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Forum Index : Electronics : Converting regular alternator to 48 volts
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| BenandAmber Guru  Joined: 16/02/2019 Location: United StatesPosts: 961 |
I would like to put an extra alternator on my bus to help charge my battery Bank while I'm driving down the road The bus is going to be all 110 volt electric so going down the road I will still need to use my air conditioning so the alternator would offset any insufficiency of the solar panels hopfullly I'm still new to solar and don't know what 3000 watts worth of solar will do for a bus I will have more solar when I get to where I'm going and get set up going down the road I will only have a little over 3000 Watts So that's what I'll be using the alternator for but I'm hoping to be able to modify a regular alternator run 48 volts instead of 12 volts I've heard this was possible I figured you guys on here would know the best way to do it be warned i am good parrot but Dumber than a box of rocks |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
There are a few ideas floating around, but I couldn't find anyone that actually did it successfully. You can buy them new. Ebay Aus has a few, I'm sure USA will have a bigger selection. 3000w of panels is a lot for a bus. You need to look at what appliances you plan to use in it, heating, cooling, cooking, hot water, refrigeration are the main culprits for energy consumption. If you can use gas for cooking and hot water that will take the pressure off your system. Edited 2019-08-05 14:30 by renewableMark Cheers Caveman Mark Off grid eastern Melb |
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| johnmc Senior Member  Joined: 21/01/2011 Location: AustraliaPosts: 282 |
Car alternators are inefficient . To increase the voltage on a alternator for example 12v to 48 volt requires 4 times as many lines of magnetic force to be cut so . This requires 4 times as many turns on the stator which will give you 4 times the voltage and 1/4 the current ie same power. The speed of the alternator is limited by centrifugal forces about 7000 to 12000 Rpm depending on the rotor dia, so it is not possible to increase the revs by a factor of 4. Also heat generation by the alternator also becomes a limiting factor outside the designed power of the alternator. Their is some 48v alternator in very late model cars, but I have not seen any. Cheers john johnmc |
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| kentfielddude Regular Member  Joined: 09/05/2019 Location: United StatesPosts: 89 |
you could buy a cheap generator or second hand generator. |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
I have a generator Onan generator I just thought it'd be nice to have a 48 volt alternator hook to my Detroit Diesel so it could just run off it be warned i am good parrot but Dumber than a box of rocks |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
I need something that the RPMs could change still output electricity I could rectify it and then send it through a mppt charge controller I just want something that's heavy duty reliable I have a large 3 phase industrial motor that I epoxied magnets to the rotor after I turned it down It works surprisingly good but I'm afraid of the magnets coming loose Might be better just to run a generator Thought I would bring the subject up to see if any of you guys have done anything like this before or have some really good ideas If I could find a reasonable priced 48v alternator would be the best thing I'm mainly worried about the air conditioning while I'm driving down the road be warned i am good parrot but Dumber than a box of rocks |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1032 |
For what it is worth, I run a 12V alternator at 42V for charging 36V batteries supplying 36V 1000W motors used intermittently. The alternator had an external regulator so I just designed one to up the volts a tad (well 3 times). The field supply still runs from a 12V system though to simplify things. (You don't want more than ~12V across the field coil & using a dropping resistor would waste a lot of power & you would need somewhere to put it). As mentioned above, you need lots of revs. My original set up had plenty of them & I got heaps of current although it wasn't used continuously. I now have a different setup with lower revs & not as much current but enough for the job. Taking an alternator up to 56V or so, may be stretching the friendship a bit so to speak. You may be better starting with a 24V truck/bus alternator if you want to go down that path. ChopperP |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Most 12v alternators begin to charge at around 2,000 alternator rpm with full field excitation. The alternator pulley step up ratio from the crankshaft on most vehicles is typically about 3:1 to 4:1 which makes the alternator warning light go out at around 500 rpm to 670 crankshaft rpm. With those kinds of pulley ratio, if the engine peaks at 5,000 rpm, the alternator will be going x3 to x4 times that speed or 15,000 rpm to 20,000 rpm quite safely. If you want to start charging at 48v you will need a MINIMUM alternator rpm of 8,000 rpm which is fine. The trouble will be when you drive your bus on the road. It will probably over speed your alternator. Lots of alternator rpm works well with a stationary engine, and a really big pulley speed step up. But the same trick is not really practical to do on a road going vehicle. Cheers, Tony. |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 506 |
Have you thought about using a boost converter 12v to 48v .. limited current (1 - 2 kw with plenty of cooling). Keeping everything stock on bus, and very controllable... https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F383054630841 Something like this. ... I think it works !! |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
This is exactly what I was looking for I wanted to get your guys's thoughts I really appreciate it I don't want to run something too fast take a chance of a flying apart 12 to 48 volt boost converter may work Cheapest 48 volt alternator I can find is $800 That's just not an option for me What do you guys think about rewinding a alternator Maybe find the very biggest Industrial heaviest alternator and Rewind it Thank you guys for your thoughts be warned i am good parrot but Dumber than a box of rocks |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
what about a 48v permanent magnet motor? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
There is another very different way to go about all this, using a standard 14v alternator running at normal speed. Just use three transformers that each provide an approximate 4:1 overall voltage step up ratio, and rectify the output from that. The disadvantage is that the power increase you can get by increasing the alternator rpm does not then apply. If its a 75 amp alternator you are only going to get roughly 75 x 14v = 1Kw. Its going to be a lot easier to do it that way than to rewind the alternator. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
