Second (ie:Dual) Alternators?

[Jsneeb]

Yeah, advantage of the second alternator is that you can run it at something other than 12V. 24 or 48V should be reasonable so long as it's not exceeding the rated voltage of the internal rectifiers. And if it is bypass them and run external rectifiers and generate whatever voltage you want.

Also running the alternator at close to it's max output all the time to charge batteries will greatly diminish the life of the alternator. Two alternators will last far longer and not jeproadize the reliabable operation of your bus.

I would not pull more than 40 A continually for charging batteries from the primary alternator.
You can do this easily with a buck/boost module equiped with both CC and CV modes. Probably 15 bucks on ebay.

[Jsneeb]

Originally Posted by Asetechrail

So you’re going to run 9 12 volt batteries wired all in parallel? That should prove interesting...post a diagram of how you plan to wire them up.

I sense skepticism also, but I'm unsure why.

I have no idea what you would need 16KW of storage power for, but if you want to add 900lb of batteries to your bus and wire them in parallel you certainly can.

Better have some 4/0 AWG cable or bigger though.

The cost of all those batteries would so far exceed the cost of a generator and fuel if I had such huge power demands a generator and 1/4 of the batteries would be a no-brainer financially.

[FamilyCircus]

In my case I have a 1350 ah battery bank. To charge it you need a minimum of 10% or 135 amps to charge it. An alternator is a battery maintainer so running it at max is not what they are designed to do so if we think of only running at 50% of the alternators max output to maintain this battery bank that puts me at needing an alternator output of 270 amps.

this is only to have the option of charging or topping off the batteries in inclement weather or as a back up if something happens to the panels or charge controllers.

Im a fan of redundancies. I also carry a 4kw gas generator and 1950 watts of solar with 3 mppt controllers.

I work with the repair of commercial RV's and those things have only one system of any kind and when it dies those half million dollar things are dead in the proverbial water.

I have redundant water storage, power production, and heat.

[bapos]

Originally Posted by SolomonEagle

Here is an idea.. Put an alternator on you driveline to reclaim energy when going down hill to charge your batteries instead of turning it to heat through yr brakes. Make the system engage with your brake lights so that they work in conjunction.. alternator coming on first to soak up the initial load and any "light braking" that you might need. Just another radical idea from a guy who lives In a bus!)

After re reading this although I think its a grand idea but it sounds like a crap ton of fab work and I am not overly fond of mounting electrical in a possible wet environment that produces 320 amps ... even dc...... I think I will stick with what works of putting it on a mount where an ac compressor will go. I think I read that it takes about 4 hp to run one of the alternators I plan to run. I think my 466e wont worry too much about a 4hp loss.

[bapos]

Originally Posted by SolomonEagle

Still though, what is the benefit of doing that..other than having a cool/tech charging system? You could charge your "house" battery bank using the same alternator by using an isolator and save yourself some money and custom work.i don't think you need a dedicated alternator for this application.

Do I need it .... probably not. My plan is to use a 15kw diesel genny most of the time. I will back it up with a small solar set up and back up that charging with this secondary alt. Kind of over kill but how many times in life have you needed something and not have it..... so I rather have it and not need it than the other way around.

If you have ever been around any kind of Navy engineering type... we have a primary... secondary and a back up to those whenever possible.

I will have a fairly powerful car stereo system in my bus so the last thing you want is to run out of power.

[TheHubbardBus]

Originally Posted by Jsneeb

I sense skepticism also, but I'm unsure why.

Because 9 parallel strings of 12V batteries is an absolutely terrible idea unless your goal is to see how fast you can kill your batteries, start a fire, or both.

https://www.solarpaneltalk.com/forum...es-in-parallel

https://forum.solar-electric.com/dis...series-strings

https://www.solarpaneltalk.com/forum/off-grid-solar/12v-solar-for-rv-or-camping-etc/21436-12-volt-design-and-safety-considerations/

[PNW_Steve]

Originally Posted by TheHubbardBus

Because 9 parallel strings of 12V batteries is an absolutely terrible idea unless your goal is to see how fast you can kill your batteries, start a fire, or both.

https://www.solarpaneltalk.com/forum...es-in-parallel

https://forum.solar-electric.com/dis...series-strings

https://www.solarpaneltalk.com/forum/off-grid-solar/12v-solar-for-rv-or-camping-etc/21436-12-volt-design-and-safety-considerations/

+1

Good advice.

