An energy harvesting project

[JulesP]

You’re certainly keen!

I don’t suggest buying any big Lithium batteries as the BMS (battery management system) installed in them can play havoc with the methodology and is the main reason behind some of my larger readings. Stick with Lead Acid, especially for getting going.

I’m still awaiting the arrival of the large relay and I’m going to take the time to gather some more data on the effect of different HVs from using different FETs and IGBT to add to the relevant section.

I’m estimating the manual will be out mid January now with the festive season stopping all my work - as expected. I will post another report though this week re using capacitors in place of the receiving battery. The electrochemistry definitely seems to be essential to the energy gain phenomenon.

Julian

[pearldragon]

[JulesP]

Hi all,

Just a quick update.

The manual is pretty much ready but, due to ongoing postal strikes here in the UK, I am still awaiting a few key components. Until I receive those I can’t complete the PCB assembly and install the revised circuit to test it. I need to do that to confirm parts of the manual, for example, the diagnostics section.

So at the moment it’s looking like I won’t make the Manual live in mid-December as planned but hopefully closer to Xmas and, if necessary soon after. Nevertheless, I am now going to make the Mega link to the folders available, with access to all the Appendices and relevant research papers that will be of interest to some. The ‘Manual’ and ‘PCB files’ folders will just be empty for the time being. I also attach here screen grabs of the front cover and the Contents page.

Then in due course, I will post to say that the Manual and the other files are also up on the link you already have.

https://mega.nz/folder/YUM0nLoT#bYpLIazqMM5K2IrEQjghDQ


Jules

[pearldragon]

Hi Julian,

Thanks for answers and PWM link. I'll await your next updates on parts list and manual before asking more questions on the parts.
Good luck finishing to manual! looking forward to read it.

Best regards,
Rodolphe

[JulesP]

Please note that some of the component designations in the above list will change before I fully release it. For example, the PCB design software sometimes uses U instead of D for some of the diodes and did so for the custom made footprint for the large relay. These will be corrected before mid December to avoid confusion. If you’re confused now you will need to wait a few weeks for clarification.

[JulesP]

Hi Rodolphe,

Yes, all the resistors are 0.25W and the ‘+’ means polarised or electrolytic.

The FET mount was a hangover from my previous build in that it let me simply plug and unplug FETs in a matter of seconds. However, it was a custom-made part in effect that I can’t expect others to produce and so I have removed it from the v4 board but it slipped through on the listing. Instead, there are two sets of holes on the new PCB for two active devices to be installed as normal.

The first draft of the manual is now written at 69 pages and 23,000 words. But I need to check some of its details by actually assembling the new board. So all is looking good for a release around the middle of December.

Links to the other components will be in the manual but here is one type of PWM module:

https://www.ebay.co.uk/itm/203966572841?

PBF means Lead (Pb) Free and Google will tell you that.

J

[pearldragon]

Hi Julian,

Regarding post #29

It would be like adding 1 to 20 and wondering if having 21 is worth the extra effort and expense.

I understand what you mean, you’re right (based on your data so far).

STW12N170K5 I cannot find on aliexpress either, STW12N150K5 I can.

Regarding post #29
I have a couple of questions regarding the parts list, probably more if look longer at it (i.c.w. looking at the diagram V4), but will not do that for now and stay with the questions I have for now:

Gate driver
IR2121 I find the version without the ‘pbf’ the end on the website where I generally buy my components*. Any idea what that PBF stands for? I looked on an infineon spec sheet where PBF was mentioned in brackets, but could not find a feature that was specific related to that PBF version.

*https://www.reichelt.com/de/nl/hs-po...ch=ir2121&&r=1

Did you use a socked, is that what you indicated with? Like this one:
https://www.reichelt.com/de/nl/ic-so...ht_sldr::41574
If not I assume there is no harm in doing so?

Do you have a link for the PWM module + display that you used?

