Discharge-Problem with Epever 3210A Charge Controller

Solalar

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Oct 25, 2018
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Hey there,

i've just signed up to this board (but read a lot before in here). I'm living in central Gemany without any energy form the grid. Since 9 month my 220Wp solar panel charging a stack of 3s60p 18650 batterys without any issues. Yesterday, after drawing a lot of energy (while rain falls), i have to notice, that the voltage drops under 10V. Thus, i've disconneted the load. Today, the voltage drops down to 8.7 Volt without any load :s According to my powermeter on the charge controller, there was no energy pushed in the batteries, although the sun was shining. I've decided to disconect the battery from the system.

I'm using a Epever 3210A (30A) Solar Charge Controller. The 3s60p was builded of 1200-2500mA 18650 batterys and is balanced via BMS. I've entered the following battery settings to the charge controller:

Over voltage disconnect: 12.6V
Overvoltage reconnect: 12.5V


Equalization charge: 12.5v (equalization time set to 0 minutes)
Float charge: 12.5V
Boost reconnect 11.4V (Boost reconnect duration set to 120 minutes)

Charging limit: 12.5V
Discharge limit: 9.6V

Low voltage disconnect: 9.8v
Low voltage reconnect: 10.2v

Under volt reconnect: 9.8v
Under volt warning: 10.0v


That worked good for me in the summertime. But after a few rainy days and drawing a lot of energy, the stated issues appear. I'm confused about the low disconnect voltage at 9.8V. I thought, the charge controller will disconnect the load, untill the solar panels charged the battery up above 10.2V? But the controller didn't charged the batterys at all, although there was visible sunlight on the panels (perhaps 50W) and the displayed voltage was 35V,but no current (0A, 0.02W) flew into the battery. And is the charge controller drawing that much energy in the standby-state, so that the voltage drops down to 8.7V?

If there is any direct sunlight on the panels tomorrow, i'm going to hook up the system again, after checking all connections/fuses. But do you have some suggestions for solving this problem?

In the meantime i've a cozy candlelight evening :rolleyes:

Thanks!
Klaus
 
An analoguecenter zero DC ammeter in series with your battery will answer your question.
 
You're asking a lot from standard lithium cells to deliver 12v. I'm sure you've read quite a few threads on the topic as it's been discussed many times, and even included in the FAQ

Aside from that, what Sean says seems viable. Center zero means the meter needle will be straight up when no current is flowing. This will show you current flowing to/from the batteries.
If you don't one of those, you could use a DC motor. It will turn one direction when power is flowing into the batteries, and turn the other way when discharging. You just won't know by how much.
But I would first recommend checking all your connections (especially since temps have changed) and nuts/bolts can come loose over time due to heating/cooling of the metal. Check all fuses and even check "inside" the charger to make sure there aren't any internal fuses that have blown.
 
Hey, thanks for the quick replies! I'll measure the battery current with my multimeter (20A fused, should be fine at a rainy day with a 220Wp panel) or a shunt/DSO tomorrow - and check all connections. But i assume, the charge controller is not configured properly. After disconnecting the load at <9.8V, the self-conumption of the controller (<20mA at 12V according to datasheet) just can't cut down the voltage to 8,7V in approx 17 hours...
But let us see tomorrow ;-)
 
When I was charging my 3s battery pack with solar, I notice the 13.0volt bulk setting on my mppt controller was too low. ( that was the lowest it would go, I was aiming for 12.6 volts). At 13 volts bulk it was charging at 5 amps even though my 240 watt panel was capable of putting out 12 amps.

When I raised the bulk setting to 14.4 volts, the charging amps went up to 15 amps. But when you raise the bulk voltage you no longer can control that the battery won't get overcharged, you need to be confident your BMS will shutoff when battery is full. In the winter especially you need to adjust your bulk voltage, otherwise you will be slow charging all the time.

