DC ripple

[Dylboy]

Hello : )

So weird one. Had an issue with one of the 2 batteries for a backup system.

Anyway battery man came out and said the wall heaters (even though low wattage and eco and all) had caused a ripple in the lithium cells.

He said as it is a heating element it draws a lot then stops them draws more and then this causes the cells to heat up and become magnetic and all sorts thus then one or more of the cells goes to low voltage and can't charge then the others are charged to much.

Anyway this does not sit well with me as never heard of heating elements causing issues and then battery cell failure.

Is there such a thing that a heating element can cause this.

Also said that if it is a 20amp draw on the DC side but since it's a heater it is 4x more so 80A but I never seen such high DC amps reported and no fuse or anything blow.

I always thought if the load is 2000watts and you have have a 10kwh battery system it will also 5hours.
But now he says as it is a heater it is worked per second the 2000watts so will be like 20 minutes.

Anyway if anyone has some form of input please help. Maybe I am wrong and he is right but no other battery manufacturer has said anything about that of a restsiror / heating elements pulling 4 times it's rating on the DC side

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[Derlyn]

The way I understand it is that the current on the DC side will be approx 4 times that on the AC side because the DC voltage is approx 4 times lower than the AC side but the power consumed is pretty much the same.

[Dylboy]

Yes ya that is what I understand as well but this guy saying because it is a heater then it's even more and now per second and thus casuing issues and a ripple and uses more power so the batteries don't last as long

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[Isetech]

Which brand of battery?

[Dylboy]

It's a Kraft battery, locally made. Decent spec in terms of KWH etc but also the brochure said it has communication but it does not communicate with the Sunsynk...

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[Justloadit]

Have not heard of this but may offer an opinion in the reason that it may occur.

It all depends on the type of heater controller.
Most of the cheaper heater controllers are a bi metal type, which means the temperature control is based on how long the heater is connected in the circuit. So you may get a few minutes on and a few minutes off. This is not an issue to the supply, as being a resistive load, has a Power Factor (PF) of 1.00.

Now some of the more expensive controllers, use a Triac, similar to your lamp dimmer. There are 2 types, leading edge and trailing edge. Either one, works in similar manner and each have their advantages. Whilst lights are usually light loads, heaters may present a problem.

At the end of the day the way that it works, is that it only switches for a certain period of the sine wave. This type of switching will cause peaks of currents for only parts of the sine wave. Now on mains may not be an issue, but Depending on the load, the PF can vary from 0.6 to 0.9, not too sure on this as I have not done precise measurements. Not a good thing for inverters, as the battery has to cope with this up and down of current draw, and the electronic sine wave inverter creates a challenge to ensure proper switching of the electronic devices creating the sine wave. The cheaper inverters may suffer more than the more expensive ones because of the design of the switching circuits. I would think that the better quality inverters will use bipolar switching as opposed to unipolar switching of the devices creating the sine wave. I won't go into the reasons here as it becomes too technical for the discussion here. Safe to say that bipolar switching handles 'bad' power factor better, and may reduce the manner in which the current is pulsed out of the battery.

It may be possible that the battery's may not cope with this if the design was not accommodating for bad PF.

[GCE]

Yes ya that is what I understand as well but this guy saying because it is a heater then it's even more and now per second and thus casuing issues and a ripple and uses more power so the batteries don't last as long

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I have never heard of that crap before

A panel wall heater is a resistive element embedded in fibre cement and would have a power factor of 1
The only way something that is rated at 500w ( i am assuming it is normal wall heater) can actually draw more current then the str forward calculation of I=p/v is if the power factor is lagging badly .

I have panel wall heaters on my batteries and footbuddies which is an underfloor heater mat without any problems and have run them on extended outages at the office .

If the load on the batteries is sitting at maximum then you could be going over the required current draw and maybe overheat but I assume this is not the case and if there is overload on the batteries you should pick it up through the BMS software

[Isetech]

Ask the supplier for a report with all the details and post it, I would be interesting to see what this is all about.

[Dylboy]

Not a bad idea, see if it can be seen the ripple. I just think poor build and baling what we can. Even says heaters are not a power factor 1 even though a resistor.....

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