I have been finalizing the system design for a grid-tied project I am planning, and I am double-checking the battery protections. Most worldwide regulations (like ABYC) and European standards (where I am based) state that lithium battery banks must be protected by a fuse capable of stopping a catastrophic short circuit (i.e., a highly rated interrupt capacity). This can be achieved using a Class T fuse or an NH fuse, which is more readily available in Europe.
My battery box came with a CHINT CRT36-00 250A NH fuse and holder. While this should be fine in theory, it comes from a Chinese supplier, so I am weighing how much I want to trust it as my sole line of defense. Because of this, I was planning to use a Lynx Class-T Power In since it integrates beautifully into the Victron ecosystem.
However, I have been reading everywhere about this product, and there seems to be a lot of confusion around its true purpose and legal compliance. If standards require a fuse to be placed as close as 7 inches (~17cm) from the battery terminal, how can this Power In practically be used?
From a quick read of the codes, regulations also specify that if the cabling is fully enclosed and protected via conduit, a larger distance of up to ~1.8m is acceptable. This leaves me with two questions:
Is relying on that 1.8m conduit exception the only intended way to legally use the Lynx Class-T Power In?
If my battery had no internal NH fuse nearby, would a setup relying solely on the Lynx Class-T Power In (with a sheathed cable of less than 1.8m) be considered acceptable and safe?
Does anyone know what is victron stance on this topic? Some people online are highly opinionated that the Lynx Class-T Power In doesn’t actually fulfill its intended purpose since it’s rather unpractical to place this busbar really close to the batteries.
I would argue that it is a thing, that does what it is advertised to do - eg, it is a large busbar with two positions for Class T fuses.
Where you put the thing, and how that relates to whatever standards apply to your particular governing jurisdiction, is up to you / your installer.
If the Power In cannot be placed close enough to the battery bank to meet the applicable codes, then you or your installer must place OCPD devices closer to the battery bank to meet the applicable codes.
Certainly. However, let’s approach this logically. Victron is a highly respected brand known for producing practical, high-quality products. Offering a product that is intended for a particular function but lacks practical utility would be contradictory.
Considering this is ultimately a safety device, it’s in everyone’s best interest to ensure these are installed correctly and serve their true purpose. This aligns with other company products that also come with specific safety guidance.
Sure, but there is practical utility. It is a high-current busbar, with positions for 2 high-current (225-400A) Class T fuses. That’s quite a practical product.
It is up to your installer to ensure that the product is installed in a manner that complies with your local governing codes and regulations, it is not up to the manufacturer - Victron has no idea what codes or regulations may apply to you, and won’t make any specific recommendation with regard to that in most cases.
The lynx system was introduced when mobile installations in cars and boats where the main focus for victron. While you surely have regulations there as well, they can vastly differ to the ones in grid-tied installations nowadays.
Depending on whether you are charging or discharging, a battery is either a power source or a sink. Additionally, if you connect multiple batteries to a busbar, currents can flow between them.
Ideally you place a fuse on the battery, or close to it, and then again on the busbar, to protect the wiring inbetween. Since a short circuit on the cable connecting the battery to the busbar can be fed from both directions, once from the battery thats directly attached to it, and once from all the sources connected to the busbar.
Sounds like a local rule, so you would need to specify your location and then wait for someone that knows this specific local code. Or ask a local electrician.
If those 1.8m are according to your local code, then yes. You have done what the code is asking you to do, so in that regard the installation is safe. Anything additional can make things safer, but its not a guarantee. Depends on the exact situation.
You can substitute the Lynx Class-T by a Lynx for Mega-fuses, if you use Adler EF3 instead if Mega-fuses.
This gives you four ports per Lynx instead of two.
Adle EF3 are designed for EV charging stations and rated to clear 50kA.
As @BjoernK few of us use have utilised the Lynx in this way with those fuses but I’m sure it’s only the M8 one that these fit? I could be wrong though
Thank you for the suggestion, but the distance issue remains whether I use a Class T fuse or an EF3, which is exactly what motivated this thread. Additionally, in my region, they cost almost exactly the same. Since an EF3 fuse is significantly slower to clear a short circuit than a Class T, I would much rather stick with the Class T. My core question is still about how to manage the physical distance requirement.
