Plane-Power vs B&C (2019) also: Parts info wanted

[TimO]

Charlie, thanks a ton for sharing the link to that West Marine article. This is EXACTLY what I was guessing when I said I think we'll see some differences going forward, as people put in Lithium type batteries. They may not realize that their alternator choices may need to be changed. That article explains things very well.

This part specifically has some information that applies to us as well, with our alternators being close to exhaust:

Temperature ratings are often determined using a military standard of 122?F, measuring the ambient air temperature in the vicinity of the alternator. Sustained operation in hot engine room conditions will reduce alternator output. A hot alternator, operating at approximately 180?F?200?F will only supply about 80 percent of its rated capacity. Large-frame models generally run cooler than their smaller siblings because of their ability to dissipate heat. Small case alternators are not designed for continuous high-output operation.

I just checked out the earthx pae and see that their ETX680 says 60A alternator or less, whereas their EXT900 says 80A alternator or less. The "or less" part is a little confusing or maybe misleading. You would think they should phrase it differently, like maybe one would need a 50A alternator "or more". A couple of my lithium equipped buddies are able to fully max out their 60A alternators with their batteries. I'm not sure if they are the 680 or 900. But, for the first part of the flight, they're pulling full capacity. Now, if you are looking at a hot day, or hot start, and start taking into account hte temperature ratings, you could really be over-taxing an alternator. I'm sure since it's not a long-term load it will work out for many people, for quite a while. I just think that long-term, it may start to change some of the trends we see in alternator longevity.

Sorry, that got off on a whole tangent that I didn't really intend. But, it just shows how important it is to look at the complete big picture when you choose components for your plane. Personally, I would think it smart to go with a bigger alternator in the case of lithium batteries. What would be nice is if there was a way to have a more controlled charge, but a full-power discharge capability for them for starting. After all, it's less desirable to charge any battery at super high charge rates, if you can avoid it. My normal running load on my planes is about 22A. A 60A alternator works great for that. I personally would love to keep my alternator load below 80%, or 48A, if possible, at all times.

[chaskuss]

Tim,
Your "rant" as you call it, really contains a lot of excellent information. People who aren't knowledgeable about electrical or electronic matters generally think that a 60 amp alternator is a 60 amp alternator. Not true! Those nice small lightweight alternators that generate the same amperage??? Do you really think that you're getting something for nothing? ( the same power for less weight). There's always a trade-off. In the case of lightweight alternators, some of the components have to be made smaller. Specifically the brushes and the diodes in the rectifier Bridge. There are always exceptions but as a general rule when you make a diode smaller, it can't handle as much power OR it's fragile under high power loading. And the smaller ones that can are $$$! You're very wise to say you want to keep your alternator output below 80%. That will go a long way towards improving the longevity of your alternator.
I stumbled across that article while doing a search to see if I could find an automotive or Marine external voltage regulator that offered both alternator and battery temperature sensing. Those Builders using lithium technology batteries should strongly consider installing a voltage regulator that can monitor both the alternator and the batteries temperature. Modern internally regulated alternator have the capability to monitor the temperature of the alternator itself. Many of the automotive manufacturers simply figure that since the alternator and the battery ( assuming the battery is under the hood) will be operating at similar temperatures. I strongly suspect that the folks on this list who are reporting short alternator lives probably do not have adequate heat shielding to protect the alternator from their exhaust system.

Charlie

[chaskuss]

Tim,
West Marine touts Balmar brand alternators and voltage regulators. The Balmar model MC-614 multi-stage voltage regulator has an amazing list of capabilities. I suggest you download the installation and operation manual for it and read up on it. It can monitor alternator temperature, it can monitor dual battery temperatures. It has multiple programmable charging strategies for all the different battery technologies that are available today. Really quite amazing piece of equipment. However I was doing this research at 3 AM. I seem to also remember in another Ballmer document saying there was a Prohibition against using this voltage regulator with crowbar over-voltage protection. That's why I hadn't mentioned it earlier. If you have the time, look for a document produced by Balmars tech support. I think that's where I read about the prohibition against crowbar over-voltage protection. That said, this unit can't be the only product of its kind of available on the market. I'm sure with some research we can find others.
I almost forgot, in my research I found Balmar gives a good rule of thumb regarding sizing alternators to batteries. The rule of thumb is this. For standard flooded acid batteries the alternator should be sized so that its output is 25% of the batteries capacity. For gel cell and AGM batteries I believe it's 45%. For lithium batteries it's 50 to 60%.
Charlie

[Dan Langhout]

Thanks Tim!

[RVDan]

Originally Posted by TimO

I just checked out the earthx pae and see that their ETX680 says 60A alternator or less, whereas their EXT900 says 80A alternator or less. The "or less" part is a little confusing or maybe misleading. You would think they should phrase it differently, like maybe one would need a 50A alternator "or more".

