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Second Alternator Charging Lithium Battery Bank

brianjwilson

Some sort of lost...
I'm hoping someone smarter than me (shouldn't be too hard to find!) can help me out.

I'm looking at a 2021 Ford E450 chassis, with factory second alternator (157 amp/hr). I want to use the second alternator to charge 4X 100 amp/hr battleborn lithium batteries, which will have their own battery monitor system, separate solar charger, inverter/charger etc. All of the "system" components would be from victron.

I reached out to an install company, and they recommended a Victron 230 Amp Cyrix based "battery combiner". https://amsolar.com/rv-battery-accessories/98-altcli230

Victron's component descriptions are really lacking. It appears to be designed as a battery combiner and not MPPT style charge controller/converter, so it would not top off the lithium bank. There is also a concern (I believe) that the lithium batteries would draw too much amperage at low idle and overheat the alternator potentially. Could there also be damage caused to the alternator with a sudden shut off from the cyrix based combiner?

Victron does offer 60 amp MPPT Orion converters/chargers that could be run in parallel.

My goal is to be able to comfortable run air conditioner off of the second alternator (through 3000w victron inverter) while driving (estimated 100 amp draw on battery system).

Any feedback would be greatly appreciated. This will be my first time with a lithium bank, I don't want to screw something up with a "standard" alternator trying to charge a large lithium bank.
 

Peter_n_Margaret

Adventurer
Get the alternator output the same as the float voltage of the batteries and connect them direct. Set and forget.
If you are happy to monitor the battery voltage the alternator voltage could be a bit higher for a higher charge rate.
No need for any fancy gear beyond a fuses each end and a solenoid switch.

If you are only running the aircon and only while driving then one battery would be adequate and it could just as easily be an AGM at a fraction of the cost.
Cheers,
Peter
OKA196 motorhome
 
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ExpoMike

Well-known member
Having done some researching into this type of setup for my M1010 (which has dual alts), I had looked into dedicating one alt to the LifePO4 house packs, independent of the vehicle system. A few things I have found I would consider during the build out of a stand alone house system.

First, with any LifePO4 (i.e. Battleborn) pack that have their own BMS, which could disconnect the battery from the charging source, is to have an alternator protector. If the BMS disconnects your alt (overcharge, low voltage, over temp, cold temp, etc) for any reason, you will blow your alt as they are designed to have a battery always connected to them during charging. Simple Sterling unit seems to be the ticket to prevent that. https://shop.marinehowto.com/products/sterling-power-12v-transient-voltage-protection-device

Second, LifePO4 batteries will charge at the max available input they can pull. Ideally you want to limit that to no more than 1C rating (in this case the BB batteries would be 100ah each, total 400ah with 4). Your alt will never survive that rate. Also, to keep from overheating your alt and burning it up, you really don't want it to run continuously at more than 60% of rate output. This should keep it in an acceptable temp range but try to push 75%+ and it will not last long. If yours is rated to 157ah, I would limit it to 100-110ah max. You can do this with a couple DC-DC chargers rated at 50ah in parallel. You want to make sure you get ones that are specifically setup to run LifePO4 batteries and ideally have adjustable parameters.

Third, you might want to find out what the rating is of your alt at idle/low RPM's as it might be rated at 157ah at a higher RPM range then you will be using. It might only be pushing 60ah at low RPM and having your DC-DC chargers setup to push more than the alt can put out will run it at max output and likely burn it out quickly as well.

LifePO4 batteries are a game changer but you cannot treat them like a standard FLA or AGM battery. This includes all of your charging and any solar system setup. You might need to look at a aftermarket high output alt along with the above stuff. For me, I decided to keep my charging limited to 40ah from alt source and keeping a FLA battery in between the alt and DC-DC charger as the buffer. This way if the BMS disconnects the LifePO4 bank, the FLA will still be connected and prevent any damage to the alt.

You might want to check out this forum for a lot of good info about LifePO4, solar, DC-DC charging and basically anything related to these systems. There is a lot to digest there. https://diysolarforum.com/

Good luck.
 

DiploStrat

Expedition Leader
Having looked at some of this, I would offer.

