# How do the H and L terminals of the Orion-Tr Smart DC-DC Charger interact with each other?

**URL:** <https://community.victronenergy.com/t/how-do-the-h-and-l-terminals-of-the-orion-tr-smart-dc-dc-charger-interact-with-each-other/46103>\
**Category:** DIY\
**Tags:** orion\_dc-dc\_convert, orion\_smart\
**Created:** [27 September 2025 17:59 UTC](https://community.victronenergy.com/t/how-do-the-h-and-l-terminals-of-the-orion-tr-smart-dc-dc-charger-interact-with-each-other/46103 "2025-09-27T17:59:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![nagmat84](https://avatars.discourse-cdn.com/v4/letter/n/cab0a1/32.png) [@nagmat84](https://community.victronenergy.com/u/nagmat84)\
**Post date:** [27 September 2025 17:59 UTC](https://community.victronenergy.com/t/how-do-the-h-and-l-terminals-of-the-orion-tr-smart-dc-dc-charger-interact-with-each-other/46103/1 "2025-09-27T17:59:19Z")

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How do the H and L terminals of the Orion-Tr Smart DC-DC Charger interact with each other? I read the manual and have the impression that some of the information are seemingly contradictory or maybe incomplete.

1. The [manual, sec. 4.7 “Remote On/Off”](https://www.victronenergy.com/media/pg/Orion-Tr_Smart_DC-DC_Charger_-_Non-Isolated/en/installation.html#UUID-1d0b7037-0f0f-b309-ed1c-88806e73ac05) states that the charger can be switched _on_, when the H terminal is pulled up above 3V, and switched _on_, too, when the L terminal is pulled down below 5V.
2. The manual, sec. 4.8 “Engine shutdown detection override” states that engine shutdown detection is overridden, when the L terminal is pulled up above 7V.

This confuses me. In my words, overriding the shutdown detection means to keep the charger on. Hence, in other words, item 2 says the charger remains _on_ when L is _pulled up_, and item 1 says the charger is turned _on_ when L is _pulled down_. How can both be correct?

For other Victron products, pulling down the L terminal actually means to switch the product _off_. (For example see the [Phoenix Smart IP43 Manual, sec. 5.2.2 Remote On/Off](https://www.victronenergy.com/media/pg/Phoenix_Smart_IP43_Charger_120-240V/en/installation---bsc---psc.html#UUID-66d65ec8-8cbf-85fb-73fc-ec687b27840a)). This makes me wonder whether item 1 above might be wrong and the statement should read the charger is switched _off_, when the L terminal is pulled down below 5V. This would make more sense for me.

Some other question related to this topic:

1. Assuming 1 and 2 above are both correct and both terminals allow to switch the charger _on_, is there any option to forcefully shut if _off_ remotely, even if the charger detects a running engine?
2. What happens if both terminals L and H are connected? Which one takes precedence?

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**Author:** ![M\_Lange](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/m_lange/32/16_2.png) [@M\_Lange](https://community.victronenergy.com/u/M_Lange)\
**Post date:** [28 September 2025 17:14 UTC](https://community.victronenergy.com/t/how-do-the-h-and-l-terminals-of-the-orion-tr-smart-dc-dc-charger-interact-with-each-other/46103/2 "2025-09-28T17:14:50Z")

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Connecting \>3V to H or pulling L to GND will put the Orion in “standby mode” and it is waiting that the input voltage meets the configured voltage in the “input voltage lock-out” AND “Engine shutdown detection”.

Connecting \>3V to H AND \>7V to L will override (ignore) the “Engine shutdown detection” and the Orion will only work with the “input voltage lock-out” setting.