the time spent charging by idling. I never stay any place more than 2-3 days without getting out and driving around, which should give a good boost to the batteries if the 45amp Sterling dc-dc charger works as advertised. Then I can top off with the little Honda generator via a 25 amp COTEK ac-dc charger when in camp, as needed.

Received both the Sterling charger and the dc-dc power supply for my BIPAP. Both are pretty substantial pieces of kit, serious stuff! I had to find a different place to install the battery charger, it would not fit where I had planned. It is installed and preliminary tests indicate it seems to be working. It is putting out 14.62 volts to my old batteries, just the kind of thing you want to see for the last 25% of charge on lead acid batteries. Supposed o be 14.8 volts, perhaps I miss-set the dip switches--in any case, a huge improvement.

My efforts to recondition my old batteries have failed (not sure why the really old battery that sat discharged in the rain all winter was so easily reconditioned), so it is off to the battery store to get a set of Trojan batteries. Then, once I am sure everything is working, I will get the ac-dc smart charger, change the oil on my little generator and be ready to go for the backcountry. Better late than never.

[cv4wheeler]

Originally Posted by CountryFit

op,
in addition to sterling as mentioned by twinboat, balmar MC-614 is another good one, check it out.

Looks like another good option, more configurable than the Sterling unit, but the flip side is that it is considerably more complicated. I have the Sterling in place, and it seems to be operating correctly, delivering high current (40A) and 13 volts when the batteries are in a state of deep discharge, and then high voltage when the batteries are approaching full charge (14.62 volts). Still haven't played with the dip switches to see if I can get the full 14.8 volts out of it--the switches are not that accessible in the place where I was forced to install the charger.

Monday I go dump the unsalvagable Costco Marine batteries and put in 2 big Trojans. With hundreds of dollars of batteries on the line, I will be particularly diligent at battery maintenance!

[cv4wheeler]

[QUOTE=cv4wheeler;3164197]high current (40A) and 13 volts when the batteries are in a state of deep discharge, and then high voltage when the batteries are approaching full charge (14.62 volts). Still haven't played with the dip switches to see if I can get the full 14.8 volts out of it--the switches are not that accessible in the place where I was forced to install the charger.
________
To keep the conversation going, and for web posterity, upon which I rely so heavily...

I have completed the testing of the Sterling DC to DC charger and find that it works almost exactly as advertised. The only deviation is that the charging voltages are 0.2 volt higher than stated in the manual, regardless of the type of battery (and hence charging profile) selected. I assume that this is because they anticipate more voltage drop in the wires that is present in my system, where the charger is very close to the batteries (12 inches) and the wires are heavy gauge (6 gauge). So I can charge at 15 volts or 14.62 volts, but not at 14.8 volts, which is recommended by Trojan--small difference, I expect it will work fine at either setting. I am currently going with the 15.0 volt absorption charge and 13.85 volt float charge, and keeping a close eye on battery water levels.

The new Trojan T-1275 batteries are amazing, a whole new world for me. Right now they hold a charge of 12.90 volts with a specific gravity of 1.325--amazing, well above spec. Surely they will settle into normal mode soon, but I am enjoying the "supercharged" batteries while they last. I drained a measured 27 amp-hours at approximately the C/20 rate (i.e. I engaged the 3-way refrigerator on DC for 2 hours) and sure enough this resulted in a voltage drop consistent with a 9% discharge, exactly equal to the spec.

Shortly I will receive the COTEK AC to DC 25 amp smart charger, which will allow smart charging from my 650 watt Honda generator (and at home, easier than lugging my big wheeled charger into the camper). I decided to improve the wiring and fusing of the system and have ordered a heavy duty 4 fuse "Maxi fuse" block.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
This will replace 4 main inline fuses, making it much cleaner and serviceable.

I realized that I have neglected to install a low voltage cutoff, to save the batteries if I make a mistake and leave a load on the system when I am not using the camper. With $400 worth of new batteries, I care deeply. After the usual research, I have ordered this highly configurable and inexpensive unit from a company called Manson, new to Amazon, a US front for a company in Hong Kong-- https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It allows the cut-out voltage to be adjusted from 10.5 volts (100% discharge) to 13 volts, although I don't know what you would get setting it to 12.8 or 13 volts. But in between there are many different options, corresponding to shallow, medium or deep battery discharge. Very cool. I will test it and report my findings.

[twinboat]

I'm curious if it has any kind of delay before cut out.
A few second of sagging voltage, during a motor startup, may give you a false shutdown.

Since the batteries can tolerate a few deep discharges, you could set an 80% discharge, cutout voltage.

That shows one benefit of a small solar panel. If you do run your batteries low, storing them in a discharged state, can be life shortening. Even a small system, in less then optimal light, will recharge them over time.

Keep reporting on your progress.

[cv4wheeler]

[QUOTE=twinboat;3180737]I'm curious if it has any kind of delay before cut out.
A few second of sagging voltage, during a motor startup, may give you a false shutdown.

____
The cut-out has a 15 second delay to account for transient voltage drops.
https://www.google.com/url?sa=t&rct=...fQWAGwm8p6yNrw It seems like a very elegant system, if it works as advertised.

Good point about having at least a minimal solar system!

[1bigmess]

I have this LVD in my wish list. If/when I get one, this one will be it, mainly due to the good reviews.

https://amzn.com/B00GZOP53M

[pasdad1]

Here is another LVD type switch. The amp rating of all I have seen is too low to run all the coach current through.....so it would seem reasonable to make the LVD activate the main 12v cutoff solenoid.

