LITHIUM BATTERIES FOR DUMMIES!

[newhaul]

Originally Posted by tanglewood

Not sure what you mean by that. I haven't seen a true DC generator on a car since about 1965. All have been alternators since then.


Just for clarity, here's what I mean from my post above.


An "alternator" is the thing on most main engines, typically belt driven, and producing 12VDC or 24VDC at it's output. Internally that is a 3 phase alternating current "alternator" - hence it's name. It produces AC. That AC is then rectified with diodes to produce something sort of like DC, with it's real output wave form hidden by the battery it's connected to. So fundamentally it's an AC device with conversion to DC.


A "generator" is a synchronous device producing AC output at 240/120VAC/60hz, or 230VAC/50hz, or 120VAC/60hz. It directly produces AC output. To get DC to charge a battery, you run it through an AC to CD converter, commonly called a battery charger.


I'm not sure if you are talking about one of the above devices, or a very old actual DC generator. That doesn't have any rectifiers in it, so no losses there, but it will still suffer the big losses which are based on teh square of the current flow through the windings. I think it's efficiency will be fundamentally the same as an automotive alternator. There is a reason the auto industry abandoned them 60 years ago.

I fully understood what you were saying . I am actually talking about an honestly goodness 12 volt generator. https://www.ebay.com/itm/Powermaster...&ul_noapp=true

I also recently was given a "generator" 3700 watts AC power powered by a l100 yanmar air cooled diesel engine .( free because it needed a new injection pump ) so the free generator cost 17.50 .

And they were abandoned for alternators due to price. Alternators are a lot cheaper to procure.

[a64pilot]

Hey they call Detroit Motor City, and motors are electric aren’t they?
Why isn’t it engine city ?

[Dave_S]

Sorry haven't read the whole thread but thought this might be worth following.

https://youtu.be/vY_-Wfyx0_A

It's the Sailing Uma crew changing over to lithium with electric only motor.

[a64pilot]

Newhaul,
Hopefully you haven’t bought that generator, cause I’m pretty sure it’s an alternator made to look like a generator for custom cars etc that want to keep things looking stock, but want an alternators output.

[hzcruiser]

Originally Posted by tanglewood

Generating a lot of power from a DC "alternator" can really be a false economy compared to an AC genset.

Historically, boat solutions often strive to a simple and reliable solution. High voltage AC is not going to charge the 12V batts. In fact, with AC you cannot charge any batt, no matter the voltage.

First off, lots of people cite the need to convert generator AC output to DC, and the associated losses. True, but exactly the same thing happens in a DC alternator. The alternator is a 3 phase AC device with the output rectified to DC. The losses are very similar.

Rectifying AC is very simple and was done for many decades. Inverting DC is much more complicated and hence not as reliable. 40 years ago it was almost impossible, leading to solutions where you drive a motor with the DC you had just in order to spin an alternator to create AC.

But the real killer is the lower operating voltage of the alternator compared to a generator. For the same power output, you need 10x the current from a 24V alternator vs a 240V generator. And the power loss and heat generated by the windings in the devices varies as the square of the current. So 10x the current is 100x the power loss. [...]

Correct.

And isn't it silly how we call the thing that produces DC power an Alternator, and the thing that generates AC power a generator? It's exactly backwards from what they actually are. Of course there is history behind those terms, but amusing none the less.

Not really:

https://top.quora.com/What-is-the-di...nd-a-generator

[newhaul]

Originally Posted by a64pilot

Newhaul,
Hopefully you haven’t bought that generator, cause I’m pretty sure it’s an alternator made to look like a generator for custom cars etc that want to keep things looking stock, but want an alternators output.

you are right I didn't even notice that part but I actually have one that is iirc 70 amp output off of my 1951 Chevy dump truck I had back in the early 1990's.and it is just as an oh Crap unit . It won't even be actually mounted on the engine for space reasons.

Otherwise I may just have to build a pm generator out of an old alternator.

[a64pilot]

Thing is we had 300 amp starter / generators on turbine engines that weren’t really all that big and heavy, considering that they made 300 amps continuously at 28 VDC, so it can be done.
There were also 400 amp SG’s too.

[hzcruiser]

Originally Posted by tanglewood

Not sure what you mean by that. I haven't seen a true DC generator on a car since about 1965. All have been alternators since then.

No need to split hairs here, it just seems that you haven't come across an alternator with an external regulator in a long time. And yes, most car alternators have the regulator (including the diodes) inside and hence give out (pulsed) DC.

[newhaul]

Originally Posted by hzcruiser

No need to split hairs here, it just seems that you haven't come across an alternator with an external regulator in a long time. And yes, most car alternators have the regulator (including the diodes) inside and hence give out (pulsed) DC.

I have an externally regulated alternator on my ford pickup .

True a 1966 but its externally regulated.

[darylat8750]

My understanding is that the old true DC generators did not have a good way to reduce the output. The excess current was just wasted as heat so even when charge was not required the power taken from the engine was the same as full charge mode.

[Q Xopa]

Originally Posted by hzcruiser

No need to split hairs here, it just seems that you haven't come across an alternator with an external regulator in a long time. And yes, most car alternators have the regulator (including the diodes) inside and hence give out (pulsed) DC.

I think what he said is pretty much right on the money.

He was saying that what we consider to be a DC producing device, an 'Alternator' actually produces Alternating current. Hence the name.

Then then the term 'generator' is these day known to be an AC output device. Which as he correctly points out the term 'Generator' used to mean a DC Generating device. He was simply pointing out the irony of how we have changed the meaning of terms.

But his main take away was that higher voltages mostly associated with AC is more efficient than often discussed rectification losses.

Also I'm pretty sure he knows way more than most of us about externally regulating 'Alternators' and DC Gensets etc.

[hzcruiser]

Originally Posted by Q Xopa

Then then the term 'generator' is these day known to be an AC output device. Which as he correctly points out the term 'Generator' used to mean a DC Generating device. He was simply pointing out the irony of how we have changed the meaning of terms.
[...]
Also I'm pretty sure he knows way more than most of us about externally regulating 'Alternators' and DC Gensets etc.

No worries, all good.

[Q Xopa]

No worries.

His web page makes very good reading on the subject of DC Gens and other related topics. He has obviously put a lot of time and effort into his practical experience and research.

You may or may not also know that he has developed a very good External regulator and DC Gen controller. Arguably as good as anything else available. I dont know of anything better. Particularly considering the price he is selling them for.

I have his regulators and am very happy with them.

[hzcruiser]

Originally Posted by Q Xopa

No worries.

His web page makes very good reading on the subject of DC Gens and other related topics. He has obviously put a lot of time and effort into his practical experience and research.

You may or may not also know that he has developed a very good External regulator and DC Gen controller. Arguably as good as anything else available. I dont know of anything better. Particularly considering the price he is selling them for.

I have his regulators and am very happy with them.

And you're not referring to Al Thomason by any chance?


mv.VikingStar: Arduino based Alternator Regulator and Engine Controller

[Q Xopa]

yep, oops not the same? My bad