Battery Isolator HOT
Submitted: Friday, Mar 11, 2005 at 15:25
ThreadID:
21147
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timber
Hi guys and gals,
Following on from advice from this
forum I have just finished fitting a dual battery system with a Redarc Isolator beween the start and aux batteries to my 3 l diesel Hilux..
All seems to be working
well, however the isolator gets pretty hot when the vehicle is running. Is this normal?
For those interested the costs (in
Canberra) where
Battery tray from Supercheap $16
520 cca battery (the largest that would fit the engine bay space) $139
Redarc Isolator (the cheapest price I could find in
Canberra) $180
Battery cables $70
Homemade battery hold down clamp, 6 pack
Cheers
Buggerlux
Reply By: Mainey (WA) - Saturday, Mar 12, 2005 at 10:24
Saturday, Mar 12, 2005 at 10:24
(Quote extract)Following on from advice from this
forum I have just finished fitting a dual battery system with a Redarc Isolator between the start and aux batteries.
The isolator gets pretty hot when the vehicle is RUNNING.
For those interested the costs (in
Canberra) where
Redarc Isolator (the cheapest price I could find in
Canberra) $180
BATTERY cables $70
Buggerlux(end quote)
timber, essentially you have paid $250 for a solenoid system after you have received advice from this
forum, bugga, it would have paid you to buy one interstate, pay the postage and save yourself at least $80… or buy something else?
Said very simply, heat is the consequence of power (voltage) which is being used directly by the isolator to maintain its ability to operate, eg; open and close the metal contacts against the mechanical force applied to it; therefore this power is not being used to run your fridge, so quintessentially it is only being wasted.
Isolators, due to their very technique of operation and because they are using your battery directly as a power source to remain closed, do get ‘warm’ in use, the difference between warm and hot is what is questionable.
AnswerID:
102152
Reply By: Wok - Sunday, Mar 13, 2005 at 08:03
Sunday, Mar 13, 2005 at 08:03
Bugger Lux,
The Redarc dissipates about 5.5W when ON[control unit has negligible loss]. This translates to about 450mA. The reason it feels hot is because the themal path is not as good as a metal-jacket solenoid. I measured the impedance of an Ashdown hd silver job = 15.6ohms c.f Redarc = 28.2ohms, which means the Ashdown generates even more heat[sees alternator voltage while my Redarc sees 12.5V]
At ambient of 21.9oC the + terminal was 39.1oC after 1hr [supply@14.1V] As the unit was not mounted on metal, this is a 'severe'
test?
Redarc could improve the control unit by dropping the holding-current.
Anyway as the vehicle is usually moving when the Redarc is ON there will be some cooling from airflow?
cheers
AnswerID:
102214
Follow Up By: Mainey (WA) - Monday, Mar 14, 2005 at 20:08
Monday, Mar 14, 2005 at 20:08
(Quote)The exact response from Redarc was: Under normal operating conditions the solenoid will be around 70 degrees C. (end quote)
So why does the Redarc solenoid run at 70 degrees, what causes this added heat, and does it happen to all solenoid systems ???
FollowupID:
360146
Follow Up By: brett - Monday, Mar 14, 2005 at 21:56
Monday, Mar 14, 2005 at 21:56
A solenoid is a coil of wire, just like a heater element, so it will generate some heat, as Wok has calculated above, the coil will need to dissapate approx 5W of energy, mostly via heat. If you can comfortably touch it then it's probably not too hot. Assuming the heat is coming from the coil then no worries about voltage drops as the coil only operates a lever to close the contacts. Now if the contacts are generating the heat then you have a problem.
FollowupID:
360159
Follow Up By: Wok - Monday, Mar 14, 2005 at 23:50
Monday, Mar 14, 2005 at 23:50
Mainey,
Brett has said it all.
If I were worried about solenoids I would have to dump my Toyo, the fuse panel is full of relays for lights etc. After 21 yrs the venerable lady has all her original relays.What vehicle do you know off that has all solidstate switching? Even my old hd metal clunker[isolator] has been switching on/off everyday for God knows how long.
If you think 70oC is hot, try measuring the back-housing of your headlights after running for awhile.
cheers
FollowupID:
360175
Follow Up By: Mad Dog (Australia) - Tuesday, Mar 15, 2005 at 11:27
Tuesday, Mar 15, 2005 at 11:27
5.5 watts is very little compared with what semiconductors have to dissapate when passing large currents. A mosfet passing 40 amps will dissapate about 20 watts will need heat sinking and get bloody hot but they are rated to about 180c but don't really let go till about 300c. Hard to beat the good old fashioned relay.
FollowupID:
360199
Follow Up By: Mainey (WA) - Tuesday, Mar 15, 2005 at 17:40
Tuesday, Mar 15, 2005 at 17:40
It was not my post that claimed (Quote)Since this post I have been incontact with Redarc, they advise that the unit is DESIGNED to run at 70 C. I guesss that is pretty hot(end quote)
my own thoughts are if the unit is actually designed to run for some reason at 70 degree's, then why not modify the design slightly to allow it to run cooler???
or is the heat required for some obscure reason???
FollowupID:
360242