On Thu, 20 Dec 2012 11:56:13 -0600, Tim Wescott wrote:> On Wed, 19 Dec 2012 18:52:53 -0800, Yzordderrex wrote: > >> Greetings, >> >> I have a small diesel engine spinning a DC generator. I need a control >> chip that will take approximately 60v that generator puts out and >> charge the lead acid bank. Bank is 16 27M Die Hard deep cycle wired in >> 4x4 configuration. It is my intention to control diesel speed to give >> me a little headroom for charging the battery pack. I will use >> external mosfets to get about 50A of charging current, so just looking >> for the control chip. >> >> Any ideas would be helpful. > > To answer your actual question: just about anything that calls itself a > PWM controller can be used. No matter what you'll need to build the > gate driver circuit and final switching circuit yourself, and that's > where the challenge is. I'm almost tempted to say that if you have to > ask you shouldn't do it -- but instead I'll just say that you should > plan on burning up a few boards... > > The LM3524 and TL494 are classics. Someone suggested a microprocessor > with a PWM output -- I'd be very tempted to go that route, myself. > > Do keep in mind that for charging lead-acid batteries you want to > implement a current-limited constant-voltage supply -- lead-acid > batteries do _not_ like being charged at too high a voltage. The ideal > charger would monitor the battery temperature and adjust that final > charge voltage, to boot. > > Also keep in mind that you may want to implement some balancing within > your series string: because you don't want to bring the battery voltage > too high, you want to avoid a circumstance where you have some parallel > banks at low voltage, and one or more at a too-high voltage. (I don't > know where balancing becomes important with lead-acid batteries, but I'm > pretty sure that when you have 24 cells in a string it means something). > > I'd be tempted to charge the batteries as four series strings, with four > individual chargers (with balancing). This should cost less than 4x as > much, because your switches and inductors will get cheaper as their > current capability goes down. What you do is up to you, of course.And -- is there a reason why you don't want to just hold the generator at the right speed for charging? And -- is it a wound-field motor, and if so why can't you use that for voltage regulation? -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Re: Need PWM controller for current source to charge 48v lead acid.
Started by ●December 19, 2012
Reply by ●December 20, 20122012-12-20
Reply by ●December 20, 20122012-12-20
On Thu, 20 Dec 2012 10:47:32 -0800 (PST), linnix <me@linnix.info-for.us> wrote:>On Thursday, December 20, 2012 7:39:33 AM UTC-8, Michael Terrell wrote: >> krw@att.bizzz wrote: >> >> > >> >> > Michael A. Terrell wrote: >> >> > > >> >> > >Sjouke Burry wrote: >> >> > >> >> >> > >> Why not regulate the generator to output the correct charge voltage? >> >> > >> No conversion losses, only slight modifications to the >> >> > >> generator control hardware. >> >> > > >> >> > > Or a switching regulator, so the engine can run at its most efficient >> >> > >speed? >> >> > >> >> > Gee, that's a GREAT idea. Maybe you should tell the car manufacturers >> >> > about that. ;-) >> >> >> >> >> >> Do you think the UAW would let them do anything to improve a vehicle >> >> if they can't pad the production line with more of their people? >> >> For instance: Back in the '70s Delco designed a car radio that could be >> >> installed from the front of the dash with no tools. The UAW threw a >> >> hissy fit, because it would cost a few union jobs. >> > >But can it be removed with no tools? If so, I would throw a fit as well. It would be open invitation for car thieves and broken windows.Rather than have the thief take a crowbar to your dash?
Reply by ●December 20, 20122012-12-20
On Thu, 20 Dec 2012 14:24:32 -0600, Tim Wescott wrote:> On Thu, 20 Dec 2012 11:56:13 -0600, Tim Wescott wrote: > >> On Wed, 19 Dec 2012 18:52:53 -0800, Yzordderrex wrote: >> >>> Greetings, >>> >>> I have a small diesel engine spinning a DC generator. I need a >>> control chip that will take approximately 60v that generator puts out >>> and charge the lead acid bank. Bank is 16 27M Die Hard deep cycle >>> wired in 4x4 configuration. It is my intention to control diesel >>> speed to give me a little headroom for charging the battery pack. I >>> will use external mosfets to get about 50A of charging current, so >>> just looking for the control chip. >>> >>> Any ideas would be helpful. >> >> To answer your actual question: just about anything that calls itself a >> PWM controller can be used. No matter what you'll need to build the >> gate driver circuit and final switching circuit yourself, and that's >> where the challenge is. I'm almost tempted to say that if you have to >> ask you shouldn't do it -- but instead I'll just say that you should >> plan on burning up a few boards... >> >> The LM3524 and TL494 are classics. Someone suggested a microprocessor >> with a PWM output -- I'd be very tempted to go that route, myself. >> >> Do keep in mind that for charging lead-acid batteries you want to >> implement a current-limited constant-voltage supply -- lead-acid >> batteries do _not_ like being charged at too high a voltage. The ideal >> charger would monitor the battery temperature and adjust that final >> charge voltage, to boot. >> >> Also keep in mind that you may want to implement some balancing within >> your series string: because you don't want to bring the battery voltage >> too high, you want to avoid a circumstance where you have some parallel >> banks at low voltage, and one or more at a too-high voltage. (I don't >> know where balancing becomes important with lead-acid batteries, but >> I'm pretty sure that when you have 24 cells in a string it means >> something). >> >> I'd be tempted to charge the batteries as four series strings, with >> four individual chargers (with balancing). This should cost less than >> 4x as much, because your switches and inductors will get cheaper as >> their current capability goes down. What you do is up to you, of >> course. > > And -- is there a reason why you don't want to just hold the generator > at the right speed for charging? > > And -- is it a wound-field motor, and if so why can't you use that for > voltage regulation?Wound field _generator_. Sorry. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●December 20, 20122012-12-20
