You have it right if you are talking about an echo charger. The simplest explanation is that the echo charger is a relay that closes based on the differential of voltage between the two battery banks. It allows a controlled amount of current (Max 15A in the case of the one I use to charge the battery under the v-berth) to flow in only one direction. So you wire it with charging source on the house bank, and when the start battery is low and the house is charging the relay closes and delivers part of the charging current to the start battery. Start bank high and house bank low, the relay remains open.
An ACR is a bi directional device that also closes based on voltage differential between the two banks. If house is high and start low, the current flows to the start battery. If start is high and house low, the relay still closes and current flows from start to house. The Blue Seas ACR I did not use in my system will pass up to 120A between the batteries based on the voltage differential, so I really would not characterize it as a “controlled current” device. If the voltage differential is too great, the Blue Seas ACR will not close, which prevents current flow if one of the batteries or cables is shorted. I think of a battery combiner as a temporary switch that puts the two banks in parallel regardless of the voltage differential. In effect it is an electronic alternative to the ALL position on the traditional 1-ALL-2 battery switch. And in answer to another question about the impact of an ACR or echo charger on a two bank charger: since the relay closes on voltage differential, and both legs of the charger start out at essentially the same voltage, there shouldn’t be a great differential and the relay shouldn’t close while the charger is running. YMMV, since the software that controls the output current and voltage of each leg of the charger can vary by manufacturer. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of John Pennie via CnC-List Sent: Wednesday, April 06, 2016 8:14 PM To: cnc-list@cnc-list.com Cc: John Pennie <j...@svpaws.net> Subject: Re: Stus-List Automatic Charging Relay So if I understand this correctly it isn’t a 2-way street. When a charging source is connected to the house bank the rise in voltage will close the solenoid and the two bank are now joined. The voltage “sensor” is only on the house bank side. So if the starting bank is at 14 volts and the house bank is at 12v the circuit will remain open and the banks will remain isolated. Do I have this right? John
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