Wiring idea for charging house batteries

[Kiltym]

I wanted to run an idea past everyone and see if my thinking is flawed, or if it might work.

I am primarily concerned with improving the ability to charge our batteries when away from AC power, as we don't spend much time with access to it.

We do not have solar yet, but will add it at some point.

So right now, primary charging is via the alternator. I am going to install a DC-DC charger to improve the efficiency and ability to charge the house bank from the alternator. I have a few options for this, and I have not made a decision yet.

Just to pass along my thoughts:

CTEK Dual: https://smartercharger.com/products/dcdc/ctek-d250s-dual/
Redarc BCDC1225D: https://www.redarc.com.au/dual-input-25a-in-vehicle-dc-battery-charger
Sterling BB1230: http://www.sterling-power-usa.com/SterlingPower12volt-12volt-30ampbatterytobatterycharger.aspx



Having read some threads on here, and Yahoo group, I was trying to think of a way to use the AC/DC converter we have installed for the air conditioner. I have not checked the voltage this converter produces, but hope it is > 13V. I saw some thoughts on the Yahoo group, but they involved adding wires direct from converter to house batteries, if I remember correctly.

If the converter does produce >13V, what would prevent me from when the generator is on, which is producing AC, which then turns the converter on, and produces DC, to feed that DC power back to the start battery via the existing wires connected to the existing relay? This would in turn charge the sprinter start battery, and assuming the voltage was high enough, engage the relay under the seat and also send power to the house bank (via the DC-DC charger, or even direct).

Obviously with the generator running, the 10A battery charging is doing it's thing also. This would take a long time of running to fill up the batteries which is why I am looking at a DC-DC charger which can put out more, ~30A. Not sure if the 10A charger needs to be taken off line, but I think they could run at the same time and feed 40A into the house back with the generator on.

This would require only minor changes to the relay/converter wiring so there was a way to feed the power back to the starter battery when the converter was running of AC. Even a manual switch could be used.

Right now the exiting AirCo relay will feed from the start battery (alternator) or the converter. So when in "converter mode", I don't see why that power could not also be fed back to the start battery via the existing cables.

Any thoughts/comments? Especially reasons why this would not work.....

 

[OldWest]

1. Compatability

You need to match the preferred charging regimen of the specific batteries to the chargers. Gel batteries do not like high amps while AGM batteries may NEED high amps, but need to look at each specific battery's requirements (versus generalization).

Battery chargers with different charging regimen options may match your specific batteries now or in the future.

The existing Westy battery charger is a dumb one and will.boil the house batteries if left plugged in constantly. Washington State owners added a smart maintenance charger under kitchen sink with a switch to choose either the Westy battery charger or the maintenance charger.

2. Bulk Charging versus Topping Off

The alternator provides plenty of amps for charging.

Your proposed DC-DC charger may provide a smarter charging regimen but not necessarily more recharge amps for same amount of time.

I think I've seen 50-60 amps going into the house batteries when first start engine (reading off a Linklite meter and with Sears Platinum AGM batteries discharged and before solar panels). So the alternator would be limited only by what house batteries willntake (self- regulating to an extent).

DC-DC chargers may limit how much amperage. Also, unless one drive 24 hours/7 days a week, will the smart DC-DC charger be that useful in going through the various stages beyond bulk charging???

The Westy battery charger of 10 amps matches the requirements of the original gel batteries (but NOT the requirements of many AGM batteries which like higher amp charging).

NOTE: But the original gel batteries got high amps from alternator??? Unless self-regulating and not accepting more amps from alternator.

The other proposed use of the air conditioner Meanwell converters would also be for bulk charging.

Topping off the last 10-20% of battery capacity requires many hours of charging (batteries won't accept more amps at this stage) and solar or plugged in (with a better smarter charger) are the best options versus driving 8 hours a day.

Boondockers follow the strategy of a high amp battery charger run off a generator for one or two hours for the bulk charging and then solar for the last charging phase.

Caveat: Our propane generator can run for ??? Hours off the propane tank. Price of propane versus hookup?

3. Alternator Duty Cycles

Seems like a lot of alternators and/or regulators have been replaced.by Westy owners. I wonder if the original Bosch 200 amp alternator was designed for CONSTANT duty to run the Kerstner air conditioner, recharge house batteries, etc.

