Anyone using both lead acid and lithium (battle born) through d250s b2b charger?

[battlebornliion]

Hi everyone!

Here is some info that is not in the marketing materials. The BMS is not bucking or doing any voltage regulation. It is simply monitoring the voltages, current and temperatures and acting as a high current switch, when things are out of whack. Charging and discharging circuits may be opened independently. For each, we have a bunch of high-current MOSFETs (along with some snubber circuitry) doing the switching. Basically, the charging switches will open if one of the following is detected: one cell exceeds a prescribed high voltage, the cell temperatures exceed 140F, the MOSFET temperatures exceed 170F, the charging current exceeds 200A for 0.5s, or 100A for 30 seconds. The discharging switches open if one cell falls below a low voltage threshold, the cell temperatures exceed 140F, the MOSFET temperatures exceed 170F, the cell temperatures fall below 25F (deadband at 30F), the discharging current exceeds 200A for 0.5s, or 100A for 30 seconds. High current disconnects are automatically reconnected after 5 seconds. Note that discharging is still allowed under low temp and high voltage, and charging is still allowed under low voltage. The 0.5s high current allows for initial cranking currents which typically last a couple hundred milliseconds. It's our happy medium between allowing cranking and protecting against short circuit. The BMS also has a standard passive balancing mechanism, whereby cells that are charged faster than the rest bleed current through a resistor. The batteries can be connected in parallel (provided you use appropriate cables and fittings to handle the current), and in series up to 48V.

Operationally, the batteries should be bulk charged up to 14.3-14.6V, and absorb ideally at 14.4V. The person who suggested that Li-ion batteries should not float is correct. However, some chargers require a float, and we recommend setting it at 13.6V or below, since that is below the natural float of the charged cells. The cells leak charge at a rate of only 2-3% per month, so they can be stored for long periods of time without a trickle charge.

That's it in a nutshell. We would be happy to answer any other questions. Feel free to call: 855-292-2831

 

[dwh]

Sean. Dude...

NAILED IT!

Really, that was just about the most excellent post I've seen from a manufacturer. Mad props.


Right offhand, I think perhaps a bit more clarification on this:

"Note that discharging is still allowed under low temp and high voltage, and charging is still allowed under low voltage."



About the only other thing that comes to mind immediately is more specifics about voltages - I still don't know what the normal resting voltage of the fully charged battery is supposed to be.



But good job man! Have marketing make that a downloadable .pdf.

 

[dwh]

The discharging switches open if …[snip]… the discharging current exceeds 200A for 0.5s, or 100A for 30 seconds.

Hrmm, just FYI, there is a discrepancy... the FAQ says:

"What are the current limits of your BMS?

2. 200 amps for 30 seconds (2400 watts at 12 volts) – if your device has a surge an individual battery can deliver 2400 watts for 30 seconds."

https://battlebornbatteries.com/lifepo4-bms-output-and-surge-ratings/

 

[JCDriller]

So to make matters a little foggier if I added a AC/DC battery charger for topping off the batteries at home when the 4Runner is parked in the garage for extended periods of time with no solar, what unit is recommended to charge the BB battery? The instructions for the d250s show I hook the charger up to the service battery and the smart pass will the pulse charge the starting battery.

I guess I'm not sure how close to a lead acid battery the BMS in the BB battery makes it act. Would it prefer a lithium charger or does the bms make a standard lead acid charger a better choice?

 

[DiploStrat]

Doesn't Matter That Much

Float charging is really critical for lead acid batteries and the entire D250S/SmartPass architecture is set up for a standard AGM battery

For LiFePO4 you actually don't want a float.

So, the instructions for leaving a lead acid battery set up for an extended period call for some form of float, for example, shore or solar. For LiFePO4, the instructions are just the opposite - charge the battery, kill the loads, and DON'T float.

For routine, overnight top ups, almost any decent shore charger should be fine as long as it is smart enough to shut off or float once the battery voltage and amp flows hit their targets. An old gel cell profile would be fine.

CTEK and others make good shore chargers that should work. Battle Born may also have some recommended brands.

N.B. The BMS does not make a LiFePO4 act like a lead acid, it merely tries to protect the battery from damage.

LiFePO4 is a whole new world. "Everything you know is wrong!" (Firesign Theater.)

