Constant 14.6 Volts and no reduced float charge for 12v LiFePO4?

[kjs]

I just got a Progressive Dynamics "PD9145ALV 12V Lithium Ion Battery Converter/Charger - 45 Amp" charger off Amazon. Amazon says "Electronic Current Limiting – Automatically reduces output voltage to prevent overheating and possible damage". But the manual that came with it says "When functioning as a regulated battery charger, the converter has a nominal voltage output of 14.6 VDC ... The system is designed to sense voltage on the battery and will taper charging current as the battery becomes charged."

This sound like it just sits at 14.6 volts all the time which doesn't "feel" right... The Victron solar charge controller I have has default settings of 14.2 Absorption (maybe a little low) but has Float voltage of 13.5V.

My question: Shouldn't the A/C powered charge controller also drop the voltage for 'float' when it is fully charged? If so, does anyone have recommendations of a more suitable 'shore power' LiFePO4 charger?

Thanks!

Kevin

ps- It is for an RV so I will be starting with only one or two 12V 100aH LiFePO4 batteries - either with 'shore power', or initially a 300W panel when boon docking. I just want to make sure they aren't over charging when on shore power.

 

[Steve_S]

That is floating at 3.65 and THAT is NOT GOOD.
If there has to be float, it is usually below the max charge value.
By continually pushing 14.6V, if you have one runner cell that is reaching full at 3.650V while the others are below that, it will continually trip the BMS into HVD.

Basic Inverter and Charge Controller Charge Settings​

Below are the typical settings when using an inverter or charge controller with LiFePO4 batteries.

• LiFePO4 batteries do not require Equalizing / De-Sulphation.
• LiFePO4 batteries do not require Temperature Compensation for voltage.

CHARGE PARAMETERS	12V	24V	48V
Bulk Voltage	14.0 - 14.6	28.0 - 29.2	56.0 - 58.4
Absorption Voltage	14.0 - 14.6	28.0 - 29.2	56.0 - 58.4
Absorption Time	depends on charging profile being used
Float Voltage	13.3 - 13.8	26.6 - 27.6	53.2 - 55.2
equalize(not used) set to lowest time	13.3	26.6	53.2
Low Voltage Cutoff	11.0 - 12.0	22.0 - 24.0	44.0 - 48.0
High Voltage Cutoff	14.6	29.2	58.4
Termination Current *	≤0.05C	≤0.05C	≤0.05C

Termination Current Example: 100AH charge max 0.5C/50A, termination current = 0.05C/5A

* when using multiple batteries in a battery bank, reading current from the bank as a whole is ineffective.

LiFePO4 can be safely charged with either of these modes:

1-stage profile (constant current (CC) aka Bulk Stage) profile will charge the battery ~95%. The 1-stage profile is sufficient, since LiFePO4 batteries do not need to be fully charged, they will settle to 95% after charging.

2-stage profile (constant current, constant voltage (CC-CV) profile aka Bulk and Absorption Stages). The 2-stage profile will charge the battery 100%. This may also have the effect of triggering a BMS HVD (High Voltage Disconnect), therefore take appropriate precautions by using conservative charge settings to begin with.

• Optimal Charging will occur at 0.5C charge rate per battery. The number of batteries multiplies the amps required to meet 0.5C charge rate.
• The ability for any single battery within a bank of batteries should be capable of handling the full charge & discharge potential of the system.

NB: Some BMS' (Battery Management Systems) can interact with Inverters, Chargers & Solar Controllers which can improve overall performance, reliability and longevity of the battery systems. These capabilities are dependent on the equipment being used.

* Equalize: Some Solar Charge Controllers / Chargers / 3-Stage chargers have this. Disable or Set to lowest time allowed and at float voltage equivalent. LFP does not require this.

 

[kjs]

That is floating at 3.65 and THAT is NOT GOOD.
If there has to be float, it is usually below the max charge value.
By continually pushing 14.6V, if you have one runner cell that is reaching full at 3.650V while the others are below that, it will continually trip the BMS into HVD.

