What's the biggest alternator available?

First off, Batts are the problem, not your alternator. I've done the math a million times and there are no great battery based systems.

Consider this. Lets assume you have a good set of AGM batts. Each holds 100 amp hours and is 12 volts. (only 14.4 when fully charged, 12 is a better average voltage) Each holds 1200 watt hours. 4 batts is 4800 watt hours or 4.8 Kila Watt hours. (kwh) Now, the most efficient air conditioning units use around 500 watts hours/hour average (.5kwh). So, assuming we could completely drain the batts (we can't) and the a/c is at peak efficiency, you can even make it a full 10 hours. Now you may be able to find slightly better batts, but the most you will get is 10 hours on 4 batts. You can add more batts, but batts are heavy.

Now lets get into charging them. Most trucks only use 20 amps to keep running with everything on. This means you have 115 amps left to charge the batt. This should charge at around 14 and thus 1610 watts. (1.6kw) This means we can charge your bank of 4.8kw at in only 2.98 hours of cruising. I assume you drive for more then 3 hours a day so your batts will remain topped off with no problems. A bigger altinator just reduces that time, but does nothing to help once you shut the truck off. if you add a bigger alternator it will be doing nothing for more time. Now they do make 200 amp altinator or even duel altinator configurations, but unless you have a huge bank of batteries you dont need it. Large altinators are needed for local work where there will be a lot of stops and starts with little drive time in between.

So, with the most efficient ac and the best batts, you get 10 hours of a/c.

Lets look at adding solar. 11 amps is STC rating and only happens in perfect conditions. Unless the panels face south at 30 degre tilt, and track the sun, your not going to see anywhere near stc conditions. (I was a solar designer before jumping into trucking) Also, temp negatively effects solar. If your over 55 degrees, you will get less power. So really, were not talking 11 amps. Were talking maybe 2 or 3 amps at noon and less the rest of the day. Compared to the alternator output this is nothing. Your best bet would be to get rid of them. This would be more aerodynamic saving fuel, and save weight. Each panel weights around 25 pounds. Thats one more batt worth of weight. (if they are the modual i think your talking about) To put this in perspective, your solar takes all day to provide the same power your alternator puts out in 20 min.

So, my advice: Ditch the solar and put as many batts on board as you can afford in cost/weight, or go with an apu. Batts are your limiting factor, not how fast you can charge them. Also there are no practical battery based solutions for 34 hour resets. If you want to go batt for 34 hour resets, turn ac off when it gets cooler at night. Also when batts dies, run truck at 1500 rpms for 3 or 4 hours. Better then idleing the whole time.


So, why do other drivers have solar? Well, its because they dont know enough about it and never did the math. There is a program called pvwatts that can acuratly show your solar output. The only way solar could possibly be effective is for night time drivers. The solar could supplement while the truck is off. But for a 34, it wont supplement well enough. if you coated the whole roof of your trailer in solar, you might be able to generate around 5kw of power and run an ac system in the summer. 5kw worth of panels though is way to heavy to be practical though.

 

Well done Richter but I didn't see one point needed.

Folks run out and buy say a 200 amp thinking they get 200 amp service...well they do and they don't. A 200 amp rating simply means the alt can and will put out 200 amps if needed...that's it. Peak performance.

If one was to load the 200 ( or 135 etc ) to the rated capacity and hold it the alt would fry. None are designed to run peak 100%of the time.


Just saying.....

 

If you want the best battery in the business theses bad boy will fit your needs
when you start your truck, the starter sounds like an air starter.

http://www.getlithium.com/1-lithium...r-Truck-Marine-lithium-ion-batteries.html#top

 

Personaly, if its a decent alt with high efficiency and proper cooling ive never seen one fri. Normally when they fail, its bearing not it frying. In any case, the alt wont produce the whole 135 if it cant handle it, but it can produce close to. In either case, unless he drives less then 5 hours a day it is moot point.

