Using BadBoy charger for 30S battery

OK. Lets see if I can lay out in detail my thoughts and viewer input requirements.

I am nearly finished building a portable band type sawmill. Logs will be softer type wood and only up to 15" diameter at breast height. Logs are from 7' to 15' long.
Our previously built sawmill had a 24HP gasoline engine and could pretty much charge through similar type logs. The sawing technique will be, slow feed of the blade depending on how the cutting goes. Until I get to use the mill, I have NO way of knowing how fast, how hard the blade will be working. I DO know the 8HP Honda gasoline engine I have will be slower than torture, but, would eventually get the job done painfully slow.

I have seen sawmills of this type powered by 15HP gasoline engines. I am NOT looking for big production from this mill. I have a small plantation of trees that we planted and my wife wants to add on to the end of our small house. I need 2" X 4" and 2" X 5" and a bunch on 1" X 3-4" for purlins to attach the metal roof panels to.

Now, first comment I received from another badboy thread, was about the battery voltage. I have 1 or possibly 2 banks of 30S Chevy Volt modules. My TOP voltage is not to be over 4.1V per cell which would be 123V. I already know that 111V is about nominal for the battery rating, BUT, I do not want to overcharge these cells. The motor will be under load as long as the blade is cutting, then, no load as the lumber is removed from the mill and the sawhead is gigged back to the original starting point for the next cut. From vast experience, I can imagine the load being applied for POSSIBLY 1-1.5 minutes per pass down the log. As the log gets thinner, the load will decrease some, so, constantly reducing load for up to half the volume of the logs.

I can be assured that the cutting of the wood would not be as severe on the battery/controller, compared to how John in CR takes off in traffic, at a hefty load and up hilly terrain and at 72V nominal of his 20S Chevy Volt battery pack. I have an older Curtis 144V 300Amp controller to use and a possibility of either a GM altermotor that was designed for 130V 3 phase, or an AC20 3 phase motor that I can't remember the name of, that this stuff was used to power a small electric car on the highway. Either motor is capable of more that the 15 HP gasoline sawmills down here.

In John's thread about badboy charging, I believe the sensus is that 117V AC from a house outlet will actually be around 164V or so after the bridge rectifier. This equates to around a 25% increase above the house 117V output. Solar Panels, for example, have about the same 25% more voltage open circuit same as the 117V open circuit from the house AC. My questions are, will the 164 peak DC voltage be detrimental to the cells or battery, per se. Also, what about the current rating available through the bridge rectifier ? Of course, fuses or circuit breaker would be in place for safety reasons. I have a 12/2 Romex, solid wire coil long enough to reach the log site and that would be approximately 80-100 feet long. I have enough to double up that 12/2 if need be.

If any more info is needed, kindly state so and I will try to oblige. Thanks for reading through all this info, Harold

Sorry I still don't follow much.

Start at the batteries, and voltages

30S means top voltage charging in theory 126V, in practice for longevity 121-123V

Midpoint **at rest** nominal 108-111V

LVC depends on how much current pulls down the voltage, but for longevity you want to see a bounceback to at least 3.3V at rest, 3.5V would be better.

So far so good? ask if any questions about the above.

Now let's look at where the energy input is coming from to support the controller+motor loads.

In theory 800W per HP, optimistic but as a start, same with 15HP required call it 12kW.

Let's say a session is two hours of actual cutting wood at that rate, so 24kWh of energy.

Ignoring the Ah capacity of the "buffering" storage battery bank,

where is the input energy coming from each day?

Is mains or genset AC power available? At what amps rate?

Or do you intend to put in a solar panel installation + solar controllers to recharge the bank?

About 7kW of panels might be enough to supply 24kWh of actual usable stored energy per day, but only when insolation conditions are near perfect.

How can you not understand what I wrote ? I specifically said the log area is close to within 80-100 feet of the house and I have possibly 2 runs of 12G solid romex wire to charge the battery. I have said, twice that the AC voltage would be 117 from the house/grid. Obviously, a max of 20 Amp supply through that 117V source ?

