Do I update the GO Power Solar Controller to get the LFP Option

[RMLetstryrving]

We purchased a 2018 Pleasure-way Lexor TS.

The Solar configuration:
• 1-CARMANAH (95 watt) - CTI – 95 solar panel
• the Go Power GP-PWM-30-UL (without Bluetooth) Solar Charge Controller
• 2-ECO-ION Lithium 100 AH - Life PO4

The GP-PWM-30-UL (without Bluetooth) Solar controller only has the charging algorithm for 3 battery types and is currently configured for “AGM”.

• Based on the above configuration should I consider upgrading the to GP-PWM-30-UL. with Bluetooth? This would controller does have the “LFP” algorithm for Lithium batteries.
• If I do add 2 additional CARMANAH (95 watt) solar panels should I consider upgrading the to GP-PWM-30-UL. with Bluetooth?
• What is the benefit of switching to the LFP algorithm for charging the batteries?

[markopolo]

The model with the LFP profile has the float voltage at 14V - seems very high to me. Float on the other is 13.7V, still high IMO.


Guess it depends on whether you think float charging LFP batteries is OK or not. For me it's something to avoid and if you can't turn float off then set it to something like 13.2V. If the controller can't be programmed then I wouldn't buy it.

[OregonPerson]

I also have a 2018 Pleasure Way Lexor TS that had the same solar panel and controller. I and other Lexor TS owners have added 2x100 watt Renogy compact solar panels at a much reduced cost over purchasing the original brand of panel. They are a little longer but still will fit on the free space on the roof top.

Your current GoPower 30A controller has an absorption phase charge of 14.4 under the AGM charge profile which is identical to the absorption phase charge under the Lithium charge profile on the updated controller you are considering. Many don't feel it is worth the money having the additional .3 volt (13.7 vs 14) under float. It is suggested that if you want to improve your controller, spend the money on either a better 30A PWM controller than you are considering or switch to a 3OA MPPT solar controller. Personally I would do the latter if you do either one because you will be maxing out the rooftop real estate with the addition of the extra panels and the primary way to increase the efficiency of your solar array will be by switching to a MPPT controller. Make sure you replace the 10A solar fuse with a 30A fuse located on the inside right above the side sliding door when you add the additional panels.

[markopolo]

Float charging, by its traditional definition, is not needed for LFP batteries. There's neither a requirement for it nor a benefit from it. Consequently, the float setting on chargers must be the most confusing parameter to be decided upon with LFP batteries.

We end up trying to use the float setting for either 1. Standby & 2. Storage or both.

Standby is a ready to use state. We know that 13.6V is full or very near full LFP battery. However, there isn't much energy stored between 13.6V & 13.4V. If you need to have a near full battery ready to go then 13.4V as a standby voltage seems to me to be the highest voltage needed.

Storage is different than Standby. Storage is when you are not using the battery. Many Class B vans are not used more days per year than they are used (for RVing purposes). They'll spend more time in storage than in use.

Storing LFP batteries at 50% SOC seems to be the most commonly recommended storage state. The thought is that equally distributing the lithium ions between the negative and positive electrodes is best for long term storage.

On the batteries that I have, 13.164V is the current rested 50% SOC point. 13.160V is the 40% SOC rested voltage. I try to leave the batteries at 13.16V for storage.

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I've mentioned this before - A substantial daily loss can be caused when using the Sure Power 1314-200 Separator with solar and lithium batteries. It's described as being unidirectional and that is somewhat unfortunate in the era of solar and lithium. The part of it that is unidirectional is its voltage sensing trigger circuitry. The unidirectional 1314-200 sees and reacts to the voltage of one battery and the bidirectional 1315-200 sees and reacts to the voltage of either battery. The solenoid part of both the 1314-200 and 1315-200 is either closed or open. When closed, power flows in either direction between the two batteries and when open no power flows. The coil drive current is 1.5A and that is typical for a solenoid.

1.5 amps x 24 hours = 36 amp hours per day used to hold the coil closed. 36 amp hours is approximately the daily harvest you'd expect from a single 100W solar panel on an RV. Eliminate the 36Ah loss and it would be the equivalent of gaining a 100W solar panel.

The 1314-200 needs to see 13.2V (+-2%) at the chassis battery to close. Once closed, it stays closed until the chassis battery voltage drops to 12.8V (+-2%). Lithium batteries are above 12.8V for like 90% of the discharge curve. Power flows in either direction through the solenoid and that keeps the chassis battery above 12.8V until the lithium batteries are nearly depleted or you disconnect the small gauge ground wire on the 1314-200 and let the chassis battery drop below 12.8V (+-2%).

[OregonPerson]

That was very informative Marcopolo, thanks.

[Winston]

Originally Posted by markopolo

Float charging, by its traditional definition, is not needed for LFP batteries . . .

We end up trying to use the float setting for either 1. Standby & 2. Storage or both.

"Float charging", "Standby"??

How about just connecting your charger . . . and we'll call it a Power Supply . . . across your lithium batteries . . . set your Power Supply for a continuous (a/k/a "Constant") 13.4 volts? This is neither "floating" nor "standing by". Let's call it "Normal Operation" mode.

In this "Normal Operation" mode, the lithium batteries are at an SOC of approximately 90%. If you don't want to operate at that high an SOC, dial the Power Supply (charger) back to 13.3 volts.

No current is entering or leaving the Lithium batteries. So we can't call this "charging" or "floating".

And, if you drop a load onto your 12 volt buss? Well, it will be the Power Supply, rather than the lithium batteries, that supply the necessary energy. Why discharge (and have to subsequently recharge) your lithium batteries if you're connected to shore power?

Sure wish we could get away from terms like "Bulk, Absorption & Float" when discussing lithium.

[markopolo]

Re: Normal Operation Charge Voltage, Storage voltage & Standby voltage etc

Winston, I'll use the voltages from discharge tests you previously posted here: https://www.classbforum.com/forums/f...tml#post103586 to help show why I like the additional descriptors.

Those results show that 90% SOC has a rested & resting voltage of 13.36V. So 13.4V will result in a higher SOC than 90%. 13.4V/4 = 3.35VPC - Looking at Powerstream's chart here: https://www.powerstream.com/lithium-...ge-voltage.htm shows that very little charging happens at 13.2V and that you can end up at 99% SOC by charging at 13.4V if left long enough.

13.2V seems to be an effective Storage setting if you've decided to leave a charge source on. Note: that 13.2V is approx 60% SOC on Winston's discharge chart and the same 13.2V only results in a 20% to 31% SOC on Powerstream's charge chart.

13.3V might be a Storage setting option for an unattended RV that has minor loads or minor parasitic losses. The RV might be internet enabled for remote monitoring for an example of a minor load. 65% to 75% SOC maybe?

13.4V is too high to be considered as a Storage voltage and too low & slow as a Operational Charge voltage IMO. Standby better describes that voltage. 13.4V can eventually get the battery to 99% SOC as noted above.

Voltages from say 13.5V to 14.6V would be Operational Charge voltages. I like 14.0V right now.