I've done a lot of searching on this error, and haven't found an answer.

My system is a Kodak OG-10, 10kw inverter, with 2x Kodak 5kw batteries.

Everything works great!

But there have been two occasions where we ran large tools in the workshop, which probably took a high startup draw.

The inverter tripped (and the master battery had a flashing red light) with warning 71.

The manual says warning 71 means this:

"If battery status is not allowed to discharge after the communication between the inverter and battery is successful, it will show code 71 to stop discharging battery."

I actually don't know what that means? 

What's going wrong?

The batteries are 1C, supposed to be able to discharge at a high rate - and of course the inverter is 10KW, which a table-saw or big grinder is not going to max out surely, no matter how heavy the start-up.

Any advice please? Any settings that I could look at?

2 hours ago, JonanGrobler said:

I've done a lot of searching on this error, and haven't found an answer.

My system is a Kodak OG-10, 10kw inverter, with 2x Kodak 5kw batteries.

Everything works great!

But there have been two occasions where we ran large tools in the workshop, which probably took a high startup draw.

The inverter tripped (and the master battery had a flashing red light) with warning 71.

The manual says warning 71 means this:

"If battery status is not allowed to discharge after the communication between the inverter and battery is successful, it will show code 71 to stop discharging battery."

I actually don't know what that means? 

What's going wrong?

The batteries are 1C, supposed to be able to discharge at a high rate - and of course the inverter is 10KW, which a table-saw or big grinder is not going to max out surely, no matter how heavy the start-up.

Any advice please? Any settings that I could look at?

What is the kw rating of the table saw and grinder as warning 71 is bms related your batteries gets disconnected due to overcurrent on startup. Your table saw motor and grinder is starting up under load. Your 2 x 5kwh batteries will tolerate not more than 8.7kw on the ac side or around 39 ac amps. (203 amps dc)Your startup on motors could be 8~10 times run current it is called LRC locked rotor current which happens on startup.

Edited January 12, 20251 yr by TaliaB

Thanks TaliaB, it sounds like you understand exactly. 

The table saw on its own trips warning 71.

It's rated to take only 3kw on startup, runs at about 1kw.

Which is why I was wondering if there was some setting I have that is limiting the batteries discharge rate? IS there something I can look at and adjust?

We have a 5kw generator that can run the table saw without a problem.

11 hours ago, JonanGrobler said:

Thanks TaliaB, it sounds like you understand exactly. 

The table saw on its own trips warning 71.

It's rated to take only 3kw on startup, runs at about 1kw.

Which is why I was wondering if there was some setting I have that is limiting the batteries discharge rate? IS there something I can look at and adjust?

We have a 5kw generator that can run the table saw without a problem.

Check parameter 41 it is by default disabled this parameter sets the battery discharge current if it should be enabled if that is the case set it at 190 amps just below max discharge current of your 2 x 1C 100ah batteries in parallel.

Edited January 13, 20251 yr by TaliaB

Talia - thanks. You're super knowledgeable.

I went to check this setting, but yeah it was already disabled.

I've set it to 180 amps, but I'm guessing that wasn't the problem, and rather that there was something wrong with the tablesaw.

Not entirely sure what else it could be, because the table saw ran just fine on a 3kw generator.

Thanks for your help.

Hi,

part of your problems might be the small battery. 10kWh battery for 10kW inverter seams to me low. You should have twice as much. The whole system would become more stable. In particular the voltage sag on the battery due to high load would be less. Just think of it: 10kW load draws around 200A from the battery. With only 200Ah capacity that's 1C. It's perhaps the maximum current acceptable according to battery specs but it should be avoided if you care for battery life. The system should be conceived for a  maximum current of 0.5C.

Thanks for the insight Beat.

We are on a solar-only system, and before upgrading to this 10kw system last year we were running entirely off a 3kw system, with deep-cycle lead acid batteries.

So to have a 10kw lithium ion battery system for us is huge, and we're very used to keeping power low. We pretty much never go above 2kw usage, and that's only when we have the pump running.

10kw inverter was just for future proofing. I will definitely look into doubling my battery storage in the future - it's just expensive as heck.

I still suspect there might be a fault with the table saw itself.

57 minutes ago, JonanGrobler said:

I still suspect there might be a fault with the table saw itself.

i had a similar experience with a large angle grinder and a cut off saw, what helped was pulsing it for half a second or so, the off for half a second or so, for 3 or 4 successive times, until it was up to speed and then. once it was up to speed, it would cut fine without complaints/errors from the inverters end...

2 hours ago, Kalahari Meerkat said:

i had a similar experience with a large angle grinder and a cut off saw, what helped was pulsing it for half a second or so, the off for half a second or so, for 3 or 4 successive times, until it was up to speed and then. once it was up to speed, it would cut fine without complaints/errors from the inverters end...

