Fieldlines.com || Make your electricity from scratch!

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products

Converting Honda EX350 from AC/DC to DC only
By Clifford, Section Homebrewed Electricity Posted on Fri Dec 02, 2005 at 07:28:52 AM MST
Dumping 350 watts into my batteries (note, I believe the EX350 and EX500 are virtually identical except for AC/DC vs AC ONLY)

I am now convinced that I will be better off running a small generator to dump into my battery bank and using a large inverter rather than running AC directly off of the generator...
Thus, if I use a "Chop Saw", for example, it may only use peak power for a matter of seconds which I should be able to pull out of my batteries. There would be no reason to have a 110V - 2KW generator running for a few hours to cover these short few second surges when a battery is made to do it.
Yes, I know that using a generator is cheating a bit, but my solar array isn't quite keeping up with my demand.
Anyway, so I've purchased a HONDA EX350 Generator along with a spare Stator Assembly. The Stator assembly is a bit oily... perhaps from a blown engine. Hopefully the Stator itself is ok.

According to the wiring diagram (free download from Honda), the DC section of the motor is running in star pattern.
Inspecting the stator...
the first 6 coils are wired together, and must be DC part of the generator.
the next 15 coils are wired together for the AC portion of the generator.
Total of 21 alternator coils plus 2 magneto coils (I think).
Note, the magnets each have dual polarity with a N pole at one end, and a S pole at the other end, giving the motor 3 phase output.
I am planning on separating the sets of coils and rewiring to give myself an All DC generator (going to my own rectifier).
I have to decide if I want to wire the alternator into 3 banks of 6 coils (3 phase-star). This will leave me 3 unused coils... what do I do with those?
The other option would be to wire it in 7 banks of 3 coils (3 phase-Delta configuration).
Assuming that I could get enough power out of the Delta config, I should be able to optimize the coils, and to use all of the coils..
Hmmm, further inspection shows that the short coil that I have circled as Magneto actually is marked as "SW" on the wiring diagram and goes to the inverter.
The Tall - fat coil (EXW) is part of the ignition system.
If I "abandon" some coils, how should they be wired? Solder leads together, or leave them open?
--------------------------
The next question that I am pondering is whether the thing could be rewired in the future to use points to switch the polarity on the coils and build an electric start mechanism into the generator.
That will have to be some future experimentation. But, in theory, if I added permanent magnet activated points (selenoid)... I could convert this into a self "starter".
---- Clifford -----
BTW... I think the Honda EX350 and EX500 generators are quite likely to be basically the same except that the EX350 has AC/DC operation and I believe that the EX500 has AC ONLY operation.

Converting Honda EX350 from AC/DC to DC only | 6 comments (6 topical)

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#1)
by maker of toys on Fri Dec 02, 2005 at 04:02:17 AM MST

first things first:

those pictures are too large. Pretty, well detailed, well focused and lighted, but too bloody large.

on to your question: from a 10 minute search, I believe the ex500 is a EU/AUS only, 240 volt machine. the ex350 looks like it's running on honda's 'all angles' 34cc 4 stroke engine; quite a nice piece of kit for what it was designed for; occasional use in weedwhackers, cultivators and dewatering pumps and such. the ex500 is probably using the big sister to that engine; the family comes in 1.5 and 2.5 hp trim, IIRC.

even though honda put one in a genset, I would question that little engine's durability if it were asked to run for a significant number of hours in a week/month/year, instead of occasional use like yardwork, camping or standby power. Your milage may vary.

So then we come to the rewiring, which I'll leave to others to guide you through; I'm not sufficiently practiced to carry the job through without experimentation, and so I wouldn't want to give what would probably be bad advice.

I'll just say that if I were doing it, I think I'd be tempted to clean the existing coils off the stator, then wrap as many multiple strands of medium-sized wire as I could fit and series up as many legs as possible in each phase. . . so I could turn the engine slower and give up a little charge rate for better life expectancy.

-Dan

It's not a case of 'Save the planet,' it's a case of 'Save the humans.'

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#2)
by Nando on Fri Dec 02, 2005 at 10:48:05 AM MST

Clifford;

You better define how the generator works, before yu tackle this job.

It is a small engine with few CC that may run at high RPM. let's say 6000.

The photos show 8 magnets and each magnet covers 3 coils, which says you have 8 poles producing 4 Hz per each revolution and at 6000 RPM of 100 RPS ( REVs per Second) it will be producing 400 Hz at 6000 RPM.

It is a three phase scheme into 60 or 50 HZ output, now observe that the generator has a sw winding .

You have, I think is a commutator converting the 400 Hz to 60 Hz ( 50 HZ for other areas of the world).

Suggestion. by some means, which I can not tell you since I am not familiar with the generator, vary the RPM in 500 RPM steps from low (idle) and measure the output voltage of the DC and the AC if possible, if the AC is not possible you may need to go into the AC converter and find the rectified high frequency voltages, this way you may find the best RPM - voltage output to cover your needs.

