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Epever MPPT Help

astronajar

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Joined
Aug 22, 2022
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5
Hello everyone. I have the following solar charging system:
312990014_482130287298126_2887240219375148596_n.jpg

- A 200 watts Renogy Solar panels.
- 100 amps 12.8 volts epcom litium LiFePO battery
- A 40 amp Epever MPPT.

312942489_429870632451926_7699532020551077417_n.jpg

The solar panels include their own solar charge controller.

I bought the MPPT because in several videos it was mentioned that they have better performance in charging batteries compared to a solar charge controller.

The problem/question/doubt I have is the following:
- When I charge the battery with the included solar charge controller, it takes an average of 5 hours to charge the full battery.
- Then for test purposes, I used the MPPT twice, following this procedure:
- I configured the MPPT to charge lithium LiFePO batteries
- I fully discharged the battery
- Then I started to charge it with the panels and the MPPT,

The weird thing I found is that, after an hour/hour and a half, the MPPT indicated that the battery was fully charged. It is that possible ?
After that, I disconnected the MPPT and connected the battery to the solar charge controller. Then it took like another 4 hours to charge,
and the solar charge controller indicated that it wasn't fully charged.
BUT, if i do a test with a voltmeter or reconnect the MPPT alone, it sais that the battery is fully charged.

What I am missing/misunderstanding ?
Thank you for your help !
 
It's not clear how you are connecting the MPPT to the panels, I assume the panels in parallel are connected to the MPPT.

The Epever controller SOC reading is very inaccurate and a rough guide only, using this to determine if the battery is 'full' is often incorrect. A similar not very useful indicator of SOC will exist on the PWM controller.

The settings for charge voltage are often set too high resulting in the battery BMS detecting cell over volts and shutting down the charge path.
It's possible your charge controllers aren't charging the battery correctly or the battery has issues.

Your battery holds 100 amp hours, perhaps.

2 off typical 100 watt panels, under solar ideal conditions with a PWM controller, will charge at a maximum of around 11 amps. Thus charge time will be over 9 hours.

The same panels with ideal solar and a 100% efficient MPPT controller charging at 14 volts will charge at 14 amps, thus a minimum charge time of 7 hours.

Since we don't have an ideal world, the charge currents will be lower and solar hours are limited, expect much longer charge times.

Using a resionably accurate voltmeter, not the indicators on the charge controllers, to measure the battery voltage, the following can be assumed;
With the relatively low charge currents, If under charge the voltage exceeds 13.8 volts, the battery is at least 90% charged, typically much higher, if it exceeds 14.0 volts, 99% charged.
At rest, with no charge or load, a voltage of 13.4 +/- 0.5 volts Indicates a full or almost full battery.

What may be causing problems is poor connections between battery and controller, example crocodile clips at the battery. Use a suitable gauge of cable and crimped ring connectors at the battery. Charge voltages are often set too high, 14.2 volts boost, (absorbtion) , 13.4 volts float, are a useful starting point. Sometimes the absorbtion volts needs to be lower if cell inbalance is causing BMS shutdown.

Mike
 
It's not clear how you are connecting the MPPT to the panels, I assume the panels in parallel are connected to the MPPT.

The Epever controller SOC reading is very inaccurate and a rough guide only, using this to determine if the battery is 'full' is often incorrect. A similar not very useful indicator of SOC will exist on the PWM controller.

The settings for charge voltage are often set too high resulting in the battery BMS detecting cell over volts and shutting down the charge path.
It's possible your charge controllers aren't charging the battery correctly or the battery has issues.

Your battery holds 100 amp hours, perhaps.

2 off typical 100 watt panels, under solar ideal conditions with a PWM controller, will charge at a maximum of around 11 amps. Thus charge time will be over 9 hours.

The same panels with ideal solar and a 100% efficient MPPT controller charging at 14 volts will charge at 14 amps, thus a minimum charge time of 7 hours.

Since we don't have an ideal world, the charge currents will be lower and solar hours are limited, expect much longer charge times.

Using a resionably accurate voltmeter, not the indicators on the charge controllers, to measure the battery voltage, the following can be assumed;
With the relatively low charge currents, If under charge the voltage exceeds 13.8 volts, the battery is at least 90% charged, typically much higher, if it exceeds 14.0 volts, 99% charged.
At rest, with no charge or load, a voltage of 13.4 +/- 0.5 volts Indicates a full or almost full battery.

What may be causing problems is poor connections between battery and controller, example crocodile clips at the battery. Use a suitable gauge of cable and crimped ring connectors at the battery. Charge voltages are often set too high, 14.2 volts boost, (absorbtion) , 13.4 volts float, are a useful starting point. Sometimes the absorbtion volts needs to be lower if cell inbalance is causing BMS shutdown.

Mike
Very helpful advice Mike ! Thank you very much !
 
General notes - I have the 100 watt version...

Note the existing supplied controller. It is on a hinge held in place with velcro. It is supposed to be swung out during use. Otherwise the back of the panel can get very hot, and throw off the internal temperature compensation quite a bit (when used for lead-acid.)

Generally, although convenient behind the panel, this is the wrong place to put it. Controllers should be close to the batteries, not the panel. Just in case you ever had thoughts of putting the new controller in place of the old one on the swing-out hinge.

(Warning - if you have never swung it out before, the first separation of the velcro can seem like you are breaking the panel glass. Don't manhandle it.)

Since these panel sets are really meant for those trying to camp and recharge a vehicular battery, they come with some pretty dicy high-resistance clamps. Notice how thin that wire is going to the clamp? It may not matter for those that are just topping off their RV battery, but for more serious use, look into using much better connectors and cut out that small-gauge wire going to the clamp. Anderson's come to mind. There are others. I just found it easier to replace all the wiring.

Doublecheck the cross-panel interconnect cable too for tightness, no stray strands etc.

These small tips may not seem like much, but can help make your folding panel provide it's best.
 
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