Understand, I am at the low end of the user range, with a single T-1275 150 Amp battery, 3 years old, and used from the local golf course, that was in essence free, I had to pay a core charge, but that was about it.
My usage, daily, might be 35-45 amps, out of the original 150 amps. For all I know, it might be down to only 130-135, having lost 10% in it already hard life of 500 discharge cycles in a golf cart.
My basic usage is to have this thing get me up to about a level of 90% charged. As a result, I just set it at 15.1 V on that big T-1275, and it draws what ever amps it draws. Might start out at 33 and drop down quickly to 27 or 25, or 20 amps, depending on what the battery decides it wants. If I tweak the pot voltage downwards, the amps it takes at start up drop downwards also.
My take is that the higher the voltage that you start with, the higher the "water pressure", which in turn allows more "volume" or amps, to flow back into the battery, at a higher rate.
These have been my observations since buying my Mega Watt 30 amp unit. Don't forget that Mega Watt also offers a 36 Amp version for like $60 instead of $50, plus shipping charges.
Since I don't own a pair of GC2's, and all I really use this Mega Watt for is just a "Bulk Charge" phase charger, and I don't full time in my travel trailer, my usage needs are unique. Having said that, for me, for my usage, this makes a great bulk charger. Sure it will top charge too, if you want to back off the voltage a bit once your amp flow drops down to about a C-20 rate. For example, when I see about 10 amps on the meter, with no other current other than the basic parasitic refrig, CO and propane detector and radio off draw, about 2 amps worth, I know it's time to shut down the Mega Watt in the morning, and let the solar panel do it's thing. I know I am about 90% charged when I see those kinds of numbers when the Mega Watt is set at 15.1 V.
The 15.1V charge rate, to me, is what really drives a quick charge rate to 90% charged. My goal is not to beat the battery up, per say, but get it done quickly and get off the generator in an expedient manner. Battery life, for this T1275, is in the retirement stage. It's seen better days, it's been worked hard already in a golf cart, and since it was free, I can cycle it hard with some impunity. It's used 5 or 6 times a year, for a week or so, so it has an easy life, most of the time.
I will pull out the old Sears manual battery charger today, since I know the battery is top charged, and will give it a solid 16.0 V equalization, and then let it rest in peace in storage on a furlow, until I am ready to go camping again.
I don't see the power supply as being super complicated. I know my battery capacity, I know that the Mega Watt will do, and I know that when I see the amps charging rate on the silly meter drop off to 10 amps, in my case, then the Mega Watt and the Honda have done their work for the day, it's time to let the solar panel take over.
I'm not afraid of that 15.1V rate. Others with lead acid open cell batteries may feel more comfortable with only 14.8V. The Trojan T-1275 behaves in many ways a lot like a Screwy 31. It needs the added voltage, in my observations, for what ever reason.
At the end of daylight, I might see 12.62 V on the meter, with that 1 amp parasitic draw that is constant, maybe with another 1 amp being drawn by a LED light or two, and the water pump for a 3 or 4 minute Navy shower, plus some listening to the radio.
Come morning time, with some heater usage ( not a lot, perhaps an hour or hour and a half before bed time), I am down to 12.28 to 12. 36V come day break. Since this is the coldest part of the day (was 25F to 35F most mornings this past week) V is going to be lower anyways. It will take a lot, voltage wise, to push amps back into a battery that cold. 45 minutes to an hour, and I will see the amps dropped off to about 10 amps, 8 actual. When that happens, time to shut the Mega Watt and generator off, their job is done for the day. Time to let solar panel take over the super inefficient part of top charging and stuffing in that last 10% back into the battery, instead of wasting gas and time trying to do so.
