270ah DIY LiFePO4 build

[Poey50]

I gave up trying to get one in the UK. Have fitted a Victron ANL instead, for now. I ordered back in June and was told delivery late July, which then slipped too end of August. My sail-away deadline was 1st August. Seems I did the right thing not waiting...

I'm beginning to think that Class-T fuses are another class of mythical beasts. Had you considered MRBFs instead of ANL? They have a higher amperage interrupt capacity.

 

[Alan S]

I'm beginning to think that Class-T fuses are another class of mythical beasts. Had you considered MRBFs instead of ANL? They have a higher amperage interrupt capacity.

As far as I can find out, MRBF interrupt rating is 10kA, class T is 20kA. I have gone for a 160LET fuse by Cooper Busmann easily available at Farnell in UK and probably cheaper. It is rated at 50kA.

 

[Poey50]

As far as I can find out, MRBF interrupt rating is 10kA, class T is 20kA. I have gone for a 160LET fuse by Cooper Busmann easily available at Farnell in UK and probably cheaper. It is rated at 50kA.

Do you have a link to the fuse holder for that?

 

[Alan S]

Do you have a link to the fuse holder for that?

I used 2 of these:
VTE Positive Power Distribution Post - 6mm, Small Base

 

[Zing]

I'm beginning to think that Class-T fuses are another class of mythical beasts. Had you considered MRBFs instead of ANL? They have a higher amperage interrupt capacity.

I have NH. I mentioned them before. I don't know why they are not favoured? I realise a lot of advice is US based, and these are more of a European standard. Is that it? Dirt cheap to boot.

3NA7836 | Siemens 160A NH00 Fast Acting Fuse HRC Centred Tag Fuse, gG, 500V ac | RS Components

 

[Kelpie]

I'm beginning to think that Class-T fuses are another class of mythical beasts. Had you considered MRBFs instead of ANL? They have a higher amperage interrupt capacity.

I did consider them, and I'm struggling now to recall why I didn't go down that route.
I do remember trying to work out how the voltage at which AIC is given affects things, and that based on this ANL was likely better than it looked on paper for use at 12v.

 

[Poey50]

I did consider them, and I'm struggling now to recall why I didn't go down that route.
I do remember trying to work out how the voltage at which AIC is given affects things, and that based on this ANL was likely better than it looked on paper for use at 12v.

I can't speak for others but, for myself, I'm aware that Class T is going to appear in the ABYC standard - it is already there in the technical advice. While this isn't binding on Europe it is often the case that authorities follow each other. Surveyors and insurers then follow these benchmarks. So by fitting Class-T I am confident that no-one will require me to change it to get insurance in the future. And I've gone for Bluesea following a recommendation from Rod Collins who has done more testing on fuses for marine installations than anyone I know.

 

[Kelpie]

I will likely change to Class T if I can ever get my hands on one.

For now I believe my ANL is sufficient to handle the pack safely enough.

Given the concerns over AIC, I do wonder if it would be possible to create a fuse which consists of a spring, enclosed in a casing. When it burns through, the remaining wire recoils to open up a larger gap, preventing arcing.

Thoughts?

 

[starfire]

I will likely change to Class T if I can ever get my hands on one.

For now I believe my ANL is sufficient to handle the pack safely enough.

Given the concerns over AIC, I do wonder if it would be possible to create a fuse which consists of a spring, enclosed in a casing. When it burns through, the remaining wire recoils to open up a larger gap, preventing arcing.

Thoughts?

Exactly what NH fuses do & they are sand filled to extinguish the arc.

Breaking capacity seems to be at least 25kA or half the rated AC capacity.

 

[Poey50]

Given the concerns over AIC, I do wonder if it would be possible to create a fuse which consists of a spring, enclosed in a casing. When it burns through, the remaining wire recoils to open up a larger gap, preventing arcing.

Thoughts?

I wouldn't like to DIY it!

 

[vas]

We in the UK for a bit if you can find someone you can order from I can give you an address to have it sent to and I forward it on to you if that's any good .

thanks for the offer Vic, looks like I'll skip T class and go to Zing's suggestion, might even be able to get them locally! will have a look.

cheers

V.