My reading of the standards is that they seek to mitigate battery risks when they are installed in more exposed scenarios.
If you install the batteries within secured compartments (deliberately using vague terminology here - compartment could mean almost anything that protects access to the batteries by people and risks that could damage the battery and cables) then the standard relaxes the requirement, and thats why they say one should provide additional cable protection between the battery and the fuse, and if you do that then up to 1.8m is the maximum.
And with that in mind the Lynx Class T In is a valid solution to aggregate your batteries neatly towards the BMS.
In industrial switchgear like motor control cabinets there is a standard IEC forms of separation of components (form 4b for e.g.) which seeks to achieve similar things. By compartmentalising things safety is added.
Anyway, thats might take on it. But then what do I know, Im just a guy.
You are quoting ABYC standards which are for mobile marine installations where stress from pushing through waves, storms plus engine vibrations are a real issue increasing the risk of short circuits especially if you have a metal hull due to fretting / chafing / fatigue, hence the limited lengths and/or double sheathing between the battery and the fuse. The same type of rules apply to boats in Europe through ISO standards. You can not use these standards for a stationary grid tied system, you need to find what standards apply in your location.
First thing is ABYC is a suggestion and many of their “standards” are subject to change with input from supporting companies.
Second thing is we make something to get well beyond this issue in our best practices.
I manufactur a bus bar style adapter to a class T fuse holde with a bus style adapter to a heavy battery switch.
Our copper battery bar is huge in comparison to other stuff we’ve seen and at 1 x .25 inches carries over the 400 amps the largest fuse could handle which is higher than the rating of 4/0 cable in most applications.
Our suggestion is to have a fuse and a switch for each battery bank.
Inquire at SBCSMARINE.com if you need help figuring out your needs and getting the right products
It’s not that difficult. Every single Lifepo4 battery needs a AIC or ICC, Europa, rated fuse. Therefore victron products are great except the lynx. In my opinion you can’t use those with multiple Lifepo4 batteries in parallel. I would never use the lynx, but place a single Class-T, ANL or NH fuse, depends on the capacity, close to the positive terminal and use proper busbars to go further in the system. Much smaller and safer that way.
OGPS
(Ed @ Off-Grid Power Systems - offgridps.com)
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The Lynx Class T is useful in fixed installations where the LFP batteries have high AIC fuses located inside the case that are hard to get at or use circuit breakers for OCPDs. The circuit breaker on the battery - in my opinion - should not be the primary means of protecting against a short circuit. But it’s super handy to use as a mechanical disconnecting means.
In mobile situations, if the batteries are located directly below the Lynx with only 12-24" or 0.5m of cable from the terminals to the cLass T fuse then I think it’s fine so long as the cables are sized appropriately to handle continuous current before the class T fuse can blow. If the cables are longer then I’m more inclined to fuse directly at the terminals. In the USA, look at the Epoch Elite V2-T models or use a device like @Boatsb1 mentioned. The issue is space above the battery, but there will always be constraints that need to be designed around. FWIW, I’m not a huge fan of the BMS in the Epoch Elite batteries, but I really like the physical case and replaceable Class T fuses built in to the case. That’s terrific for many marine and RV applications that don’t need a more sophisticated BMS with external ATC/ATD control lines.
And yes, the EF3 fuses fit an M8 or M10 Lynx Distributor or a modified Lynx PIN. The trouble is getting EF3 fuses in North America. I’ve looked into importing them and distributing them in the USA but that’s a large financial commitment and risk I’m not willing to bite off on. I’ve talked to other distributors about pairing up to do it, but it’s a 3 month lead time to receive product for every order, which means stocking even more. The Adler USA rep did send me four of them from Germany to test and I like them a lot, but with the dumba** tariff policy from our dumba** administration it’s very costly to import them from a German distributor. In North America, we’re better off with Class T fuses for time being. Hopefully the situation changes.
