Going Lithium-Iron Phosphate

[rvsprinterguy]

I'm switching from a single 100-Ah AGM house battery to two 100-Ah Lithium batteries and would like advice regarding a replacement Converter/Charger.

I'm looking at the Progressive Dynamics PD9160ALV 12V Lithium Ion Battery Converter/Charger - 60 Amp on Amazon.

Is this a good choice, or are there better options?

Thanks in advance!

[rowiebowie]

Your pocket book will smart for a while, but you'll smile when you realize you have over 3x'd your usable power.

I suggest a combined Inverter/Charger of at least 2000 watts. Also, add a DC to DC charger between your chassis battery and new lithium coach batteries plus a battery monitor. I went with all Renogy setup, but there are other more & less costly options.

Make sure all components have a charging profile for lithium batteries (including solar controller if you also have roof panels) and that you draw no more than 40 amps from your engine alternator when charging while driving.

[hbn7hj]

The converter you chose will work. You have two problems yet to solve: Dealing with lithium temperature issues and charging from the alternator. Get the charge mode pendant if you don’t have ready access to the button within the power panel.

If the lithiums are in the living space that problem is solved. You will need a DC to DC charger if you want power from the alternator. Alternator direct to a lithium battery doesn’t work well.

I kept the original battery, did away with the need for the DC to DC charger but added complexity.

[markopolo]

Your money might be better spent on a DC-DC charger than a new converter because you might be able to run the output of your existing converter (depending on what you have) through a DC-DC charger that has a better lithium charging profile. Output from the alternator could possibly be run through the same DC-DC charger provided that the alternator also remains connected to the chassis battery.

I mostly use a standard 3-stage PD converter as the power source to charge my lithium batteries. The output of the PD converter runs through my DIY DC-DC charger so I have full control over both voltage and current. It doesn't matter what stage the PD converter is in as the boost/buck DC-DC charger controls what the lithium battery actually gets.

[rvsprinterguy]

Originally Posted by hbn7hj

The converter you chose will work. You have two problems yet to solve: Dealing with lithium temperature issues and charging from the alternator. Get the charge mode pendant if you don’t have ready access to the button within the power panel.

If the lithiums are in the living space that problem is solved. You will need a DC to DC charger if you want power from the alternator. Alternator direct to a lithium battery doesn’t work well.

I kept the original battery, did away with the need for the DC to DC charger but added complexity.

My two new batteries will go in what was a storage compartment on the floor next to the existing converter. I had intended to remove the AGM house battery, but am intrigued by the possibility of keeping it to avoid adding a DC to DC charger. I'd like to know more about how you accomplished this.

[rvsprinterguy]

Originally Posted by rowiebowie

I suggest a combined Inverter/Charger of at least 2000 watts. Also, add a DC to DC charger between your chassis battery and new lithium coach batteries plus a battery monitor. I went with all Renogy setup, but there are other more & less costly options.

Next step is putting together a schematic to understand what additional components are needed and where they'll go.

[rvsprinterguy]

Originally Posted by markopolo

Your money might be better spent on a DC-DC charger than a new converter because you might be able to run the output of your existing converter (depending on what you have) through a DC-DC charger that has a better lithium charging profile. Output from the alternator could possibly be run through the same DC-DC charger provided that the alternator also remains connected to the chassis battery.

I mostly use a standard 3-stage PD converter as the power source to charge my lithium batteries. The output of the PD converter runs through my DIY DC-DC charger so I have full control over both voltage and current. It doesn't matter what stage the PD converter is in as the boost/buck DC-DC charger controls what the lithium battery actually gets.

Good to know. I'll be using a COTS DC-DC charger. There appear to be multiple places where power to it can be tapped.

[hbn7hj]

Originally Posted by rvsprinterguy

My two new batteries will go in what was a storage compartment on the floor next to the existing converter. I had intended to remove the AGM house battery, but am intrigued by the possibility of keeping it to avoid adding a DC to DC charger. I'd like to know more about how you accomplished this.

Booster and I put this together several years ago. It works very well.
I took his ideas and adapted them to my use. You can change things to suit your use.

AGM for the furnace, lithium for the entertainment systems. Lithium charges the AGM without noise.

https://www.classbforum.com/forums/f...stem-8526.html

The generator is used to charge the lithiums. At 60 amps generator runs are very short. No converter change necessary but a dedicated lithium charger is used. You need two battery monitors.

[rvsprinterguy]

Originally Posted by hbn7hj

Booster and I put this together several years ago. It works very well.
I took his ideas and adapted them to my use. You can change things to suit your use.

