AIMS MPPT draining LIFEPO4...

Lysdexicuss

So the 40amp Renogy Rover MPPT never drained my battery but, now~ with a beefy Aims 80amp MPPT and a brand new LIFEPO4 that i fully charged upon arrival~

There seems to be a massive drain over night without any load.

Question:

if i add a blocking diode between the MPPT and the LIFEPO4, will this stop the drain from occurring ?!

thanx

BB.

Assuming the charge controller (and other components) are working properly, then NO, adding a blocking diode will not fix anything, and will throw confusion into the charge controller and inaccurate charging voltage

If you don't have one, I would suggest purchasing an AC+DC Current Clamp DMM (digital muli-meter). Something like one of these (or others):

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (low cost, "good enough" meter)
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid-priced meter)

You can just clip the current clamp on a wire and see how much current is flowing (and the +/- sign is active in DC mode--Not obvious which direction the current is flowing as just "flipping" the clamp will "flip" the +/- sign.

It would be helpful to know exactly which brand/model of LiFePO4 battery (with BMS or not, etc.). How you know that the battery is being discharged? What is your solar array (number of panels, series/parallel wiring, etc.).

Any other loads (AC Inverter, etc.)?

-Bill

Also with solar charge controllers, always connect the battery bus to controller first, and disconnect the battery bus to controller "last". If you connect solar array first, it can confuse or even damage the charge controller.

-BB

Lysdexicuss

Thanx for the tip on what kind of meter to purchase

yeah the system has been connected in proper sequence, battery 1st controller last

it's a 12v system with six 100 watt panels, a 3500 watt Aims inverter, a Bilt Hard 200 ah lifepo4 battery.

The Renogy Rover 40 amp mppt did a great job but i wanted to expand the array by adding two more panels in series/parallel.

The only change made to this set up was removing the Rover and adding the Aims which is sucking the battery like a vampire to the point where it drops below 10.6 volts.

Are there ANY options to 'fix' this problem other than sending the Aims MPPT back and using another brand ?

BB.

This solar charge controller?:

https://www.aimscorp.net/80-amp-solar-charge-controller-12-24-36-48-vdc-mppt.html

Just to be clear, connect the Charge controller Vbatt  terminals to the Battery Bank first (and battery is somewhere between 10-17 VDC so controller will "configure" for 12 volt bank).

Measure Vpanel input to controller---With the sun up, you should measure around 30-110 VDC--And would be around Vmp-array*0.8 for when everything is operating normally (sun is up, MPPT controller is charging).

More or less, use your volt meter to measure the Vbatt terminal voltage (should be within 0.10 VDC or so of battery bus voltage).

What does you LCD display say (array voltage, array current, battery voltage, battery current)?

Is the AC inverter "ON" for longer periods of time?

Did you connect the Inverter's 12 VDC cables directly to the LiFePO4 battery bank, or to the "LOAD" terminals on the solar charge controller?

Note that a 3,500 Watt inverter can draw a huge amount of current if loaded to 3,500 Watts--For example:

• 3,500 Watts * 1/0.85 AC inverter eff * 1/10.5 volts (loaded/discharged battery bank) = 392 Amps

Or fully discharge your 200 AH battery in about 30 minutes...

I did not find your specific inverter--But it can draw 40-50 Watts @ 12 volt "just turned on" (Tare Current) and zero loads...

48 Watts / 12 volts = 4 amps "Tare current" (guess)... That would discharge your battery in:

• 200 AH / 4 amps = 50 hours (or just over two days if there is no charging from the sun/other charging source)

A 600 Watt array is pretty small for a 3,500 Watt inverter--But if you are careful about your energy usage--It could work. Don't know your location, but a relatively sunny spring day in a sunny location could be 5 hours:

• 600 Watt array * 0.61 DC off grid system eff * 5 hours = 1,830 WH
• 1,830 WH / 12 volt bank = 152 AH of charging in a "sunny" location (typically South West USA).