48V alternators can be had affordably. https://www.alibaba.com/showroom/48v-alternator.html I'd get at least 2 so you had a spare. Why go 48V though? The bus electrical system is likley to be 24, there are plenty mppt controllers that will take 30V panels down to 24 and lots of 24V inverters. Finding high output 24V alternators will also be a lot easier and cheaper than 48V. Car/ truck alternators are Very efficient, they use the same claw pole design as power station alternators. What is very inefficient is the Regulators. There are a number of staged/ stepped regulators out their like Balmars and others that allow a lot more control and far greater charging efficiency than the built in regs. They allow one to get a lot more power out of the same alternator than what would happen with the built in reg. They are reasonably priced and widely used on boats and RV's. http://www.balmar.net/multi-stage-regulators/ Why do you want to run electric air con when driving down the road? Much easier and far more efficient to just put a compressor on the engine and run AC Direct. There would be heaps of systems you could buy used for a bus/ coach and just fit to your own. 3Kw of solar sounds a lot for a bus but it's only 12 250W panels so should be doable depending on what else you put on top. You won't often get anything near 3 KW out of them so I think the more you can stack up there the better. I think keeping to 24V on a vehicle would be a lot better, easier, cheaper and more repairable than 48V. I take it you will be travelling with this so having a conventional alternator screaming away to make 48V or a rewound one of unknown longevity to me sounds like bit of a gamble. |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
So before the diodes there is AC so take that AC and run it through a Transformer??? I am liking the sound of this this is sounding like a really good solution regular cheap alternator get a thousand extra watts Not exactly sure how to do it though Do you care to explain a little bit more I really appreciate your wisdom and time be warned i am good parrot but Dumber than a box of rocks |
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| Ironmaiden Regular Member Joined: 09/07/2019 Location: United StatesPosts: 53 |
There are small AC generators for mounting on Fire Trucks and the like. They are usually about 3500 watts. The frequency varies unless you also buy the special voltage regulator. Or use a hand throttle when the bus is stationary to set the RPM to hold 60HZ. These units are very overpriced IMHO. However, They do show up on Govt auction sites sometimes for cheap. Fabco Gen The AC coming from a regular alternator varies from 200HZ to 400HZ. I've used a car alternator to generate 110v DC and 400HZ AC powered from an old Briggs engine. There are some converter boxes that allow you get 110v DC from a car alternator. I've got three of the vintage contraptions. They are nothing more than a 3 pole double throw switch, an indicator light, and a circuit breaker. (I've seen them with screw in fuses). The DC coming out has a very high ripple current. I can power anything like brushed motors, incandescent lights, and heating elements up to 746 watts. Some of the big alternators like the Leece Neville types can do up to 3000 watts. A good book on using alternators is (Alternator Secrets by Lindsay Publications) It's available on the web if you do a Google Search. If it was me, I'd look at having a Onan RV generator or similar pancake diesel generator slung under the frame of the bus. Isn't there some compartments under the bus? Robert Edited 2019-08-08 02:02 by Ironmaiden |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
Yes there is giant compartments underneath there so big I could put a washer and dryer in them I have an Onan generator also have a second exhaust that goes all the way from the generator Bay to the back of the bus Problem is I don't want to ever run a generator so I have used the generator Bay for my battery Bank I took out the big giant stainless steel fuel tank for the generator and have redone that compartment and installed my batteries in it Between the fuel tank and the generator you're probably looking at well over a thousand pounds and took up all kinds of space I have a small power washer (without pump) that I will be putting some kind of generator on also I want a backup for my backup on the back of the 6 V 92 supercharged and turbocharged Detroit Diesel there is a big spot on the right where in the Greyhound versions of this have a big air conditioner pump there's already another belt space that would be used for the air conditioner pump on the same pulley as the hydraulic pump that goes to the hydraulic motor for the big radiator fan So there is a big space there just begging to be used for a second alternator for the battery Bank When I'm sitting still I'll be able to put my awning out and have another 2 to 3000 watts of solar and this will not be needed When driving down the road I'm only going to have a little over 3000 watts of solar and I'm not sure if this will be enough to keep the air conditioning going in the bus without depleting my battery Bank So even a thousand Watts alternator wood probably give me that extra little bit of wattage I need to run air conditioning going down the road Sorry so long I will get a few pictures today when I go down to the bus pictures might describe it better then I can be warned i am good parrot but Dumber than a box of rocks |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
what bus do you have? https://www.ebay.com/itm/1450-WATT-PMA-48V-4-ENGINE-USE-Permanent-Magnet-Alternator-Generator-PC1248DC/232775180731?epid=622606519&hash=item36327b61bb:g:Xi0AAOSwAL9UjOdz Edited 2019-08-08 05:53 by kentfielddude |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 Silver Eagle same thing as a greyhound mine's just the tour bus version be warned i am good parrot but Dumber than a box of rocks |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
here is a 48v alternator kinda expensive |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
Thank you for finding that for me it is a permanent magnet alternator I'm looking for one that has electromagnet in it so it can regulate itself Or I might use something like that and send it through a mppt charge controller Davo99 I have 330watt solar panels 10 will fit on top the bus can only use 9 of them 3 series connected and parallel those sets of three gives me around 115 volts to my mppt charge controllers I will have another set of 9 on my awning so around 6,000 Watts when parked but only around 3,000 watch when driving down the road The buses electrical system is 12 volts and I have two very large batteries hooked up to that it will only be used for starting and running the bus All of the rest of us is 110 volts ac Thanks to the good people on this form I have a home built inverter with a 52-pound 5000 continuous watt Transformer the board that's in the inverter can do up to 10000 Watts continuous The interior of the bus is 100% 110 volt electric I am Universal HVAC certified and would be no problem for me to put a pump on the motor I just didn't want to have a whole other system for just going down the road Edited 2019-08-08 07:27 by BenandAmber be warned i am good parrot but Dumber than a box of rocks |
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