[cv4wheeler]

Originally Posted by 1bigmess

I have this LVD in my wish list. If/when I get one, this one will be it, mainly due to the good reviews.

https://amzn.com/B00GZOP53M

Yes, this looks like a very nice option, although it has a more limited range of adjustability, from 50% discharge to 100% discharge (per Trojan specs). But this covers what the vast majority of people would want. Limited to 65 amps, but this would cover my needs in the vast majority of cases.

[cv4wheeler]

Originally Posted by pasdad1

Here is another LVD type switch. The amp rating of all I have seen is too low to run all the coach current through.....so it would seem reasonable to make the LVD activate the main 12v cutoff solenoid.

Attachment 134342

https://powerwerx.com/low-voltage-di...-battery-guard
Looks like yet another good option, very configurable with respect to voltage. Low standby current. Limited to 35 amps, but as you say, can be configured to run a solenoid. It has a useful high voltage cut out at 16.5 volts, just above an equalization charge voltage.

The LVD I am trying is rated to 100 amps, more than I would ever draw now that I have abandoned trying to run a microwave off of batteries! We shall see how it works out. I feel a little sketchy buying something directly from Hong Kong, but my son assures me that he does this all the time. It was purchased through Amazon, so comes with the Amazon assurances, presumably.

I love the idea that all of this good information will live on in cyberspace for others to refer to!

[CountryFit]

Originally Posted by cv4wheeler

The LVD I am trying is rated to 100 amps, more than I would ever draw now that I have abandoned trying to run a microwave off of batteries!

just so you know some of the microwaves could draw much higher current than 100a. i have observed 157a draw by my sharp carousel convection unit; it's a 2000 model though.

[cv4wheeler]

[QUOTE=cv4wheeler;3181868]https://powerwerx.com/low-voltage-di...-battery-guard

OK, let me close this series of posts with a summary of how things worked out, for internet posterity. Links to all of this equipment can be found in prior posts in this discussion. Thanks to the many who provided valuable input.

The Trojan T-1275 deep cycle batteries--Fantastic, exceeding my expectations (based on several rounds of experience with COSTCO marine deep cycle batteries). The batteries seem to be operating above spec (in terms of resting charged voltage and charged specific gravity, as well as amp-hour capacity), and real deep cycle batteries are not supposed to reach spec until perhaps 25 discharges. Perhaps the Trojan specs are just really conservative.

Sterling DC-DC Smart Charger--Fabulous, works like a champ. Only drawback is that it is kind of big physically and sort of expensive. Also slightly noisy when the fans kick in. Hardly matters, given that it only operates when the truck is running. The series of LEDs that indicate function are a bit confusing, and require a good line of sight to the instrument, limiting the places you can install it. There is a remote readout available to bypass these problems. Not sure if I really need this, as the instrument doest really need me watching it, but I might buy one.

Cotek AC-DC Charger--Excellent, although I did find that I cannot use my old Honda 650 generator to run this charger at altitude. The loss of horsepower due to the thin air (I tested at 7700 feet, 23% loss of horsepower) means that I will need at least a 1000 watt generator. I do object to the placement of the function LEDs on the back of the unit instead of on the front, where the power switch is--this limits the places you can install the unit. A minor quibble. Also, the users manual that came with the unit was outdated, I had to use the on-line newer version.

Manson Low Voltage Disconnect/Circuit Breaker/Master Disconnect--This well made LVD seems to work pretty well, although the cut out setting I tested was off by 0.1 volt. Also, the cut-out options are not really optimal, there is alternate gear available that might be a better choice. I configured it with a master-off and bypass switch, using a simple DPDT center off switch from Radio Shack (yes, we still have Radio Shacks where I live). I am satisfied, with no expectation of changing this item out.

The Scosche Core Maxi Block Fuse Power Distributor (fuse block)--Beautiful, functional, well made piece. It uses allen screws to secure the wires to the block--I might have preferred ring type terminal connectors, but time will tell if the allen set screw approach works.

Resmed DC Power Supply (For BIPAP)--Very heavy construction, very well made. Works like a charm in the camper, clearly drawing less power DC-DC than running the AC power supply off of the battery converter (DC-AC-DC).
CPAP.com - DC Converter 24V 90W For AirSenseâ„¢ 10 and AirCurveâ„¢ 10 Machines

So, after the investment of $1100, the DC system in the camper is about as good as it can get. Now I need to buy a 1000 watt or the ubiquitous 2000 watt Honda generator. Solar, probably not, for reasons described previously.

[1bigmess]

Thanks for the follow-up!

[Phil G.]

After reading this entire interesting thread, I have some comments after the fact (most of which are probably way too late to affect what you did/do) :

- Why (did you) go with a bigger single alternator ... dual alternators for redundancy is the best arrangement for maximum reliability when camping out in the middle of nowhere.

- If you do (did) add a bigger single alternator ... (did you) add a big enough one such that at idle it's output is still up there where you need it. High idle is not necessary if one sizes a single alternator appropriately .

- Why did/do you think you needed the (relatively expensive) Sterling? A big single, or dual alternators, plus larger cabling should have delivered plenty of charging current at the proper battery terminal voltage.

- Is your little Honda generator and EX650? We carry one of these along all the time in our small Class C motorhome for battery charging. It's in pristine condition and starts right up. It's also one of the quietest small suitcase generators ever offered for sale (54dB at all power levels).

Good job on your research and the whole project, BTW!