• The 200 AH battery is rated for 150 AH max discharge (and charge) "Surge?" current...
• 150 Amps * 12 volts * 0.85 AC inverter eff = 1,500 Watt max AC inverter surge current support...

When connecting your AC inverter... It should be connected directly to the battery bus. The LOAD terminals on the solar charge controller are only good for 60 amps maximum (at least my quick search/read).

All of this is to set your "expectations". To better help you debug and understand what you should be seeing. If you can give us some operating voltages and currents (array, battery bus, etc.)... Conditions, Full sun, battery state of charge, etc. 

-Bill

Lysdexicuss

Here's what i can tell you for certain:

i have been an Electrician for over twenty years

All the connections are proper as per your response.

For almost a year everything has been working great with the following:  six 100 watt Renogy solar panels, a 40 amp Renogy Rover Mppt, a 200 ah lifepo4, with an Aims 3500 watt inverter. Properly fused, properly breakered, with four dedicated circuits that are switched on only when needed.

On any given day i can do two loads of laundry, use a 1500 watt cooktop for an hour, and use a big-screen projector to stream movies etc 4-6 hours a night without the battery EVER dropping below 12.4 volts

SO

After switching mppts, now i am lucky if the battery lasts 1.5 hours after dark.

i am not Sherlock Holmes 😹 but it seems obvious who the culprit is.

my only question now really is~ do any of You long-time solar gurus have any ideas how to fix this problem by adding a component (like a blocking diode etc) or should i just return this product and get a Victron or Outback mppt instead ?

i like the build quality of the Aims products and the inverter has done a great job it hardly ever gets hot or runs the fan unless i'm running a window AC unit for several hours during peak Sunshine here in mostly sunny eastern North Carolina.

i shot some video of the Aims mppt during peak solar harvesting maybe i can share a Youtube link here...

thanx 

littleharbor2

If it were me I'd get a quality MPPT charge controller and swap it with the Aims unit. This will likely solve your problem, seeing as it started when you installed it.

BB.

Links and such are fine.

Just to finish hours of sun per day discussion. Winston-Salem NC, fixed south facing array @ 36 tilt:
https://pvwatts.nrel.gov/pvwatts.php

Month	Solar Radiation ( kWh / m2 / day )	AC Energy ( kWh per 1,000 Watt array per month )
January	4.41	82
February	4.50	74
March	5.08	90
April	5.60	93
May	5.49	93
June	5.72	91
July	5.66	92
August	5.41	89
September	5.52	89
October	5.48	96
November	4.66	81
December	3.65	67
Annual	5.10	1,037

It sounds like the charge controller... In the middle of a sunny day, what battery. and array voltage are you seeing when the system is charging? Current values?

Assuming that all is wired correctly, solar panels are producing power, battery connections are correct, and charging voltage is ~14.4 volts set for Li Ion type battery--It does sound like the new charge controller is at fault.

There is nothing you can add to the "charging system" that will fix any problems. If the charge controller is not functioning correctly, it needs to be replaced.

-Bill

Lysdexicuss

Lysdexicuss

The mppt seemed to be doing a great job (before i disconnected it) harvesting energy during peak hours, 2pm-4pm... But after dark, the leeching of power off the battery to the point where i'm not able to use the system effectively is unacceptable. Thanx for all your input Bill~ appreciate your time & energy. 

BB.

Looks good on the display... One of the major design requirements for a Solar Charge Controller is to prevent "back feeding" the solar array with battery energy at night. Typically, at most, the "vampire loads" of a MPPT solar charge controller is 1 to a few Watts at night:

• I=P/V= 2 watts / 12 volts = 0.17 amps (just a rough estimate)

Your controller would have to be consuming multiple amps of current overnight to measurably affect the battery state of charge... For example, say the controller was "consuming" 5 amps over night for 12 hours:

• 5 amps * 12 hours = 60 AH
• 60 AH * 12 volts = 729 Watt*Hours
• 5 amps * 12 volts = 60 Watts

If the controller was consuming that amount of energy, you would probably feel the heat coming off the controller (60 Watt lamp worth of heat).

