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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.

Post Subject: Again about the PurePower battery charger.Posted by Romy the Cat on: 12/27/2011

Lx_ wrote:
Indeed when the battery gets charged the sound is different from when it is charged. I have noticed this especially after the battery is discharged completely (after PP shuts itself down when running on battery). I think this is also true whenever after running on battery, not only after full discharge, but to a lesser extent.

I have also wondered if this could explain differences in sound that I cannot explain otherwise: no other device getting on in the house, yet sound gets worse. Could it be that the PP is charging the batteries? Indeed under normal operating conditions some power must be drawn from batteries, also the batteries discharge naturally. So they must be recharged. I do not know if this is done continuously or if some discharge level must be reached before PP engages the charging circuit (which may impact sound).

This is very simple, the problem you describes and I completely concur derives from the fact the PurePower improperly implement at the unit charger. When battery is discharged the impedance of the battery drops, consequentially the charging current is very high. Some whatever circuitry they use to charge battery (switching DC-DC converter or classing transformer-rectifier-filter) is passing very high current. In fact if you completely discharge the buttery then for the first few second the charger will be screaming at 90db with a voice is a wounded hyena. In a few second as the battery get charged a bit the impedance of the battery rice and the current subdued.

So, the PurePower charging circuit is strong enough made to care the “cruse current”, or the minimal current of the fully charged battery. As the battery gets discharged then the charging circuit operates in semi-stressed mode. I did report this observation to PurePower and I did expressed my opinion to them that it is NORMAL as the typical operation of the regenerator with battery fully charged and the charger passing high current is only temporary, very short state.

However, having said above I do feel that enter charging circuitry is the biggest liability of PurePower unit and I wish they would revise it. The worsening sound during high current charge is just a symptom of much wider problem. The battery charger is the ONLY one element of PurePower that hard connects the outside line with inside line. I hope it is has galvanic decoupling of some sort (isolation transformer) but the biggest problem is that the charging circuitry creates a hell of noise inside of the units. If you put a scope at the PurePower output then you will see a default PurePower waveform. Then, if you just put the unit in battery testing mode, what will flip unit for a few second to battery operation, than you will see as charger kicks in that over the default PurePower waveform will be a lot of distortions and they will be gradually go away as battery get charged. If you take a stethoscope and listen the PurePower chassis then you will clearly hear that the distortions on the waveforms will be very harmonious with the noise of the charging transformer (or whatever they use).

I do not know if it is unconfident filtration of charging current, the emitted EMI/RMF radiation of the charging elements or anything else but I know that it might be fixed. The PurePower needs very slightly to beef up the charging mechanism, or perhaps to unit better filtration and most likely to shield it. I am absolutely confident and I have written many time about it that the “fussiness distortions” that are not there during the battery operation and are there during the line operation are derivatives from improperly operating charging elements of PurePower. I do not know if PurePower work on it. The unit was initially designed I am sure for UPS service and those level of details were not in the mind If would not take a lot of efforts for PurePower to revise the charging elements, I hope they go there sometimes. Well, I can get from them a bypass switch for years, how long you think it will take for them to put a mu-metal shield around the battery charger?

Well, saying all of it I am a bit afraid that changing something PurePower people might accidently loose the glorious sound that I think they have today. So, I am kind of want to stress them to work on the "defetive" charger but at the same time I a bit afraid of it. Who knows why this damn regenerator sounds so good? It would be a hideous discovery if it turns out that the PurePower unit sounds so good…. because the distortions from changer. The Cat

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