Ventilation / cooling for 150 Diesel auxiliary battery - Mod ideas?

[Andy-150Diesel2010 Lurker Find all posts View Profile Close Andy-150Diesel2010]

Hey Folks,

After a few premature auxiliary battery failures, I'm looking for ways to improve airflow / cooling around my aux battery.

From factory, there's basically done. I tried to take a few pictures but it's so dense in there to be useless. The problem basically though is this...



After the external grill on the front, there are 2 side channels ( the red lines in the picture) which force all airflow to the radiator.The air whch makes it into the bay then is obviously hot, and doesn't provide any cooling for surrounding structures.

The red barriers are also metal, which doesn't make modification easy.

The best thing I can think of so far is something like this...




Mount some roughly 40mm flexible tubing in the bullbar gap here - possibly with a scoop for a bit of ram air effect, and run the tubing under and up past the light, to then be pointing at the battery.

(Red is the tubing, yellow battery behind the light)

Hope that makes sense?

Questions...

1) Anyone done something similar?

2) How effectifve was it?

3) How effective do we think this volume of air will be, as a general thought? Could comfortable do 2 tubes, I think, one for each side of the battery.

4) Any better ideas?

Thanks in advance all.

[gunda Member Find all posts View Profile Close gunda]

I have done what you're not supposed to, which is mount a DCS 100Ah lithium under the bonnet. DCS are claimed to be suitable for under-bonnet placement. The advantage of DCS is that it has a bluetooth module, that enables me to monitor the battery temp while driving. When I've done that, the battery temp is only a couple of degrees above the ambient air temperature. I concluded that the 150 (MY21) aux battery location is well ventilated. It is true that once I stop then the battery temp gets warmer, but not excessively so IMO. The fact that the battery temp only rises after stopping is further confirmation that there's good airflow into that area when driving, at least in standard config. I don't have a front bar, driving lights, etc.

[carco Advanced Member Find all posts View Profile Close carco]

I agree with gunda.
I had twin batteries (parallel) in my 90 and had no problem from engine bay heat.
Corrugations were another matter!
Look at a 200, twin batteries in a very tight engine bay and they survive OK.
My brother in law has twin batteries in his 100 plus a 3rd all squeezed in the engine bay.
It’s VSR controlled for his on board fridge and guess which battery is always dying, that one.
I don’t think heat is the fault here, could be continually under charging. Might need a DC-DC?

[gunda Member Find all posts View Profile Close gunda]

I'd suggest trying to measure the battery temperature in that second battery slot before jumping to the conclusion that heat is the problem in a 150 Prado. I read complaints of short battery life from AGMs.

I originally had my DCS lithium second battery being charged through a Victron isolator, but my auto-electrician, who has the same set-up in his Hilux, found that that particular alternator didn't put out a high enough voltage for Lithium. We've switched to a Redarc DC2DC. The alternator seems to be able to charge it and the van lithiums (via an Enerdrive DC2DC) without problem, although I think at a slower rate when the van is hooked up. AGMs should be less of an issue without a DC2DC, as their voltage is lower, isn't it?

[Leethal Advanced Member Find all posts View Profile Close Leethal]

I believe some overseas markets run two batteries as standard in cold climates which would indicate both battery locations are well ventilated.
If your batteries are not lasting I would be looking at the batteries used and your load duty cycle. Perhaps your running them down to low a state of charge as anything below 50% SOC/12V kills a standard deep cycle (wet cell, Gel or AGM etc.) pretty quickly

Lee

[Andy-150Diesel2010 Lurker Find all posts View Profile Close Andy-150Diesel2010]

Thanks for the replies, guys.

In response to a few of the points above...

Agreed, temperature is not an issue while cruising. After bopping down the highway for 30m and then feeling the aux battery it was noticeably warm, I didn't measure the temperature, but was plainly well below any level of concern.

My truck is pretty much exclusively for weekend getaways though, and any trip almost inevitably involves lumbering along an off-road track at speeds where I won't have 'highway level' air flow. That's more the concern.

