Prado 150 Second battery DC to DC charger running hot

[peter69_56 Lurker Find all posts View Profile Close peter69_56]

I have a CTEK D250S DC to DC charger. Fitted on top of the fuse box on passenger side behind the battery. It runs hot on hot days so I put a heat shield around it with air gaps under the heatshield and under the charger. Has anyone else had issues with their charger derating in hot weather to a point where it hardly charges.

I see the redarc 20 amp charger derates from a temperature of 50C full charge to 80C no charge.

I am assuming that the CTEK is the same, but on writing to them they suggested the data wouldn't help me so refused to pass the information on to me. So all I can assume is, that their charger derates the same as the Redarc or derates more hence their refusal to give me the derating information. Does anyone have data on the CTEK?

Only other solution would be to put it inside the cab, which I don't wish to do.

I also put a heat shield beside my second battery to help prevent heat from the engine cooking it. Seems to be working as the plate is hot but battery much cooler.

[Guest Close Guest]

You should move it in front of the radiator.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

When I did some temp tests with a heat gun, above the fuse box was one of the hottest spots. I tested there as I have seen arb install them there.

Amts, I have heard of people putting it in front of the radiator. Any photos? Does water get to it with rain?

[Guest Close Guest]

Amts, I have heard of people putting it in front of the radiator. Does water get to it with rain?

It probably would. Needs some shielding or find somewhere else cooler in the engine bay.

But if there is no need for the solar panel input, I don't see the need for a DC-DC charger. A voltage booster diode would be a good alternative if it is a 150 3.0L 1KD and the aux battery is in the engine bay.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

The charger should be located close to the battery if it has an inbuilt temperature sensor so
that it can supply a suitable charge voltage to the battery, ie battery in hot environment,
charger in cold environment will lead to overcharging of the battery.

In the Prado with the battery mounted behind the headlight the battery gets some cool
air stream to cool it, if possible mount the charger between the head light and the battery
so it gets some cool air too.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

So how does an alternator with diode booster control the heat issue?

[Guest Close Guest]

So how does an alternator with diode booster control the heat issue?

Won't need the DC-DC charger then.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

So wouldn't it overcharge a hot battery then

[Guest Close Guest]

So wouldn't it overcharge a hot battery then

OP has an issue with a hot DCDC charger, not with the battery. A hot battery is probably already overcharged.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

Leigh made a point about hot environment and cold environment, hence I asked about the alternator overcharging. Just trying to understand this all better. From my understanding the alternator will overcharge a battery if it is hot. A dc will not do this.

[sweetpea Senior Member Find all posts View Profile Close sweetpea]

The charger should be located close to the battery if it has an inbuilt temperature sensor so
that it can supply a suitable charge voltage to the battery, ie battery in hot environment,
charger in cold environment will lead to overcharging of the battery.

In the Prado with the battery mounted behind the headlight the battery gets some cool
air stream to cool it, if possible mount the charger between the head light and the battery
so it gets some cool air too.

The Ctek D250S has a remote temperature sensor to attach to the auxiliary battery to monitor the battery temperature and adjust the charge voltage accordingly.

The sensor cable is 2 M long so the charger and the battery being charged don't need to be located together for temperature control purposes.

S

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

So how does an alternator with diode booster control the heat issue?

The Alternator is temperature compensated, if you monitor its output
you'll see it is higher when you first start the car and it will gradually reduce
as the engine bay heats up.

[peter69_56 Lurker Find all posts View Profile Close peter69_56]

The Alternator is temperature compensated, if you monitor its output
you'll see it is higher when you first start the car and it will gradually reduce
as the engine bay heats up.

Yes I have noticed this. Also I am reluctant to use a booster diode as I have noticed that on cool days the car battery voltage currently runs at 14.2 v, putting a booster diode in will then boost this to around 14.9 v which seems a bit high. As I am in Gippsland we do have much of the year at low temperatures. Normal battery voltage is 13.8-14.2 v, thus 14.9 may overcharge.

Having introduced clearance between the heat shield base and the charger base plate has helped. Will be interesting to see how I go in WA and NT Aug/Sept this year.

Also knowing the derating data would help as I could monitor areas to find a cooler area. I have opened some foam blocking an opening in the front ratiator support panel near the headlight and this allows some cooling air in too.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

Thanks Leigh. I don't have anything to measure amps on the 2.8 but would love to see how it works.

With regards to the temp under the engine bay in the 2.8. There is very little difference to where the 2nd battery goes and the space behind the air box. In front of radiator was coolest but I was concerned about rain. Fuse box was hottest place of those 4 areas tested.