A Different Perspective on Automotive Alternator Direct DC Charging

[OFFGriddnPat]

Hi fellas-

My first post as I just found the forum. Lots of like minded folks here I see. Looks like a pretty cool place.

I've read through a few of the threads here on DC Alternator charging. I think some of the theories here may be over complicating the setup. I use a much simpler and less costly way to build DC Alternator direct to battery bank charging systems, and have for many years.

DC amps are amps, just like watts are watts. Why lock yourself into a voltage by using a regulator?  It doesn't matter if you have your inverter configured with batteries wired for 12VAC, 24VAC, or 48VAC if you drop the regulator and manually set your system performance by pulley ratio, throttle for motor rpm/load, and field load for your needs. This way you can use a (non regulated) alternator and engine, and adjust it for peak efficiency.

We've been off grid and living remotely for over 12 years. I have 2 systems- one trace SW400024v inverter w/12 L16's in the house with 1kw of PV panels, and one Outback 3500 watt inverter in 24VAC as well w/12 L16's in the shop. All systems are monitored with a Trimetric.

I have a fully equipped machine shop that I built and outfitted with manual machines- (3) lathes and Bridgeport mill with all the supporting equipment and bench power tools, as well as 2 CNC Hardinge lathes and a CNC Cat40 mill. I manufacture and market my own product designs.

The house system runs everything in the house including dishwasher, clothes washer, flat screen TV computers, microwave, and every kitchen appliance known to woman. It also runs all of my manual machines in the shop. The shop Outback system is dedicated specifically for my CNC machines.

I rely on stock, Delco alternators with no internal regulator, (no external regulator either...NONE) for both backup and continuos direct to battery bank DC charging and have for over 12 years.  I simply wire up a HEAVY variable load resistor to the field with on/off switch, amp meter, and heavy DC positive main inline fuse. This way you can fine tune your sheave pulley ratio to turn your alt at the best speed for cooling, your engine throttle for optimum fuel consumption and load/speed for wear and longevity, and peak optimum amp draw load from your alt to give you the max amps you need and maximum life from your alternator.

I size these components to the old Delco. I've gotten as long as 8 years out of a single alt. I've ran different engines and horspowers over the years, and will be machining some aluminum serpentine belt sheave pulleys for these setups, and start doing tests for fuel consumption, amp output and engine/alt longevity with rpm ratio tests, etc. to get the absolute optimum results down on paper, beyond my own feel and experience of what works well. 

For me direct to DC has been a cost effective, inexpensive, and easy off grid generator to keep running. Something that is crucial and extremely important for living in the outback, not to mention running a business that relies on machines.

Another observation when running machines with a large AC generator with inverter charging... any startup surge really is noticeable, even running my big 10KW ac generator and Trace SW4000 inverter. Running the DC alternator direct to the battery bank can handle pure surge power effortlessly.

I never saw the need to run a big AC generators, that start out with DC, then convert back to AC to be sent to your system inverter, that intern converts it back to DC for the battery bank.  I believe it's harder on the inverter as due to heat as well. I've gotten a solid 10 years out of my first Trojan L16s, and I'm still using that set in the shop.

If you have to have an AC source directly off a generator then that's the way to go, but if you can run a battery bank and inverter, nothing beats direct DC battery bank charging IMO, and nothing beats the cost of running DC generators continuously day in and day out for years on end.

[LowGear]

The proof is in the pudding.

Casey

[Horsepoor]

Pat,

Can you post some photos on your setup?