Alternative solution is to find 3 power transformers and connect them to the generator three phases, prior the 400/60 Hz converter and the secondaries as needed.

This way, if you do it properly --you keep the generator as it is -- to have 115 volts AC and to be able to have the Secondary output DC voltage you aim for.

Also, the power losses are within the posses you may have if you modify the generator windings.

I have a very old 250 watts generator (Italian, 2 cycle, companion to my bike front wheel friction 2 cycle motor -- 0.8 HP -- with more than 30 years age) that has 115 volts AC at 200 HZ, which I have set it to produce about 145 Volts AC which I rectify bipolar ( +200 & -200 Volts ) and from there I have a small DC/AC converter (60, 50 and 400 HZ and/or 12, 24, 48 DC charging Volts if needed) very accurate since it uses crystal oscillators to maintain the frequency.

I presented my idea so you may think about it and for you to adjust your thinking to a possible better decision to make.

Nando

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#3)
by Clifford on Fri Dec 02, 2005 at 11:55:10 AM MST

Thanks for the comments.

Someone has shrunk the photos for easier display. However, you can view the full size photos by opening them in a separate window.

----------

There are two types of "generators".

The classic generator is phase locked to create 120V, 50 or 60 HZ.

Honda, and a few other manufacturers have modified the generators to run an alternator, which is rectified and fed into an inverter which gives a more stable phase and voltage output, but depending on the inverter, it may or may not have a good sine wave. It is also easier to regulate the output power.

A couple of corrections:
The engine is a 2-stroke - 34.4 cc engine with a 3000/4500 RPM switch.

It has 8 magnets, but each has two inward facing poles, giving a total of 8N poles and 8S poles, or the equivalent of 16 magnets.

I haven't been successful in finding a Honda EX500 manual. However, there was one of the generators on E-Bay recently (I didn't buy it). That doesn't mean it wasn't from timbuktu. However, the seller said that it was 110V, 60HZ with the 34.4 cc 2 cycle engine that the EX350 uses. The plug appears to be "American Style". Looking at the back of the generator it appears to have a 110 outlet, but does not have a 12V outlet. And, it would make sense if the EX350 uses about 1/3 of the windings for 12V, and 2/3 for 110... that the EX500 would use 100% of the windings for 110V.

I did consider feeding the generator into a battery charger then back to the battery, but it seemed to be a bit redundant.

However, getting a single transformer may do the trick (again with losses converting from 3phase to 110V single phase and back to 12V.

[ Parent ]

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#4)
by nothing to lose on Mon Dec 05, 2005 at 01:04:15 AM MST

"I did consider feeding the generator into a battery charger then back to the battery, but it seemed to be a bit redundant."

Maybe not too bad. If you convert this 120V AC generator to a DC generator direct to batteries how do you plan to prevent over charging the batteries? And then you have no AC backup if you ever need it.

There is a simple charger posted here that uses a capacitor to limit amps and a rectifier to convert to DC. I can never remember the UF value per amp when thinking about this.

Anyway if the genny is running good as an AC generator perhaps just rectify that AC output instead of rebuilding the whole thing?
I am thinking about doing that with the 2500watt I just got. So far have not even started mine yet though, got it on trade for a car.

I figure at full load max power is 120Vac at 2500watts. That's a tad less than 21 amps. 2500 watts at 12Vdc is a bit under 210 amps. If I figure I want a 100amps charge rate then I should be running the genny around half load, use less feul, longer life for engine. I need to figure my caps on the AC to limit down to 10 amps 120Vac, rectify that and I should have 120V DC at 10amps or 1200watts. Feeding into a 12V bank of around 1000amps the batteries should hold the volts down to 12V till fully charged and at 1200 watts I should be getting 100 amps charging.
Now the problem with this simple type charger is there is nothing to stop over charging the batteries (or limit the volts) once they get full and voltage will continue to rise and fry them. You either have to watch close or have another system to turn it off.

Now my thinking also is the genny is controlled by the load on it. More feul used and harder running the heavier the load, less feul easier running the lighter the load.
Since you can easily add up DC amps for extra chargers you could build as many simple chargers as you have plugs for on the genny. (or use on off switches for each and put as many as you want on one line)
If you want max 200amp charging and have 4 plugs available, build 4 50amp chargers. When batteries are pretty low use all four chargers for 200 amp charging, as the bank charges remove a charger and have 150amps, remove another for 100amps.
Myself I will probably build various chargers as seperate units then I can use each as needed or take one elsewhere also.

Anyway that's my thought on how I will be doing mine basically. Anytime I need AC power I still have the genny for AC backup. If I need to charge the battery bank a bit at times plug in a simple charger and watch the volts till I hit around 12V. At 12V I will have plenty of battery power in the bank ready to use and still room for other charging methods like wind genny to top them off.

