Attention distributors/dealers/installers: Adler EF3 fuses Available in the USA

Q&A and troubleshooting
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After quite some time lobbying Adler Electric USA to bring their 36x22mm EF3 fuses to North America, they are now planning to stock them in their Seattle warehouse. If you’re not familiar with these fuses, then search the forum for EF3 fuses or see one discussion here: Fuses and Wattloss on T Class MEGA EF3 and DC Breakers

For those not in the know, these are popular in Europe to replace MEGA fuses in a Lynx Distributor or a Lynx PowerIn with the extra studs added. They are physically compatible with MEGA fuses and bolt right into the Lynx Dist or PIN (not the Class T PIN). For the last year I’ve been running three 200A EF3 fuses in my Victron three phase system that runs my shop with no issues at all. Victron doesn’t support using the EF3 fuses in the Lynx products but that doesn’t mean they don’t work well. I’ve seen one post on this Community that said he had heating issues, but most others have had no issues like me.

The 36x22mm EF3 fuses come in: 100A, 150A, 175A, 200A, 250A, 300A, and 350A current ratings. They are rated for 200-315Vdc (depending on the size) and have breaking capacities up to 50kA. See the datasheet attached to this post for details. They make excellent fuses for lithium batteries, Victron inverter/chargers, and high-current MPPTs such as the 450/200. They also cost less than similar Class T fuses.

EF3 315VDC EV FUSE.pdf (2.0 MB)

If you are a Victron distributor, dealer, or installer and are interested in ordering these for your business, please let me know here or send me a DM and I will provide further information. If you are an end user and want some of these for your own project, subscribe to notifications for this post and you can find the different places to purchase them. It’s going to be roughly 12 weeks from the initial order to receiving them and Adler is trying to determine what that initial order will be.

I intend to design a single fuse holder for use directly at the battery terminal since the EF3 fuse will not fit the Victron MEGA fuse holder. This will be beneficial for Victron NG batteries, 3rd party batteries w/o a built-in Class T fuse, or other high-current sources/loads when a high AIC fuse is desirable.

Please let me know if you are interested and I will talk to you offline.

Thank you

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@OGPS that’s good news indeed. Thanks for the leg work.

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Update, my Adler rep says they make a single fuse holder that will work with the EF3 so we don’t have to make them ourselves.

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I’ve posted a link to this message on diysolarforum.com.
Thank you for doing the work on this, the EF3s look superior in every way to Class Ts.

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Thanks, Rick. I haven’t spent much time on that forum the last few years so it’s appreciated. I don’t know if I can say they are superior in every way but for most of my use cases the EF3 should be a good fit. However, in a permitted and inspected installation, I’d still use fuses the average inspector has a clue about: Class K, Class R, Class T, etc.

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I certainly agree with the permitted and inspected angle.
However, lots of DIY people aren’t in that situation for obvious reasons.

The 50 kA breaking capability should really get people motivated. :grinning_face:

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Would be interested in stocking these, especially if it can help secure a presence for this in the US/North America. Thanks for the footwork on this!

:waving_hand:

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I’d like to share an update and clarify something. In my original post above I stated: “They make excellent fuses for lithium batteries, Victron inverter/chargers, and high-current MPPTs such as the 450/200. They also cost less than similar Class T fuses.”

After reviewing the trip curves with my EE and another distributor’s engineer, we have concluded that the EF3 fuses are ONLY suitable for short circuit protection for batteries and NOT for branch circuit protection. Right in the datasheet it says the UL breaking capacity of 50kA starts at 410% of rated capacity and I missed that important detail. In other words, the fuses won’t open at all until current is more than 4x the rated current, and even then, the time to open is long.

Therefore, EF3 fuses are only suitable for short circuit protection for lithium batteries and do fit in the Lynx products. But, I do not recommend them for any other use. Indeed, for ABYC standards, EF3 fuses might not be a sufficient replacement for Class T fuses at the batteries.

@ricardocello Going back to your comment, aside from size, fitment into Lynx products, and cost, Class T fuses really are better in almost every way to EF3 fuses.

I’m mildly embarrassed to not have caught this myself, but that’s why we have technical review processes. I do think EF3 fuses could be useful to land LFP batteries onto Lynx Power In’s, but I’m going to think on this some more before I recommend their use to DIYers.

@BjoernK I know you have been a proponent of these fuses because they fit into a Lynx Distributor/Power In. Do you have any comments on this?

Thanks!

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I didn’t catch that either! :upside_down_face:

And I don’t believe that is completely true, I’ll post a summary of my thoughts in a few hours.

Their published time-current curves show that they will trip, but they don’t specify the breaking current at anything useful except at 4 In. This is going to come down to what they’ve tested for UL vs. how they can actually be used, I suspect.

I read data sheets all day long, for everything from microcontrollers to mosfets to RF devices. Lots of things look good on paper!
My statements about the EF3s being ideal were based totally on my interpretation of the data sheet. Having samples in the lab and testing them would be the next step to verify what is reality.

I still think they have uses, and will wait to see.
Nevertheless, thanks for doing the work with the manufacturer.

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@OGPS I’ve tabulated some breaking time comparisons for the following fuses: Adler EF3, Littlefuse JLLN Class T, and Littelfuse MEGA 70V, looking only at 300A, 200A, and 100A fuses.

