AGM or LiFePo4?

[Anhedonic]

So why spend 5-7x the price of lead on them?

Why buy drop-ins or why buy lithium? 

1. I would buy a complete 12v LFP battery because I don't want to have to string together and deal with balancing 4 separate cells. Having a single box that does all I need it to do is valuable to me and I don't want to spend more effort than I have to building or maintaining it nor do I want to have many pieces and a giant web of wiring just to build my battery. 

2. I would buy lithium to save both weight and space, as well as to be able to use the full, rated capacity of the battery to do things. In addition, I plan to have my van for the next 10 years and I don't want to have to replace my batteries once, much less a few times as I would with AGM batteries. 

Why don't I use wet cells? Because I really, really don't want to is the bottom line. 

When you mention C-rate, are you talking about charge rate? If so, some of the batteries I've seen, including the one I mentioned above as a strong-if-expensive contender, do have very high charge rates. 

As to interfacing with BMS components, I'm not entirely sure what you mean.

 

[QinReno]

No the ones I've seen were 25' long and could be rolled up,  seemed very durable.

But still being made?

They have those things too, but also in regular type panels. You can tell the amorphous, as many of those panels do not have the square lines or corner divits like poly/mono.
https://www.google.com/search?q=100+watt+amorphous+solar+panel&source=lnms&tbm=isch&sa=X

So, I'm just planning to try an experiment here, but will also keep my 100W mono panel onhand. When I was down in the Sierra last week, my one panel (which I simply put outside in the daytime) had to be moved constantly to avoid shading by the trees as the sun moved, and I only got 3-hours total charge time as it was.

 

[QinReno]

When you mention C-rate, are you talking about charge rate? If so, some of the batteries I've seen, including the one I mentioned above as a strong-if-expensive contender, do have very high charge rates. 

Charge rate is a factor, but I suspect "high" charge rate will not be an issue with solar. Eg, a typical 100W panel will only put out 6-7A max, and that's only about Q/14 to Q/16 for a 100AH battery. There might be an issue with charging off an auto alternator however.

In the world of RC cars, Q/14 is more or less considered to be a trickle charge, whereas a lot of RC battery chargers will go Q/2 or so, IOW charge the Li batteries fully in about just 2-hours. RC guys want to get their cars back on the track ASAP. Of course at those charge rates, the batteries also get very hot.

 

[Anhedonic]

Charge rate is a factor, but I suspect "high" charge rate will not be an issue with solar. Eg, a typical 100W panel will only put out 6-7A max, and that's only about Q/14 to Q/16 for a 100AH battery. There might be an issue with charging off an auto alternator however.

In the world of RC cars, Q/14 is more or less considered to be a trickle charge, whereas a lot of RC battery chargers will go Q/2 or so, IOW charge the Li batteries fully in about just 2-hours. RC guys want to get their cars back on the track ASAP. Of course at those charge rates, the batteries also get very hot.

There are too many acronyms and abbreviations I don't know here.   

The battery I was looking at (the big, expensive, KiloVault one) has a charge rate of 150a. That seems pretty high.

 

[QinReno]

Q = full charge, basically measured in AmpHr; maybe John's C is similar to my Q.
A = amperes, of course.
RC = radio control, of course.
ASAP = as soon as possible, of course.

So, Q/16 = charge rate here would be 100AH / 16Hr = 6.6 Amps, and which would charge the battery in roughly 16-hours. Q/2 = 100AH / 2Hr = 50 Amps, very high. 

Looking back at your 300AH battery, it does say 150A max charge and discharge currents. I missed it earlier. That is huge. So that's Q/2. Then 300W of solar into your 300AH battery would give about 3*7 = 20 Amps max, which is way below that at only about Q/15, or full charge in about 15-hours. In general, solar charging would never get anywheres near 150A. OTOH, if you charge off an alternator, it might be higher than 20 Amps.

 

[B and C]

My AGM batteries are going on 9 years old. I only cycle them to about 20% discharged (80% remaining). Sometimes down 30% but rarely. I have a 375 AH bank though and I don't ever have to worry about charging temps. I do have a charging temp sensor on one of the batteries for the charge controller to use though. They are starting to lose capacity in the last year. When capacity doesn't meet my demands, I will replace with AGM again. Not going to reinvent the wheel and spend what precious time I have left try to coddle/learn a new chemistry. My $0.02 worth (if that).

 

[John61CT]

Weight and size for 300AH usable is NBD for lead.

Let's say $400 for FLA, can last at least 7 years, stand up well to beginner mistakes / abuse.

