Installing 2 balmar 170s w/mc618s on two engines without centerfielder. How do i avoid yo-yo-ing with volt sensor
Balmar XT-CR-170-K6-KIT alternator kit with Max Charge regulator
I'm replacing alternators on a catamaran, on both engines. The old OEM alternators charged the start batteries only. Now I am putting in balmar XT-CTR-170s with mc-618 regulators, plus APMs, and directly charging the house bank. I have a 12v victron LFP house bank (5 x SmartLithium 12v 200Ah from 2022) with victron lynx BMS and cerbo, and using the trickle charge output of the multiplus ii to keep the start batteries full from the house bank.
I understand people are no longer using the balmar centerfielder because it's not needed so much with LFP batteries. How do I connect the mc-618 voltage sensor so that i won't get "yo-yo-ing" when both alternators are going? If one alternator is running and then the second one comes online, i want the second one to also charge the batteries, instead of sensing the first one's charge voltage and deciding to not charge. Does connecting the voltage sensors directly to a battery help, versus at the lynx bus or elsewhere?
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Open Jun 10, 2026 - 11:16 AM
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Staff Answer
Jun 10, 2026 - 11:16 AM
The voltage sensors should go to the battery directly, or failing that as close to the battery as you can get. Lithium batteries dont change their voltage much when on charge. The voltage may only rise 0.2 volts or so when you start charging, so both regulators will do whatever you programmed them to do. Over the course of the charge cycle the voltage will slowly rise but it is only at the very end as the batteries reach their full point that the voltage will rise to near the set point. That only happens right at the end and so it doesnt matter at that stage if one or the other alternators drop out.
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