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Old 11-27-2019, 09:21 PM   #1
Mini-Skoolie
 
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Two alternators? Anybody doing this?

I have two unused a/c compressors on my engine with their own dedicated serpentine belt sheaves. I am thinking of using a GM style single wire alternator in place of one of these compressors to charge my house batteries when driving. Any thoughts?
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Old 11-27-2019, 09:24 PM   #2
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Yes. But you need a charge controller between the extra one and the batteries. I will be having dual MPPT controllers and just connect the second alternator to it. I will be doing a 23c/200amp alternator to the mppt. Keeping the engine alternator and the house alternator separate.
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Old 11-28-2019, 10:07 AM   #3
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Id like to hear how well that works for you with the dual Mppt charge controllers.
I’m looking at another way of charging using only one alternator but it requires solar in combination. Here’s a description:
Ive considering a revolutionary and custom way to charge Lithium or Lead Acid batteries in a bus. Any suggestions or corrections are appreciated. It’s custom and requires rethinking the whole system. But it would transform the alternator charging from 30%-50% efficient to 70%-80% efficient and would integrate it with solar in a seamless system. So this is for topnotch systems. Would be a investment. And it would be programmable. I hijacked the technology from cutting edge micro hydro/solar technology which is very efficient and integrated. You would even be able to see what it’s doing using Bluetooth on your smart phone. Or on a computer 10,000 miles a way using WiFi.
This is a expensive system and probably only worth doing on a large bus or Coach. As it requires a large solar array to clamp the alternator voltage.
Step 1: toss out the 12 volt alternator and bolt in a 48 volt alternator but do not connect it to the 12 volt starting battery. Or even better use a Harris alternator with powerful magnets and adjustable magnets.
Step 2: connect the 48 volt alternator to a programmable Mppt charge controller in parallel with a large solar array on the roof to the 48 volt house battery. The solar array acts like a zener diode and clamps the voltage of the alternator. The charge controller tracks the maximum power point. A very efficient and programmable setup.
Step 3: connect a big programmable DC to DC charger from the house battery to the starting battery. Now the starting batteries will also be connected to the solar and alternator through the house battery . Never need to worry about them being discharged.
Step 4: install a DC to DC converter from the house battery to the 12 volt DC loads. Or several step down DC to DC converters if the loads are big.
One could do a trick dual alternator setup if there is a massive 12 volt A/C load. But with a big DC to DC converter this extra alternator should not be necessary. But I would switch to a mini split inverter heat pump A/C that runs from the inverter/charger.
The Mppt charge controller can be programmed to charge Lithium or Lead Acid. The DC to DC Charger can be programmed to charge Lithium or Lead Acid. It offers flexibility.
Basically this is replacing the old low voltage analog DC systems in the coach with all cutting-edge technology high voltage DC digital systems. The entire system can be integrated together fairly easily. Well almost the entire system. It’s not the space shuttle.
This is the type of system I’m considering building on my Overlander Isuzu or my shortie skoolie
I forgot to mention the amperage. If using a 100 amp Midnite Solar charge controller to a 48 volt house battery it can handle 4800 watts of total solar/alternator. So if you charge from about 2000 watts from solar and 2000 watts from the alternator it’s a good balance and below the maximum threshold. The solar needs to sized correctly to clamp the voltage or the panels may heat up. The solar needs to be equal or slightly bigger than the alternator output
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Old 12-08-2019, 07:39 PM   #4
Mini-Skoolie
 