[mobile_bob]

OGPat:

always nice to see new folks come on board, welcome.

now to the meat and taters of the topic...

you realize of course that your delco alternator starts out making AC current and uses those rectifiers to make the power DC for battery charging, basically the same thing that some folks do by rectifying their ST heads AC current to DC for battery charging.

all generators are alternators, every one of them, they all produce AC current and either use diodes (rectifiers to convert to DC) or,
they use commutators to mechanically rectify/convert to DC the AC current generated.

while you have a system that works for you, it would appear you either have a good match or you like to baby sit the charging regime?

no system that incorporates a single reostat as the soul control handle in lieu of a proper regulator can ever come close to matching the efficiency of a purpose built regulator in efficiency, lifespan, or fuel consumption. this is not to say that such a system has no place in offgrid
because certainly it does, its just not the best solution for the vast majority of folks, and certainly has no place in a multifuction cogenerator save for a back up/fail safe/if all else fails patch to get you through till parts can be procured.

the most efficient charging regime for a flooded lead acid battery and most AGM types is the 50/80 regime, in order to optimize a charging system to fully take advantage of the regime one must have in most cases at least a couple hundred amps of charging capability. such high current systems should never be controlled by a simple reostat system unless the operator is available to closely monitor the charging from start to finish, and is able to temperature compensate the charge rate. failing to be able to do at least those two things is inviting a severely over charged battery, overheating, and shortened lifespans, or worse.

you don't mention the amount of time you run your system or what frequency you do so?  do you recharge daily? how many hours per run? how many amps? what voltage? what set points for what range of ambient temperatures do you use? what equalization schedule and voltage?

i suspect you run something less than a hundred amp unit, or rather something less than about half its max output?  and you run a significant amount of hours for each charge? probably twice what you would have to run should you choose to use one of several 3 stage controllers that have temp compensation, alternator temp sensing, and a plethora of other nice things like an amp manager to allow you to tailor the alternators output to the available power driving it.

some of us have other thing running off the engine such as refer compressors, AC 120/240, air compressors, and all manner of other stuff
where the loads are very variable and are switched in and out at random, all of which would make the use of anything other than a 3stage
controller an exercise in futility.

don't get me wrong here, i am not saying your system is without merit, quite the contrary really, every offgrid installation should have a simple system that is reostat controlled, however...

it should not be the main system for anything other than either a very small infrequently used system, or one that is single purpose and where the owner has the time and inclination to be the "regulator" (read that babysitter), or in exceedingly rare installations where the ambient temperature is very close to 77 degree's F and everything else is very well matched.

fwiw

bob g

[OFFGriddnPat]

I don't know where to begin with what you write accept those are very well crafted words, but for the most part are baseless in my experience, and for my requirements.

I've charged this way almost daily for over 12 years now. My first 12 bank of L16's lasted 10 years before a noticeable slip, and without optimum care I might add, and are still serving duty between a running DC charger and my CNC shop machines.

Yes, I have run over 100 amps (24v amps) and can and do if I wish to, and no there is no baby sitting involved. I do let my solar panels float charge the remaining top end of the system on sunny days. Cloudy days why worry about it?  It's not that critical. Far less than the conventional wisdom would have you believe. I do only fuel up for as much run time that's needed if I have to leave, or I get busy.

Now I do agree that if you are running an ST gen head with compressor in addition to a DC alt then you would want to automate your load with a regulator, so you could balance out the loads on your engine for your systems needs, but I'm just talking about an inexpensive, dependable, efficient, long lasting setup that can be repaired for peanuts and can be "matched", as you mentioned the word and it's a good term to describe the right sized hp engine rpms and load placed on your alt. With an engine that has enough Hp and a drive pulley that can turn your alt fast enough, so it runs cool enough, your matching is a piece of cake with a heavy duty adjustable load in the field. No need for a fancy, expensive, regulator. Or a costly alt wired to a specific voltage.

I know what works proven over time and my pocketbook, by doing it.  I feel for many of the posters I read on the forum here and elsewhere on the net where guys just want to build a DC generator inexpensively, and the gammit of info they get is kinda off the mark. They wind up spending money on expensive alts and regulators that stall out their rigs, or have to be revved up to excite.

My eyes are a little blurry now from resting and watching movies all day here, but I'll get into examples and specifics, and be happy to answer questions.  I don't proclaim to be an expert on the subject, and certainly my goal is not to show disrespect, flame, or demean anyone's opinions.