AGM for the furnace, lithium for the entertainment systems. Lithium charges the AGM without noise.

https://www.classbforum.com/forums/f...stem-8526.html

The generator is used to charge the lithiums. At 60 amps generator runs are very short. No converter change necessary but a dedicated lithium charger is used. You need two battery monitors.

Thanks for the link. That's a very interesting thread.

[hbn7hj]

Originally Posted by rvsprinterguy

Thanks for the link. That's a very interesting thread.

The link continues to get views but I don’t know anyone that has used it to build a system. Someone must have a link to it on his website.

[@Michael]

I built a combined LiFePo4/AGM setup.



This diagram is greatly simplified. I have a few more A/B switches so I can flip the solar panels between battery banks, use the LiFePo4 to top off the AGM, etc.

A few more details are in this post.

One of my constraints was that I wanted to be able to remove the LiFePo4 battery and still have a functional coach, mainly to allow me to store the camper in extreme cold weather. If I were starting over from scratch, I'd remove that constraint and make it simpler.

[jakegw2]

You do not need a DC-to-DC charger.

It is true that the alternator will not provide optimal charge parameters for LiFEPO4 batteries but as long as you have some power source that can top them off (and rebalance the cells) occasionally they will be pretty happy charging off the alternator.

For large LiFEPO4 banks the alternator can be overstressed from having its maximum output demanded for long periods of time when charging them from a low charge state. In my opinion this is not a significant issue for only 200Ah.

So my advice would be to get a converter that has a LiFEPO4 charging profile and don't worry about the DC-to-DC charger. Not only will you simplify your installation you will get higher charge rates from the alternator that will fill your battery with less run time.

Finally I presume you are buying a battery with a built-in BMS that protects against all the common failure modes (overcurrent, overvoltage, undervoltage, high temp, low temp, etc). In this case you should realize that even without any LiFEPO4 optimized charging source your batteries will work just fine. You will experience a shorter lifespan then you would with a better charging setup, but it will still likely be on the order of 5+ years rather than the 10+ that you could get with a better setup.

LiFEPO4 prices have been dropping rapidly and I would not be surprised if you would have much better options from a performance and cost perspective in 5 years that might prompt you to upgrade anyway. I purchased my LiFEPO4 batteries about 1.5 years ago and there are now significantly better options on the market then when I bought. So much so that I am contemplating replacing them to take advantage of the improvements, despite the sunk-cost of my current (perfectly well performing) batteries.

Bottom line - changing your charger is a perfectly adequate upgrade to support your new LiFEPO4 batteries without any other changes.

[rvsprinterguy]

Originally Posted by @Michael

I built a combined LiFePo4/AGM setup.

One of my constraints was that I wanted to be able to remove the LiFePo4 battery and still have a functional coach, mainly to allow me to store the camper in extreme cold weather. If I were starting over from scratch, I'd remove that constraint and make it simpler.

Thanks for the diagram. We're not subject to extreme cold weather, and I'm willing to run a small space heater if necessary. So, I'll probably remove the AGM house battery in the interest of weight savings.

[rvsprinterguy]

Originally Posted by jakegw2

You do not need a DC-to-DC charger.

It is true that the alternator will not provide optimal charge parameters for LiFEPO4 batteries but as long as you have some power source that can top them off (and rebalance the cells) occasionally they will be pretty happy charging off the alternator.

For large LiFEPO4 banks the alternator can be overstressed from having its maximum output demanded for long periods of time when charging them from a low charge state. In my opinion this is not a significant issue for only 200Ah.

So my advice would be to get a converter that has a LiFEPO4 charging profile and don't worry about the DC-to-DC charger. Not only will you simplify your installation you will get higher charge rates from the alternator that will fill your battery with less run time.

Finally I presume you are buying a battery with a built-in BMS that protects against all the common failure modes (overcurrent, overvoltage, undervoltage, high temp, low temp, etc). In this case you should realize that even without any LiFEPO4 optimized charging source your batteries will work just fine. You will experience a shorter lifespan then you would with a better charging setup, but it will still likely be on the order of 5+ years rather than the 10+ that you could get with a better setup.

LiFEPO4 prices have been dropping rapidly and I would not be surprised if you would have much better options from a performance and cost perspective in 5 years that might prompt you to upgrade anyway. I purchased my LiFEPO4 batteries about 1.5 years ago and there are now significantly better options on the market then when I bought. So much so that I am contemplating replacing them to take advantage of the improvements, despite the sunk-cost of my current (perfectly well performing) batteries.