I still prefer using these controllers on high power tools like table saws, angle grinders, cutters for steel. Basically any brush motor without speed control. All the above I manage to start from a 2.4kW 24V Axpert. Some I don't even run at full power. They are kind to the inverter and no more high starting spikes. 

I have a 4kW with 0-100% power meter that adjusts via up and down tactile switches. Some junk info these units were one of 2 electronic projects we could be asked to do during our trade test way back in the late 1970's.

I build one before my trade test inside a 4x4 box and used the full wave design with pot for decades in the garage. 

https://www.communica.co.za/products/cmu-ac-speed-dimmer-contr-6000w?variant=17184331202633&sfdr_ptcid=31591_617_495127808&sfdr_hash=d937f832f4bff6317af0b7c2114f8972&utm_source=www.communica.co.za&gad_source=1&gclid=CjwKCAiAtYy9BhBcEiwANWQQLzYeTb6d2Fvn1wWsxTb-Ex4gmFe_smytp6UQMHBvhmD_dMGoDjRvCBoCTpoQAvD_BwE

12 hours ago, JonanGrobler said:

I still suspect there might be a fault with the table saw itself.

Sorry, big motors are just brutal with their start-up current.

For what it's worth, I don't like either of the above two suggestions. Switching on an off rapidly will confuse the control systems. The phase control of "dimmers" will also confuse the control systems, and doesn't actually reduce the peak current all that much, unless there is filtering, which would not fit into that small box.

The proper way would be a VFD (also called VFC I think), which chops the power (like the phase control dimmers, but at a higher frequency), but also has filtering. But this is quite bulky and expensive.

There's no easy way around it: to start a large motor, you will need a large battery.

Thanks Coulomb - I'm with you. Switching on and off rapidly sounds a bit strange, and I don't really know anything about dimmers.

My dad has spoken about adding big capacitors, to help with that start up spike? is that an option?

Ultimately, we need to get another 10kw of batteries - not in the budget right now.

3 hours ago, JonanGrobler said:

My dad has spoken about adding big capacitors, to help with that start up spike? is that an option?

That probably won't help. There is also the issue of "starting" the capacitor (assuming it goes across the battery). The inrush of a capacitor across a battery could be worse than the in-rush current of the motor! There are ways of "precharging" the capacitor to avoid this.

The problem is the large current that results when the applied voltage is full value, but the back-emf from the spinning motor is initially zero and for a few AC cycles well less than the applied voltage. The current is then limited essentially only by the resistance of the windings and cables. If the capacitor had enough energy to hold up the battery bus while starting, there is still the issue of whether the inverter's IGBTs can handle the overload current, and if the inverter's firmware will allow this overload for long enough to get the motor started.

On 2025/02/06 at 6:39 AM, Coulomb said:

Sorry, big motors are just brutal with their start-up current.

There is a way around it: Put a resistor in series with the starting motor and short it after the motor has come up to speed. Practically I could realize it like this:

Get an outlet box with a switch. Wire it such into the motor cable that the outlet is in series with the motor and the switch will short circuit the outlet. Connect a laundry iron (or any other heating appliance) to the outlet. With the switch you short circuit the iron outlet when the motor has reached speed. This arrangement will never draw more current than the naked iron.

20 minutes ago, Beat said:

Put a resistor in series with the starting motor and...

As they used to in the bad old days of DC motors. Trams (now called light rail) had arrays of resistors under the floor, and a controller that switched through increasingly low resistance until the tram was running on the full 600 VDC (415 VAC three phase, rectified by mercury rectifiers). There was a considerable jolt as each new resistor was switched in. The tram motors were series wound, which I think were better at starting than the more usual shunt field motors. I guess that AC motors would be startable in much the same way.

7 hours ago, Coulomb said:

As they used to in the bad old days of DC motors.

Yes - but most power tools as well as my circular saw are powered with brush motors. They are built and work just like good old DC motors but on AC with high starting torque causing high current surge. Induction motors on the other hand have low starting torque despite high starting current going up to 5x rated current. Therefor there used to be the 3 phase induction motor with 3 slip rings connected to the rotor windings. The stationary brushes of the slip rings were connected to a set of variable resistors for start up and speed control. The resistance was gradually reduced as the motor picks up speed until short circuit for full speed. There we are again with the startup resistor.

Remember the resistor pedal for sowing machines? The same technique. When my ex wife complained about her sowing machine being too slow I installed a rectifier bridge in front of the motor. The AC brush motor now fed with DC had lower resistance as the inductance with AC, therefor drawing higher current and running faster.