Tell me about smart alternators + connecting a solar panel

[Lorgar]

Hey all,

Here's my current situation.

I have a Prado 150 with the 3.0L TD engine and conventional alternator. Connected to the starter battery I have a 30w solar panel running via an MPPT controller to maintain the battery on long camp trips etc.

That all works fine, because the alternator just provides the steady charge and the MPPT fills in some gaps and keeps the battery in float while at camp for days.

In a few weeks, I'm picking up my new truck which comes with the more recent 2.8L TD engine with smart alternator.

I get the gist of the smart alternators but haven't been able to find an exact answer on if I can run my solar panel in the same way on it.

Obviously, the smart alternator is monitoring the battery and charging it as it deems appropriate, but it will not be aware of the solar panel, so I'm not sure if this will cause confusion.

I've read some conflicting info that the smart alternator measures the voltage of the battery, and others that it measures the resistance of the battery to determine the appropriate charging.

If it monitors voltage, that's going to be a problem because the solar panel will be feeding 13-14 volts, giving the alternator the impression the battery is full.

If the alternator measures the resistance of the battery, I don't think I've got a problem.

Anyone got a more comprehensive understanding of how a smart alternator would interact with the solar input?

Cheers.

[Oldbloke]

"If it monitors voltage, that's going to be a problem because the solar panel will be feeding 13-14 volts, giving the alternator the impression the battery is full" (whilst driving)

Yes, that's my understanding.

But I know just enough to be dangerous.

You could fit a manual isolation switch on the panel/controller but that would be a PITA.
Perhaps one that isolates the panel when the ignition is on?

Be careful what you read on the www. A lot of misinformation. Everyone wants to be an expert.

My strong suggestion is talk to an auto electrician. Preferably one that has been recommended to you. May be better in the long run.

When I'm camping I just plug a 200w blanket into a controller fitted in the tray whilst parked. Keeps my auxiliary battery charged and runs my 40ltr fridge.

[Oldbloke]

Just remembered. I've heard that if your lucky, some of the smart alternators can be "switched" back to work like the old dumb type.

But could be BS.

[noneyabussiness]

ok... the " smart " alternators are just that, most take internal resistance and voltage + load and a but load of other stuff to work out charge algorithms... your 30w panel will make absolutely no difference to it when your talking 100s of amps ( in most cases 100-200 amp) that your alternator will put out... It will be perfectly safe...

[on_one_wheel]

https://www.redarcelectronics.com/au/re ... od-redarc/

In not a fan of all that new rubbish, so much unnecessary bs that does very little other than add complexity and extra fail points.

[noneyabussiness]

the old shunt regulator on the back of em has worked well for Many years... if it ain't broke...

[Lorgar]

You could fit a manual isolation switch on the panel/controller but that would be a PITA.
Perhaps one that isolates the panel when the ignition is on?

That's my plan B of sorts. I was doing to do a slide cover of some sort on the panel itself. While driving with the cover on, the solar would be generating 0 PV, so the MPPT wouldn't be feeding power.

When I'm camping I just plug a 200w blanket into a controller fitted in the tray whilst parked. Keeps my auxiliary battery charged and runs my 40ltr fridge.

I have the same for my Aux, that's no problem.

I have this small panel for the starter just to top it up after load from lights from doors being open, UHF radio being left on at camp, etc.

[Lorgar]

your 30w panel will make absolutely no difference to it when your talking 100s of amps ( in most cases 100-200 amp) that your alternator will put out... It will be perfectly safe...

Yep, I'm aware the current from the 30w panel will be pretty inconsequential. From memory, it only puts out 1.6amp max in full sunlight.

It was just the voltage specifically I was concerned about, and if the alternator would see 14+ volts from the panel and take that above all else as a sign the battery was full.

[Oldbloke]

Lorgar,
Do you have an auxiliary battery and/or fridge?

[Lorgar]

Lorgar,
Do you have an auxiliary battery and/or fridge?

Yep.

Starter battery > BCDC charger > auxiliary battery > power box > fridges, phone charging, inverter etc.

On the starter battery I've got an MPPT controller and fixed 30w panel permanently mounted on the roof.

On the auxiliary battery I've got an MPPT controller and Anderson plug, and 2x 300w solar blankets; I either plug in 1 blanket, or 2 in parallel depending on the weather/load.