| Author |
Message |
teej
Samba Member
Joined: November 26, 2010
Posts: 897
Location: Seattle
|
 Posted: Sun Oct 16, 2011 7:19 am Post subject: 120-901 battery contactor/isolator question--getting hot |
 |
|
I realized our alternator charging circuit to the house batteries needed improvement. I replaced the stock silver 30A isolator/combiner weekender relay with a more robust unit. I realized that if our house batteries (2x44Ah=88Ah) were very flat, and some other loads (amp, subwoofer) were operating it would be possible to overstress that 25y.o. little relay designed for lighter duty.
Based on research here and elsewhere I chose the White Rodgers 120-901 Contactor, 12VDC, Continuous duty, 100A, 400A inrush, $20.
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=5763007
Upgraded the wire to the house batteries to 8ga with an inline fuse while at it.
Functionally all seems well: 14.15v to the aux batteries with engine running, which is about .15 to .2v better than before. Voltage loss through the switchgear and wiring only .05v, as measured at starting battery and then at house battery, engine running.
The 120-901 seems very robust however I noticed that it gets quite warm to the touch, some with sensitive skin might say hot. As this is my first experience with this type of contactor is this normal? I mounted it horizontally as they say this is permissible.
Also I couldn't make out any polarity markings for the coil trigger connections. Does this matter?
Thanks electrical experts in sambaland!
_________________
1986+ Wolfsburg Weekender Pop-Top 2.3 WBX Manual Trans
Last edited by teej on Sun Oct 16, 2011 10:46 am; edited 1 time in total |
|
| Back to top |
|
 |
crazyvwvanman
Samba Member
Joined: January 28, 2008
Posts: 9939
Location: Orbiting San Diego
|
| Posted: Sun Oct 16, 2011 8:06 am Post subject: Re: battery contactor/isolator question--getting hot |
|
|
Yes, the larger relays get warm. Not a problem. The polarity of the coil leads doesn't matter. I have used many of those 120-901 relays.
Mark
| teej wrote: |
I realized our alternator charging circuit to the house batteries needed improvement. I replaced the stock silver 30A isolator/combiner weekender relay with a more robust unit. .....
Based on research here and elsewhere I chose the White Rodgers 120-901 Contactor, 12VDC, Continuous duty, 100A, 400A inrush, $20......
The 120-901 seems very robust however I noticed that it gets quite warm to the touch, some with sensitive skin might say hot. As this is my first experience with this type of contactor is this normal? I mounted it horizontally as they say this is permissible.
Also I couldn't make out any polarity markings for the coil trigger connections. Does this matter? |
|
|
| Back to top |
|
|
teej
Samba Member
Joined: November 26, 2010
Posts: 897
Location: Seattle
|
| Posted: Sun Oct 16, 2011 8:25 am Post subject: Re: battery contactor/isolator question--getting hot |
|
|
Thanks crazyvwvanman, I was hoping you might comment. Appreciate the reassurance!
| crazyvwvanman wrote: |
Yes, the larger relays get warm. Not a problem. The polarity of the coil leads doesn't matter. I have used many of those 120-901 relays.
Mark
| teej wrote: |
I realized our alternator charging circuit to the house batteries needed improvement. I replaced the stock silver 30A isolator/combiner weekender relay with a more robust unit. .....
Based on research here and elsewhere I chose the White Rodgers 120-901 Contactor, 12VDC, Continuous duty, 100A, 400A inrush, $20......
The 120-901 seems very robust however I noticed that it gets quite warm to the touch, some with sensitive skin might say hot. As this is my first experience with this type of contactor is this normal? I mounted it horizontally as they say this is permissible.
Also I couldn't make out any polarity markings for the coil trigger connections. Does this matter? |
|
_________________
1986+ Wolfsburg Weekender Pop-Top 2.3 WBX Manual Trans |
|
| Back to top |
|
|
PDXWesty
Samba Member
Joined: April 11, 2006
Posts: 6247
Location: Portland OR
|
| Posted: Sun Oct 16, 2011 9:05 am Post subject: |
|
|
Another good voltage drop test is to turn on some loads with the engine runing and measure the voltages and drops again. With the headlights, brights, and fans running, take another set of measurements. It might drop as low as 13.5 under high load. If the aux battery is discharged it's even worse. It really demonstrates how the voltage drop increases with the amperage flow.
_________________
89 Westy 2.1 Auto |
|
| Back to top |
|
|
|
