320Ah LiFePO4 battery system charging with alternator (no solar)

[T3TRIS]

Yes, another LifePO4 battery post... I've read through quite a few of these posts here but haven't seen one where the goal would be to eliminate solar panels altogether. The idea being that with the larger and larger capacity LifePO4 batteries, one can last quite a while without needing to recharge the cells and the likelihood that you would not start your van during that long period of camping is very very very low. Maybe not for some of us, but I imagine most of us don't camp in one spot for more than a week. This was inspired by this post from Howesight (thank you).

I'm still learning about all this, so please feel free to correct anything from this post.

Batteries:
So here we go, we just ordered 4x320Ah cells for our system, which will be made from scratch. I chatted with several people with different setups and it seems like a good baseline for debating this is that 200Ah seems to last 5 to 7 days depending on what's used in the van, what time of year, etc. Of course, there are many variables that change from one rig to another. Do you use a heated blanket to warm your bed up before bed? Is it 90deg out and the fridge is cranking all week? Do you have a 2000W subwoofer that you like to blast during camping? All of this matters, but for the sake of simplicity, lets say:
200Ah=5 days of modest camping without needing to charge
That means 320Ah should last us about 8 days.
I spent quite a while trying to figure out what could fit under the driver seat and it seems that the current achievements are 120Ah without modifying the box (150Ah cells seem to be the same size now) and 280Ah with some major mods. Some debate the choice of the driver seat for LifePO4 batteries since it's poorly insulated and these batteries can't charge when it's freezing.
Another thought is that the driver seat box (without modifications) seems to have 535 cu in of usable volume in a restricted 11.75"x6.75"x6.75" space. The 320Ah battery cells we ordered are 174mm x 71mm x 207mm, so 4 of them would be 6.85"x11.18"x8.15", or 624 cu in (about 15% larger than the seat box).
The current, no modification record has 4 120Ah cells (150Ah depending where you shop) each measuring 174mmx48mmx171mm, so 6.85"x7.56"x6.73" or 348 cu in (about 35% smaller than the seat box). Granted the Overkill BMS would also fit in the driver seat box, I'm still not sure it's the best spot if it creates battery capacity restrictions (and low temp charging restrictions). If the seat box is the place to put the auxiliary battery, then we would probably need to add some sort of solar panel for extended camping trips, adding weight, complexity and bulk, somewhat defeating the whole exercise, all of it for utilizing a spot that isn't all that ideal.
Storage is storage, volume is volume... the seat box isn't necessarily the easiest spot to get to, but we can store things there that would utilize the volume better. When we first considered batteries, I was convinced there wasn't a better spot, but with the larger and more affordable capacities and the opportunity to get rid of solar altogether, the equation changed.
We'll probably get the popular OverkillSolar 4s BMS 120a LifePo4 Battery Management System for 12v for our BMS.

Charging:
Now, onto the charging part of things. Supposedly, LifePO4 can easily charge at 0.5C, which means that in our system, we could send 160A and the cells would happily charge from 0% in a couple hours (or at least get to a high charge percentage). Sending 160A to these cells would require a beefy charge controller and an even beefier alternator. But theoretically, we could send 120A into the batteries (2hr40min for full-ish charge) with the Overkill Solar BMS but it's tough to find a DC-DC charge controller that can provide this much. They seem to be available in 50A options (from Redarc, Renogy and Victron) and even some 100A. 50A would take 6hr24min for a full charge from 0% on a 320Ah system.

In our system-to-be, we currently have the stock Subaru 70A alternator. I haven't figured out what our normal draw is from the alternator, but it would be obviously undersized for the LifePO4 system. I have a Tribeca 130A alternator coming in the mail which should fit without much trouble. Our 70A alternator was doing just fine with running our van and my understanding is that an alternator will only produce the amperage that the system tries to pull from it. So the 130A alternator should act the same as the 70A in normal conditions, but would have an additional 60A available for charging the LifePO4 batteries and would work nicely with a 50A DC-DC charge controller.

There are some considerations and additional questions to answer for this such as:
- Upgrading the alternator wiring for that amperage (I already installed a 2/0 gauge cable between the starter and the starter battery).
- If we start driving and the charging system pulls as many amps as it can from the alternator, the larger alternator will rob some HP from our engine (which we might feel).
- I don't know how amperage is prioritized. Let's say we're using the full 130A with 50A running the car and 80A going into the batteries (unlikely if we have a 50A DC-DC charge controller), what happens if we need to turn the windshield wipers on? What gives?
- The likelihood that we'd camp for more than 7 days in one spot is very low, however possible. We can always use the van at idle as a generator. Alternators have lower amperage at idle but I imagine the 130A would still have plenty to significantly charge the batteries.
- Most of the time, we spend 3 or 4 nights in one spot. If our batteries were at 100%, that means we'd be down to 50% by the time we start driving around. That means a 3hr12min road trip should be enough to get back to a full charge if the charging system can produce 50A.
- I'm sure there are other aspects I'm not considering yet.

