Lifepo4 + Hot Van

[Harmony5000]

I addressed both these situations above. If you're not going to read it, I'm not going to write it. I'm out.

I did thoroughly read your post and do appreciate the time, thank you

 

[4thHorseman]

I hadn’t thought of that. I’m trying to vent the whole van as I’ve got other things that need to be cool. I’m curious if you know how many cubic feet per min a fan would need to push to do that effectively? I have no way to test in the climate I’m in right now. Thanks!

You can still vent the whole van. Just make sure the coolest air hits the batteries first then vents out through the rest of the van second. This would be both beneficial during days and nights since you want the batteries to receive as much cool air at night to offset the hot days anyway.

 

[NVS]

You should put in a roof vent. Like this several kinds and prices. They also make covers for them so you can use them in the rain.

Fan-Tastic Vent RV Roof Vent with Thermostat, Model 3350, White, Manual and Automatic Speed 12 Volt RV Vent Fan, Smoke Dome RV Vent Cover https://www.amazon.com/dp/B00HQZB4I4/ref=cm_sw_r_awdo_MD3946V24FE1MZ2P6HFN

Maxxair 00-955001 White Fanmate Cover with Ez Clip Hardware https://www.amazon.com/dp/B010D1VJQO/ref=cm_sw_r_awdo_6NDEPMWYCFN3J1RQXC7S

 

[guidecca]

Hi, I have some questions regarding charge/discharge of lifepo4 in hot environments. I’d like to have a better understanding of risks and possible solutions.

Right off the bat does anyone have experience charging/discharging lifepo4 in a van where outdoor temp reaches an average of 80-85f while they are away from the car all doors and windows closed?

Here is the scenario:

Need to charge/discharge 200ah of lifepo4 battery daily in a city environment (L.A.)while I’m away from the vehicle. High daily outdoor temp in summer months (3 months) is steadily 80-85 degrees fahrenheit. Of course there could be days reaching higher or lower but this is about average high temp each day rest of the year seems to be in the 70s. If anyone lives LA let me know if I’m mistaken? I’ll be parked near Venice beach.

From what I understand temperatures in a vehicle parked in direct sunlight under these conditions can reach 130 on days that are 85. 140 if there is something like a 95 degree day. I’m unsure if that is ambient air temp or surface temp (like dashboard/seat). The batteries themselves won’t be in direct sunlight.

Right now my only defense is custom sunshades I’ve built with Reflectix material (sturdy reflective bubble wrap type material) installed on the interior of the windows. They are fit to where absolutely no sunlight comes in. From what I understand this method dramatically lowers surface temperatures but may have little effect on ambient air temperature - the site that gave that report posted a photo with similar material but it was not tightly fit so I have a one up on that. Their report said ambient air temp was only lowered by 1 degree.

Right now I’m choosing my batteries for the project. It seems like trusted manufacturers charging at high temp shuts off at 113 degrees. Reports for cheaper batteries such as zooms, ampertime, chins, 122. Obviously from what I read we can’t trust reports from company’s like those. Also, the bms systems don’t seem to be reliable for low temp cutoff (not a problem in my case) and I’ve seen some reports of low voltage disconnect not working. I will be using 1 battery outside of the van during the day and completely running it out of juice at times so this concerns me. Just the fact that the temperature inside the vehicle may reach 130-140 and if a cheaper batteries bms fails to employ high temp cutoff this concerns me.

Ok so risks/solutions

Risks:

Battery Life- I understand battery life may be shorted in hot environments. This isn’t a concern to me if the batteries can still be used for 1-2 years. Renogy customer service says they can be stored at 149 degrees which might be the very high air temp in the car a few days. In almost all reports I see temperatures like 149 are at the top of surface temp in direct sunlight not ambient air temp.

BMS - if a cheaper battery is chosen and the bms high temp cutoff fails how likely is it that fire, explosion, or fuming could be a thing?

