An energy harvesting project

[pearldragon]

Hi Julian,

This week finally started up my Bedini SG again. Started out with some measurement with PSU at the input: Scope shots looked weird. Switched to using a battery at the input and the scope shots started to look as I remember them.

In the attachment you can find some of the scope shots. The scope shot with the PSU at the input had some resemblance with the 2^nd image of the 4 scope shots you showed in our zoom call, hence the post here.

Regards,
Rodolphe
Post nr 153 - Scope shots - 2023-12-01.pdf

[JulesP]

Hi Gary,

Yes, I have tried using a variety of sizes from 2.5, 5, 7,16, 40, and 110Ah with every build I have made and still never got the battery over about 13V.

My present system (V5) is a 4 winding + trigger coil and 4 generator/recovery coils and is giving the best CoPs around 0.9 (total energy out/total energy in) with both the 16Ah fluid motorcycle battery and the 40Ah car battery, but still never goes above about 12.9V.

However, it seems that reaching those voltages is not a prerequisite for getting OU, but of course, it will have long-term effects on the levels of sulphation.

I will be seeing what effect making the negative lead to the battery a direct connection and not going via a connection hub. I found that made a difference on the positive lead and where lumps of metal may interfere with the surface flow of energies.

I attach a charging profile from my BD1 setup (effectively an SSG) which is with just a single power winding and a trigger winding. This reached 1.15 but I have not yet done consistency tests.



It seems that the most important factor is keeping the current down (hence my earlier query regarding adjusting it) and with this trace was at 0.26A (I recall JB saying to keep the current at this sort of level). The thing is that with more windings the current goes up proportionately, as expected, but the charging effect does not increase by the same factor. This means that in fact, a two power winding coil will likely do better overall than a 4 winding one since the supply current is lower. In fact, with my V5 with its 4 windings, I get a better result if I disconnect one of the windings. So running with 3 coils instead of 4 reduces the supply significantly but does not drop the charging by the same amount. So far with this, I have reached 0.9, but there are a lot of alternative options to test yet.

I do have to wonder if my living on top of a huge peninsula of granite, in far west Cornwall, may be affecting the local ether! As you will recall, Rodolphe, who has replicated my V4 setup using a PWM, regularly gets around 15V with a 12Ah battery. So far we haven't made sense of this situation.

Regards,

Julian

[Gary Hammond]

Hi Julian,

Thanks Gary for all that. I tend to run in Generator or Common Earth mode so the max RPM for min current is what so have been doing. Still haven’t got a battery above about 13V though . . . . .

The battery size needs to be favorably matched to the size of the SSG. This means small batteries for a small machine with a single power winding on the main coil. I have a small SSG I started as a replication of Shawnee Baughman's little machine shown in the beginners handbook. I had trouble getting it to not blow the transistor, so changed a few things and got it working very well with a MJE3055 transistor, 2.75" diameter rotor, 1.5 x 1.75 coil, and 5.5 AH 12 volt batteries. It will easily push the charge battery over 15 volts in probably less than an hour. Here's a link to a video of it running on the battery swapper I made so you can see the relative size of the SSG in comparison to the batteries. https://www.youtube.com/watch?v=DE-CvurRW5U

Gary Hammond,

[JulesP]

Thanks Gary for all that. I tend to run in Generator or Common Earth mode so the max RPM for min current is what so have been doing. Still haven’t got a battery above about 13V though . . . . .

[Gary Hammond]

Hi Julian,

Hi Gary,

Another quick query if you please. I have been adjusting the 1k trigger pot for the fastest rotor spin and not necessarily the minimum current. Is that the preferred method? There is a point where the minimum current coexists with the highest rpm, and that is what I try to find. It is usually a little different (a few pot turns) for each battery type.

