high rate charging on generator

[pianotuna]

Hi all,

The batteries:

556 amp-hours of surplus acid AGM batteries 12 volt jars 105 lbs each. They are wired as two banks with balanced wiring.

The depth of discharge:

12.1 volts under 425 watts of load plus normal RV overhead applied for 4 hours. During the day the fridge (325 watts) was run for 5 hours and the RV was driven at highway speeds for 3 hours. On the last hour of driving charging was initially 50 amps but that soon tapered to 25 amps. The solar contribution was about 5 amps.

The generator:

Yamaha Sieb 2800 Va (23 amps of output @120 volts AC)

The inverter/charger:

Magnum 3000 hybrid.

What happened:

I deliberately took the battery bank down farther than I normally would. I turned on the generator after setting the Magnum to draw no more than 23 amps.

Within one minute the Magnum remote reported "fet over load". Remote was showing 127 amps of charging at 12.9 volts DC just before the over load shut down.

I reset the Magnum by removing all power sources. I "dialed down" the possible input to 15 amps from 23. This still caused the Magnum to display 125 amps of charging. I finally dialed it down to just 13 amps to prevent over load on the fets. At that level charging was 90 amps @ 12.5 volts.

I've been charging for 45 minutes at 90 (+) amps and the voltage had risen to 13.8.

I 'opened up' the input to 23 amps and after 15 minutes it is now charging at 14.3 @ 98 amps. The remote is saying absorb charging.

15 minutes later and the remote says 14.3 at 80 amps.

1.5 hours and charging is 14.4 @ 27 amps.

During this time frame I did also run the microwave and three oil filled heaters (400 watts each).

The generator was running with the eco switch on and at the 45 minute point started throttling back as the load shifted.

Next time my voltage is so low I'll dial the Magnum down to 13 amps to start out.

[pianotuna]

Yes you can adjust them *if* you have the remote. Load support, which is what I wanted most only works with the remote.

[brulaz]

pianotuna wrote:
Hi Mr Wizard,

It is set absorb of 14.5 and float of 13.6. It does have temperature probe so I'm now seeing 13.8 and 14.7.

The agm selections are not close to what my batteries appear to require.

You can customize/adjust those voltages in the Magnum?
Or are you just using the Flooded Lead Acid setting?

When I was looking at Magnums I didn't see any way to adjust the specific voltage settings, just select AGM, Flooded or ...

Otherwise they looked like really nice units.

[pianotuna]

Hi Mr Wizard,

It is set absorb of 14.5 and float of 13.6. It does have temperature probe so I'm now seeing 13.8 and 14.7.

The agm selections are not close to what my batteries appear to require.

[MrWizard]

PT
does your custom setting include a higher charging voltage
lower internal resistance plus higher charging voltage equal
higher amps

if that is the case, either be prepared to baby sit and manually change settings
or set it to std AGm settings, and have peace of mind about the safety of the magnum and the batteries

i think a lower voltage and keeping the magnum happy is the best option

[full_mosey]

Hi pianotuna;

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.

HTH;
John

[pianotuna]

Hi Mr Wizard,

No, I used a custom setting because of my "surplus acid" AGM's. I do have the temperature sensor in place, and I'm observing increasing charging voltages.

The Yamaha generator is essentially a 23 amp shore power device with 500 watts of overload capacity for ten seconds.

Even on a 15 amp shore power I would have had the fet overload happen. I had to dial back the input "throttle" to 13 amps to keep the charge rate down.

I believe I'll take your advice and email Magnum to see if they have an answer.

[MrWizard]

yes..i know about load support
but it does not charge while doing this

anyway you answered the initial question
everything, charging and heaters was on the generator

sounds like the magnum is out of adjustment
it should NOT exceed its output rating anytime
what if you were on 30amp or 50amp shore power

you did change the setting to AGM batteries right
something needs to be adjusted someplace, maybe by factory service personel

[pianotuna]

Hi Mr Wizard,

Actually the Magnum 3000 allows load support--so if the pass through is set to 15 amps and I am running 12 amps of heaters, and then start the microwave it will draw from the inverter for the extra power needed rather than blow the shore power breaker. When it moves to load support it does stop charging and goes to inverting mode. I love the feature. I wish it did voltage support as well--but it really does not. That means I'm still in the market for a good autoformer.

But I was not using the inverter. It was turned off. So the Magnum was only doing one thing--trying to recharge deliberately thirsty batteries.

[MrWizard]

PT
i was thinking Maybe you were running a separate inverter, using the yammy like you did the 15amp shore power
less input than output load use

combo units even the magnums, only do one thing at a time its either charging or inverting, it can't do both at the same time

[GordonThree]

fet overload would seem to be a software glitch - maybe contact Magnum for a firmware update?

charger should rollback its charging rate well before it hits the "overload" point.

[pianotuna]

Hi BFL13,

To keep the unit from going into fet overload. I agree that normally 'more is better'.

BFL13 wrote:
Whyinheck would you want to limit the charging amps???? More is better!

[pianotuna]

Hi John,

Thanks for the ceramic heater and recharge information.

[pianotuna]

Hi Landy,

Output voltage so far as I am aware is set as a 'favorite' which allows me to change it. But the voltage was not at 14.5--I think it was only 12.9 during the event.

I doubt that the Magnum over heated in under one minute. I watched as the amperage flew up to 127 then announced 'fet overload' and shut down the charger.

I've only seen bulk charging once before--and that was with my old tired flooded batteries. They were charging at 125 amps.

I am using a custom setting for output voltage rather than the two agm choices Magnum is set up for. The reason I did that is because the float voltage was not 13.8.

landyacht318 wrote:
If you can change the output voltage, you can change the charge output amps.

But you might have to keep twiddling voltage upwards to keep it close to the 125 max output.

I wonder if this is something that could be attenuated with more ventilation.

[full_mosey]

I have the smaller Magnum 1012, a 1000W/50A. I use temp comp and let the Magnum set charging Volts.

I 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 800W with a 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.

HTH;
John

[BFL13]

landyacht318 wrote:
If you can change the output voltage, you can change the charge output amps.

But you might have to keep twiddling voltage upwards to keep it close to the 125 max output.

I wonder if this is something that could be attenuated with more ventilation.

The temp of my meanwell at 40 amps is quite high after 45 minutes at full output, but once amps start tapering, at about 35 amps the heat produced drops drastically.

Add more computer fans, add more heatsinks, if possible.

BFL13, 156 amps........ That's freaking awesome.

156 on four is the same as 78 on two which is no big deal (as seen on my ugly graph somewhere here for 70,55, and 35 on two) PT has more AH in his bank than I do so he can go well above 156 and be ok.

I totally lost track of what PT's problem is from the OP to here. It's not the gen, now it's not the inverter, which leaves--him!!! 🙂