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Instead of 2 alternators, maybe install a "A/B" switch so you can select the bus battery or the "house" battery...some switches would allow you to select both batteries which would enable you jump start yourself with the turn of a switch. These switches are common in marine applications.
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Old 12-08-2019, 09:13 PM   #5
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Thanks for the reply. I have several boats so am familiar with many marine switches. I am just researching a redundant system on my bus.
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Old 12-08-2019, 09:30 PM   #6
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Yes. But you need a charge controller between the extra one and the batteries. I will be having dual MPPT controllers and just connect the second alternator to it. I will be doing a 23c/200amp alternator to the mppt. Keeping the engine alternator and the house alternator separate.
Be careful, you might let the magic smoke out
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Old 12-08-2019, 09:36 PM   #7
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Originally Posted by smokescreen View Post
I have two unused a/c compressors on my engine with their own dedicated serpentine belt sheaves. I am thinking of using a GM style single wire alternator in place of one of these compressors to charge my house batteries when driving. Any thoughts?
I am actively looking for a bracket to mount a second alternator to charge my house battery bank. Balmar makes some wonderful alternators with three stage charging and available in 12v or 24v.

If you happen across a bracket for a second alternator for the Cummins 8.3 please let me know.
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Old 12-08-2019, 11:52 PM   #8
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My bus came with a wheelchair lift and while I haven't looked at my alternator, I would assume it a high output alternator. Could this not be wired to provide charging for a modest (212 AH) house bank
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Old 12-09-2019, 09:44 AM   #9
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For those of us that have deleted the factory AC is it possible to mount an alternator directly in place of the AC compressor?
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Old 12-09-2019, 01:07 PM   #10
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I used a marine bank switch to allow me to tie my alternator in with my house battery bank. I can't imagine doing anything much more complex than that.
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Old 12-09-2019, 04:07 PM   #11
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For those of us that have deleted the factory AC is it possible to mount an alternator directly in place of the AC compressor?
Iíll second this question as Iím considering placing a second alternator where the A/C compressor is. Would think it would just take lots of time fabricating brackets unless a kit is available.
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Old 12-09-2019, 05:50 PM   #12
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Aux Alternator

I have a 2000 DT466E in an Amtran FE, I was looking into adding a second alternator and wanted to reinstall an A/C compressor for driving A/C as well.
I could not figure out how to add both so I settled on increasing the standard alternator which is a 130 Amp Leece Nevile J180 mount alternator and installing a 275-320 amp Delco 40SI brush-less alternator.

these alternators produce 160 amps at idle and produce up to 320 or 275 amps while driving. I will then use a continuous use solenoid to switch the output of the alternator at the starter to a separate 2/0 cable to the house batteries.

This solenoid can be turned on with a rocker switch at the dash. This is an option for a redundant battery charging system should the solar panels not be able to keep up with demand on cloudy days or high usage at night.

After doing this I can install the Sanden compressor on top of the engine where the original York compressor was and install and engine driven A/C system.
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Old 12-09-2019, 07:36 PM   #13
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Just be careful about charging house (i.e. deep-cycle) batteries from a vehicle alternator. Simply, alternators don't do a good job charging deep-cycle batteries and will probably shorten their lives. Alternators are intended for spongy-plate SLI batteries, not thick-plate continuous-load batteries that best work with a three-stage (Bulk, Absorb, Float) charger.

