LiFePo4 settings on Progressive Dynamics Converter

[Jerry Burks]

My camper has a Progresssive Dynamics PD4500 converter/charger and a Renogy Rover 40A solar controller. Right now I am switching from an FLA battery to a LiFePo4 battery.

The battery seller gave me a bunch of voltage values that I can enter into the Renogy solar controller, no problem even if the values are slightly different than the Renogy default Lithium settings. Renogy suggested to go with the battery specifications if available.

But the Progressive converter/charger has only a simple switch between Lead/Acid and LiFePo4 without voltage fine tuning opportunity. They also do not list their actual voltage settings.

Question (not that I have a real choice...) is that a potential problem?

[757driver]

Originally Posted by Jerry Burks

My camper has a Progresssive Dynamics PD4500 converter/charger and a Renogy Rover 40A solar controller. Right now I am switching from an FLA battery to a LiFePo4 battery.

The battery seller gave me a bunch of voltage values that I can enter into the Renogy solar controller, no problem even if the values are slightly different than the Renogy default Lithium settings. Renogy suggested to go with the battery specifications if available.

But the Progressive converter/charger has only a simple switch between Lead/Acid and LiFePo4 without voltage fine tuning opportunity. They also do not list their actual voltage settings.

Question (not that I have a real choice...) is that a potential problem?

It depends on what lithium batteries you are getting. That charger in the LI setting will give a charge voltage of 14.6v and the charge wizard is disabled. They don’t say what happens after the battery bank reaches 14.6v. Does the charger shut off? I sure hope so. When does the charger turn back on?

[Marine359]

Unless I’m confused, charge voltage not the same as battery voltage. My battery charges at 14.6v @80amps. My LiFePo4 battery seldom exceeds 13.8 v, when my bm shows 100%SOC. That’s when charging stops. Nominal battery voltage normally 13.5 - 13.8v

[757driver]

Originally Posted by Marine359

Unless I’m confused, charge voltage not the same as battery voltage. My battery charges at 14.6v @80amps. My LiFePo4 battery seldom exceeds 13.8 v, when my bm shows 100%SOC. That’s when charging stops. Nominal battery voltage normally 13.5 - 13.8v

I would think that the charge voltage you mentioned of 14.6v would be the max. that it would charge to. When your lithium battery bank is showing 13.8v I am sure your charger voltage would be 13.8-13.9v. As with lead acid it does not immediately go to 14.6v when charging lithium but slowly ramps up the voltage. Showing fully charged at a battery voltage of 13.8v is not surprising at all. It may not be at exactly 100% SOC but very close and not necessary to push it the last little bit.

[Jerry Burks]

Originally Posted by 757driver

It depends on what lithium batteries you are getting. That charger in the LI setting will give a charge voltage of 14.6v and the charge wizard is disabled. They don’t say what happens after the battery bank reaches 14.6v. Does the charger shut off? I sure hope so. When does the charger turn back on?

This is a 300Ah CHINS battery with following charge specs. If the Progressive charger really stops at 14.6V I guess I should be O.K. The cells are supposed to be regular prismatic automotive cells.

[Jerry Burks]

O.K. confirmed...Progressive tech support is saying the converter charge voltage is constant 14.6V. Their product does not have any features for boost or float in Lithium mode. And the battery seller is saying the Progressive charger is fine.

Great. But if that is sufficient why do we have boost and float settings for LiFePo4 in the PPMT controllers at all?

[757driver]

Originally Posted by Jerry Burks

O.K. confirmed...Progressive tech support is saying the converter charge voltage is constant 14.6V. Their product does not have any features for boost or float in Lithium mode. And the battery seller is saying the Progressive charger is fine.

Great. But if that is sufficient why do we have boost and float settings for LiFePo4 in the PPMT controllers at all?

As with a lot of information from battery sellers, charge controllers, and battery chargers they don’t really know themselves and are trying to take all the knowledge of lead acid batteries and make it fit with lithium batteries. Lithium is a totally different beast and thus has to looked after differently.

As an example the post above with the spec chart from Chinns says to charge to 14.6v (reasonable if it has balance boards but otherwise that high is not necessary, 14.2-14.4v would be better).

The real killer is the quoted float voltage of 13.8v. After your batteries are fully charged to 14.6v holding them at a float voltage of 13.8v will keep them at 100% SOC indefinitely which for lithium is not good.

Whether a solar charge controller or a stand alone battery charger you should aim to charge your lithium batteries up to 14.xx volts and if it has balance boards hold at that voltage for 15-30 minutes and then stop charging. Otherwise charge to 14.xx volts and stop charging, period. A float charge is something left over from lead acid batteries and is not necessary or required with lithium.

With a solar charge controller recharging will resume the next day when the sun shines. With a stand alone shore power battery charger charging should only resume when the SOC drops to a level set by you (as installed) of about 40% or a voltage of about 12.8-12.9v.

With my solar install it has been months since my inverter/chargers have turned on, solar has looked after everything 12v and even much of my 120v needs.

