DIY 280A Lifepo4 Lithium in 2019 Roadtrek

[larrylwill]

"Another option for your list (just for completeness):
Use the alternator to power a 120VAC inverter. Use its output to power your shore-power charger.
Inefficient, but not completely crazy."

Yes I thought of that, but I only have a 10A charger. Tomorrow I'm going to make some tests and decide if New Potential solution is a decent option. I have a module that I can set the voltage high and low that could turn on/off the relay to short B- and C-.

[booster]

Originally Posted by larrylwill

"Another option for your list (just for completeness):
Use the alternator to power a 120VAC inverter. Use its output to power your shore-power charger.
Inefficient, but not completely crazy."

Yes I thought of that, but I only have a 10A charger. Tomorrow I'm going to make some tests and decide if New Potential solution is a decent option. I have a module that I can set the voltage high and low that could turn on/off the relay to short B- and C-.

Do you have the manufacturer's wiring diagram you could post?


Why only a 10 amp shore charger?

[markopolo]

The RT seems to be one without a Balmar. Probably similar to forum member Yoshimura's RT. Alternator voltage set point at 14.7 volts.

An option is to keep the original setup: UHG to AGM to Inverter for full potential UHG type usage. Insert a lower cost B2B unit like a 60A Renogy between the AGM and the lithium for controlled charging of the lithium. Insert a heavy duty "A/B" switch between the Inverter and the dissimilar (not paralleled) house batteries so you can choose to power the inverter from the AGM (engine running) or from the Lithium (engine not running). Non inverter house loads would be run off the lithium battery. The AGM would only charge when the engine is running but as there's only a 10A charger in the RV I'm guessing that shore power isn't used much anyway.

Shorting B-(cells neg) and C-(neg charge/discharge connection) on the BMS bypasses all of the BMS protections. If the alternator went overvoltage for example then the directly connected lithium cells could be damaged. Similarly, the pulse discharge current out of the directly connected lithium cells in the event of a short for example would be spectacular if not dangerous.

[booster]

Originally Posted by avanti

Balmar regulators are like $300. Probably worth it if you have an independent second alternator.


Another option for your list (just for completeness):
Use the alternator to power a 120VAC inverter. Use its output to power your shore-power charger.
Inefficient, but not completely crazy.

The former is still the most cost effective and would give good results and keep a relatively high charge rate when compared to a big B to B or or through the inverter where a much larger charger would be required to get a good charge rate.


If 40-60 amps of charging is enough get a cheaper small B to B, but at those charge rates, you might as well take out the 280 amp alternator as the stock one on the van could do that much.

[markopolo]

Boosters idea of using a Balmar with the turn down option does look to be the most cost effective. Maybe 1500W or so potential inverter output with that solution so it should be able to run the air conditioner. The lithium would probably have to assist with startup surge. Ideally the voltage hitting the lithium would be less than the 14.7V those RTs had set for the AGM rigs though.

What were the details of the UHG "death spiral" batteries draining - was that with lithium Roadtreks?

Edit: A turned down Balmar is not enough to run the air conditioner and fast charge a deeply discharged 280AH lithium bank simultaneously. Maybe only 300W to 400W left over for charging. We need to know what the UHG was used for and why the switch to lithium was made.

A second 280Ah lithium battery with the same BMS (parallel 280Ah banks, each with 150A BMS) might be a solution depending on what needs are to be met.

[larrylwill]

Originally Posted by booster

Do you have the manufacturer's wiring diagram you could post?


Why only a 10 amp shore charger?

I had 2 AGMs 115A in parallel, I was working in the garage and had the AC on RV plugged in. I went into the house for lunch when I came back the AC was still running but the battery voltage was 8v. I found one of the batteries (the one that came with the RV 2019 was shorted, also the Inverter/charger/ac switch was not working. I pulled it, opened it and could not find any problems, fuses or smelled anything burnt. However I cant get it to come on.

Everything including the batteries fit in the same compartment that the old inverter was.

So I bought a stand alone 2000W sine wave inverter, AC switch (for shore power) and an automatic battery charger 10A. Normally when I park the MH the battery's are fully charged anyway due to driving, so I figured 10 Amps would be more than enough. I also replaced the AGMs with 280Ah of Lifepo4 battery's.

[woodbri]

I have 2016 Roadtrek SS Agile and last spring I pulled out the Ecotrek lithium battery and KS2 electronics, and replaced it with 4 Lion Energy Lithium batteries and Victron components. I also have 280A UHG and solar. I left the 2 6V batteries under the hood in the system because they act as a buffer when the BMS disconnects the Lithium from the UHG. When this happens if the charge load goes from 120-280A to 0A, you generate a HUGH voltage spike, before the balmar can shutdown the generator and this gets dumped into the AGM protecting the UHG and the BMS and other electronics you might have plugged into the system. I found this out because one of my AGM batteries was bad and I was charging the Ecotrek when the ecotrek disconnected and I got a lighting strike in the control panel over the sliding door, which I later found out blew up some capacitors on the tank monitor.

