Swapped in lithium battery, but ...

Vermillion

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Joined
May 4, 2022
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8
Location
TRAVERSE CITY
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 rinsed dust off the solar panel.
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. Today, which has been full sun with zero clouds, 21.3Ah.
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?
 
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Something doesn't look right with the controller, it should be pushing more volts than that, it looks like a float voltage. There should be a bulk mode for the controller.
 
That's what I thought. But today, day five with the new battery, I plugged into shore power and the solar controller instantly flipped to Full Charge. Maybe it just needed a jolt to get on track?
 
That's what I thought. But today, day five with the new battery, I plugged into shore power and the solar controller instantly flipped to Full Charge. Maybe it just needed a jolt to get on track?

Could be, maybe it needed to see some additional load going into the battery. Hopefully it charges now once off of shore power.
 
You really need an ammeter to count amps in and out to get an accurate read on lithium, the benefit of a flat discharge voltage curve is also a detriment to reading how full it is charging. The one on the controller helps but doesn't really show the BATTERY condition, just what the controller has sent to the output, battery AND loads.

Yes, you need more than 13.5v to charge lithium too. That may be a limitation of the charger or the panel. Might help if you could tell us the model, not all controllers are made equal. MPPT do a much better job than PWM. Also, your panel isn't going to produce 100w/8a all day long, it's going to put out 100w when the sun's directly perpendicular to it. If it's laying flat, unless you're at the equator, the sun's below 90 degrees. As it rises and falls in the morning/afternoon it hits at even more of an angle. The more angle, the less power output.

So you've put ~85ah into the battery that was discharged to an unknown level. Exactly how many amps are you pulling overnight from just the CO detector and parasitic loads? subtract that from the charged capacity. IE if you have .5a coming out also, you're losing 12ah per day. The controller sees it going out but not where.

As for reading full when shore power plugs in, presumably that's because your converter is charging at higher voltage than the solar controller.
 
I have the Renogy 200 watts on roof and 30 amp MPPT that charge my battery up most days even with heavy furnace use during the night. So you may need another panel but even more likely an upgrade to MPPT.

I would first contact GoPower and see if they can help you diagnose whats going on. One thing easy to do yourself is check all connections for shiny clean and tight. I had a good battery that looked bad but turned out simply almost invisible corrosion. But as above, you need 14 plus volts at the battery to force the amps into the battery.

I would upgrade to 200 wats and an MPPT.
 

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