Choosing fuse vs circuit breaker

[KevK]

I'm adding a 2000 watt inverter to my camper and am debating wether I should use a fuse and a cutoff switch or a breaker. Here are my thoughts. The inverter is a 2000 watt GP electric inverter and the documentation recommends 00 cable size and a 300 amp fuse. I picked up a terminal block fuse and was going to go with one of the boat style high current switches but then I came across two breaker options.

The top left photo is an example of the terminal fuse. I have a 300 amp version. I will need to add a master switch.

Next are two circuit breakers. I like the concept of the circuit breaker where you insert the wire directly into the breaker and eliminate the need for a ring terminal as that all reduces voltage loss, however, the 300 amp breakers like that only accept up to a 1/0 gauge wire. I could trim down the wire to make it fit at just the connection but that seems a bit iffy to me.

The circuit breaker with the posts is more common but then I'm adding in more ring terminals and it seems like the more convoluted connection would lead to more loss.

I read in the forum (sorry I forgot the user's name) that a fuse is preferable for inverter circuits as breakers have a higher voltage loss. Is that why I only see fuses on inverter manufacturer sites?

Thanks for your input. Fuse or circuit breaker?

[SeaDog]

I can't imagine that the voltage loss from the type of terminal used would of any significance when compared to all the other connections on an RV. I think I would go with what ever the industry standard is. JMHO

[babock]

Circuit breakers have more voltage drop across them than a fuse which is why most inverter companies recommend fuses. Inverters don't like low voltage so in order to avoid the low voltage cutoff to be hit, you want to use the fuse over the circuit breaker.

It's also why AGM and lithium work so much better with inverters. They have much lower internal resistance than a FLA battery for the same reasons.

[Jeffjeeptj]

Go with a fuse, but, keep a spare or two. Also, don’t just install another fuse, figure out the problem first. I’m sure you know about electricity but, as a remonder, periodically you need to do preventive maintenance and tighten and/or clean your terminal connections. Those are the locations where energy is lost.

I worked in the Power Generation business until I retired. We had a lot of reliability issues with “molded case” breakers especially when used near the Manufacturers’ limit. When we had something critical a fuse was used, unless there was something special about starting amps vs. running amps
As stated above, inverters are sensitive to input voltage.

[TitanMike]

When I was in college I was taught that circuit breakers were better for circuits that had a lot of surge loads. Fuses (other than the "Slo-Blow" type) were pretty much an immediate interruption where circuit breakers had varying amounts of delay to allow for the current peak to pass.

Remember though, my college days were back at the beginning of the 1960's so lots of things no doubt have changed although I'm sure simple fuses still pop quicker than most basic circuit breakers.

I know that circuit breakers are favored by those who run electric trolling motors and also in marine applications.

[KevK]

Thanks all. Based on majority input, I'm going to go with the fuse I have and get a cutoff switch. The inverter will have a dedicated lithium battery (modified Chevy Volt battery) so wiring is simple. I'm keeping the original house battery on a separate circuit for the other 12v loads. I have to keep them separate as they have different charge profiles. The fuse I have is the one in the top photo and isn't slow burn but at most I'm running the microwave so I'm not even coming close to the 300A and should be ok.

And yes, I will keep a couple extra fuses.

[TitanMike]

Originally Posted by KevK

Thanks all. Based on majority input, I'm going to go with the fuse I have and get a cutoff switch. The inverter will have a dedicated lithium battery (modified Chevy Volt battery) so wiring is simple. I'm keeping the original house battery on a separate circuit for the other 12v loads. I have to keep them separate as they have different charge profiles. The fuse I have is the one in the top photo and isn't slow burn but at most I'm running the microwave so I'm not even coming close to the 300A and should be ok.

Very interesting. I own a Chevy Volt and wondered how long it would be before someone used it for powering up an RV.

As for stored energy there's around 17 kwh versus the 1.2 kwh stored in an average 12v battery that you can only access half of.

I think the battery pack in a Volt weighs around 350 lbs and runs at 360 volts.

I can charge mine from "empty" to "full" in 4 hours with the level 2 charger I installed in my garage which consumes around 3500 watts.

