Question on charging LiFePO4 to 90% SOC with a charger in an RV

robwolff3

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Backgound​

I purchased a new Airstream that came with:
  • 2 lead acid batteries
  • WFCO WF-8955LiS-J-WAGO charger / power distribution panel that is compatible with lithium batteries
  • Progressive Dynamics PD1610J 1,000w inverter
My plan is to upgrade the batteries to LiFePO4 by making a 12v battery with (4) 3v 280Ah cells and a BMS as an example. I as I understand it, the life of the battery can be extended by charging no more than 90% capacity and depleting no lower then 10% capacity. This would require a custom charging profile with specific voltages in accordance to the batteries capacity which I don't believe the WFCO can do. I would also like a storage charging profile of 50% SOC when not using the battery for weeks or months at a time.

Currently when not using our trailer we plug it in to shore power. If we're not going to use the trailer for weeks I would trigger the storage charging profile and trigger the 90% SOC profile a couple days before we leave for a trip.

I am using a Victron BMV now to gather data Ah usage on right sizing the battery I will eventually make. I plan on staying in the Victron family with a Victron solar charger down the road and possibly for my question below. Also to note, I don't plan on using an inverter my RV came with hardly if ever with the way we boondock. Everything we use on the trailer is 12v, appliances, lights, charging phones, etc.

My Question​

Two ideas I had to get two custom charging profiles. I'm not what the best solution here is and would appreciate feedback:
  • Put a Victron DC-to-DC in between the WFCO and the battery to get custom charging profiles. What I'm not sure on is if the Victron will allow electricity to flow in reverse to the WFCO distribution panel and to 12v appliances when the trailer is not plugged in to shore power.
  • Replace the converter / charger in the WFCO with a Victron charger? I'm trying to figure out if Victron would have a compatible drop in replacement that would work with a distribution panel but I'm not sure. Could it power the power 12v appliances in addition charging the battery when were plugged into shore power? Maybe the Blue Smart IP22 charger or the Phoenix Smart IP43 Charger?
Before recommending a Victron charger/inverter, I already have an inverter and don't plan on using it hardly at all so I don't think that's the best budget friendly route to go.

Attached is the lithium charging profile from the WFCO WF-8955LiS-J-WAGO.
 

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time2roll

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14.6 volts will generally trip a DIY LFP battery BMS every time for cell or battery over voltage. I don't recommend this converter or any other "lithium" converter. Especially for charging to 90%. Even a standard WFCO at 14.4 volts is better.
 

camelCase

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I have a WFCO 8900 series unit in my camper. I have never seen it put out more than 13.7 volts. To get it to go up to 14.4 volts you have to have a big enough load on it to pull the voltage below 13.2 volts in order for it's algorithm to go into boost mode. Under normal usage, that doesn't happen in my experience. 13.7 volts is 3.425 per cell, so you'll likely never get a full charge anyway.
 

robwolff3

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This is the charging profile of the WFCO 8955LiS when in lead acid mode. I am just worried about cutting off charging to the battery when it gets to 90% SOC.
 

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wholybee

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Short answer, get a different charger.
Longer answer, a charger with a custom setting will allow you to set the bulk voltage lower, to what will be about 90%, which is probably about 13.6V. You would then set absorb or float to something lower than that (maybe 12.8) so charging will stop.

As things work, that won't precisely give you a charge to 90%, but get you in the area and thus accomplish your goal.
 

wholybee

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I have a WFCO 8900 series unit in my camper. I have never seen it put out more than 13.7 volts. To get it to go up to 14.4 volts you have to have a big enough load on it to pull the voltage below 13.2 volts in order for it's algorithm to go into boost mode. Under normal usage, that doesn't happen in my experience. 13.7 volts is 3.425 per cell, so you'll likely never get a full charge anyway.
Full charge is ~3.4V per cell. Charging at a higher voltage will get you to a full charge a little bit faster, but after you stop charging and let the battery rest for 24 hours, it will settle to 3.4V. If you charge at 3.4V, you will fully charge the battery, but as you get close to 3.4V per cell the charge rate will slow down and it will take longer.
 

robwolff3

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Based on your replies and refining my searches of the forums here it looks like the best solution is to swap out the charger in my WFCO with a Victron Blue Smart IP22 charger 30A. Looks like it will charge the batteries with the charging profiles I desire as well as power the 12v appliances in my trailer when were plugged into shore power. Thank you all for your input!
 

rickst29

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The WFCO 8900 consists of 3 'sections'. The Battery connection is into the DC distribution board (upper right), and the WFCO output (from the Converter Board in the "bottom section" is also connected there. The uopper left is the AC circuit breakers and power distribution, not really an issue here.

