DC to DC Charger Needed?

[68camaro]

On a E-350 Super Duty Cutaway Camper Van, do I need to replace Isolator with a DC to DC Converter to account for Lithium's different charging needs and protect engine battery and Alternator from "load dump"? I am going from two DC220-6 6V batteries to three Lithium heated 100ah.

If I need one, any recommendation and what size I should get?

Thanks

 

[Peter_n_Margaret]

Depends on your alternator.
If the delivered voltage is OK and the alternator is overload protected, adding a DC-DC charger will only reduce the charge rate available (and cost more).
Cheers,
Peter
OKA196 motorhome

 

[CMARJEEP]

Even if your alternator puts out the correct voltage to fully charge the lithium batteries I would still get a DC to DC charger so you can manage the charge profile better. If you’re going LiFePO4 they like to be charged up to 14.4-14.6v (for 12v batteries) but it’s not good to keep them there constantly. You should be charging up to that then let them float down to 13.6ish volts, which a good charger will allow you to do.

 

[helenandtoby]

You definitely need a DC-DC charger.
A) Your alternator will not put out the right voltage because it is temperature compensated. Lead batteries need that, your lithiums don't. Without the dc-dc, your alternator will send little or no charge to the batteries.
B) Without the dc-dc, the batteries can draw the maximum amps the alternator can produce. That will soon destroy the alternator.
Your truck certainly has a big alternator, so I would suggest a 50 amp unit. I have a Victron 50 amp Buck Boost unit. (Note that this is not the same as the Victron Orion units.) It works great, and never gets more than warm.
As far as float mode goes, you don't need it. If you ran your truck 24/7 for weeks at a time, it would be nice. But for you not necessary. See Battle Born's videos on why not.
So, all you need is 50 amps of nice steady 14.4 volts!

 

[Pacific Northwest yetti]

Victron Smart, DC/DC 30 amp. ( Size as needed) One of the best ones on the market. Id also recomend the Victron BMV 712. Yes they are expensive. But cheaper then killing your batteries. And the Smart makes it easy to program, and monitor.





There is a reason high end yachts use ( Victron) these. And places like OEV have switched to Victron products.

 

[68camaro]

B) Without the dc-dc, the batteries can draw the maximum amps the alternator can produce. That will soon destroy the alternator.
Your truck certainly has a big alternator, so I would suggest a 50 amp unit. I have a Victron 50 amp Buck Boost unit. (Note that this is not the same as the Victron Orion units.) It works great, and never gets more than warm.

Thanks. The Buck Boost is nice but price breaks the bank. If I wasn't occasional weekend warrior I think I could justify cost.

Victron Smart, DC/DC 30 amp. One of the best ones on the market. Id also recomend the Victron BMV 712. Yes they are expensive. But cheaper then killing your batteries. And the Smart makes it easy to program, and monitor.

I am leaning towards the Orion TR and like the BMV 712 but have a question. I ordered 3 - 100ah Lifeline Heated Lithium batteries and they have built in bluetooth BMS. If the batteries have a BMS built in do I still need the BMV 712 or is it redundant?

Also, am I correct taking out the Eaton Isolator to replace it with a DC/DC charger?

 

[fratermus]

do I need to replace Isolator with a DC to DC Converter to account for Lithium's different charging needs

The lead batts probably needed DC-DC staged charging more than the lithium does. Lithium does fine with "charge and stop".

The stop part is problematic with actual isolators (diode or FET-based); due to how they are wired in there is no easy way to stop them. If the isolator is a relay/combiner/solenoid it can be disabled at will.

But depending on DoD, how long you drive, whether the isolator is diode- or FET-based or a relay, and the voltage of the alternator you may not get to the stop part anyhow.

and protect engine battery and Alternator from "load dump"?

The DC-DC isn't designed to protect the system from load dump. It provides setpoint-based charging and current limitation. The starter battery would attenuate any dumps.

But the play is at first base: prevent load dump by not overcharging and tripping the BMS. Most default Li profiles are too aggressive, IMO, and can actually cause BMS disconnects.

I am going from two DC220-6 6Vbatteries to three Lithium heated 100ah.

Fullriver AGM? If so, I'm guessing the bank pulled something like 75A through the isolator at 50% DoD. And, based on other charging reports, that the 300Ah Li bank would pull ~100A. Not a giant jump there, assuming the components are happy with that.

Before yanking everything and buying new parts you might try it with the isolator in place.

Also, am I correct taking out the Eaton Isolator to replace it with a DC/DC charger?

An actual isolator would need to come out to install DC-DC, since an isolator sits between the alt and battery and lowers voltage (forward voltage drop through the diodes). A relay could remain in place if you wanted.

 

[fratermus]

There is a reason high end yachts use these.

Motor yachts have traditionally used dead-simple alternators with external regulation. Balmar, etc.

 

[Pacific Northwest yetti]

Motor yachts have traditionally used dead-simple alternators with external regulation. Balmar, etc.