4. OneManVan Modifications

Search OneManVan's mods (probably on Yahoo Westfalia group). He installed a MANUAL switch to route the air conditioner Meanwell converters (two of them) to bulk charge the house batteries. He may have had to run additional cables (don't remember). The Meanwell converters are basic converters and not smart chargers.

OneManVan also added a MANUAL switch to the battery relay under driver seat so the engine battery can also be recharged by the Meanwell converters.

Clever modifications, but need to pay attention to position of switches, etc. OneManVan knows electric/electronics, but his mods require attention so not for the forgetful.

5. Driving, Generator and Solar

The Westy is limited to boondocking by the size of the water tanks, propane tank, food storage, etc.

Calculate:

(A) the longest time one might go without starting engine and driving (alternator charging),

(B) use of generator (NOISY and not neighbor friendly), and high amp battery charger,

(C) solar recharging, and

(D) how much one drains batteries----

Then figure out system.

200 watts of semiflexible solar panels is enough for me EXCEPT when really hot all day and night and I run Fantastic Fan in bathroom all day.

Otherwise, the two solar panels recharge house batteries (and via a 300 watt inverter and plug-in Battery Maintainer, the engine battery) every day (except if cloudy). So no need to plug-in or run engine alternator or generator.

Someday, when air conditioner dies, I'll replace that area with an additional 200 watts of solar panels (by that time, the existing 200 watts of semiflexible panels on curved roof area may have diminished in capacity).

 

[OldWest]

Portable Solar.

Might also mention that OneManVan put together a portable solar panel for himself and another member here. While OneManVan has the 200 watts of semiflexible panels.on sloped roof, the panels weathered a bit. The portable set up means less exposure to weathering as well as ability to park in shade and run solar panels out into the sun. Can put portable panels on roof, in windshield, etc.

For easy use, the portable panels plug into the 12v outlets so can use to recharge engine battery as well.

This might be an option for you.until you figure everything out. Just get a semiflexible 50-100 (check fuse and wire sizes of 12v outlets)- watt panel, small controller and cigarette plug. Then can plug into the 12v outlets when need some topping off. Easy and no messing around with other stuff.

 

[Kiltym]

Just to be clear, my goal here is not a "final" solution by any means. Adding solar is key to staying off grid, I agree (and a lot quieter then generator/engine).

What I am tying to do is improve the current system, with a fairly small investment, to allow for better charging of the house bank, and at the same time using the generator/converter to also provide the DC power. And, not being plugged in, as we rarely are.

And please don't take my comments below as argumentative, just want to have an good conversation about the proposal (which may be flawed).

"Your proposed DC-DC charger may provide a smarter charging regimen but not necessarily more recharge amps for same amount of time."

The CTEK devices has an add-on called "smart pass" which allows full output from alternator to bank (basically another relay), and then the charger takes over to complete the charge cycle at the proper voltage until full. There are also 60A and 40A versions of the products I posted.

Agreed, the charger has to match the batteries, which I assume I will do.

The advantage of the dc-dc charger is it will actually 100% charge the batteries, where as a "dumb" power source (alternator and converter) would not. If we drive 6 hours, and the batteries are not full, seems like a waste of power. My understanding is adding a smart dc-dc charger in there would allow the full charge of the house bank over those 6 (or less) hours.


"Topping off the last 10-20% of battery capacity requires many hours of charging (batteries won't accept more amps at this stage) and solar or plugged in (with a better smarter charger) are the best options versus driving 8 hours a day."

That is where the generator comes in with the DC-DC charger. If we are able to stay in a single location for a week say, we don't run the sprinter engine, having the generator already there, why not use that at more the 10A that the standard charged provides...

One could replace the AC-DC charger, but I feel my solution (for us, of never being plugged it), is more beneficial since it effects both alternator and generator/converter.

I used to charge a 600aH bank on our boat with a 75A charger in 4-5 hours from a generator (assuming no more then 50% discharge). Not to 100%, but until the amps going in was < 10, which for a 600aH bank, is pretty full.

I agree, solar is better then running the noisy generator, but looking for an immediate improvement without investing in solar at this time, and an alternative to wear on the sprinter engine to bulk charge when sitting still.

"He installed a MANUAL switch to route the air conditioner Meanwell converters (two of them) to bulk charge the house batteries. He may have had to run additional cables (don't remember). The Meanwell converters are basic converters and not smart chargers."