 

[JCDriller]

Float charging is really critical for lead acid batteries and the entire D250S/SmartPass architecture is set up for a standard AGM battery

For LiFePO4 you actually don't want a float.

So, the instructions for leaving a lead acid battery set up for an extended period call for some form of float, for example, shore or solar. For LiFePO4, the instructions are just the opposite - charge the battery, kill the loads, and DON'T float.

For routine, overnight top ups, almost any decent shore charger should be fine as long as it is smart enough to shut off or float once the battery voltage and amp flows hit their targets. An old gel cell profile would be fine.

CTEK and others make good shore chargers that should work. Battle Born may also have some recommended brands.

N.B. The BMS does not make a LiFePO4 act like a lead acid, it merely tries to protect the battery from damage.

LiFePO4 is a whole new world. "Everything you know is wrong!" (Firesign Theater.)

Ok, thank you, that makes since. I was thinking about being able to keep my ARB running for a month while I'm out of town and it's parked in the garage. Maybe the best thing to do is just keep the 110v plug of the ARB plugged and don't worry about charging the batteries on a AC/DC charger. Or I can hook the AC/DC charger up to the starter battery and bypass the d250s/BB battery side all together. Let the alternator and solar deal with the lithium side once i get home and go for a drive. There is so little charge leakage of the lithium I don't need to maintain it.

If all goes well I'll likely swap out my starter battery too, just for the weight savings. My JKU was a pig, I'm trying to stay weight conscious on this build.

 

[battlebornliion]

Sorry...I noticed an error in my last post! The CHARGING current is cut off under low temperature conditions. Not the discharging current. Discharging is allowed under low-temp (it actually acts to heat the cells). The reason we do not want to charge in cold temps is that the Li ion diffusion is slower when it is cold. And pumping electrons into the anode faster than the Li ions can get there could cause Lithium metal plating. Sorry for the confusion.

 

[battlebornliion]

Hrmm, just FYI, there is a discrepancy... the FAQ says:

"What are the current limits of your BMS?

2. 200 amps for 30 seconds (2400 watts at 12 volts) – if your device has a surge an individual battery can deliver 2400 watts for 30 seconds."

Each battery can deliver UP TO 200 Amps for 30 seconds. However, the current is cut off after 0.5 sec if the current EXCEEDS 200 Amps.

 

[DiploStrat]

More Kudos!

Sean. Dude...

NAILED IT!

Really, that was just about the most excellent post I've seen from a manufacturer. Mad props.

...

But good job man! Have marketing make that a downloadable .pdf.

Let me add my thanks!

I have spent a lot of time communicating with LiFePO4 battery manufacturers, trying to understand the real world issues of building an expedition vehicle electrical system around these batteries. All too often these communications have been challenging as you get some variation of:

-- "That's proprietary - just plug it in and trust us." or,

-- Information that is simply incorrect. LiFePO4 batteries are different, but not THAT different.

Some of this is because the companies are spending all of their time building batteries and don't really consider the challenges of installing or charging their batteries. (Really, they simply use a bench charger which is NOT the same as a modern vehicle, optimized for lead acid or an off-the-shelf solar controller or shore power inverter/charger.

The posts from Battle Born are a breath of fresh air, and have the advantage of tracking exactly with my (limited) experiments and the information that I have been able to glean from the more responsive souls. Thank you!

 

[dwh]

Each battery can deliver UP TO 200 Amps for 30 seconds. However, the current is cut off after 0.5 sec if the current EXCEEDS 200 Amps.

Ah, okay. I think I get it now. Lemme see if I've got it straight...

Input/output up to 100a indefinately, 101a - 200a for 30 seconds, then cuts out with an auto-reconnect in 5 seconds. Over 200a cuts in half a second and auto-reconnects after 5 seconds.


So...theoretically...

Input 200a for 30s, cut out for 5s, reconnect for 30s...endlessly until the battery
is charged and stops accepting current.

Provided, of course, that the charging system can supply 200a. A charging system with between 100a-200a potential, is going to be running flat out at around an 80% duty cycle. A charging system with less than 100a potential will just be running flat out - 100% duty cycle (until the battery is charged, which should only be an hour or three).

Ouch. What an alternator eating little monster that could turn out to be...especially running two or more of the lithiums.


So yea, it looks like a battery to battery charger is the way to go, just to keep the alternator from overheating. Either the CTEK at 20a or something like the Sterling at say 50a, and either one would also help the battery to live longer by limiting the charge current to well below 100a (well, technically...below C*1).


