Fresh lithium swapped in, but ...

[Frank Dane]

I just swapped in a 100Ah lithium battery for the 80Ah AGM battery that came with our 2-year old Jayco trailer. We have a factory 100-watt Go Power rooftop solar panel and the stock Go Power GP-PWM-30-SQ solar controller.
The system had been working fine (set to AGM), and I haven't paid much attention to the readouts on the controller, other than to see that it usually showed the old battery full to 100 percent capacity by noon or thereabouts on sunny days. During our 14-week trip to Alaska, I know we stressed the old battery a few times by drawing it down further than 50 percent, and after those nights, it took two days to recover to full charge.
I bought the lithium battery to give us a bit more capacity.
I changed the controller setting to LifePO4.
The new battery has been installed for four days now and we've had either full sun or mostly sunny days.
I hoped/expected the battery to reach full charge by now, but it has not.
We haven't used anything electrical in the trailer, it is just sitting in the yard. It does have a carbon monoxide detector and a smoke alarm hard-wired in, so they take current.
The right two of the four bars across the top of the controller readout blink in sequence, but the left two are constantly black/on.
The charge indicator down the left side has shown the three-quarter full icon (bulk or absorption charging, according to the manual) since the moment I hooked up the new battery, and still does.
I haven't yet plugged into shore power, since I wanted to see how the solar would behave, since that's how we mostly camp.
The controller during daylight is showing between 3 and 3.5 Amps, and 13.5 volts consistently.
The third available number (Ah) on the controller has me confused.
I at first assumed this represented the amp hours the solar panel was producing that daily cycle (read that somewhere, now suspect it's wrong).
Late afternoon the first day it showed 25.4Ah. Second day, 20.5Ah, Third day, 22.4Ah.
But the controller instruction manual says the Ah number represents Charged Capacity.
So the new 100Ah battery is only charging up to 20 or 25Ah?
Can anyone educate me on what might be happening?

 

[HueyPilotVN]

I have an idea about what might be happening.

I switched out the charger section of my Convetor/charger to a Lithium rated one.

The first few times it did not fully charge the battery to 100% SOC.

I read the instruction for the WFCO 8955 AD and it says that you have to let the charger go thru a few cycles to learn that it is a Lithium and not a standard battery. It said to fully discharge the lithium battery. I took mine down to about 10%.

After two cycles it was at 100%.

Worth a try.

 

[Gary RV_Wizard]

From what I understand, 13.5v will never bring a LiFePO4 battery to full charge. It takes more like 14.4v. I would think, though, that 13.5v would get it to 75% or so. Hope one of our solar-lithium gurus will chime in on this...

 

[Isaac-1]

You need a amp counting battery monitor to determine LiFePo4 state of charge, you can't rely on volts alone to determine charge level of Lithium batteries as the difference between fully charged and empty is a far narrower span than with lead acid.

The best option is a good shunt style battery monitor, note cheap shunt meters are notoriously inaccurate, good ones will likely cost at least $50, there are also some hall effect charge monitors that work ok in this price range

This is probably the cheapest one I would consider Amazon.com

See SOC charts for LiFePo4 vs lead acid.
This chart illustrates the principle though it is for a 48v battery, 12v will show the same pattern

 

[Frank Dane]

From what I understand, 13.5v will never bring a LiFePO4 battery to full charge. It takes more like 14.4v. I would think, though, that 13.5v would get it to 75% or so. Hope one of our solar-lithium gurus will chime in on this...

Thanks for the reponse. Interesting. GoPower says the panel should output 18 volts. But it's max seems to be 13.5 volts in full, bright, overhead sun. Guess I'll have to think about trashing this panel and finding a different brand that can output at least 14.4 volts.

 

[Frank Dane]

You need a amp counting battery monitor to determine LiFePo4 state of charge, you can't rely on volts alone to determine charge level of Lithium batteries as the difference between fully charged and empty is a far narrower span than with lead acid.