On 12/20/2012 7:57 AM, Nico Coesel wrote:> mike<ham789@netzero.net> wrote: > >> On 12/19/2012 6:52 PM, Yzordderrex wrote: >>> Greetings, >>> >>> I have a small diesel engine spinning a DC generator. I need a control chip that will take approximately 60v >> >> that generator puts out and charge the lead acid bank. Bank is 16 27M >> Die Hard deep cycle wired in 4x4 configuration. >> >> It is my intention to control diesel speed to give me a little headroom >> for charging the battery pack. > > I'd use a microcontroller. That puts everything under one software > controlled loop. In that case it's also easy to have the diesel start > and stop automatically. > >> I will use external mosfets to get about 50A of charging current, so >> just looking for the control chip. >>> >>> Any ideas would be helpful. >>> >>> thanks, >>> Bob >>> N9NEO >> What's the fully charged voltage of your battery? >> Looks like you have barely enough voltage. >> Crank the engine speed down 5%. And regulate it by current >> and voltage. Probably less lossy than the best switcher >> you can build that will run off that little headroom. >> High technology is not always the best answer. >> >> You want to run the engine at maximum efficiency whatever >> the charge level. That may not be the same speed over >> the whole charging range. > > Running a diesel at maximum effiency is at near full power (or at > least near maximum torque).Up to here, that statement agrees with my "understanding". So a switcher if most likely to provide> the best fuel economy.The conclusion is the part I contest. I define efficiency as the ratio of energy imparted to the battery divided by the gallons of diesel fuel used. The switcher reduces the generator current which reduces the torque. It makes little sense to run at higher speed at reduced torque and also lose 10% in the switcher. This all depends on the facts presented...60V and 4 batteries in series. IF there are other unstated loads or considerations or...or... the optimal solution might be completely different. Best you can do is solve the problem as disclosed. I've given the OP the benefit of the doubt and assumed they know that a 48V lead acid battery doesn't charge at 48V.>
Reply by ●December 20, 20122012-12-20
On 20/12/2012 02:52, Yzordderrex wrote:> Greetings, > > I have a small diesel engine spinning a DC generator. I need a > control chip that will take approximately 60v that generator puts out > and charge the lead acid bank. Bank is 16 27M Die Hard deep cycle > wired in 4x4 configuration. It is my intention to control diesel > speed to give me a little headroom for charging the battery pack. I > will use external mosfets to get about 50A of charging current, so > just looking for the control chip. > > Any ideas would be helpful. > > thanks, Bob N9NEO >Can you be more specific about the DC generator? To me a DC generator has a commutated armature and a stationery field winding. I would have thought you would have meant an alternator, with rectifying diodes and a rotating field winding with current supplied by slip rings. Either way, you probably have access to the field winding, and so able to control final voltage by varying field excitation? Or do you really mean controlling engine speed by electromechanical means (stepper motor / solenoid etc), to limit charging voltage to 59V depending on your desired charging regime? -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●December 20, 20122012-12-20
On Wednesday, December 19, 2012 9:52:53 PM UTC-5, Yzordderrex wrote:> Greetings, >=20 >=20 >=20 > I have a small diesel engine spinning a DC generator. I need a control c=hip that will take approximately 60v that generator puts out and charge the= lead acid bank. Bank is 16 27M Die Hard deep cycle wired in 4x4 configura= tion. It is my intention to control diesel speed to give me a little headr= oom for charging the battery pack. I will use external mosfets to get abou= t 50A of charging current, so just looking for the control chip.>=20 >=20 >=20 > Any ideas would be helpful. >=20 >=20 >=20 > thanks, >=20 > Bob >=20 > N9NEOI didn't want to get into too many details here - but you guys (being engin= eers) leave me no choice:-) Thanks for all the design input, but I'm really= all set. I'm just looking to do a 50 amp current source using a buck conv= erter. I've been designing power conversion gear since the 70's. I find t= he manufacturer search engines to be a little lacking, and Digikey not much= better. The generator I believe has permanent magnets on the stator with a wound ro= tor and slip rings. (They sell em on Ebay for 4 or 5 hundred bucks. People= use them as motors on motorcycles and lawn mowers and so forth.) I'm driv= ing it with a Chinese diesel that is rated for 6HP. I have all set up, jus= t have to buy the timing belt. I've geared it to run at the most efficient= speed. I will eventually charge 32 batteries when fully up and running. I am also doing 48vdc to 120vac converter/inverter, and PV array chargers. = All this