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Can a fully programable PWM charge controller safely charge a Lifepo4 Battery?

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featherlite

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Can a fully programable PWM charge controller safely charge a Lifepo4 Battery?

I read an article that appears to say that PWM chargers produce too much ripple to safely charge Lifepo4 batteries.

The subject article appears at
https://nordkyndesign.com/charging-marine-lithium-battery-banks/
and says that

“The worst ripple voltage is produced by solar PWM charge controllers []. In the case of a solar PWM charge controller, the solar array is connected and disconnected from the battery at a fixed frequency. The open-circuit voltage of a solar array charging a battery in a 12VDC installation typically reaches up to about 22V (36-cell panel).
Once the battery can no longer accept enough current to keep the voltage down, every time the controller sends a pulse to the battery, the cell voltages are gradually driven towards 22 / 4 = 5.5V. If the pulse voltage reaches 4.2V, there is sufficient energy for the electrolyte decomposition reaction to take place and the cells get rapidly destroyed, even if the average battery voltage as measured by a multimeter appears acceptable.”
...
“If these [voltages] exceed about 4.20V/cell for the LiFePO4 chemistry, the electrolyte is broken down into gaseous products and pressure starts to build up into the cells.”

I am not asking about the relative advantages and disadvantages of PWM vs. MPPT charge controllers.

I am assuming the charge controller is fully programable so that the charge parameters can be set properly to charge a Lifepo4 battery.

FYI, I currently charge my 12v, 235Ah lead acid batteries with the Bogart SC 2030 charger, the Bogart TM 2030 monitor and (6) 100 Watt solar panels; for my converted cargo trailer.

I am thinking about upgrading to four or eight Eve prismatic cells, with BMS(s) and charging them with my Bogart system.

My apologies if this topic has been covered elsewhere on this forum; however, I searched the forum and found no relevant discussion about this particular issue

I would appreciate your thoughts.



Thank you!
 
I too wonder of this. i have a programmable TriStar PWM controller.
I can program to this suggestion; https://2n1s7w3qw84d2ysnx3ia2bct-wp...Phosphate-LiFePO4-Generic-Charge-Settings.pdf
As this talks about MPPT, I asked the engineers at MorningStar if I could use my PWM for LiFePo. The report back said If I program the PWM to proper settings for my battery, it will be fine.
Please note, this is for MorningStar brand TriStar controller.
 
featherlite said:
Can a fully programable PWM charge controller safely charge a Lifepo4 Battery?

I read an article that appears to say that PWM chargers produce too much ripple to safely charge Lifepo4 batteries.

The subject article appears at
https://nordkyndesign.com/charging-marine-lithium-battery-banks/
and says that

“The worst ripple voltage is produced by solar PWM charge controllers []. In the case of a solar PWM charge controller, the solar array is connected and disconnected from the battery at a fixed frequency. The open-circuit voltage of a solar array charging a battery in a 12VDC installation typically reaches up to about 22V (36-cell panel).
Once the battery can no longer accept enough current to keep the voltage down, every time the controller sends a pulse to the battery, the cell voltages are gradually driven towards 22 / 4 = 5.5V. If the pulse voltage reaches 4.2V, there is sufficient energy for the electrolyte decomposition reaction to take place and the cells get rapidly destroyed, even if the average battery voltage as measured by a multimeter appears acceptable.”
...
“If these [voltages] exceed about 4.20V/cell for the LiFePO4 chemistry, the electrolyte is broken down into gaseous products and pressure starts to build up into the cells.”

I am not asking about the relative advantages and disadvantages of PWM vs. MPPT charge controllers.

I am assuming the charge controller is fully programable so that the charge parameters can be set properly to charge a Lifepo4 battery.

FYI, I currently charge my 12v, 235Ah lead acid batteries with the Bogart SC 2030 charger, the Bogart TM 2030 monitor and (6) 100 Watt solar panels; for my converted cargo trailer.

I am thinking about upgrading to four or eight Eve prismatic cells, with BMS(s) and charging them with my Bogart system.