 

Price is ridicules. They are lighter but size is huge. for the same storage capacity of 4 agm (1000 bucks) they cost 6400 bucks. Also lithium like clean power and precise charge amperage. Unless you use with a charge controller, i highly dought you would get the advertized cycles. The problem with a charge controller, is as the batt gets abover 80% the charge rate will slow and thus not use the full capacity the alternator can put out. Lith can co form 5-80% much quicker then from 80-100. Another problem is if you ever accidentally drain it all the way. They may have discharge inhibitors, but they dont always work. If a lith batt goes all the way down, it wont take a charge again.

 

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can not be used in sub freezing temps. WHAT? I guess that wont work on trucks. They sell add on insulation, but not sure how well it works. Id consider myself an early adopter of most tech, but not batts that may freeze and not work.

 

Read your own original post. You asked for solutions but didn't say anywhere only "experienced people" could answer. So no, you didn't ask for experience. I have experiance with off grid battery based solar. I also have experience using generators to supplement. So you have an engine instead of a generator. pretty much the same thing. If you provide specs on your panels, I could accurately tell you hop much power they will produce each month.

First off, 11 amps isnt enough to run a fridge and electronic even if you don't use a/c. It may be, SOME week-end, but one rainy week-end and everything goes dead. Why does your truck need any power while your in Europe. Turn off your fridge. Saying the solar system is easier and cheaper is wrong. If you have a bad day, it fails. Thats not easier. best option for extended vacation is either shut everything off, or bobtail home and plug in your truck to a 50 dollar batt charger. 20 min of fuel cost about a $1.30. How much did you spend on those pannels? They are only saving you 1.30 a day, assuming they are working as good as you think.

I wasn't insulting you, but just buying the biggest alternator you can wont solve anything. I simply was giving you some info so you dont waste 400+ bucks on something you dont need. You say a steady 11 amps. Have you taken into account that during the winter you only get 1/4 of your summer power depending on where you are? Are we even assuming 12 volts here? If you get shade on a panel, voltage drops for a large section of the panel. If you installed bypass diods, this should just shut down one panel, if you didn't, the panels could lower their over all voltage to less then the required charge voltage because only one is shaded. Did you install back feed cut offs? If not, the panels will actually drain your batts at night. You can have all the amps you want, but if volts aren't high enough, its useless.


I was a great solar designer, but the industry crashed when the government stopped supplementing it. 600 companies went out of business in 1 month. Me switching careers does not disprove my credibility as a solar designer.

The power needed while running is irrelevant. I used an assumption so I could show you the math. a lower assumption makes the alternator a little more efficient but doesn't change the result of the math. Math is used to design solar arrays all over the year. If they were designed by me, they preform pretty darn close to the math. You can't say....person A's truck solar system works so ill make mine identical to his. Your truck is different, your load is different, and person A might not even have the data other then gut feeling that it is working the way he says it is.

As for your idleing less to recharge on a 34, I normal idle for 30 min twice and am completely fine. If you need an alt, and upgrade isnt a bad idea, but i wouldn't go out and buy a bigger one just for the heck of it.

As for your alt is cheaper then hauling around more batts, they do 2 different things. More batts allows you not to idle ever on you break. Bigger alternator just mean is will cost less time when you do idle on your break. If you want to run a/c you will have to half wake up half way through the night to idle for 3 hours. With a larger alt you could cut that to 2 hours, but you still need to wake up. You also need to charge the batts a lot, not just a little for electric loads. Solar would not help here. (because 11 amps is nothing) With more batts you could make it all night without turning the key. So how is a bigger alt cheaper then batts when you have to idle 2 hours a night to run a/c?

 

That pisses me off. You read your original post....you never asked for actual experience. Not to mention, I was in the solar industry and have actual experience. Not on trucks, but designing off grid solar with gen back up running a/c. Just swap out the gen for a motor and its the same thing. Also yours moves and ths pannels wont be facing sue south.