The converter is analogous to the alternator as best I know right now. So by putting a "smart" dc-dc charger in the middle, should charge the house batteries correct via the alternator, or the converter. That's my thinking anyway.

I think I saw his posts, I was just wondering about simplifying with the idea I posted. Perhaps oneman will comment since he is much more experienced with this then I and perhaps already thought through my proposed solution.

If a manual switch we installed between the converter, and the heavy DC cables at the relay going to the start battery, it seems pretty simple. If the switch is closed, power will flow from converter to start battery (and in turn open the relay and onto the house batteries). If switch is open, everything as it is now. If the switch was closed, and the engine is running, there would be power on the line to the converter, but not sure that is a problem or not.

I attached a quick sketch.

For reference, this link has info: https://groups.yahoo.com/neo/groups/sprinter_westfalia/conversations/topics/13660

Specifically post #40. Don't know if "captnalintiverton" and "onemanvan" are one in the same

 

[Kiltym]

"DC-DC chargers may limit how much amperage. Also, unless one drive 24 hours/7 days a week, will the smart DC-DC charger be that useful in going through the various stages beyond bulk charging???"

Forget about the alternator for a moment, and think generator only.

A dc-dc charger should fill the battery in the same time a comparable AC-DC charger would. So running a generator to charge the batteries, whether it goes through a "smart" ac-dc or dc-dc charger, it should be the exact same result.

Now, the bonus with the dc-dc is you get to more fully charge the batteries also via the alternator using the same dc-dc charger. The dc-dc charger will continue to put the correct voltage into the batteries, regardless of what the alternator is doing (which is usually < 14V).

Not debating the value of solar here, just looking for a solution before I invest money and time into the solar option.

 

[OldWest]

CaptAlTiverton and OneManVan are two different people.

Different ideas and methods. All good to discuss. I'm an Internet armchair parrot.expert, so take with a big grain of salt. Like your enthusiasm and willingness to post (especially the photos).

Boondockers with generator want to maximize use of generator. It'd be ridiculous to run a 2500 watt generator to power a 300 watt.battery charger. Better to get a bigger.2000 watt.charger if compatible with batteries. Same with engine alternator.

Issue is when gel or AGM batteries get up to 80% charged (making up number, could be 75% or lower/higher depending upon batteries), the batteries won't accept high amps and the charging amperage drops significantly with a much longer time to recharge.

So the smart battery chargers need to offer some value up to the 80% charged status, like putting out more amps at a higher voltage (all acceptable to batteries).

Beyond the 80% charged status and when fully charged, the chargers need to stop boiling the batteries by dropping the voltage.

Smart chargers brochures all talk about the float voltage.(so no boiling batteries) but this works more for RV storage versus house batteries which are in constant use (fridge).

I looked at the battery to battery charger (DC-DC) years ago, before I got solar. Seemed to make sense that you'd want a smart and more efficient charger, not fooled by the status of the engine battery or limited to the IQ of the regulator.

I decided to pass on the idea for the following reasons:

1. Various discussion re fooling around with the Sprinter sensitive electronics. There is a charger which goes to the alternator and a charger which goes to the engine battery.

The latter, as attached to the engine battery, would avoid touching Sprinter alternator.

But the charger would likely be located in the engine compartment and susceptible to heat.

2. The DC-DC charger suggests one can get greater amp charging from the alternator (depending upon size of the charger).

We have a Bosch 200 amp alternator, which may put out more amps without a charger than with a 100 or 60 amp DC-DC charger???

But if the DC-DC charger can put out more amps at a given voltage.because smarter, that'd be a plus (e.g., engine battery is fully charged but house batteries are not???).

Also, the type of batteries may also self-impose a maximum intake amperage.(gel versus AGM versus lithium) so a bigger amp charger may not be used to full capacity.

So depending upon the graph of the charging regimen of the charger and the graph of charging regimen of the battery, AND where on the the graph you'd be after so much time of driving or generator use, versus alternator alone, then would have to decide.

So would need.batteries which can absorb the maximum output of amps at a given voltage and a charger which could put out more amps at a given voltage so hopefully less time to charge VERSUS alternator alone.

BUT, as you point out, add in the generator, and the low 10 amp Westy charger, and would want a bigger amp charger. And if adding a new charger, why not a DC-DC charger.