Julian

When running in radiant mode, it will usually start out at 2 or 3 pulses per magnet pass. In order to get to one pulse per magnet pass it may require reducing the base resistance pot in order to get it to "shift" from 3 to 2 and/or from 2 to 1 pulses which in turn increases base current. One it has "shifted" the RPM will increase to a given speed and then slowly increasing the pot resistance will cause a further increase in RPM and decrease in run current. There is a sweet spot where it runs at maximum RPM with the least current draw just before it drops back into adding an extra pulse back in. I try to run in this sweet spot, which changes over time as the run battery drops in voltage. If you adjust to slightly above this sweet spot it will run longer before shifting back to an extra pulse. Another trick is to add a "grain-of-wheat" bulb in series with the pot. This tends to cause the machine to self servo as the run voltage drops.

If you are running in common ground (generator) mode you will only get 1 pulse per magnet pass and can adjust for max RPM at least current draw. In this mode, as the charge battery increases in voltage the RPM will also increase and the current draw will decrease because the load is reduced and the voltage differential between the batteries is also reduced. In fact, the charge voltage can go way above the run voltage and produce overcharging of the receiving battery.

Gary Hammond,

[JulesP]

Hi Gary,

Another quick query if you please. I have been adjusting the 1k trigger pot for the fastest rotor spin and not necessarily the minimum current. Is that the preferred method? There is a point where the minimum current coexists with the highest rpm, and that is what I try to find. It is usually a little different (a few pot turns) for each battery type.

Julian

[JulesP]

Hi Gary ,

Yes, I have often had a 'poor/dirty contacts' notification during CBA discharges, that gave spikey, rough traces, arising from poor contacts in the pigtail connectors. One of the first things I did was solder the input cables directly to those metal prongs coming off the CBA board.

I think what I need to do is use the calibration method they gave me to measure the IR with various battery types at a specific C rate to find out what has the lowest value. I would also have expected that fluid-filled batteries would have the lowest value but I guess plate thickness must also come into play as well.

I would also expect that rejuvenating AGMs would be more difficult as the paste used is much less mobile than fluid electrolyte so ‘rehabilitating’ the Lead Sulphate is much more difficult.

I wish I was able to ‘top up’ my batteries! Until such time as that happens my CoP method will have to continue to use an ‘up and down’ method - charging from a measured voltage point at around 80% charge and then discharging back down to the same voltage (or near enough with some interpolation). At least it’s a consistent method for comparisons.

Julian

[Gary Hammond]

Hi Julian,

However, I have just heard back from the battery support and they say that the lowest IR is with the AGMs as they have thinner plates. Or, if I must have a wet battery, then choose one with the highest CCA. So it seems it might be a choice between having the lowest IR and being able to top up?

That's interesting. I just assumed that the flooded ones would have the lowest IR because there is nothing between the plates except the electrolyte. My assumptions are not always accurate.

When it comes to measuring IR, the CBA does it with the enhanced software that I have but it needs to be calibrated since the values I’m reading include the cables, etc. Here is what support says about how to do that:

“Run a test, the higher the current the better. Write down the voltage at the battery, the voltage on the screen and the current. Then use TOOLS > CALIBRATE CABLE to enter that information. The software will calculate the resistance and use that in future voltage calculations for the screen.”

Yeah, I forgot about the voltage drop in the cables and connections, so I went back and corrected the procedure I posted. This can be a significant loss. In fact my CBA had enough loss in the connectors between the short sections of cable that go to the CBA and the longer sections that go to the battery, that it was causing irregularities to be displayed on the discharge curve. I at first thought something bad was happening in the battery, but using a voltmeter directly across the battery discovered it had to be the connectors and not the battery itself. I removed the connectors and spliced the cables back together with a soldered connection. I also removed the connectors from the cables inside the CBA and soldered them directly to the PC board. End of problem!

I've not had any problem being able to "top up" the AGM batteries. Rather the only type I've had trouble "topping up" are the 105 AH deep cycle ones as they are too large for my machine. I'm old school in that I still prefer the flooded starter batteries. I've been able to rejuvenate several of them while I've never been able to rejuvenate the AGM type.

