Proper process for balancing two Dyness batteries

Stonemason said:
I have a bank of two Dyness batteries on my Sunsynk inverter which I installed 3 years ago. The two batteries are different distances from the inverter and they were installed 6 months apart
In all the time I have had them, they have always been in perfect balance.
What is happening at the OP is not normal. Get the installer to take the weaker battery to the supplier for replacement. There is no other option regardless of the opinions expressed in this thread
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Your batteries were prob from the same batch. There is no problem. 90% of 10.2kWH is 9.1kWh which is what he got technically.
 
wingnut771 said:
Your batteries were prob from the same batch. There is no problem. 90% of 10.2kWH is 9.1kWh which is what he got technically.
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No, they were not. Even their user manuals differed. The OP's one battery is faulty and the only remedy is for the battery to be taken back to the supplier for replacement under warranty.
 
Stonemason said:
No, they were not. Even their user manuals differed. The OP's one battery is faulty and the only remedy is for the battery to be taken back to the supplier for replacement under warranty.
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and after all that faff still get 9kWh?
 
wingnut771 said:
and after all that faff still get 9kWh?
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It is clearly a problem and in time it may get worse. Anyway you argue it, the faulty battery must be repaired or replaced.
The idea with these batteries is that they should last you 10 years. If a problem already starts to manifest at 2 years then it can only go downhill from there.
 
Stonemason said:
It is clearly a problem and in time it may get worse. Anyway you argue it, the faulty battery must be repaired or replaced.
The idea with these batteries is that they should last you 10 years. If a problem already starts to manifest at 2 years then it can only go downhill from there.
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What happens to you in 3 years time when you add a third battery and the 3rd battery does this but you still get full capacity?

Isn't the warranty capacity based?
 
wingnut771 said:
What happens to you in 3 years time when you add a third battery and the 3rd battery does this but you still get full capacity?

Isn't the warranty capacity based?
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Is either works or it does not. In the OP's case it does not work as it should. The supplier will have no leg to stand on.
 
wingnut771 said:
What's not working? 9kWh is 9kWh.
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Yea the problem is 90%

Is also an estimate
It may also be 95% of capacity

ie that the one 5kwh is actually a 4kwh

And thus that one may be running down close to 0%

The bms is told you have a 100Ah bank it calculates 10% based on 100ah -discharged 90ah thus it is at 10ah/10% soc

I would wager there is a good chance the system shutsdown before it can come close to zero %

You would have to run it down to protection voltage at the bottom
Once till shutdown to know that they are indeed perfectly sound 5kwh batteries

Then the bms behaviour may also become correct

As it updates SOH only if it hits the bottom
 
leon.davibe said:
Yea the problem is 90%

Is also an estimate
It may also be 95% of capacity

ie that the one 5kwh is actually a 4kwh

And thus that one may be running down close to 0%

The bms is told you have a 100Ah bank it calculates 10% based on 100ah -discharged 90ah thus it is at 10ah/10% soc

I would wager there is a good chance the system shutsdown before it can come close to zero %

You would have to run it down to protection voltage at the bottom
Once till shutdown to know that they are indeed perfectly sound 5kwh batteries

Then the bms behaviour may also become correct

As it updates SOH only if it hits the bottom
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The inverter showed 8.9kWh with 89% used. The math shows there is 2% missing. He would have got more if he used voltage based AGM mode. We weren't trying to get to zero.
 
wingnut771 said:
The inverter showed 8.9kWh with 89% used. The math shows there is 2% missing. He would have got more if he used voltage based AGM mode. We weren't trying to get to zero.
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Yea i get that

Just meant that the 90% ie 10% left does not mean that both the batteries was at 10%

Since the SOC is calculated by avg of the 2 batteries

2% +18% is still shown as 10% soc

And since the indicators wasn"t in sync

A person may be degrading one battery quicker than the other
If the one runs lower

Onlly thought with a brand new battery if sometjing doen't look right it might not be a bad idea to check it

A brand new battery should pass a capacity test, so easy enough run it down to alarm voltage charge at constant amps and check tbe charge time , at 0.5c it is 2 hrs and you have answers

If anythjng is wrong with the battery ie bad cell or out of balance out of the box , just rma it

Rather sooner than later

Brand new a supplier can't claim user abuse
 
leon.davibe said:
Yea i get that

Just meant that the 90% ie 10% left does not mean that both the batteries was at 10%

Since the SOC is calculated by avg of the 2 batteries

2% +18% is still shown as 10% soc

And since the indicators wasn"t in sync

A person may be degrading one battery quicker than the other
If the one runs lower

Onlly thought with a brand new battery if sometjing doen't look right it might not be a bad idea to check it

A brand new battery should pass a capacity test, so easy enough run it down to alarm voltage charge at constant amps and check tbe charge time , at 0.5c it is 2 hrs and you have answers

If anythjng is wrong with the battery ie bad cell or out of balance out of the box , just rma it

Rather sooner than later

Brand new a supplier can't claim user abuse
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I dont care about soc, I only care about voltage when in the knee of the curve.