Share what you've done to modify the battery to fit your RV. If I were to tackle a project like that I'd look at it more like an solar system setup running 48 volts into an inverter. Higher voltage reduces size requirement on wires and accessories like chargers and Inverters are more and more available today than in the past. Of course the higher DC voltage does introduce some very important safety considerations but there's a lot to like.

[babock]

Chevy Volt modules are 48V 45AH. The Nissan Leaf and Tesla modules are used more often in RVs. For small trailers like mine, I prefer LiFePO4 for safety. If I had a 5th wheel and wanted to run AC, I would use the Tesla modules.

[KevK]

Originally Posted by TitanMike

Very interesting. I own a Chevy Volt and wondered how long it would be before someone used it for powering up an RV.

As for stored energy there's around 17 kwh versus the 1.2 kwh stored in an average 12v battery that you can only access half of.

I think the battery pack in a Volt weighs around 350 lbs and runs at 360 volts.

I can charge mine from "empty" to "full" in 4 hours with the level 2 charger I installed in my garage which consumes around 3500 watts.

Share what you've done to modify the battery to fit your RV. If I were to tackle a project like that I'd look at it more like an solar system setup running 48 volts into an inverter. Higher voltage reduces size requirement on wires and accessories like chargers and Inverters are more and more available today than in the past. Of course the higher DC voltage does introduce some very important safety considerations but there's a lot to like.

I only use a small part of a Volt battery pack. It was originally a small 24V section but has been rewired to be 12. I picked it up on eBay last year from a guy who modifies new Volt batteries and resells them. I was originally just going to replace the house battery with the 100 amp hour (1.2 kWh) Volt battery and run everything I needed on 12v but changed my mind and decided I wanted to use my microwave when boon docking.

The battery is small so I can fit the inverter and battery in some free space I have in the kitchen cabinet. If I knew I was just going to power only the inverter when I bought the battery I would have gone with an un-modified 24v section but with a 12v battery I have the option of getting a 2 battery switch which will give me the option of running the 12v trailer system on either battery.

Here is a link to the eBay seller who I purchased the battery from. I bought the 12v 100 amp hour version with a BMS. (if the link doesn't work, search eBay for "chevy volt battery 12v"):

https://www.ebay.com/str/Lith-ion-Ba...p2047675.l2563

$600 for a 12v, 1.2 kWh battery with a BMS (cheaper without). You can pick up a used 24v, 50 amp hour (same size as mine but twice the voltage so both store about 1.2kWh) for $220 from other sellers. The module I'm using is only 20 lbs and is 9.5"W x 5" L, x 10.5" H so it fits where I want it to go.

For charging, I have a couple 100 watt panels I lay on the ground for now and a Victron 75/15 controller. I picked that controller as it has bluetooth and I'm able to set the correct charging parameters.

I figure I don't need a whole lot of storage as I'm not running much and I did replace all my interior lights with LEDs so not much usage there either.

I also picked up a buck converter for my truck which will convert the truck's 12v to 48V. I'm wiring the 48v (250 watts) to an Anderson connector on the truck's bumper. From there I'm running a line from the bumper to the Victron solar charge controller so I can also charge the Chevy Volt battery while I'm driving.

[babock]

So...I don't hear you saying anything about a BMS on this battery. If you don't have a BMS, you are going to be in huge trouble.

BTW, a buck converter is a step down voltage converter. It won't convert 12V to 48V.

I also don't see where you have 48V in your system. Your battery was rewired to be 12V I thought!

EDIT:See you say it has a BMS. Did you have that in there before?

[babock]

Here is a guy who actually knows what he is doing with a Li-Ion pack(tesla). Has a BMS and still had an issue.

https://www.youtube.com/watch?v=of01p0Q-yUM

[KevK]

I just noticed an issue with my system. The seller updated his listing for the 100A 12V battery to say that the maximum charge and discharge rate is 25 amps. I suspect that this is because the jumper he used in the modification is fairly small gauge. The un-modified 24v 50 Ah battery he lists shows a continuous current of 240A and a peak of 350A. Looks like I need to figure out an alternative. Sigh.

[babock]

Originally Posted by KevK

I just noticed an issue with my system. The seller updated his listing for the 100A 12V battery to say that the maximum charge and discharge rate is 25 amps. I suspect that this is because the jumper he used in the modification is fairly small gauge. The un-modified 24v 50 Ah battery he lists shows a continuous current of 240A and a peak of 350A. Looks like I need to figure out an alternative. Sigh.