-- My Chevrolet had twin alternators, but I could never find a detailed enough wiring diagram to let me know if I could safely separate the two. If you can simply add a new, dedicated alternator - which may be possible with a bracket from the folks who cater to the head banger car stereo crowd, it should be relatively easy to fit a marine alternator with a dedicated voltage regulator set for lithium.

-- Direct connection of the lithium bank to the factory alternator(s) can be difficult as, 1) a deeply discharged lithium battery will pull a LOT of current. I tested a fully discharged 100Ah battery and it pulled well over 95A, melted the jumper, etc. 2) Some alternators, e.g. Chevrolet, will zoom up well over 15v when it gets cold. Great for AGM/FLA, but possibly deadly for lithium.

-- I have not tested it, but a sudden disconnect, as might occur if the BMS activates, is said to be dangerous for alternators.

All of that said, a dedicated alternator is really slick and some, e.g. Winnebago, are going this way.

The net result is that lithium provides a whole new justification for battery to battery chargers (B2B).

-- A B2B can control the charge voltages/currents to match the needs of lithium batteries. Specifically, a B2B cannot draw more that about 20% above its rated output. (That is why a 40A B2B is fused at 60A, etc.)

-- Most B2B don't care if the battery is present or absent and will prevent any transient being passed to the alternator.

Good luck!
 

ExpoMike

Well-known member
-- Most B2B don't care if the battery is present or absent and will prevent any transient being passed to the alternator.
Not sure this is the actual case. Yes the B2B won't care but I do think the alternator will. There might be some that have built in protection but other might not. Not sure I would want to test that on my own system. :)
 

DiploStrat

Expedition Leader
In the case of my REDARCs, this was confirmed with the factory. Nothing passes back to the alternator. And, in any case, it is moot as the starter battery is still in the circuit. (You could wire a B2B directly to the alternator, but most of us wire to the positive terminal of the starter battery.)

I would be surprised if this was not the case with Sterling Power as well, but I have not tested.
 

Buddha.

Works too much
I would just use a B2B(DC to DC) charger, or two, coming off one of the batteries. I don't see a reason to isolate the alternators and draw off of just one. Their voltage is computer controlled and not easily altered for lithium profile.
The dual alternators should be able to keep up with a 100amp load at idle I think, or you could set the engine at a higher idle.
Keeping the alternators hooked up to the batteries in stock configuration would prevent any weirdness with the lithium's BMS disconnecting right?
 
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peculierboy

Member
The Mortons on the Move bloggers had some issue with the newer Ford alternators oveheating while charging Lithium batteries, https://mortonsonthemove.com/truck-camper-lithium-alternator-charging/ and determined a B2B charger was the better way to go, he's an electrical engineer and goes into some detail on why. Sterling makes a 120amp B2B unit if you really want the amps, not cheap, https://www.sterling-power-usa.com/...probattc-batterytobatterycharger12vto12v.aspx We have the 60 amp Sterling and are very pleased with it. At idle on our dual alternator RAM it cranks 60 amps out no problem.
 

brianjwilson

Some sort of lost...
Thanks for confirming some of my thoughts, guys. I’ll check out the sterling unit.

My immediate thoughts are;

1) forget the second, dedicated alternator. Stock alternator is 230a. Run either two parallel victron 60 amp dc-dc chargers or a ctek unit with smart pass (140amp total) that can be set to lithium charging. But I could really be pushing the alternator limit especially at idle. Or,
2) Install the second alternator as stated above. 60 amp dc-dc charger on both the main alternator AND another on the second alternator. This would not be cheap, but ensure that I could charge up to 120 amps to the lithium bank pretty reliably and safely without pushing the limit of either alternator. The 120 amps would allow me to run roof AC on the inverter as well without concern.
 

Peter_n_Margaret

Adventurer
If the batteries are full and the alternator is connected and running and you switch on the A/C, the alternator will supply 100% of the power required, NONE of it will go either into or out of the batteries.
Cheers,
Peter
OKA196 motorhome
 

DiploStrat

Expedition Leader
Yer overthinking this a bit.

-- While the new CETK 250 can charge lithium, it is not clear that the SmartPass can be used with any but lead acid. I would check with CTEK.