Add-ons:
I still have to research other forms of charging, just in case. Even though I'd like to avoid solar panels completely, it probably wouldn't be too difficult to wire a solar connector if we wanted to carry around a folding panel. I doubt we would though, but if it's a minimal investment and easy install, might as well. On the other hand, it would seem that adding a way to charge the LifePO4 from a 110V outlet is a little more difficult and requires additional components that would take valuable space for not being used often at all. Is it possible to have a 110V charger at home that just connects to a solar port?
Another interesting add-on would be to add the capability to manually top off the starter battery from the LifePO4. I'm not entirely sure if there would ever be a need for this, my understanding is that LifePO4 isn't well suited for starting an engine, however in the event of a dead starter battery, could the house battery charge the starter battery enough to get a crank?

FYI: I might/will update this initial post as I learn more and get feedback.
_________________
Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery

[bobbyblack]

I'd tend to say that you would want to target a LOW charge level of 20% and a HIGH charge level of 80% to maximize the longevity of your battery bank.

Next up, long term storage; do you have many weeks of non-use? Keep an LFP bank at 50% is recommended for long term storage.

So, you go from a base line of 50%, takes you 4 or 5 hours to drive to your destination. All should be fine. Just keep an eye on what your BMS is saying. When you get down a ways, go for a spin to the ice cream shop, or whatev.

I have my 120ah LFP bank in the stock aux box. I'm moving it to under the bench ASAP. I liked how it fit up in the aux box, but I suffered a freeze down scenario that could have been life threatening, and I don't want to have that happen again... got so cold so fast (something like 50F to -20F in 3 hours) that I didn't think to turn on my battery warmer. I was having a hard enough time just keeping the bus headed into the 40+mph oncoming wind blast.

My recommendation is to also get a house battery charger, 110V. There is an extra outlet that the stock fridge used (if you still have a stock fridge.. there will be an 'extra' and if not, then you have TWO plugs open in the galley). Plug your little charger in there, and wire it to the BMS. It is VERY simple. When you are home, getting ready for a camp, just use a drop cord and plug in to the side of you camper.. bingo, you are charging up your bank. Check in with your BMS app a few times. There is a 5 amp unit that is quite reasonable, and bigger ones for more money, but I went with a 5A unit. Its small enough to hide under my forward drivers 'shelf' of the aux battery area.. But I will put it somewhere near the water tank when I move things back.

The question about using your house battery to charge up a start battery... Well, a 320aH can provide plenty of juice to do that, yes... Also, that 5A charger I mentioned above, yes, you can take if off your BMS and (change the battery type to flooded) and use some sort of inverter, based on whatever that charger is rated for.. in my case five amps at 12 volts is not that many watts.. I'm an idiot and thought I should get a really large inverter, since I wanted to run StarLink and a TV... Yup, I'm that guy.. Anyway, you CAN make do with just that single charger, but many many more folks out there would suggest a separate trickle charger for the start battery, just think of the 'off season' as well for that. You do know that flooded batteries loose approximately 1% of their charge each day of non-use, and that does NOT INCLUDE things like a stereo that uses a little bit to keep your station memory set. Not to mention any other little led's that blink, etc.. Anyway, a little trickle charger hooked up to the start battery makes sense to a lot of people. And they are reasonably priced, too.

Oh, one last thing, I really try to never leave home without a fully charged jump pack. So very handy at all sorts of odd jobs, and a neighborly helping hand for those poor souls who forgot theirs...

Cheers!

-bobby
_________________
'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[T3TRIS]

Thanks Bobby, that's all good stuff. Dang I hadn't really thought about the temperature drop for charging while driving. That box would be cold indeed!

Our van was originally a passenger tintop, so we don't have any of the Westfalia add-ons. I have a power strip wired from the back of the van to the inside that could be used to trickle charge both batteries when plugged in though.

You're also right about storage, I'll have to learn how to make sure the batteries are kept at a certain SOC. And it seems like normal camping usage would probably fall between 20% and 80% most of the time. Might be an argument to stick with a 50A DC-DC charge controller rather than a 100A one (that would be tough to maximize anyway without an incredible alternator, like the 180A or 270A high output ones!!).

Also agree with the little jumper. Heck, they are small enough nowadays that it actually doesn't really make sense to make a complicated system to trickle charge the starter battery from the LifePO4. Might as well carry a small jump starter battery that can be used elsewhere. Ours can be recharged via USB too, so the LifePO4 can top off the jumper if needed.
_________________
Guillaume, Jennifer & T3TRIS
87 2-knob Syncro
- 94 Subaru EJ22, 225/70-R16 CLK 16x7 ET37
- Transaxle rebuild, Mexico paint job, Front end rebuild, 320Ah LiFePO4 Battery

[Sodo]

I’d say don’t worry much about charging the shortest time to charge 320 from empty to full.
The number of times that you camp 8 days then drive - then camp again 8 days, is seldom.
You can wish for that.👍🏽
Or its a breakdown.

99% of the time you will camp 1-2 nights then drive a few hours.

