Protecting Lithium batteries from charging at low temperature.

[PeteS]

Ive been looking to find away to stop a Victron Orion Tr B2B charger charging LiFePO4 batteries below 0C and I think Ive finally settled on a method.
Ive been playing with a W1209 Digital Thermostat to control the B2B via its high input. To my delight the settings are stored in non-volatile memory when the unit is switched off. In other words it remembers its settings so on next power on it just carries on.

This means it can be powered by a D+ signal and the relay contacts can pass the D+ to the H input on the B2B thus enabling it to charge.

The current consumption with the relay on is around 75mA which is higher than specified and whist not significant if in daily use, in storage over winter it could be significant if coupled with an alarm and other kit.

Seems to work a treat so far, I have it set to 5C, it would have stopped charging last night!

 

[wildebus]

Ive been looking to find away to stop a Victron Orion Tr B2B charger charging LiFePO4 batteries below 0C and I think Ive finally settled on a method.
Ive been playing with a W1209 Digital Thermostat to control the B2B via its high input. To my delight the settings are stored in non-volatile memory when the unit is switched off. In other words it remembers its settings so on next power on it just carries on.

This means it can be powered by a D+ signal and the relay contacts can pass the D+ to the H input on the B2B thus enabling it to charge.

The current consumption with the relay on is around 75mA which is higher than specified and whist not significant if in daily use, in storage over winter it could be significant if coupled with an alarm and other kit.

Seems to work a treat so far, I have it set to 5C, it would have stopped charging last night!

well, if it is powered by the D+ signal, would it use any power when the engine is not running? so that would be a factor to worry about?
If there was an additional power source needed, that could come from an ignition-controlled line, so again, only present when ignition on (so again, when parked up, no power drain as it needs no power for anything until the engine is running )

 

[PeteS]

well, if it is powered by the D+ signal, would it use any power when the engine is not running? so that would be a factor to worry about?
If there was an additional power source needed, that could come from an ignition-controlled line, so again, only present when ignition on (so again, when parked up, no power drain as it needs no power for anything until the engine is running )

Yes there was a bit missing from my post, the point being if you use D+ then there is no drain when the engine is not running, no other power sources required. So all good

 

[Chris Evans001]

Yep, protection definitely needed here last night... I woke up to these messages this morning.Brrrr.

 

[HarryW]

Silly question, does too low a temp just prevent charging? I’m presuming you can still draw current from them?

 

[Chris Evans001]

Silly question, does too low a temp just prevent charging? I’m presuming you can still draw current from them?

Yes you can still draw power out but my charger completely cuts any charging below zero deg c. Pretty sure it charges at a lower rate between 5deg and 0deg as well.

 

[wildebus]

Yes you can still draw power out but my charger completely cuts any charging below zero deg c. Pretty sure it charges at a lower rate between 5deg and 0deg as well.

That is pretty good And with the Readarc BMS30 (not to be confused with lithium battery BMS's for anyone reading this ) handling all charging sources, full protection there

Little question ... do you know if you can set a charge cutoff temp below zero? Just thinking how the BMS30 would work with a battery like the Poweroad SubZero (and a couple of other Lithiums) which allows charging to continue below zero, and rely on those batteries BMSs to do the cutoff?
(I suppose you could just disconnect the battery temp sensor in those cases?).

Anyway, good to see it has that built-in feature. I find it remarkable the Victron Mulitplus knows a battery temp, can set to Lithium but still cannot set a cut-out temp but have to mess around with assistants.

 

[Chris Evans001]

That is pretty good And with the Readarc BMS30 (not to be confused with lithium battery BMS's for anyone reading this ) handling all charging sources, full protection there

Little question ... do you know if you can set a charge cutoff temp below zero? Just thinking how the BMS30 would work with a battery like the Poweroad SubZero (and a couple of other Lithiums) which allows charging to continue below zero, and rely on those batteries BMSs to do the cutoff?
(I suppose you could just disconnect the battery temp sensor in those cases?).

Anyway, good to see it has that built-in feature. I find it remarkable the Victron Mulitplus knows a battery temp, can set to Lithium but still cannot set a cut-out temp but have to mess around with assistants.

Redarc can apparently supply a different battery temperature sensor with a a lower setpoint pre programmed.
I read an article where the manager 30 was used on a polar expedition with air temperatures never expected to rise above zero even in the daytime. The batteries were mounted in an outer locker so the temperature sensor had a charging cutoff point of -24 deg c !

Certainly never seen anything programmable in the menu options on the manager 30.

It is pretty incredible that with Victrons pedigree, something similar isn't built into the multiplus. Perhaps they are working on an add on product!

 

[wildebus]

That is good. Maybe too many user options can result in the wrong settings being made so they went for hardware differences to make the change?

Victron have an assistant you can add in and combine that with a BMS unit you add on (and costs three figures).
But all their MPPTs have a simple checkbox option you set if you want to disable charge below 5C! surely that is the way to go and very simple to support natively on the MPPT (and other chargers that know about temp).