PM motor how to control

[bearbutt95]

How or what do I need to control the output voltage of my Permanent magnet motor? I have it hooked up to an old lawn mower motor and it keeps boiling the acid out of the batterys!!!

The batterys is/are in series to 48 volts dc connected to an MIDMNE4448 E-Panel Power Panel w/ 4400W MagnaSine from The Alternative Energy Store

[AbyssUnderground]

You need a dump load controller. This is a controller that "dumps" excess power to a high power usage source (like a heater or power resistors) once the battery reaches a set voltage. All the excess power then gets dumped until the battery falls below the preset level and begins to take a charge again.

If you're doing this with a lawnmower generator then why not turn it off when the battery is full? This would make more sense than continuing to let it run, dumping everything its making and wasting fuel.

If this is an unattended system you will definitely need a dump load.

[kurt]

not enough information what size engine?? what size dc pm motor?? hp, rated rpm and rated voltage?? pulley sizes you used?? how many amp hours are the batteries??  do you have any way of measuring current into the batteries like a dc clamp on amp meter?? if you are pumping allot of amps into the batteries and the batteries get full they will boil if the batteries are to small for the amount of amps you are pumping into them they will boil ect.

[kurt]

one more thing do you have any idea of the battery bank voltage when they were boiling like do you have a volt meter hooked up to the bank so you know when the batteries are fully charged so you can shut off the engine??

[Flux]

You need a voltmeter, a throttle and brains.

When low the batteries will take all you can throw at them . As the voltage rises to the end of the bulk charge point then ease the throttle back to reduce charging current, let it do its equalising if the battery has not been fully charged and then shut it down.

Why burn fuel producing excessive charging current and cook a dump load. I presume this is a back up so just baby sit it and save fuel. If it is a permanent set up then the mower engine will not last long and you haven't chosen the best generator ffor automatic control.

Flux

[bearbutt95]

I spent about $3400.00 dollars on this system "not counting the labor for the electrician" they the alternative energy store said all I needed to do was wire the unit up. so I did, I hired an electrician to do the wiring (licensed) they (The Alternative Energy Store) said it was ready to go.

MIDMNE4448 E-Panel Power Panel w/ 4400W MagnaSine from The Alternative Energy Store.

I have 4-12 volt Adventure Power 4D Marine Battery Volts: 12 Amp Hr: 200 each.

PM motor puts out approximately 90 volts from a 5 hp gas engine at about half throttle I only use the engine to charge the batterys when I feel they are getting low.

Thank you

[jonas302]

it doesn't look like that includes a charge controller what are you normally charging with or plan to use? or is the generator the primary source?

[bearbutt95]

I have had this hooked up for about a month it works great except for the over charging thing. I read somewhere that a person could connect a hot water heater and with an element coil to this and leave it on all the time or just when the PM motor is running and that would end the over charging! is that what a dump load is?

Thanks

[jonas302]

Yes that is a dump load you want a controller to switch it on and off google search the board to find out more about them make sure you find a controller and element that will work good with 48 volts it will switch the load on when the  batts come up to  a certain voltage

With out a dump load and controller you will need to watch the voltmeter on your panel and throttle the moter so it doesn't over a certain voltage and boil also do a board search Im not sure what to set a 48 volt bank to as they get more charged you will need to back off the throttle to keep the volts down

A proper controller will keep the volts down for you it kinda wastes the power bit if you can use the hot water its probly not all bad just throttle so it dumps as little as posible  Hope that helps some.

Are you off grid completly?

[bearbutt95]

Yes I am off the grid about 10 miles to nearest power pole. just rewired this old camp and this system works really well except the over charge thing. All the major appliances are propane maybe I could put in a electric hot water tank just before the propane tank so it might preheat the water before it goes in the propane tank (this could be the dump load???.)

I heard that fork lift battery's are better to use more voltage and amps.

Thank for all your help and info.

[Tritium]

Here we go again. a newbie choosing an offensive screen name. It is not cute.

Thurmond

[bearbutt95]

That is the name of my dog thank you very much!!!

[feral air]

Does the engine have an electronic ignition?

[bearbutt95]

I do not know for sure it is a good 30 years old or more.

what are you thinking???

again thanks for everything.

[ghurd]

Maybe a simple dump controller.

When the battery is full, the ignition is shorted and the motor stops.

G-

[feral air]

I was thinking you could kill the engine when the batteries are full and restart it some time later...automagically...

The controller would kill the engine when the batteries are full and restart a timer. When the timer goes off it tells something to get the engine back on-line. The something would try starting the engine and if it doesn't start after some_number_of_tries the process is halted and an alarm goes off.

Basically. take it easy

[bearbutt95]

That sounds very interesting does the engine need to be an electronic kind???

I can buy a newer type!