My apologies if this topic has been covered elsewhere on this forum; however, I searched the forum and found no relevant discussion about this particular issue

I would appreciate your thoughts.



Thank you!
Click to expand...
I first charged my Lifepo4 with the Bogart TM/SC with the WF module. Using a voltage logger I found that for short periods I would see as high as 17 volts. Lithium plating and electrolyte degradation can happen at that voltage. I really like the Bogart system due to its capabilities but decided to move on.
 
Battle Born was fine with a Victron PWM. Though I am trying to return it as it keeps giving me an over voltage alarm.
 
Zil said:
I too wonder of this. i have a programmable TriStar PWM controller.
I can program to this suggestion; https://2n1s7w3qw84d2ysnx3ia2bct-wp...Phosphate-LiFePO4-Generic-Charge-Settings.pdf
As this talks about MPPT, I asked the engineers at MorningStar if I could use my PWM for LiFePo. The report back said If I program the PWM to proper settings for my battery, it will be fine.
Please note, this is for MorningStar brand TriStar controller.
Click to expand...
I have a TriStar 60 set up as a back up SCC for my trailer. I loaded the program info using a PC with the spec's from that PDF. It did not suffer from over-voltage issues that the Bogart system did. My Chargery BMS failed so I decided to go with the ElectroDacus SBMS0 and using the DSSR20's for charging.
 
Bluedog225 said:
Battle Born was fine with a Victron PWM. Though I am trying to return it as it keeps giving me an over voltage alarm.
Click to expand...
Can you explain this a little? I know BattleBorn has said a PWM controller is fine, but seems like you have a PWM sold by BattleBorn and your BMS gives you an over voltage alarm. Both you and @grizzzman

If I’m interpreting that correctly, the PWM does not work well.
 
I got a Victron PWM Pro 12/24-30A. Got it from Battle with their blessing.

Hooked it up to three 100w panels parallel. Kept getting overvoltage alarms from the Victron.

That’s all I I’ve got. I’ve asked for an RMA. Pending.
 
chrisski said:
Can you explain this a little? I know BattleBorn has said a PWM controller is fine, but seems like you have a PWM sold by BattleBorn and your BMS gives you an over voltage alarm. Both you and @grizzzman

If I’m interpreting that correctly, the PWM does not work well.
Click to expand...
Not sure of Bluedogs actual problem. However over voltage seems to be common with PWM CCs when the batteries are full and little load.
My assumption is that the voltage builds up either side of the CC and since there is no actual physical isolation within the circuitry on the negative side (the + on most pwms is common and so directly coupled) the V will gradually build up to the VOC of the panels.

Working on this assumption I fixed my problem by switching on loads at increasing V and having a relay that cuts the pv input at 14.9v as a last defense to prevent the over v of the inverter....it works for me!

Unexplained fires within solar generators may have this issue as one of the possible causes....leaving fully charged batteries connected to a CC, no load, and unattended for long periods.
 
sunshine said:
Not sure of Bluedogs actual problem. However over voltage seems to be common with PWM CCs when the batteries are full and little load.
My assumption is that the voltage builds up either side of the CC and since there is no actual physical isolation within the circuitry on the negative side (the + on most pwms is common and so directly coupled) the V will gradually build up to the VOC of the panels.

Working on this assumption I fixed my problem by switching on loads at increasing V and having a relay that cuts the pv input at 14.9v as a last defense to prevent the over v of the inverter....it works for me!

