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Low Temp Cutoff Question

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stlwx21

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Nov 9, 2021
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Greetings all!

I was looking at a cheaper 100ah Amazon lithium iron phosphate battery and it doesn't have low temp cutoff. The battery will be used to power the trolling motors on my small boat.

Can you somehow rig up low temp cutoff with only the Victron Smart Shunt and its temperature sensor? I don't think this is possible but not 100% sure.

My other thought was to provide an alternate source of power to a Solar Controller, but not confident in my abilities to this.

Any feedback, thoughts, suggestions would be appreciated.
 
What will you be using to charge the battery? Some charge controllers, such as the Victron line, have a setting to stop charging below a set temperature. It can get the temperature from the SmartShunt.
 
Currently, I have the Victron Energy Blue Smart IP65 charger - the 15a version. I can still return it if I want.
 
So I guess you take the battery out of the boat and connect it to the charger when needed. So why worry about charging when too cold? Just don't charge the battery when it's too cold.
 
I may well end up doing that - and that's perfectly fine. I wanted to see first if there was a set it and forget it option. :)
 
For a charger like that you could use a thermostatically controlled outlet to ensure the charger is disconnected from power if it gets below a certain temperature in the room.
 
We use automatic on outlets all the time here in the north country. Something like this.

In a situation like yours you would put the battery and sensor outlet in a smallish space (maybe a large cooler) with a incandescent light bulb connected to the thermostatically controlled outlet. This will keep a small space’s temperature between the set points of the thermostat. I’m sure someone makes a device that turns off around freezing but it’s not common to need to do that. If it was me I would just charge the battery up and store it and try to remember to top it off before boating. It should still have most of it’s charge after several months and it’s generally better not to keep a lifepo4 battery fully charged when not being used anyhow
 
I have the same question , in my case , the boat is in a boat lift , always on the water. I need the power to the charger to shut down in
freezing weather, Or something wire in between the charger and battery.
thanks
MO
 
One problem with a device to shut of a charger at low temperature is that if it turns back on before tha battery warms up enough you haven’t solved anything. Depending on the location of the battery it might take many days for a cold battery battery to warm up inside unless the temperatures around it are way above freezing.
 
So buying a cheaper battery with no low temp shutdown and then buying a device to do that makes sense how?
How much is that new 100Ah SOK? $300?
 
I'm not aware of any $300 SOK battery.

As I mentioned earlier in the thread, I will likely end up bringing it inside if it gets brutally cold. I'm in Texas so shouldn't need that often if at all. With the real cold weather last week it dropped between 15 and 20 degrees at night, however in my garage it never got colder than 45.
 
Last edited:
rmaddy said:
The 12V 100Ah SOK battery is currently $570.
Click to expand...
….and 100Ah usable (maybe) lead acid in cheap batteries is $200-ish

It’s getting harder and harder to not consider LiFePo in a lot of situations. Cheap lead batteries really need to last 5 years to make sense (unless upfront cost is the driving factor or charging in freezing temps is required).
 
Low temperature thermostats are available in the UK, and I expect other countries, simple mechanical low temperature thermostats that switch on, or switch off, at low temperatures. I use the devoice in the link below as a master override should other low temperature sensors in the system fail, ( device has a change over contact set, rated at several amps AC, totally mechanical)

Heating Accessories - CorgiDirect

Heating Accessories
www.corgi-direct.com www.corgi-direct.com

frost stat.jpg
Mike
 
12VoltInstalls said:
And this works/is rated for cutoff of DC volts/amps?
Click to expand...
The contact set world work for low voltage and current control inputs to disable chargers, power relays or control the AC power to chargers.
The idea to to use it as a control device, not to directly cut DC charge currents to the battery.

Mike
 
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