Battery Charging Questions

[flyboy013]

So I have a few questions about battery charging. I’m currently boondocking. This morning my house batteries were at 11.9V, so I decided to turn the generator on to recharge the batteries.

I’m currently in the bulk phase and Silverleaf is showing 120 amps being output from the charger to the batteries. See last picture below.

At the same time, Silverleaf is showing that I’m pulling in 19 amps of generator power on Line 1. Given that my other systems aren’t using any significant power (HVAC is off, Oasis AC off, etc) I would have expected Line 1 to be using only slightly above 13.5 AC amps (120 amps x 13.5V DC / 120V AC).

So my first question is: what am I missing? The only other items consuming AC power is the refrigerator, basement freezer, and perhaps some parasitic draw from dishwasher, microwave, washer/dryer, etc. The 4.5 AC amp draw isn’t a problem, I’m just trying to understand what Silverleaf is telling me.

The charger is configured via Silverleaf such that the charger is on a 30A breaker. Given this, why would the charger only be outputting 120 DC amps? Shouldn't it be as high as 266 amps (30 AC amps * 120V / 13.5V)? Even given the fact that the charger is going to consume some power itself, it should be significantly higher than it is.

Things are working as they always have been. I’m just trying to understand why they are not operating as I think they should be. Most likely my thinking is flawed.

Thanks

 

[Kevin D Pem]

Because you are working with a smart charger many things come into play. I see that the unit monitors battery temp. I would say that temp is the big player in your charger output. Other things in play are how many batteries in your bank, and the size of them you know total amp hours.

 

[NWIP]

I believe charge profile is dictated by battery type selected (AGM1 or 2) and max charge rate

 

[flyboy013]

I believe charge profile is dictated by battery type selected (AGM1 or 2) and max charge rate

So you're saying that while the Silverleaf may be configured such that it will allow up 30 AC amps to be drawn by the charger, the Xantrex charger itself may be configured to only allow 120 DC amps to flow to the batteries. I guess I'll need to pull out the Xantrex manual to see if I can find why its configured that way and if it can/should be changed.

Does anyone else with the Xantrex charger see more than 120 DC amps displayed on the Silverleaf panel when in the bulk charging mode? I'm wondering if my unit is configured just like others.

 

[flyboy013]

So I’ve been reading the Xantrex User’s Manual and reviewing the configuration of my SW3012 inverter.

In a nutshell, what I’ve found is that the SW3012 inverter has a charging output limit of 150 DC amps. Additionally there is a “Max Charge Rate” setting. This setting which has a default value of 100%, is set by Newmar at 80%. 80% of 150 DC amps is 120 DC amps which is what I’m seeing displayed on the Silverleaf panel.

I’m now wondering why the “Max Charge Rate” is set to only 80%. I’ve sent a note to Xantrex. Hopefully they can answer the question. If not, I’ll ask Newmar.

Given that the the “Max Charge Rate” is set to 80%, it requires the generator to run long in order to recharge the batteries while boondocking.

 

[Kevin D Pem]

Most every thing is designed to run at 80% they have a peak output of 100% but will not last at full out. This is true of engines generators and most electronic I am aware of.

 

[CaptainGizmo]

You’d benefit from @redbaron’s incredible battery guide and worksheet! Helpful in so many ways.

 

[sheridany]

RedBaron's Simple Guide to Battery Life in your RV

This guide explains the 12-volt battery system found in all RV’s and how to properly maintain them. There is specific information relating to Magnum Inverter/Chargers and Newmar motorhomes that use these chargers. Even if your system does not...

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