Unexplained fires within solar generators may have this issue as one of the possible causes....leaving fully charged batteries connected to a CC, no load, and unattended for long periods.
Click to expand...
Pretty new to this forum and in the process of going to LiFePO4 from my FLA Trojan. I have a Schneider C60 PWM charge controller (same as Xanex C60 by the looks of it) and am wondering if I will have any issues assuming I change the (potentiometer) Float/Bulk settings (and disable the automatic monthly equalizing. I'm looking at either 12 V 200 Ah or 300 Ah for my system and the 300 Ah is ~$1000 so don't want to screw things up. I'm a retired EE and in fact had designed/built (about 5 years ago for my small off-grid backup system) my own LV disconnect/reconnect box but recently replaced with the MOES unit (very happy with that setup as my "box" had fixed LV/reconnect voltages as I wanted to have essentially close to a 0% DOD to use battery "forever"). Interested in the circuit you used for the solar disconnect at 14.9v. I'm keeping my old "box" intact but would most likely have all the hunks/pieces in there to build your solar disconnect but will buy new parts, no problem. Could you share your circuit and how implemented? thx
 
Bluedog225 said:
I got a Victron PWM Pro 12/24-30A. Got it from Battle with their blessing.

Hooked it up to three 100w panels parallel. Kept getting overvoltage alarms from the Victron.

That’s all I I’ve got. I’ve asked for an RMA. Pending.
Click to expand...
That is a controller issue if the voltage is going above the voltage set point.

Not a PWM vs MPPT issue.

Voltage is voltage. There is no special metric, analog or Lithium electricity.

While the voltage pulses can be seen on an oscilloscope the voltage at the battery will never rise above the set voltage. Similar to a PWM controller in bulk mode will pass through full panel voltage but the battery voltage does not rise to the panel voltage. Once the set point is reached the current is reduced to continue limiting voltage to the set point.
 
Last edited:
T2R...thx for your reply. My understanding of MPPT vs PWM is the MPPT keeps the panels at their Max power point (as in the name) via a DC-DC converter and thus the voltage to the battery is continuous (as in not pulsed) and at the proper value whereas the PWM has a time averaged voltage and thus when "on" (as in during the on part of the on/off pulse) the voltage will be (at least momentarily) at the panels Voc and maybe the BMS doesn't like this? If the BMS has a large enough capacitor at the input then the average DC voltage should prevail. I did find the link below of use to me as I try to educate myself with changes to my system. I'm a retired satellite systems engineer and know full well how things can go bad with a missed interface spec between two units (and on orbit that's a very serious issue!). Seen it way too many times. Trying to keep my existing PWM CC but will buy a new MPPT with LiFePO4 profile if needed for battery health. Panels are so cheap that I haven't felt the need (nor are my loads excessive) to go the MPPT route yet.

Info - Amptron

www.amptron.com.au www.amptron.com.au
 
SunnySoCal said:
Interested in the circuit you used for the solar disconnect at 14.9v
Click to expand...
FRC3C NC 80 amp relay on the PV- side of PWM cc controlled by XY-CD60 battery protection module ($5 AliExpress), Simple but it works
I did install 2 supercaps at the time and these seem to be a overlooked necessity in any system.

​

 
Last edited:
time2roll said:
While the voltage pulses can be seen on an oscilloscope the voltage at the battery will never rise above the set voltage. Similar to a PWM controller in bulk mode will pass through full panel voltage but the battery voltage does not rise to the panel voltage.
Click to expand...
This does not agree with my observations using multiple PWMs and overpaneling.
I fixed it in my system.
" the battery voltage does not rise to the panel voltage." I still can not exclude this as a possible cause of unexplained fires, along with dendrites, etc, in lithium battery packs specially in the scenario of 'left connected to the panels and with no load' and there is a gradual rise to pv voltage!
 
I emailed Bogart Engineering with a copy of my question posted at the start of this thread and provided them with a link to this thread. Below is the reply from Bogart:

[Bogart reply:] All well built LFP battery packs have internal electronics to limit battery voltage and charge or discharge currents. The upper voltage limit is usually set in the range 14.6 to 14.8V. If an external charger attempts to impose a higher voltage, this [BMS] circuit will isolate the battery immediately.

In addition, it is very difficult to increase the voltage of a battery pack to very high levels without increasing the charging current. As long as the batteries are being bulk charged at 30% or less (of nameplate capacity), an external source (charger or solar panel) can't spike the voltage to very high levels.

