PWM Confused, please help!

[Goboatingnow]

So just posting to be boastful and irrelevant. Gotcha.

Why not be nice and not an nasty poster. You’re not coming across well

Fusing PV is a compromise some codes require it some don’t. Some applications don’t benefit from it at all. As i said in my case I don’t fuse cause it does nothing.

 

[Substrate]

You just haven been bitten yet.

What you are proposing is running with no panel fuses in a small system, and using large cable so that it in itself doesn't act as a fusible-link when 3 or more panels are used.

It sounds good on *paper*, but there is a reason this over-simplified solution hasn't been promoted for 40 years.

Don't you think that other engineers would have promoted this for the last 40 years or so?. This is not a sudden revelation that every engineer has overlooked. C'mon, I know it hurts - let down the guard, and see if there is something to learn here.

I'm an engineer in another field, and I know we don't like to be confronted. Sometimes not everyone else is wrong.

 

[sunshine_eggo]

You just haven been bitten yet.

What you are proposing is running with no panel fuses in a small system, and using large cable so that it in itself doesn't act as a fusible-link when 3 or more panels are used.

It sounds good on *paper*, but there is a reason this over-simplified solution hasn't been promoted for 40 years.

Don't you think that other engineers would have promoted this for the last 40 years or so?. This is not a sudden revelation that every engineer has overlooked. C'mon, I know it hurts - let down the guard, and see if there is something to learn here.

I'm an engineer in another field, and I know we don't like to be confronted. Sometimes not everyone else is wrong.

Uh oh... that makes three now...

 

[Jchance]

One other thing, can someone tell me what happens in my situation, (with an RV), when I’m either plugged into shore power or running generator power etc.. and my battery is getting charged from One of the sources mentioned above, what does the solar charge controller exactly do when it sees this incoming current charging my battery? I’m assuming it stops any type of feedback, like a diode wood?

 

[sunshine_eggo]

One other thing, can someone tell me what happens in my situation, (with an RV), when I’m either plugged into shore power or running generator power etc.. and my battery is getting charged from One of the sources mentioned above, what does the solar charge controller exactly do when it sees this incoming current charging my battery? I’m assuming it stops any type of feedback, like a diode wood?

Charging from multiple sources

One can have as many independent charging sources running concurrently as they like provided they are programmed properly for the voltage of one's battery bank. Examples (some or all at once, even multiples of a single type, different brands, etc.): Solar PV via MPPT Solar PV via PWM AC-DC...

diysolarforum.com

 

[Jchance]

Thanks, I just have a rinky-dink system,
200 W on the roof, a, (soon to be), 20 amp MPPT charge controller, and one lead acid battery that came with my RV. I’m just looking for those times when my rig is parked and only my refrigerator is on the day before a trip. I am just looking to help my battery state of charge out a little bit. I don’t even have an inverter! I do carry a little solar generator on a handcart just in case, of course it doesn’t run my air conditioning, but that’s not why I bought it.

Thank you.

 

[sunshine_eggo]

Thanks, I just have a rinky-dink system,
200 W on the roof, a, (soon to be), 20 amp MPPT charge controller, and one lead acid battery that came with my RV. I’m just looking for those times when my rig is parked and only my refrigerator is on the day before a trip. I am just looking to help my battery state of charge out a little bit. I don’t even have an inverter! I do carry a little solar generator on a handcart just in case, of course it doesn’t run my air conditioning, but that’s not why I bought it.

Thank you.

What kind of fridge? If propane, run it on propane. Propane fridges on AC use a staggering amount of AC juice.

Can charge with multiple appropriate sources without issue.

 

[Jchance]

What kind of fridge? If propane, run it on propane. Propane fridges on AC use a staggering amount of AC juice.

Can charge with multiple appropriate sources without issue.

Lol, I’m on my 3rd rig with LP/Absorption fridge, I’ve had it with them all! To finicky, can’t deal with the temperature swings, so we are Going to 12V. My wife’s scared to death of all the propane fires she occasionally hears about. She has pushed me “to the 12V side”!

Recently I purchased a small, Changemoore, refrigerator/freezer chest as a backup, and to handle extra food on long trips. It’s powered by 12V/120V and I purchased the optional 12V battery for it and it also has a solar input to charge to battery. It’s the best thing I’ve ever purchased for camping. I also use it for parties at the house, small car trips and outings, it’s amazing ! No more ice to deal with!

 

[Goboatingnow]

You just haven been bitten yet.

What you are proposing is running with no panel fuses in a small system, and using large cable so that it in itself doesn't act as a fusible-link when 3 or more panels are used.

It sounds good on *paper*, but there is a reason this over-simplified solution hasn't been promoted for 40 years.

Don't you think that other engineers would have promoted this for the last 40 years or so?. This is not a sudden revelation that every engineer has overlooked. C'mon, I know it hurts - let down the guard, and see if there is something to learn here.

I'm an engineer in another field, and I know we don't like to be confronted. Sometimes not everyone else is wrong.

My current focus is Marine PV. DC side fusing is extremely rare these would be series parallel system upto about 1kwp My own isn’t fused.