I been using an overvoltage relay to disconnect the solar panel when the battery voltage reaches the appropriate setting that I set. I can set bulk voltage to whatever I want, its always higher then recommended due to I like to fast charge my batteries when on solar. Also like other people recommended, get a 90 volt 30 amp combometer, connect between controller and battery. The combo meter has large LED that shows you volts/amps going into the battery. With your 220 watt panel you should be getting at least 11 amps of charge power.


My setup. The 6 dollar relay is the brains in the system. It monitors battery voltage, if it goes too high it disconnects the panel, no more charging.

image_oeimel.jpg


combo meter . you can find on ebay for about 20 dollars

image_fgqicg.jpg
 
Thanks jonyjoe for sharing your setup. But I can't belive, that a modern MPPT charge controller need to be set to a higher voltage, to force a higher chargeing current through the batteries. Sounds strange to me, but i'll test it at the next sunlight - thanks ;-)

Furthermore I clamped a ampmeter between battery an charge controller this morning: 170mA flew into the charge controller (self-consumption, i guess). After disconnecting the RS485-to-Wifi-Adapter, the consumption droped to 110mA. Despite the overcasted sky, there should be at least 20W powered by the solar panel. The controller (and android-app) displayed 35V solar-voltage, 0A, 0.25W...

I've checked all fuses, connections and the PCB of the charge conroller (for hidden fuses and faulty components) - but everything should be fine...
So my next steps are
1) rising the charging-voltage (like jonyjoe)
2) Check the controller with a lead-acid-battery

Do you have some more suggestions? ;-)


Edit: I found this repair instruction in another thread. There are fuses on the controllers PCB, i have not seen. I'll check this out first ;-)
 
you dont want to hear my suggestion :) But this is proper way to do it

1. Get a charge controller that will work properly with lithium and you can set proper voltages
2. Do not use the BMS as charge controller for disable/enable charege. The BMS is a protection
3. Go to 24V system instead since 12V on Lithium based on nominal of 3.7V do create issues.

Disabling solar input based on voltage on the battery is 1 sollution but you will never be able to fully charge the pack since it will disconnect directly when voltage is reached (CV) and never go into constant current state (CC)

And as said many cheap controllers draw power from the battery. Especially those with Load ouput. Get one you can disable that on or just run as a charge controller and the charger will almost drop to 0 in idle mode.
 
daromer said:
1. Get a charge controller that will work properly with lithium and you can set proper voltages
2. Do not use the BMS as charge controller for disable/enable charege. The BMS is a protection
3. Go to 24V system instead since 12V on Lithium based on nominal of 3.7V do create issues.

Thanks daromer,

1) Jeah, my charge controller should be fully programable... should..
2) I'm using the BMS just for balancing
3) Jep, this is my goal in the near future. The 12V battery is just for testing. Meanwhile i'm harvesting 18650 for a proper 24V powerwall ;-) A diy-thread will follow! :cool:
 
I don't think there is a true solar controller that does lithium (except the electrodacus controllers) they all monitor overall voltage and if the lithium is out of balance that can be bad. I wouldn't waste spending extra money on a controller that is "lithium" capable. Theonly one I tried, I set it for 12.6 volts max voltage, and it went over 12.6 volts. I don't trust any controller to charge lithiums on there own. A controller that you can adjust the bulk voltage is best the controller to own, sometimes you might have voltage drop from the controller to the battery, you need to account for that. The controller can read 12.6 volts, but if you measure the voltage at the battery terminals it might read 12.2 volts, to compensate you need to raise the bulk voltage .4 volts. Thats just an example of why adjustable bulk voltage is needed.

As far as balancing, the BMS has very low capability to balance in the 60 milliamp range, if you try and fast charge the battery at high amps, it will always trigger the BMS to shutoff charging early. No matter how good you build your battery pack, it will always drift out of balance when fast charging, even a small amount is enough to shutoff the charging.

