Idiot's guide to a self build battery

[Joeboy]

That’s ok. I was wondering after reading through the thread, you mention that sometimes the eve batteries are the only ones providing the power as various voltages are passed. Does that still happen after the initial balancing? I’ve quite a large inverter and that would mean a lot of current (187 amps) through one set of cables to the eve extension whilst waiting for the pylon tech to join in again. At the moment I have it set up for 47 amps per pair of pylontech on the original cables.

I'll be honest and say I haven't checked for yonks. I'm quite basic so every few days I check cables by hand for heat and they have never been more than mildly warm. I am 3.6 to 3.9kW limited in draw.

[Andy]

This makes me worry that the ones on ebay might be fakes and to be honest this seems like a part of the build I shouldn't risk it on. So rather than resettable breakers, which just seem like adding more things to go wrong, I'll simplify to using link fuses: https://www.12voltplanet.co.uk/P00523.html along with a holder https://www.12voltplanet.co.uk/victron- ... older.html. Haven't bought these yet but do have in basket so if anyone has better recommendation please do shout

A bit late to this one. Some of the mega fuses are only rated to 32V so you have to be a bit careful in selection.

[AlBargey]

A bit late to this one. Some of the mega fuses are only rated to 32V so you have to be a bit careful in selection.

Yes only the higher rated 58V Mega Fuses can be used on a 48V system, but they don't have a high enough AIC rating for LFP @ 48V, so we should still have either a T class, BS88 or NH fuse for arc interruption.

[Andy]

A bit late to this one. Some of the mega fuses are only rated to 32V so you have to be a bit careful in selection.

Yes only the higher rated 58V Mega Fuses can be used on a 48V system, but they don't have a high enough AIC rating for LFP @ 48V, so we should still have either a T class, BS88 or NH fuse for arc interruption.

Oh, all my pylon tech are only fused with 58V mega on the Victron Lynx distributor. Do you mean the 32V aren't enough, or do you include the 58V as well?

If you mean the 58V ones, then what is the point in them if they don't break the arc?

[AlBargey]

Oh, all my pylon tech are only fused with 58V mega on the Victron Lynx distributor. Do you mean the 32V aren't enough, or do you include the 58V as well?

If you mean the 58V ones, then what is the point in them if they don't break the arc?

The 58V Mega Fuses will work fine (for a 48V Nominal system) under normal circumstances, but they cannot quench the Amperage Interrupt Capacity (AIC) of a short circuit, which with LFP can be around 10,000A+, so it's desirable to have a main fuse/s that have a high AIC rating, the T class being a Semiconductor fuse, will also blow so quickly it should protect an inverter from a massive short circuit, but T class are expensive, I've made the choice to go for NH fuses main fuses for the batteries and inverter, and just use the Lynx PowerIn as a simple busbar without fuses to minimise resistance.

[Joeboy]

Al,
This is a really good site. Thanks for bringing it.

https://eu.nkon.nl/eve-lf280-prismatic- ... fepo4.html

I am going to go with Deriy for the next set and match to my current set. So it will be 16 LF280k's V3 with M6 connector and fingers crossed Grade A. One spare left over tween the 30 units and hopefully little extra cost to install. I'll end up with enough home storage for half charge of EV if needed. All ini'll expect less stress and even cooler packs at the end of this.

Sorry Colin, the shipping costs killed it.

[Andy]

https://eu.nkon.nl/eve-lf280-prismatic- ... fepo4.html

Seems like the quote button only gives pick up from the Nederlands s an option

[Andy]

The 58V Mega Fuses will work fine (for a 48V Nominal system) under normal circumstances, but they cannot quench the Amperage Interrupt Capacity (AIC) of a short circuit, which with LFP can be around 10,000A+, so it's desirable to have a main fuse/s that have a high AIC rating, the T class being a Semiconductor fuse, will also blow so quickly it should protect an inverter from a massive short circuit, but T class are expensive, I've made the choice to go for NH fuses main fuses for the batteries and inverter, and just use the Lynx PowerIn as a simple busbar without fuses to minimise resistance.

Thanks Al. That’s a great explanation though I now feel obliged to go and spend some money to make it safe . I need a crimping tool anyways.

[AlBargey]

Al,
This is a really good site. Thanks for bringing it.

https://eu.nkon.nl/eve-lf280-prismatic- ... fepo4.html

They are only €67.00 if selecting non EU! But I don't know if they'll need an EORI number and UK VAT, business import stuff.

NKON.NL stopped shipping to the UK a while ago now after Brexit made it too much hassle for them, But.... I was thinking a road trip could be fun, we have friends on the way to Eindhoven.

I think if it's declared and for personal use then possible?

16 x 280k V3 €67 cells at NKON price of €1,072 (£915) = £207.59 import and duty fees = £915+£207 (£1122) or £70 per cell VS Fogstar £119 per cell.. Maybe do a road trip, even if paying tax twice it's still cheaper.

Check tax on goods you bring into the UK - GOV.UK:
www.tax.service.gov.uk www.tax.service.gov.uk

[Joeboy]

Has anyone on here built using the small 18650 batteries? I always wondered how that went. A fair bit more complicated than a 15 stack of LF's? Cool nonetheless.

I wonder how mobile and controllable such a pack would be in comparison to the commercial smaller form storage units? Just a passing thought...