 

[Goboatingnow]

One other thing, can someone tell me what happens in my situation, (with an RV), when I’m either plugged into shore power or running generator power etc.. and my battery is getting charged from One of the sources mentioned above, what does the solar charge controller exactly do when it sees this incoming current charging my battery? I’m assuming it stops any type of feedback, like a diode wood?

Both systems may charge.

 

[Substrate]

My current focus is Marine PV. DC side fusing is extremely rare these would be series parallel system upto about 1kwp My own isn’t fused.

Ok, I get it now. I think you may be carrying over a cross-application to the non-use of solar dc panel fusing a little too far.

Yup - guys running the wrong cable AIC ratings for their DC starting circuits - or using breakers that instead of opening, weld themselves shut! Or using their mondo house-banks for the same starting purpose with a cross-switch. Flaky switches that weld instead of switch - fuse banks that have lots of voltage drop etc etc.

You may or not agree with the ABYC standards, which help expose this problem for a marine installation, but they do seem to recommend using dc-fusing for non-starter circuitry.

DC Circuit Protection - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

So I *think* I know where you are coming from now, but I believe you may be doing a cross-application mixup in regards to the panels.

 

[Goboatingnow]

Ok, I get it now. I think you may be carrying over a cross-application to the non-use of solar dc panel fusing a little too far.

Yup - guys running the wrong cable AIC ratings for their DC starting circuits - or using breakers that instead of opening, weld themselves shut! Or using their mondo house-banks for the same starting purpose with a cross-switch. Flaky switches that weld instead of switch - fuse banks that have lots of voltage drop etc etc.

You may or not agree with the ABYC standards, which help expose this problem for a marine installation, but they do seem to recommend using dc-fusing for non-starter circuitry.

DC Circuit Protection - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

So I *think* I know where you are coming from now, but I believe you may be doing a cross-application mixup in regards to the panels.

The reality is on domestic installations “ code “ is now dominant anyway. So irrespective of the technical reasons or not you will be following code to arrive at a certified system.

Marine system have no such mandatory code anywhere in the world.

My own view is a total panel short is extremely unlikely , secondly given mppt is better with series strings the tendency is higher vojtages and not large arrays in parallel again reducing the panel short current issue.

So I stand by what I says , technically fusing is hard to justify as often it will simply not blow.

 

[Substrate]

Ah, see your application focus is too narrow - good for you perhaps, but can't justify sweeping solutions to fit all.

You probably don't have rats, racoons, possums and other critters on board that like to nibble and play around the wiring. Or a neighbor that goes too far with his roto-tiller and hits your trenched run inside conduit. Or those using what wire they have available, have tight bends, and the UV degradation eventually opens up the casing - all possibilities for shorts on land.

Oh well, I've made my point. One-size solutions do not fit all circumstances.

In fact, it is better to be safe than sorry. What you are promoting may suit *you* fine, but I'm sorry - your recommendations promote an unsafe dangerous practice to 99.9% of the users.

Maybe the Danger-Zone category is best for stuff like this.

 

[Goboatingnow]

Ah, see your application focus is too narrow - good for you perhaps, but can't justify sweeping solutions to fit all.

You probably don't have rats, racoons, possums and other critters on board that like to nibble and play around the wiring. Or a neighbor that goes too far with his roto-tiller and hits your trenched run inside conduit. Or those using what wire they have available, have tight bends, and the UV degradation eventually opens up the casing - all possibilities for shorts on land.

Oh well, I've made my point. One-size solutions do not fit all circumstances.

In fact, it is better to be safe than sorry. What you are promoting may suit *you* fine, but I'm sorry - your recommendations promote an unsafe dangerous practice to 99.9% of the users.

Maybe the Danger-Zone category is best for stuff like this.

Well as long as you technically understand this stuff from first principles you can then do as you please. Electrics/electronics , especially high current high voltage , is not a diy activity in my view. It’s a serious degree level professional engineering discipline.

To many people bolting together supposed building blocks without in-depth understanding or even exposure to local codes and or certified installation processes. It’s even worse on boats and RVs

In my case no parallel panel setup exceeds the panel link current max settings so parallel strings can’t damage each other. Fusing does or nothing in this case.

 

[Jchance]

I kinda get we’re you guys are both coming from, but to be clear, for MY application, if I were to fuse in a 2S2P string, it would only be one on each of the + legs of the Parallel side? However, any system less than a 3 panel parallel string does not need fusing?

Just looking for clarification.

 

[sunshine_eggo]

I kinda get we’re you guys are both coming from, but to be clear, for MY application, if I were to fuse in a 2S2P string, it would only be one on each of the + legs of the Parallel side? However, any system less than a 3 panel parallel string does not need fusing?

Just looking for clarification.

What you propose is fine.

The correct answer is you can have 0-3 fuses.

One fuse only between the MPPT and the paralleled array.
One fuse per string.
No fuses anywhere.
Fuses everywhere.

Literally, do what you want with fusing.

 

[Jchance]

I downloaded the manual to my charge controller. I noticed it does not have a grounding post on it. Should I ground the body of it to my chassis using one of the mounting holes with a cable?