Battle Born LFP impressions

[Ampster]

I think that sheds some light on why Lithium is more tolerant of being in parallel.

[Mike90250]

I’m not sure how much time you’ve spent measuring the internal resistance of a LiFePO4 cell set.

Your statement sounds good in theory, but i’ve got a $4500 battery analyser that says the internal impedence of a LiFePO4 cell changes with it’s SOCand especially temperature, but doesn’t change with age.

I’d be keen to hear from others, as my cells are only eight years old, so when they start to age things might change..

Your experience beats my book learning from industry sites. So the user can decide what they want to do (they always do anyway !! ).

[tom rickard]

The Li BMS does nothing regarding the internal resistance of the cells. New cells = lower IR. So when adding new to the old bank, the new cells take over the brunt of the work, till they are as worn ( Internal Resistance ) as the older cells. No voltage measurement needed, nothing the BMS can do about it.

I’m not sure how much time you’ve spent measuring the internal resistance of a LiFePO4 cell set.

Your statement sounds good in theory, but i’ve got a $4500 battery analyser that says the internal impedence of a LiFePO4 cell changes with it’s SOCand especially temperature, but doesn’t change with age.

I’d be keen to hear from others, as my cells are only eight years old, so when they start to age things might change..

[PNjunction]

You said it best Mike!

Using batteries with different usage patterns, even if they are the same make/model/capacity, is just not the thing to do.

But people are going to do it anyway and learn the hard way. Or not learn, and just go about putting things together lego-like on a whim. Costly in the long run.

This is why I rail against "one-off" systems built from scraps or other funky DIY methods - they make the poorest choice for making any sort of observations or learning anything truly useful when transitioning to a commercial quality unit.

[Mike90250]

The Li BMS does nothing regarding the internal resistance of the cells. New cells = lower IR. So when adding new to the old bank, the new cells take over the brunt of the work, till they are as worn ( Internal Resistance ) as the older cells. No voltage measurement needed, nothing the BMS can do about it.

[PNjunction]

Forgot to mention another mind-blowing aspect, although we've talked about it somewhere along the line..fuel savings with a genny.

So you have a genny onboard to take care of those times when you need to bring your lead-acid up to a full charge. Multiple rainy days - what have you. Typically that is started in the morning up to about 80% SOC, and you let a small solar system take care of that last 20%, because the cost of fuel to run a genny in the CV stage where current is naturally tapering is ridiculously expensive. It takes time. So the small solar setup finishes the job instead.

But with LFP, the charge acceptance is so great, that running the genny up to 95 or even full, (if you've set your CV voltage high enough) can actually be done solely with a genny. CV doesn't take that long, so you aren't incurring a lot of fuel-expense, or perhaps 95% SOC is just fine.

So that's another feather in LFP's hat from a system standpoint. If you do have to use a genny, some of that extra upfront expense is offset by very efficient use of the genny to reach even 100% - which one would never do with lead-acid unless they just want to waste fuel/cash.

I don't want to sound like a marketer trying to keep LFP upfront prices high, but it's just another observation I encountered.

[PNjunction]

Heh, when I first started with prismatics back in 2009 or so, I thought that give them a few years and lead acid would be toast based on the performance differences alone.

But - that didn't happen, and possibly not to threaten the lead-acid industry, the upfront costs remained high, and were touted solely based on cycle life cost. It actually does work out, but it's a longer term outlook.

At the time, I was plenty happy to just replace lead-acid more often. Thanks in part to this very website, I got enough info to actually enjoy proper lead-acid maintenance, be it flooded, gel, agm.

Then along came LFP. Thing is, despite decades of talk, I had to go hands-on. Holy cow.

From a battery-nerd standpoint, LFP took a lot of maintenance fun out of the equation. What? No eq? No hydrometers? No charging a gel to a max of 14.1v cv despite the sticker ratings? Supplying supplemental charging to my agm's simply because solar can't really hack it on a daily cyclic basis? Not worrying about Peukert? My inverters always running very efficiently at nearly dead status? PSOC and not worrying about leaving my battery at 30% SOC and going on a 2 month vacation and basically picking up where I left off with no sulfation? Goofed on your power budget and actually bought too much capacity (yeah, rare) - just psoc it, and not worry about reaching 100% soc all the time.

(Hint - in those PSOC cases, I STILL treat my overly-large capacity battery to a full charge - discharge - recharge about once a year just to make sure the chemicals stay active across the entire surface. Another thread perhaps)

I think that for a battery nerd, this performance aspect - provided you start with a quality product in the first place, be it this or something else - might make the hit on your wallet MUCH easier to swallow.

It truly is mind-blowing, but it takes hands-on to make it sink in for the AHA moment to occur. So just a warning.

[SunEagle]

I am also impressed with the battery. I just wish all Li chemistry types would be lower in cost and much easier to justify as an energy storage source for solar. Without products coming down in price then most of the people will never be able to use solar at home.

I hope that since pv panel prices have come way down then all other solar based equipment follows. We need to be able to install this equipment and stay inside a financial payback period.

[PNjunction]

Re: add-ons or replacements in leiu of doing a power budget - now that I think about it from a manufacturer's perspective, I'd probably not to want to limit sales. In that case, it might be simply "not recommended, but not prohibited".

