Going to lithium, converter question....

[Spower]

I have decided to go with 2 100ah battle born lithium batteries in the very near future.
My current converter is a progressive 60A, PD4560K18NS2B.
It has a "mode" button on it that i am told i will have to push when I want to charge the lithium batteries. If so then what does the controller do while boondocking? I have a renogy 40A mppt rover controller that supports lithium batteries.
Can somebody explain this to me in English i will understand?

I can go with a new converter that i dont need to push a button for charging, but I want to understand what I wrote above.
Also how the new converter will work as well while boondocking.
Stay with old converter and push button or go with new?
TIA!!

 

[sduser]

Not familiar with that product, but this post has some info:

Battle Born Lithium Iron Phosphate Batteries charging - Jayco RV Owners Forum

Below is a copy of an email string I sent to Progressive Dynamics, maker of my Jayco Eagles battery charger. I hope you all find this useful. Charger: PD4560K18NS2B Subject Lithium iron phosphate

www.jaycoowners.com

 

[Spower]

Thank you for that!! So then the converter only charges when I am plugged in, right? And my solar/controller do the charging when not plugged in, right?
If I am correct then I don't really see a need to change the converter, I am a full timer and boondock most of the time.

If I was to be stationary for a few moths then I would just push the button a few times a month to charge them up?

 

[MisterSandals]

So then the converter only charges when I am plugged in, right? And my solar/controller do the charging when not plugged in, right?

I suspect that your PD converter is "probably" powered by your RV's engine alternator which would charge when the engine is running. This is what my RV does with a PD4645 (10 year old, pre-lithium aware converter).

The solar charger is probably completely independent of your PD converter setup so it probably is ready to charge whenever the panels send enough power to the Rover.

 

[MisterSandals]

What I discovered with my PD converter was that its charge profile, set for lead acid batteries, is far better than the newer lithium compatible replacement. I forget the numbers exactly but my existing converter charges to around 13.4v which mostly charges my LiFePO4 battery bank (8 206ah cells in 2P4S arrangement, 12v).
The new PD replacement that is lithium compatible, charges really high and is not configurable. It charges to 14.6v or something WAAAAY over where i like to charge (13.8v, very conservatively because i have a big battery bank and can get by with charging to "less than 100%").

So long story short, I am using my old PD4645 to charge my LiFePO4 bank with a lead acid charge profile.
Most of my charging is by solar and I am rarely plugged in so not much of an issue other than when driving. I keep an eye on the charging while driving and plugged in. Suboptimal but I cannot see a better solution at the moment (swapping converters is NOT easy and PD is the only maker of a wire-for-wire replacement).

So, I recommend for your PD converter, research the charge profile and evaluate for yourself (or ask this forum when you get the numbers) whether this is how YOU want to charge YOUR batteries.

 

[snoobler]

Thank you for that!! So then the converter only charges when I am plugged in, right? And my solar/controller do the charging when not plugged in, right?
If I am correct then I don't really see a need to change the converter, I am a full timer and boondock most of the time.

If I was to be stationary for a few moths then I would just push the button a few times a month to charge them up?

This is a constant voltage 13.6V unit. This is an optimal float voltage for LFP, and it will charge your BB to 95% SoC, though it can take 5-6 hours.

IMHO, the only times you should use boost are 1) if you really need to charge the battery quickly, or 2) you're charging from a generator, and you don't want to run it for 5-6 hours.

 

[Spower]

Ok so what i am reading here is that unless I want a fast charge (while plugged in) I don't need to push the button, I can just leave it, right?

BTW my rig is a TT not a MH.

 

[snoobler]

Ok so what i am reading here is that unless I want a fast charge (while plugged in) I don't need to push the button, I can just leave it, right?

BTW my rig is a TT not a MH.

That is my opinion, and that is what I would do. I have confirmed with individual cell charging test that 3.4V/cell (13.6V float) will charge these to 95% capacity (not BB specific, but LFP in general). 13.6V is the maximum allowed float voltage for BB batteries.

 

[Spower]

Quote from above....13.6V is the maximum allowed float voltage for BB batteries

Then why do they sell the new converter that charges constantly over 14v?

 

[snoobler]

Float is the constant voltage applied to a battery to maintain its charge.

Bulk or Absorption voltage is the charging voltage to achieve full charge in a timely yet safe manner.

Normal lead-acid charging is:

Bulk: max current until absorption voltage reached (14.4-14.6V typical)
Absorption: Taper current to keep voltage at the 14.4-14.6 typical level while battery "absorbs" the top 10-20% of its capacity
Float: Once battery is fully charged, supply just enough current to hold the battery at the float voltage, 13.6V in this case.

Lead-acid must be stored at 100% when possible and the float achieves this.

