I assume you are thinking of buying the Blue Sea Systems BatteryLink battery charger model 7605. Compare at
https://www.bluesea.com/products/7605/B ... nk_ChargerThis is a fairly new product from Blue Sea Systems. I think it is a great product. Here are some excerpts from the manual about this device:
--begin excerpts--BatteryLink® Charger FeaturesThe BatteryLink® Charger is a 120VAC/230VAC nominal input, 12VDC nominal output, 10A battery charger with integral battery combiner (ACR) providing a second battery connection, as well as standard ACR function when AC power is not present.
• AC plug-in at the dock, provides 10 Amps of charge current
• Integrated ACR automatically combines batteries during charging, isolates batteries when discharging and when starting engines
• Start isolation protects sensitive electronics from voltage sags and spikes
• Battery temperature compensation prolongs battery life
• Supports alternators up to 65 Amps
• One-piece stainless flange nuts ensure safe and secure connections
• Ignition protected—safe for installation aboard gasoline powered boats
• LED light is ON when batteries are combined
• Includes a remote indicator LED with mounting bezel
• Snap-on insulating cover
Automatic Three Stage ChargingThe BatteryLink® Charger uses a three stage automatic charging profile. The three stages are referred to as bulk, absorption, and rest/float. The charger will move between these stages automatically, with no user intervention. When the charger starts, it goes first to the bulk stage. This is where the first 75% – 80% of charging takes place. It is a constant current mode, in which the charger outputs as much current as it can to drive the voltage of the battery up to the absorption voltage. Once the absorption voltage is reached, the charger enters absorption mode. This is a constant voltage mode, in which the battery is held at the absorption voltage to complete the last 20% – 25% of charging. In the absorption stage, current will decrease according to the Batteries’ needs plus any additional current required for active loads. The length of time spent in the absorption stage will vary based on battery type, battery capacity, and the presence of loads, but will be a minimum of 1 hour up to a maximum of 5 hours. After the absorption stage, the charger will move to the rest/float stage. The float stage is a constant voltage mode intended to maintain fully charged batteries while supplying current for loads as necessary. The rest mode is included as an energy saving mode, and for compliance with California Energy Commission (CEC) requirements. In the rest stage, the charger output and ACR are turned off to conserve energy, and the battery voltages are monitored. If loads or self-discharge on either battery cause the voltage to drop to 12.9V, the charger enters float mode for 4 hours in order to maintain the battery and supply current to loads. After seven days of continuous rest/float mode, the charger will repeat the normal charge cycle to assure good battery health.
Battery Temperature CompensationBattery temperature compensation is output voltage regulation based on battery temperature variances. Since batteries can see extreme temperature differences, it is important to regulate output voltage with temperature to maximize battery life. A battery in a cold environment should not be charged at the same voltage as a battery in a hot environment. The BatteryLink® Charger is set at a baseline of 25°C. If the included battery temperature sensor is installed, then every 5°C variance from this baseline will result in a change in output voltage. Voltage will decrease at higher temperatures, and increase at lower temperatures. The temperature sensor also allows the charger to react to extreme hot or cold temperatures (below 0°C or above 45°C) by reducing output or shutting down to preserve the battery. Reference the Installation Instructions on page 6 and the Full Installation Diagram on page 8 for details on how to install the battery temperature sensor.
Automatic Charging Relay (ACR)The BatteryLink® Charger includes an integrated 65A Automatic Charging Relay (ACR). The purpose of an ACR is to combine batteries for charging, but leave them isolated for discharge. This works well with dual battery systems, where non-starting loads are isolated from the engine starting battery to reduce the risk of being stranded on the water without enough power to start your engine. The ACR in the BatteryLink® Charger will combine the auxiliary and start batteries at or away from the dock. This means both batteries will be charged during AC powered charging, or when AC power is not available and a secondary charging source is active, such as your engine’s alternator. The ACR includes an optional Start Isolation feature, which can be used to prevent engine starting current being drawn from the auxiliary battery. Start Isolation protects sensitive electronics wired to the auxiliary battery from being affected by voltage sags or spikes caused by engine starting. Reference the Installation Instructions on page 6 and the Full Installation Diagram on page 8 for details on how to wire the Start Isolation feature.
--end excerpt--I really like this product for the following reasons:
--the battery charger is more sophisticated than the typical marine AC-operated charger; it has multi-stage charging profiles and temperature compensation; both features are advancements over the usual constant-voltage non-temperature-compensated simple charger;
--wiring to the battery terminals is simplified because the charger circuit and the ACR circuit use the same leads; this reduces the number of connections to the battery terminals; simpler wiring and less wiring are always advantages on small boats;
--the cost is appropriate for the two products provided in one assembly; it would be hard to find a charger with these features and an ACR for the same total cost.
Therefore, although I cannot meet your requirement for having first-hand experience with this product, it does looks like a very good solution for charging two batteries from both AC and DC sources on a small boat.
Also, I think you will want to still get the battery switch to control the primary power distribution from the batteries. The recommended model 6011 would be a good choice. Compare at
https://www.bluesea.com/products/6011/m ... itch_-_RedI have been using the larger 5511e model for several years. I chose that size to fit with the existing holes for mounting it. I also have an E-TEC engine, but it is a V6 and I have added the auxiliary charging kit. These eliminates the need for a combiner relay.