Thank you! I bought it based on the Amazon wording but was concerned with the wording in the manual. It looks like Progressive Dynamics have a 9100 and 9200 series that can incorporate a 'Charge Wizard' to drop the voltage (but their max voltage is 13.6 for SLA) but the 9100L (L=Lithium I presume) doesn't support that module and the manual indicates it only tapers the current and not the voltage.

Does anyone recommend a good inverter / charger for LiFePO4? Else I'll return this one and keep googling. Thanks!

 

[kjs]

Rereading the two descriptions again, I wonder if when the manual only says "taper the charging current", it really has to do that by reducing the charging voltage... I may hook it up and let it charge my battery and if it tries to stay at 14.6 V, then I'll return it. Any concerns with a test like that? It's a 45 Amp charger going into a 100Ah battery. It should be floating in < 2 hours right? Thanks again for responses!

 

[Reed Cole]

Pretty sure it will just stay at 14.6 but with minimal current. Battleborn sells those on their website for what it's worth.

 

[mkaye]

i think it has 2 modes, constant current, then constant voltage
when it flips to CV the current will taper off as it reaches full charge of 14.6V - just the nature of LFP
i think this is a good read
https://marinehowto.com/lifepo4-batteries-on-boats/

 

[kjs]

Pretty sure it will just stay at 14.6 but with minimal current. Battleborn sells those on their website for what it's worth.

I was under the impression that we didn't want to hold them at 14.6 after they were charged. Am I incorrect (just with solar for < 1 year and LiFePO4 for < 1 month, so it won't hurt my feelings if you say my assumption was incorrect...

i think it has 2 modes, constant current, then constant voltage
when it flips to CV the current will taper off as it reaches full charge of 14.6V - just the nature of LFP
i think this is a good read
https://marinehowto.com/lifepo4-batteries-on-boats/

That seems to be a great article and I will have to wait to the end of the day to read it. One other question for both of you is whether 45A is too much for a 100Ahr battery. [I think not, but that was my other question.]

Thanks again - great to find this forum!

Kevin

 

[Rocketman]

45 amps for a 100ah battery is .45C. You need to look at your battery spec’s.
I have seen recommendations for charging at .5C And also .2C

 

[Reed Cole]

I was under the impression that we didn't want to hold them at 14.6 after they were charged. Am I incorrect (just with solar for < 1 year and LiFePO4 for < 1 month, so it won't hurt my feelings if you say my assumption was incorrect...


That seems to be a great article and I will have to wait to the end of the day to read it. One other question for both of you is whether 45A is too much for a 100Ahr battery. [I think not, but that was my other question.]

Thanks again - great to find this forum!

Kevin

For what it's worth means take it with a grain of a salt, further investigation is needed.

Battleborns' cells are high quality and closely matched, they test each cell and have thousands to choose from, so they may feel that for them the potential downsides won't result in too many warranty claims.

 

[Reed Cole]

Here is Will interviewing Battleborn CEO, they discuss floating at a high voltage briefly at around 12:50.

 

[kjs]

Here is Will interviewing Battleborn CEO, they discuss floating at a high voltage briefly at around 12:50.

Reed - thank you for this link! Since it was my first LiFePO4, I got an off brand for a little cheaper but will likely buy a Battleborn next time. The ability to ask questions and get answers is well worth another $200 over the course of 10 years...!

Kevin

 

[Sean Steele]

That video sure sounds like Battleborn recommends floating a lifepo battery at 13.4. my converter/charger can do three stage or single stage with adjustable voltage. Now I'm not sure which to go with when my LI battery gets here.

 

[Dzl]

I have only skimmed this discussion so far so feel free yell at me or to throw things at me if I miss the mark or missed some bit of context... buuut no reputable manufacturer or resource that I am aware of recommends a float voltage anywhere near 3.65V (14.6V). Some might state it is allowable for a number of hours or days, but none recommend it. Generally speaking the vast majority of float voltage recommendations I have seen for LFP are (1) float at ≤3.40V (13.6V) or (2) don't use float, stop charging after the first two stages and resume when voltage drops to some level.

edit to add: LFP doesn't need or want 3 stage charging in the same way Lead Acid does. Because LFP does not benefit from being held or kept at a near full state of charge. So 3 stage charging is not necessary or even ideal in some respects, but we can tailor it in a way that makes it work well enough.