LFP follows a very similar convention except LFP doesn't NEED a float phase. They hold their charge fine. Float is useful with LFP when combined with solar. When the SCC is holding a float voltage, if loads are applied to the system, the SCC supplies the needed power in an effort to maintain the float voltage.

 

[Spower]

That makes sense, thank you! I am learning so much!!

 

[MisterSandals]

Then why do they sell the new converter that charges constantly over 14v?

I wouldn't use the term "charges constantly" because of the different stages outlined by snoobler (that almost got posted with autocorrect to: "snubber") above.

But why do the have a lithium charge profile that charges to 14.4-14.6v (using snubbers numbers)?
I dunno. I would love to hear the answer. I would love to see a configurable charge profile.

 

[snoobler]

14.6V is the way you get LFP charged fast. At 0.5C, the battery will likely be at 90% SoC when it hits that number. Once that's hit, I think they just cut off or have a VERY brief absorption phase.

The biggest issue I see is that at 14.6V and 50A-ish current may result in a notable voltage drop. My TT has the converter and batteries in the same compartment - no biggie. My MH has the converter on the back wall of the aft storage compartment and the battery bank about 20' away. This means the converter "sees" 14.6V way before the battery gets there and terminates charging.

A fairly common profile of RV converters is:

14.4-14.6V "bulk" with negligible current taper at that level (1-4 hours typical)
13.6-13.8V "absorption" (8-14 hours typical)
13.2V "float"

IMHO, the above profile is likely better suited to LFP batteries than what I've seen of the "dedicated" LFP chargers.

 

[carbon RV pilot]

manually putting your converter into boost mode [pushing the charge wizard button] will force it to charge at 14.4 +/- at 60 amps for about 2hrs or until fully charged and is only charging at around a 0.3c rate but still somewhat quick and from what ive read safe aswell if you let it charge BB's on its own at 13.6v [not boost] it will just take a bit longer! nit sure about long term though, that converter is a "smart" converter so i would think it would stop charging when full but that im not sure about... but the BB's on-board bms would prevent overcharging! buying a "lithium" charger would clearly be better but i think you should be able to safely use that converter

 

[Spower]

Thanks for all the great replies and helping me understand all this!!

I will stay with my current converter. Most of my camping entails no hookups until I hunker down for the winters then I am plugged in. But as mentioned, the BB batteries have BMS, so I should be fine then as well.

 

[phfkef]

Lithium batteries require 14.6 volts to reach full charge. If you can't provide that you will never reach full charge and most likely about 70 to 80% max. They also can not be charged when below freezing without damage. Some have built in heaters (obviously parasitic) to allow this.

 

[John Frum]

Lithium batteries require 14.6 volts to reach full charge. If you can't provide that you will never reach full charge and most likely about 70 to 80% max. They also can not be charged when below freezing without damage. Some have built in heaters (obviously parasitic) to allow this.

You can fill a battery pretty much full with 3.4 volts per cell which is 13.6 volts for a 4s battery.
14.6 volts just gets it full faster.
The problem with charging at 14.6 volts is when the battery is not perfectly top balanced one or more cells can exceed 3.65 volts and incur damage.
Most batteries are not perfectly balanced.

 

[snoobler]

Lithium batteries require 14.6 volts to reach full charge. (1) If you can't provide that you will never reach full charge and most likely about 70 to 80% max. (2) They also can not be charged when below freezing without damage. Some have built in heaters (obviously parasitic) to allow this.

(1) absolutely, positively untrue. I have personally attained 95% SoC at 13.6V.
(2) true.

 

[phfkef]

(1) absolutely, positively untrue. I have personally attained 95% SoC at 13.6V.
(2) true.

If so then this is very interesting from Progressive Dynamics;

"Can I Use My Present Progressive Dynamics PD9200, PD4000 or PD4500 Series Lead/Acid Units With the Charge Wizard to Charge My Lithium Battery?​

Yes, if you are willing to live with an expensive battery that is only partially charged. The Normal Output voltage of the PD9200, PD4000 and PD4500 Series voltage provides only 13.6-volts and a full charge voltage for Lithium needs to be 14.4 – 14.6 Volts. The PD9200, PD4000 & PD4500 Series Charge Wizard will initially jump to 14.4-volts in the Boost Mode when first connected to 120 VAC power and will remain there until the battery voltage reaches 13.8-Volts, then automatically drops down to the Normal Mode of 13.6-Volts. The faster charge rate of Lithium means that in the Boost Mode it will reach this 13.8-Volt point after only a few minutes of recharging and then the charging current will drop to ZERO AMPS and will not add any additional charge to your Lithium Battery. This lower charge state will not damage your battery, but will eliminate most of the advantages you paid for."

 

[snoobler]

The majority of LFP charging occurs below 13.6V.

PD has a motivation to sell new converters.

I have a motivation to enable informed choices.

I have personally charged a single cell to 95% capacity @ 3.4V. It started at 0.33C.

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