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Motor to Generator operation Controller
By Usman, Section Controls Posted on Fri May 16th, 2008 at 03:50:49 PM MST
Any better way of over-crank/under-crank protection

I have just found the Lister engine I have been looking for that is a slow speed, 1000 rpm, 9hp, original English made, air cooled, but without a starter motor and a generator. It does however have the provision for the starter motor to be placed in a casing with the flywheel.
I have a 48V wind turbine/solar array connected to a larger 48V battery pack as well as a small 12V battery pack (for lighting and controlling relays) that may need to be charged during days of low wind/low sun, I am intending to using the diesel generator as a back up.
I need to convert the manual or hand crank start type diesel engine into an electric one. The engine should be started automatically by a voltage monitor, which upon sensing a low-voltage on the 48V battery pack, energize relay to run a starter motor.
The problem that I am facing is how to protect the starter motor from over-cranking, since this would be an auto start & without any human intervention. The relay can be timed for a period of 0-a few seconds but that may under-crank or over-crank the engine, resulting in either failure to start or damaging the starter motor.
I have been investigating into this issue and came across a number of mini-controllers that offer that functionality, but that required synchronization, which I feel is a risky business.
I have finally decided to use a PM 12V motor for cranking up the engine as well as charging the small 12V pack. The PM DC motor would be always coupled to the engine by means of a timing belt and when the Voltage Monitor energizes the relay, the DC motor acts as a motor to turn the engine for 10 seconds, allowing ample time for the engine to start, and after that when the relay is de-energized, the PM DC motor turns into a Generator and starts to charge the 12V batteries, along with the 48V generator.
I am looking for a circuit or a ready made controller that could do the motor to generator conversion once the VM has de-energized the starter relay.
I would further appreciate any other possibilities to achieve the above with minimal hassle. Any input would be appreciated.
Thanks, Usman.

Motor to Generator operation Controller | 5 comments (5 topical, 0 editorial)

Re: Motor to Generator operation Controller (3.00 / 0) (#1)
by wdyasq on Fri May 16th, 2008 at 11:11:58 AM MST
(User Info)

Bosch built a version of this called the "Dynastart" using a conventional generator instead of a PM unit. Amongst mechanics it had the enduring term 'Damnastart', mostly due to the problems with the regulators and relays.

There are diagrams on the internet that show how they are wired and how they worked.

I can think of several ways to assure the engine would be running with oil pressure before the 'starter' dis-engaged and also assure proper shutdown if things were not working as planned. Oil-pressure activation, voltage reading and over-temperature switches should be employed.

Ron
Adventure is just bad planning." -- Roald Amundsen

Re: Motor to Generator operation Controller (3.00 / 0) (#5)
by Simen on Tue May 27th, 2008 at 01:21:04 PM MST
(User Info) http://www.mwlmf.net

I have one of those on my vintage(1958) 12hp 2cyl gasoline engine in my wooden boat... ;)

It's not the strongest of starters but works ok, and delivers a charge of max 11Amp. (There is an 20Amp available too i think...) I'm not sure of the power as a starter, but i think it draws around 50-60Amp.
The regulator is an mechanical variant, and is not suited in a humid enviroment like a wooden boat (hence the nickname Damnastart... :D ), but there are seldom any problems with it as long as the regulator are kept dry.

The problems starts after the boat has been at the bottom once, and the starter system didn't get a proper overhaul... :D (I speak of experience... :D )

As a dynamo, the dynastarter thrives at 3000-3500rpm, which is easily archieved on these old engines with big flywheels. The flywheel on my engine is approx. 15", and the wheel on the dynastarter is approx. 3.5" (4.25:1 ratio); running speed of the engine is around 750rpm.

[ Parent ]

Re: Motor to Generator operation Controller (3.00 / 0) (#2)
by jonas302 on Sat May 17th, 2008 at 05:56:17 AM MST
(User Info)

remote car starters moniter the voltage of the battery to disengage the starter
not being an electrical engineer I might be tempted to try to modify one you could even use the brake switch wire to hook to a temp sensor ect to kill it

As far as going back to generator mode it would seem if you applied power between the diode and moter it would generate as soon as your relay opened Or maybe use a double throw relay the normally closed contacts for batt charging

Re: Motor to Generator operation Controller (3.00 / 0) (#3)
by Old F on Sat May 17th, 2008 at 04:20:59 PM MST
(User Info) http://www.oldf.homestead.com

This outfit has what your looking for there controllers' have provisions for glow plugs if needed

http://www.atkinsonelectronics.com/list.asp?lt=alte&mn=1

Hope this helps

Old F

Re: Motor to Generator operation Controller (3.00 / 0) (#4)
by Ungrounded Lightning Rod on Sat May 17th, 2008 at 06:09:44 PM MST
(User Info)

Using a DC motor as a generator and an autostarter?

Just short the blocking diode to start.

Turn the short off after a timeout. The engine is either running by then (and the motor running as a genny) or it's not (and requires manual intervention).

A high-current self-resetting circuit breaker protects from burnout if something is jammed and the motor doesn't spin up.

Motor to Generator operation Controller | 5 comments (5 topical, 0 editorial)

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