With 130A available, the Amps to the battery is the capacity of your DC-DC converter. I bought a Renogy 60A but would like a 40,50A charger for a little smaller size. I often see 55A charging reported by the Overkill app (from this 60A Renogy.) 55A on 150AH battery is .42C.
Whatever.
I bet .25C would be fiine or even less since I have Solar too.
Problem is…..solar is kinda fun.
I have to turn off the alternator charging to have any solar fun.
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[T3TRIS]

[mitch5]

I am currently running the new renogy 50 amp dc-dc charger. So far i have only been using it for alternator charging but it has been flawless. For the price i think is worth getting the dual setup incase you want solar later.

Im running a 280 ah diy lifepo setup too, the overkill bms has great features for monitoring although the app translation can be goofy. The extra capacity has totally changed how i do trips and is worth every penny.

Personally i would consider installing the battery in the cuby next to the water tank on the floor. It's a more central location for wiring and access is great as you have a door and can remove the top panel if you need full access. I currently have the battery,inverter,fuses and dc distribution block in there. The cabinets are all wood so it makes mounting stuff a breeze.

I keep spares and parts shoved under the driver seat since its a good spot to squish stuff

[jimf909]

What a great thread. Thanks for posting your thought process, OP.

I'm not sure if Howesight was the first with a 300+ah battery bank but his examples of the benefits in the cloudy NW have me aiming for a mega-bank (is >300ah mega?) when my LA batteries finally quit.

Looking forward to more from the OP on this.

p.s. solar is indeed fun
_________________
- Jim

[T3TRIS]

[shagginwagon83]

Sweet thread. I currently have a 150aH lifepo4 under the drivers seat along with a 40a Renogy DC/DC, paired with 200w rooftop and 130w portable.

I bought the CATL 310aH cells earlier this year due to insane price (and was worried about future import tax). I still have to install this.

I actually bought the 60a Renogy originally (new, open box PM me if you're interested), but chose not to install it due to size AND after I found a statement in the Renogy manual

[T3TRIS]

[1988M5]

https://www.youtube.com/watch?v=jgoIocPgOug&t=287s

Shows the danger of overheating your alternator at idle/ low rpm due to overheating.

BK
_________________
1991 tin top GL
2002 Winnebago Vista. VW VR6 24V Eurovan front clip powered class C 21' RV.
Some BMWs.

[kguarnotta]

good thread - I just wanted to add my experience -
I really liked the idea of the battery under the driver's seat. After doing it, and realizing the cold temp effect - and how tight the battery is in that space (I have the 120 AH battey) I would not do it that way again. Next time, or if I redo it - I would go under my bench seat (I don't have a westy kitchen setup, just the weekender type package).

Under the bench allows for a much bigger battery for a minimal price increase, the battery stays warmer - and is easier to access.
_________________
-Kevin
Lincoln, MA

'86 Triple Knob Syncro w/EJ22
'78 Westy
'69 Single Cab
'65 Kombi - EZ-Camper

[shagginwagon83]

[T3TRIS]

[shagginwagon83]

[Butcher]

How many alternators do fry with lithium battery charging? I bet not many.

I too can post a video of over stressing an alternator to prove my point but what is the real life scenario? I suspect if it was a real issue, there would be more about this.

I do believe when the manufacturer builds a product, it is designed to work together. There is no reason to put a 200A alternator on a Vanagon. I've got my own solar project starting and I believe looking at everything is a good approach. A stock alternator was never designed to charge lithium batteries so to increase the capabilities is probably a good idea. Same with wire gauge and everything else in between.

So asking a stock 65A alternator to perform more than it was designed to do is probably not a good idea.

[crazyvwvanman]

The video test setup is biased to make the problem bigger than it is in our vans.
I guess that is helpful to people selling "solutions".


Mark

[valvecovergasket]

[T3TRIS]

Well, regardless of what the video is setup to do, it's definitely good to be aware of this. If anything, I am now convinced it's critical! If the goal (in this thread) is to eliminate solar panels, that means the backup solution for recharging batteries would be to run the engine at idle for a while, like a generator. If your stock 70A or 90A alternator can only provide 40A or 50A at idle, it might be an issue when charging the LifePO4 cells at a high charge rate.
Again, this is probably a non-issue for most sensible battery setups, especially ones with solar, but the idea here is to have a hefty battery system that can charge very quickly regardless of sun exposure. Without that, the system doesn't perform well enough to not rely on solar panels.
Therefore, picking the right alternator can be critical. If you're idling with everything off on your van and your charge controller is happily taking 50A from your alternator, you'll be OK until your engine gets to operating temperature and the radiator fan kicks in, demanding another 20A to 40A from your alternator. If this is not considered and your charge controller and radiator fan ask a combined 70A to 90A from an alternator that's designed to spit out 50A at idle, I can see how things would start to overheat after a little while.
Unless I'm missing something, the math seems relatively straight forward. Investing in a high output alternator could be a necessity for a fast charging large LifePO4 battery system without solar panels.
Probably a non-issue for most situations, but I wouldn't want to find out that my alternator is fried in the middle of nowhere when I was trying to top off my batteries...

[crazyvwvanman]

Look at the pulley sizes in the video and compare them to the wbx pulley ratio.
The wbx alternator small pulley turns multiple revs for each large engine pulley rev.

Even at 900 idle speed the wbx alternator is spinning pretty good.

Mark