Solar controller as an el- cheapo smart regulator?

[Compass790]

Question for someone with more electrical knowledge than me which is most of the people on here.
We have a Bosch 55amp alternator which has a 14.7 volt setpoint internal regulator on it. I'm wondering if I can leave that regulator on the alternator & run the output from the alternator thru a 60 amp PWM solar controller to get 3 stage battery charging for say US$20 instead of say US$200 for a smart external regulator?
Reason I want to add the solar controller is to drop the voltage to the 13.5v that the solar controller has as its float voltage when the battery is fully charged. We dont often run the engine for long but
Just accept I'm cheap & give me a reason why it's electrically not wise or impossible rather than say just buy a balmar please. I'd like to learn something from your explanation.
Thanks for your help in advance

[Dsanduril]

Don't do it! From a theoretical point of view a PWM controller basically just opens and closes a switch very rapidly (gross oversimplification) which is the last thing you want to do with an alternator under load. Good way to ruin the alternator's rectifier (the voltage spike that occurs when opening the switch while the alternator is generating exceeds the diode's breakdown voltage).

Never done it though, so would love some real-world experience to say that the PWM pulse width is so narrow that the alternator wouldn't be hurt. Don't imagine that's the case, but willing to learn new tricks.

[Compass790]

Originally Posted by Dsanduril

Don't do it! From a theoretical point of view a PWM controller basically just opens and closes a switch very rapidly (gross oversimplification) which is the last thing you want to do with an alternator under load. Good way to ruin the alternator's rectifier (the voltage spike that occurs when opening the switch while the alternator is generating exceeds the diode's breakdown voltage).

Never done it though, so would love some real-world experience to say that the PWM pulse width is so narrow that the alternator wouldn't be hurt. Don't imagine that's the case, but willing to learn new tricks.

Whilst I love experimenting you've frightened me already. If I had a spare diode bridge I'd have a go maybe but I don't.
I understand your point & thanks.
Hope more weigh in, maybe someone has already tried it?

[Wotname]

If the alternator diodes survive, the spikes might take out the solar regulator. I'm sure the solar regulator is not designed to handle large inductively generated pulses.

Plus you would need to be certain from where your existing internal regulator senses it's target voltage otherwise the two regulators will be eternally slugging it out.

[Compass790]

Originally Posted by Wotname

If the alternator diodes survive, the spikes might take out the solar regulator. I'm sure the solar regulator is not designed to handle large inductively generated pulses.

Plus you would need to be certain from where your existing internal regulator senses it's target voltage otherwise the two regulators will be eternally slugging it out.

Thanks Wotname,What about putting solar controller on the field wire then & just using the brushes, bypassing the internal regulator? Feel free to laugh as my electrical knowledge is very limited. At least I'm down to blowing up a $6 solar controller instead of a rectifier bridge then.
I can see a problem as the voltage will be the same on both sides of solar controller so will the circuit be open or closed? Normally it's 19v going in frm solar panels & battery 12.6 or so.

[newhaul]

My question is where are you finding a solar controller that can handle 55 amps input for 20 bucks?
The best I can get a 60 amp one is 75 bucks from renogy .
Unless you are charging Lfp banks you will not have any issues with your Fla bank . To charge from 80% go a full 100% would take several hours running the alternator.

[Compass790]

Originally Posted by newhaul

My question is where are you finding a solar controller that can handle 55 amps input for 20 bucks?
The best I can get a 60 amp one is 75 bucks from renogy .
Unless you are charging Lfp banks you will not have any issues with your Fla bank . To charge from 80% go a full 100% would take several hours running the alternator.

https://www.aliexpress.com/item/30-4...643c2e0emDsv6n

Now there are a few things I've learn't about buying from China. Quality is variable to say the least. Item descriptions are often false. I prefer to buy off Ebay if I can find the same stuff as you can use paypal & Ebay has better refund service.
Doubt the solar controller example I posted is an MPPT but I'm not qualified to judge.
I have got some good buys too tho. It's a lottery on AliExpress but it's in my budget.I would buy local or US made if I could afford it
Our bank is 225amp 6v in series FLA but we sometimes have them full on solar @ 0930 & I'm a bit concerned the alternator reg setpoint of 14.7 is too high when they are full. Of course I can just not turn it on ( we have field wire switch ) but I'd rather have smart alternator for cheap.

