Measuring DC current out of a battery charger with a 500A 100mV shunt

[Jedon]

Okay I got my hydro going and the numbers for the raw hydro output look good, 5.26A at 108V DC but I don't think I'm getting all that power into my batteries.
I got an IOTA 13A 55.4V DC battery charger and feed the DC right into that even though it's an AC input charger, I was told it would work and it seems to do something.
I want to measure how much current I'm getting out of the charger. My multimeter can read 20A DC so I tried that but it went blank so it must surge about that?
It seems like the voltage and current when the charger is connected to the battery bank, becomes that of the battery bank?
I think I can just put the shunt on the + side of the charger and measure the voltage drop across that to calculate the outgoing amps, right?
I know I shouldn't be using AC rated breakers but it's what I have for right now so my setup looks like this:
hydro->20A breaker->120V AC socket->battery charger->20A breaker->Batteries ( 8 x 6V golf cart )->inverters
Since I'm getting 12KWh+ per day raw out of the hydro that seems like it should be enough power so I don't have to ever run the generator but I still do so I'm trying to figure out where the issue is, maybe I'm just a power hog?! I have an AC power meter to install that will help with that side.
Thanks!

[Hank]

I'm not sure about putting in DC power into an AC charger and expecting it to work correctly if at all.
In terms of measuring DC amps you are correct in using a shunt. What you can do is use a length of #10AWG wire on the + side charging your battery. Measure the voltage drop across a 1 ft. length of this wire and your current will be pretty much what you read in millivolts, ie. if you measure a 20 millivolt drop the current will be 20 amps.

I'm not sure what your generator system is or how far it is from your battery banks but you may want to consider a charge controller to charge your battery bank and divert any excess power to a water heater or some other load.

Hank

[mike90045]

I've got the 48V Iota too, and while they call it a 48V charger, it is barely capable of getting 54V, which is not quite a good bulk charge for a large 48 battery bank.

The Iotas work fine on DC, and with enough hours, they will get your bank up to about 4/5 of full, they won't get into the absorb (59V) stage at all, their voltage is too low.

I used a Kill-a-watt to measure my Iota - to see what it was putting out.  It's only got a .65 power factor, but on DC that doesn't count.

5.26A at 108V DC = 568.08w / 55V = 10.3A x 85% = 8.77A DC     So 8.77 A is the most that it can put out , with whats going in.

[Jedon]

Hank, thanks for that trick with the 10g, I didn't know you could do that. I have a real 500A 100mV shunt so I should probably just use that.
My generator is about 4ft from my battery bank, Lister SR2 12HP 5600W. I also have a Metro CS 6/1 with an ST-5, the power is very lumpy and flickers my lights.
When I turn the Lister on, it brings the battery voltage up to 58V and the IOTA turns off :-(

Mike, thanks! It's great to have someone doing the same kind of thing for sanity check. So my Kill-A-Volt won't blow up if I feed it DC? What about open circuit 208V?
I have a Morningstar Tristar TS-60 PWM charge controller, is that useful?
I have my PV at 65V hooked directly to my batteries right now, 800W.

[mike90045]

Kill-a-Watt is ONLY 120VAC    I run my Iota from a honeywell i2000 genset.

[Jedon]

Thought so! You said the IOTA can run on DC so I thought you might be doing so.