Batteries Won't Charge with Battery Charger

[crquisto]

I had to replace all three batteries on my 405. Now Battery 1 and Battery 2 will not charge using the Battery Charger, either off of Shore Power or Generator Power. I think the Generator battery is charging, but since it carries none of the house load, I'm not really sure. As part of another problem (see "Battery Blowup" in this section) I tested the volts out of the charger per the tech support people guidance, but whenever I leave the boat sitting with anything on and the Battery Charger on with about 20 amps showing on the charger, the batteries still drain. By jumping them, I can start my engines and then charge the batteries, but that shouldn't be required. Any ideas on checking out my problem, and also, do I really need to select only 1 or 2 with the engines running and not BOTH as the manual says?

[waybomb]

On my boats the charger connects directly to each battery. As does the bilge pumps. My battery switch is always off when I leave the boat. When I am running I run on one only. Either 1 or 2.
Not saying that what I do is correct but it had worked for me for over 20 years.

[Ondercin]

How old is the charger? I just replaced our original charger (1988) with a brand new 30amp 3 bank charger and it works amazing... After winter storage the charger wouldn't get the batteries up to full charge and after putting a car charger on them for a coupe days they went to 100%.. I put the batteries back on the boat charger and after a couple weeks the engines couldn't start due to weak batteries.
Since replacing the charger everything has been great!

[Ramsport47]

There should also be 3 circuit breakers labelled "battery charger" that need to be in the on position. These are usually by the batter switch (es)

[feeez]

In our boat the battery charger is connected to the batteries in the same manner as Ramsport suggest. There are three breakers one for each battery bank. Carver also says as you do that the battery switch should be on 1 or 2 and only "both" when either battery will start the engine. I have found that unless my battery switch is set to "both" the batteries don't get charged properly while connected to shore power. I have a feeling that there may have been some "rewiring" done in the past. I took a look behind that panel in the salon..... yuck what a mass of wire back there.

On my boats the charger connects directly to each battery. As does the bilge pumps. My battery switch is always off when I leave the boat. When I am running I run on one only. Either 1 or 2.
Not saying that what I do is correct but it had worked for me for over 20 years.

[waybomb]

There's Fuses between pumps & charger and batteries but it is a direct link to battery power. Actually I believe the connection is at the back of the battery switch where the main cables connect to the switch not going through the switch.