The solar panel information was simply to compare the % amount of voltage of either charging source over the voltage of whatever battery is being charged ?

just seeking to clarify, not even sure what your question is

but never mind carry on

My guess would be that on a continuous basis the mill is only going to be needing 4-5kw at the most, probably more like 2-3kw average (while actually sawing, not moving logs and cut planks around which I guess is the majority of the time spent), and of course when it bogs down a bit it will draw more. At 120V pack and after voltage sag and losses in round terms call it 40-50A If it's the V1 Volt modules then you've got about 40ah of capacity or the V2's 45ah+ usable. That gives a minimum of about an hour of run time actually cutting, though I think more like 2hrs, so I question the need for high power charging while running the mill.

Comparing HP ratings of gas to electric doesn't work very well. The smoke belcher is rated a max output at a specific narrow band of rpm and it take longer to respond to changes in load, which is automatic with electric. I'd always heard that 3 to 1 is a good comparison ratio, ie 1hp electric = 3hp gas. On a mill, since the rpm is mostly constant then a 2 to 1 ratio is probably good as long as you don't have to much in gearing losses to get the right rpm at the blade.

If you're going with a 110V AC line, let's hope the guys where right about actual voltage coming out of the rectifier. That would mean the 117V we measure at the wall is RMS, which will convert to the same voltage RMS DC, so unless the battery is pretty low it's only going to be charging the battery during the voltage peaks of the waveform...small pulses and the battery will be a buffer and absorb the spikes, so it will never go to the 160V-170V the guys were telling me.

My 2 concerns are:
1. Is the rectified voltage from the 110VAC line actually going to be high enough to supply enough current to charge the battery during operation.
2. Safety- You need some way to make sure the bad boy charger gets turned off in the event of an accident. The last thing you need is battery fire on top of a saw mill accident, because unlike the mill that charger is running silently and has no cutoff.

I need to dig out the rectifier and test the voltage. Busier than a 3 peckered Goat the last few weeks.

I would install a 10-12 Amp circuit breaker or fuse between the house supply and the charging device. The item in the link I sent in the UPDATED PM might be all we both need for charging. In my case, I may need a boost circuit to raise the supply voltage IF the converted AC to DC voltage is not what we are being told. I can't say until I find the bridge rectifier I have. It is a 90A device.

I'm not looking to keep the battery close to full charge, just to prevent too close to cell voltage under 3.5 SOC. This is why I can also parallel another 30S with the first, and charge them both after the sawing session(s) is done.

Harold in CR said:

I need to dig out the rectifier and test the voltage. Busier than a 3 peckered Goat the last few weeks.

I would install a 10-12 Amp circuit breaker or fuse between the house supply and the charging device. The item in the link I sent in the UPDATED PM might be all we both need for charging. In my case, I may need a boost circuit to raise the supply voltage IF the converted AC to DC voltage is not what we are being told. I can't say until I find the bridge rectifier I have. It is a 90A device.

I'm not looking to keep the battery close to full charge, just to prevent too close to cell voltage under 3.5 SOC. This is why I can also parallel another 30S with the first, and charge them both after the sawing session(s) is done.

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With 2 batteries you may not even need charging until after a good day's use. Get the wind turbine flying again, so you can charge with it, otherwise you'll feel that extra charging in your electric bill if it's many days of work. Too bad my teens have zero interest in actual work, otherwise I could send some help that would allow them to learn the gratification of outdoor manual labor work.

I've still got over 20 of those Nissan Leaf modules. Maybe we can work a deal on 15 of them.

I've been interested in those modules. It's just difficult to get them from the Bus stop up to the house. Would be great if you delivered. :lol: :lol:

If you don't understand how a badboy charger works, you shouldn't be using one. I'll give you both a hint - you don't.

Without anything to limit current, you will blow your fuse immediately. The peaks of the AC waveform will put 1000s of amps into your battery.

Thanks for the encouragement. We have made these threads trying to get some input from those that DO know about the Bad Boy charging. Would you have some info to steer us into a positive direction, HMmmm ?

I am working on the current, just haven't posted all the info I have been gathering up.

John, if you could get the boys up here, without their cellphones, maybe I could generate some interest in them. I'm afraid though, after 2 days with me, they would suffer from boredom and become suicidal.

