snowleopard
Well-Known Member
Well I splashed out £3.07 this morning on a 30A headlamp type relay. I'll report back on how well it works.
Percussive maintenance (Yanmar diesels)
- Thread starter snowleopard
- Start date
lw395
Well-Known Member
[ QUOTE ]
Not really. With respect you are complicating the issue unnecessarily. An SRB601 with 40A capability does not need the protection of a diode. It does not matter if the load is inductive or resistive. It's the current that matters and that will be way lower than 40A to fully energise the coil of the solenoid. On either boats or cars its the KISS principle that is important. Buy good quality components, never have marginally specified kit and fit big fat wiring where you can and it will not only work but keep working. Simples!
[/ QUOTE ]
With respect, I have seen several 40A relays fail prematurely in precisely this application, so personally I would follow the advice of Omron and Matsushita and fit some sort of suppression, or use a relay that is specified for the exact purpose. It is common to de-rate contacts for inductive loads by up to a factor of 10, occassionally more, if no suppression is available.
To quote from a manufacturer:
"When the load is inductive the switching
current must be reduced still further and is
determined by the time constant of the load
(L/R). A protection circuit can be incorporated
to reduce the arc time. These are commonly
diodes or RC networks and can give efficient
arc suppression. Other methods include the
use of zeners, varistors and other transient
suppression components. These can be
costly, don’t always achieve a significant
improvement in contact life and can cause a
delay in reaction times. Limited test data is
available so it is usually best to test the relay
in each application to check the required life
can be achieved. "
I can't find a proper spec for the SRB601. I know there are special relays with suppression built in, but last time I needed one I got it from a scrap car.
I find that an engine that will not start when you want it is what complicates life unnecessarily. At least a spare relay isn't going to break the bank.
Enjoy your weekend /forums/images/graemlins/smirk.gif
Not really. With respect you are complicating the issue unnecessarily. An SRB601 with 40A capability does not need the protection of a diode. It does not matter if the load is inductive or resistive. It's the current that matters and that will be way lower than 40A to fully energise the coil of the solenoid. On either boats or cars its the KISS principle that is important. Buy good quality components, never have marginally specified kit and fit big fat wiring where you can and it will not only work but keep working. Simples!
[/ QUOTE ]
With respect, I have seen several 40A relays fail prematurely in precisely this application, so personally I would follow the advice of Omron and Matsushita and fit some sort of suppression, or use a relay that is specified for the exact purpose. It is common to de-rate contacts for inductive loads by up to a factor of 10, occassionally more, if no suppression is available.
To quote from a manufacturer:
"When the load is inductive the switching
current must be reduced still further and is
determined by the time constant of the load
(L/R). A protection circuit can be incorporated
to reduce the arc time. These are commonly
diodes or RC networks and can give efficient
arc suppression. Other methods include the
use of zeners, varistors and other transient
suppression components. These can be
costly, don’t always achieve a significant
improvement in contact life and can cause a
delay in reaction times. Limited test data is
available so it is usually best to test the relay
in each application to check the required life
can be achieved. "
I can't find a proper spec for the SRB601. I know there are special relays with suppression built in, but last time I needed one I got it from a scrap car.
I find that an engine that will not start when you want it is what complicates life unnecessarily. At least a spare relay isn't going to break the bank.
Enjoy your weekend /forums/images/graemlins/smirk.gif
snowleopard
Well-Known Member
Having a couple of spare relays in the toolbox is no problem. Can I take it that the arcing likely to occur because of the induction of the solenoid coil is unlikely to weld the contacts of the relay shut. That could get very expensive!
lw395
Well-Known Member
The relays I've seen fail burned their contacts open circuit.
Welding closed would be a worry! I think the current is probably enough to burn through anything apart from a very good weld, so this failure mode seems unlikely imo.
Welding closed would be a worry! I think the current is probably enough to burn through anything apart from a very good weld, so this failure mode seems unlikely imo.
jonno45
Member
Snowleopard I can let you have a Yanmar starting relay as i have one spare, even though GM series had no option of a start relay this one will fit with a little wiring PM me your address if you want it? I see the GM has been knocked a bit for sounding bad at idle (most likely a 3HM or 1GM with advance injection timing) But they are dependable if looked after, just look how many are out there!
peter_il
New Member
I have been following this thread with big interest - and I find Boatmikes post to fit my experiences.
I have a Yanmar YSM8G, and I have been having starter troubles for years. I replaced the relay three years ago but start problems still occured regulary. When it fails, nothing happens - no click or anything. I have allways suspected a voltage drop from the battery via the start button to the relay as the engine used to start when on shore power.
Well, a couple of weeks ago it wouldnt start - even when on shore power. I changed the original cables to/from the start button to 6 mm2 - just to make sure. And I installed two new batteries. Measuring with a multimeter I found no voltage drop. It seemed I had 12+ volts to the relay. Measuring on the relay when trying to start however, I only got 8,5 volts (on the connection to the start button). Strange - 4 volts seems to disappear and the engine did'nt start (and no click).
My guess is, I have destroyed two relays over time caused by to low voltage from the start button (fitting Boatmikes description). This should now be fixed (new wires and batteries). I now need to find a new relay that fits the starter engine which turns out to be a bit of a problem here in Copenhagen in the summer :-/
Kind regards
Peter Laursen
I have a Yanmar YSM8G, and I have been having starter troubles for years. I replaced the relay three years ago but start problems still occured regulary. When it fails, nothing happens - no click or anything. I have allways suspected a voltage drop from the battery via the start button to the relay as the engine used to start when on shore power.
Well, a couple of weeks ago it wouldnt start - even when on shore power. I changed the original cables to/from the start button to 6 mm2 - just to make sure. And I installed two new batteries. Measuring with a multimeter I found no voltage drop. It seemed I had 12+ volts to the relay. Measuring on the relay when trying to start however, I only got 8,5 volts (on the connection to the start button). Strange - 4 volts seems to disappear and the engine did'nt start (and no click).
My guess is, I have destroyed two relays over time caused by to low voltage from the start button (fitting Boatmikes description). This should now be fixed (new wires and batteries). I now need to find a new relay that fits the starter engine which turns out to be a bit of a problem here in Copenhagen in the summer :-/
Kind regards
Peter Laursen