Buck-Boost with ACR?

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usmc-mustang asked Nov 27, '20

Buck-Boost with ACR?

I have an RV with an existing AGM auxiliary battery connected to the starter battery via a Blue Sea Automatic Charging Relay (ACR). Both are charged via the 220A engine alternator, with the ACR determining which battery requires charging. I have added additional house batteries (LFP) in a separate location and would like to also charge those via the alternator, using a 50A Buck-Boost DC-DC charger (see diagram).

My question is: When connecting the Buck-Boost to the starter battery in accordance with the instructions, how does this affect the existing interface between the starter batter, the ACR, the alternator, and the existing aux battery? In other words, can I leave the ACR in place and simply connect the Buck-Boost to the starter battery per the instructions?

Lithium Battery

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Answer 1 · 2020-11-28T01:11:22Z

rodneyab answered · Nov 28, 2020 at 01:11 AM

yes. There may be times arise when you need to disconnect via the ACR. When you charge the Lithium from your starter battery, if your ACR is latched on, you will be charging off both batteries. If you latch off the ACR, you will charge the Lithium from the starter battery only, which is preferred. If by chance you choose to charge your Auxilliary AGM with an outside source, and your ACR is latched on, and your DC-DC charger is on, you will be charging your remote lithium house battery, which you may not want to do.

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Answer 2 · 2021-02-24T16:27:04Z

usmc-mustang answered · Feb 24, 2021 at 04:27 PM

Friends:

To re-start this discussion, I continue to be frustrated by my Victron Buck-Boost 50a installation. Most recently I’ve removed the ACR altogether and connected the Buck-Boost to the same ground (negative) as the other batteries. When running, the Buck-Boost input (from the starter battery) is 14.1v and the output (to the LFP bank being charged) is 14.2v. That SEEMS to suggest everything is working properly, yet I cannot get any amps to flow. The voltage on the LFPs is 13.2 and they are NOT charging from the Buck-Boost.

Any idea what I’m (continuing to) doing wrong? Is there a way to simply test the Buck-Boost to verify that it’s not broken or malfunctioning?

Many thanks,

Steve

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over-and-under-victron commented · Oct 19, 2022 at 01:55 PM

Doing some research and was curious if you ever figured this out?

Should we have an expectation that Victron weighs in on questions like this? Or is this simply a user only forum without the expectation of help from Victron?

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Stefanie (Victron Energy Staff) ♦♦ over-and-under-victron commented · Oct 19, 2022 at 02:42 PM

See: https://community.victronenergy.com/questions/5889/new-victron-community-guidelines.html

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