Fair Enough, I can’t speak to all yachts. I was lucky enough to work on some nice ones. The type with helicopter pads. Making friends with the captain allowed me to spend time on the bridge and not only relegated to the infirmary. I saw a lot of Victron stuff, and use it personally. But don’t know if it was used in totality. Multi plus were common, and the GX screens that would remote monitor and control.


If the batteries have a Bluetooth BMS, you probably don’t need the 712. As it would be redudant. And if each battery has one, you allready have redunancy. I dont know the lifeline product. And of course size fuses,breakes, guage and chargers to your system.

 

[68camaro]

The lead batts probably needed DC-DC staged charging more than the lithium does. Lithium does fine with "charge and stop".

The stop part is problematic with actual isolators (diode or FET-based); due to how they are wired in there is no easy way to stop them. If the isolator is a relay/combiner/solenoid it can be disabled at will.

But depending on DoD, how long you drive, whether the isolator is diode- or FET-based or a relay, and the voltage of the alternator you may not get to the stop part anyhow.




The DC-DC isn't designed to protect the system from load dump. It provides setpoint-based charging and current limitation. The starter battery would attenuate any dumps.

But the play is at first base: prevent load dump by not overcharging and tripping the BMS. Most default Li profiles are too aggressive, IMO, and can actually cause BMS disconnects.



Fullriver AGM? If so, I'm guessing the bank pulled something like 75A through the isolator at 50% DoD. And, based on other charging reports, that the 300Ah Li bank would pull ~100A. Not a giant jump there, assuming the components are happy with that.

Before yanking everything and buying new parts you might try it with the isolator in place.



An actual isolator would need to come out to install DC-DC, since an isolator sits between the alt and battery and lowers voltage (forward voltage drop through the diodes). A relay could remain in place if you wanted.

Thank you for response, good call as I am replacing two 6v FullRiver AGM's, they lasted 4.5 years, they still work but not for long, battery dealer tested and need replacing. Probably user error for short life span.

My Isolater is actually an Eaton Smart Solenoid so I don't know if your answer changes based on my incorrect description, but I think they might do the same thing.

As you suggest, I think I'll use current setup with new batteries and test from there. The LifeLine has a good Bluetooth BMS so I'll be able to do Bluetooth monitoring.

I looked at a Balmar alternator but they don't have one for Ford e-350. I can upgrade from a 130amp to a 160 or 200 amp lower cooling Alternator, would this make sense?

 

[68camaro]

If the batteries have a Bluetooth BMS, you probably don’t need the 712. As it would be redudant. And if each battery has one, you allready have redunancy. I dont know the lifeline product. And of course size fuses,breakes, guage and chargers to your system.

Thanks, I also did speak with Lifeline and they confirmed with their BMS no need for 712 or other.

 

[fratermus]

My Isolater is actually an Eaton Smart Solenoid so I don't know if your answer changes based on my incorrect description, but I think they might do the same thing.

They do the same thing but {operate and are installed differentl}, affecting how we direct-charge lithium. IMO the solenoid is easier to work with here since it can be manually disabled by disrupting the control circuit (IGN, D+, whatever) and does not have to be removed if you install DC-DC later.

{Edit: I have solar helping out so I usually disable alternator charging when the bank gets up to ~13.7v. If I didn't have solar I might let it ride to ~14.0v There's a HVD that would automate this process if I ever get around to installing it..... It's easy to catch 13.7v, less easy to catch 14.0v since that's on the upper knee when things start happening fast}

As you suggest, I think I'll use current setup with new batteries and test from there. The LifeLine has a good Bluetooth BMS so I'll be able to do Bluetooth monitoring.

I had planned on installing a DC-DC when I went from lead to lifepo4, but my solenoid (a VSR) works fine. The bank charges at voltages/currrents that make the battery and alternator happy.

I will say that charging current would be more consistent with a DC-DC. 50A right up to Vabs. With a direct connection it will charge harder at lower SoC and slower at higher SoC, like the AGM. Because of the broad flat middle of the LFP curve the taper will likely be less linear than with AGM.

I looked at a Balmar alternator but they don't have one for Ford e-350. I can upgrade from a 130amp to a 160 or 200 amp lower cooling Alternator, would this make sense?

External regs don't play well with the chassis, from what I understand. They'd be used with a secondary alt or on solo alt that does not talk to the ECU (like on a boat).

I'd see what the existing install does before investing in new gear.

 

[broncobowsher]

I would do a DC-DC for no other reason than current limitation. Lithium can absorb massive amounts of power. Alternators running sustained full output tend to not be happy and die quick. DC-DC can be used to throttle back the charge rate and make the load on the alternator a manageable sustained load.

 

[Pacific Northwest yetti]

There is also a write up here, With really good info. It was done by K Pawley. Who started, owns and operates Zero Declination. A company in Reno that specializes in Camper electrical systems, and Lithium upgrades. Some specific to FWC. But the info is transferable. Full Disclosure, my brother owns the shop.

https://forum.expeditionportal.com/...and-switching-to-lithium.236905/#post-3119988

https://www.zerodeclination.com/