Harold in CR said:

In John's thread about badboy charging, I believe the sensus is that 117V AC from a house outlet will actually be around 164V or so after the bridge rectifier.

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Right. Specifically between about 155 and 185 volts.

Solar Panels, for example, have about the same 25% more voltage open circuit same as the 117V open circuit from the house AC.

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Well, completely different mechanism, but OK.

My questions are, will the 164 peak DC voltage be detrimental to the cells or battery, per se.

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Yes. 5.5VPC will quickly destroy the cells.

Also, what about the current rating available through the bridge rectifier ?

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A well designed (i.e. low resistance) system would give you hundreds of amps at peak voltage. So to make it work at all you'd need to do a poorly designed (i.e. high resistance) system. A cheesy way to do this is with longer and longer extension cords until you get the resistance you need to not blow any breakers. But they will get very hot - so you'll have some thermal issues to deal with. For example, if you coil up the extension cords, they will melt and you'll have a fire.

Overall direct charging is a very bad idea. Segment the pack and charge each segment through an isolated AC/DC supply.

Segment the pack and charge each segment through an isolated AC/DC supply.

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This idea I have used for my 83V (74V nom.) , but it creates some manipulation to reach a very close balance voltage among segments. The Chevy Volt battery carries a nearly perfect balance of it's own, (.01-.015) usually. I am following along the Lee Hart conversation ( I believe Don Bonn was the author)? and they recommend transformers or a Variac type for part of the circuit. I have trouble understanding electronic circuits, so, it takes a while to sink in.

Being told we don't know what we are doing doesn't help. What about all the people that ARE doing thi s ? They didn't know anything in the beginning, either. Explaining how things work and how TO do it, used to be what this place was all about.

Could you please help with the cross pollination and list links for those conversations?

Disclaimer: don't do this. This is not an instruction. This is a thought experiment only.

It is done using a long cable (which acts as a resistor) to reduce the current (and to a limited extent, voltage) seen at the pack. It's as simple as that. But that simplicity is what makes it so difficult to apply in practice.

It's a very rough way of charging. It's brutal on the cells. You need to be very on the ball. You need to know SOC at the start, and you need to work your way up. Start with shorter charge times, until you build the confidence (and data) that you are charging within the limits of the cells. You need to be there monitoring what's going on at all times. With a fire extinguisher (for the surrounding items, not the battery, you won't be able to stop that sucker burning). And you need to disconnect at exactly the right point in time.

You need to calculate the resistance of the cable, based on how many amps you want to push, and the voltage difference between the pack and the supply.

R= (Vsupp-Vbatt)/I
(For the nit pickers, I'm purposefully ignoring cell IR.)

You need to make sure the cells can handle the higher voltage they'll see. Can they? You need to make sure the cable can radiate the heat generated. Could be kW range. However you plan on managing balance, that's something else you'll need to solve.

And your dealing with rectified AC, with no filtering. Ouch. That's hard on the cells.

Oh, and non-isolated too. Double ouch. That's hard on the heart.

This is why people are telling you not to do it. In your scenario, there are so many variables and undesirable conditions that can cause catastrophic failure. Or just poor performance/cell life. Unknown soc. Variability in the mains supply voltage, etc etc etc...

Also, what they're saying is, this shit is so rudimentary, that if you can't figure this stuff out from basic principles, you don't know enough to keep yourself out of trouble. No offence intended. Just being blunt.

We used to do it from a car battery into small packs of A123 cells. But those cells were so fricken robust. You could over volt them and pump so many amps, and they didn't care. And a car battery is a known stable power source. And the power levels were an order of magnitude lower than you're talking about. And we had a consistent/known SOC at start of charging every time (speed controller LVC). Much more controlled situation. Much lower risk.

What your talking about is extremely risky. It's not that it can't be done. But it just probably shouldn't be done.

And for what purpose?

Stellar quality high power ex-telecom PSUs (good boy rectifiers) go for cheap as chips on eBay

The biking threads' purpose is not carting one around, but that's not an issue in a stationary context.

john61ct said:

And for what purpose?

Stellar quality high power ex-telecom PSUs (good boy rectifiers) go for cheap as chips on eBay

The biking threads' purpose is not carting one around, but that's not an issue in a stationary context.

