Battery Protect with temp sensor

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smartupfitters asked Apr 21, '24

Battery Protect with temp sensor

Long story short,, I have to use this 150ah battery - it's the only one I can find that fits in the space available. The problem, it does not have low-temp protection in its BMS.

The Battery Protect (BP) is going to cutoff both the charging and the loads for the battery, when the Victron BMV TEMP sensor goes below 40 degrees. The thermal sensor needs 12v to operate and needs to live in the battery compartment. The issue, if the aux battery is completely dead, the Temp-sensor/BMV will never close the BP. Also, the Charge sources needs to feed the load, when the battery is dead.

Remedy, a supply from the Charge sources will be connected to the Temp-sensor/BMV within the battery compartment. And both loads and sources will be place on the "IN" of the BP.

Question, does this all seem like an okay design? Is there an issue running both loads and charging sources from the "IN" on the BP

BMV Battery Monitor Battery Protect Temperature Sensor

battery-protect-circuit.png (135.8 KiB)

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snoobler answered · Apr 22 at 12:21 AM

https://www.victronenergy.com/battery_protect/battery-protect

The BatteryProtect is a uni-directional device. It can only deal with current in one direction, so either current to a load, or current from a charger, but not both currents at the same time.

you need a separate one for discharges/loads and an inverter can't be part of the load, i.e., you can't use a BP to connect/disconnect the DC supply of an inverter. You will damage the BP.

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Modifications Space

Node Red Space

Answer 1 · 2024-04-22T13:47:40Z

smartupfitters answered · Apr 22 at 01:47 PM

Would the two BP's be put in series, with reverse input/output? See crude sketch
One BP would protect for loads, the other for supplies??

img-1523.jpg (546.6 KiB)

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Answer 2 · 2024-04-22T15:21:10Z

snoobler answered · Apr 22 at 03:21 PM

No. Separate parallel circuits. The way you have them has both BP passing current in both directions.

Battery > BP IN > Loads

Sources > BP IN > battery

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smartupfitters commented · Apr 22 at 04:02 PM

Thanks Snoobler, but would separate parallel circuits allow for supply to the load, during cold temps?

oh,, like this?

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img-1524.jpg (1.2 MiB)

pwfarnell smartupfitters commented · Apr 22 at 04:33 PM

No, you have a connection between loads and chargers, remove this, now you have parallel circuits.

However, now you can not supply the loads with the chargers if the BP stops charging.

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76588-img-1524-kindlephoto-238263106.jpg (793.2 KiB)

Answer 3 · 2024-04-22T16:10:10Z

smartupfitters answered · Apr 22 at 04:10 PM

Would this damage one of the BP, when the current is running the opposite direction?

Victron Manual: " a reverse current may flow that damages the SBP"

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Answer 4 · 2024-04-22T16:21:42Z

smartupfitters answered · Apr 22 at 04:21 PM

Looks like Victron recommends wiring the BP's in serie for Loads and Sources

1654cceb0b0f8a.png (76.4 KiB)

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snoobler commented · Apr 22 at 04:25 PM

Nope. That's parallel and separate. It's just using the "IN" on the loads BP as a connection point. The circuits are separate, i.e., if one triggers, the other will not pass the current.

In your sketch, the parallel connection to the right of both BP means that BOTH BP have to trip to stop any current in either direction.

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Answer 5 · 2024-04-22T16:26:20Z

smartupfitters answered · Apr 22 at 04:26 PM

.. but this would disconnect the CHARGE from the LOADS. No one could run any devices in the cold, even though Orion is ready to supply 30a while driving. I think I'm giving up trying to use the BP as a substitute for a BMS without low-temp protection.

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Answer 6 · 2024-04-22T16:29:40Z

smartupfitters answered · Apr 22 at 04:29 PM

and one more thought for anyone who's really wanting to make this work. A third BP could connect Charges (supply) and loads and be NO (closed when cold).

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