Alternator charging House Lithium battery

[loverofpeace]

Looking to add a DC/DC charger to my T3. Has anyone had success running the 30a version of either the Renogy or Victron on their stock alternator? I have a stock 65a one and am wondering whether it’ll be enough to run this without dying an early death.

[baltik]

I have no real world experience in your setup (I run a 30a renogy with a subaru 110A alternator) but would steer you towards a 20A version, I just think you are going to be pushing a very aging electrical system to its bleeding edge

[OldSpice]

how many amps are getting pushed through to a normal drained AGM aux battery?

im also trying to plan out upgrading aux battery system.

[nmerrill]

I installed a lithium battery, and a monitor inline. 4Ga wire between start and house battery (through blue sea ACR)
Figured I'd see what kind of Amps it might draw before I pulled the trigger on a Dc/DC charger.
If I recall correctly, I saw 38 amps once.
I'm running a 120A alt I think (audi)
Installed DC/DC 20A charger shortly later.

[dobryan]

[pnwkayaker]

Have you considered the Redarc BDCD1225D 25A DC-DC charger?

I have installed one to charge my 50AH Lithium battery and so far, it's performing great. It has also an MPTT solar charger that I have connected to a 100w panel, and the charger takes care of all the balancing between both power sources.

There's also a 40A version (BCDC1240D) if you need higher amperage.
_________________
87 Syncro Westy EJ25 ("Tardis")

Seattle Meetup at Marymoor (link)
A collection of Simple Useful Mods (SUM) (link)

[nocreditnodebt]

I cycle a group31 Northstar TPPL AGM. Very similar to Odyssey.

Thin plate pure lead, 103 AH and 1050 CCA

It is a beast. I have fed it 134 amps of plug in charging source when depleted to just under the 50% range, and that was not enough to instantly bring its voltage to 14.7v.

After several minutes of voltage climbing towards that, the breaker feeding the 134 amps of charger blew and I then continued with 94 amps for several minutes before voltage did climb to 14.7 at which point amps tapered.

Since I can manually control the voltage my alternator is told to seek, this battery can easily max out my 120 amp alternator as it will take ~65% more amperage when told to seek 14.7 compared to 13.6v.

Alternators get very hot very quickly when maxed out, or nearly so
Above 220F is the danger zone.

My Non VW van, at highway speeds keeps the maxed out alternator under 140f, but under 25mph maxed out, and temp quickly shoots towards 180f+.

Parked idling it can only make ~50 amps but still temp shoots up quickly as well as does the temperature of my external voltage regulator as it sends maximum field current to the rotor.

I've No data on a VW alternator when it is working hard feeding depleted
healthy battery capacity, but if you intend to work it hard, then force feeding it/ Ducting coolest possible ambient air to keep it cooler will help its output and longevity to some unknown degree.

I use this Northstar AGM as it has no Issues with huge recharging amperages, and seems better off when it regularly receives them from a well depleted state. It can and does push the charging sources to their limits, and All I can do is insure they and the battery do not get too hot, then twist my voltage dial down when they do.

So knowing when and where they do needed to be established.

Heat generated is the limiting factor, whether it is alternator, cabling, Dc to Dc converter, or bttery or its BMS, if Lithium.

There are K type thermometers, like which come with many digital multimeters. I use Arctic silver thermal epoxy to adhere the sensor to the alternator casing, then use Nashua Flex fix and a reflextix like product to insulate it from airflow.

Actual Data is so much better than guessing. Without tools to actually collect data, all one can offer is a guess.
With so many variables, guesses even when well intentioned, can be wildly inaccurate, and cause failures.

Sometimes seeking maximum safety, compromises function. I'd be quite annoyed if I had to limit my charging sources to save the battery, or limit the charging sources to save themselves. or both.

[rmcd]

Might look at this. Before you freak on the price you should consider all the pieces and parts you will have to engineer, source, make work together and buy to get the same functionality.

https://smartercharger.com/products/140a-off-road-bundle

Dc dc charging, combining and separation up to 140a
MPPT controller
Lithium battery and multistage Charging support
And so on.
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VW LT40 build. Like a Vanagon but 30% larger in every direction and 40% slower even in metric.
https://www.thesamba.com/vw/forum/viewtopic.php?t=749359&highlight=

[CarstenR]

Hey all, as I learn more and more about this mysterious world of Westfalias and campervans, I'm starting to revive some old threads- I hope that's not a problem!