Solar panels are a peculiar kind of energy source. They can't simultaneously hold the voltage at the highest levels & deliver high currents. This is the reason solar panel specifications mention open circuit voltage (zero Amps) and short circuit current (zero voltage).

The maximum power point voltage & current are usually 10-15% lower.

Several customers use our SC-2030/TM-2030 to charge lithium batteries. We have two systems in our lab that have been running flawlessly for over 3 years.

Make sure that the panels' Voc is not more than 21V and the total current does not exceed 35 Amps.

As long as the monitor & controller are in good working condition, the voltage will be regulated to programmed levels.
[end of Bogart Reply]

Does anybody disagree with Bogart's reply or care to comment?
 
I agree with Bogart. I also suggest charging to less than the absolute max voltage and having a relatively short absorption period before regulated voltage is dropped to float. This should be simple in a fully programmable controller. I have and recommend Morningstar brand controller. Although Bogart controller combined with the Bogart monitor would seem to be an excellent set up.
 
I’d like to understand why they don’t recommend the panels Voc to be over 21V. Aren’t they admitting that there is a risk of over voltage with their controller with this very statement?

EDIT: I see that they were referring to their 2030 unit. I understand the concern now.

This seems like a pretty limited controller for the $. You can buy a nice MPPT for not much more that gives you the flexibility to connect your panels in series.
 
Last edited:
When I first purchased the SC2030 the Manuel stated 60 amps but would clip anything over 31 amps. Then later it was revised to 45 amps. And now there stating 35 amps? Before I over paneled, I e-mailed Ralph ( The engineer/owner then) He said I was OK over-paneling at 640 watts as long as ambient temps stayed below 120 F. The FET de-soldered and I corrected that (thought that the heat-sink coming loose was the cause.) I ran that unit for 5 years without issues that way (with FLA) so my guess is that the LFP bank stays in bulk longer causing more heat then absorb pushed it over the top. moral of the story, keep it below 35 amps!
 
RVLiFe said:
I’d like to understand why they don’t recommend the panels Voc to be over 21V. Aren’t they admitting that there is a risk of over voltage with their controller with this very statement?

EDIT: I see that they were referring to their 2030 unit. I understand the concern now.

This seems like a pretty limited controller for the $. You can buy a nice MPPT for not much more that gives you the flexibility to connect your panels in series.
Click to expand...
We recommended a panel Voc of 21V since the SC-2030 is a PWM type controller; going up in voltage does not result in higher charging currents.

Max input voltage of the SC-2030 is 55V.

There are other aspects to battery charging than the common PWM or MPPT question. For example, our controller (when used with the TM-2030) in the only one in the market that lets you terminate charging based on the Amp-hrs returned to the batteries. The charging process (as is the discharging) is an electrochemical reaction, with electrons being one of the reactants/by products. In order to fully reverse the chemical reaction & completely convert all lead sulfate into lead or lead oxide, it is essential measure the charging Amp-hrs. It is even possible to specify X % excess charge to account for less than unity Coulombic efficiency of the reactions.
 
grizzzman said:
When I first purchased the SC2030 the Manuel stated 60 amps but would clip anything over 31 amps. Then later it was revised to 45 amps. And now there stating 35 amps? Before I over paneled, I e-mailed Ralph ( The engineer/owner then) He said I was OK over-paneling at 640 watts as long as ambient temps stayed below 120 F. The FET de-soldered and I corrected that (thought that the heat-sink coming loose was the cause.) I ran that unit for 5 years without issues that way (with FLA) so my guess is that the LFP bank stays in bulk longer causing more heat then absorb pushed it over the top. moral of the story, keep it below 35 amps!
Click to expand...
The maximum current the SC-2030 can tolerate is still 45 Amps. However, we have noticed that many customers do not install the controller the way we specify. For example, some customers install it in cramped spaces, without air space below, above & the sides to promote natural air circulation. Or, install them in locations where the ambient temperature can exceed 120 F (in summers). Under these conditions, it is important to de-rate the controller's specifications.
 
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