[PatrickBaptist]

I've mad a trailer out of a RV chassis, I am working on plans to put an alt on the rear end of the trailer since it is a drive axle that isn't doing anything.
Figure it would work good to reclaim some power from nothing. I realize that doesn't do anything when your not moving but I've got all kinds of parts laying around so there isn't going to be really any cost for me to do it other than the cost of running the welder.
It will be dandy though if the bus alt dies while road tripping so I have plenty of time to drive where I need to get to change out the bus alt.
I realize I would be one of the very few with this option but I couldn't help but throw that idea out there.

[FamilyCircus]

I dont pretend to be an engineer so I have to ask regarding my proposed battery bank.

Is it ok to run 3 of the 12v batteries in parallel then join 3 groups of these parallel banks together. As opposed to a long 9 battery string all in parallel.

I dont know so I am asking those that know.

[Shamoke]

Originally Posted by bapos

If you have ever been around any kind of Navy engineering type... we have a primary... secondary and a back up to those whenever possible.

Yea, primary is the chief responsible, secondary is the poor E3 he had do it and the backup is any E2 standing close by the looks like he could take the blame.

[RolesvilleMarina]

Anyone know what the typical output is on a stock alternator on most buses

I have a T444E for example.

was just curious

[Versatile]

Mine is 150 amp.

[EastCoastCB]

Originally Posted by RolesvilleMarina

Anyone know what the typical output is on a stock alternator on most buses

I have a T444E for example.

was just curious

IDk if they were ever standardized. A couple of my buses had the amperage specified by the buyer on the order sheet. My first bus was top of the line with deluxe everything, but they'd spec'd a 95 amp alternator.

[cadillackid]

ive not seen a standard.. from what ive seen the amount of equipment kind of dictated it.. factory A/C busses seem to have bigger alternators than non.. ive seen busses with tons of heaters have bigger Alternators..



not to mention that the likeliehood of it being original is next to none so a achool mechanic might replace with aftermarket.. for example bosch makes a small form factor 200 amp that is smaller than the leese neville 160 on my red bus..

[RolesvilleMarina]

Well my bus doesn't get as hot as I expected it too whilst driving.

Up to west VA it was pretty bad, outside and at least 32 outside but as long as moving we weren't "dying" at all as I expected. The bus came with two fans pre-mounted. One blows over the drivers face, and the other ironically is where I put M's seat. Which is weird because the bus was not designed to have a seat there in the stairs, but now her fan is also perfectly positioned. They look like little retro house fans from the 60's which is actually a bonus.

We left all the windows down, and with the screens had a decent breeze. The curtains need a redesign of the stowing as they flapped around like a wavy arm guy back there.

1st thing going in soon is the Onan 4k genny now that the mount/hitch is complete. It runs on petrol so I will have to figure out a tank for it, as well as fab up the exhaust still. But when that is finished we can give her a test run next year driving with the roofshaker on.


Ideally I want to put in a sanden compressor, as I can do air con, and run engine driven.

HOWEVER, I do have a little 2 hp electric motor, so I wonder would it be better to run a 2nd alternator and this way I can mount the sanden anywhere, and just belt it to the leccy motor. This way engine could be off say in a parking lot for a store run, but the leccy motor (through) the inverter would run the sanden for a bit off the leisure batteries.

Again it's all just talking out loud. The Sanden doesn't need a lot of HP to spin her up, 2-3 is sufficient i imagine as long as RPM's are where they need to be which can be accomplished by pulley variations.

and just to be clear I am in no way expecting to run any kind of air con off batteries alone at all.. It continually comes up in the sailing forums when dreamers think they can run 15k all day off a harbor freight solar panel and a battery.

I am specifically looking as to whether one or the other may be better whilst the engine is running... when parked we are on the shore power, or once and awhile the onan

If I went with a 2nd alternator then even on shore power I could run the Sanden for additional cooling as parked?

[Booyah45828]

IMO, it's best is to have 2 seperate air con systems. One for driving, and one while parked. If you already have the rooftop unit, and it provides adequate comfort while parked, then install dash air and be comfortable while driving.

I just don't think a rooftop or minisplit unit will provide enough btu's to cool while driving.

Some do get it to work. I've seen native's system and it works for them. I wouldn't be satisfied with it though, so I'll likely install dash air on mine.

[RolesvilleMarina]

Originally Posted by Booyah45828

IMO, it's best is to have 2 seperate air con systems. One for driving, and one while parked. If you already have the rooftop unit, and it provides adequate comfort while parked, then install dash air and be comfortable while driving.