AGM at $800, likely 5 years at the most, have to be more careful, more expensive chargers etc. Going to 150+AH each means super heavy, or stringing 6v cells anyway.

LFP at $3000++, plus say 300 extra hours learning and research to feel secure you won't kill them. Very precise care needed for longevity, at say a grand for monitoring / control gear.

No there is no easy howto, no list of what to buy.

If drop-in yes, less concern about BMS protections, but might only last 5 years, I dunno,

Done the normal way with 4-packs of cells, maybe 20 years if you're lucky, again, we dunno yet.

Stringing 4 together is like the difficulty of tying shoe laces together as part of overall training for the decathlon, if you think that's too much trouble run do not walk from LFP.

Same with adding water to batts once in a while, silly reason to waste many hundreds of dollars when you're on a budget.

 

[John61CT]

And you guys talking about solar charging, my impression is that 80-90% of energy will come from mains or the genset, since running aircon many hours per day is assumed.

If going LFP then no need for solar at all, save money complexity and roof space.

 

[Anhedonic]

And you guys talking about solar charging, my impression is that 80-90% of energy will come from mains or the genset, since running aircon many hours per day is assumed.

If going LFP then no need for solar at all, save money complexity and roof space.

The generator is only going to be running when I need the AC running or the chair charged. The house battery is intended for everything else. As you suggested, I gave up on running the AC from batteries. 

600ah of FLA batteries is what? 300lbs? that's a lot but not unmanageable. What it isn't is space efficient. Similarly, 4 cells laced together is also not terribly space efficient. One large battery that I can wire in and slide under a seat is a nice, compact option. 

My chair and lift take up the entire garage area in my promaster 136"wb. Adding a generator box eats about 8 cu ft in front of the seats. That leaves me with very, very little space. I have no idea where I would put 6 100ah FLA batteries, much less how I would manage to connect them all together, not because it's too hard or too complex but because it means that they will need to occupy adjacent space. It's not a question of a bunch of this or a bunch of these or a few of these or one of these. It's a question of which one, single thing, or possibly two single things can I fit in the van with all the other stuff. 

Further, on the topic of FLAs, I have no way to place them safely and vent them properly given my space limitations. 

Complexity is not my problem. I'm neither an idiot nor a stranger to technical topics. This is not my area of specialization, but I could do without the condescension.

 

[John61CT]

OK, if the extra cost of thousand$ and

higher risk of early EoL, and

much greater complexity

is worth those concerns to you. . .

Not arguing, do what you like, but for others reading now and in the future,

Thousands of FLA banks are installed without any special venting. Few people are sensitive to their offgassing, and

you'll need well controlled high-CFM ventilation installed anyway.

LFP will need strong hold-downs as much as anything else, but yes maybe half the weight.

Bussbars, wiring & terminations, CP / distribution boxes, chargers, switches, outlets, converters / inverters, all will need well organized professional-level installation taking a certain amount of space,

whichever way you go. LFP will need more monitoring and control gear.

And I do not mean to be condescending, not saying you can't learn what's required, and in fact I've been putting in a lot of my time helping you climb the learning curve, but you're not yet over that initial "Dunning—Kruger hump".

Many "unknown unknowns" remain.

 

[Anhedonic]

I do appreciate the time you've spent on helping out. I don't mean to be unappreciative of that. You've given me a lot of information that I can use and given me some good reasons not to try things that looked good at first glance.

I'm not under any Dunning-Kruger delusions. I know how little I know on the topics of battery chemistry and electrical hardware. That is why I keep looking for an at least semi-plug and play solution; I'm not an electrical engineer and I don't have plans to become one. That is also why I came here seeking advice. I want to build this and I want to do it right, but I also have limitations I have to deal with. Some are monetary, some space-oriented, some based on my own abilities, and some based on how I plan to use the van.

It may be good to say at this time, that I am planning to get an actual electrician to install and consult on the ultimate design of all of this. I have no delusions about my ability to do this right and safely without hands-on help, at least not at the level that I want it to work and the safety that I need.

I know all of these things take space. I am factoring that into my build. The generator is going to be in a box. Behind the box in one of the seats. Under that seat is where I want to put a battery. On top of the generator box is going my electrical cabinet that will hold all the hardware for the electrical system. I'm figuring that a 2.5' x 2' x 3' cabinet will probably be enough for the inverter, breaker box, etc.

The battery will be secured by a frame bolted to the floor and held in by ratcheting tie-downs. If the van turns over, it still won't go anywhere.

I apologize if I snapped at you without adequate justification.

