Re: Understanding breakers

Brent Cameron

Just as Nick says….  The 75A is coming from the DC output side of the charger while the 25A breaker on the 220V AC side of the charger is what is powering it.  75A at 24 V (DC) is 1800 Watts so as Nick says, your 220 V (AC) should be supplying something more than that but certainly not the 5,500 Watts that COULD be supplied by your circuit with a 25A breaker at 220V.   The charger will be using rectifiers, diodes, fans, etc which all consume power to convert the 220VAC to 24VDC but nothing like the full 25A on your breaker.  The ammeter will show you WHERE the power is being consumed so (or if your breaker is simply tripping at only say 10A instead of at the 25A it should be at.   

If you put it around ONE of the AC leads going to or from that breaker in behind your 220VAC panel, it will show you the amps being consumed on that circuit.  It shouldn’t be anything like 25A (Nick’s right that it should be close to 10A worst case). If its 10A or so, then you have a faulty breaker.  If it is at or above 25A, there could be something wrong with your charger, or perhaps something else that got connected to that circuit or even a short circuit on the wiring on the other side of the breaker (a leak to ground by a corroded connection, etc.).  You could test out whether it is the charger or not by unplugging it and plugging in some other 220V device (say a toaster or a coffee pot) with a known consumption (such as 1500W). Divide that known consumption by 220V and you will see how many amps it SHOULD be drawing (7A in the case of 1500W) and if it is that then you know it is likely the charger.  If it’s something more than that, you’ll have do do some tracing of the wires to the charger and ground to see where the problem lies.  The nice thing about those clamp on ammeters is that they don’t require you to disconnect any wires or subject yourself to any danger as long as you stay away from touching bare wires or terminal connections.  


On Dec 11, 2021, 12:08 PM -0500, Nick Newington via <ngtnewington@...>, wrote:

It is really simple. The 25A breaker is on the AC panel. The battery charger is powered with 220v AC. It converts the AC to DC and charges the batteries with DC.  Typically 70A  DC output from the charger will demand about say 10A AC at 220v from the generator or shore power….there will be some inefficiency in the form of heat and fans etc. If it were 100% efficient 70A at 25v is 1750 Watts, to produce 1750w the charger will need 1750 divided by 220v which is 7.95A…but it is not 100% efficient so. Allow a bit of heat and waste call it 10A. To charge the batteries at 70A the charger will need about 10A 220v AC ...

 The breaker is set at 25A in case there is some kind of short or other problem it will trip. If it trips at 10A then it is faulty as it should only trip at 25A. 

You must not mix up the AC and DC in your mind. They are completely separate.

Kind regards


S/Y Amelia 
Amel 54-019


On 11 Dec 2021, at 16:12, Patrick McAneny via <sailw32@...> wrote:

Brent, I am a little confused,my normal state of mind. I know that it is a 220v 25 A breaker, yet if I understand you ,75a 24v is passing thru it ? I have a 100 A charger ,but the victory typically shows 70A going to the battery.The charger has two heavy gauge wires coming out of it that I now assume is the supply from the genset.The wire from the breaker seems undersized to carry 75 amps even at 24v ,that is why I thought maybe it closed a relay. I will try to purchase that amp meter ,Thanks for your detailed post.

Brent Cameron

Future Amel Owner & Amel Owner Registry Moderator

Oro-Medonte, Ontario, Canada

Join to automatically receive all group messages.