That may also be a function of the BMS which is on the battery you have. The BMS may be what is limiting the current more than likely.

My suggestion, unless you are an EE or have a lot of experience with these types of battery systems, buy a LiFePO4 battery with a built in BMS.

[KevK]

Originally Posted by babock

So...I don't hear you saying anything about a BMS on this battery. If you don't have a BMS, you are going to be in huge trouble.

BTW, a buck converter is a step down voltage converter. It won't convert 12V to 48V.

I also don't see where you have 48V in your system. Your battery was rewired to be 12V I thought!

EDIT:See you say it has a BMS. Did you have that in there before?

Yes I did have it in there that I have a BMS. They also make step up Buck converters. You have to look hard to find them as most are step down converters. But alas, looking at specs for the battery (I bought mine a year ago and just used it for a 150 watt inverter to run my tv, the specs for the 12v 100 Ah battery say 25 amp charge/discharge max probably because of the small gauge jumper wire the guy installs. The 24v, 50 Ah version can be discharged at a much higher rate because of the tabs that connect the pouches have a lot of surface area. Sigh, looks like I may need to downsize my inverter. Back to just the TV and computer.

Edit: The 48v from the truck goes to the solar charge controller which properly charges the battery. As others have noted, I had a momentary brain lapse and it isn't a buck converter but a boost converter.

[babock]

You are talking about a boost converter. Buck converters only step down.

Does the 24V 50AH battery also have a BMS?

[KevK]

Originally Posted by babock

That may also be a function of the BMS which is on the battery you have. The BMS may be what is limiting the current more than likely.

My suggestion, unless you are an EE or have a lot of experience with these types of battery systems, buy a LiFePO4 battery with a built in BMS.

Thanks. For now I may just go with the lead acid in front and skip the inverter and lithium. No microwave and just run the computer and tv off a 150 watt inverter I already have.

[babock]

Go with a LiFePO4 battery!

[KevK]

Originally Posted by babock

You are talking about a boost converter. Buck converters only step down.

Does the 24V 50AH battery also have a BMS?

Sorry. Momentary brain short circuit. Yes a boost converter. Some of the 24V 50Ah batteries have BMS and some don't. The specs he list are the same but the seller could be in error. I sent the seller a question asking if it is the jumpers or the BMS that is the limiting factor.

As for using LiFePO, I don't have the room where I want it to go so for now, I'm just going to stick with my current 150 watt inverter which is enough to run my tv and computer. If I go with the LiFePO and the 2000 watt inverter I would have to put it under the bed and run the 120v to the transfer switch or run an extension cord to the shore plug. The 12v lines from the battery box to distribution panel aren't sized to support an inverter and the inverter should be located near the battery anyway.

[babock]

Originally Posted by KevK

Sorry. Momentary brain short circuit. Yes a boost converter. Some of the 24V 50Ah batteries have BMS and some don't. The specs he list are the same but the seller could be in error. I sent the seller a question asking if it is the jumpers or the BMS that is the limiting factor.

As for using LiFePO, I don't have the room where I want it to go so for now, I'm just going to stick with my current 150 watt inverter which is enough to run my tv and computer. If I go with the LiFePO and the 2000 watt inverter I would have to put it under the bed and run the 120v to the transfer switch or run an extension cord to the shore plug. The 12v lines from the battery box to distribution panel aren't sized to support an inverter and the inverter should be located near the battery anyway.

Personally, I would not be putting one of those Lithium Ion vehicle batteries in a living quarters of a trailer. If I did, that battery better be be on the opposite side of the trailer where the bed is with an exit door in between. LiFePO4 on the other hand are a different animal altogether. I have mine under my bed.

[Larry-NC]

Originally Posted by KevK

Thanks. For now I may just go with the lead acid in front and skip the inverter and lithium. No microwave and just run the computer and tv off a 150 watt inverter I already have.

Okay, you've scaled the project back. But I have a question about the original scheme.

You presented three pictures of protection options: a fuse and two 300 amp circuit breakers. You discussed them as equivalent options. Did you realize that the fuse was a 75 amp fuse in a holder that could accept up to 300 amps?

Larry