I eagerly wait for the multimeter pics.
 
wingnut771 said:
I dont care about soc, I only care about voltage when in the knee of the curve.

I eagerly wait for the multimeter pics.
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Got the multimeter, but struggling to find clear and safe steps for measuring the voltages on these batteries and I am not gonna lie — I am not playing around with electricity.

Would I need to disconnect the batteries when fully depleted to properly measure this?

Also read on Powerforum that Dyness recommends:
Discharging each battery as individual Master to shutdown, one after the other.
Reconnecting the BMS comms between the batteries and setting Master and slave as per the manual.
Charging the batteries in parallel to full.

 
Hanno Labuschagne said:
Got the multimeter, but struggling to find clear and safe steps for measuring the voltages on these batteries and I am not gonna lie — I am not playing around with electricity.

Would I need to disconnect the batteries when fully depleted to properly measure this?

Also read on Powerforum that Dyness recommends:
Discharging each battery as individual Master to shutdown, one after the other.
Reconnecting the BMS comms between the batteries and setting Master and slave as per the manual.
Charging the batteries in parallel to full.

Click to expand...
You can touch 48V DC no problem. Just measure on the battery terminals where the cables attach. Measure under load and with no load.

Powerforum recommendation sounds promising.
 
Hanno Labuschagne said:
Got the multimeter, but struggling to find clear and safe steps for measuring the voltages on these batteries and I am not gonna lie — I am not playing around with electricity.

Would I need to disconnect the batteries when fully depleted to properly measure this?

Also read on Powerforum that Dyness recommends:
Discharging each battery as individual Master to shutdown, one after the other.
Reconnecting the BMS comms between the batteries and setting Master and slave as per the manual.
Charging the batteries in parallel to full.

Click to expand...
Safe threshold for DC is about 120V. 58 which i assume is the max you would see on Lithium is far below that. 58AC though will shock you.
 
wingnut771 said:
You can touch 48V DC no problem. Just measure on the battery terminals where the cables attach. Measure under load and with no load.

Powerforum recommendation sounds promising.
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It's not the 48V that will get you, it's the 100A.

I don't fck around electricity either, even if I know what to do. Anything can happen for any reason. I'd rather someone else take the chance of getting zapped...
 
Mike Hoxbig said:
It's not the 48V that will get you, it's the 100A.

I don't fck around electricity either, even if I know what to do. Anything can happen for any reason. I'd rather someone else take the chance of getting zapped...
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If you're really worried, wear slops and dish washing gloves. Anyway, your hands are holding multimeter probes. I doubt those wires can handle 100A.
 
wingnut771 said:
If you're really worried, wear slops and dish washing gloves. Anyway, your hands are holding multimeter probes. I doubt those wires can handle 100A.
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48V x 100A = 4.8kW. Or 50A at 0.5C. Still, 5A is enough to kill you, let alone these amounts. Those DC cables are thick for a reason...
 
Mike Hoxbig said:
It's not the 48V that will get you, it's the 100A.

I don't fck around electricity either, even if I know what to do. Anything can happen for any reason. I'd rather someone else take the chance of getting zapped...
Click to expand...
For current to flow you need low resistance. Skin has very high resistance. 100A wont flow through you at 50V DC. I=V/R. The voltage is not high enough for the resistance. Its basic electricity rules.

You need potential difference for current to flow. I have done tests on installations where there was a 110VAC leakage on a panel and I still went ahead and worked on it. You can feel the zap and its just uncomfortable but you get used to it. I dont recommend anyone doing that though. But 48VDC wont do jack **** to you.
 
Mike Hoxbig said:
48V x 100A = 4.8kW. Or 50A at 0.5C. Still, 5A is enough to kill you, let alone these amounts. Those DC cables are thick for a reason...
Click to expand...
Just because you're scared of 48V DC doesn't mean other people have to be. Remove the caps if you cant get the probes in from the side and stick them on the screws. Its impossible for current to flow through you.
 
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