 

[John61CT]

No apology needed at all, I know brusque is more efficient and everyone needs a thick skin once getting into controversial territory, which LFP will remain for years to come.

at least semi-plug and play solution

Only available per component with LFP, overall systems integration is up to you unless spending say $8-12K minimum.

Lead is tried & true, well understood by thousands of marine and RV techs. Former more so than the latter.

> I am planning to get an actual electrician to install and consult on the ultimate design of all of this.

Good luck finding one with a clue about LFP.

In the US, no license / training is required for DC electrickery.

Licensed electricians often are very poorly informed on this niche arena, 12V in general, never mind LFP.

If you want to go that way, pay a specialist like Bruce @ OceanPlanet or MaineSail, even if you need to drive to Maine. Or someone they recommend closer, say 500 miles, there might be another dozen or two in the country can do it well, just not enough demand.

As I said, a few hundred hours of research and practice you'll be able to DIY, it isn't rocket science.

Or if you need help with physical issues, pay a handyman type to follow your close instructions.

Getting a "pro" who thinks he knows more than you about 12V stuff (D-K is omnipresent) will just make things more difficult with LFP, bad enough with lead.

With mains power issues, auto transfer switches, big Victron PowerAssist combi charger/inverter, yes high voltages require a noob paying a licensed professional.

 

[Anhedonic]

In case you smell something burning, that would be me thinking very hard about how I can do this such that I get something resembling what I want and which unpalatable compromises I want to make.

 

[John61CT]

But think how much money so many people waste by not doing the research and educating themselves first!

Bigger vehicle solves lots of problems.

But brings new ones

 

[Anhedonic]

I wish I could have gotten a bigger vehicle. Unfortunately, I need to fit it in the parking space behind where I live. A 20' vehicle just won't do that. That meant this was literally the only type of van currently on the market that would work. I wanted a 159" WB, but had to go with the 136". That, plus the chair and lift mean space is a pretty serious crunch.

 

[QinReno]

Hello A. Once I realized your issues with the wheelchair, lift, and lack of space as a result (ie, this being yesterday), I think you probably have the right idea. Go with LFP for size, weight, and charge-density.

600AH of FLA or AGM will take 6 batteries and be closer to 400 lbs, meaning big area and a lot of weight to move around, plus a lot of extra wiring, plus the 6 FLA would need to be installed so you could easily check and maintain the batteries.
- https://webosolar.com/store/en/deep...MIzLih1LLt3QIVwkwNCh2WlA_2EAQYASABEgKwVvD_BwE

 

[Anhedonic]

For a sense of how space-restricted I am, here is a picture. This picture is 100% of the space I have to work with. Keep in mind that there will also be a 3'x3'x2.5' box for the generator up against the far wall that will stop just shy of the seat on both sides. 



Everything past the seat is taken already. So I've got a little over 3.5'x6' of floor space to work with. In that space goes the generator, the electrical cabinet, the bathroom, the kitchen, most of my storage, and my living space. 

It's like playing Tetris very slowly, but with only about 5 lines.

 

[QinReno]

Yeah, I saw your other pictures yesterday too, lift and chair under the bed. I have a regular GMC Savana van, which has about 6'x9' of space in the back, and it's just amazing how fast it disappears when you start to put stuff in there, LOL. Soon as you put the bed in there, you go ... WHAT?

So, all in all, I think you need to become an LFP "early adopter" - which you notice from that wikipedia link is another term for guinea pig!! But you'll learn a lot too. And you should have plenty of power for a good frig. Have fun, .
https://en.wikipedia.org/wiki/Early_adopter

For me, as I expand solar plus in the next year, mainly so I can add a frig, I'll stick with AGM due to less maintenance and minimal outgassing, even if they don't last as long as FLA.

 

[Anhedonic]

Well, I've been an early adopter of a lot so this would be par for the course. Sometimes it even goes well.

As luck would have it, I think I have found a solution as a side effect of buying The Expensive Battery. I contacted AltE who makes it and they have everything I'll need from solar down, have pre-sales system designers that will help me through figuring out what to buy and how it all goes together, and they even have a small stable of electricians who are expert with batteries, 12v systems, solar, and very small installations as well as large ones. Apparently everything but the electrician comes with the whole pre-sales process.

The best part is that they are local and do local pick up so no shipping.

Of course I'll have updates as progress happens. I'll certainly be posting their suggestions to see if anyone wants to sanity check them.

 

[QinReno]

Sounds like you have it knocked. Experts on call. And they are local too - wow! Can't beat that. Everything I seem to want to do in person requires driving from the west coast way over to the southeast.