Acouple of months ago I posted a question regarding batteries and the 3 position switch. That problem was solved. I noticed the other day that the shore power charger was draining a small amount of current from the starting battery. The boat is on a morring and nothing was on. So do I need to put a diode between the battery and the shore charger or is there another issue. The battery is wet cell and the charger is a Xantrex true charge (20 amp). Thank you for any insight.
do I need a diode
- Thread starter orion
- Start date
- Status
What's the link to the last discussion? (we can't remember like you can) and how do you know you have a "drain" when there's no connection that's "on"? BTW, I have never heard of having to need a SEPARATE diode on a charger when two banks are connected and the charger's off.
Last edited:
A diode will result in an always undercharged battery when using the shore power charger as almost 1 volt will be lost crossing the diode. Better would be a 25 -30 amp circuit breaker (depending on your charger output and wire size) between the charger and the battery. Just leave the breaker(s) off until plugged into shore power. I have a three bank charger that I installed a separate breaker on each leg to the batteries. That way there is no backflow to the charger electronics. Alternatively, you can buy a small solar panel on ebay to counter the parasitic drain of components.
Allan
Allan
What happened was the refrigerator was on and the battery switch was on #2. Somehow battery #1 was drained of power also. The only way for the electicity to get out was back through the shore charger. When testing the switch I had a small amount of current drain on #1 when the switch was on #2. When the shore charger was disconnected the power drain was stopped. What do you make of it?
Charger hook up wrong
In a 3-way switch configuration the charger hooks to the common post and you use the 3-way to control which battery bank(s) get charged. If you hook multiple lines to either the battery banks themselves or the 1 and 2 posts of the 3 way you are effectively bypassing the 3-way.
Current flows from the "off" bank through the battery charger + cable to the charger then enters the other bank + cable at the charger and then to the bank that is connected to the loads.
Some chargers have isolation diodes between the + cables and some don't. you can test by disconnecting the charger + cables and seeing if there is a circuit between the cables (+ to +) in both directions. If there is a circuit then you need to wire as above to the common post of the 3-way. If there is no current then you can wire it any way you want as they are already isolated.
FWIW
In a 3-way switch configuration the charger hooks to the common post and you use the 3-way to control which battery bank(s) get charged. If you hook multiple lines to either the battery banks themselves or the 1 and 2 posts of the 3 way you are effectively bypassing the 3-way.
Current flows from the "off" bank through the battery charger + cable to the charger then enters the other bank + cable at the charger and then to the bank that is connected to the loads.
Some chargers have isolation diodes between the + cables and some don't. you can test by disconnecting the charger + cables and seeing if there is a circuit between the cables (+ to +) in both directions. If there is a circuit then you need to wire as above to the common post of the 3-way. If there is no current then you can wire it any way you want as they are already isolated.
FWIW
It All Depends on How It's Wired
MOST boats with multiple output chargers have been installed with the multiple outputs of the chargers wired to the battery banks directly from the charger, rarely from the the charger to the 1 & 2 posts of the switch (which woudl be exactly the same electrically).
That's so people could turn the 1-2-B switch to OFF when they leave the boat and still plug in and charge their batteries. If it was as you described, people would have to leave their 1-2-B switches ON to charge their batteries..
It is imperative that the owner check out the wiring to find out how it is ACTUALLY installed on HIS boat, and NOT take our word for ANYTHING, because assumptions about wiring are very dangerous.
Bill is also ABSOLUTELY correct about the isolation diodes in the charger in the second part of his post.
With all due respect, that's nonsense. See the heading to this post. Most boats unfortunately have their alternator outputs (not charger outputs) on the C post of the 1-2-B switch, which results in what you've described, Bill.
MOST boats with multiple output chargers have been installed with the multiple outputs of the chargers wired to the battery banks directly from the charger, rarely from the the charger to the 1 & 2 posts of the switch (which woudl be exactly the same electrically).
That's so people could turn the 1-2-B switch to OFF when they leave the boat and still plug in and charge their batteries. If it was as you described, people would have to leave their 1-2-B switches ON to charge their batteries..
It is imperative that the owner check out the wiring to find out how it is ACTUALLY installed on HIS boat, and NOT take our word for ANYTHING, because assumptions about wiring are very dangerous.
Bill is also ABSOLUTELY correct about the isolation diodes in the charger in the second part of his post.
Thank you for the information. The simple solution is to leave the charger wire disconnected until I am plugged into shore power. Then when the shore power is disconnected remove the wire from the battery.
The simpler solution is to
leave the second battery connected to the charger and put a simple switch in the line.
leave the second battery connected to the charger and put a simple switch in the line.
- Status