 Are you telling me that if the battery's are dis-charged that it wont hurt the battery's if 90 volts is put into them--I have a 48 volt system--just as long as they don't get over charger (boiled). I wish that I could figure all this stuff out!!!

 Thanks for all the info

[ghurd]

You are confusing some numbers.  The motor won't put 90V to 48V batteries, it will put amps into the battery at the batteries voltage.

I don't know much about ignition systems.  A 30 year old motor probably has a very simple way to shut it down, like a tin strap that shorts out the spark plug?

The controller would do about the same thing.  Possibly the exact same thing, or maybe before the coil.  Making a motor stop is pretty easy.

G-

[Flux]

You really must get an ammeter, it is current that you need to know, the source voltage is totally irrelevant.

I seriously think your gassing problem is simply that you are over charging your batteries. If they are well down then I can't see any pm dc motor driven from a small engine being any problem at all. When they are fully charged then 5A may be enough to boil them if they are in good condition. Get yourself an ammeter and when the voltage gets well up ( about 55v for 48 v system) then you need to throttle back the engine to drop the charging current to about 10A.

Ideally use a hydrometer to check the s.g. and when there is no rise after 1 hr you can be sure you are fully charged and just shut down.

You only need to gas the things occasionally and normally you could stop the charge at about 56v. Perhaps once a month reduce the charging current at 55v to prevent violent gassing and let them stew for an hour.

Maybe your solar is being perfectly effective and you don't need the engine at all if gassing starts almost immediately.

Just completely stop worrying about charging source voltage, it seems impossible to get people to understand that the battery determines the voltage not the source. The dc motor's open circuit voltage depends on how fast you run it, it may be nowhere near the nominal 90V, it could be lower if you run it slowly or it could be far higher if you run it above its original motoring speed. It just doesn't matter, alter the throttle to control your current and it will be fine.

Flux

[bearbutt95]

That is exactly how I shut it off. I push a piece of metal against the spark plug.

I live in an area that does not much info for me I have been searching the web.

You know if you don't know what a item is called it is really hard to do a search.

How do I figure out the amount of amps that this motor is putting out?

Should I get some gauges or meters for volts and amps?

Here is the label info:

Permanent Magnet DC Motor

Rotation        CW

Voltage         120 VDC

Enclosure       Open

Speed           5600 RPM

Horsepower      2.5

[bearbutt95]

Thank you so very much.

 I am going to buy them (1 for amps and 1 for volts) locally if I can. Should I get a digital or needle type?

The Battery's are brand new a month ago. When I hear the acid boiling I always shut off the engine I don't think I lost any acid from the battery's!!!

[Flux]

"How do I figure out the amount of amps that this motor is putting out?

Should I get some gauges or meters for volts and amps?"

Yes go and get yourself an ammeter. Doesn't matter about volts as far as the generator (motor)is concerned but a reasonable multimeter to measure battery volts is almost a necessity unless your solar metering has something.

As far as the motor goes then you need to run it at a maximum of about half its nominal speed so direct from the engine should be near enough. If anything a slight speed increase rather than decrease so you don't have to rev the engine too much.

The maximum long term rating is only about 16A  so don't exceed that for long or you will cook the motor. A 200 Ah battery should take the full 16A until nearly charged then for the last bit you need to throttle down to a lower current for the final charge.

You really shouldn't be running these things with no means of measuring current, the motor is in far more danger than the battery. I am sure you are charging longer than needed and that is why the battery is boiling.

Flux

[bearbutt95]

Thanks for the info I called the local auto parts store they said that they have a digital multimeter. I hope that will do the trick. it does volts and amps.

Thanks again

[Flux]

A few go up to 20A, most only go up to 10A. You can read amps by measuring the volt drop of a shunt if you understand what you are doing. I think TomW has a figure for a foot of #10 copper wire or similar that makes a simple shunt.

You seem unsure about meters, make sure that you measure current in series with the charging circuit, don't try sticking the meter across the motor leads on the amps range or you will be looking for another one. I far prefer analogue meters for this sort of current measurement but you need a digital to measure battery volts so that is the best buy if you want one to do everything.

Flux

[ghurd]

Something in the numbers seems WAY off to me.

I get about C/20.  

That is where many companies say a controller often isn't needed.

OR the PM DC motor should have burned out after not too many hours.

I get the feeling you need to trust the solar panels more, and get some meters you understand.

G-

[Gary D]

 I have a feeling that solar panels aren't being used at this time. ALL charging is from the pm unit attached to the mower. If this is the case, it won't take long for the mower and the pm generator to die untimely deaths. They should be used as backup.

 Perhaps as funds allow, several solar panels can be added(totaling 48 volts). It will increase the life of the motor/generator combo. It will also lessen the cost of gasoline/ oil changes.

 Be sure to only fill the batteries with distilled water. No battery acid should be needed.

 Hope this makes sense to you... Gary D.