Key issue is how long would alternator and/or generator have to run to recharge batteries to a satisfactory level (80% or more???) in combination with no charger or the dinky 10 amp Westy charger, or with a new DC-DC charger.

NOTE: Westy Owner Manual recommends plugging in at least once per month for 48 hours. Presumably, this is so house batteries can be fully charged at least.once a month (which driving around may not do).

NOTE: While gel and AGM batteries reduce the amount of amperage they can accept as they get closer to being fully charged, some of the new lithium batteries can receive the same level of bulk charge amperage until fully charged.

So the lithium batteries would be a much better match (setting aside the other lithium issues).

For example, if had a 100 amp charger, it might take 8-10 or more hours to recharge a 100 amp deficit for gel or AGM batteries (the last couple of hours at 2-3 amps and not 100 amps), but only 1 hour for lithium batteries (making up and exaggerating the numbers).

NOTE: Another non-Westy owner has an inverter attached to the engine battery. When driving, the inverter powers a smart AC-DC charger for house batteries. So owner has protection of a smart charger. Owner has a separate smart battery charger when plugged in. Search forums for discussion on this arrangement.

3. Someday, may get rid of generator if air conditioner goes.

4. Saw the light and found solar semiflexible panels to fit on sloped roof.

 

[Kiltym]

"Issue is when gel or AGM batteries get up to 80% charged (making up number, could be 75% or lower/higher depending upon batteries), the batteries won't accept high amps and the charging amperage drops significantly with a much longer time to recharge.

So the smart battery chargers need to offer some value up to the 80% charged status, like putting out more amps at a higher voltage (all acceptable to batteries)."

The stage after Bulk is called Absorption. The voltage is kept the same (high), but the amps start to decrease as the batteries reach capacity. The smart chargers all offer this. The issue with the alternator/converter is they are not charging the house bank at 14.4 (or whatever it is your batteries want). It charges at about 13.5-13.8, which will never fully charge the batteries. If a smart charger delivers the 14.4 through the entire bulk/absorption phase, I have no doubt the batteries will be better charged then with a dumb alternator like we have.

On our boat, we installed a Balmer regulator (and alternator) which charges smart also, but a dc-dc charger is a easy way to avoid messing with the sprinter side of things.

After absorption, the charger will go to float, and maintain a 13.X charge (again depending on your battery specs). Bulk/Absorption duration will depend on amps going in (size of charger), and state of the batteries.


"1. Various discussion re fooling around with the Sprinter sensitive electronics. There is a charger which goes to the alternator and a charger which goes to the engine battery.

The latter, as attached to the engine battery, would avoid touching Sprinter alternator.

But the charger would likely be located in the engine compartment and susceptible to heat."

I am not clear on this. I would mount the dc-dc charger near the house bank and simply disconnect the existing cable from the house back from the start battery and plug into the dc-dc charger.

Would not touch the alternator, or mount anything under the hood. I have not seen any dc-dc charger that needs to be connected to the alternator. A regulator might be fitter that is "smart", but I agree that it is better to avoid messing with the sprinter stuff.

"The DC-DC charger suggests one can get greater amp charging from the alternator"

Not in my opinion. The goal is for a better (more full) charge, not more amps. If you have a 200 aH bank, and use no more the 50%, you only have 100aH to replenish. A 50A battery charger would do a pretty good job in ~ 3hours. And better then the alternator alone would do in 3 hours, even with more amps, as its only putting out < 14V.

"But if the DC-DC charger can put out more amps at a given voltage.because smarter, that'd be a plus"

This is the key in my approach. I don't think a dumb-regulated alternator (or converter) can do a good job charging batters. I suspect your solar install is providing a huge impact for you as it is charging the batteries correctly.

"3. Someday, may get rid of generator if air conditioner goes.

4. Saw the light and found solar semiflexible panels to fit on sloped roof."

These two I completely agree with. But I figure the dc-dc charger is still beneficial with even just the alternator, but certainly less so if you are always able to "top-up" with solar.

Just curious, what panels did you buy, and how old are they now, and how are they holding up?

 

[OldWest]

Side Note:

Several years ago, I replaced my original gel batteries with Sears Platinum AGM batteries (no longer available). The Sears batteries were rebranded, identical Odyssey batteries, but over $100 cheaper per battery (Jeep and marine forums figured this out). Several Westy owners posted re this good deal.