The second stage (absorption/CV) is useful (1) to give the BMS extra time for balancing if needed (2) to maximize usable capacity and really get up to 100% SOC (which could be the goal or something to avoid depending on your model). The third stage (float/lower CV) is not needed at all with LFP, but it is convenient in a practical sense in many contexts. There may be other factors I'm not considering, I don't know a ton about charging models.

 

[Annisguy]

I just got a Progressive Dynamics "PD9145ALV 12V Lithium Ion Battery Converter/Charger - 45 Amp" charger off Amazon. Amazon says "Electronic Current Limiting – Automatically reduces output voltage to prevent overheating and possible damage". But the manual that came with it says "When functioning as a regulated battery charger, the converter has a nominal voltage output of 14.6 VDC ... The system is designed to sense voltage on the battery and will taper charging current as the battery becomes charged."

This sound like it just sits at 14.6 volts all the time which doesn't "feel" right... The Victron solar charge controller I have has default settings of 14.2 Absorption (maybe a little low) but has Float voltage of 13.5V.

My question: Shouldn't the A/C powered charge controller also drop the voltage for 'float' when it is fully charged? If so, does anyone have recommendations of a more suitable 'shore power' LiFePO4 charger?

Thanks!

Kevin

ps- It is for an RV so I will be starting with only one or two 12V 100aH LiFePO4 batteries - either with 'shore power', or initially a 300W panel when boon docking. I just want to make sure they aren't over charging when on shore power.

I have had the same dilemma on finding a converter/charger for my motorhome that does not have a nominal charge of 14.6 volts. You mentioned the pd9145alv which is a single voltage charger as are all the progressive dynamics lithium charges with the exception of the 60 amp version which I gather has now been changed to have a float voltage also of I think 13.6. I don’t understand why battleborn still recommends their chargers when they recommend a lower charge voltage of 14.4.
I have a 9245 smart charger, which I decided to leave in place when converting to lifepo4 batteries. As mentioned in an earlier post battleborn batteries and other higher end battery suppliers have matched cells and charging to 14.6 doesn’t seem to be a problem. For the Diy guys, like me, and many others the 280ah Chinese cells are the choice. The problem is the cells tend to drift at the high and low end which causes the bms charging/discharging disconnect to be activated. So, to keep out of the discharge disconnect from the bms, I have set my maximum charge to be 14.2 for my solar and renogy dc to dc converter of the alternator.
I have also ordered an iota dls-75 dual voltage converter/charger that has a rj type plug that you plug in to select either the 13.6 or 14.2 charge voltage. This can also be wired out to a switch to toggle between the two voltages. This converter would normally be off, but would be turned on to get a quick topping up of the batteries from shore power or generator. The iota DLS series also has the IQ4 module which can be added as a module to automatically control charging voltages. Their lithium module uses the 14.6 and 13.6 voltages which is too high for what I wanted, their IQ4 gel model uses 14.2 and 13.6 which is more inline with my preference. I am going to try without the gel module for now.

In summary I think the converter/charger manufacturers need to address the diy lithium users with a more flexible/voltage adjustable model. Solar charges have very flexible settings, why can’t the chargers have the same.

 

[Woody]

I too have concerns with LiFePo4 chargers and went with Battle Born selection for a charge controller. I’m using the following converter/charger from Progressive Dyanmics.

Progressive Dynamics Inteli-Power RV Converter and Battery Charger - Lithium - 12V - 80 Amps
Item # PD9180ALV

I purchased them from etrailer for the reduced price offering they had on them. In my battery design, two 280Ahr cells in parallel with eight of these cell pairs in series to create a 24v battery, I want to do bulk charging but I also wanted to keep a reduced voltage charging profile to extend their life. As such, I wanted a quality bulk charger with voltage output adjustments but did not find one. So I am using two of these Progressive Dynamic converter/charger in series to create a 24v 80A manual bulk charging system.