If you want to interrupt the battery connection with a new (and one-way) DC->DC charger, you will need to pull a second "load" wire from the battery +12v terminal(s) to the DC distribution board. If you like, that "load wire" can be switched - allowing you to shut off all 12v "phantom loads" while the Airstream is in storage. That shutoff also prevents the WFCO Converter Board from reaching the LFP batteries directly. Without that shutoff, the "load wire" is actually bidirectional, and WFCO can still charge the battery.

But, as camelCase has correctly pointed out - the WFCO chargers tend to fall into "float mode" very quickly. The resulting charge current (at only 13.7 Volts) will push the battery to more than 95% full, but it will take considerable time to do that. The difference between 95% full (WFCO native "float mode") and 90% full (13.6V desired "float mode") is awfully small, and IMO not worth the trouble and expense of wiring in a DC->DC charger.

The big issue with the WFCO is: #1, with 'Lithium profile' it charges way too hard, continuously, while #2 with 'FLA' mode it wants to perform "Anti-Sulfation" Equalize cycles every couple of weeks, at extreme high voltage which WILL kill the LFP batteries. But there is a pretty good solution for you: Simply set your DIP switches to specify that you've got 'AGM' batteries. That drops the Boost Voltage AND prevents the Equalize cycles, with nearly perfect results.

I feel that the hassle and cost of installing the separate DC->DC charger, along with needing to remember the shut-off switch whenever you put it into storage, aren't worth the very slight benefit of a lower float charge voltage.
 

HRTKD

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In the short term, you could set your BMS to have a max voltage of 14.2v, or whatever you're comfortable with. It's not an ideal situation as we generally recommend limiting the charge with the charger, not the BMS. The BMS should be your last line of defense, not your first.

Replacing the non-programmable converter with a programmable converter is the right way to go. I have a non-programmable IOTA Engineering converter in my RV trailer. It does have a LiFePO4 charge profile. The converter is rarely used because I'm boondocking 95% or more of the time and I rarely need to use my generator. When I do use my generator it's for short periods of time to run the microwave. My PV system satisfies my charging needs.

If I happened to be in a situation where I was stuck on shore power for more than a day, I would probably flip the circuit breaker that the converter is on. Problem solved.
 

RF_Burns

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I'm a bit late the to the party here, but just wanted to share what I have.

I have two 100Ahr LFP batteries, a Samlex EVO-1200 charger/inverter/transfer switch and a Victron MPPT solar charge controller. The Samlex unit is programmable for battery chemistry, charge current, target voltage, absorption time limit and exit current and lots of other parameters. It even Logs status onto an SD card if desired.
The Victron MPPT SCC is wired to the EVO's external charger input terminals. The EVO measures the current from the external charge source and subtracts that from the current it is delivering. So I have the EVO set to 40Amps and if the SCC is delivering 5amps, then the EVO will add 35 amps to keep the charge current at 40Amps.
I used a lot of Samlex stuff during my 40 years in 2-way radio communications systems and very rarely had any issues with their equipment. They seem to have a charger only unit with similar features on their European site, but not in North America.
Just my experience, your mileage may vary.
 

Geokilroy

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I'm a bit late the to the party here, but just wanted to share what I have.

I have two 100Ahr LFP batteries, a Samlex EVO-1200 charger/inverter/transfer switch and a Victron MPPT solar charge controller. The Samlex unit is programmable for battery chemistry, charge current, target voltage, absorption time limit and exit current and lots of other parameters. It even Logs status onto an SD card if desired.
The Victron MPPT SCC is wired to the EVO's external charger input terminals. The EVO measures the current from the external charge source and subtracts that from the current it is delivering. So I have the EVO set to 40Amps and if the SCC is delivering 5amps, then the EVO will add 35 amps to keep the charge current at 40Amps.
I used a lot of Samlex stuff during my 40 years in 2-way radio communications systems and very rarely had any issues with their equipment. They seem to have a charger only unit with similar features on their European site, but not in North America.
Just my experience, your mileage may vary.
Your WFCO WF-8955LiS has a switch option to change between LiFePo batteries and the others. That is what the"S" at the end designates. Hook up that switch and change between profiles easily. Your switch can be mounted remotely to make it easy. Check to see if their profiles will fit your requirements. Also for long storage, I put a disconnect at the batteries to make it easy for me to shut everything down and not damage my batteries over the months of down time.
 

chrisski

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I have not found a plug into 120 volt charger that I would leave my battery hooked to 24/7/365.