But, these Odyssey batteries required high amp chargers (don't remember the correct numbers, but maybe 75 to 90 amps for a 200 amp battery bank). Our dinky Westy 10 amp battery would be a bad fit.

(The Westy 10 amp charger is a good fit for the original gel batteries which do NOT want high amps.)

After looking around for a bigger battery charger and issues of the circuit breaker and wiring size, etc., I decided to skip replacing the battery charger. Why?

I figured that most of the time, the battery bank was drawn down only 20-30 amp-hrs at most at the end of a 24 hour cycle in the early morning (200 watts of solar panel)--typically no more than 20 amp-hrs or 10% of the battery bank. Note that during the day, the solar panels recharge the batteries and keep up with any electrical use. Usually fully recharged by noon.or 1:00 pm. So just the night battery drain.

A big 90 amp charger would not be putting in 90 amps at that 10% level of discharge. So the 200 watts of solar panel or the 10 amp Westy charger would be acting very much like a 90 amp.charger at this level of minimal discharge.

For bigger drains or discharges, driving around with the engine alternator would provide the big amps charging the batteries like.

So far, so good. Had 7 years on the original batteries and 6 years so far on the Sears ones. (Anyways, that's my explanation. If wrong, please feel free to correct.)

 

[OldWest]

I have the Solbian semiflexible panels from BruceSchwab.com. I've had this set since August 2013 or so. They have become a bit cloudy/hazy and don't put out as much as they did when new.

Used 3M Dual Lock (like plastic mushroom Velcro) to attach to sloping roof. One panel was trimmed on the long edge so no overlap in middle.

Have the Morningstar 15 amp MPPT controller. (AM Solar installed my solar setup (rooftop junction box, wiring, Linklite meter, shunt, Morningstar controller, except for the solar panels. Can only recommend then with caveats.)

My first Solbian solar panel (2012 or so) was a mounting disaster--West Coast distributer used 3M 4200 or 52OO adhesive which took forever to set and the edges were wavy (I assisted). I bought a second panel (Solbian bit newer version with clearer top finish) and did myself with a better job in mid 2013 (Palmer Energy Systems in Florida let me borrow ladder and tools; but it unfortunately it caught on fire a month later--two hot spots).

Note: Palmer Energy Systems installed a Morningstar 300 watt SureSine inverter for me. He 's an excellent place to get solar done as he wants you to see everything he does (and you can assist).

Bruce Schwab (OceanPlanetEnergy) went to bat for me with Solbian and replaced and reinstalled (I assisted) two new Solbian panels (so they'd match as Solbian had changed top coating). So far, so good other than a bit of haziness and lower output. 3M Dual Lock allows for a nice installation. (Recommend Bruce Schwab highly. Marine folks might like to know he has some around the world solo sailing records. He also carries some new Group 31 batteries which are better than typical AGM batteries.)

A little bit of shade from bird droppings or leaves can cause hot spots on the semiflexible panel--enough to ignite. Also, overflexed or poor wiring can also cause.hot spots. For glass panels, not that big.an issue as glass can handle. Semiflexible panels can't take the hot spots.

Chinese knock-off semiflexible panels may claim to use the same high efficient Sunpower cells, but the quality of the solar cells and the quality of the mounting layers may not be as high as the Solbians.

Delamination and haziness are often issues with semiflexible panels. But, need to determine which panels make sense (Chinese ones are so much cheaper, maybe treat as semi-disposable).

OneManVan is going the portable panel route to reduce the level of weatherization of the semiflexible panels. He had a bit more wear and tear effects on his two semiflexible non-Solbian panels than my current set, even though he did add polycarbonate underlayment for stiffness and cooling.

 

[OldWest]

You are obviously handy enough to do your own solar installation.

There are enough real solar experts like OneManVan and others on this subforum who can give you enough tips to DIY.

Some Colorado folks looked like they may have.coordinated some solar installs.

If you need hands-on assistance, Palmer Energy Systems in Florida is highly recommended.

Westyfests are also a good place to coordinate.

My favorite solar site is handybobsolar.com. He may still assist on installations.

 

[Kiltym]

Yes, familiar with Bruce and Solbian. Good stuff, but pretty pricey as you know.