The best option is a good shunt style battery monitor, note cheap shunt meters are notoriously inaccurate, good ones will likely cost at least $50, there are also some hall effect charge monitors that work ok in this price range

This is probably the cheapest one I would consider Amazon.com

See SOC charts for LiFePo4 vs lead acid.
This chart illustrates the principle though it is for a 48v battery, 12v will show the same pattern

Thank you for the information. As a non-electrician, I was hoping for a simple, no-extra-wiring way to moderately upgrade the capacity of a trailer sold as LifePO4-ready. But it sounds like to enable use of a 100Ah lithium battery in my two-year-old RV, I need to basically replace the entire stock system: solar panel, controller, wiring, and add an aftermarket shunt battery monitor, whatever that is. I have a lot of learning ahead of me. From the reading I've been doing in the last couple of days, it sounds like I'll need to tear out inside wall panels to snake in bigger wires. I love having the solar up on the roof, but if all that is required, I may decide to just buy a suitcase solar panel and mess with the hassle of setting it up every day.

 

[Lou Schneider]

Thank you for the information. As a non-electrician, I was hoping for a simple, no-extra-wiring way to moderately upgrade the capacity of a trailer sold as LifePO4-ready. But it sounds like to enable use of a 100Ah lithium battery in my two-year-old RV, I need to basically replace the entire stock system: solar panel, controller, wiring, and add an aftermarket shunt battery monitor, whatever that is. I have a lot of learning ahead of me. From the reading I've been doing in the last couple of days, it sounds like I'll need to tear out inside wall panels to snake in bigger wires. I love having the solar up on the roof, but if all that is required, I may decide to just buy a suitcase solar panel and mess with the hassle of setting it up every day.

It sounds like the trailer is LiFeP04 ready - you have that setting on the solar controller. What you're missing is a way to accurately monitor the battery's actual state of charge. Unlike a lead acid battery where the voltage gradually rises as it gains a charge, a lithium battery holds the system voltage at 13.5-13.6 volts until it gets to about 85% full, only then the voltage will rise during the last 15% of charge.

This makes the Battery Charge Level display in the controller pretty much worthless - it can tell how full a lead acid battery is by looking at it's voltage but a lithium battery's voltage doesn't change unless it's almost all the way full or all the way empty. The amp-hour display only shows how much current the controller is sending towards the battery - it has no way of knowing how much is actually arriving there versus being diverted into powering other loads.

I suspect you have yet to fully charge your lithium battery. If you are putting 100% of the panel's output into the battery (nothing else is on day or night) it will take 10-12 hours of full sun to reach full charge. If you are consuming half of the solar panel's output that time will double, if your average use is more than or equal to the panel's average output you'll never get to full charge.

You don't need to rip out walls, replace wires, etc. Just add the amp-hour counting battery monitor like the one Isaac-1 suggested above. Or the Victron Bluetooth version that mounts directly on the battery and doesn't have any extra wiring going to a display - it shows the parameters on your phone.

 

[HueyPilotVN]

Mine had to go thru two cycles, including a deep discharge for the battery monitor to learn the capacity and then read 100%.

The instructions actually recommended that the battery be discharged to a low SOC before the first connection.

You might try disconnecting it from charging and let it discharge by leaving something on as a load and reconnect after discharge.

Let us know if that works.

 

[Frank Dane]

So today, day five with the new battery, I plugged into shore power. I went into the trailer a minute later and the solar controller was showing Full Charge, 100%, 13.9 volts. Maybe it just needed the jolt from the converter to tell the controller the battery was full? Thank you all for your suggestions and comments. I'm going to look into the Victron Bluetooth version. And fully plan to add maybe 200 more watts of solar at some point in the future.

 

[Isaac-1]

The solar controller is seeing 13.9VDC and interpreting it as being fully charged, this may not be the case, though 13.9VDC should be close to fully charged for LiFePo4 (greater than 97% SOC)

 

[bill dane]

No help, just hello from another Dane