Got a new Toy! PowerMax Boondocker adjustable 60A

Nope :) AH out is what you see, but AH in has the heat loss, so you must put more in that you get out.

How much to allow for heat is a moving target. From 50-70 SOC not much heat, then 70-90 there's more as "gassing voltage" is reached, then there is a lot from 90-100.

Trimetric picks a compromise amount which you can adjust if it doesn't match your own results.

BFL13 wrote:
Confusion between Peukert Effect and charging efficiency? The Trimetric instruction manual has some good notes on all that. Worth a read.

Also the Magnum manual has something about the specs being at 25F it goes off the specs other than that, and he was having all sorts of over-temperature problems causing it to do its charging pull-back trick.

I don't trust all this kill-a-watt method instead of just reading the amps without really knowing what the conversion factor is. Needs a calibration cross-check. But to do the cross-check you need an ammeter, so just use that in the first place :)

Yes, I think I have started to jumble it all up in my mind. So basically Peukert Effect, not significant enough to worry about. Charging efficiency, really significant losses there, however if you use a DC ammeter between the charger and battery the losses are occurring before you get to the ammeter. Then, Ah out should be pretty close to Ah back in. Think I've got it now!

Confusion between Peukert Effect and charging efficiency? The Trimetric instruction manual has some good notes on all that. Worth a read.

Also the Magnum manual has something about the specs being at 25F it goes off the specs other than that, and he was having all sorts of over-temperature problems causing it to do its charging pull-back trick.

I don't trust all this kill-a-watt method instead of just reading the amps without really knowing what the conversion factor is. Needs a calibration cross-check. But to do the cross-check you need an ammeter, so just use that in the first place :)

BFL13 wrote:
The lower capacity at higher draw is for when you draw right down to 10.5v. When you only run a high draw for a short time, the battery bounces back, so you get some capacity back for lower draws. Also the low draw times compensate for the high draw times. Works out close enough. Trimetric manual has some notes on why they don't bother with Peukert.

I ran some tests on this a few years ago and it came out like the Trimetric guy says. One of the other monitors does use Peukert but that is over-refined for the job IMO (and Trimetric's)

Ok, that makes sense. However, as full_mosey posted (and I plan to try today with my setup) it took him 1.87kWh of charging to replace 1.0kWh drawn from the bank, and that's with a PFC charger running at .98 or higher. So that .87kWh went somewhere. I'm guessing heat generated by the inverter/converter going each direction. So all the losses happen as you are going from DC to AC and then AC to DC. If you put a monitor in line between the inverter/converter and the battery, the Ah out should be really close to the Ah back in? In other words, no significant losses occurring in the battery itself?

The lower capacity at higher draw is for when you draw right down to 10.5v. When you only run a high draw for a short time, the battery bounces back, so you get some capacity back for lower draws. Also the low draw times compensate for the high draw times. Works out close enough. Trimetric manual has some notes on why they don't bother with Peukert.

I ran some tests on this a few years ago and it came out like the Trimetric guy says. One of the other monitors does use Peukert but that is over-refined for the job IMO (and Trimetric's)

Very interesting, and gives me an idea for another test I can run. I'll do the same thing, run a ceramic heater through my 1200W inverter for a specific time so I know exactly how many kWh have been removed. Then charge with the Boondocker plugged into the Kill a Watt and see how many kWh it takes to fully recharge.

Also, this brings up another question I've had. So deep cycle batteries are rated in Ah at the 20 hour rate. Draw it out quicker and the capacity is actually less, slower and it's more.

Now AFAIK people use monitors like the Triametric to measure Ah out and Ah put back in. Seems to me that if you always discharged your battery at exactly the 20 hour rate, It would work fine. But since this is not the case, I don't see how this works.

The best analogy I can come up with is this. Say you had a gas tank with no fuel quantity gauge. If you carefully measured the fuel as it's removed, you'd always know how much you had remaining. Take 10 gallons out, then measure 10 gallons back in and you'd know you are right back where you started.

But... If the size of the tank was constantly changing based on the rate at which you were drawing fuel out, you'd never know how much you had remaining using this method. :h. That's why I have a hard time understanding how something like the Trimetric provides useful info.

That Magnum is nice unit with a well-written manual!

On the watts vs amps thing, what about that 84% "charger efficiency" in the spec? Do you apply that?

I see it says it has "active" PF correction, which came up in another thread, where somebody said a converter would have to have that type of PF correction.

I don't know how this works, but since it has PSW, why does it need a True RMS meter to read the voltage? I thought that was to do with MSW.

MrWizard wrote:
output !!
50amps 15v = 750w
50amps 14.4v = 720w

850 is an over estimation


INPUT ?

The user manual specs on page 39 claim that 7AAC input gives 50A of DC charging, right?

7A*120V=840W input, right?

The 50A DC output could be at various output Volts as governed by the bank's acceptance rate and according to the bank's temperature, right?

I do use the Magnum temp-comp cable.

HTH;
John

output !!
50amps 15v = 750w
50amps 14.4v = 720w

850 is an over estimation


INPUT ?

Hi BFL13;

PF, yes, .98 or higher per KAW. Watts=VA!

I recently ran a bench test on a pair of Eaton Powerware 135AH batteries that were pulls from cell tower(s). It took 1.87KWH of charging to replace 1.00KWH drawn from the bank.

First I drew with an 800W ceramic heater until the KAW read 1.00KWH at 1:15 when I stopped the heater. The Magnum's fan was running furiously. It took the Magnum about 15min to cool down. Battery Volts rebounded from 11.99 to 12.33.

Next I used the house 120V source to recharge. At about 50min, the Magnum automatically lowered charging Watts from 950 to 600W due to the internal temperature as per the manual. The Magnum would cycle in/out of the hot condition. I shut down the test when the KAW showed 1.00KWH used at 1:13. The Magnum was in Bulk the whole time. The battery ended at 13.31V.

The next day I resumed the charging. The Magnum stayed in Bulk for another 36min and then ran 1 hour in Abs before switching to Float at 14.36. I shut the test off as the Magnum was only drawing 126W. The PF never went below .98.

My Magnum may have been exceeding its 50A rating as well. The manual says "7AAC Input current at 50A rated output", which would indicate 840W. I was seeing 950W going into the Magnum until the thermal reduction to 600W. If you extrapolate 840w to 950w then the charging might have been 56.5A

This was a bench test where there was no use of the transfer switch and no pass through of any 120V. The inverter was unplugged from any 120V to force the inverter to run the 800W heater from the bank. Next, the heater was shut off and then the charger was plugged into 120V to recharge the bank.

MMS 1012 User Manual. Look at page 39.

HTH;
John