(Repeating here what DiploStrat already said)

IF the alternator can handle the load, a simple split-charge relay would be fine (as long as the solenoid was rated at least 200a continuous - 400a (or alernator max) with two lithiums in parallel).


ACR is a problem, because the programmed set points are all wrong. A typical ACR is going to keep the batteries tied until the voltage drops to like 12.7v - by which time the lithium is going to be pretty far down.

On the other hand, it might not be a big problem. If the cranking battery is full, then it would just be basically getting a float charge off the lithium. Power to feed loads would be coming out of the lithium until the ACR disconnected, so that's not so bad.

The questions are: A) how will it affect the lithium to be supplying a (possibly long-term) float charge to a lead-acid? And B) again, what is the full charge voltage of the lithium?

If the lithium is full charge resting at 13.8v, then that isn't going to pose any serious threat to a typical lead-acid. It's a touch high for a float voltage, but not crazy high. If the lithium is at 13.6v full charge, then that's a perfect float voltage for the lead-acid.

On the gripping hand (nerd points to whoever gets that reference), there are adjustable/programmable ACRs, and no doubt manufacturers will eventually see the light.




And I still don't know the full charge resting voltage of that battery...was it posted somewhere and I missed it? Anyone got a link?

 

[dwh]

Ok, thank you, that makes since. I was thinking about being able to keep my ARB running for a month while I'm out of town and it's parked in the garage.

It might not be a big deal. The BMS does apparently disconnect cell charging when the cells (or one anyway) get to a certain voltage.

So if you left a shore powered charger hooked up, and a fridge...

Theoretically, the BMS would cut the cell charging when the battery is full, and then the fridge would be drawing power from the shore charger.


Hrmm...

An Iota DLS (NOT the -X variant) and withOUT the IQ/4 smart charging brain might be just about perfect. (Forget the IQ/4 - it makes the voltages too high. Perfect for lead-acid, too high for the lithium.)

With the "dual-voltage" dongle unplugged, it's just a 13.6v regulated power supply. With the dongle plugged in, it becomes a "two-stage" charger that bulks to 14.2v and then drops to float at 13.6v.

A 45a or 55a model for a single 100ah battery would put it in the "C*.5" sweet spot that Battle Born recommends for long life.

Okay sure, the 14.2v bulk is a touch below the 14.4v that Battle Born recommends, but that just means it'll take a bit longer to reach full charge, and it's on shore power so time doesn't really matter, and it'll take it easier on the cells and BMS.

But the 13.6v float voltage is what they recommend to stay below full charge voltage and basically just avoid floating.

http://www.iotaengineering.com/power.htm



The only real gotcha I can see there, is it might drop to float before the lithium reaches 100% charged.

BUT, unlike a lead-acid which needs to be at 100% to slow down sulfation for long life, lithiums (if I understand this correctly), actually live longer if you don't keep them pumped up to 100% all the time.

And the 13.6v float would be plenty to run the fridge without drawing down the lithium.


The only question I'd have is: Exactly what will cause that unit to jump back up into bulk stage after it's dropped to float?

You might want to see if you can get them to answer that before buying one.

Or maybe Battle Born can get one and test it and publish the results.



(I said "not the -X variant" - the new model - which I said only because I could not easily find a description on their site or in the manual describing what the bulk voltage is, and couldn't tell right offhand if it does the "dual-voltage dongle" thing. For all I know at this point, it might be perfect, but maybe not.)


[Note to Battle Born: Iota is VERY popular in the RV/boating/overlanding communities.]

 

[battlebornliion]

If you charge up to 14.4V and then disconnect the battery, the open circuit voltage will sit at 14V for a couple of hours, and drop steadily to 13.5 - 13.6V after a couple of weeks. Discharging a bit, like by trickle charging a lead acid battery, takes it down to 13.4V pretty quickly. So an open circuit voltage of 13.4V reflects a full battery. An open circuit voltage of 12.7V is a pretty empty battery. So you are correct that there are issues with ACR. It will drop to 13.4V quickly upon discharge to the starter. But if the disconnect voltage is 12.7, then the Li-ion bank will trickle charge the starter until it is near empty. Depending on the trickle current, it may take a long time to get there, but it will eventually happen. It may be a better idea to just have a provision to start the engine off of the house batteries if the starting battery is dead.

