12VDC with Dual Alternators
12VDC with Dual Alternators
(OP)
Hello everyone,
I am working on an automotive project where I would like to run 2 alternators. The first alternator will be the stock one and drive all of the stock/factory electronics. The second will supply power to a lot of aux electronics.
There are a lot of reasons I want/need to run 2 alts and 2 batteries (basically 2 separate systems) that I don't have time to explain at the moment, so just take my word for it for now. I can explain more if necessary, but it boils down to the aux electronics be very voltage sensitive and current hungry, so they need their own source.
The engine block is already drilled and tapped for a 2nd alt, so I think all I will need to do is install the new alt and battery, ground both to the chassis, run a power wire from the alt to the aux battery and then connect my aux electronics to the battery (using proper connections and fuses of course). My only concern is having a common ground for both systems. Other than that, everything is separate. Is this going to cause a problem? I will have to double check, but I am pretty sure the 2nd alt should have an internal regulator. If not, i will have to include that. Am I missing anything else? Should this work w/o frying something?
Thanks
I am working on an automotive project where I would like to run 2 alternators. The first alternator will be the stock one and drive all of the stock/factory electronics. The second will supply power to a lot of aux electronics.
There are a lot of reasons I want/need to run 2 alts and 2 batteries (basically 2 separate systems) that I don't have time to explain at the moment, so just take my word for it for now. I can explain more if necessary, but it boils down to the aux electronics be very voltage sensitive and current hungry, so they need their own source.
The engine block is already drilled and tapped for a 2nd alt, so I think all I will need to do is install the new alt and battery, ground both to the chassis, run a power wire from the alt to the aux battery and then connect my aux electronics to the battery (using proper connections and fuses of course). My only concern is having a common ground for both systems. Other than that, everything is separate. Is this going to cause a problem? I will have to double check, but I am pretty sure the 2nd alt should have an internal regulator. If not, i will have to include that. Am I missing anything else? Should this work w/o frying something?
Thanks





RE: 12VDC with Dual Alternators
Beside, I think that you'd run into problem trying to find an ungrounded alternator (and other parts of the system).
Stand by for other opinions.
Car stereo - or something more interesting?
RE: 12VDC with Dual Alternators
Possibly.
You may want to run a dedicated ground cable from the alternator to the second battery rather than depending on the chassis ground. Connect the cable to either the alternator body or alternator supports or to the engine block close to the alternator. I have seen cars with a very light ground jumper from the engine block to the chassis. I wouldn't want to depend on that jumper for heavy current. From the sound of the load you're anticipating, you may be well to use a two cable system from the alternator to the battery and from the battery to the load, even though there is a common ground at the engine block.
Hi VE1BLL;
No problem with your post.
respectfully
RE: 12VDC with Dual Alternators
OP can also perhaps put the 2nd battery very near the load (taking into account all the safety precautions, including hydrogen).
Strangely, my car (front engine, RWD) comes stock with the battery in the trunk just behind the right rear wheel. I think they put it there for traction. It's also ideal for a '2000-watt' trunk mounted stereo - if I was still interested in such things.
RE: 12VDC with Dual Alternators
You should include a heavy duty DC fuse rated at your alternator's output. Shorts in these large wires terminated at large energy reservoirs like car batteries pretty much guarantee full involvement car fires that are particularly hazardous to the garage they happen to be parked in when things go sour..
Keith Cress
Flamin Systems, Inc.- <http://www.flaminsystems.com>
RE: 12VDC with Dual Alternators
First you will need to fit a second "alternator" dash warning lamp between the new alternator field terminal and the accessory +12v output of the ignition switch. Otherwise the new alternator will probably not begin to charge when the engine starts.
RE: 12VDC with Dual Alternators
Despite the heavy cable from the battery to the block, there is a smaller strap on many cars connecting the body to the engine block. Try connecting jumper cables from bumper to bumper instead of from block to block. If you have the small strap, you will find it by the smoke!!
P.S. My little diesel is 2.7 L, not much power but great mileage.
respectfully
RE: 12VDC with Dual Alternators
blakrapter; Do heed warp's comment, the dash "idiot light" is often an integral part of the system. No output? Better start checking that.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 12VDC with Dual Alternators
If the bulb blows, then the alternator doesn't start charging.
Something similar happened to me when there was an internal break in the wire to the warning light: no warning light with the ignition on but the engine not running, which I didn't notice... until the battery was so flat that it wouldn't turn the engine over any more... fortunately just outside my garage
You'll need a switch or relay to disconnect the warning light when the engine isn't running or that'll discharge the 2nd battery for you
RE: 12VDC with Dual Alternators
zeitghost, could you clarify what you said about the switch/relay? I am not following why I would need that if its tied into the ignition switch.
Thanks!
RE: 12VDC with Dual Alternators
There are some one wire alternators available that do not need any external source of power to start working.
respectfully
RE: 12VDC with Dual Alternators
blakrapter; Yes do keep in mind a lot of alternators need that bulb doohickey. (%50?)
But the rest do not! Or need something else different. That was a suggestion/reminder for you to actually find out what your specific alternator requires.
Remember a whole lot of vehicle come with ammeters and NO idiot light.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 12VDC with Dual Alternators
RE: 12VDC with Dual Alternators
If you must use an ammeter check these out, I like them.
http://www.cd4power.com/data/meters/dpm_pdb1.pdf
You could use a shunt one and avoid the big wires to the dash.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 12VDC with Dual Alternators
If it's tied to the ignition switch you don't need an extra switch...
RE: 12VDC with Dual Alternators
Try it first, it may not require anything extra if the alternator can self energise. If it doesn't self start, try wiring a second dash "idiot" light back to your ignition switch. I can see no reason why that should not work perfectly. It is pretty basic.
RE: 12VDC with Dual Alternators