Gary Hammond,

[JulesP]

Hi Gary,

I have had a comprehensive look at batteries from a wide variety of manufacturers and almost all of them have a CCA/Ah ratio of around 10 or even less, implying a moderate to high internal resistance (accepting that for a lead acid battery they should be in the 10-50mOhm range when new).

However, Yuasa makes a range of wet motorcycle batteries, and where these have a better ratio, some around 12.5. However, in some of the listed specs the CCA value quoted is significantly higher than on the battery itself, so I'm seeking clarification.

So not only are these the best ratios I can find anywhere, with any battery type, but it can be topped up, so I reckon one of this type would be a good buy.

If you run through the list on this link: https://www.tayna.co.uk/Yuasa-YuMicr...ycle-Batteries you can see the Ah and CCA listed, which is helpful.

With two batteries with a similar 'good' CCA/Ah ratio, I assume the larger Ah one would be preferable.

However, I have just heard back from the battery support and they say that the lowest IR is with the AGMs as they have thinner plates. Or, if I must have a wet battery, then choose one with the highest CCA. So it seems it might be a choice between having the lowest IR and being able to top up?

When it comes to measuring IR, the CBA does it with the enhanced software that I have but it needs to be calibrated since the values I’m reading include the cables, etc. Here is what support says about how to do that:

“Run a test, the higher the current the better. Write down the voltage at the battery, the voltage on the screen and the current. Then use TOOLS > CALIBRATE CABLE to enter that information. The software will calculate the resistance and use that in future voltage calculations for the screen.”

I have yet to do this but I’m hoping it will be the most accurate and simplest way to get that value.

Julian

[Gary Hammond]

Hi Julian, F

Well, I've been looking at more battery specs and claims since we started down this rabbit hole. LOL I don't know if the battery manufacturers are trying to muddy the water with all the various specification terms or I'm just not smart enough to figure it all out!

Looked at my 105 AH deep cycle marine batteries a minute ago and discovered they have a label declaring a CCA rating of 550 CCA. That's only a 5.2/1 ratio of CCA/AH. My SSG would charge them very slowly to a max of 13.8 volts as best I can recall. They did, however, work OK in the 4 battery manual swapper circuit I made taking about 20 minutes to regain their starting voltage when in the charge position. They would keep repeating this reaching the same charge voltage in 20 minutes each cycle. I did this for up to 6 hours. At that time I got tired of baby sitting and manually switching them. I suspect they would have done this indefinitely if they were automatically switched. They were working in the 12.4 to 12.8 volt range which eventually caused sulfation due to under charging. I concluded that these batteries were too large and of the wrong type for what I was trying to achieve.

Then after searching for a while I found an old spec sheet for the Interstate batteries I used to sell back in the 1990s. It had a footnote that said to estimate the 20-hour capacity for any battery to multiply the reserve capacity (RC) rating by 6/10. (The RC is the number of minutes of 25 amp output at 80⁰F.) They had 3 different U1 style batteries back then each with a different set of ratings and number of plates. The middle one had 48 plates and was rated at 230CCA and 30 minutes RC. So multiplying the RC by 6/10 =.6x30=18AH. And dividing the CCA of 230 by 20 =230/20=11.5 AH. This size battery would usually show 11 to 13 AH actual capacity on the CBA analyzer when discharged at the C20 rate. The CBA analyzer gives the actual rating and not an estimate.

And after thinking about it for awhile, I concluded that the CBA could also be used to find the internal resistance at any discharge rate. You need to start with a full charged battery and hook it up to the CBA and measure the voltage at the battery before starting the discharge at the C20 or whichever rate you chose. Then when the discharge is started there will be a dip in voltage with a partial recovery after a few minutes which will then remain steady for awhile. If you then subtract this steady state voltage, measured at the battery, from the fully charged voltage you will have the voltage drop across the battery under load. Divide this voltage drop by the current draw chosen and shown on the computer to find the actual internal resistance of the battery for that rate. (R=V/I) Taking all voltage measurements at the battery you eliminate reading any voltage drop that occurs in the connecting cables and points of connection.