If you have an UHG, I would be surprised that you don't also have a Balmar, and you should reprogram that for the lithium, and adjust the belt load down as suggested above. Also if you don't have an AGM in parallel to your lithium, you can get a spike arrestor or generator protection device to protect destroying your UHG. Like https://www.sterling-power-usa.com/S...iondevice.aspx

Booster is giving you great information.

[larrylwill]

I ordered my 2019 Simplicity with a UHG, Voltstart, Power couch and outdoor shower and had to wait 2 months to get it. I would not be surprised if it doesn't have a Balmar but I don't know where to look. I looked under and around the UHG but did not see one. I do remember it had Echotrek stickers on the kitchen backsplash but only 1 AGM battery. I also found out that the voltstart module was a lithium module and not a AGM one, which when first needed started the engine way too soon. I have ordered a 60A DC to DC charger and plan to hook my lone 115A AGM up to the alternator out and the DC to DC to the Lifepo4 280A battery. I also added 280W of solar some time ago. I hope that will work ok. In the future If I find it necessary I ma add a 2nd 60A DC to DC charger. I doubt Ill have to though.

[markopolo]

That's a safe option for now particularly if some of the wiring is only 4AWG as mentioned in post #9. At full output, a 60A dc-dc unit might need 80A on the input.

[larrylwill]

i have 280 A and the wiring is 2 4 gage in parallel. The main from the alternator is 0 at least.

[Winston]

As per usual, we’re late to this thread . . . but, notwithstanding, we’ll offer a few ‘late’ comments.

We have 500ah of lithium that we charge from three sources, shore power, solar, and a Nations 280amp 2nd alternator controlled, originally, using a Balmar regulator.

A couple of general “philosophical” comments about BMS’s . . . which won’t help you much as you already have one. For us, a BMS has but one purpose - - its our insurance policy should something unexpected happen. We never expect our BMS to intervene, ever. If it does, it means something, elsewhere, has already gone wrong. Thus, our three chargers are all, independently, programmed to ‘do their thing’ - - charge our lithium to a predetermined point, then stop charging. For the BMS to kick-in for ‘over voltage’ means that one of our power supplies (chargers) has failed.

At the other end of the spectrum - - the low voltage end - - we ‘participate’ (monitor) the status of our system and never anticipate allowing it to reach such a low State of Charge that the BMS must intervene. It’s like buying a gallon of milk. We take it from the frig, pour a glass of milk, pour it on our cereal and return it to the top shelf of the frig. Tomorrow, we’ll likely repeat this process. At some point we’ll note - - the milk is getting low, time to buy another gallon. We’re not relying on our frig to report: “Sir, danger, you’re running out of milk.”

We were surprised to learn that you have a BMS that limits the charge (and discharge?) current. You can exceed these current limits on any battery, lithium, AGM, wet lead-acid. Why should we now employ a babysitter to limit these parameters? Our BMS utilizes a rather standard 50mV/500amp shunt. The BMS doesn’t care how much current is flowing - - the biggest consequence of running very high currents - - the BMS’s “meter” may go off-scale. But the BMS won’t otherwise object.

Ok, we’ll get off our BMS soap-box.

Let’s look at charging lithium with a large 2nd alternator with an external (Balmar) regulator. (We no longer use our Balmar as its output stage failed and it no longer provides any field current to the alternator. We’ve kept the Balmar to monitor alternator temperature, but have otherwise built our own regulator).

We were surprised by the huge current slump you have observed (from 280 to 100 amps). Of course charge current slumping is endemic to lead-acid batteries where the battery output voltage varies dramatically between its full and discharged states. But the very flat lithium State of Charge vs Voltage curve makes such slumps far less significant. We’ve never witnessed a slump anywhere close to what you reported. Indeed, we’re wondering if that slump isn’t due to temperature and the fact that the Balmar regular will cut back charging when it reaches 104C.

In fact, we were going to caution you against even trying to charge at 280 amps. We’ve found, for example, that while stationary (not driving/moving), we cannot charge at a continuous rate of more than 75 amperes without overheating the alternator (maybe 100 amps if its really cold outside). When driving, we’ve been able to maintain 150 ampere charge rates without overheating in virtually any temperature. But remember, the heat generated is proportional to the square of current - - so if you jump from 150 amp to a 280 amp charge level, you are increasing the heat that must be dissipated by nearly 4 times.

