I have installed solar panels on top of my RV to charge batteries. The solar charger is certified to 150vdc at 30amps input. The 300w of solar panels puts 60vdc at 8 amps. What I would like to do is full bridge rectify the AC from the trailer power and use (2) 600vdc 20amp solid state relays to switch between Solar Panel input - DC input from rectified AC service. I have a SPDT to switch that will turn on one solid state switch or the other, never both at once. Will this work?

 

That sounds like a good way to let the smoke out or worse, kill someone.
Why not just use a professionally mains connected solar charger?

These are pretty cheap and work well. I got mine on Ebay and they will have 110V versions. (I'm in Australia where we have 240v)

EDIT: I'll have to check if this has isolation, but I would think it does.

 

That sounds like a good way to let the smoke out or worse, kill someone.
Why not just use a professionally mains connected solar charger?
View attachment 155394
These are pretty cheap and work well. I got mine on Ebay and they will have 110V versions. (I'm in Australia where we have 240v)

I think you have misunderstood what the TS wants to do.

The vehicle has solar panels that can handle 60Vdc at 8A – which are used to charge the vehicle battery at 12V.

I think what the TS wants to do is replace this 60Vdc at 8A solar panel supply, with rectified mains.

If the mains supply is 120Vac, the rectified voltage will be at 170Vdc, whereas the charger is only rated to 150Vdc – plus the isolation between the input at 170Vdc and the 12Vdc out is unknown.

Don’t do it.

 

That is exactly what I thought he wanted to do.
DO NOT rectify the mains!!!
Use a battery charger with isolation.
Probably the inverter I mentioned is overkill, when an off the shelf battery charger is all that is needed.

 

I think you have misunderstood what the TS wants to do.

The vehicle has solar panels that can handle 60Vdc at 8A – which are used to charge the vehicle battery at 12V.

I think what the TS wants to do is replace this 60Vdc at 8A solar panel supply, with rectified mains.

If the mains supply is 120Vac, the rectified voltage will be at 170Vdc, whereas the charger is only rated to 150Vdc – plus the isolation between the input at 170Vdc and the 12Vdc out is unknown.

Don’t do it.

You are correct. I have a solar charge controller. It is a new MPPT controller with max 150vdc input. I wasn't aware 120 rectifies to 170vdc. Can you explain why this would not rectify to 120vdc? Safety is my first concern but my electrical drain at night will draw the batteries very low and cannot always rely on the sun to charge them up fully.

 

Can you explain why this would not rectify to 120vdc?

The AC mains voltage is always specified as Vrms.
The RMS value of a sinewave is 1/√2 times the peak waveform voltage.
This means the peak voltage is √2 * 120 = 1.4 * 120 = 168V.
A rectifier and capacitor connected to the AC will charge up to near this peak voltage, giving a DC output of around 165V.
Below is a simulation of a simple AC circuit with rectifier.
Note the measured RMS value (small window) of the AC is ≈120Vrms while the DC output is near 170V.



I agree with the others, that your best solution is likely to buy an off-the-shelf mains battery charger and just switch between that and the solar inverter.
Any other type of direct mains connection is problematic and dangerous.

 

You are correct. I have a solar charge controller. It is a new MPPT controller with max 150vdc input. I wasn't aware 120 rectifies to 170vdc. Can you explain why this would not rectify to 120vdc? Safety is my first concern but my electrical drain at night will draw the batteries very low and cannot always rely on the sun to charge them up fully.

It is also very possible that if you were to implement such a charging system, the chassis of the vehicle would be at mains potential – with a high probability that anyone touching the vehicle metalwork would receive a fatal electric shock.

 

All are valid points. I will continue to use the on board 12vdc charging system and merge the 12vdc output of the MPPT solar charger to the same 12v posts on the battery. As I said safety is my first propriety. Thank you for your help.