chrisski
Solar Boondocker
- Joined
- Aug 14, 2020
- Messages
- 5,179
Just want to be sure we're talking about Lithium Iron Phosphate, and not Lithium Ion Batteries.That said, I would not use anything else in a Li-Ion system.
Just want to be sure we're talking about Lithium Iron Phosphate, and not Lithium Ion Batteries.That said, I would not use anything else in a Li-Ion system.
Just want to be sure we're talking about Lithium Iron Phosphate, and not Lithium Ion Batteries.
That's a common misunderstanding. Lithium Iron Phosphate ARE Lithium Ion Batteries, just one of several common chemistries employed in Lithium Ion Batteries.Just want to be sure we're talking about Lithium Iron Phosphate, and not Lithium Ion Batteries.
I don't think I'll go down that road.That's a common misunderstanding. Lithium Iron Phosphate ARE Lithium Ion Batteries, just one of several common chemistries employed in Lithium Ion Batteries.
Oversized protection can be worse than no protection (in all things) ;-)Your all wimps! I just got me a Manly Sized Class T fuse for my system.
View attachment 74115
JUST KIDDING GUYS I thought that sized counted in everything
Well not in "All things" A nice 50 cal is better protection than a .223 and thick wires with thin Insulation pass more electrons than thin wire with thick insulationOversized protection can be worse than no protection (in all things) ;-)
Good point. What is the TE-13 reference?Just to correct an earlier post about the ABYC standard for Lithium Ion Batteries (TE-13), it does NOT mandate class T fuses.
This is true. And the ABYC E-11, barely considers LFP as it is. Considering the predicament you outlined above (unknown short circuit current) this is the relevant excerpt:The standard simply requires fuses of sufficient AIC (Ampere Interrupting Capacity). Unfortunately, as most battery manufacturers I'm aware of don't specify available battery short-circuit currents, the user is left with guesstimating instead of proper engineering to decide which fuses to employ.
Since short circuit current is unknown, the latter should apply. It is unclear if the above pertains to LFP or not, there is no indication that it does not.11.10.1.2.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery
overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery
manufacturer’s short circuit rating OR be rated at a minimum of 20kA at 125 VDC or higher.
That said, I would not use anything else in a Li-Ion system. The cost of the right fuses and fuseholders pales in comparison to the cost of batteries and inverter-charger, etc. costs. Safety and peace of mind are much more important to me.
Good point. What is the TE-13 reference?
This is true. And the ABYC E-11, barely considers LFP as it is. Considering the predicament you outlined above (unknown short circuit current) this is the relevant excerpt:
Since short circuit current is unknown, the latter should apply. It is unclear if the above pertains to LFP or not, there is no indication that it does not.
The above is probably why Class T has come to be the defacto standard recommendation (probably not a coincidence that both Blue Sea (Eaton-Bussmann) and Littelfuse have class T fuses rated for 20kA AIC @ 125VDC). So while there is no specific requirement for Class T, it is a sensible choice, and the most readily available fuse type that satisfies this standard.
good pointFrankly, I am disappointed in TE-13. There is a lot it could cover and doesn't. For instance, how can you require adequate AIC if you don't require the short circuit current to be specified? Having the 20kA fall-back in E-11 seems to be ducking the issue.
And subdividing a bank to accommodate protection devices that can't handle the full bank short circuit current begs the question of how you protect downstream devices and branch circuits.
?people who have lost all 24V power on their boats because the Li-Ion bank / BMS employed a single master contactor to "protect" the bank (while leaving all parallel strings still connected to the faulted string)
That is one way to look at it. Another way is that its just a statement made in recognition of the same problem that you stated--that AIC is often not listed by LFP manufacturers or assemblers--and guidance that can be followed without knowing that info would be useful to builders.Frankly, I am disappointed in TE-13. There is a lot it could cover and doesn't. For instance, how can you require adequate AIC if you don't require the short circuit current to be specified? Having the 20kA fall-back in E-11 seems to be ducking the issue.
If each subdivision was properly fused, with properly sized AIC and current ratings, downstream would be protected wouldn't it? Only the first fuse for each subdivision would need to handle the full AIC of the pack I think. Beyond that, lower AIC fuses are okay I think. I may be misunderstanding something.And subdividing a bank to accommodate protection devices that can't handle the full bank short circuit current begs the question of how you protect downstream devices and branch circuits.
Nice to have a little extra breathing room, particularly considering the unknowns. The 20kA stated in E-11 is referenced as the minimum if short circuit current is unknown, so exceeding it is reasonable. Was the fuse more pricey than other class T fuses you looked at?Interestingly Mersen (Ferraz Shawmut) A3T (160V DC rated class T) fuses are rated at 50kA interrupting capacity. Presumably this means they were qualified to this level with UL or whomever. I bought Mersen fuses for the extra "reserve" whether it's real or not.
Not sure without more context. My guess is they are just making a fairly safe generalized statement for the most popular system voltage. The Class T fuses I have looked at are all rated at 20kA for voltages above the common 12/24/48 system voltages (most commonly 125V or 160V DC)NOTE: Generally, fast acting current limiting fuses such as Class T fuses in an approved Class T fuse holder have an AIC of 20,000 amps at 12VDC and will be adequate for a subdivided bank.
[My comment: why only 12VDC?]
That is one way to look at it. Another way is that its just a statement made in recognition of the same problem that you stated--that AIC is often not listed by LFP manufacturers or assemblers--and guidance that can be followed without knowing that info would be useful to builders.
If each subdivision was properly fused, with properly sized AIC and current ratings, downstream would be protected wouldn't it? Only the first fuse for each subdivision would need to handle the full AIC of the pack I think. Beyond that, lower AIC fuses are okay I think. I may be misunderstanding something.
Nice to have a little extra breathing room, particularly considering the unknowns. The 20kA stated in E-11 is referenced as the minimum if short circuit current is unknown, so exceeding it is reasonable. Was the fuse more pricey than other class T fuses you looked at?
A power of standards (which I don't believe TE-13 has the status of) is to compel people to list safety-critical specification information in order to be compliant.
?The manufacturers and suppliers "tail" should not be wagging the standards "dog".
Bank of N packs in parallel.I take TE-13 to mean that if you have say 4 parallel battery system branches, you could fuse each at say 200A, and each of those fuses would ordinarily have to deal with just the short circuit current of that string. (Exception: if that strings shorts, the other three strings fault into it. ABYC did not allow for that - another flaw in TE-13?). But after those fuses, the branches are combined, and now the available fault current is four times greater.
Cell vendors publish internal resistance. With that and cell voltage, you can calculate an expected short circuit current.
From the numbers people have shown here, I get just about 20kA.