If a guy can show me how I can save money by running a different DC rig for my needs, I'm all ears and you certainly have my attention.

[Lloyd]

Off-G-P,

Efficiency is a through-put concept...not just throwing some current at bats. bc you have only intimated to what your actual system is... it's really hard to understand what you think efficiency is.

I have better then a hundred bat banks and alts with Balmar Controllers installed, at least a dozen that are exceeding 10 years. While the Balmar controller is the most expensive controller I know in the market place...I think it's cheap at any price. I don't know of one failure to a Balmar Controller...certainly not in any of the units that I have installed. My own Balmar Controllers 2 of which are 10 years old this year are working happily.

So the math works out like this $270.00 purchase, amortized over 10 years is a mere $27.00 dollars a year. $27.00 dollars divided by 365 and then again by 24 works out to $0.003 cents per hr, I pay my baby sitter for the bat bank. Now that is down right cheap.

Now include the fact the controller monitors the bat, and alt temp, and adjust output accordingly so 1, I don't burn up an alt, and 2, I don't burn up a bank, finally 3, I pour as much current into the bank, as they can take, with the least amount of fuel, and wear and tear on both the alt and the engine driving it...... and the controller is probably as close to free as free gets.

Do you cycle charge?   ...or do you just let the alt run non-stop.... It's been proven time and again that a cycle charge regime is the most efficient way to run a bank, whether it's powering an inverter or just straight dc loads, or the combination of both.

Fuel and engine wear are the biggest investment in the scope of an off-grid investment, that includes the same, when you measure through-put; end to end.

I know it's not fair 2 against one but...you are up against more odds then that...when talking total system efficiency...
Glad to have you aboard..let the vetting process begin...it's good for us all.

Lloyd



Lloyd

[mobile_bob]

a few more things to consider

1. i would never use a fuse on the alternator output, reason being if there was ever a problem that caused the fuse to open the alternator would produce a very high voltage spike and there goes your rectifier bank

2. modern alternators use what is referred to as "avalanche" diodes for the rectifiers, what this means is a 12 volt unit will limit to about 30 volts operation before they clamp, any more voltage and operation over a few seconds will lead to rectifier failure, this precludes their use on anything over a 24volt system and even at 24 volts one will need to assure large enough cables not to have much over a half volt of drop you you will go over the avalanche voltage while charging a 24 volt bank with a 12 volt alternator. of course these diodes can be replaced or one can use one of the older models and get away from an avalanche type diode.  just something for others to be aware of and adds cost to the project.

3. while delco alternators are certainly widely available and about as inexpensive as any, they are also some of the most difficult to repair in my opinion, most especially the more modern units that use welded lead construction.  yes you can solder those connections instead of welding, however the reliability suffers at higher outputs.

4. a properly setup balmar, xantrex (which is made by balmar)., amplepower, hehr, sterling et. al. can and will pay for itself in fuel savings in very short order, as Lloyd reports they are very robust and their failure rate is quite low.

5.  efficiency is a measure of btu's input vs btu's output, and for the most part construction cost is not a factor. generally speaking the single largest factor in an engine driven battery charger is the cost of fuel, anything that reduces fuel consumption even a little bit will quickly not only pay for itself but pay dividends for the life of the system. a good controller will always allow for the use of less fuel than a similar system controlled with a simple reostat.

in closing i two would like to know more about your system

how large is your battery bank, how many amp/hrs?

where are the batteries stored?  underground so that the ambient temps are stable? or
in a climate controlled room? or in a room with  widely fluctuating temperatures over the course of a year?

what alternator are you using?

what engine are you driving it with?

how often do you recharge?

how many hours per day do you charge?

at what voltage do you charge? and

how do you maintain this voltage as the battery nears the point of gassing? (about 80% SOC)

you understand of course what you report doing is nothing new, quite the contrary it was what was used and abandoned by
everyone over a hundred years ago before the advent of mechanical regulators came on the scene.  the early mechanical regulators
were in reality a simple reostat that used some clever coils, gearing and other stuff to adjust the reostat as the battery charged.
it was quickly realized that running without some form of regulator was the soul cause of many a failed battery bank, by failed i mean
"murdered" batteries.

