Pros and Cons on Different DC to DC Chargers

[Glennman]

I've been following this for some time but honestly just what problem you are trying to solve eludes me. You have a start and a house battery. Solar panels and the alternator and a generator are energy sources. What's the reason for the combiner,etc.?

Hey windtrader... I just want to be able to charge my 8 lithium house batteries off the alternator without cooking the alternator or maxing it out. The lithiums will apparently cause the alternator to run at max output if, after boondocking, the 8 batteries are low, potentially reducing the alternator's lifespan. I have the Victron Multi-plus II 3000 watt inverter for charging while plugged in, and the 3000 watt solar panels too (literally on a good day!), and no generator. Maybe the solar panels is all I need. I figure that adding about 30 amps of charging while driving, coupled with what I get from the panels, will at least bring the batteries up enough to run the refrigerator or...? Thanks for weighing in!

[windtrader]

Maybe the solar panels is all I need.  Thanks for weighing in!

Is this all installed or are you in design and planning? The solar panels should be more than sufficient to charge the house lithium bank. If it isn't then:1) You have too much draw - add more charge capacity2) You have insufficient solar charging to keep house battery charged - add more panels, if extended low solar charging, then go to pole or onboard generator.3) Depending on your use pattern, adding circuit to charge house from alternator is not beneficial. For example, you spend days parked/boondock, bus does not travel enough to be used as a charging source. We'll assume that running the bus engine to spin the alternator to charge the house batteries is not a recommended option. Can be done but probabaly least efficient way to charge house batteries.

[luvrbus]

I wonder where the word "boondock"comes from,I see people in the desert with solar panels covering the roofs and sides with some panels sitting on the ground,Most are using residential fridges and mini splits,electric cook tops,mircowave ,coffee pots and watching TV with the generator running for 6 hours to make it through the night ,Solar panels are useless in the winter here in the desert we don't have a enough sunshine for the solar to work, the days are short and then we get cloudy or rainy days on top of that and those people dead in the water and running their generator ,or at the swap meets trying to buy one

[dtcerrato]

On our first two Alaska road trips w/o solar we logged around 300 genny hours each trip. On the third AK road trip with just supplemental solar @ 500W our genny use logged in at 9 hours for the whole trip. I'd say that's a pretty good trade off. We are not an all electric bus. We use propane, gasoline & diesel besides electric & all lighting is 12 VDC. We love Boondocking (mountain, rural area, away from the pack, off grid)

[luvrbus]

On our first two Alaska road trips w/o solar we logged around 300 genny hours each trip. On the third AK road trip with just supplemental solar @ 500W our genny use logged in at 9 hours for the whole trip. I'd say that's a pretty good trade off. We are not an all electric bus. We use propane, gasoline & diesel besides electric & all lighting is 12 VDC. We love Boondocking (mountain, rural area, away from the pack, off grid)

LOL you have a backup plan,I have seen buses worth 5 to $10,000.00 maybe with $20,000 in Lithium batteries and they struggle without  generator for backup.Van and I have a friend that is a electronic specialist,and he believes in a generator and is not going to be without one with all his solar and all his Victron system, in fact he had his generator completely rebuilt 2 years

[buswarrior]

Beware, those who go deep into solar aren't too forthcoming about the compromises that come with religious zealotry...
that YOUR Admiral will not put up with...

I would want a way to charge the house via the engine alternator, if for no better reason that redundancy against failure.

Again, the Admiral is going to $#@!  All over you, if some part of that expensive horsehockey that has tied up huge amounts of family treasury, and time, stops working and ruins the vacation plan...

I want to start a support group forum for the long suffering victims of busnuts, with a side hustle in family law.

"Have you been the victim of a Busnut? Compensation may be available..."

Happy coaching!
Buswarrior

[luvrbus]

I don't get it a good solar panel on the average is 200w or 3 amps and you have a 270 amp alternator that produces 6000 watts ,how many solar panels would you need to supply that much power that is there waiting to be used

[Glennman]

Is this all installed or are you in design and planning? The solar panels should be more than sufficient to charge the house lithium bank. If it isn't then:1) You have too much draw - add more charge capacity2) You have insufficient solar charging to keep house battery charged - add more panels, if extended low solar charging, then go to pole or onboard generator.3) Depending on your use pattern, adding circuit to charge house from alternator is not beneficial. For example, you spend days parked/boondock, bus does not travel enough to be used as a charging source. We'll assume that running the bus engine to spin the alternator to charge the house batteries is not a recommended option. Can be done but probably least efficient way to charge house batteries.