Finding the actual IR at any particular C rate of discharge is probably the most reliable way to compare batteries and how well they will respond to radiant/pulse charging.

Gary Hammond,

[JulesP]

Ok thanks, the hunt is on.

[Gary Hammond]

Hi Julian,

Hi Gary,

I suppose fluid-filled but tamper-proof (sealed) would be ok, so long as it doesn't need topping up through loss of water over time.

Would you say then that the CCA/Ah value is the most indicative of low IR and more important than the Ah capacity - so best if I compare a range of batteries to find a ratio of at least 20A/Ah, even if it results in a 40Ah or larger battery?

Julian

Most car starter batteries I've seen in the US for the past 20 years don't give a reliable AH rating, only the CCA rating. Some dual purpose marine batteries still give both ratings. But to answer your question, the 20 to 1 ratio of CCA to AH would be a pretty reliable guide.

The battery link you posted (post # 138) is about the same physical size as our U1L lawn and garden batteries. I used to have a 2006 Ford Expedition with a 4.6L v8 engine. Here's a link to the flooded batteries still available for it. Notice that only the CCA ratings are given. Most of my vehicles use batteries near this size range, and when I replace them I keep the old ones to use with the SSG. https://www.interstatebatteries.com/...explorer-v846l And here's a link to the U1 batteries available locally. https://www.farmking.com/category/di...tegory?id=3042

Some of our flooded maintenance-free batteries can be opened up to add water, but the AGM ones are usually sealed.

Gary Hammond,

PS : I see that the Interstate battery link shows 7 batteries available for the vehicle listed. 5 of them are flooded and give no AH rating. But the last 2 listed are AGM and DO give an AH rating. These figure out close to a 11.8/1 ratio for one battery and 11/1 for the other.

[JulesP]

Hi Gary,

I suppose fluid-filled but tamper-proof (sealed) would be ok, so long as it doesn't need topping up through loss of water over time.

Would you say then that the CCA/Ah value is the most indicative of low IR and more important than the Ah capacity - so best if I compare a range of batteries to find a ratio of at least 20A/Ah, even if it results in a 40Ah or larger battery?

Julian

[Gary Hammond]

Hi Julian,

So I should be aiming for a fluid-filled battery or are the AGMs or SLAs equally as good? I have a 17Ah AGM mobility battery, that I have done many tests on, but its IR is not as low as I would like.

I didn't realize it would be difficult to find flooded lead acid starter batteries in the UK. We still have them readily available in the US.

The battery in the link you provided is only a 300 CCA which is pretty low for also being rated at 35AH. Our U1 and U1L lawn tractor batteries are rated from 270 to 335 CCA and will only deliver from 11 to 13 AH when tested on the CBA analyzer. These are what I started with and also what I showed on my home page that gave me the 1.25 COP.

I've also gotten nearly as good results with 12AH AGMs but I prefer the flooded type because I think they have the lowest internal resistance. The deep cycle batteries will work, but I get better results with flooded starter batteries on my particular machine.

Gary Hammond,

[JulesP]

Hi Gary,

Clearly, I was given poor advice by another who was adamant that the larger deep-cycle batteries would give the best results.

So I should be aiming for a fluid-filled battery or are the AGMs or SLAs equally as good? I have a 17Ah AGM mobility battery, that I have done many tests on, but its IR is not as low as I would like.

Here is a typical 35Ah sealed one:
https://www.eurocarparts.com/p/lion-...AOVjBdo1wlPhF3 w-Do3ey2GriojrIEx_XdUe0TD9DN40BPMlTmn7N1iiersaAmd3EA Lw_wcB

It's not easy to find fluid-filled ones these days, except perhaps in small motorcycle batteries for example.

Perhaps my 110Ah battery can serve as a REAC, a 3rd battery, although many say that depleted and sulfated batteries work best here.

Decision, decisions

Julian