[Compass790]

Originally Posted by newhaul

My question is where are you finding a solar controller that can handle 55 amps input for 20 bucks?
The best I can get a 60 amp one is 75 bucks from renogy .
Unless you are charging Lfp banks you will not have any issues with your Fla bank . To charge from 80% go a full 100% would take several hours running the alternator.

Forgot to say when buying chinese electronica buy 2x the capacity that you actually need.i.e. if you need a 10amp solar controller buy a 20amp as they are marginal at best at their rated capacity.
Guess how I know?

[ohgary]

Problem with PWM is your only going to get out of your panels what your battery's are rated for. So a 100 watt panel is typically 18v at about 5.5 amps. In a PWM system going to a 12v battery bank your 5.5 amps are still there but its at 13.8v so your around 75 watts. IN a MPPT system you get the full 100watts to the battery bank.(minus some wire loss).

[Compass790]

Whoops just saw this re 20$ solar controller!!!!!!
https://www.aliexpress.com/item/Plea...AbTest=ae803_3

[Wotname]

Good spotting!!!!!

[newhaul]

Originally Posted by Compass790

https://www.aliexpress.com/item/30-4...643c2e0emDsv6n

Now there are a few things I've learn't about buying from China. Quality is variable to say the least. Item descriptions are often false. I prefer to buy off Ebay if I can find the same stuff as you can use paypal & Ebay has better refund service.
Doubt the solar controller example I posted is an MPPT but I'm not qualified to judge.
I have got some good buys too tho. It's a lottery on AliExpress but it's in my budget.I would buy local or US made if I could afford it
Our bank is 225amp 6v in series FLA but we sometimes have them full on solar @ 0930 & I'm a bit concerned the alternator reg setpoint of 14.7 is too high when they are full. Of course I can just not turn it on ( we have field wire switch ) but I'd rather have smart alternator for cheap.

ok first I actually deal a lot with Chinese manufacturers. Not sales people .
So yes always get bigger than needed. Now as to the specific controller you linked to .
They are not good quality . I would not recommend spending the 40bucks on them. ( remember shipping)

[newhaul]

Originally Posted by ohgary

Problem with PWM is your only going to get out of your panels what your battery's are rated for. So a 100 watt panel is typically 18v at about 5.5 amps. In a PWM system going to a 12v battery bank your 5.5 amps are still there but its at 13.8v so your around 75 watts. IN a MPPT system you get the full 100watts to the battery bank.(minus some wire loss).

Gary he is looking to use a solar controller as an alternator voltage regulator.
Which I don't recommend. Doing

[Compass790]

Originally Posted by newhaul

ok first I actually deal a lot with Chinese manufacturers. Not sales people .
So yes always get bigger than needed. Now as to the specific controller you linked to .
They are not good quality . I would not recommend spending the 40bucks on them. ( remember shipping)

na it was free shipping but I bought a different one as it had a 2 year warranty ( good luck with that though is my experience) https://www.aliexpress.com/item/30A-...10ee4c4dZAmo63 There are heaps for sale on Ebay too.
This is a 30amp but we only need a 12 amp for our solar system. I will use our existing 20amp controller on the alternator if I experiment but still waiting for more input from electrical experts. Wanted a spare solar controller anyway.

[RaymondR]

It might actually work.

What all alternator regulators do is vary the rotor current to control the field output current and voltage. Pre electronic regulators this was done by opening and closing mechanical switches with a solenoid so one might say it was switch mode control. However due to a degree of hysterisis the rectifying diodes experienced pulsating current levels rather than a series of spikes.

If you could rig the solar regulator to independently sense the battery voltage and have that control the rotor current it might work.