All three... Installed: the entire system (as of this week); Design: I'm never satisfied; Planning: I don't do it enough!

I installed the battery combiner, but I'm afraid of overloading the alternator, so I want to install the DC to DC unit instead (this still charges off the alternator, but is metered, lower level charging). I'm not looking to completely replenish the batteries while driving, as 30 amps from the alternator charging depleted 800 amp hours of batteries will require that I drive thousands of miles to bring them back up, especially if the sun isn't shining. I'm thinking that 30 amps from the alternator (DC to DC), plus whatever I get from solar will be enough to at least run the mini split and 10 cu.ft 110v refrigerator while driving, if the batteries are low when returning from a boondocking adventure.

I might just wait for now. I will have a 50 amp shore power on our first trip to Idaho in June. So, I should be starting the trip with a full charge and heading home with a full charge. It's only 300 miles one way, so if I get good sunshine, the batteries should still have good power by the time I reach my destinations.

[luvrbus]

I don't quite understand the concern about the alternator, the regulator protects over charging and if it detects to much heat they reduce the charging rate ,the Balmar regulator is my favorite. It is a better unit than the OEM unit IMO

[Glennman]

I don't quite understand the concern about the alternator, the regulator protects over charging and if it detects to much heat they reduce the charging rate ,the Balmar regulator is my favorite. It is a better unit than the OEM unit IMO

That is very interesting luvrbus. I'll have to look into that before I scrap my battery combiner for a DC to DC charger. Is the regulator outside of the alternator? A "Balmar" regulator can be installed in lieu of the factory one without changing the entire alternator? Thanks for your help!

[buswarrior]

https://balmar.net/

Look for the multi-stage regulator, amongst all the other lovely things that Balmar makes.

Happy coaching!
Buswarrior

[Glennman]

Nice. My son works for a marine outfit. I'll see if they can order stuff from them (Balmar). I can see myself with a separate, dedicated alternator. Looks like they do complete kits.

[mqbus767]

Hey Glenn,

I went through a bunch of this about 2 years ago. You can read my experience here:

https://www.busconversionmagazine.com/forum/index.php?topic=35424.0

I wanted to direct connect the alternator to the house battery using a "smart" combiner, but the output from the 50dn kept tripping the internal circuit breaker on the BB batteries.

What I currently have installed are three Victron Energy Orion-Tr Smart 24/24-Volt 17 amp 400-Watt DC-DC Chargers. They are uber expensive per watt but highly configurable and "safe". They support charging profiles for various batteries, have engine start detection, and bluetooth monitoring. I really didn't want to go this route and may replace it with something else in the future, but they do work. 1200 watts is not much, but I'm also hoping that with future solar it'll be enough going down the road to run the mini-split and the fridge.

P.S. I don't think the 50dn will have any issues direct charging a battery bank as it's rated for continuous use. I might even be able to overcome the battery CB tripping by extending the capacity one day. I tried several times working BB and Victron techs to make it work, but none of them could tell me exactly why it wasn't working. On paper, they all said it should work.

[Glennman]

Thanks for weighing in mq! I read the all the posts in the link you provided detailing your experience. Why didn't you just go with (2) 30 amp units instead of (3) 17 amp ones? Using the DC to DC chargers does appear to be a safer option rather than the combiner. Do you think your experience with the combiner would have been different if you used the Cyrix-li-ct? You mentioned that you accidentally ordered the wrong one. Do you recommend the non-isolated or isolated version. I have a good connection from the house bank to the bus frame for the negative side. Also, I'm thinking that one 30 amp charger will work, or at least greatly help, since I also have the 3000 watts of solar, of course that's on a good day.

[mqbus767]

Hey Glenn,

The 30-amp units are 12v/12v. My house batteries are 24v. When I bought the units, 17A was the largest Victron offered. (That may haved changed.)

The combiner route is a good option only if your batteries can handle the current from the alternator. Nothing I tried in a direct connect setup worked because the batteries simply couldn't take everything the 50dn was able to produce. Victron speculated that a larger bank would be able to handle it, but I was unwilling spend several more thousand dollars just to test that theory. I may one day travel to Victron and have them look the system over and advise. If they can prove that more batteries solves the issue, then maybe I'll go that route.