Main Battery in engine bay too hot to charge with MPPT?

[NudeLobster]

Hey guys ,


I replaced my Renogy Voyager PWM controller with a Renogy Rover Elite MPPT that includes a temp probe for temperature compensations. After driving the vehicle the Rover Elite gives an "over temperature" fault, reading 80-85C at the battery. Removing the temperature probe from the MPPT to force a 25*C baseline clears this. I've never read of any MPPTs shutting down charging from the battery being too hot to charge... The unit specs give max operating temperature of 65*C, but it appears the unit will fault if the battery is over that, as well.

Has anyone else experienced this?

It seems pretty common theory to place the MPPT within very close distance to reduce voltage drop and ensure internal temperatures of the charger are equivalent to the battery, and if not close enough then to use a temp sensor at the battery. Does the operational theory of this Renogy mean no charging until the battery is cool enough (essentially house batteries in-cabin only)? It took more than an hour for the battery in the engine bay to cool down enough for the MPPT to charge.

 

[john61ct]

Very few solar-type electronics are designed to be reliable in extreme temp conditions like the engine bay.

Definitely also lowers the lifespan of an expensive House bank, by a lot.

If you have room, put the SC and your bank in a cool location.

Or purchase a SC designed for high heat, likely Aussie

 

[NudeLobster]

I wonder if the battery being too hot had to do with the motor running ?
What begs question if MPPT is really needed at those times.

Oh most definitely, and solar is not needed then, but it does take a considerable amount of time for the battery probe to cool down enough to resume charging after the engine is shut off, losing out on possible energy harvest.

Very few solar-type electronics are designed to be reliable in extreme temp conditions like the engine bay.

Definitely also lowers the lifespan of an expensive House bank, by a lot.

If you have room, put the SC and your bank in a cool location.

Or purchase a SC designed for high heat, likely Aussie

I am running this solar charger to the main engine battery, I do not have a dedicated house battery. I only have a fridge to power/offset so I did not see it worth the weight and cost to add an additional battery.

 

[john61ct]

A fridge is a relatively big load to maintain, very often the biggest in a small system, can be 50+ Ah per 24hrs.

If you are going way off the beaten path alone, high risk of getting stranded with no ability to crank.

And very few batteries suitable for Starter service will last very long doing deep cycling service.

But everything is relative, depends on lots of variables of the use case.

 

[NudeLobster]

A fridge is a relatively big load to maintain, very often the biggest in a small system, can be 50+ Ah per 24hrs.

If you are going way off the beaten path alone, high risk of getting stranded with no ability to crank.

And very few batteries suitable for Starter service will last very long doing deep cycling service.

But everything is relative, depends on lots of variables of the use case.

This is true. the Dometic CFX50 has been tested to draw 51W when cooling. I have a 175W panel on my RTT to feed, as well as a deep cycle Odyssey Extreme G31M battery to allow deeper draw with less impact on starting. with the old PWM it could reliably start after 2 days with out alternator charging using an 80W panel overheated on the hood. I expect ample performance moving up to 175W in a cooler location

 

[NatersXJ6]

I do something similar to what you are. I did not use a temp probe as I was sure the battery would be too hot to charge. It does cook off some water.

my solution:

use cheap FLA battery and replace as needed
Add water often
Charge controller is inside the footwell about 3 wire feet from the battery.

the reality:

With 200 watts of solar panels and an mppt controller, running only a fridge, radios, and some lighting, my battery rarely draws down far enough to even pull much charge unless I don’t drive for a few days, then the battery is cooler and the solar keeps it topped off.

system has been running close to 2 years now through several months of 100 plus outside temps without a hiccup. The battery was a $90 group 27 from one of the parts stores that start with a vowel. I might change it this winter just for peace of mind.

before this I trashed several high dollarAGMs because I wasn’t charging them enough or properly

 

[NudeLobster]

I do something similar to what you are. I did not use a temp probe as I was sure the battery would be too hot to charge. It does cook off some water.

my solution:

use cheap FLA battery and replace as needed
Add water often
Charge controller is inside the footwell about 3 wire feet from the battery.

the reality:

With 200 watts of solar panels and an mppt controller, running only a fridge, radios, and some lighting, my battery rarely draws down far enough to even pull much charge unless I don’t drive for a few days, then the battery is cooler and the solar keeps it topped off.

system has been running close to 2 years now through several months of 100 plus outside temps without a hiccup. The battery was a $90 group 27 from one of the parts stores that start with a vowel. I might change it this winter just for peace of mind.

before this I trashed several high dollarAGMs because I wasn’t charging them enough or properly

That is a good point, with my new 175W panel, I should get plenty of charge for my needs even though it will only be running for less time when the engine bay (battery) has cooled enough. Thanks!

 

[broncobowsher]

I have my charge controller inside the cabin (actually in a kick panel as that was a good fit for it). It pulls temp from that location.
Theory being when parked the cabin temp isn't that far off from the battery under the hood. While driving, irrelevant, alternator is charging. The temp compensating setpoint won't match for a few hours after driving. No big deal. In the grand scheme of things it is a short amount of time. Heat stress on the battery is a bigger stress than a slight change in ideal voltage. I pulled 7 years out of a battery in Arizona that normally kills them in 2 years doing this. And at the 7 years it still worked, time for some preventative maintenance. Change it before it fails.

 

[Josie'slandcruiser]

I keep my Victron MPPT in the cargo area, and attach it to the starting battery only when deploying the folding solar panels. Quick attach/detach plugs make this easy and protect the MPPT from the engine bay environment while the vehicle is in operation.

Hey guys ,


I replaced my Renogy Voyager PWM controller with a Renogy Rover Elite MPPT that includes a temp probe for temperature compensations. After driving the vehicle the Rover Elite gives an "over temperature" fault, reading 80-85C at the battery. Removing the temperature probe from the MPPT to force a 25*C baseline clears this. I've never read of any MPPTs shutting down charging from the battery being too hot to charge... The unit specs give max operating temperature of 65*C, but it appears the unit will fault if the battery is over that, as well.

Has anyone else experienced this?

It seems pretty common theory to place the MPPT within very close distance to reduce voltage drop and ensure internal temperatures of the charger are equivalent to the battery, and if not close enough then to use a temp sensor at the battery. Does the operational theory of this Renogy mean no charging until the battery is cool enough (essentially house batteries in-cabin only)? It took more than an hour for the battery in the engine bay to cool down enough for the MPPT to charge.