Under charging is not the issue. Already running a Redarc BCDC charger and have confirmed through a volt meter that boost, absorption and float voltages are all being provided as desired. Correct battery type is selected etc.

My 1st battery death was caused in part, I'm sure, by repeated over-drainage. Drained it dead a few times after forgetting to turn the fridge off around town. My bad.

The 2nd one to fail though was definitely taken care of though. Fridge cut of was 11.4 volts from the battery. Never accidently run flat.

I hear you that the extra ventilation may not be "critical", but having done all this now I figure why not go the extra yard and make life for it that much better. A few degrees less for hours here and there can only be beneficial in the long run.

[gunda Member Find all posts View Profile Close gunda]

I concede that a lot of low speed driving with a hot engine working hard may be a different kettle of fish. Not my typical usage scenario.

I have wondered how to cool the battery after stopping. I'm not sure that insulation is going to help in that environment. A fan perhaps? First I'd need to monitor the temp more carefully after stopping to see how warm it gets. The rise is fairly gradual. I thought about opening the bonnet, but who does that every time they stop?

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Andy

Fridge cut out at 11.4V cutoff is way to low, 12 volts is considered 25% charge for wet cell, Gel & AGM batteries so 11.4 volts is flat IMO.
Personally I would change the fridge cut out to 12.2 volts at least if not higher.

Lee

[Daniel150 Member Find all posts View Profile Close Daniel150]

Totally agree with leethal.

Heat in the engine bay is not ideal for batteries but is not the culprit for them dieing prematurely.
Any wet cell design (wet cell, agm, gel) should never be taken below 12.2v ideally. Below this the plates start to sulphate up and damage is occurring. Most people will run their aux battery till it dies and then wonder why it only lasts 12 months.
If you care for a wet cell, you should get about 3 years out of it.
Fridge cut outs are generally set too low to compensate for voltage drop due to insufficient wire sizing. Ideally you should only loose about 0.2v between the fridge and battery meaning you can set the fridge cut out at 12v as a minimum.
Personally I never let my wet cells drop below 12.2v and you will have no problems. It sounds like you are dropping the battery too far, not overheating it.

[Daniel150 Member Find all posts View Profile Close Daniel150]

Something else to think about in regards to sizing…
If you run a 105ah true deep cycle (not a hybrid) you have about 50ah of capacity.
Most fridges on the market, run just on fridge setting, will draw roughly 2.5 amp/hour (in ideal circumstances). That gives you at absolute best 20 hours run time before you are damaging the battery.
Chuck into the mix a few lights, pump etc and you really only have capacity for an over night stop and will need a decent charge the next day. Also keeping in mind that the battery will rarely start at 100% charge given it takes a long time to completely charge a battery, something that’s rarely done off an alternator.
I guess what I’m trying to say is don’t expect too much from your battery, especially if you don’t look after it.

[Andy-150Diesel2010 Lurker Find all posts View Profile Close Andy-150Diesel2010]

I concede that a lot of low speed driving with a hot engine working hard may be a different kettle of fish. Not my typical usage scenario.

I have wondered how to cool the battery after stopping. I'm not sure that insulation is going to help in that environment. A fan perhaps? First I'd need to monitor the temp more carefully after stopping to see how warm it gets. The rise is fairly gradual. I thought about opening the bonnet, but who does that every time they stop?

In my case opening the bonnet is actually fine. 99% of the time I use my Prado for weekend trips; get to where I'm going and set up camp. Open the bonnet and connect the solar every time.

So, cooling the batteries during 'shopping trips' and whatever is no concern. Just that pesky low speed driving when off the paved stuff.

[Andy-150Diesel2010 Lurker Find all posts View Profile Close Andy-150Diesel2010]

Andy

Fridge cut out at 11.4V cutoff is way to low, 12 volts is considered 25% charge for wet cell, Gel & AGM batteries so 11.4 volts is flat IMO.
Personally I would change the fridge cut out to 12.2 volts at least if not higher.