Capacitors:
-all electrolytic ones, voltage rating min 20V?
-when you put the ‘+’ at the end, you mean indicated value is the min. value (capacitance)?

Resistors:
-all wire-wound versions, 0.25W?
update 2022-12-04 -> depending on the type of resistor they do not come standard in 0.25W. I selected 'thin film' resisters, 0.6W and some 0.4W.

What do you mean with ‘FET mount’ do you have link for that part?
Do you have a link to the heatsink for the FET? (to make sure I order one that is not too big/interferes with other components) And did you use heat conducting paste in between?

More questions next time

Thanks for uploading the parts list!

Regarding post #31
I just received my aliexpress diodes, also with +/-E5,- shipping costs via DHL, so no idea why Jinftry asked so much, I send them an e-mail about it.

Best regards,
Rodolphe

[JulesP]

If you can’t find the 120/150/170 devices easily you will still get good results with the STP20N95k5 which is definitely available on AliExpress at a reasonable price. 95% of my tests results were done with this FET so no one needs to be hindered by the current dearth of some devices.

Having said that, I paid $52 for the 150&170k5 INCLUDING delivery of $5. You have to ask for the cheaper postal service rather than FedEx etc. The delivery time is variable but I got mine in Uk in about 2weeks which was perfectly acceptable.

[JulesP]

While I’m posting here is the components list for the new v4 PCB.

[JulesP]

I have attached grabs from two docs in the folder indicating that delivering cap dump type pulses to the battery did very little and would required another circuit. The contribution to CoP from such would not be noticed next to that from direct HV pulsing. It would be like adding 1 to 20 and wondering if having 21 is worth the extra effort and expense.

Some of these chips are hard to come by. If I find other suppliers I will post them, especially if they are cheaper to deliver. AliExpress etc can be good for many things but I haven’t found any of the 150/170k5 IGBTs on there so far.

[pearldragon]

Small update/info for those who want to build Julian’s setup as well and considering where to buy the mosfet and diode. This is my experience so far:

Jinftry:
Quick and friendly with replies, but sending parts via DHL cost about 50Euro/USD, so mainly an interesting option for bigger orders.

Jinghongyang electronics technology (post #17):
I’ve sent them several inquiries, but they never replied

Aliexpress/eBay:
Seem quickest and cheapest options.

Regards,
Rodolphe

[pearldragon]

Hi Julian,

The answer to your question is addressed by the doc ' Report - Cap Dump Circuit' in the docs folder.

I assume you refer to the document “Interim Report – Battery charging vs CDF (Oscillator)”? I read through it but could only find reference to catching the HV spike when switching OFF the mosfet, but no reference to use a cap dump circuit to catch the switching ON spike.

In other words, the HV spike when switching the mosfet OFF would still go directly to the battery, while the spike when switching the mosfet ON would first be caught by a capacitor and then dumped to the battery. So both spikes would be used, instead of only one. For an (over) simplified sketch of catching the switch ON spike, see attachment.

PCB looks very nice Julian! Curious to hear how it performs.

Best regards,
Rodolphe
Attachment.pdf

[JulesP]

But the following thought crossed my mind:
By grounding this ‘switching-on-pulse’, we are wasting it… could the circuit not be constructed that we catch this pulse too? Since it is in the reverse direction, I guess we would need a capacitor for it first and when voltage has risen high enough, dump it to the battery -> so a cap dump circuit after all . But only to catch the switch on spike.

The answer to your question is addressed by the doc ' Report - Cap Dump Circuit' in the docs folder.

The new PCB v4 has arrived and the test/check build will start in the next week

[pearldragon]

Hi Julian,

The role of the body diode is to allow a current path to ground during the period between switching on and off to release the charge collecting at the junction and is particularly relevant when switching inductive loads. However, they have a slow response time that can cause a significant build-up of charge at the junction and with associated problems, depending on the circuit you have and the application.

Adding an external fast recovery diode, thereby shunting the body diode in parallel, will release that charge more effectively than the indigenous body diode and usually prevent the body diode from ever having to switch on.