My concern is about leaving these batteries on float continuously like an UPS or how RV systems are typically implemented because this type of battery chemistry from what I’ve read doesn’t like long term float let alone at that high of voltage for protracted periods of time. There is no external voltage adjustment on these chargers and the charger’s metal case is pop riveted so no easy access to its internals to see if it can be manually adjusted. The solution to reduce the output voltage from these chargers that I will be using was suggested by another forum users and that is to use a diode in line to drop the voltage. This approach works fine for my needs since I’ll be using shore power and the power wasted as heat loss due to the diode drop is acceptable. I’ll be using two high power heat sinked diodes with cooling fans in series to create roughly a 1v drop from these chargers. This is a brute force means to keep the voltage down but it will work. Ideally I should open up the charger and see if they have a variable resistor for voltage adjustment but will not do so until the warranty period is up. I do concur that these vendors should provide a user adjustable voltage adjustment but this vendor doesn’t.

 

[Annisguy]

I too have concerns with LiFePo4 chargers and went with Battle Born selection for a charge controller. I’m using the following converter/charger from Progressive Dyanmics.

Progressive Dynamics Inteli-Power RV Converter and Battery Charger - Lithium - 12V - 80 Amps
Item # PD9180ALV

I purchased them from etrailer for the reduced price offering they had on them. In my battery design, two 280Ahr cells in parallel with eight of these cell pairs in series to create a 24v battery, I want to do bulk charging but I also wanted to keep a reduced voltage charging profile to extend their life. As such, I wanted a quality bulk charger with voltage output adjustments but did not find one. So I am using two of these Progressive Dynamic converter/charger in series to create a 24v 80A manual bulk charging system.

My concern is about leaving these batteries on float continuously like an UPS or how RV systems are typically implemented because this type of battery chemistry from what I’ve read doesn’t like long term float let alone at that high of voltage for protracted periods of time. There is no external voltage adjustment on these chargers and the charger’s metal case is pop riveted so no easy access to its internals to see if it can be manually adjusted. The solution to reduce the output voltage from these chargers that I will be using was suggested by another forum users and that is to use a diode in line to drop the voltage. This approach works fine for my needs since I’ll be using shore power and the power wasted as heat loss due to the diode drop is acceptable. I’ll be using two high power heat sinked diodes with cooling fans in series to create roughly a 1v drop from these chargers. This is a brute force means to keep the voltage down but it will work. Ideally I should open up the charger and see if they have a variable resistor for voltage adjustment but will not do so until the warranty period is up. I do concur that these vendors should provide a user adjustable voltage adjustment but this vendor doesn’t.

How are your 280ah cells performing at the high end, what sort of spread do you have between the lowest and highest cell voltage when approaching full charge. What bms are you using.

 

[Woody]

Q. How are your 280ah cells performing at the high end...?

A. I had the battery bank assembled about a month ago to bulk charge it up. Prior to that I had all the batteries in parallel to balance them off as much as possible after I received them. Initially the batteries were received at 3.295- 3.296v at 0.13-0.14mohms on all of these cells. After pairing the cells and then putting them together to form a 24v battery, I did a bulk charge initially until the BMS noted one cell pack was at 3.7v. Funny because all the cells were taking on a charge really well with only minor variations until one cell pack jumped up to 3.7v. I was charging them with the PD charger at a rate according to the BMS of 80amps. Once I saw the voltage jump, I immediately removed source and cell voltage dropped back down into 3.6xx (don't recall exact value). I then activated the BMS cell balancing feature and let that run for several hours on their own without any power input. The next day I disassembled the 24v battery pack, pulled off the BMS, and put all of the cells in parallel. Then connected them to an 18amp bench power supply and left them slowly charge up over days. Finally reached 3.60v range and I then powered off the power supply, removed the wires from the power supply and have left them in parallel for the few weeks. I haven't checked their voltage in a couple weeks or so. Sorry but the weather warmed up and I had to get the garden ready for planting, along with other pressing issues to take care of, I haven't gotten back to them. Saw the batteries sitting there the other night thought I'd better reconfigure them but car broke down, taxes are due, we had yet another freeze that killed off my tomatoes again, ...life! So I'll have to measure the voltage to see how they are doing but they all should be very well stabilized at the same capacity now.