-- The Victron Cyrix-Li is a smart relay with higher voltage settings to work with lithium batteries. The problem is not that it will not "top off" the lithium bank, but rather that the vehicle voltages, especially if temperature compensated, may be too high and that the draw of a deeply discharged 400 Ah bank may be too great for your alternator(s). As an alternative, Battle Born sells a smart relay that shuts off for 20 minutes every 15 minutes to allow the alternator to cool. LiFePO4 Battery Isolation Manager (BIM) | Battle Born Batteries It appears that this device will also act as a maintenance charger for your starter battery when the camper battery is above 13.5v. Nice feature.

-- A single battery to battery charger, rated at between 50 and, say. 75% of the rated output of your vehicle's alternator(s) rating should be perfect.

-- REDARC has 50a units which can be paralleled and Sterling Power makes single units of up to around 100A.

I would go with a B2B setup and (hopefully) be happy! (N.B. I am running a pair of REDARCS into 800Ah of lithium. So far, all of the smoke is still on the inside. ;))
 
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I would recommend going with a single Sterling unit. I have used quite a few Sterling products over the years, mostly in marine applications, and they are high-quality. The biggest issue is keeping them well-ventilated. They need a LOT of airflow. Connect it straight to the starter battery with appropriately-sized copper wire and go. If you want to add the second alt, fine, but keep it tied in with the rest of the system. Separating it adds unnecessary complication.
 

RAM5500 CAMPERTHING

OG Portal Member #183
Yes, i went through this exact conundrum on my 2020 Ram5500 project.

I special ordered my truck with the Dual Alternators for 440amp total thinking i would separate them, one for truck bats, one for house bats.

I quickly learned this is WAYYYY more complicated than it seems, on the newer trucks.

DISCLAIMER: I am NOT an expert in this field, and wont claim to be. Also, everything i have found out is based on the Ram 6.7 cummins, i have no idea if the Ford alts are setup the same way.

However, i have some friends that are, do this for a living, and even spent a couple hours at my local dealer talking with an OG guy there that loves my project, so gives me a bit more love than the usual customer.

Bottom Line i found out: The dual alternators are controlled by the computer to work together and split the charging (somewhat) and disperse the duties to cut down on heat and other things. If one fails, the other one can pick up the slack as needed until repaired/replaced.

There is a process to electronically remove the second alternator from the computer by deleting the sales code and that essentially has the truck setup as if it came with just a single one from the factory.

Electronically anyway... You still have a complicated array of wiring in the loom for alt 2, and redoing it all to serve a different purpose on a brand new truck just seemed like way too much headache and unnecessary work that may possibly effect warranty.

After lots of research, and going back and forth, i settled on a Sterling 60amp B2B and so far, it has been working flawlessly throughout all the crazy tests i've been putting it through. My Victron smart shunt, shows the Sterling is actually charging at the 60amps it claims as well.

This is all for a 300ah lithium LifeBlue battery. So far, its been great for all my needs (my entire truck is setup for everything electric and no propane). But now that summer is coming, and i will be running the AC a bit more, i will be keeping an eye on the usage and determine if i need more battery.

A friend of a friend runs a residential Solar company and builds his version of Tesla Walls and he's been yapping about building me a big silly battery bank for the camper. If i end up doing that, i will likely switch to the Sterling 120b2b and then i'd basically be setup for whatever i could possibly throw at it.

End of the day, B2B are simple to install, setup, and work great

Careful with the Victron and RedArc versions folks are using, for what they cost they arent available in higher outputs.

There is absolutely no reason you shouldnt put the biggest one you can fit on your setup. I believe the Victron and RedArc max out at 30 or 40amps or so.

Sterlings are available up to 120amps, its kind of a no brainer (i went with their 60amp at the time of my build because the 120amp version was on backorder forever, its available now)

 
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DiploStrat

Expedition Leader
Way back when, I looked into trying to separate the two alternators on my 2013 Silverado and, like you, concluded that it was too hard. The good news was that the Chevrolet's charging system was so good that all I needed was an intelligent relay.

Sterling B2B units are available in more sizes and are infinitely adjustable, should you wish. (And know what you are doing.) They tend to be physically larger and require lots of air flow.

REDARC units are basically 25A & 50A. They offer fixed profiles and not adjustable beyond that. They are basically sealed blocks of epoxy and can, in some cases be mounted under the hood. Some units also allow solar input, but note that in this case it only spares the alternator, it does not increase the output.
 
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