Blew up two Daly's, so just ordered a Batrium

[upnorthandpersonal]

I wonder how much this would be a factor with the "true" sign wave (20khz, iirc) coming from the Quattro. Regardless, you point is well taken.

Even with a pure since wave inverter, the input coming in the DC side is not constant, so you will see a pulsed current on battery side. I really should capture a waveform with my scope, since this is not the first time this comes up...

 

[digimer]

Even with a pure since wave inverter, the input coming in the DC side is not constant, so you will see a pulsed current on battery side. I really should capture a waveform with my scope, since this is not the first time this comes up...

Graphs!! :D

 

[vk2emp]

The proper way to test batteries to get a true idea of capacity is wirh a dc electronic load - I have a small one which does around 500W, but those batteries Madi has would take days at 500W, possibly even weeks with the "Big Battery" stack. Basically you want to do a constant current, and set it at what you roughly expect the boat to draw.

Those batteries, if they were just house, would be overkill, but as Madi wants to also have an electric drive, I can see why she wants a truckload of batteries on board.

 

[digimer]

The proper way to test batteries to get a true idea of capacity is wirh a dc electronic load - I have a small one which does around 500W, but those batteries Madi has would take days at 500W, possibly even weeks with the "Big Battery" stack. Basically you want to do a constant current, and set it at what you roughly expect the boat to draw.

10.9kw, max draw with the pod motor I am currently looking at. Plus what ever the Quattro is pulling for the inverter. Let's say 15kw as the very very highest load. Realistically, I'll usually be at 1/2 throttle with minimal AC load while moving, so say 6kw realistically.


Tricky to find a constant 6kw draw.

 

[vk2emp]

Then you divide it - get a 1kW dc electronic load and simply divide the runtime down by 6 to get the average runtime of 6kW. Then subtract 20% to give yourself a saftey margin.

I am charging a 150Ah 12V LFP using a 32V power supply simulating a solar panel into a smart solar 150/35. At 20 amps change current (the psu trips at 25A) its so far taken 3 hours and am at 52%

 

[digimer]

Then you divide it - get a 1kW dc electronic load and simply divide the runtime down by 6 to get the average runtime of 6kW. Then subtract 20% to give yourself a saftey margin.

I could do that with any consistent load, really. Track the wattage drawn into the inverter, it's fundamentally a DC load. I'd like to hit 6kw+, 15kw ideally, to confirm temps stay good under max load. You were talking capacity though, so I'm admittedly thinking beyond the original topic.

 

[vk2emp]

6kW is a scary amount of power - I'll stay around the 2kW level here - but I'm only powering servers and other stuff, not a sailboat with an electric drive

Because I have a house based system and live in Australia, I usually have sun (not today - raining) and shore power, so I can always give my batteries a boost if the sun doesn't want to play. Unless you have a genny, you have to be careful about your power budget on the boat

"Hey Siri, turn on the charger"

Funny how we went from discussing me exploding Daly's to talking about battery capacity and sailboats - made a fun change to the thread.

 

[stienman]

Even with a pure since wave inverter, the input coming in the DC side is not constant, so you will see a pulsed current on battery side. I really should capture a waveform with my scope, since this is not the first time this comes up...

That would be great! That's not good for the batteries, though, from an efficiency standpoint. I'd expect capacitors to provide significant smoothing. Now I definitely want to see some measurements...

 

[upnorthandpersonal]

That would be great! That's not good for the batteries, though, from an efficiency standpoint. I'd expect capacitors to provide significant smoothing. Now I definitely want to see some measurements...

The capacitors definitely smooth it out, especially at lower power draws. But as soon as you start putting a decent load on it, you can clearly notice it. You can even see that with the JK which doesn't do averaging (and hence why the values jump around).
I'll hook up a scope once I find the time and capture a few different waves of both my 6kW low frequency MUST and my 3kVA Victron.

 

[vk2emp]

I have an old analog scope, otherwise I'd do the same - its just not great trying to capture something with a scope that so old it has a CRT

Should invest in a Rigol or similar (one of the hackable ones - I like tinkering as we all do )

 

[MurphyGuy]

Another Chinese BMS failed?

I'm shocked...