What size resistor for inverter fire-up?

[OldJimbo]

I saw Will use a resistor to eliminate the spark when first feeding power into an inverter. I’m going to buy a 24v inverter - around 2000 watts or maybe 1500, depending on the best price I can find at the time. Looking at Amazon resistors, I’m seeing from 1 to 1 million ohms. Help?

 

[noenegdod]

You dont need a resister. You can use anything that will provide resistance to current. I have used a 12v heating pad and a 120v incandescent light bulb

 

[rmaddy]

The following resource has some good info on this:

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

There are also several existing threads on pre-charge resistors that will answer this.

Search results for query: pre-charge resistor

diysolarforum.com

 

[Smokin]

25 ohm is ok. I use light bulb 2 12volt in series. Yeah what he said.

 

[corn18]

I used a 6 ohm 50 W resistor. I used that one because that's what they had at the auto parts store. It's in the light section and it's called a LED load resistor.

 

[OldJimbo]

This:

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

comes through as Hieroglyphics on my phone.

 

[rmaddy]

This:

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

comes through as Hieroglyphics on my phone.

What looks bad? Simply clicking on that link or clicking on the Download button after clicking on that link? It all works fine on my phone. The Download button will load a PDF.

 

[OldJimbo]

It’s the Download button.

ªUkŠ_»µ¦zµ¦žEwh ʇ—ÄŒœ|)áÂJð—r‡‹h .u #ƒ·ì«‘Ưâ|¿Aò¥=§GCÃ{¿òWa²/ø7 u]ÿ´áɸÔhˆ3µ=§'ôÕ+üyA«Ù4KùDá„Ð…åg+¤p5š€ äV<Àù¨GÁÇpÇV[KLkûÔ±nkÝkëgsÇ.[·Aùß²u!ÉÂØý¸×ôoä^²ÝuÝî[{³m+¹âG{tyÏm3«ò-/Éêf5½f=¦r¶™µJ,‚ã[ƒfòëyzE"¢$vlÖ¶u´ß/¯DàÜXë¯ï¦ÌjßQCs*™\òÍÁ×”Ìi/k"À›Ô'KÌล5èŒ?@Uy–*LÇùŸÄæŽë´˜Ð¤ešG%ðrÞÃ|½îÓÆéœØDÞ¥Œaßú§—m]8z?Ôà‰•‡=„I–3TÚ4ž:Ô¶I>ÎùÝšk‚ú¿ËBï7Eß!¢v‘o¤°Ò°hžÞ`zP¯©"„¬På™sª!]Ø8«ýŽUƒ 'µ+

I’m sure it’s not the link, it’s my phone. Still, I can’t find the “Translate Sanskrit” button.

 

[rmaddy]

The Download button triggers the download of a PDF file. If your phone doesn't support that then you'll need to do it on a computer.

 

[Jp0311]

The following resource has some good info on this:

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

There are also several existing threads on pre-charge resistors that will answer this.

Search results for query: pre-charge resistor

diysolarforum.com

I’ve been reading these post about resistors and not finding the answers I’m looking for (don’t want to assume and mess something up).

I have a gowise 1500w inverter and 12v LiFePO4 100ah battery I connected with 2awg cable. It sparks when I connect them as expected. What size resistor do I need and how would I figure this out for future so I don’t have to ask again as I upgrade system? Still new to all of this.

Thanks.

 

[THUDGUN]

I made this little device. 10W 20Ohm cement resistor...

 

[JoeHam]

I use these :

Amazon.com: YiePhiot 2PCS 50W 25 Ohm Resistor Aluminum Case Wirewound Chassis Mounted Compatible with Ring Doorbell, Nest Hello Doorbell, SkyBell Doorbell Etc : Industrial & Scientific

Amazon.com: YiePhiot 2PCS 50W 25 Ohm Resistor Aluminum Case Wirewound Chassis Mounted Compatible with Ring Doorbell, Nest Hello Doorbell, SkyBell Doorbell Etc : Industrial & Scientific

www.amazon.com

At $5 a pair I keep some laying around for whenever they may be needed.

 

[rmaddy]

I’ve been reading these post about resistors and not finding the answers I’m looking for (don’t want to assume and mess something up).

I have a gowise 1500w inverter and 12v LiFePO4 100ah battery I connected with 2awg cable. It sparks when I connect them as expected. What size resistor do I need and how would I figure this out for future so I don’t have to ask again as I upgrade system? Still new to all of this.

See the following document. It shows resistor sizes for a given voltage. The wattage of the inverter is irrelevant for choosing the resistor.

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

 

[THUDGUN]

See the following document. It shows resistor sizes for a given voltage. The wattage of the inverter is irrelevant for choosing the resistor.

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

I really like that dial design. Simple, effective and hard to use improperly. I think I'll go with that design over my pushbutton design.

 

[Jp0311]

See the following document. It shows resistor sizes for a given voltage. The wattage of the inverter is irrelevant for choosing the resistor.

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

diysolarforum.com

Thanks. I take it I need to use a 25w resistor with ohms ranging between 3 and 12 for my 12v system? I have no clue what any of this means, but hoping it makes more sense once I start playing with the resistor and reading more.

 

[time2roll]

1 ohm per volt will limit current to 1 amp. 2 ohms per volt will give half an amp as max. 5w is plenty at these levels. By the time it gets warm the event will be over.

 

[Al D]

Thanks. I take it I need to use a 25w resistor with ohms ranging between 3 and 12 for my 12v system? I have no clue what any of this means, but hoping it makes more sense once I start playing with the resistor and reading more.

It's probably best if you try learning about this before diving in. This is semi-expensive equipment that you can damage if you don't connect things properly. Not to mention the hazard to your physical safety.

If you want to "start playing" then I would suggest getting a few LEDs and resistors. You should be able to wire up a simple circuit before even thinking about trying to wire up a mini power station.

Per your question, here is my anecdote: I have a 3kW inverter hooked up to a 24V battery bank. I used a tractor resistor (high wattage) bought from one of the big auto shops. I remember it sparking just a little when I made the connection. I want to say the resistance was only a couple ohms. I used rubber gloves and eye protection. I try to be reasonably safe.