Search results

These would be very close. Battery voltage is the cell pack voltage. Bus voltage is the voltage on the BMS output to the inverter. If low current is flowing these are extremely close. If large current is flowing the difference is caused by the resistance introduced from the wires, pack and the...

Provide pictures of the battery, not picture of the BMS UI :) .

The BMS can not handle situation with totally unbalanced cells. You are supposed to balance them before assembling the pack. Easiest solution to do it without disassembling the pack is to turn off the BMS and charge each cell up to 3.65V with power supply. Stop charging once current drops below...

Did you balancer your cells before assembling? Can you post a few pictures of your battery?

Yes. But since it is like 100mA discharge you'll need 10 hours for each Ah difference. It will take forever :) .

Here is an example for MPPT heater controller - https://projecthub.arduino.cc/stevetearle/loadmaster-xp-a-smart-pv-mppt-solar-hot-water-controller-5264c7 . Details are pretty well explained.

As long as you have a suitable wall (concrete) and proper stand there is no issue. I have a 280Ah 16S battery mounted this way and it is over 200lbs. 4 concrete anchors + an iron stand made of 20mm square profiles with 2mm thick wall.

The process should be automatic, not you manually doing anything. The SOC will drift with the time and the BMS will compensate for that drift every time when the cells are fully charged (preferably) or discharged. So make sure that you reach fully charged state (like 3.45+V per cell) on regular...

Voltage will go over 3.4V only while charging. Then it will settle down to around and below 3.4V. Having a cell at 3.5V while charging means that it is fully charged. No point in going above that. Having wrong SOC Ah will only lie the inverter about the remaining capacity. I can't think of...

For AC - yes. But the OP is considering DC as source. Fixed load works in fixed conditions, but the power you produce is not a constant. That's why there are MPPT trackers. Even such with DC output for heating elements. They use PWM to reduce the power on load side and dynamically control the...

Induction heater has lower efficiency (~80%) compared to resistive heater. There are even OOB MPPT devices for resistive loads like water tank heaters. I don't see benefits in considering inductive heating here.

And you are slowly coming to my solution. Instead of storing heat energy, I store electrical energy in the battery. And when heat is needed I start the heat pump. The pros - no heat energy losses and close to constant round trip energy losses (~20%). And electricity can do a lot more than heat...

Did you calculated the losses? 500C with heat insulation will lose a lot more energy than 100C with the same heat insulation. Roughly 5 times more.

I can share what people do here when we are talking about a storage tank for a lot of energy - they use water tanks from trucks with decent heat insulation. With some math and 16m3 tank you'll get close to 18kWh of stored energy for each degree Celsius of temperature rise for the water inside...

So I think I found a solution. Still testing it, but the initial run for several hours shows very promising results. How it works - constantly monitor the PV inverter. Use some greedy logic to determine if more power can be produced and if yes - force the battery inverter to increase the...

Yep, I'm aware of it. But when throttled the PV inverter says that the external system is dictating the limit, not that the max produced power has been reached. The PV inverter actually catches up quite fast. The Home Manager 2.0 that controls the zero export is likely the cause. But I'll be...

Some more research confirms that this is caused by the SMA Home Manager and its algorithm for limiting feedback. During trottled periods devices state that they are limited by external PV system control. Now I'm considering turning off the devices' external control and setting them to some...

The system is grid tie with two inverters - SMA Sunny Boy 3.6 and SMA Sunny Island 4.4. The problem is the Sunny Island ramp up speed when charging. If there is drop in the sun (short cloudy condition, i.e. 30 seconds) and then full sun the system does not get to full speed in matter of seconds...

Smaller MPPT controllers mean more MPPT trackers with fewer panels in strings. This would optimize the cases with partial shadow. Another benefit is the failure scenario where a single controller fails, but you still get power from the remaining. A larger controller usually means higher MPPT...

A proper fuse is highly recommended. In my case, the fuse is between the BMS and the cells. I doubt that it would save the BMS, but will definitely prevent fire in short-circuit situation. Look around in the forum. There are multiple discussions on the proper fuse type and specs. The main thing...

Yep, looks like that. The SOC should get correct after a full discharge and charge cycle. The BMS should also recalculate the capacity it shows and this can be used as an indicator for cell healthy. The other indicator has been explained - the battery internal resistance. How many months...

There may be a single defective cell. Can you measure the cell voltages when it gets to 0% SOC and at 10% SOC? If the BMS provide cell voltages you can also get them from there.

It is normal. Heating up depends on the losses. Charging with 100A generates roughly 10W losses per cell in pretty good battery build scenario. So these are 40W heating up your battery. This is just an example, but it gives the idea about what should you expect. Same goes for discharging. It...

I never tested them out. But other folks ordered from the same seller and at the same time tested them to ~295Ah. Not grade A definitely. But they look to be in perfect condition - totally flat against each other, very close IR. Working for over 7 months now and no complains so far.

The price is close to what you can get from China including shipping. Octomber last year I got exactly CATL 280Ah cells with busbars for 135USD/pcs. Prices are lower now. And mine were "grade A" according to the seller, but we all know that this is likely incorrect. Think about what you'll be...

To get more the only option is to put second small rows of 3 panels behind each of the long rows. But this will almost double the cost (additional MPPT trackers, panels) and will provide about 30-40% more production conditionally. Additionally, the access to maintaining the system will get...

Yep. The idea is that users/installers should not understand the charging processes. It should be plug and play. The battery manufacturer is responsible for setting proper parameters and providing a warranty for the product. And to guarantee that installers would be able to mess things up they...

Do the drawing and math to calculate at what sun altitude there will be no shading. Then open the sun calculator and check in different seasons when shading will be gone. The calculate the estimated energy output and see if it suits you. The process is not simple, but there is likely calculator...

And what happens after it reaches 99.5% SOC? Does the voltage drop? Or it stays at 55V/56V until you demand energy from the battery? Mine stays at the configured charging voltage. The voltage drops when the sun goes down and there is demand for energy.

Yep, you may reach 99.5 at both voltages. But this is not a problem. This is still a fully charged battery. The SOC gets recalibrated at several percentages. 98.2% is also a calibration point. If you are getting to 98.2 and over it on daily bases, your SOC will not drift with time.

Same here. I don't care for the last 0.5%. What I care about is fully charging the battery. 3.5V per cell is more than enough. Getting this done without the BMS turning on and off the MOSFETs is good enough for me.

What was the highest cell voltage and the total pack voltage when the 100% SOC was reached?

If REPT cells are in general good I will go with them. I don't look for grade A cells. Storage grade (grade B) should be more than enough.

I'm looking for 15 or 30 kWh storage. Current offer is for REPT 280Ah, EVE 304Ah and CATL 302Ah. Can you, please, share some quick feedback on the different brands? CATL - I've used them and so far so good. EVE - I've been reading in the past for issues with low capacity on some LF280K, but...

If the problem exists only with high current charge/discharge - check your busbar connections. Cells seems pretty well balanced in most log entries, but there are entries with big deviations. So this seems to be either bad busbar connections (high connection resistance) or bad cells (high...