This is a picture of my lifepo4 with active balancers ( can be used on any lithium battery), they can balance at up to 10 amps per cell, the active balancers will keep up with high amp charging. These keep my battery overall voltage always in balance. Highly recommend these balancers when you like to fast charge your batteries.

image_ridbuq.jpg
 
Those balance can ONLY reach max current when the voltage difference is HIGH. What I have tested it need to be more than 1.5V between max and min cells. If you see that you have other issues. . When the difference is 50mV there is not much transfer of energy at all. yes I have tested the 1s version of them. So no they wont keep up to any high current system. The longmons i have from Batrium do alot better balancing then above when you getting closer to the end voltage ;)

If the voltage on the inverter is 0.4V off from the battery you have design issues due to wires or a bad controller. It should at most be 0.1V and that is at HIGH load. For instance when i run 300A towards my batterybank i can see 0.1V difference and thats it. Unfortunately some of the controllers have high voltage drop inside due to bad setup.

Lithium or not Lithium controller the difference is that the ones that are better for Lithium you can set float and bulk to same so you get proper CC CV charging. Thats all you basically need. The other things is taken care of by the BMS. On other hand a good controller can be controlled by the BMS to lower current and voltage for doing proper balancing. Of course you should never do full charging with out BMS or some kind of protection. Electrodacus is just a charger with BMS function built in.

Many ways of doing it and everyone have their own experience with it all.

Btw Fast charging should not have to trigger any unbalance if the packs have been built decently sorted. If the pack is smaller and stressed this will though be hard to avoid and you will hit where the IR comes in play.
 
I think the battery voltage is less than recognising voltage of the charge controller that is why it doesn't see any valuable voltage in it's input for it to charge.
Try and check the battery pack, since it's 3s find out which is the lowest and boost it up a little manually or boost the whole pack manually to raise the voltage up so that the controller can recognise it for charging.
One question to ask is
Do you connect your load from load output of the controller?
Or directly to the battery terminals.
Controller will cut off the load if the battery is going too low beyond low voltage cutoff settings If load is connected to controller output but if otherwise it will not.
Other thing to consider is that 3s pack is not always good for mppt charge controller that is not made for charging lithium batteries. It's better you change to 7s which is 24v system.
 
A short update: The fuses inside the charge controller are in a good order. Above, I rised the charging voltage up to 16V, but no current was flowing into the battery. Finally, I disconnected the battery and attached a lead-acid-battery for testing purposes. Immediatly the solar panels charged the battery; so it turns out the charging controller works fine: But I have some issues with my 3s60p-battery.
The BMS show up the three voltages for the 3s: 2.7V; 2.9V; 3.4V. So I need to look for the single cells - or wait a month until I installed my first 7s60p battery ;-)

Thanks!
 
What voltage ratings are detailed on the back of your PV panel ?

You've mentioned it's 220w, but what voltage ?
 
Hey Sean,

i'm using two old Simens SM110-24 modules in parallel:
Rated Power: 110W
Configuration: 24V
Rated current: 3.15A

Rated voltage: 35V
Short Circuit Current: 3.45A
Open Circuit Voltage: 43.5V

...but i will replace them with three 300Wp modules in parallel (Short Circuit Voltage: 38.83V; Rated Voltage: 31.98V) to charge my 7s60p
 
Hey Sean,

the specification of the controller:

Nominal system voltage: 12/24V (auto)
Rated charge current: 30A
Rated discharge current: 30A
Battery input voltage: 8 ... 32V
May. PV open circuit voltage: 92V
MPP voltage range: V_bat+2V ... 72V
Max. PV input power: 390W (12V); 780V (24V)

So i guess the controllers input range is from zero to 92V!

Thanks!
 
Connect your panels in series, MPPT chargers like higher voltages, although you've not got much to start with.
 
Ok, thanks for the hint! What do you think about buying 4 modules with 300Wp in a 2s2p configuration? I'm just asking, because of the "Max. PV input power" of 780W (for my 24V-system-to-be). Added together, the 900Wp will exeed the 780W maximum input power of the controller. But in practice i will never reach the 900Wp in midst of Germany. But do you knew, what will happen, if the solar power exeed 780W? Is there typically a fuse? Thanks!
 
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