For us, when the lithium pack is significantly discharged, we’ll start with a 150 ampere charge rate which will decay to, say, 100 amperes.

After researching lithium charge profiles, and modifying the possibilities by the realities of available chargers, we have chosen to use Constant Voltage charging. (We’d prefer a constant current charger, but this requires that the charger output voltage to be continuously increasing as the battery charges - - and, frankly, we’ve never found such a charger.

It seems you’re contemplating getting a “smaller alternator” (which, in our opinion solves nothing), or using the Balmar belt tensioning set back feature . . . or a host of other artificial means (add more resistance between the alternator and battery) to limit charge current. We’d suggest turning your Balmar into a Constant Voltage charger . . . experimenting with “the appropriate” voltage to obtain your maximum charge current when the battery is significantly discharged. We simulated this by setting our Balmar’s Bulk charge duration to 8 hours (of course, we never drive this long so, in short, we set our Balmar to remain in Bulk mode continuously), then adjusting the Bulk charge voltage, again, until we achieve the desired initial charge current.

As an aside, with an external regulator, one doesn’t have to be too concerned with cable size. Based on 200-300 amp possible currents, we spec’d 4x0 cable - - until we actually picked up such a cable. No, we weren’t going to wrestle with 4x0 - - we chose 2x0, instead. And the fact that it has more voltage drop is practically irrelevant . . . as we ran our Balmar ‘voltage sense wire’ from the engine compartment to the rear of the van where our batteries are located. Thus, if the voltage drop increases, the Balmar simply ‘controls’ the alternator to increase its output voltage to compensate for the increased voltage drop.

Hope some of these late comments are helpful.

[larrylwill]

I have found that most BMS's limit the charge to less than the output of the BMS. Mine is 150A but can charge at 150A. Every video I have see the BMS will limit the output current and input current. I can set the amount in the Bluetooth app. I was not aware of one that did not limit the charge and still protect the battery.
I can bypass the input charge by shorting the B- to C- terminal. but then the bms cant stop the charge if its too high for the mosfets. I do NOT have a balmar, my RV didn't come with one.
I have ordered a 60Amp DCtoDC charger so I will use the original 2nd Alternator.

Last night I ran the engine and watched the charge on the app, it started at 280amps and quickly dropped to 150 amps then dropped further to 60A then at last to 0. The battery was not that low. I have not tested it with a really low battery.

[booster]

Originally Posted by larrylwill

I have found that most BMS's limit the charge to less than the output of the BMS. Mine is 150A but can charge at 150A. Every video I have see the BMS will limit the output current and input current. I can set the amount in the Bluetooth app. I was not aware of one that did not limit the charge and still protect the battery.
I can bypass the input charge by shorting the B- to C- terminal. but then the bms cant stop the charge if its too high for the mosfets. I do NOT have a balmar, my RV didn't come with one.
I have ordered a 60Amp DCtoDC charger so I will use the original 2nd Alternator.

Last night I ran the engine and watched the charge on the app, it started at 280amps and quickly dropped to 150 amps then dropped further to 60A then at last to 0. The battery was not that low. I have not tested it with a really low battery.

I don't want to speak for Winston, but I think you missed his point. Your BMS is not regulating the current at all. The 150 amp rating is the max it can pass through without failing,as that appears to be the type it is, passthrough. Winston's BMS reads a high current shunt so doesn't actually see the current going through itself but can read it indirectly. Your BMS failed from overcurrent, which IMO is a very expensive way to limit current and the result is zero current. If it truly limited current it would not have failed, it would have just reduced the current.

[markopolo]

Larry's BMS did exactly what it was programed to do and, in this case, was to prevent its own failure due to overcurrent. The BMS was fine and would resume passing current as soon as overcurrent cause was fixed. The problem here is a 280A rated alternator connected to a 150A rated BMS. You could think of it as a circuit breaker type event protecting a wire or downstream component.

Larry's BMS will also protect against overvoltage. That type of feature would have saved Winston some grief when he discovered his smoking lithium batteries in the rear of his van.

You can see how all these extra safeguards available now can be useful and valuable but you still have to size everything correctly.

[larrylwill]

My BMS shuts down after 10 seconds with the high current then restarts after another 10-20 sec. and keeps doing that. Looking at the app, it says BMS protection ON, current 0 when shut down. I don't know what to tell you. The specs says 160 amp charging, there also is a setting I can use to lower that. Overcharge current protection 160A.
https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1

[larrylwill]

Markopolo: I know exactly how a BMS is supposed to work, like I said it shut down due to the fact that the alternator was putting out 280Amps.
thanks

[booster]

I think Marko describes the BMS well as being a last resort circuit breaker to save itself from destruction as well as the rest of the systm.


