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Lithium LiFePo DC charger 712 BMV renogy

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#1 RHarries

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Posted 31 October 2023 - 02:19 PM

I recently swapped out my dying AGM battery power for a single  Renogy 100 Ah LiFePo battery with self heating function.  My power system also includes a Victron 712 BVM (with temperature sensor), Victron MPPT, and Victron Orion DC charger.

 

Everything worked perfectly this summer, yet now that temperatures are dropping I want to make sure that I don't damage the new battery by charging at freezing temperatures.

 

I have the BMV low temperature relay set to 3 degrees Celsius.

 

I noted that the solar charger was not charging yesterday during freezing (2 C) temperatures, however when I started the truck, the DC charger initiated charging the battery.  I do not see that the DC charger has the ability to monitor temperature and adjust its charging program.

 

I believe all is wired correctly. All positive leads (solar, DC charger, Iota, etc.) to a BUS bar with a single 2 AWG to the house battery, and all negative leads to the 712 shunt with a single connection to the house battery negative terminal.

 

Finally my questions:

Should the DC charger be charging the battery even though the shunt relay is set to limit charging at low temperatures?

 

I am unclear on how the "self heating" function of the battery is supposed to work.  (there is very little info from the vendor available)

 

Thanks,


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#2 Jsoboti

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Posted 31 October 2023 - 02:41 PM

If the battery is self heating, it will have a temp. sensor inside the battery. Below a threshold temp. which I think is 41F for the Renogy, the current going into the battery (either from solar, DCDC, IOTA, Etc.) will be used to power the internal heating pads, not charge the battery. Once the internals of the battery are warm enough, the current will be used for charging. 


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#3 Taku

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Posted 31 October 2023 - 10:35 PM

We have a Battleborn with no heater and it has worked fine through one winter with below zero temps. Will see how it goes over time


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#4 Vic Harder

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Posted 31 October 2023 - 10:36 PM

@RHarries, as Jsoboti indicated above, your self-heating batteries are ok and will not accept a charge unless warm enough.  I have played around with this to create a battery warming system for mine, since my Battleborn's are not self heating.  

 

The "cold relay" function sets a temperature in the BMV where it can operate a relay.  The relay output is on the back of the BMV.  

 

The various Victron components do NOT talk to one another unless they are networked with more Victron tech, like their Cerbo units.  (unless I missed something?)

 

Vic


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#5 dennis 221

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Posted 01 November 2023 - 05:40 PM

So??? Either lithium or agm ?? When u run a trickle charger on them does that not keep the battery warm so it would take a charge in a our cold Northern winter's??!
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#6 Vic Harder

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Posted 02 November 2023 - 01:51 AM

So??? Either lithium or agm ?? When u run a trickle charger on them does that not keep the battery warm so it would take a charge in a our cold Northern winter's??!

Not sure exactly what you are asking Dennis... in the OP case, he has heated lithium batteries, and is golden with that setup.  And yes, trickle charging can warm the battery, but lithium batteries have such a slow self-discharge rate that it has no effect.  Plus it is more ideal to store lithium batteries partially discharged, say 50-80%, and NOT on a trickle charge.

 

I just came back tonight from 10 days in BC with nighttime temps in the -10*C range, and the batteries were constantly plugged in and charging.  Because my batteries are in the living area, they rarely get cold while the camper is in use.  


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#7 RHarries

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Posted 02 November 2023 - 01:37 PM

Thanks all.  Now that the cold snap has stalled, the battery has quickly recharged from solar gain. 

 

It is comforting for me to know that both  the Victron BMV and Renogy battery have mechanisms in place to protect the power storage system.  I like having redundancy to protect the expensive battery!

 

FWIW, the BMV low temperature relay default setting is 5*C, which aligns with the 41*F Renogy cutoff mentioned by Jsoboti. 


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