I have the same issue as the OP did back in 2020. I'm running a stock alternator on my 1981 Westy (the Opa Bus), don't have A/C, and even though I plan to replace every bulb inside and outside with LEDs and run my Dometic off propane and not 12VDC, I'm still a little concerned with having my 100Ah LifePo4 battery draw so much juice so as to fry my alternator.

Since I am adding a solar panel to the Opa Bus and plan to run the Renogy DCDC30S 30 amp DC-DC controller with MPPT, I believe that the Renogy will limit the draw on the alternator to 50% of maximum (with 50% draw from the solar panel), so 15 amps. Did I read that correctly? If so, should I feel confident that the stock alternator won't overheat from a 15 amp draw, even if I find myself stuck in traffic at idle?

FYI I don't plan to have any additional power hogs like a thumpin' audio system or underbus neon lighting ;~))...

Thanks,

- Carsten
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Carsten Ramcke
Allen Park, MI
1981 Aircooled Westfalia: the 'Opa Bus'

[Sodo]

When the DCDC30S senses voltage from the solar panel it will limit the draw from the alternator to 15 amps.
If your panel is in full sun you get about 7 amps so 22 amps.
If your panel is in partial sun then you get 15A plus a few.

At night, when the panel voltage is zero, the DCDC30S will draw the full 30A from your alternator.

Incidentally you should add a dedicated ground from your alternator direct to the chassis.
That LiFePO4 battery, when its low, is gonna suck hard from your alternator, for a long time.
You want to ensure there are no lost volts.
And no stray amperage finding it's own way to ground due to 35 year old corroded connections.
Such as ruining your transmission bearings or wheel bearings and thru your parking brake cables etc.
If you add a dedicated ground then you only have to inspect two connections and ensure 100% of the amps willl travel there.

Here's a pic about slow starters, but it describes updating a (degrading) 35-year-old ground path.
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'90 Westy EJ25, NEW oil rings (!) 2Peloquins, 3knobs, SyncroShop pressure-oiled pinion-bearing & GT mainshaft, filtered, cooled gearbox.
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered original gearbox
....KTMs, GasGas, SPOT mtb

[E1]

So far as adding anything beyond an isolator, some circuit breakers, and a good on-panel controller if on a portable…

Personally? I think most everyone way overthinks this — and over complicates the process accordingly, mostly just to ensure more stuff can fail.

We’re run stock 75 amp alternators to first a 100 aH AGM, then to a pair, and for five years to a single 210 aH AGM. We gain a half-volt of real battery charge in an hour of driving, and the last alternator failure was a rebuilt NAPA 60-amp — about 2,000 consecutive days of continuous travel ago. And we fully or mostly discharge our house battery on many more days than not.

I’ll do the same setup when getting a lithium, when this 5 year-old battery fails — though its cold cranking amp readings are still near its new rating.

Save money, save weight, save space, save wiring, and stay simple. And maybe carry a spare alternator with a mounted pulley because it makes sense anyway.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans

[CarstenR]

Hey E1 and Sodo, thank you for your replies.

I appreciate the dedicated ground strap idea, Sodo. This makes [common] sense to me and I will be following your example. It seems to me this mod not only helps with efficency, but reliability and longevity of the starter, and possibly alternator and battery as well.

E1, as I understand it, LiFePO4 batteries draw differently than AGM batteries, as Sodo mentions. And although I'd like to upgrade the alternator, I think my options with an air-cooled Westy are limited. Also I'm already going to struggle with power, so the less load my alternator puts on the motor, the easier it will be to make it up to Clingmans Dome in the Smokies.

I read a statistic that states your house battery should never draw more than 50% of your alternator's rated amperage, though I tend to be skeptical of these kinds of blanket statements, especially as they apply to 40-year-old technology.
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Carsten Ramcke
Allen Park, MI
1981 Aircooled Westfalia: the 'Opa Bus'

[GoEverywhere]

[E1]

Hi, Carsten:

The guy who installed the house system on our first van really knew what he was doing… and yet, he insisted our starter and house batteries not only had to both be AGMs to charge well, but the *exact same* batteries. So we put in two $300 AGMs, 1100 Ah each. He had nothing to gain from this, as he didn’t sell batteries.

If you can’t upsize the alternator, there are aftermarket voltage regulators (from Volvos, I think) that can enable sending 14.4 volts to the batteries instead of in the 13s.