so lets hear more about your system and experiences operating it.

edit:

i went back and reread part of your original post,
it would appear you have a battery bank that is about 800amp hours at 24 volt nominal?

if this is the case, then your ability to max out at about 100 amps, and you limit the run time so that you then top off with solar panels
and have enough load to clamp the excess are the reasons why you are getting away with a simple reostat controlled system.

an 800amp/hr system could readily accept twice what you are able to deliver (up until gassing gets excessive, then you would have to reduce the output) and in doing so would cut your charge time roughly in half, which in turn would reduce your fuel consumption by roughly half as well.  however if you had a system capable of putting out 200 plus amps and chose to control it with a reostat you would either be forced to babysit if yourself or have batteries that boiled dry and suffered an early death.

more later

bob g

[OFFGriddnPat]

Maybe we are talking apples and oranges here folks.

I'm not saying your systems will not work, but you express all of your thoughts on how mine can't, or won't. I'm here to tell you I do, and it does.

I was told by the "Experts" I could not possibly run industry standard 3 phase industrial metal lathes and mills off grid here with a single phase 120VAC. But I do daily. It was stated by an engineer and physicist that the product I have designed could not work and was "all wrong" for the task yet I did, and have taken a good majority of his business.

Everything is doable and relative. Blanket statements do not always fit.

The system I use is for fast, pure DC amp charging. It is certainly bare bones and simple, and adequate for the task and my needs. No automatic startup and shutdown. No float or "Cycle" charging. And yes "Baby Sitting" if you consider peaking at a Trimetric for a moment and shutting down the gen if you have placed more than enough run time fuel needed "baby sitting". I have never found that to be a burden living off grid.

What my generators do is apply pure amps in DC with your choice of engines, that do pretty darn good on fuel, and use parts and components that are cheap and easily obtainable. Plus the cost allows me to run more than one generator setup in different areas, and have an instant backup rig ready to go should a problem arise, and I don't have the time to stop for the day and trouble shoot a repair issue.

I don't burn up alts.

I don't burn up batteries.

"no system that incorporates a single rheostat as the soul control handle in lieu of a proper regulator can ever come close to matching the efficiency of a purpose built regulator in efficiency, lifespan, or fuel consumption. this is not to say that such a system has no place in offgrid
because certainly it does, its just not the best solution for the vast majority of folks, and certainly has no place in a multifunction cogenerator save for a back up/fail safe/if all else fails patch to get you through till parts can be procured."

Those statements are far to general in their nature. Specially the part about lifespan an no place in a "multifunction cogenerator" off grid situation. It depends on what kind of power needs you're talking about. My system will run a home and a shop. Life span? Years. Parts cost? A few dollars. Down time? Minutes.

"modern alternators use what is referred to as "avalanche" diodes for the rectifiers, what this means is a 12 volt unit will limit to about 30 volts operation before they clamp, any more voltage and operation over a few seconds will lead to rectifier failure, this precludes their use on anything over a 24volt system and even at 24 volts one will need to assure large enough cables not to have much over a half volt of drop you you will go over the avalanche voltage while charging a 24 volt bank with a 12 volt alternator. "

I don't often DC charge past 29 volts or so in my 24v system. I charge up to about 85-90 percent (28-29), then let the panels and inverter do the rest including float. I do charge up and over 29v often but I do use heavy 1/0 copper.  Good tips on the diodes.

"generally speaking the single largest factor in an engine driven battery charger is the cost of fuel, anything that reduces fuel consumption even a little bit will quickly not only pay for itself but pay dividends for the life of the system. a good controller will always allow for the use of less fuel than a similar system controlled with a simple rheostat."

I would agree. If you can show me how I can reduce my fuel consumption and costs, I'm all ears.