The reason they limit the alternator output is because their battery management system doesn?t limit charge current. Lion batteries have a very low internal resistance and will take very high charge currents. So, if for example, you have a 100 amp alternator, and you had a partially discharged battery from starting, the battery will accept all 100 amps. Sounds great, but this heats up the cells and can cause battery failure. Therefore they limit alternator output to a value that they know won?t toast the battery.

[TimO]

That makes sense, thanks Dan. So basically it's got a narrow operating envelope if you look at it that way. On one hand, you don't want too large an alternator, or you can destroy the battery with too much charge current. On the other hand, if you get too small an alternator, you may cause early death of your alternator due to the alternator running hot or working too hard. So given that, the 40A model is probably not good for a Lithium install, and you would want to pick the best battery size for your 60A or 70A alternator. It's too bad they don't have a current limiter on the input. It would make the alternator choice a little easier.

[chaskuss]

Originally Posted by chaskuss

Tim,
snipped. During the 1990s Nippondenso actually did have one automotive customer who wanted a high output, quality Nippondenso alternator that would use an external voltage regulator. That customer was Chrysler Corporation. So if you want to have a Nippondenso alternator that's externally regulated but you don't have to do surgery on, go to your local favorite auto parts store and order an alternator for a 1995 Dodge half ton van. These trucks came with a V6 and V8 engine option. Engine doesn't matter. Both the V6 and V8 were available with a 90 AMP or 120 amp alternator. You want the 90 AMP unit as the 120 amp unit is considerably more expensive. These alternators are physically and externally similar to the 70 amp alternator that you used to have on your RV 10. The one difference is there's no internal voltage regulator. Where other Nippondenso alternators have a voltage regulator, these Chrysler units have a terminal block with two studs for wires to go to your external voltage regulator. On the original trucks the external voltage regulator was actually built into the PCM aka engine computer. Chrysler installed a temperature sensor under the battery so that the computer could monitor battery temperature and modify the field voltage to compensate for a battery that was getting too warm.
snipped
Charlie

The Lester number for this alternator is 13354.

The Lester number for the 1992 Camry 70 amp alternator that I also mentioned earlier is 14849. This is an internally regulated alternator that can be converted to external regulation without any major surgery. It's a simple matter of removing the internal voltage regulator and the brush pack and replacing them with the terminal block and brush pack for the Dodge van alternator. Cost for the conversion Parts is about $15.

Charlie

[chaskuss]

Originally Posted by Lux Wrangler

I have been looking at the Chrysler alternator, online, for some time. Specifications list the weight at 12 pounds? Does the PlanePower pulley fit the shaft diameter? Is the housing small enough to fit in the space?

Jim, I sent a question to Advance Auto Parts asking them the weight on both the 90 amp alternator designed for external regulation for the 1995 Dodge van and also for the 70 amp alternator for the 1992 Toyota Camry. Surprisingly the 90 AMP Dodge van alternator is lighter. According to Advanced, it weighs 10 lb. The 1992 70 amp Toyota Camry alternator weighs 12.6 lb. I guess that's not surprising when you look how massive the mounting points are on it.

Charlie

[rv6ejguy]

A few points. If your engine is in proper tune, you shouldn't have to turn it over for more than 5 seconds. This takes very little out of the battery and therefore won't result in very high charge current from the alternator to replenish it in the first minutes.

If you're concerned with too much charge current, keep the engine at idle for a minute or so. A 60 amp alternator will be lucky to produce 30-35 amps at slow idle.

If you run a lithium battery and it's really discharged for some reason, think about delaying your flight and getting a low rate charge on it for a while and be sure you know WHY it was so discharged to begin with. If you're electrically dependent, treat that battery with respect and care. Your life may depend on it.

If you firewall mount your battery, be aware that it will almost certainly see temps over what the manufacturer recommends without some air blast cooling. High temps reduce life and may have more serious consequences in some cases with certain battery chemistries.

[scsmith]

An interesting data point on alternator reliability, from the automotive world.

My 2000 Chevy Astro Van went 180,000 miles on its first alternator. It failed last month. Not feeling like working on the van (poor access to most everything on the front of the engine) I paid a shop to replace the alternator. At the time, I walked out of the shop thinking that was the most expensive alternator I ever bought (because of the installation labor charge).

Today, that new alternator failed, after just a couple of hours of run time. Infant mortality I guess. The shop said it was "highly unusual". He wasn't sure if it was an ND or a Bosch (he wasn't the tech that did the replacement). This time I walked out thinking it was the best deal I ever got on an alternator, because I didn't have to go through the chore of replacing it twice!

I don't know the exact failure process, but I can tell you that it made a distinct whine/whirring noise, and then started to smell strongly. Then I noticed it wasn't charging.

I don't know if this experience is relevant to any of our alternators or not.