is being done in my spare time as I am General Contractor for my = house that this is all going to power. Utility wanted $17k to string wires= to my house. Roof going on today and windows next week. Hopeful to be in= with some kind of electricity by the end of the year. Picked up 2kW worth= of panels and the state and fed is going to kick in $2400 in rebates. I am in-between jobs now so a little reluctant to call my usual TI or LT re= ps. I've actually referred to this newsgroup as my design team on numerous= occasions. I've been hanging around here for probably 10 years and gotten = a lot of good design advice. Thanks for all the design advice. Hope this tome has shed some light on p= roject. Tim was the clear winner with supplying part numbers. Tim has bee= n a very good ally over the years as well as John and some others. Thanks = to all for the input - I'll be sure to follow up with my design. =20 MERRY CHRISTMAS Bob N9NEO
Reply by ●December 20, 20122012-12-20
> > Alternator+rectifier types can be regulated by shorting their outputs, often > with an SCR. Shorting such a generator with PWM'd mosfets would be interesting. > > -- >John, I know this is true for some alternators, because most motorcycle charging systems work this way, a simple shunt regulator at the output. But I've always wondered about this. My assumption is that this can work only if the output Z is pretty high. In a sense the alternator is always loaded at it's maximum current to keep the output voltage down. The question is WHY would anybody design it this way. Seems very wasteful of power and operating the alternator at max current 100% of the time can't be good for the life of the windings, in fact burnt out alternators is a common problem on some bikes. So again, WHY are the designed this way? Mark
Reply by ●December 20, 20122012-12-20
On Thu, 20 Dec 2012 15:43:35 -0800 (PST), Mark <makolber@yahoo.com> wrote:> >> >> Alternator+rectifier types can be regulated by shorting their outputs, often >> with an SCR. Shorting such a generator with PWM'd mosfets would be interesting. >> >> -- >> > > >John, > >I know this is true for some alternators, because most motorcycle >charging systems work this way, a simple shunt regulator at the >output. But I've always wondered about this. My assumption is that >this can work only if the output Z is pretty high. In a sense the >alternator is always loaded at it's maximum current to keep the output >voltage down. The question is WHY would anybody design it this way. >Seems very wasteful of power and operating the alternator at max >current 100% of the time can't be good for the life of the windings, >in fact burnt out alternators is a common problem on some bikes. So >again, WHY are the designed this way? > >MarkCar/bike alternators are designed to be sort of constant-current devices, because that helps to drive the load over a wide range of RPMs. There is an air gap between the rotating field (wound or PM) and the stator windings, effectively a lot of leakage inductance. If you short it, the current is limited by the series inductance and it doesn't (or isn't supposed to) get all that hot. As speed goes up, the open-circuit voltage goes up, but the w*L impedance goes up too, so things sort of cancel. The reason the load dump voltage is so high in a car is because the open-circuit voltage of the alternator is maybe 60 volts, to charge a 12 volt battery. Anyhow, maybe the best regulator is a PWM'd mosfet short. The 50 amp switcher regulator inductors are free, namely the internal inductance of the alternator. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●December 20, 20122012-12-20
Michael A. Terrell wrote:><snip>> > Do you think the UAW would let them do anything to improve a vehicle > if they can't pad the production line with more of their people? > For instance: Back in the '70s Delco designed a car radio that could be > installed from the front of the dash with no tools. The UAW threw a > hissy fit, because it would cost a few union jobs. > > > At one time there were variable rate automatic transmissions which > did optimize the power curve but I haven't heard of one in decades. >Nissan offered a continuously variable transmission on the Murano. -- Les Cargill
Reply by ●December 20, 20122012-12-20
On Thu, 20 Dec 2012 10:39:33 -0500, "Michael A. Terrell" <mike.terrell@earthlink.net> wrote:> >krw@att.bizzz wrote: >> >> Michael A. Terrell wrote: >> > >> >Sjouke Burry wrote: >> >> >> >> Why not regulate the generator to output the correct charge voltage? >> >> No conversion losses, only slight modifications to the >> >> generator control hardware. >> > >> > Or a switching regulator, so the engine can run at its most efficient >> >speed? >> >> Gee, that's a GREAT idea. Maybe you should tell the car manufacturers >> about that. ;-) > > > Do you think the UAW would let them do anything to improve a vehicle >if they can't pad the production line with more of their people? >For instance: Back in the '70s Delco designed a car radio that could be >installed from the front of the dash with no tools. The UAW threw a >hissy fit, because it would cost a few union jobs. > >[snip] One of my more stressful moments was during a tour of a GM alternator manufacturing line in Anderson, IN (*) There were union members PAID to stand around and watch the robots make alternators, unaided by any human. The intriguing step was watching the robot balance an armature... spin it, magnetically watch its wobble... stop it exactly and drill away a small amount of metal to balance it... repeat once, then perfectly balanced. (*) Night spot of Indiana... sit around the fire-pit in the lobby of the Holiday Inn, and watch the snow fall ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