The BMS that I am using is: https://www.aliexpress.com/item/4000006610664.html

It's the 8SLifepo4 60A with BT

My design is using the BMS as a monitoring control device that is used in conjunction with external solid state relays to activate/de-activate heavy loads like the inverter(s). External bulk charging will only be manually performed via the Progressive Dyanmics chargers if I find the batteries need to be heavily refilled. However, I can also provide charging via the inverters if they are online and connect to the shore power. Bulk charging will be performed externally from the BMS. As for the 60a line from the BMS, it will be connect to low power DC needs and support connections for solar charging input. The plan is to keep the battery available for those times of emergency and when the power goes out. The battery will then be put in service along with the inverter(s) to run things. Solar and/or generator will provide the power to refill the batteries doing these times until the power is restored, well hopefully otherwise I'll be 100% off the gird like many others.

Here's a picture of the cells early on when the battery was configured and under control of the BMS. You see the voltages on the paired cells aren't too poorly spread out.

 

[Annisguy]

Q. How are your 280ah cells performing at the high end...?

A. I had the battery bank assembled about a month ago to bulk charge it up. Prior to that I had all the batteries in parallel to balance them off as much as possible after I received them. Initially the batteries were received at 3.295- 3.296v at 0.13-0.14mohms on all of these cells. After pairing the cells and then putting them together to form a 24v battery, I did a bulk charge initially until the BMS noted one cell pack was at 3.7v. Funny because all the cells were taking on a charge really well with only minor variations until one cell pack jumped up to 3.7v. I was charging them with the PD charger at a rate according to the BMS of 80amps. Once I saw the voltage jump, I immediately removed source and cell voltage dropped back down into 3.6xx (don't recall exact value). I then activated the BMS cell balancing feature and let that run for several hours on their own without any power input. The next day I disassembled the 24v battery pack, pulled off the BMS, and put all of the cells in parallel. Then connected them to an 18amp bench power supply and left them slowly charge up over days. Finally reached 3.60v range and I then powered off the power supply, removed the wires from the power supply and have left them in parallel for the few weeks. I haven't checked their voltage in a couple weeks or so. Sorry but the weather warmed up and I had to get the garden ready for planting, along with other pressing issues to take care of, I haven't gotten back to them. Saw the batteries sitting there the other night thought I'd better reconfigure them but car broke down, taxes are due, we had yet another freeze that killed off my tomatoes again, ...life! So I'll have to measure the voltage to see how they are doing but they all should be very well stabilized at the same capacity now.

The BMS that I am using is: https://www.aliexpress.com/item/4000006610664.html

It's the 8SLifepo4 60A with BT

My design is using the BMS as a monitoring control device that is used in conjunction with external solid state relays to activate/de-activate heavy loads like the inverter(s). External bulk charging will only be manually performed via the Progressive Dyanmics chargers if I find the batteries need to be heavily refilled. However, I can also provide charging via the inverters if they are online and connect to the shore power. Bulk charging will be performed externally from the BMS. As for the 60a line from the BMS, it will be connect to low power DC needs and support connections for solar charging input. The plan is to keep the battery available for those times of emergency and when the power goes out. The battery will then be put in service along with the inverter(s) to run things. Solar and/or generator will provide the power to refill the batteries doing these times until the power is restored, well hopefully otherwise I'll be 100% off the gird like many others.

Here's a picture of the cells early on when the battery was configured and under control of the BMS. You see the voltages on the paired cells aren't too poorly spread out.

I have 2 12 volt strings in parallel and the one 4 cell string has one cell that runs up to 3.65 way faster than the other 3 cells, so my bms shuts down the discharge. Have attached screen shot.
I have contacted my battery supplier.
I did extensive top balancing and my other string of 4 cells is fine.

 

[Bud Martin]

Did you try swapping the cell to see if the problem follows?

 

[grizzzman]

You really think that is an issue? With a delta of 0.074? Drop your voltage to 14 to 14.2 this "may" allow a longer balance time (just a guess as I don't know your BMS adjustment capability)