270ah DIY LiFePO4 build

[gregcope]

@vas No recommendation as I have not used them yet;

4pcs Eve 280ah Lifepo4 (lfp) 3.2v Cells Battery (new Version Lf280k With 6000cycles,Fully Matched)--genuine Grade A - Buy Eve,Lifepo4,Rechargeable Battery Product on Alibaba.com

Search the DIYSolar forums (https://diysolarforum.com) for info on other vendors and Luyan/Amy. Not the cheapest.

 

[gregcope]

Can anyone recommend me a fuse/fuse holder for 60-200Amp 12v loads?

Thinking I need one "just in case" ;-) But am a little perplexed on the choice and availability.

 

[Poey50]

Can anyone recommend me a fuse/fuse holder for 60-200Amp 12v loads?

Thinking I need one "just in case" ;-) But am a little perplexed on the choice and availability.

Because of the high level of current that LFP can pour into a dead short a Class T fuse is recommended close to the battery. I'm still waiting for mine to be delivered from Cactus.

 

[Kelpie]

I found class T fuses impossible to source in the UK. Cactus said they would get them in but have pushed back the delivery date by another month.

I'm using a 400A ANL fuse, which I am fairly confident will be sufficient in the real world. If using multiple batteries I would also put a MRBF on each battery.

 

[gregcope]

This is exactly why i asked. I looked at T fuses that seem popular over the pond but almost impossible to get here.

Hence the question.

 

[Poey50]

This is exactly why i asked. I looked at T fuses that seem popular over the pond but almost impossible to get here.

Hence the question.

I'm using MRBF at the moment, as I have for the last year, and will replace when my Class T arrive.

 

[vas]

poey50: mind if you post link to the one you have and the one you ordered (wont be ordering from the UK for sure though!), slightly confused with the fuse terminology tbh!

 

[Poey50]

poey50: mind if you post link to the one you have and the one you ordered (wont be ordering from the UK for sure though!), slightly confused with the fuse terminology tbh!

This is the MRBF. I have the double version with separate fuses for the load and charge circuits.
https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

This is the Bluesea Class T fuse holder (plus fuses) I'm waiting for from Cactus.
https://www.bluesea.com/products/5502/Class_T_Fuse_Block_with_Insulating_Cover_-_225_to_400A

 

[gregcope]

Has anyone got a 12v capacity measurer gizmo i could rent/borrow? I am only going to use it once so seems pointless to buy one.

 

[RogerJolly]

I'm thinking you'd choose the same main battery fuse rating for Lithium as for LA, as it's to protect the wiring.

And again, whether or not you fitted one would be independent of the battery type, being more about the likelihood of the cables shorting.

It does seem that more emphasis is place on fuses in a Lithium context. But surely a LA has more than enough capability for carnage – wouldn’t like to be shot in the head with a small gun any more than a big gun.

Just trying to clarify the issues to myself prior to a possible Lithium switch. Would be grateful for any correction/guidance.

Thanks

 

[noelex]

I'm thinking you'd choose the same main battery fuse rating for Lithium as for LA, as it's to protect the wiring.

And again, whether or not you fitted one would be independent of the battery type, being more about the likelihood of the cables shorting.

It does seem that more emphasis is place on fuses in a Lithium context. But surely a LA has more than enough capability for carnage – wouldn’t like to be shot in the head with a small gun any more

The problem, or potential problem, is the interrupt current (IC) of the fuse. At very high currents the fuse can weld closed and fail to break the short circuit. As a lithium battery is capable of delivering a higher current in a short circuit situation than a similar sized lead acid battery this becomes more of a concern.

Thus when switching from lead acid to lithium a new fuse type with a higher IC may be needed (such as switch between MRBF to T class fuses). The actual fuse value may be unchanged. T class fuses have a very high IC rating (typically 20,000A) so are a popular choice.

 

[Poey50]

The problem, or potential problem, is the interrupt current (IC) of the fuse. At very high currents the fuse can weld closed and fail to break the short circuit. As a lithium battery is capable of delivering a higher current in a short circuit situation than a similar sized lead acid battery this becomes more of a concern.

Thus when switching from lead acid to lithium a new fuse type with a higher IC may be needed (such as switch between MRBF to T class fuses). The actual fuse value may be unchanged. T class fuses have a very high IC rating (typically 20,000A) so are a popular choice.

Absolutely this. Also arcing can occur across a blown fuse. There's a photo of this with an ANL fuse some way back in this thread.

 

[Poey50]

Has anyone got a 12v capacity measurer gizmo i could rent/borrow? I am only going to use it once so seems pointless to buy one.

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.

 

[RogerJolly]

The problem, or potential problem, is the interrupt current (IC) of the fuse. At very high currents the fuse can weld closed and fail to break the short circuit. As a lithium battery is capable of delivering a higher current in a short circuit situation than a similar sized lead acid battery this becomes more of a concern.

Thus when switching from lead acid to lithium a new fuse type with a higher IC may be needed (such as switch between MRBF to T class fuses). The actual fuse value may be unchanged. T class fuses have a very high IC rating (typically 20,000A) so are a popular choice.

Thank's noelex. Was a bit woolly in my understanding of the various parameters - fuses more complicated than I thought!

 

[Kelpie]

One thing about IAC ratings is to look at the voltage at which they are rated. I think ANL may actually be better than MRBF when you compare like for like. I could be wrong

 

[Poey50]

One thing about IAC ratings is to look at the voltage at which they are rated. I think ANL may actually be better than MRBF when you compare like for like. I could be wrong

Yes, I wasn't meaning to suggest that MRBF are more suitable than ANL. Mine cover 10,000 amps at 12 volts which is probably OK for my 270ah 12 volt pack but I believe Class T offer at least double that protection. Rod Collins has done a lot of testing on ANLs and nevertheless recommends Class T.

 

[Poey50]

This gives a bit of reassurance for MRBF protecting against an LFP short. However it may be the case that the long undersized cable may have helped limit the short circuit current.

 

[vas]

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.

sorry to bore you, link to a capacity meter plz!
I have a 12V one which is a pain to use on my 6V trojans, and obvs no good testing lifepo4s...

 

[Poey50]

sorry to bore you, link to a capacity meter plz!
I have a 12V one which is a pain to use on my 6V trojans, and obvs no good testing lifepo4s...

No problem. I have one each of these. I've only used the 180 watt one which is very good. There are various YouTube videos on using them. [£31.78~37.69 32% OFF] 8 In 1 150W/180W Digital Battery Capacity Tester Voltmeter Adjustable Constant Current Electronic Load Charger USB Meter Indicator Module Board from Electronic Components & Supplies on banggood.com

 

[vas]

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