I would also be someone who would say that they BMS should not be used as a charge controller, and I doubt that it was it was designed for. How many over current, turn back on, overcurrent turn back on cycles can it it endure? I doubt they publish that data as they figure it shouldn't be an issue or needed.


The process of all of this should be to get charging of appropriate amps and volts until to a point where the batteries are almost full. Most cutoff on voltage, but we have seen at least on newer article the suggests using amps at a voltage to indicate cutoff time. This is just like with lead acid. The BMS shouldn't be involved in any of this.


As was stated earlier in the thread, systems are just that, systems. The parts and parameters need to match each other and play well together. If they don't, the whole thing will never really be what it should be and may be a complete bust.


I think the early Ecotrek systems from Roadtrek showed how bad a hodgepodge system can be.

[larrylwill]

Ok Ill sate it once more. I recognize the problems, that's why I bought a 60A dctodc charger. I had to start somewhere, that was with what I had, before I found out what problems I faced, once realized, I took steps to fix it.

[Winston]

Originally Posted by markopolo

Larry's BMS will also protect against overvoltage. That type of feature would have saved Winston some grief when he discovered his smoking lithium batteries in the rear of his van.

Oh, very good Marko . . . you have a good memory. Indeed, ours is a curious 'case study' in which our "insurance policy", the BMS, malfunctioned at the critical time that it was called upon to make its rare intervention. As you may recall, one of our primary chargers - - the 2nd alternator with the Balmar regulator - - had failed resulting in no charge action. As a temporary fix we wired a fixed resistance into the alternator field winding adjusted to provide a predetermined fixed charge of 50 amperes. This was a temporary manual 'fix' requiring us to closely monitor and terminate charging when full charge was reached. But we got distracted and forgot. This is when the BMS insurance policy should have intervened. But, alas, the BMS was itself defective and did not perform its function. This was an unlikely double failure not really related to the 'over current protection' issue central to the present thread.

Originally Posted by larrylwill

I do NOT have a balmar, my RV didn't come with one.

Larrylwill, we sense a little edginess here and want to apologize. It was not our intention to challenge but to offer a differing perspective based on our five years ‘playing’ with lithium systems and, in particular, our experience with the Balmar regulator. In that regard, we thought you had such a regulator.

It is clear that over the years, differing philosophies of how to implement lithium and its associated BMS technology have evolved and diverged. We have a 500ah pack that is spec’d for a maximum charge of 3C - - 1,500 amperes! As we can never approach this theoretical limit, the thought that a BMS should limit the charge current never crossed our minds. We are happy that our BMS does not perform this function and believe that it is not necessary, nor the role of a BMS, to do so. But we understand your BMS is different. It is what you have. And, most importantly, you are happy with it. So, for us, this is no longer an issue.

Before we, tail under our legs, retreat from this thread, let us inquire about your 2nd alternator, specifically, you say you don’t have a Balmar regulator. The really important question is, do you have an external regulator of any kind? Or is this a more ‘stock’ 2nd alternator having a built-in regulator. The answer to this question changes everything. If you have a non-programmable built-in regulator, then the fact that you have a 2nd alternator is, to us, irrelevant - - you are facing the same issues that you would face with a single alternator of matching a lead-acid based charge profile (alternator/regulator) to a lithium battery. And, if so, your decision to go with a B-to-B converter is quite understandable and logical.

But one of the beauties of a 2nd alternator in a lithium system - - if that 2nd alternator has a programmable external regulator - - is the ability to match that 2nd alternator to the lithium system directly. You can set the 2nd alternator charge current to anything you want - - you are not restrained to the comparatively lesser maximum charge rates allowed by most B-to-B devices.

Peace?

[booster]

Can't say for currently but a few years ago when we were playing with how to increase alternator charging we put in the 250 amp version of DC Power alternator as our only alternator. This basically a slightly small version of the 280 amp version used in most second alternator setups. IIRC correctly it was available with or without a Denso internal regulator. All that Nations does, it appears, on theirs is either put in a regulator or put in two wires to the field if using a remote. I converter the 250 to remote regulator when we got the 280 amp version for a second alternator and we run them in parallel. We can easily charge at over 300 amps for a short time and at 180 amps continuously without overheating the alternators.


The OP probably has the 280 with internal regulator which will run pretty high voltage of about 14.6-14.8v for a while and about 14.3-14.5 later. DC Power used to have a lower voltage regulator available also, I still have one here that ran at about 14.3v and 13.8v, but I don't know if they still have that one available.