[Jerry Burks]

Originally Posted by 757driver

.......As an example the post above with the spec chart from Chinns says to charge to 14.6v (reasonable if it has balance boards but otherwise that high is not necessary, 14.2-14.4v would be better). .....

Thanks, this makes a lot of sense. Since the Renogy controller does not have a separate "full charge voltage" number I will set the "Boost" voltage to 14.6V and turn the "Float" voltage off. If I set the "Boost Return" voltage to 13.2V I guess the solar controller will start charging again when the battery drops below 13.2V and then cycle between 13.2 and 14.6V

Still trying to figure out if the Renogy "Low Voltage Disconnect" and "Low Voltage Reconnect" values mean anything (other than maybe for the load terminals on the controller which I do not use). The BMS has its own low voltage protection.

[Itinerant1]

When talking about float or giving recommendations for float or not floating it would help to know if the batteries are being used daily or being stored for period of time. If being used daily and solar is charging/ floating it would be foolish to run off batteries when solar could carry the loads. No reason to unnecessarily cycle the batteries.

[757driver]

Originally Posted by Itinerant1

When talking about float or giving recommendations for float or not floating it would help to know if the batteries are being used daily or being stored for period of time. If being used daily and solar is charging/ floating it would be foolish to run off batteries when solar could carry the loads. No reason to unnecessarily cycle the batteries.

Whether being used daily or in storage I see no need for floating lithium batteries at any voltage. Perhaps a case could be made for a low float voltage of 13.1-13.2v but a float voltage of 13.8v is absolutely absurd.

In terms of cycles I have been operating my system for 3.5years and have put on 250 cycles. With an expected 1500-2000 cycles I have between 21 and 28 years before they drop to 80% of rated capacity so I am not worried about unnecessary cycles. YMMV.

[Itinerant1]

13.8v is absurd, 13.6v or lower why not?

Edit: It's been over 5 years now in fulltime everday boondocking use. Charging to 14.1v or 14.2v depending on season, floating 13.6v with over 1,600+ cycles of partial 35-45% DOD or 550+ combined full cycles. No reason to unnecessarily cycles the batteries when the sun is shining.

[CRV2]

All of the chargers I have seen that are Lifepo4 rated usually charge what is known as CV (constant voltage) at a preset value (some you can adjust) usually around ~14.5v. Think of it like a cruise control resume function, if you batteries are very low, the overall charge voltage will lag behind (lower) than the ~14.5v until the charge current is able to bring the battery voltage up to the set point (~14.5). Once the set voltage is obtained, then the charge circuit will maintain that voltage and constantly drop the charge amperage until another set point in the charger is hit (some are based on time, and some are based on current) (aka as constant voltage or CV).

In regards to floating, that is not really necessary although it does help in certain cases where you want the solar to keep the lifepo4 batteries fully charged for night time usage. In other words if your batteries were fully charged by 1pm (off of solar or other charger) and you turned off the charge and started discharging them, they may not ever get discharged to 13.2v during the afternoon but will not be at 100% when night time hits thereby wasting the solar charge available during the rest of the afternoon.

I personally would not recommend charging lifepo4 batteries to 14.5v (or 14.6v) unless you will be needing 100% of their capacity within a day or so. They will last a lot longer (based on mfgr reports) if you don't charge them to 100% and don't discharge them 100%. In fact, the low voltage cutoff in the BMS (for at least all lifepo4's I have looked at) is there for a safety and it is not recommended to run them down so low as to have the BMS shut off the battery (or charge them so high the BMS shuts off the current). When I don't plan to need the batteries at 100% I usually use the lead acid charge profile which on mine only charges them to about ~14v then I stop charging (depending on which charger I am using I set the float as low as possible). As others have mentioned, some lifepo4 batteries need the higher voltage to balance the batteries, the batteries I have don't require the high voltage to balance them. You should check with the mfgr of your batteries to be for sure. ~Craig

[CRV2]

I wrote that a bit wrong above and past the time I can edit it. I should have stated that the Lifepo4 chargers charge at a constant current (aka CC) first until the voltage hits the set point and then maintains that voltage (aka constant voltage or CV) until either the amperage output falls below a set level or in some chargers a set amount of time has passed. ~CA

[757driver]

Originally Posted by Itinerant1

13.8v is absurd, 13.6v or lower why not?

Edit: It's been over 5 years now in fulltime everday boondocking use. Charging to 14.1v or 14.2v depending on season, floating 13.6v with over 1,600+ cycles of partial 35-45% DOD or 550+ combined full cycles. No reason to unnecessarily cycles the batteries when the sun is shining.

It depends on the use and charge source. For me floating at 13.6v while on shore power would keep the bank at 80-90% SOC. If I am not using the batteries I like to treat it as a storage situation therefore store at about 50% SOC. Floating at 13.6v while boondocking and using solar for the charge source makes perfect sense. If your battery bank is full early afternoon then a float of 13.5-13.6v would be desirable to keep the bank at a higher SOC for the coming night when it will inevitably drop by the next morning.