"i would never use a fuse on the alternator output, reason being if there was ever a problem that caused the fuse to open the alternator would produce a very high voltage spike and there goes your rectifier bank"

What would you do, risk a possible fire? I run a heavy block 250 amp fuse inline of 1/0 copper cable between the alt + output and the battery +. If you have a problem severe enough to blow that fuse, your rectifier bank is the least of your worries.

I gotta git to work.

[LowGear]

Patrick! 

Lad!  You're speaking against the faith!  Surrender into your warm fuzzy cloak of knowledge and understanding.  Allow your cup to runneth over.  Appreciate the oil upon your head.  I, for one, am with you.

I don't know if you've looked at the work Lloyd does but it puts most brain surgeons in the corner with the pointy hat.  And mobile_bob simply knows his stuff.  Your system works absolutely perfect for you but these guys have seen the result of the brown gui stuff hitting the propeller blade and they're lives have been changed forever.

I wonder how much more it would cost to build their system compared to yours?  Amortize that number over 10 years.  I'm not an hourly guy but I do understand monthly payments.

Casey

[OFFGriddnPat]

OK-

My bare bones DC charger.

Lets start with the least expensive setup:

Engines-

I've ran diesels and I've ran gas. I prefer to have both over the years, and eventually I will have 3 separate generator sheds here, both outfitted with a DC gas powered gen and a DC diesel.  Both ready to run at any given moment.

Right now I'm running Chinese knock of Hondas, and one Jap Honda. Reason is time to dedicate to gens, I don't have much right now, so I can have a Honda ready to go on a moments notice. I've had some good luck with the Chinese, once you get beyond bolts coming loose, and fuel tanks coming apart. If they run well and don't use oil from the start, they hang in there pretty good for the money. Getting 4 years on a 16hp currently. I prefer Jap Hondas but, the cost of the Chinese are going to allow me to conduct comparison tests.

Like I mentioned before, I would like to do some testing with these engines and the Delco alt systems to get a definitive measurement to see what combinations produce the best results. Looks like there will be some great help here for that.  Currently, I have a 6.5 chicom running, a 9hp Jap running, and a 16hp chicom running. I can run the 6.5 or the 16hp on the house system simultaneously.  I run the 9hp Honda for my CNC machines in the shop. I just purchased a 13hp chicom sitting ready for backup and future testing.

A 6.5 is a good inexpensive engine to run for those starting on a budget.

Alternator-

I use the Napa #66287  Delco-Remy 10DN Chinese Knockoff. They come with a 3 year full replacement warranty for $36.95. They far exceed performance and quality of any of the over the counter Mexican rebuilds. Rated at 63 amps I believe. As long as I keep them under 55 amps (24volt system) they last for a very long time. Many years at 40 amps.

Rheostat-

I use an Ohmite RKS16R variable. Once in awhile the contactor will burn and loose it's contact, and actually this is the only weak point of the unit. It's only happened one time.  I machined an adjustable clamp with a wire lug and removed their contactor. Once you find where you need to set it for your system, you never have to move it anyway. There's nothing else left to burn or fail. Pure dependable load.

Sheave pulleys and belts-

For now I run v-belts, and stock alt pulleys. 7" drive sheave with SK bushings. Even found an inexpensive steel non bushing pulley adequate for a 6.5 hp engine. I DO not use automotive V-belts. They are junk and wear out quickly. I use AX Industrial belts only.

My favorite belts are serpentine flat belts. More efficient, less drag, longer lasting. I have not had time to machine flat pulleys for these Hondas, but I will as time frees up here.

I run heavy copper cable, with copper lugs to the battery banks. 250amp inline fuse. Systems are monitored by Trimetric.

My goal is to perfect a this type of DC gen for highest performance and lowest costs involved, ease of repairs and maintenance, and parts availability. As soon as time allows, I have two new (2) JKson CS 6/1 Listers to get online, and one new Changfa Style Chinese single. I would like to put together the best DC alt charging system for those and see how well they perform.

