ANL fuse vs Circuit Breaker

[JimF]

Hello all,

Newbie here. I am connecting a BattleBorn 100A battery to serve as backup for twp Pieces of medical equipmen. I also want to have the capability to use a 1000 watt pure sine wave inverter. I was going to put in a 100 amp breaker, or 100 amp ANL fuse along with battery shutoff. This will feed to a distribution block where I’ll connect the charger and MPPT controller, each with their own breaker.

Question is: The BattleBorn manual says to use an ANL fuse, yet I have ready many places that a circuit breaker would be better and the breaker could do double duty as a shut off switch to disable all battery power if needed (only after first turning off solar and AC chargers first). Is there a valid argument for ANL fuse vs Circuit Breaker? Or will either one work OK?

Safety is highest priority.

Thanks, JimF

 

[time2roll]

I would go with the ANL and skip the switch. I go years without disconnecting the battery and simply unbolt one of the cables if needed.
Switch mostly just adds resistance and another fail point. JMHO

 

[sunshine_eggo]

The bigger consideration is the AIC rating of the OCP (over-current protection). LFP batteries can deliver massive current that can overwhelm the fuse/breaker and prevent them from protecting the circuit.

In most cases, Class T fuses, which have an AIC rating of 20,000A, are used for LFP.

BB may recommend ANL because they have computed the max amps based on non-public information. A breaker may be fine, but it needs to have the same AIC rating of an ANL fuse.

 

[JimF]

I would go with the ANL and skip the switch. I go years without disconnecting the battery and simply unbolt one of the cables if needed.
Switch mostly just adds resistance and another fail point. JMHO

Thanks @time2roll & @sunshine_eggo. I’m also read that class T fuses have much higher Amp Interruption Capacity (AIC) and are fast. I found one thread here that recommended putting class T fuses on both positive and negative terminals. I don’t know how fast the Battleborn Battery BMS shutdown is for a dead short, but it reads that it allows 200 A for 30 seconds and anything higher for 1/2 second. That concerns me so I want a hard 100 Amp limit. I’ll call battleborn to double check on the ANL fuse recommendation, however I think I’ll buy the Class T 100 A.

 

[JimF]

Thanks @time2roll & @sunshine_eggo. I’m also read that class T fuses have much higher Amp Interruption Capacity (AIC) and are fast. I found one thread here that recommended putting class T fuses on both positive and negative terminals. I don’t know how fast the Battleborn Battery BMS shutdown is for a dead short, but it reads that it allows 200 A for 30 seconds and anything higher for 1/2 second. That concerns me so I want a hard 100 Amp limit. I’ll call battleborn to double check on the ANL fuse recommendation, however I think I’ll buy the Class T 100 A.

I assume best to attach the class T fuse directly to battery terminal, then to battery shutoff switch?

 

[time2roll]

it reads that it allows 200 A for 30 seconds and anything higher for 1/2 second. That concerns me so I want a hard 100 Amp limit. I’ll call battleborn to double check on the ANL fuse recommendation, however I think I’ll buy the Class T 100 A.

Check the Class-T interrupt chart on Blue Sea. Shows close to a minute at 200% rating.

https://www.bluesea.com/products/5112/Fuse_A3T___Class_T_110_Amp

 

[JimF]

Thanks for the link @time2roll. 60 seconds at 200% seems a bit dangerous to me since It could overload the wiring. Do I need to upsize everything to handle 200-400 amps? That will be some expensive any unwieldy wire. Maybe both 110 A Class T fuse and a breaker? Have to locate that same type of % overload vs reaction time chart for breakers. If the breaker AIC isn’t enough and it arcs then the class T should eventually blow.

Renogy ANL fuses show similar (or longer) time delays … https://www.renogy.com/content/files/Manuals/ANL-Fuse.pdf



Thx, Jim

 

[JimF]

Blue Sea 285 series breakers are marginally better response time than either Class T or ANL fuses. They are rated for between 10 and about 35 seconds @ 200% current, though AIC rating is only 3000A @ 48v - no idea if that changes for 13.4v. So I might use both a fuse and a breaker on the positive side.

https://www.bluesea.com/products/7187/285-Series_Circuit_Breaker_-_Surface_Mount_100A

 

[time2roll]

I would stay with the BB recommendation.

 

[JimF]

Thx. I’ll call BattleBorn tomorrow and document what they say here.