John
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Old 12-09-2019, 08:03 PM   #14
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Sounds good if you run your bus a lot. Mine is parked a lot so Iím weighing alternatives. Unfortunately my roof wonít fit a lot of solar with out major work so Iím planning on towing my cargo trailer that already has 1350 watts of solar panels and a energy system inside. Then Iíll see if I need to change my alternator. What about maxing out your solar and seeing if you need that big alternator?
And as was mentioned batteries love solar and three stage charging.
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Old 12-10-2019, 07:16 AM   #15
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Quote:
Originally Posted by brokedown View Post
I used a marine bank switch to allow me to tie my alternator in with my house battery bank. I can't imagine doing anything much more complex than that.
If it works good that’s great. Maybe you have a more robust system than some. Such as a large frame alternator that dissipates heat better. Or good alternator ventilation and location away from exhaust manifold. Or your battery and loads are not too big for your alternator. And the voltage is high enough to keep pushing amperage into the house batteries until they are fully charged. What regulator do you have? There’s no other battery isolator at all? Are your house batteries and starting battery the same type? Ive never had a boat with one of those switches so don’t know. But it sounds nice and simple.
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Old 12-10-2019, 07:37 AM   #16
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According to the folks at Batteries Plus and Interstate, the AGM deep cycle batteries they sell are designed to be charged by an alternator.. they sell these for use in standard vehicles and in Boats.. all charging with alternators vs completely controlled chatging systems.. the warranties on these batteries indicate they expect long-life from them...
-Christopher
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Old 12-10-2019, 07:51 AM   #17
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Originally Posted by Doktari View Post
If it works good thatís great. Maybe you have a more robust system than some. Such as a large frame alternator that dissipates heat better. Or good alternator ventilation and location away from exhaust manifold. Or your battery and loads are not too big for your alternator. And the voltage is high enough to keep pushing amperage into the house batteries until they are fully charged. What regulator do you have? Thereís no other battery isolator at all? Are your house batteries and starting battery the same type? Ive never had a boat with one of those switches so donít know. But it sounds nice and simple.
Works well, but I rarely need to use it. My electricity needs are surprisingly low and my solar is almost always more than adequate. but if we get a few nasty days in a row, I need to ad juice from another source. If I'm parked I can fire up my generator and run my 30A boost charger, but if I'm driving anyway the alternator is free power.

I've got a Bosch SB200 alternator, 200A designed specifically for buses, makes most of its power around idle speeds. My battery bank is AGM so simply connecting the banks will do it. The bank switch I use is rated for 250A continuous. And it works both ways, if I need to charge my start bank from solar because i left the lights on (hasn't actually happened... yet) it's a twist away.

This is the same tech they've used on boats for decades. My 1979 Pearson 35 had effectively the same bank switch on it.

This is the switch i use: https://amzn.to/2RGsCAP
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Old 12-10-2019, 09:46 AM   #18
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Quote:
Originally Posted by Iceni John View Post
Just be careful about charging house (i.e. deep-cycle) batteries from a vehicle alternator. Simply, alternators don't do a good job charging deep-cycle batteries and will probably shorten their lives. Alternators are intended for spongy-plate SLI batteries, not thick-plate continuous-load batteries that best work with a three-stage (Bulk, Absorb, Float) charger.

John
Balmar makes alternators that feature three stage charging and are easier on deep cycle batteries.

Now if I could just find a bracket.
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Old 12-10-2019, 02:11 PM   #19
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Thanks for the reference to the Balmar alternators. Those look very interesting. I am interested in a second alternator. I think I have plenty of room. It looks like there are at least 2 or 3 places I might be able to fit one in. My police model Crown Vic had the alternator replaced shortly before I bought it. I've forgotten the number but the output is much higher than the standard alternator on the 4.6L.

But Balmar's alternators sound more appropriate. They look expensive, but I did not check out prices because I know I will be able to afford it after this house sells.

And a question about brackets, I'm thinking about designing my own and hiring someone to fabricate it for me. Has anyone here designed or built their own alternator mounting bracket?

[edit] The downloads I got from the Balmar website look very useful too.
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Old 12-10-2019, 02:46 PM   #20
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Quote:
Originally Posted by gs1949 View Post
Thanks for the reference to the Balmar alternators. Those look very interesting. I am interested in a second alternator. I think I have plenty of room. It looks like there are at least 2 or 3 places I might be able to fit one in. My police model Crown Vic had the alternator replaced shortly before I bought it. I've forgotten the number but the output is much higher than the standard alternator on the 4.6L.

But Balmar's alternators sound more appropriate. They look expensive, but I did not check out prices because I know I will be able to afford it after this house sells.

And a question about brackets, I'm thinking about designing my own and hiring someone to fabricate it for me. Has anyone here designed or built their own alternator mounting bracket?

[edit] The downloads I got from the Balmar website look very useful too.
They are not cheap

I am looking at their 100 amp 24 volt three stage alternator. Price is around $800.

My father used to tell me "Son, the oats are always cheaper after the horse."
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