Battery Choice - right now I’m looking at buying 3 units of 100ah SOK on the high end. Weize (low temp cutoff seems to work and high temp cutoff rating is 113f exactly like battleborn and sok maybe I can trust them?) and on the cheaper side zooms, ampertime, chins. Suggestions? Money is extremely tight but safety is most important. I currently do have a 100ah lithium ion battery (not lifepo4) by SmartBattery 6 years old lots of use, should I discard that/not use under these conditions?

Solutions:

I’ve mentioned the reflective shades. Maybe they can lower to 113 but I have no way of testing and that sounds like an iffy bet.

Would installing simple vent/fan to cycle air from the interior to exterior of the van help? I believe I could build some that slot into the driver and passenger window after I park to move air in and out of what I think would be the area of the van most prone to heat build up (windshield).

Insulated battery box, how much would that help if at all I don’t know?

Ac- I don’t believe I have enough AH to run that and meet my charging needs. I had thought of putting a small portable AC and directly aiming it at the batteries but most of those seem to use evaporative moisture so that’s a no go and if they don’t it’s just more power consumption or maybe ineffective (cool breeze?)

At best I’d just like to keep the batteries under the 113 operating range so they can charge all day. At worst I’d like the BMS to safely shut them off and lose some hours of daytime charging. Also are there any recommended fail safes?

Here’s my system 500w renogy solar, 40a mppt renogy charge controller, 200ah battery to be determined, 900watt xantrex inverter connected to 45w 12v fridge and a secondary charger charging the old 100ah lithium ion (SmartBattery brand) if it sounds safe under the circumstances, or new lifepo4 if that’s a better option?

Thanks so much for taking the time with my post!

A low tech but effective solution for a van that would lower the temperature to below 100 degrees F. would be to shade the vehicle with cheap reflective tarps that you can buy in any hardware store. If you can create an offset that prevents the sun from striking metal surfaces the temperature inside the vehicle will be greatly reduced. I would use four reflective tarps and lots of solar panels on the top.

 

[DIYVan]

Old thread, but tint all your windows, windshield included. Most of the heat input into car/vans will be through the windows, especially if you have the roof covered in panels already. A 70-80% VLT ceramic tint is almost invisible and will cut down on UV and IR ingress dramatically. Darker will help even more.

 

[curiouscarbon]

solar heat gain from windows to interior requires more energy to reject said heat flux, nice

 

[Capt Bill]

I'm going to experiment with one of these as it gets hotter down here in Baja. Hoping I can hard wire it to a 12 volt panel for daytime only use. If it gives me problems I will run a small battery inline and manually disconnect in the evening. It does cool pretty well from my early battery only connection.

https://www.amazon.com/Semiconductor-Refrigerator-Refrigeration-Thermoelectric-Peltier/dp/B07TQHH6Q1/ref=sr_1_30?crid=36C6UQBTONBZP&keywords=thermoelectric+peltier+refrigeration+cooling+system+kit+cooler+diy&qid=1649421978&sprefix=Thermoelectric+Peltier+Refrigeration+Cooling+System%2Caps%2C118&sr=8-30

View attachment 90395

Wondering how this experiment performed for keeping your set of LifePO4s cooler in a hot car, or battery room that may be also heating up from the All In Ones (or other solar equipment) near one's batteries . ??? Any further report from a few months later will be appreciated.

 

[littleharbor2]

Wondering how this experiment performed. ... Any further report will be appreciated.

From a similar post of mine elsewhere on the forum. BTW it's working great. The cooling unit is kind of an energy hog but being that I have a dedicated panel, controller and battery running it it really isn't dragging my lithium's down.

Figure I'd add what I have done to my LiFePo4 230ah 2s8p bank to help in the summer. I purchased this 12 vdc refrigeration unit and digital thermostat . It seems to be working fairly well. I do have a dedicated 12 volt solar panel, controller and battery powering the unit. It's pretty humid here in the summer so I had to create a waterproof chute to get the condensation out of the battery box.

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1 x NTC sensor (3m cable). For example, If you choose Heat mode(Set HC to H). Set Temperature Value to 80°F. Set d value to 20°F. The relay will be connected when the temperature drop to 60°F(set temperature value-d value).
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