I just don't think a rooftop or minisplit unit will provide enough btu's to cool while driving.

Some do get it to work. I've seen native's system and it works for them. I wouldn't be satisfied with it though, so I'll likely install dash air on mine.

Correct... what I am getting at is should I run the dash air con with the engine spinning the compressor, OR use the 2nd alternator as a 200amp power source which will easily run the same dash air con, the difference only being a leccy motor spinning the sanden

whichever way I spin the sanden I still need to run the condenser under the bus so I will have to also use leccy fans for that

the advantage is while plugged in I can run the dash air con with the engine off in case I need "extra" cooling for some reason

[cadillackid]

a sanden will "spin" with a 2 horsepower motor. but you need to look at the output curve to see what 2 HP will actually get you in BTU output.. prob not much more than a rooftop or window unit or minisplit .. thats assuming you can turn that 2 HP motor under load with an alternator making 12 volts converting it to whatever that motor needs..



and WHY? unless you plan to use the dash air on a system for when you are parked its much easier to mount the sanden on the engine and spin it the way its meant to spin.. if you are tried to build a dual system where it can be road A/C and parked A/C then it makes more sense to get creative..



here is the link to the performance curve of the SD7 enhanced.. now I push mine hard and they take all i give it.. however I also dont spin it slower than minimum.. you can see what you need to do to get decent output..



on my diesel engines im over-driving my compressors pretty good. the curve shows up to 4000 RPM, sanden gave me a continuous operation RPM max of 6000 for all of the SD7 series.. however they roll off a bit in performance increases above 4000 so they recommended 4000 as the "sweet spot highway cruise" for a long haul bus.. they encouraged over-driving more for city-driven vehicles like school busses ..


Ive worked with a lot of different compressors over the years and compared efficiencies. and 2 have stood out..



the SD7. (the enhanced was released in the mid 00s and only thing I use now)
the GMC frigidaire A6. yesah the one thats likely on your classic GM and some fords.. they actually are used in bus / coach applications.. or were.. ive seen them as recently as on 5.9 cummins Bluebird and thomas busses..


do your math first.. engineer your A/C. dont just throw parts together and hope it blows cold

[Shamoke]

You guys are throwing around a lot of names and terms I am unfamiliar with, names like sanden and leccy are nothing I have ever heard before.

I have a 2000 Blue Bird All American front engine cummins 5.9, what are the options of adding dash a/c to this bus? I had planned on using a 1 ton mini split, (12k BTU), as the main cooling for parking and driving and using a second alternator to charge the batteries and provide power to the a/c and refrigerator while driving. This would be in conjunction to solar panels on the roof charging the house batteries and running the listed equipment when it's sunny out.

I am seeing posts both for and against this method but now I run across this thread about adding an engine driven a/c and you have me intrigued with this idea. Can anyone provide any links to this add on equipment?

[cadillackid]

Sanden is a manufacturer of common A/C compressors.. Most of our busses with engine A/C use sanden or a knockoff brand that fits in like a sanden..



Leccy is a term for an electric motor..



there are many options for adding engine driven A/C from mild to wild.. read that as cheaper to pricey..



you can certainly run yoiur minisplit while driving and if you mount it above your seat and partition off right behimd your seat you'll stay OK cool in all but the hottest weather.. but only another front seat passenger might benefit.. and with a front engine bus youd have to really insulate that doghouse extremely well..



the cheapest route is to find someone yanking out their engine driven A/C and procur the parts.. many people give them away if they pull em out. thats the cheapest way.. that would net you a system capable of cooling most of a well insulated bus or easily half of a stock bus really well.. youll have a ceiling evaporator inside and a skirt mount condensor outside.. you can relocate the ceiling unit into cabinetrey.. put it down low and duct it etc.. get creative..



if the bus yuo remnover the A/C from was the same engine you can snag the compressor and engine brackets from it.. if not, new brackets for a 5.9 24 valve are easy to find and a couple hundred bucks..


I did custom ducted dash air in my DEV bus. as i wanted refrigerated defrost (like you have in a car). so I gutted my driver heater box and fitted a high capacity heat / cool unit.. the advantage of refrigerated defrost is being able to dehumidify the air and not fog the glass in rainy weather.. that system was more costly as i used mainly new sourced parts and had a lot of custom work I did to make it all work.. (theres also a mid-ship heat / cool unit as well)... 80% plus of my time spent in my bus is driving so engine driven is what I needed.. I dont camp in it. but do sit and work in it sometimes.. or eat. (since covid).. so i just leave it run for those times..