Each will go in a Gen shed, along with a Honda DC gas rig. Plumb them into a hot water system for water heating. Glycol and heat exchanger.

Then the final goal is wood gassification as we sit on 15, heavily wooded acres next to the National Forest. I like Victory Gasworks designs.

[OFFGriddnPat]

Casey- I claim to be nobody's guru and respect those that have achieved high enlightenment in their fields. I'm all ears.  I would like to take my system and find out it's peak capabilities and costs and see what can be improved. Look at other systems well. I'm all for finding the best.

Here's as fancy as I get:




That ran 8 years without changing the alt or doing any engine maintenance cept' for oil and filters.

[Lloyd]

Well I do things a little different.

First I size a battery bank based on the true Pukert load as opposed to the 24 hr average load. I go for a three day with out charge bank size, drawn down to 40% DOD/60% SOC or 12.4 for 12v bank and 24.8 for a 24v bank

Next I charge at 30-40 % of the amp hr capacity of the bank, during bulk charge. I use a temp compensated regulator, which maintains cell charge voltage. Ideally a bat should be charged at 77f, a bat can charge all the way to 120f as long as the voltage is tightly regulated, under temp management.

A bat bank can take this kind of charge amperage all the way through the bulk cycle as long as temp compensation and tight voltage management is controlled.

Pat, 12 L-16s in a 24v bank would mean 1110 amp hr bank if they're 375's or a 990 amp hr bank if they're 330's. So doing the math I would size the alts for max efficiency as follows 330 amp 24v, and respectively 297 amp 24v, or as close as I can get.

Your little  63 amp unit cold rated likely only puts out 40 amps hot, based on my experience, and that's pushing it to it's limit. That means I can charge a 1110 amp hr bank discharged 40%, about 4 times faster using 1/4 the fuel as your 63 amp unit

I'll just bet that your installation instructions that come with that alt state that if the bat voltage is below 24.6v to charge up the bats with a shore charger before running the alt. These alternators were never designed to be bat chargers. Their design is to replace the voltage used for cranking the engine, then providing accessory loads, which are usually intermittent. Running any alternator at it's flat out rate will burn em up.

The above is why I would only use a well designed regulator. First to get a bank standing at anything 60% or lower SOC into bulk, you have to slowly feed it current, said in another way you have to ramp up the current to max bulk charge. If you take a bank that is discharged and hit it with high current it will do noting but build heat. A discharged battery has a high resistance initially, but if you ramp up the current slowly it's resistance declines in short order so that it has almost no resistance, and then can take a high current charge the rest of the way through bulk charge.

lloyd

[mobile_bob]

Pat

i think you may have missed my point, or rather more likely i missed getting it related to you effectively.

in an offgrid installation there is always a place for a simple system such as you have been using, it works as you describe
and makes for a nice failsafe/backup unit.

so in that regard you are right in promoting the system, however

my overriding point is simply there are better, more efficient and in the long run more cost effective means to battery charging.

its hard to argue against the marine industry, they have been living offgrid since before there was a grid and have prefected battery
charging to the highest degree attainable outside of perhaps NASA.  (even NASA follows similar charging schemes)

i am still comfortable in stating it likely we could cut your fuel consumption in half, and as Lloyd states perhaps to as much as one quarter
of what you use now.

bob g

[Ronmar]

And your particular circumstances, very large bank, relatively small charging source is why it works for you.  You are basically just a little over a trickle charge for that large a bank...  Reostat to limit the the alternator load so it survives the process at 40-50A and a huge hole to fill.  I think you could save a bunch of fuel(and runtime) with a well controlled larger capacity charge source.  And other than the larger engine to power it, not an especially complex bit of kit to keep the energies within limits...

[OFFGriddnPat]

And your particular circumstances, very large bank, relatively small charging source is why it works for you.  You are basically just a little over a trickle charge for that large a bank... 

Really?  "trickle charge"

Uh at what measure is 40 to 55 amps @24v a trickle?

I see here there's many preconceived notions and opinions on the forum.