Some kind of controll would be good to shut off the chargers at a preset voltage like 12V, but knowing the banks total amps and present voltage a person should be able to figure out about how many amps to charge and stay well below full.
Can't remember where I saw the chart, but something like 12.5V is 100% full, 12V is 90%, 11V is 70%, (numbers not correct, just example) So if that were correct and I had a 1,000amp bank then 11V being 70% would mean I was 30% low or 300amps. Saftey would be perhaps 200amps, charge at 100amps for 2 hours, or 200amps 1 hour. Still staying about 100amps below full charge. In such a manner a person could easily and quickly make a close geuss and certainly leave lots of room for error on the safty side to prevent over charging and raising volts far too high.
Now like I said I am sure the above numbers are NOT correct, just an example of a quick figure to decide how much to charge. Being sure to always figure not enough charging to actually bring the bank up to full. If the estimate is 2 hours at 100 amps, then in about 2 hours check the volts again and see where the system sits. If needed charge a bit more.

I think this type of fast charger would be good for allot of uses, especailly when heavy loads are needed on the batteries and inverter like aircompressor, welder, grinders, etc..
Charge off the genny for an hour or two, run randon devices all day. Why run a genny all day when the loads are seldom on. And it takes time from work to constantly start and shut off the genny each time you need a load to run.

.
nothing to lose

Spelin and tpying are my strong points, not electronics.
[ Parent ]

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#5)
by Clifford on Tue Dec 06, 2005 at 09:51:57 PM MST

Thanks for the comments.

I didn't tear my generator apart yet. But, the time will come, soon, I think.

I have looked at several dual AC/DC generators, and noticed that most charge batteries at less than 10 amps... I assume the reason is that many batteries don't take kindly to HUGE amperage/wattage being pushed in.

There was a 28V military generator on E-Bay recently. Perhaps I should have picked it up.

Anyway, one can distribute the generator's amps across a bank of multiple batteries... so no single battery gets the full brunt of the charging and thus increase the limits a bit.

If I take my generator...

350 watts AC + 8 Amps DC... it works out to be about 450 watts... or less than 40 amps which I can distribute across my batts and it should be fine. I think I would risk huge problems if I went up to 5 times that.

I was thinking about charge controlling.
If converted to DC, I could probably push the whole thing into a 48 Amp MPPT and wouldn't have to worry about tuning the output either.

Or...
Try to make a circuit the trip when the amps drop or the voltage increases. But, that would work best if I had an auto-start on the thing.

My thoughts about grinders and etc...
Sure, I have tools that pull around 15 amps 110V... and perhaps my welder can pull a bit more. Obviously a 350 watt generator wouldn't be able to help with either AC or DC. However, If I grind for 10 minutes in an hour... the 350 watt generator would just about be able to keep up with my needs... (doing small stuff).

As far as battery chargers...

Cummings Tools had one out of the box that was supposed to charge about 4 (or 6???) batteries at 8 amps (I think). It might be worth looking at. But, it was a bit expensive ($300 range).

[ Parent ]

Re: Converting Honda EX350 from AC/DC to DC only (3.00 / 0) (#6)
by nothing to lose on Wed Dec 14, 2005 at 06:36:00 PM MST

I probably read something wrong before, you have a 350watt AC generator?
Without reading back through the whole thread I think I was thinking you had a 3500watt generator perhaps? Very big difference of course.

Yes I think if your going to have about 40 amps max DC charging into 12V batteries you should be ok. I have L16p Trojans, 360 amp hours, I charge those at 40 amps often, and so far no problems. I badly abuse these, they are a couple I rescued from a scrap yard very cheap, after desulphating a few days/weeks they worked like new. I had gotton 10 trojans, 4 never did anything, 4 L16p's and 2 slightly smaller ones worked great. I forgot now how long I desulphated and slow charged etc... various ones now though.

I think I would try for a bank of over 400amp hours for 40amp charging, that would be a C10 rate. More batteries you have of course the less you drain them down with the same load, so they may last longer. If your load is like 200amps per day that is 50% of a 400amp bank or 25% of an 800amp bank. Still the same 200 amps you have to charge daily (plus self discharge) but the larger bank would be charging closer to a C20 rate at the 40amps and also a shallower discharge cycle would probably mean longer life.

My generator is a 2500watt and I was thinking yours was bigger than mine. Mine I'll have to cut back on the charging amps when I build the converter charger and then with less than a full load I'll also use less feul and engine will last longer under less load.
.
nothing to lose

Spelin and tpying are my strong points, not electronics.
[ Parent ]

Converting Honda EX350 from AC/DC to DC only | 6 comments (6 topical)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board

Login

Make a new account

Username:

Password:

Total Views

��94 Scoop users have viewed this posting.

Related Links

� magnet
� Also by Clifford

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!