 

[JimF]

Battleborn support says today that the BMS shuts down 100% @ 250A. They recommend an ANL or MEGA fuse type, along with a separate battery cutoff switch over circuit breakers. They recommended I upsize my cable leading to the primary distribution block from 4 AWG to 2 AWG for 1000 watt inverter loads. The support rep only knew of Blue Sea that offers “bolt-to-terminal” ANL fuse holders, but also recommended to just use a short jumper to an inline ANL fuse holder. I’ll have circuit breakers between primary distribution block for the charger, for the inverter, and for the downstream Blue Sea 100A ATO fused distribution panel. BattleBorn said my plan sounds OK. Let me know if anyone disagrees with this approach. Thanks!

 

[sunshine_eggo]

What happens when the BMS fails and there is no short circuit protection? Will an ANL or MEGA adequately protect the circuit?

 

[JimF]

Yes, thanks @sunshine_eggo, that is exactly my concern. According to BattleBorn this morning, yes an ANL fuse provides enough protection, however there are many downstream components that can’t handle 150 amps, let alone 200 amps, for 30 seconds if they fail and short out or, as you point out, the BMS fails to shut down at all. I still have my concerns. I am now researching fast-blow fuses as another option. MEGA fuses can spark and provide an ignition source. MEGA fuses appear to also have less AIC ratings. The BattleBorn rep stated he didn’t feel that circuit breakers are as reliable, especially when serving double duty as an on/off switch.

 

[time2roll]

MEGA fuses can spark and provide an ignition source.

May want the Blue Sea ignition protected holder. https://www.bluesea.com/products/7721/MEGA___AMG_Safety_Fuse_Block

Shop around

 

[John Frum]

Yes, thanks @sunshine_eggo, that is exactly my concern. According to BattleBorn this morning, yes an ANL fuse provides enough protection, however there are many downstream components that can’t handle 150 amps, let alone 200 amps, for 30 seconds if they fail and short out or, as you point out, the BMS fails to shut down at all. I still have my concerns. I am now researching fast-blow fuses as another option. MEGA fuses can spark and provide an ignition source. MEGA fuses appear to also have less AIC ratings. The BattleBorn rep stated he didn’t feel that circuit breakers are as reliable, especially when serving double duty as an on/off switch.

What is downstream that can't handle 150amps for 30 seconds?

 

[JimF]

Even the Eaton “fast blow” Class T fuses appear to have even worse delays. I can’t easily format the AH vs time chart on my iPad, but the graph is here: https://www.eaton.com/content/dam/e...circuit-fuses/class-t/bus-ele-ds-1025-jjn.pdf. My search continues. I’d rather have a very fast fuse knowing that it limits my startup inrush current for devices plugged into the inverter (like motor startup).

 

[time2roll]

What happens when the BMS fails and there is no short circuit protection? Will an ANL or MEGA adequately protect the circuit?

Has anyone tested a MEGA with a LFP dead short at 12v or 24v? I am OK with MEGA used in conjunction with the BMS.

 

[JimF]

I called to speak to a tech engineer @Easton who verified I am reading the time-current load cart correctly. 300 seconds is way too long for a overload shutdown. He recommended a current sensing circuit/relay. This starts to get way more expensive and complex than I planned for. Am still searching for a simpler solution.

 

[JimF]

What is downstream that can't handle 150amps for 30 seconds?

@smoothJoey - Wires/charger/controller …. Any device can sort out or fail and draw excessive current. It depends on the device’s tolerance, but having a fuse that allows double overcurrent for up to 300 seconds seems excessive and a danger to me. The MPPT controller, AC charger and the two medical devices I need to provide backup power to (CPAP machine and O2 concentrator) will obviously have much smaller fuses than the main 100A fuse on the battery, however it appears all fuses, even “fast blow” have significant delays in an overload condition. Yes, I know I’m being overly cautious In the opinion of many people.

 

[JimF]

Has anyone tested a MEGA with a LFP dead short at 12v or 24v? I am OK with MEGA used in conjunction with the BMS.

@time2roll, why MEGA vs ANL if ANL has higher AIC rating? Blue Sea chart does appear to show the MEGA has a faster response for overloads > 150% …

MEGA® / AMG® Fuse - 300 Amp - Blue Sea Systems

Use with MEGA or AMG fuse blocks to create an economical system for 100 to 300 Amp circuit protection

www.bluesea.com