The MEGAs are the fastest acting with the lowest interrupt rating.
The JLLN Class Ts are moderately fast, but nowhere near as fast as the MEGAs for distribution use.
The Adler EF3s are the slowest with the highest interrupt (breaking) rating, but because they condition their spec based on > 4In, we don’t know what the interrupt (breaking) rating is at lower current levels that still exceed the fuse rating (!) I would expect normal 48V battery systems to do really well with the EF3s, as the rating is for 200 VDC, but there is no certified number we can use.

For example, if you put 1000 A through a 300 A fuse, the EF3 will blow in 4 seconds, the Class T will do it in 0.6 seconds, and the MEGA will be 0.7 seconds. Does that really matter? I guess it depends.

My old eyes go nuts looking at log-log plots, so I apologize in advance if I messed up reading the values. Feel free to share this with your engineers.

Screenshot 2026-07-23 at 12.48.49 AM
Screenshot 2026-07-23 at 12.48.49 AM1325×463 86.7 KB

Data Sheets are here:
Adler EF3 posted above
https://www.littelfuse.com/assetdocs/jlln-time-current-curves?assetguid=92e1e140-fc2b-45e6-8729-058e34ad66d1
https://www.littelfuse.com/assetdocs/littelfuse-datasheet-998-mega70v-sf51?assetguid=01891f75-4b5c-40fe-900a-f1b91afc557a

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@OGPS Great to hear you finaly got access to the Fuses in the US. Hard work payed off.

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I think there is one important aspect that may be getting mixed into the comparison.

In modern lithium battery systems, especially LiFePO4 installations with very low internal resistance, the primary challenge is often not the fuse opening time at 1,000 A or similar overload levels. The bigger concern is whether the fuse can safely handle and clear the potentially enormous fault currents that a lithium battery bank can deliver.

In other words, interrupting capacity (AIC/kA rating) is frequently more important than whether a fuse opens in 0.6 seconds versus 4 seconds under a moderate overcurrent condition. A large lithium bank can produce fault currents that are many times higher than the operating current, and a fuse that lacks sufficient interrupt capacity may fail catastrophically even if its time-current curve appears attractive.

For example, with a 48 V lithium system capable of delivering tens of kiloamps into a short circuit, a fuse must not only open the circuit, but do so safely without sustaining an arc or rupturing. That’s where high-interrupt-capacity fuses such as Class T or purpose-built battery fuses tend to have an advantage over automotive-style fuses.

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Thanks @OGPS for this important detail!

I use EF3 to secure +14kWh (280Ah+) battery blocks as they might need an AIC higher than 2kA, which is the rating of standard MEGA fuses. Additionally I use fine strained 50qmm2 silicon wire on each battery block.

For all other circuited like MP2, MPPT… I use normal MEGA fuses.

I thought about using DC NH1 fuses with holders from Jean Müller for TelCo application rated up to 800A at 48/80V but couldn’t source them. I would recommend those for bigger installation.

Thanks again for pointing us to the long timespan until tripping and focusing the EF3 for bigger batteries (16 or 32 kWh blocks) only.

The EF3 have been designed for professional EV charging station. If you need some translation of German document, pls reach out.

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This, to me, is less problematic than that same 300A EF3 fuse not opening for 400 seconds (nearly 7 minutes!) with a 500A load. Wouldn’t the use of EF3 fuses for branch circuits require sufficiently sized wire gauges to sustain this? That would quickly negate the benefits of the EF3 vs the Class T. This is why I think the EF3 fuses can only be relied upon for short-circuit battery protection.

Let’s take this reasoning a step further using the same 300A EF3 fuse installed 1.5m from the Lynx. If the battery itself doesn’t have proper overcurrent protection around 125% of load, then only using an EF3 located in the Lynx is a bad idea. It would require very large cable or a second OCPD to handle the non-short-circuit overload protection.

In my shop we use Epoch Elite V2-T batteries for most mobile/marine at 12V (god forbid), 24V, and sometimes 48V; Pytes V5, V10, and V16 batteries for most 48V applications; and Victron Lithium NG batteries in mobile/marine applications where we need rock-solid control of sources & loads (i.e. controlling an external alternator regulator). The Epoch and Pytes both have high AIC fuses internal to them and the Pytes V10 and V16 also have MCCB’s. So landing them on an EF3 now doesn’t make a whole lot of sense to me. We could use an EF3 in a fuse holder at the terminals for the Victron NG batteries, but at the volume we use those batteries it doesn’t make sense to import EF3 when we could just use Class T.

I’m now second-guessing my entire reasoning for the EF3 fuses in a Victron system. :roll_eyes:

Thank you for summarizing with the table!

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We’re not missing that. It’s the entire point of this thread :slight_smile:

Thanks!

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The original person to catch this was Jim at The Yacht Rigger in Florida. My eyes saw 1.4I on the datasheet and not the 4.1I it actually says! As soon as he pointed that out to me I immediately started to reconsider.

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4 seconds very high current will most likely kill the battery, after 4 seconds call the fire brigade.

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I understand that’s the point of the thread. My comment wasn’t aimed at the overall discussion about EF3 interrupt capacity or the importance of a high interrupt rating. I was responding specifically to Rick’s breaking-time comparison, which seemed to place a lot of emphasis on the differences between the EF3, Class T, and MEGA clearing curves. I wanted to highlight to him that interrupt capacity remains the more important consideration in the overall evaluation of these fuses.

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Gotcha. Thanks for clarifying that for me. It’s been a long week haha

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Agreed! I’d rather not rely on the BMS to detect overcurrent and shutdown.