Bottom line - changing your charger is a perfectly adequate upgrade to support your new LiFEPO4 batteries without any other changes.

All good to know. Yes, the batteries I'm buying have built-in BMS. And the charger is Li-specific.

[avanti]

Originally Posted by jakegw2

You do not need a DC-to-DC charger.

It is true that the alternator will not provide optimal charge parameters for LiFEPO4 batteries but as long as you have some power source that can top them off (and rebalance the cells) occasionally they will be pretty happy charging off the alternator.

I think it is safe to say that this is a minority opinion, to say the least.

There are combinations of vehicles and batteries that might let one get away without a current-limiting device between the chassis and a lithium battery, but it is certainly not considered good practice.

Judging from his username, OP is driving a Sprinter. For many years now, the MB upfitters' guide has explicitly required charging currents for all external batteries to be limited to 40A. Lots of people (especially owners of older Sprinters) ignore this, but no reputable upfitter would do so. Moreover, modern vehicles almost all have so-called "smart" electrical systems, in which the voltage is modulated by an ECU to optimize charging of the chassis battery. In such a system, you will see significant fluctuations of voltage coming from the alternator. That is why buck/boost B2B setups are so common these days.

[hbn7hj]

Always good when the creative folks around here wake up!

[booster]

I think one thing that hasn't been mentioned and is often lost in the how to details is what the original premise of doing the combination setup of AGM and lithium.


When it was first put out as a "what if" type thing the idea was to create a fairly large reserve capacity and reduce the charging time by a bunch. It was mostly tailored as something that would allow boondocking folks with generators, or big alternators, to get fully charged with much less generator or van running time. This is because of the long charge times that AGM batteries take to get full (6-8 hours of charging).


As imagined, you would have a larger AGM bank than lithium so costs would be reduced compared to pure lithium, plus you could just remove the smaller lithium and use the van on AGM in the cold weather. Early guess you would have 3-4 times as much AGM capacity as lithium.


Cycle would be something like run the generator charging both banks at the same until the lithium is full and the AGMs probably at about 70% or so. Which would be 30 minutes to a couple hours depending on bank sizes. You would then let the lithium pick up the lower rate charging of the AGM bank during the much slower, low amp, finishing charging of the AGM. Overnight when use is low would be a good time for the quiet charging by lithium. In the morning, AGM will be full or near full and the lithium in need of charge. Another short generator to fill the lithium and you have two full banks.


Such a system could increase capacity at reduced cost to all lithium, eliminate cold temp issues, greatly reduce generator run time to charge AGM batteries.


The devil, as always is in the details, but it has been shown to be doable. Variations of the theme, of course, to suit individual needs and taste would/are certainly warranted.

[RossWilliams]

Originally Posted by jakegw2

Bottom line - changing your charger is a perfectly adequate upgrade to support your new LiFEPO4 batteries without any other changes.

I think you are seeing the difference between optimum solutions - which may be both expensive and complicated - and a likely acceptable simple solution that is neither. Preferred solutions on this forum are usually of the complicated, optimum variety.

You might also ask yourself how sure you are you will even still be using this RV in ten years. By that point you may be able to power your RV from your toad's electric battery.

A LONG time ago, Bill Gates was asked why he wasn't using the newest Pentium computer and his response was enlightening. He said his current computer met the need for his current uses and in 6 months there would be an even faster computer available. You should only buy when you need the technology, because you will have to accept less to get it now than you will have if you wait 6 months. No matter what you do now, there will be a better solution at less cost available in the near future.

[markopolo]

Originally Posted by rvsprinterguy

Good to know. I'll be using a COTS DC-DC charger. There appear to be multiple places where power to it can be tapped.

Do you have a link to the Cots unit?

[honeyboy]

Four years ago I installed 2-100 AH Battleborn batteries in my 2001 Roadtrek with no DC to DC charger. I was worried about frying the alternator too. The tech folks at Battleborn assured me this was not a problem. They appear to be correct. I’ve had no issues with the alternator. I did do a permanent install of a PD 30 amp lithium charger which is able to top off the batteries at 14.6v. I was told to plug it in once per month to top off and balance the lithiums. I also have a 180 w Grape solar panel on the roof to help keep them charged. I almost never use the batteries past 60-70%. I’m not sure how well the alternator would fare if I solely depended on it to bring the 200 ah batteries back from 10%.
This is my real life experience with 2-100 AH Battleborns. Your mileage may vary……