I looked to find onemanvan's posts about what he did regarding the converter, but have been unsuccessful. Maybe there aren't any...? Or do you know where his info might have been posted?


The other reasoning with the dc-dc charger is that two I posted include built in MPPT solar controller. So when solar is added, I can use the same dc-dc charger already in place. Certainly will add solar in the future, but I still feel there is advantage to adding the dc-dc charger if I can get the converter to supply power also. And it would mean better charging all around, but maybe overkill as you are implying.

 

[Kiltym]

"For bigger drains or discharges, driving around with the engine alternator would provide the big amps charging the batteries like."

My hang up is the voltage from the alternator is not high enough to charge the batteries well. I think your solar is doing more then you think when/if you were to drain your batteries down 50%. But based on your usage, this never happens, and in turn, your solar is 100% adequate for your needs and you don't really ever rely on alternate charging sources.

 

[OldWest]

Try looking for what OneManVan did on the Yahoo Westfalia group (I have no luck there ever since they changed the format years ago.). As I remember it, he provided detailed diagrams and parts info.

I searched this subforum for the info and could not find.

 

[OldWest]

DC-DC is not overkill if it works for your situation. Different folks, different needs, etc.

Some folks love the gel batteries (and last time I checked years ago, Westfalia was still using gel batteries in the new James Cooks) while others prefer AGM batteries.

I was gung-ho on lithiums for their light weight and depth of discharge, but balked at their high price. Then I learned from OneManVan and others that lithiums are not a drop-in and ignore so lithiums are off my list for now as too many complications.

I and many others thought the Fantastic Fan replacement for the bathroom vent was the cat's meow. But some folks in the Pacific Northwest didn't seem to need or want one.

The rear seat mod for folding down the back portion is my favorite mod thanks to an East Coast Westy owner. But not recommended for folks who seat passengers back there.

Solar does not seem as popular in the Paciific Northwest (let there be light). Probably not cost-effective.

And for many Westy owners who don't boondock extensively or who drive a lot or plug-in when using their Westies, solar doesn't make sense.

Solo travellers find the black tank big enough, but families wanted bigger black tank. I like Foster's composting toilet for more freedom from dump stations.

Several folks have done the VanCompass lift and I'm debating whether worthwhile. TNeuer did.the 4x4 conversion (he does NOT recommend the company).

 

[OldWest]

Another option add-on.

There is a high-idle option which can be retrofitted. Believe Ted and several others may have done.

The high-idle option may be an alternative to the generator (compare to see which is louder).when using the DC-DC charger.

Also, for folks who use the Sprinter air-conditioner and/or the Kerstner rooftop unit.

 

[onemanvan]

Here are some links to what I posted on the Yahoo forum back in 2012.

https://groups.yahoo.com/neo/groups/sprinter_westfalia/conversations/messages/9958

https://groups.yahoo.com/neo/groups/sprinter_westfalia/conversations/messages/13675

That was five years ago - since then I've realized that some of the modifications I made turned out to be less effective/useful than I'd hoped for... Chalk it up to the high price of education

If I had it all to do over again - knowing what I know now - I would probably run a 6~10 gauge wire from the Mean-Well output directly to the house batteries. There is a fair amount of line loss between the converter output and the house batteries when you take the long way around - at charge currents of around 30 amps I'm seeing a .5~.7 volt drop! And as CptnAl pointed out - a disconnect switch and a Schottky diode would probably be a good idea. Maybe something like this:

http://www.mouser.com/ProductDetail...s/VS-100BGQ015/?qs=9h5moqLwYqRXhPAl60%2bFWQ==

Be forewarned that even a Schottky diode induces a voltage drop of about .4 volts - which is almost as bad as taking the long way around!

If you crank up the output voltage of the Mean-Well converter to 14.4 then you might not even need the DC to DC converter for a bulk charge.

Leveraging the Mean-Well converters to perform a bulk charge does seem logical on the surface - but there are a few caveats...

To get the most bang for your buck - ie: minimize generator run time whilst maximizing current into battery.

1) It helps to let the house bank voltage drop down to 12.4 or less ( ie: 4 bars or less on central electronic console ). Reason being the acceptance rate of most lead acid batteries is inversely proportional to state of charge. IE the deader it is the thirstier it is...