Upfront cost: actually better than most considering how open they are about their manufacturing / testing process. Each cell is measured for capacity, and assuming they are looking for internal resistance outliers too. Then each "mod" as they call it (pack of 3.2v cells) is tested again under those conditions before final assembly. Lots of manual labor there. Far better than someone just pulling cells out of a cardboard box and firing up the spot welder.

In regards to lead-acid -- WE know how to get the most and maintain lead acid properly, but most don't. I alluded earlier that for many, the upfront cost is paid back in less end-user maintenance to keep the battery healthy. So there's that.

Website and videos: I've got my radar up and running, and nothing I see on their site(s) if you include Dragonfly, shows up on my screen as a red-flag. Other than the obligatory green thing and user testimonials, it seems to be on target technically with no BS and limited buzzword marketing. It's funny to watch the CEO, an obvious techy guy hold back when discussing things - which looks like he'd love to get into but doesn't want to make eyeballs glaze.

If I needed one, I'd be very comfortable with Battle Born. If I'm trying to run massive propulsion systems, or life-critical systems, then possibly go into the stratosphere with something like Lithionics, but that's a whole different level of engineering.

Again, as a non-owner, these are just impressions. Impressed enough to like what I see, that's all.

[extrafu]

I say it is expensive for 2 x 12v 100Ah battery system at $2000 compared to 2 x 6V 225Ah FLA batteries at $250.

The comparison is will the 100Ah Li battery produce a kWh cheaper then the FLA over their lifetime.

Some people can better afford buying those 2 x 6V @ $250 very four years compared to 2 x 12v 100Ah at $2000 every 8 years

I perfectly agree with you on this.

[SunEagle]

Omitting the voltage is quite wrong in every Ah battery capacity saying. 100Ah at 3.2v for a single prismatic cell is far away from a 100Ah at 48v. In this case, it's 12V but only saying 100Ah is expensive is misleading.

I say it is expensive for 2 x 12v 100Ah battery system at $2000 compared to 2 x 6V 225Ah FLA batteries at $250.

The comparison is will the 100Ah Li battery produce a kWh cheaper then the FLA over their lifetime.

Some people can better afford buying those 2 x 6V @ $250 very four years compared to 2 x 12v 100Ah at $2000 every 8 years

[extrafu]

With those 100Ah being around $1000 each I think that someone would have to have a lot of disposable money to tinker around with them.

Omitting the voltage is quite wrong in every Ah battery capacity saying. 100Ah at 3.2v for a single prismatic cell is far away from a 100Ah at 48v. In this case, it's 12V but only saying 100Ah is expensive is misleading.

[Ampster]

I was actually referring to putting them in parallel to increase pack capacity. Typically one would do that with similar capacity batteries but if one group was slightly older than the rest of the pack within 10% or so. I don't think the degradation would be the same with lithium as even that slight difference would create with Lead acid. That is all I was speculating about. Maybe this is a topic for another thread since it would not be unique to Battle Born

I understand the issues of putting different vintages or capacities in series and your illustration does a good job of explaining why that is not recomended..

[SunEagle]

Maybe a mental exercise might help that goes to the extreme to amplify the effect:

Make a 4S / 48v, 100ah bank with 4 of their batteries. Assume you have done the right thing and charged each individually first before doing so etc - standard procedure.

Now remove one of the batteries, but replace one with their 50ah model. Just for discussion obviously.

That 50ah battery (or one of the 4S cells if you want to look at it like that) will be worked hard, much harder than the rest. But also when you charge it back up, say you only wanted to charge to 90% full, since we don't need a totally full charge all the time.

That 50ah cell will always be in balancing mode, and riding out the CV stage to 100% capacity. Basically the cells are going to act / age differently than the rest of the system.

Since the bms' don't communicate with each other, eventually this situation *may* be of concern depending on your application and how critical it is. Out at sea? On a wheelchair 10 miles from home and your cellphone doesn't work?

Probably the best thing to do is ask them, and not rely on my internet analogies.

Ultimately, the warranty decides all. Does such mix-n-match as convenient void it?

With those 100Ah being around $1000 each I think that someone would have to have a lot of disposable money to tinker around with them.

[PNjunction]

Maybe a mental exercise might help that goes to the extreme to amplify the effect:

Make a 4S / 48v, 100ah bank with 4 of their batteries. Assume you have done the right thing and charged each individually first before doing so etc - standard procedure.

Now remove one of the batteries, but replace one with their 50ah model. Just for discussion obviously.

That 50ah battery (or one of the 4S cells if you want to look at it like that) will be worked hard, much harder than the rest. But also when you charge it back up, say you only wanted to charge to 90% full, since we don't need a totally full charge all the time.

That 50ah cell will always be in balancing mode, and riding out the CV stage to 100% capacity. Basically the cells are going to act / age differently than the rest of the system.

Since the bms' don't communicate with each other, eventually this situation *may* be of concern depending on your application and how critical it is. Out at sea? On a wheelchair 10 miles from home and your cellphone doesn't work?

Probably the best thing to do is ask them, and not rely on my internet analogies.

Ultimately, the warranty decides all. Does such mix-n-match as convenient void it?