This is all very clear how you explained it. Thanks.

Of course, we do want this pulse so we don’t add an additional, above-mentioned diode across the inductor to discharge it to the battery

I understand what you mean, but the sentence looks/reads a bit strange to me, what I expected you to say was: Of course we do want this pulse, so we don’t add an additional, above-mentioned diode across the inductor. Without this diode the pulse discharges to the battery.
But again, I understood what you meant.

Please note that this video does not make reference to the spike that results from the coil switch-on but focuses on the one at switch-off.

Well exactly that confused me a bit, that put me on the track that the built in diode was already performing the function of the external diode in your circuit, but all is cleared up with your explanation.

But the following thought crossed my mind:
By grounding this ‘switching-on-pulse’, we are wasting it… could the circuit not be constructed that we catch this pulse too? Since it is in the reverse direction, I guess we would need a capacitor for it first and when voltage has risen high enough, dump it to the battery -> so a cap dump circuit after all . But only to catch the switch on spike.

PS. I'm busy writing the assembly manual and so will be limiting my responses on here for the next month or so.

No worries, I might post some more questions here, but please don’t feel any pressure to respond to them quickly. And maybe Gary will be able to help out too.

Best regards,
Rodolphe

[JulesP]

Hi Rodolphe,

I’m not an electrical engineer but my understanding on this is that all MOSFETs have an internal, also called body or parasitic diode, by virtue of the PN junctions that are part of their innate structure. This is shown within the symbol for the FET on the right hand side (see pic).

The role of the body diode is to allow a current path to ground during the period between switching on and off to release the charge collecting at the junction and is particularly relevant when switching inductive loads. However, they have a slow response time that can cause a significant build-up of charge at the junction and with associated problems, depending on the circuit you have and the application.

Adding an external fast recovery diode, thereby shunting the body diode in parallel, will release that charge more effectively than the indigenous body diode and usually prevent the body diode from ever having to switch on.

For regular power switching, where you don’t want the flyback pulses appearing at the Drain and causing problems (EMI etc) then often another diode is used to discharge the ‘damaging’ pulse and which the body diode can’t do since it's being reversed biased.

Alternatively, many of these active devices have an 'avalanche rating' whereby over a certain voltage they break down to discharge the pulse to ground, This is shown in the other graphic. This latter feature is the limiting factor in the peak flyback pulse voltage as I have mentioned elsewhere.

Of course, we do want this pulse so we don’t add an additional, above-mentioned diode across the inductor to discharge it to the battery (as is shown in this video: https://youtu.be/6YOctFtOuwY). Please note that this video does not make reference to the spike that results from the coil switch-on but focuses on the one at switch-off.

You might reasonably ask why we don’t do that as the pulse will still arrive at the battery. I believe the key answer here is that shunting the coils with a diode would prevent the spike voltage from building up to the 1-2kV that we do see and want and instead clamp it at a low value, along with a small amount of current. This is a very different result from delivering a high potential pulse directly to the battery terminal which is what we need to elicit the ‘phenomenon’ at the interface of the pulse and the electrochemistry.

So instead we let the voltage spike exist as a pure voltage potential delivered to the battery terminal instead of using an additional diode across the coil, as shown in the video, which would inevitably change the type, quality and magnitude of the pulse arriving at the battery.

However, we are still limited by the FETs avalanche rating and, if the FET we use didn’t have such a rating, then it would be easily damaged by the very pulses we seek to use.

So to summarise, an external FRED, Schottky or another type, is added to support the discharge of the pulse energy generated during the FET on duration and which would otherwise build up as charge at the Drain-Source PN junction. This is due to the slow response of the body diode, which is not optimised for this role, and is not there from a deliberate design choice but on account of the way the device is constructed.

I hope that gives you some clarity.

Jules

PS. I'm busy writing the assembly manual and so will be limiting my responses on here for the next month or so.