Lee

Unfortunately, the highest cut-off settings on the Waeco are

Switch off voltage: 11.8 V
Restart voltage: 12.6 V

But yes, you're point is taken, and I can change the cut-off to the higher 11.8v

That said, I am actually also running solar (not mentioned in my original ticket) so not running the battery down for days. The battery is used through the night, then recharged to full daily.

Something else to think about in regards to sizing…
If you run a 105ah true deep cycle (not a hybrid) you have about 50ah of capacity.
Most fridges on the market, run just on fridge setting, will draw roughly 2.5 amp/hour (in ideal circumstances). That gives you at absolute best 20 hours run time before you are damaging the battery.
Chuck into the mix a few lights, pump etc and you really only have capacity for an over night stop and will need a decent charge the next day.

Yep, understood that whatever supposed AH a battery is, the usable amount is really half that.

At night, the only thing I run is my fridge. Lights, speakers etc. are all battery-powered, and recharged during the day when solar is running.

Though I may crank the fridge up a bit to really chill things in the day, I'll set it to 4c overnight. Obviously, it's cooler at night too, no sun beating down on the truck, so the AH usage is actually fairly reasonable when relying purely on the battery.

At an estimate, I would say I'm asking the battery to do 10-12 hours work each evening/night, at a rate of about 1-ish AH. On a 55AH YellowTop AGM battery.

[Daniel150 Member Find all posts View Profile Close Daniel150]

55ah is too small for an aux battery. I wouldn’t even bother with one under 100ah.
You could try putting an amp meter on the fridge, I’d assume it’s going to draw 2-3 amps per hour.
Effective solar gain is gone by let’s say 6pm for example and effective gain returns at say 8am. That’s 14 hours at 2.5 amps. That’s 35ah over night.
Not sure on your solar panel, but let’s assume you are running a standard camping setup with a PWM (labeled mppt) charger. (Bcf, annaconda, supacentre). These will put in about 5-6 amps at full sun. Full sun from 8-6 is 10 hours or 50ah. The fridge has taken 25ah of these leaving 25 ah to be put into the battery that has lost 35ah overnight.
Adding to that, it sounds like you are recharging lights and speakers etc off the solar as well which makes things worse.
The battery is then starting the next night already 10 ah or half the usable charge gone.
To run a fridge and minimal lighting you need a minimum 100ah battery and a 140watt panel. Your battery is too small. I know I have massively over simplified the calculations but I’m just trying to give a basic demonstration. Throw in some clouds, less than perfect sunlight, panels not getting moved, panels getting knocked over etc and it gets even worse. These calculations come for years of experience and setting up 12v setups so they have been gained from practical experiment’s.

[Daniel150 Member Find all posts View Profile Close Daniel150]

Adding to that, a few mates have rum optima yellow top batteries and haven’t had a great lifespan either.
The one you have is a hybrid, so not truely a deep cycle or a starting battery. It’s a compromise that can do both jobs, but neither one well.

[Andy-150Diesel2010 Lurker Find all posts View Profile Close Andy-150Diesel2010]

Hey Dan,

"55ah is too small for an aux battery. I wouldn’t even bother with one under 100ah.
You could try putting an amp meter on the fridge, I’d assume it’s going to draw 2-3 amps per hour."

Nope, this simply isn't the case for how I'm running my fridge. 1.1, 1.2 ish AH is my consumption. This is tested, not guesswork

.

"Not sure on your solar panel, but let’s assume you are running a standard camping setup with a PWM charger. (Bcf, annaconda, supacentre). These will put in about 5-6 amps at full sun. Full sun from 8-6 is 10 hours or 50 amps. The fridge has taken 25 of these amps, leaving 25amps to charge the battery that has lost 35 amps. Follow???"

I do follow, though a few of your assumptions are off. My 300w panel and mppt regulator put out about 21V and 13A in full sunlight. More than you've accounted for in your calculations there.



55AH is on the small side though, I grant you. I'm off shortly for a few weeks touring with the above: it is what it is, for now. Once I'm back though the 55AH will be getting moved to replace the starter, and a new 66AH will be put in as the new Aux. So there's that.