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Harold asked a question. You obviously don't have the ability to read and understand what he was asking (although it was plain to see for everyone else).

Nobody cares about your unrelated opinions. People have their own reasons. None of your business.

I was looking at the Bonn badboy charger here http://www.evalbum.com/tech/bonn_charger.html, and it seems interesting and brings up something that hasn't been before, and that is using an inductor to help limit current and or voltage. I have a meter for measuring inductance, and I have some big subwoofer magnets that I rounded the corners on for winding torroidal coils that I wound with 10 gauge cable. I had three that I put in series with a very low inductance motor so it wouldn't make the controller run so hot. With a torroidal coil wound with heavy insulated wire, it should be cheap and easy to make, and could be put in a bucket of water to make sure it doesn't cook.

What I don't have a clue about is what kind of inductance value would be needed.

serious_sam said:

Nobody cares about your unrelated opinions. People have their own reasons. None of your business.

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Odd that opinions are unwelcome when they are asked for.

Maybe I should say why I am/was interested in this charging system. Many years ago, I bought a belt drive 4KW ?120/240 volt AC alternator and attached it to a 10 to 1 gearbox that was attached to a 15 foot diameter propeller that I carved and placed this on a 60' tower that I built. I ran 2 hot legs and a neutral to a shed with PB battery 2V cells and attached a 36V lester golf car charger to one 120 line and a large physical sized diode ? and a relay that was turned on at a specific voltage and then to a large sized 14" diameter ? variac. Thing was probably 30 pounds.

I bought 250' of 4 ga. welding cable that was probably way over kill, that ran down the tower and to the battery shed.

As the wind turbine started turning nothing happened, then at a little stronger wind, the alternator would excite itself and a small lamp in the battery shed would start to glow. As the wind picked up the Lester charger would start buzzing and put out current as shown on the case mounted gauge. The variac would also show current on another amp gauge. I could turn the know on top of the variac and increase, SOMEWHAT, the current output.

Some days the wind was very light but I could still put small charging to the 32V battery bank. As the wind picked up I would have to turn down the variac to keep the 120V lines somewhat in balance. In a good strong wind, I could watch the amp gauges go as high as 30A surges on each leg. The blades were governed by a device I built from information regarding how Marcellas Jacobs designed his turbine governors in his wind turbine factory.

We lived off grid for over 5 years with this system until the night the tornado caused the blades to separate from the turbine. We also had a gasoline generator for backup charging using the same set up, by being attached to the 3 welding cables

This system worked surprising well, SO, I have been drawn to this bad boy system because of the success I had. Probably the controlled output of either generator was a contributing factor.

Any thoughts as how I got away without boiling the cells compared to what the Bad Boy system would do, I would like to hear practical opinions. I'm looking for education, not doubting the advice already given as to the caution by several people. Thank you to those that responded to prevent major problems.

That system was pretty much the opposite, though if you still has that big variac it would be just what the doctor ordered. That old system you had a real battery charger that turned on when your intermittent electrical supply put out enough power to turn the charger on. Now you're talking about an unlimited stable AC power supply to charge a big battery pack without a real charger. You know how to turn it into DC, and know how dangerous it is and that manual supervision and cutoff is required. The battery will absorb the lumpy voltage, so it's just current that you need to monitor and limit. A run capacitor is required on the AC side, and be sure to solder in a sufficiently sized bleed down resistor to avoid shock hazard even when it's off.

A heavy duty dimmer can limit the current and so can inductors. Though energy wasteful for as cheap as $2-3 a resistance coil for an on-demand showerhead water heater so commonly used down here could limit current. In a big bucket of water with a continuous slow flow of fresh water to keep it cooler and not boil away. Going that route, I think it would be safer and maybe more efficient too to have that on one of the DC legs well away and downhill of everything...not sure if positive or negative would be better or even make a difference. That's what I used to burn off all the energy left in that fire damaged pack I had.

John, you are correct in that I am aware of everything you just posted, including changing out the resistive wire in these suicide shower heads, before I went Solar water heating.I'm just hoping some the educated guys come back in and educate me/us. I am heeding all their advice, just want to be educated.