Multiple Voltages
Multiple Voltages
(OP)
I have a personal project I'm working on and wanted to run it by the experts. I have a truck that has a split 12v and 24v electrical system. It currently uses two 12v alternators, one with isolated ground, to charge each battery individually. I want to convert it to a single 12v alternator to charge one battery and use a 12-24v converter to charge both.
Here is my crude sketch.

Please be critical.
I would use a 12v-12v isolation power supply to charge the second battery but I can't find such a device available. Current is ~100 amps.
An alternate plan was to use a relay to alternate the battery being charged. If I add a capacitor in parallel with each batter and cycle the relay at high frequency I may be able to do this without causing the headlights to flicker.
Here is my crude sketch.

Please be critical.
I would use a 12v-12v isolation power supply to charge the second battery but I can't find such a device available. Current is ~100 amps.
An alternate plan was to use a relay to alternate the battery being charged. If I add a capacitor in parallel with each batter and cycle the relay at high frequency I may be able to do this without causing the headlights to flicker.
RE: Multiple Voltages
RE: Multiple Voltages
TTFN (ta ta for now)
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RE: Multiple Voltages
Sourcing a 24v alternator shouldn't be too challenging and the 24-12 converters are commercially available.
While I've never seen a converter used to charge a battery we do use "power supplies" as chargers successfully. The key is to get the right voltage output. You want 13.6 or 27.2 volts out of the supply to properly charge a flooded lead acid battery system.
This is going to be my fun truck and nothing ruins fun like breaking down. I agree that the 24v alternator is the wisest route. The 24 volt alternator is way more expensive is why I avoided the idea but now I see the step down converter is much less expensive than the step up.
RE: Multiple Voltages
RE: Multiple Voltages
You want get more power out of that alternator remaking the power to 24 Volt?
I am assuming that batter 1 12V is for the normal running of the car and that batteri 2 together with batteri 1 is for some contraption "toy" you have on it.
So how the loading will affect the batteries has very much to do with how often you intend to use this toy compared to how much you just intend to drive it.
Lets say the alternator is 100 A and each batteri 100Ah, it will take 2 hours to fully load the batteries if there is no consumption.
If you start of with 2 fully loaded batteries and you are just running the car Batteri 1 (12V) lets say it will go between 60 and 100 Ah (I am just making this numbers up)
Batteri 2 will stay fully loaded.
When you then start using your toy, lets say that you hade bat1 60Ah, bat2 100Ah you will have bat1 80Ah and bat2 80Ah (24V)
So when you have finished with that, both batteries will be loaded simultaneously and depending on how much is left in them the time needed just depends on how much you have taken out.
So loading 12 Volt or 24 Volt isn't so important just how many hours and how many Amps.
“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein
RE: Multiple Voltages
RE: Multiple Voltages
But I can't tell as you have not included enough information.
We do all sorts of voltage changes with AC, and a transformer. Then again, I assume you are using an automotive alternator, which I believe is a three phase/six diodes.
RE: Multiple Voltages
RE: Multiple Voltages
My I initial reasoning behind the 12 volt charge and 24V supply was that most of the electrical load is 12V and the 24V is only an intermittent load for starting.
RE: Multiple Voltages
Or buy one that is hell for stout, like this
https://www.trcelectronics.com/View/Mean-Well/RSD-...
They do make smaller ones also.
Or these
https://www.ato.com/dc-dc-buck-converter-24v-to-12...
And the 24V is the most critical part, if it doesn't start then nothing else matters.
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RE: Multiple Voltages
Depending on how many cylinders there are, it should be quite possible to configure these into some manner of concatenation that obviates any requirement for ballast resistors, for example any vee six cylinder Diesel, two groups of three glow plugs in parallel on each bank of cylinders could be wired in series, such that each group of three receives 12 volts when 24 volts are applied end to end.
It would also in my view not be all that difficult to wire an unbalance relay with two voltage-actuated coils wired subtractively, such that if any one glow plug burns open a voltage unbalance would appear whenever the plugs were energized; the pick-up of this relay could serve to annunciate as a "glow plug failure" alarm, giving prompt warning of such and minimizing the likelihood of burning out the remaining good glow plugs.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Multiple Voltages
RE: Multiple Voltages
http://www.gonefcon.com/trucktcom/parallel_sw.htm
https://www.texasindustrialelectric.com/T_114_12_s...
12V loads are connected to battery A.
RE: Multiple Voltages
That series parallel relay could work. It would have to cycle off and on a few times with the glow plugs but that should be fine.