You could also measure the night time voltage/current going to the solar array... It can happen that you will see 10's of volts on solar array at night from "controller leakage"--But solar cells are actually just "giant diodes". While not terribly good as "blocking diodes", a solar panel at night will draw very little current--So it should not be the "power sink" in this setup.

Some controllers will display array voltage and current at night--Might be interesting to see what your controller displays (since this is all software controlled... It is possible that the software person "zeros" the values at night to avoid phone calls from customers with questions).

-Bill

littleharbor2

If not the controller, can you trace the current with a clamp meter? You should be able to see current coming out of the battery and if it is going somewhere else it should be traceable

ToroPower

Hello from latitude 9.5N.

I have been fighting one of my old systems with an overnight drain.

Six BattleBorn 10012s in series parallel for 24vdc. All Outback FX MPPTs (2) and an Outback FX 2524 inverter/charger.

I have individually recharged/balanced each battery, load test with a coulombmeter and put back in service twice, the second time with new cables for the strings.  The system peaks with over 1500watts on a good day, 28.8vdc at high sun.

The consumption at night is limited to a fridge and a fan or two, maybe 200watts.  Still, the batteries drop to almost LVD before I need to run the generator in the middle of the night.  Voltage drop tests show nothing abnormal.

Strange as it sounds, it's the three batteries in parallel on the POSITIVE side that drop most drastically.

Am I creating a problem by switching off the two FX controllers at night to test the system?

All suggestions are appreciated.

littleharbor2

I would run each string to a set of bus bars as opposed to the method you have now. Good chance it'll work better. all battery to bus cables need to be exactly the same gauge and length.

ToroPower

Thank you for your insight.  I am aware and would like to install and connect bus bars in all my systems here.  However, my 48vdc system with eight BB10012s has been working flawlessly for three years.

The 24vdc system in question WAS working fine for three years. This o-nite drainage just started a few months ago.  I used the BB guide to connect them together (+ and - connected diagonally).  They worked fine, didn't even need the generator.

Inspection of wiring, voltage-drop tests showed nothing apparent.

I am ready to blame the 20yo FX2524 inverter/charger.  But I read this experience with the controller draining the system o-nite and wanted to pursue this diagnosis.

What has me stymied is the fact that it is the positive string dropping off.

So, switching off the two controllers at dusk should not hurt, correct?

 

littleharbor2

ToroPower said:

Thank you for your insight.  I am aware and would like to install and connect bus bars in all my systems here.  However, my 48vdc system with eight BB10012s has been working flawlessly for three years.

The 24vdc system in question WAS working fine for three years. This o-nite drainage just started a few months ago.  I used the BB guide to connect them together (+ and - connected diagonally).  They worked fine, didn't even need the generator.

Inspection of wiring, voltage-drop tests showed nothing apparent.

I am ready to blame the 20yo FX2524 inverter/charger.  But I read this experience with the controller draining the system o-nite and wanted to pursue this diagnosis.

What has me stymied is the fact that it is the positive string dropping off.

So, switching off the two controllers at dusk should not hurt, correct?

 

If you don't have circuit breakers between PV and CC and, CC and Battery then probably best to wait till sun goes away. Look into installing this type of control/protection.

ToroPower

Thanks.  There are breakers.  The subject of isolating the FX controllers is moot (typo corrected. -BB) as it was tried last night to no avail.

Back to a faulty inverter, but I must do my utmost to verify this.

ToroPower

I meant to write "the FX controllers is a "moot" point.  My bad.

Please note administrators, I could not use the edit button and I have yet to receive my confirmation email although I have clicked "resend confirmation" numerous times.

BB.

ToroPower,

I did send you both a PM (private message) and an email. Please let me know if you have received the email or not (and this is the correct email address).

You probably cannot edit your older posts because of the missing email conformation. I can force that, but I wanted to confirm your email address is correct first.

Also, please start your own thread/discussion about your system. That way your questions do not get confused with the original poster's questions.

Take care,
-Bill

ToroPower

Will do Bill.  No worries.

Perhaps I'll start a new thread regarding my overnight BB drain.