What makes a LFP dropin rated for under the Hood?

[Jman99]

There are LFP dropins ranging from 75-100AH usually that are rated for under the Hood use & some come with a 3 year warrenty for this. As far as I can tell most are using prismatics & cylindricals types of cells.

What do they do to them to make the whole battery ready for under the hood? I'm asking as I wan't to put some of my own 180 tall bare cells under there to replace a heavy Aux AGM & just wan't to know what special treatment they get to cope with the harsh vibrations & heat, & how should I go about it? eg. just bare cells strapped in hose clamp in a plastic container?

 

[john61ct]

All drop-ins are based on a lie.

Yes you will likely get better lifespan than lead, they just count on laziness and ignorance to not get wiped out by warranty claims. Or shysters, will just disappear.

But their cell quality, packaging methods, protective circuitry are far inferior to what you could put together DIY for cheaper

and treating it as LFP should be treated might get 10x the lifespan compared to drinking the drop in koolaid

 

[Rando]

The only thing that I can think of that would be necessary for under hood use would be built in temperature limits, particularly for charging. You want to make sure your BMS has the ability to prevent high current charging below a certain temperature, and possibly prevent both high current charge/discharge above a certain temperature to protect the MOSFETs. Assuming you are mounting this to the vehicle body, temperature and possibly incidental water exposure are the main differences. I don't see why there would be a significant difference in vibration from other parts of the vehicle.

I am using a similar 150Ah pack at the moment, without issues. In general the trickiest part is the interconnects between the cells. There are numerous drop in BMS boards that will work well for this application.

As for the rant about drop in batteries, yes they have limitations, but they also have advantages. For installation under the hood, a drop in with the right temperature rating seems like the way to go.

 

[john61ct]

possibly prevent both high current charge/discharge above a certain temperature to protect the MOSFETs

Even slightly higher temperatures reduce cell longevity, by a lot.

LFP is LFP, there are no real differences in "temperature rating".

The levels reached in an engine compartment could be considered murderous might lose 80% or more lifespan,

but there is no difference there between drop-in and accessible-cell packs.

> I am using a similar 150Ah pack

> trickiest part is the interconnects between the cells

Similar in what ways? What you describe is not a drop-in!

By definition a drop-in makes the interconnects and BMS and measuring cell level voltages inaccessible and invisible.

> There are numerous drop in BMS boards that will work well for this application.

Again, there is no such thing, inherent contradiction between what a drop-in is and the ability to know anything about the BMS much less choosing one.

 

[Rando]

The OP is building his own battery pack our of cylindrical cells, therefore he needs interconnects and a BMS. He wants to mount it in his engine bay, therefore he needs some thermal protections for the pack, and it should probably have some water resistance as well.

I am not sure what your standard rant about the evils of drop in LiFePO4 has to do with any of this. You were the one who brought it up.

 

[Jman99]

All drop-ins are based on a lie.

Yes you will likely get better lifespan than lead, they just count on laziness and ignorance to not get wiped out by warranty claims. Or shysters, will just disappear.

But their cell quality, packaging methods, protective circuitry are far inferior to what you could put together DIY for cheaper

and treating it as LFP should be treated might get 10x the lifespan compared to drinking the drop in koolaid

How does this help me? Yep i know how to build a long lasting battery, but this is for hard remote travelling say once a year, so I dont break the vehicle from excess weight. a short lifespan is part of the game, 6yrs out of the sub $1000 lpf battery and buy another isn't all that bad for the high cost of a good agm or wet cell. lol koolaid, now I know what it's like when I myself rip in to others about buying these things.

 

[Jman99]

The only thing that I can think of that would be necessary for under hood use would be built in temperature limits, particularly for charging. You want to make sure your BMS has the ability to prevent high current charging below a certain temperature, and possibly prevent both high current charge/discharge above a certain temperature to protect the MOSFETs. Assuming you are mounting this to the vehicle body, temperature and possibly incidental water exposure are the main differences. I don't see why there would be a significant difference in vibration from other parts of the vehicle.

I am using a similar 150Ah pack at the moment, without issues. In general the trickiest part is the interconnects between the cells. There are numerous drop in BMS boards that will work well for this application.

As for the rant about drop in batteries, yes they have limitations, but they also have advantages. For installation under the hood, a drop in with the right temperature rating seems like the way to go.

thanks, but the steel battery tray is much harsher than the insides of the vehicle.

 

[john61ct]

Not ripping in, many have no idea.

I was answering your question, a manufacturer claiming "you can do this"

is not due to anything special they are doing.

DIY with accessible cell data, ability to fit your own BMS and other controls

will not likely cost more but give you a higher chance of greater lifespan.

Not as convenient though, obviously do what you like.