270ah DIY LiFePO4 build

[Poey50]

thanks, well mine is not a capacity meter then
looks like it's called battery tester:
BT175 Digital 12V Battery Tester
nice and expensive bit of kit to test batteries will keep it for engine & genny starter then!

cheers

Yes, the ones I linked to replace the 20 watt bulb, notepad and clock method. They hold the amperage constant and record everything for you. It makes C/20 testing (or whatever) a doddle. You can set the voltage to end the test. Very pretty too with the green LEDs.

 

[gregcope]

I've got a spare if you can wait ten days 'till I'm home. But they don't cost much and I think you'd use more than once.. I've capacity tested the individual cells with mine as well as the pack. Also easy to test lead acid capacity. I expect to use mine to check on any decline in capacity of my LFP as the years pass.

Good points. And if they are only £30 thats probably most of the cost of posting one backwards and forwards.

Thanks for the offer, butI think your logic wins out.

 

[gregcope]

Would this T fuse work?
https://www.mouser.co.uk/ProductDetail/Littelfuse/JLLN200X?qs=WtG364jHAdxuq3QzCozJog==

Or rather what spec are we looking at for a T class? I understand it needs a certain amp rating (e.g. 200A) and an interrupt rating (this one has 20ka)

 

[noelex]

Would this T fuse work?
https://www.mouser.co.uk/ProductDetail/Littelfuse/JLLN200X?qs=WtG364jHAdxuq3QzCozJog==

Or rather what spec are we looking at for a T class? I understand it needs a certain amp rating (e.g. 200A) and an interrupt rating (this one has 20ka)

Yes, that T class fuse looks fine.

The fuse rating needs to be matched to the wire size (or other components that need protection such as the BMS) that it needs to protect (or lower, depending on the expected load).

You also need a suitable fuse holder.

 

[gregcope]

Quick response @noelex.

25mm Cable. 170A. BMS around 130A max.

So 150A is probably a better.

 

[gregcope]

Like this one;
https://www.mouser.co.uk/ProductDetail/Littelfuse/JLLS150X?qs=bpnLQM2ZShwvuWrCK5i4lQ==

 

[Poey50]

Following on from Noelex's comment, one of the reasons I understand for Class T recommendation is not just the suitability of the fuse but also the fuse holder in a marine setting.

I've just been notified that Cactus will be delivering my fuses and holder tomorrow so supplies must have finally got through.

 

[gregcope]

@Poey50 good for you.

Can you share any logic of the T class fuse holders being better in a marine setting? Ie why?

 

[noelex]

Quick response @noelex.

25mm Cable. 170A. BMS around 130A max.

So 150A is probably a better.

To calculate the maximum fuse rating you ideally need to take into account the cross sectional area of the conductor, the wire insulation temperature rating, whether or not the wire is bundled, and if it passes through an engine space. This is complicated, but the details do make a significant difference.

As a simple answer, a 150A fuse on a 25mm2 cable is probably resonable.

 

[Poey50]

@Poey50 good for you.

Can you share any logic of the T class fuse holders being better in a marine setting? Ie why?

I'm not any kind of authority on this and, as is probably apparent, always at the edge of my knowledge. But that is what I heard, I think from an authoritative source which frequently means Rod Collins.

 

[noelex]

The T class fuse holder from marine companies such as Blueseas is nearly identical to the equivalent ANL fuse holder. The only apparent difference is the slightly different contact spacing to suit the length of the T class, or ANL fuse. This is 61.72mm for ANL fuses and 46.74mm for T class fuses.

However, the T and ANL fuses themselves are of different construction. The advantage of T class fuses is their high IC rating. The drawbacks of T class fuses are their high cost, limited availability, limited current range and non ignition protection rating, nevertheless these fuses are worth considering especially for lithium battery banks.

 

[Poey50]

The T class fuse holder from marine companies such as Blueseas is nearly identical to the equivalent ANL fuse holder. The only apparent difference is the slightly different spacing to suit the length of the T class, or ANL fuse.

However, the T and ANL fuses themselves are of different construction. The advantage of T class fuses is their high IC rating. The drawbacks are their high cost, limited availability, and limited current range and non ignition protection rating, nevertheless these fuses are worth considering especially for lithium battery banks.

Just to add to my previous comment, the fuse holder issue - as I understand it, is because Class T has a more suitable fuse holder than other industry fuses that have an equivalent amperage interrupt current rating, not because the fuse holder is any way better than other marine types of fuse holders.

 

[gregcope]

What are peoples thoughts on just bolting a T-Class to a suitable ring connector? I saw this on one install.

 

[noelex]

What are peoples thoughts on just bolting a T-Class to a suitable ring connector? I saw this on one install.

Rather than a wire and ring connectior bolted to the ends of a T class fuse an oversized solid copper bar (rectangular cross section) is perhaps a better solution. This constuction provides some heat disipation for the high currents that might be anticipated where a T class fuse is warranted.

Copper bar is inexpensive if you want to construct your own "fuse holder".

 

[gregcope]

Its possibly an issue of space rather than cost, although i cannot visualise what you mean @noelex

 

[mitiempo]

Blue Seas has 2 different class T fuse holders. The first is similar to the ANL fuse holder - the cover can be hard to remove. The second type which is newer is a big improvement.

 

[mitiempo]

Here is the better type of class T fuse holder

https://www.bluesea.com/products/5502100/Class_T_Fuse_Block_with_Insulating_Cover_-_225_to_400A

 

[Poey50]

Blue Seas has 2 different class T fuse holders. The first is similar to the ANL fuse holder - the cover can be hard to remove. The second type which is newer is a big improvement.

Interesting information. Thanks.

 

[Zing]

I did mention up thread that NH fuses are a good and reasonable cost alternative to the not especially easy to get US style fuses. I don’t understand why they are not being sought.

 

[Poey50]

Here is the better type of class T fuse holder

https://www.bluesea.com/products/5502100/Class_T_Fuse_Block_with_Insulating_Cover_-_225_to_400A

My fuse-holder arrived today - finally - the old-style one unfortunately. Neither I, nor Cactus, had been aware that there were two kinds. As well as the cover being pretty crude, more significantly, the new style advertises itself as 'ignition protected'.

Edit: Cactus have a lead time of around 20 weeks for the new-style which based on recent delays is just this side of never. I'll stick to the old style. I suspect 'ignition protected' may refer to the fact that the fusing has now been tested rather than any change of design.