Very Hot Weather and AGM Battery inside truck shell

[FoxenTec]

I currently have a Tacoma 4WD truck with an A.R.E. DCU commercial aluminum shell. I live where it often is above 100 degree's in the summer months.

Inside I have two 105ah Lifeline AGM batteries wired in parallel and fed by 200 watts of solar through a MPPT Controller. This runs our Engel fridge, lights, fan and phone charging.

Today was in the low 100's and inside the truck cab it reached 118 while inside the aluminum shell was 109. I know we will see significantly hotter weather then today and I am wondering if I need to move some air in the shell for the batteries. I have a 3" vent to the outside for the batteries and I often leave the shell front slider open with a screen on it. Would it benefit having a fan run in the shell on these really hot days or am I worrying about nothing?

I have seen thermal runaway in huge -48V DC battery plants inside telecommunications offices and want to avoid any issues with my little truck shell batteries.

Thank you!

 

[PaulT]

Sounds like you have sufficient battery & solar to run a swamp cooler to drop the temps some. You might consider that if you have access to water.

Paul

 

[rando]

In terms of safety, I don't think this is a real issue. This doesn't sound as bad as the conditions the starting battery under the hood experiences, particularly under similar weather conditions.

This will significantly reduce the lifespan of your batteries though, at temperatures around 40C (what you are describing) the battery will only last about 1/4 the lifespan at 25 C. This is also why car batteries only last 2-3 years in Arizona and Florida, as opposed to 6-8 years in cooler places.

 

[Wallowa]

In terms of safety, I don't think this is a real issue. This doesn't sound as bad as the conditions the starting battery under the hood experiences, particularly under similar weather conditions.

This will significantly reduce the lifespan of your batteries though, at temperatures around 40C (what you are describing) the battery will only last about 1/4 the lifespan at 25 C. This is also why car batteries only last 2-3 years in Arizona and Florida, as opposed to 6-8 years in cooler places.

Very interesting....how would LiFePo4 batteries fare under these temps?

 

[rando]

Very interesting....how would LiFePo4 batteries fare under these temps?

They would also have a significantly reduced life. It is funny on the forums there is a lot of discussion of not discharging LiFePO4 batteries all the way, not storing them fully charged etc. However the biggest factor in LiFePO4 (and lead acid) lifetime is the operating temperature (see the figure below).

One thing to remember, is that for most of us we are only out exploring in super hot temperatures for a few weeks a year, battery aging will be much higher for those few weeks, but the overall impact is not that significant as the aging will be 'normal' for the other 90% of the time. The testing that demonstrates the much faster aging at high temperatures assumes the battery is constantly at those high temperatures - unless you live in Furnace Creek, that is unlikely to be the case.

Image from: PowerSonic

 

[Wallowa]

They would also have a significantly reduced life. It is funny on the forums there is a lot of discussion of not discharging LiFePO4 batteries all the way, not storing them fully charged etc. However the biggest factor in LiFePO4 (and lead acid) lifetime is the operating temperature (see the figure below).

One thing to remember, is that for most of us we are only out exploring in super hot temperatures for a few weeks a year, battery aging will be much higher for those few weeks, but the overall impact is not that significant as the aging will be 'normal' for the other 90% of the time. The testing that demonstrates the much faster aging at high temperatures assumes the battery is constantly at those high temperatures - unless you live in Furnace Creek, that is unlikely to be the case.

Image from: PowerSonic

Again very informative....Sonic does say this: "@ 55C Li batteries will have 2X the cycle life of a SLA battery at room temp."

Same oh,same oh, I guess, use it until you can't and then replace ...

Thanks for references...

Phil

 

[FoxenTec]

Thank you all for the great info. Always nice to see Rando reply!

I did find from the manufacturer that max storage is 122F and max operating is 160F. I will be adding my temp probe from the MPPT controller to the battery too.