2) It also helps to crank up the output voltage of the Mean-Well converters. Reason being the acceptance rate is directly proportional to the charge voltage. IE: the higher the voltage the harder you're pushing juice into the battery. The fuller the battery gets the harder you have to push to cram electrons back into their cage

If you can do both of these things you might be able to stuff 30 ah into your house batteries with 1 hour of generator run time. However - this will only get you from about 50% state of charge up to 75% state of charge. Beyond 75% the acceptance rate is so low that it's not really not worth it to keep running the generator.

Herein lie the most compelling arguments in favor of lithium over lead acid! Lithium's will take whatever you have to offer - whether it be 10 amps or 100 amps - from 0% state of charge right up to 100% at a voltage of 13.7~14.1 -

But of course Lithium's have there own caveats - that's another story

John...

 

[Graphite Dave]

Another choice that works well is to power a pure sine inverter with the vehicle 12 volt system. Use the inverter output to power your 3 stage shore power charger while you drive. The house battery is always charged with the correct 3 stage charge profile. This is actually my backup method of charging if weather forces its use.

My primary charging system is a single 300 watt high voltage panel with a Morningstar Sunsaver 15 amp MPPT solar controller. Solar provides more than enough power for my application in my climate. The original 8D Lifeline 255 amp-hr in the sold Sprinter is still in operation after 8 years. Built the same system for the current Transit conversion.

 

[Kiltym]

Thanks for the links and the "reflections" on what you did.

One thing I note is that it appears that you had to circumvent the relay under the seat to get the power to flow to the house bank. I suppose the relay is only engaged by the engine running, and in turn, power will only flow to the house back if the engine is on.

The dc-dc chargers (at least the CTEK one) will perform this function. So I think I would need to permanently circumvent the relay under the seat (no need for a manual switch), and then let the dc-dc charger take care of connecting, and disconnecting the two banks as needed. Not a big deal, but something I did miss in my original thinking.

Being able to adjust the voltage on the main converter unit is good, as 13.25 is not quite high enough for the dc-dc chargers. If that can be raised to 13.8 or so, that would be better. Will have to try it.

Your mention of the voltage drop is a bit surprising to be honest. The cable running to the start battery should be handling 30A without much loss. But I guess there are some connections and relays/switches also involved before the house bank is reached. I would think the dc-dc charger again would help this problem however since it would raise the voltage back up to 14.4 (or whatever was needed).

And, the relay you added to prevent running the A/C on the start battery is also a good idea.

So, I think this will all work, just have to put together the shopping list together.

I think the main decision point for me is driving the van and running the generator would result in the same charge. So having the option to charge from the generator, for $10 worth of parts, seems like a nice add-on.

Your point of just running a cable from the converter to the house bank has some positives as well as it avoids any type of switch/relay installed with the converter, just add the wire, and your done. Not sure why the diode would be necessary, unless the converter is going to "consume" DC power and cause harm somewhere.

Decisions decisions....

 

[onemanvan]

Ideally there would be an isolation switch inline between the converter output and house battery to be switched on when performing a bulk charge via the converter. The diode could serve as a 'failsafe' in case you forget to turn the switch off after the bulk charge was finished. When the roof A/C is powered by the converter you don't want the house battery in that circuit as a parallel current source. It's difficult to advise as I don't know if you still have the Kissling relay in circuit or if you substituted or are planning to substitute the Kissling with a battery switch.

The majority of the .5~.7 volt drop on my Westy occurs between K52 and the house battery - it appears to be a 6~8 gauge wire - couldn't be more than 10 feet - shouldn't be inducing that much of a voltage drop - it's a puzzle Iv'e yet to figure out. Might need to trace the Mean-Well converter ground.

 

[OldWest]

Well, my head is spinning so have not gone through these threads which might be interesting.

https://sprinter-source.com/forum/showthread.php?t=44803&highlight=Sterling+charger

https://sprinter-source.com/forum/showthread.php?t=38670&highlight=Sterling+charger

https://sprinter-source.com/forum/showthread.php?t=54677&highlight=Sterling+charger

https://sprinter-source.com/forum/showthread.php?t=7333&highlight=Sterling+charger
https://sprinter-source.com/forum/showthread.php?t=51923&highlight=Sterling+charger

https://sprinter-source.com/forum/showthread.php?t=25621&highlight=Sterling+charger