Battery Heat Barrier
Submitted: Monday, Jan 09, 2012 at 16:21
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Allan B (Member, SunCoast)
After the recent upgrade to the Troopy's auxiliary battery system and the purchase of a replacement AGM battery, I turned my attention to the heat that the batteries are exposed to in the engine bay.
Now I know that it gets damned hot in there and I know that batteries, particularly AGM's, do not like high temperatures so I contrived to install a thermal barrier to protect the batteries. I used 12mm closed-cell foam with one-side foil backing. This was doubled-over to increase thickness and provide foil on each side then installed to segregate the engine bay. Being flexible it fitted rather
well down to the inner mudguard and cooling air can flow through the grille but outside the radiator then over the batteries and exit down below the firewall.
Image Could Not Be Found
Now for the performance
test:
It was only an extended local drive and lacked both the high ambient, high engine load and slow vehicle speeds of say the Simpson, but it was a preliminary
test.
After a short run allowing temperature to rise from 30c ambient:
Engine bay 61c, Battery bay 45c
Engine bay 64c, Battery bay 46c
Engine bay 68c, Battery bay 48c and stabilised.
A significant reduction of battery environment temperature. I'm pleased at the improvement with little cost or effort. Perhaps now some fine tuning in the way of scooping more intake air.
Incidentally, I do not subscribe to the proprietary close-fitting battery heat protectors. Without the provision of internal cooling air flow they can only slow the transfer of heat and at the same time prevent the escape of heat caused by the charging of the battery.
Reply By: Wayne (NSW) - Tuesday, Jan 10, 2012 at 06:10
Tuesday, Jan 10, 2012 at 06:10
Allan,
Good idea about the heat shield. I have looked at trying to reduce the heat under the bonnet of my 78 Series. I have looked at fitting vents over the batteries, but this has proven to be a big exercise.
What I have come up with, and a few have done it in the past and that is to raise the back of the bonnet using a spacer under the hinges.
The wife has a nylon cutting board, about 10mm thick, I was thinking of buying her a new one (her birthday is coming up soon), so I will cut it up to make spacers.
The only problem that I can see with your idea is when you have to change the oil filter the heat shield will probably be removed and replaced again. Minor point but if the batteries last longer
well worth it.
Wayne
AnswerID:
474533
Follow Up By: Allan B (Member, SunCoast) - Tuesday, Jan 10, 2012 at 08:30
Tuesday, Jan 10, 2012 at 08:30
Hi Wayne,
I had earlier considered the scheme of raising the back of the bonnet but when you look in the engine bay there appears to be plenty of space for the air to flow down past the firewall as it is being forced by both the fan and the ram effect. I really doubt that opening a narrow slit along the back of the bonnet would make any appreciable difference. I considered it more important to shield the batteries from the engine radiant heat and to have cool air, rather than air via the hot radiator, pass over the batteries. Furthermore, there is potential to get oil deposited on the windscreen with that scheme.
The idea of raising the rear of the bonnet seems to be a notion only. I wonder if anyone doing it has actually measured before and after temperatures of the batteries.
Incidentally, I used a couple of thermocouples positioned in the engine bay to measure temperatures with the vehicle in motion.
The shield in my vehicle does not appear to obstruct the oil filter removal and being flexible is an advantage.
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749481
Reply By: Andrew - Tuesday, Jan 10, 2012 at 10:33
Tuesday, Jan 10, 2012 at 10:33
Lifting the back of the bonnet works on some vehicles but not on others. The effect can change with vehicle speed as
well.
The area in front of the windscreen on most vehicles is a high pressure are so that air can actually be pushed into the engine bay from there with the effect getting worse as the speed rises.
There is a famous case of an old (very old) English sports car that kept overheating: they started measuring the airflow and found that the high pressure at the rear of the bonnet where they had vents fitted was taking in air and pushing it out backward through the radiator.
So if you do lift the back of the bonnet it will be worth doing some before and after testing to make sure the result is what you want.
At low speed (below say 50kmh) the effect is much less and it may be beneficial.
feeding air out through vents in the guards would normally be more effective as this is not a high pressure area.
The other thing to remember is that you still need air flowing past your exhaust to prevent it overheating the engine bay so any mod you make needs to take that into account.
regards
A
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474548