A couple years later, we heard otherwise over and over — from other full-time travelers — so replaced the AGM starter battery with a typical, 650 aH lead acid and the other AGM became a second house battery. No problems keeping all three charged, but we’d also added a new Bosch 75 amp alternator and never lost another regulator as we’d been doing on rebuilt 60-amp NAPA alternators. But using two house batteries was a constant battle, in never being identical in charge and performance, and why we will never run two instead of a larger single again.

I, too am very skeptical on this topic. Lots of theories and complications, mostly sold by the industry and well propagated online.

Admittedly, I’ve never run a lithium for a variety of reasons, but will next time — partly to add capacity, but mostly to lose 60 lbs. It could turn out we do need a more-precise method to do so, but until then I will remain skeptical… but so far, lots of use in the wilds has proven me right (been over maybe a thousand high passes under load, too).

Please let us know what you do and how it all works. And Yes, Sodo’s ground information is on my To Do list, sometime.

Another tip is to not buy a large inverter like we first did, an 1100 watt based on a bus parts supplier’s posted advice. It sucked battery power endlessly and ruthlessly. Ours is 600 watts now and can run a blender.

So far as power needs, we run a Macbook and a 27” monitor most days, all day, plus a powered speaker, then we watch videos at night with the speaker, and 200 watts of solar keeps up even in winter. But, we’re in the desert, and use an ice chest, so being in the East like you would probably have me wanting a lithium for more storage on cloudier days.

It all comes down to what level of power you need — and some serious thought to power conservation as well. Worth noting is we run only portable panels, they’re miles more efficient, our last one lasted 125 months of constant use (Zamp), and we like to park in the shade. We just bought two 100w portable Zamps a month ago, and they’re spectacular.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans

[GoEverywhere]

[E1]

Thank You for that experienced view… I’ll never think about that “mod” again!

The above post about your alternator upgrade is also awesome!

And Yes, when our rebuilt alternators’ voltage regulators failed, I’d see fleeting spikes at over 17 volts. Once, a battery got hot, so no more NAPA rebuilts for us (although, our spare is a fresh version of exactly that, will only temporarily use until replacing with new).
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans

[MarkWard]

We have a Lithium 100 amp battery. We use the Dometic on propane. We have an oscillating 12 volt fan and have converted the kitchen light to LED. For reading we use out rechargeable head lamps. Maybe some stereo when camped. The biggest hitter is probably our diesel heater.

The most we have used in 24 hours is 20 amps. Our Renogy DC to DC 20 amp charger recovers the battery in an hour of driving. It sounds like your use would be similar to ours. We have not been able to justify adding solar. We always camp in shade when possible and often set camp end of the day.

Having done a few versions of cabin batteries, combiners, switches, I have found the 20 amp Renogy dc to dc charger to be the best setup so far. I can see where an AGM battery would also benefit, because you can set the output voltage and it’s stable and conditioned. Your results may vary.

[CarstenR]

[Crooked Designer]

I have a 110A alternator (subaru) and was advised to do the 20A vs 30A Renogy. Not sure if that was the right advice, but the 20A has been plenty for my 100Ah House battery. I almost never turn on the DC to DC charger tbh.. (I have a toggle switch on the D+ signal wire) because I have 200w of solar up top and that does an amazing job of charging while I drive. (I too camp in the shade in the summer) But, if its raining, or if I need both to charge faster, I love it. I don't think I've ever wished for the 30A. Fridge, stereo, and 3-4 devices charging constantly.
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'85 Westy full camper, Subaru 2.5L, 5 speed SubiGears + 5speedbus shifter kit

[Howesight]

Hey Carsten:

I agree with the posters above who recommend a lower current DC-DC charger in the 20 amp range. This will protect your alternator and also be just fine charging your 100 A/h LiFePo4 battery. 30 amps or 40 amps would be too much.

We have a 280 A/h DIY LiFePo4 battery and use the Redarc 40 amp (nominal) DC-DC charger which also acts as a solar charge controller. The actual alternator charging output is around 43 amps. I am careful not to have the Redarc switched on for long periods when the engine is idling and other large electrical loads are also pulling current on the alternator. At normal driving RPM's I do not have to limit in this way. We have a 1994 Subaru SVX 3.3 engine which came standard with a high-output alternator, although I can't recall the rating at the moment.
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'86 Syncro Westy SVX