Although our Li-ion (LiFePO4) have a charging profile that exhibits the same voltage range as a lead acid batteries, Li-ion batteries are low impedance and spend most of their time in bulk mode, whereas lead acid batteries are high impedance and spend most of their time in absorption mode. This means that your Li-ion bank will suck up whatever your alternator will deliver until they are full. So you need to design your system so that your alternator does not overheat (undersized alternator), or your battery does not charge too fast (undersized battery – we do not want to exceed a 1C charge rate). There are easy solutions, and you all have already addressed some. Limiting the current between the alternator and battery bank is an easy and complete solution. This can be done by a DC-DC converter or a smart battery isolation manager that limits the time that coach batteries charge. Most of our customers have this issue solved inadvertently simply because the house batteries are located some distance from the alternator, and there is an inherent voltage drop in the line that chokes the current. Some alternators have thermal sensors that regulate the output based on the stator temperature. This is more common in the marine industry, but I suspect it will spill over into the automotive world as well.

Concerning the shore charger/battery scenario. The battery does not normally shutoff during charge. It only prevents a charging current if a cell voltage is abnormally high, in which case the high cell will quickly bleed down. But, under this situation, the BMS will never prevent discharge. if the fridge needs juice from the battery, it will get juice from the battery.

We will need to get the Iota to test it. Thanks for the tip!

 

[oradba69]

Wowww, what a nice thread. Eventually I have a better grasp on these batteries After researching Lifepo4 batteries for a few weeks now.
Thanks a lot for the contributions of the Battle Born gentleman.

 

[dwh]

So an open circuit voltage of 13.4V reflects a full battery. An open circuit voltage of 12.7V is a pretty empty battery.

Okay, so floating the lead-acid off the lithium is a no-go since it will eventually end up taking the lithium down to 0%. 12.7v represents "fully charged" for a lead-acid, but represents "fully drained" for a Battle Born lithium. Looking at the specs for one BlueSea ACR:

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

The disconnect is 12.75v. All wrong.

Concerning the shore charger/battery scenario. The battery does not normally shutoff during charge. It only prevents a charging current if a cell voltage is abnormally high, in which case the high cell will quickly bleed down. But, under this situation, the BMS will never prevent discharge. if the fridge needs juice from the battery, it will get juice from the battery.

Ah. So holding it at an elevated voltage is not going to be prevented by the BMS. Definitely want a shore charger with multi-stage that can drop to a float voltage. Preferably a *low* float voltage.

We will need to get the Iota to test it. Thanks for the tip!

No worries.

Another one, very popular with RV manufacturers (OEMs), is the Progressive Dynamics...who I see now have a charger for lithium (L Model):

http://www.progressivedyn.com/lithium_battery_charger.html


Looking at the manual:

http://www.progressivedyn.com/pdfs/110621A English.pdf

The thing just appears to be a regulated power supply set at 14.6v. Doesn't say anything about float.


The regular PD:

http://www.progressivedyn.com/power_converters_9200.html

Is a multi-stage charger with a goofy charge profile. It bulks to 14.4v (they call that "boost mode"), then drops to a 13.6v float (they call that "normal mode"). So it's basically what the rest of the world would call a two-stage charger. Then they add a twist. After 30 hours in float, it drops the float to a lower voltage - 13.2v (they call that "storage mode"). Then another twist - after 21 hours at the lower 13.2v float, it kicks up to 14.4v for 15 minutes (they call that "equalize").

So it's a compromise designed for RVs that spend most or all of their time hooked up to shore power. It's primary function is as a power supply for the 12v systems in the RV, but thanks to the goofy conservative charge profile, can be hooked up to shore power indefinitely without cooking lead-acid batteries.

However...

It looks to me like the standard PD might actually be a better fit for the Battle Born than the PDL. I wanna know what that PDL does after the lithium battery reaches 14.6v...and naturally, the marketing droids (who obviously long ago staged a coup and took over) at PD don't tell us. Even in the bloody manual, they don't tell us.

I doubt it just shuts down - PD makes power converters to supply the 12v loads in RVs, and they can't very well do that if they just shut down when the battery hits 14.6v.

 

[ScottReb]

I believe BB sells the Progressive Dynamic chargers. I have to second the kudos. So nice to see this level of interaction with a vendor.