I charge my Lithiums at 13.8. That is 3.45 per cell. All standard switches are higher than that. Some are 14.4.

I have found RV chargers that are voltage configurable, but they would also float at that voltage. I want to float at less.

The main charging takes place with the SCC. Only if my batteries get low because of cloudy weather will I turn my charger on.
 

RF_Burns

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Is there a RV charger/converter that is programmable? Most solar charge controllers are programmable but shore line RV chargers seem to be fixed in their settings. That's likely a good thing for people who don't care about the details... keeps them out of trouble and saves customer service calls.
There are charger/inverters that have programmable settings, but there must be a RV converter/charger only out there that fits the bill!
 

HRTKD

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Is there a RV charger/converter that is programmable? Most solar charge controllers are programmable but shore line RV chargers seem to be fixed in their settings. That's likely a good thing for people who don't care about the details... keeps them out of trouble and saves customer service calls.
There are charger/inverters that have programmable settings, but there must be a RV converter/charger only out there that fits the bill!

I haven't seen one that I'm impressed with. For that reason, when it came time to replace my inverter, I went with an inverter/charger that is programmable. I'll ditch the existing AC-DC converter, which, while it does have a LiFePO4 charge profile, isn't programmable.
 

time2roll

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Is there a RV charger/converter that is programmable? Most solar charge controllers are programmable but shore line RV chargers seem to be fixed in their settings. That's likely a good thing for people who don't care about the details... keeps them out of trouble and saves customer service calls.
There are charger/inverters that have programmable settings, but there must be a RV converter/charger only out there that fits the bill!
Powermax Boondocker has an adjustable converter but I think you are stuck with a fixed voltage if the adjustment is used.
Some talk about opening converters and finding the correct pot to adjust.

Mostly mine is charged with solar so I plan to tolerate the WFCO converter for emergency use only. I did buy a battery voltage controlled relay to cut or connect power to the converter based on battery voltage. Might install if it gets to be an issue.

https://www.mpja.com/Battery-Low-Voltage-Disconnect-Board-20A/productinfo/36621+MI/
 

chrisski

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I haven't seen one that I'm impressed with. For that reason, when it came time to replace my inverter, I went with an inverter/charger that is programmable. I'll ditch the existing AC-DC converter, which, while it does have a LiFePO4 charge profile, isn't programmable.
I spent so much time and energy finding the Aims AC to DC converter which I will only turn on if batteries need charged like several cloudy days, that I forget about what seems like a much better solution of an inverter/charger or an all in one.

One of those if I did my build over things.
 

Cdkipp

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I spent so much time and energy finding the Aims AC to DC converter which I will only turn on if batteries need charged like several cloudy days, that I forget about what seems like a much better solution of an inverter/charger or an all in one.

One of those if I did my build over things.
Yes I still have questions about how the all in ones are going to hold up with rv travel. They are lighter and cheaper. The Victron and Magnum hybrid converter/chargers are beasts and hard to beat. Magnum is a bit more of a beast but Victron has all the pretty bells and whistles. IMO
 

HRTKD

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Yes I still have questions about how the all in ones are going to hold up with rv travel. They are lighter and cheaper. The Victron and Magnum hybrid converter/chargers are beasts and hard to beat. Magnum is a bit more of a beast but Victron has all the pretty bells and whistles. IMO

Converters and circuit boards last for years in RV's. A securely fastened device should as well. Then again, some trailers ride better than others.
 

RF_Burns

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Here is a charger that is programmable and can handle 3 different batteries at once each one can be a different chemistry and have a different profile. Its available in different current and voltage ratings.


Its from Samlex Europe and does not seem to be marketed here in North American.
 

eXodus

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I have not found a plug into 120 volt charger that I would leave my battery hooked to 24/7/365.

I charge my Lithiums at 13.8. That is 3.45 per cell.
I got an old Parallax Powercenter Converter - it floats 45A at 13.6V

It's always at that voltage. No float, not bulk, no intelligence whatsoever. Constant voltage power supply. Perfect for killing FLA early and AGMs slow. But actually decent to maintain lithium at around 90%.

What I connect it all year round? Probably not - but I'm only pluggin into campgrounds once in a while.
 
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