 

[vas]

interesting NH 250A fuse, 9euro. Mount with M10 connectors 25euro. Both ordered locally will have them next week
rather bulky, pity they don't do the nice 3PH plastic moulted mounts in 1PH :-(

Specs identical (if not better!) than the T-class ones, price a fraction, what not to like?

cheers

 

[Pete7]

slightly confused, so Pete, you have the FLA always online (in parallel to the LFP) and occasionally get the LFP offline to fully charge the FLA or have I got that wrong?

cheers

Yes.

 

[sailaboutvic]

Being away from the boat at the moment I been interested in emails I had from several cruisers who are changing to lithium .
All four are cruisers we known for some years and at less 3 out of the 4 are quite knowledgeable when it comes to 12v and batteries.
There are all fitting 12v set up 400ah to 560ah
Here the interesting part ,
They plain not to use a BMS , instead use their victron mppt and b2b to monitor hight and low voltage,
Use cell monitors to keep an eye what each cells doing .
Connect the cells to a active balance board .
Considering the cost of BMS this could be a cheap way forward .

What's the view ?

 

[vas]

what are these cell monitors? how many amps can the active balancer board shift? how much does this setup cost?

the diyBMS that I decided upon costs something like 200euro for 5 control boards (cannot order one PCB from china!) and 10 modules that fit on top of each cell.
and some time to solder a few bits that are not available to be soldered atm

not sure I'd dare go bare on this tbh! and they must have a LA or whatever bank standby if something goes horribly wrong, no?

so victron mppt says all's fine 13.5 and one cell is at 3.8 active balancer is not fast enough shifting current about, what do you do? what decides to take the whole bank off line? the active balancer?

 

[sailaboutvic]

So I understand the active balancer they going to use will put 1A from one cell to a lower cell.
Rather then just burning off .

The cell monitors are just displays they don't do anything but show what each cell is at,
so there no protection .

Judging from mind set up my charge rate is 13.8v and now and then I rise that upto 14.0v
At 13.8v all 8 cells are spot on at 14.0v two cells will very slight start to drift but not to the extend I need to worry (0.03 v) only at 14.2v a different of (0.10v) 14.3v two cells will hit 3.65v .
So keeping then to max of 14.0v there isn't any chance of a miss happen especially since they being used all the time .
Of cause there a chance of something going wrong but BMS can also go wrong .

Taken in considering all four are full time liveaboard and like most liveaboard are monitoring everything from What coming out to what's going in I think it could be a solution to expensive BMS .

I think if someone is charging to max 14.4v , it wouldn't be some thing I would use,
but charge to a lower rate as I do and cells that are match the risk aren't that hight .

If my smart 123 packed up I think I would give it a go.

If I wasn't on board full time I probably stick to a BMS .

It be interesting to see how the others get on with it .
Any more views?

 

[vas]

Vic,
what you describe seems OKish assuming cells are rather well matched. Wont work if not, fullstop!
further if slightly unbalanced, you'll have to "throttle" charge so that the 1A shifting about active balancer can cope, how much? no idea but doubt a 20A charge with unbalanced cells will enable the balancer to keep things proper.

Not a fan tbh.

V.

 

[Kelpie]

I'd be wary of going without a BMS. Mine cost about £65 and I can pull 120A through it. It's not a huge expense in the scheme of things.

 

[sailaboutvic]

I'd be wary of going without a BMS. Mine cost about £65 and I can pull 120A through it. It's not a huge expense in the scheme of things.

Mine cost me just under £350 .
Smart 123
It doesn't regulate how much I can use ,
my breaker does that , all the BMS do is monitor cell <> and if any cell goes over the setting it signal the breaker to trip.
Max use at any one time as been 230A

 

[sailaboutvic]

Vic,
what you describe seems OKish assuming cells are rather well matched. Wont work if not, fullstop!
further if slightly unbalanced, you'll have to "throttle" charge so that the 1A shifting about active balancer can cope, how much? no idea but doubt a 20A charge with unbalanced cells will enable the balancer to keep things proper.

Not a fan tbh.

V.

Yes agree you need to have matching cells .

Knowing these guys their cells will all be match and top balance .