When I joined this forum I had a very poor understanding of the relationship between volts and amps. I thought a charging source could manipulate each of those individually and had complicated algorithms that could somehow sense the battery capacity and adjust accordingly. This was extremely foolish and ignorant.
After trying to fins some charging source which would be reliable, and could deal with different types of future batteries, and with the help of Mex, I Now use a 40 amp adjustable voltage Meanwell powersupply and use a 90 Amphour AGM battery for both engine starting and house loads. though I have enough room for 345Ah of total capacity.
The adjustable voltage power supply has been modified by me with a 10 turn potentiometer and more heatsinking and ventilation, and I can set it to any voltage between 13.12 and 19.23v and can, if it has to, deliver 40 amps continuously at those chosen voltages. I have a wattmeter/ammeter on the output, as well as a shunted ammeter/Ah counter reading amps into or out of battery. SO I can always see how much amps the power supply is supplying, at what voltage, and how much of that is going into my battery as compared to how much of that is powering DC loads. This removes ALL mystery as to what is going on, and there is no second guessing what the automatic charger is trying to do and and what it is actually doing.
The other night I was unable to sleep, and had not realized I left on a bunch of bigger loads, and at 3:30 AM I clicked my battery monitor and saw I was at 11.7v, 63Ah from full, under a 4.7 amp load.
I go outside and plug in, then plug in my Meanwell power supply, and knowing I will likely fall asleep soon, I set it to 13.6v rather than 14.7v.
When I hooked up the Anderson powerpoles to complete the DC circuit to depleted battery instantly 40 amps was flowing, as there is a big difference between 11.7, and 13.6v. Battery voltage rose instantly to 12.6v but only slowly rose from there, and I went to bed. I am not sure how long it held 40 amps when seeking to hold 13.6v, but I can say for sure it held them for a much shorter timespan compared to if I had set it to 14.7v.
How much amperage is required to get this well depleted battery at ~700 deep cycles and approaching 4 years of Age, to 14.7v instantly? Likely 90+ amps.
I know that now as is, when depleted to about 40% state of charge it will accept 65 amps for ~25 minutes before voltage at battery terminals reaches 14.7v at which point the amps begin tapering.
There is an initial voltage Yoyo when I hook up 65 available amps to a battery this depleted. usually the voltage on this AGM battery will climb to 14.4 fairly quickly at 65 amps, then plateau, then drop to as low as 13.6v, all while sucking up 65 amps. Then some 20 minutes later voltage at battery terminals has risen to 14.7v and at that point the amperage begins to taper.
My point is that when one determines the desired voltage, the charging source should be at maximum output in its quest to get the battery to that voltage.
Anything Automatic is likely trying to figure out a way to not overcharge the batteries, instead of charge the batteries as fast as possible.
The fastest way to recharge is to reach absorption voltage instantly, and depending on the battery(s) and their capacity this can be a huge number, and such high amperage might not be very good for them.
When boondocking off the grid, and time to recharge is a big factor, high amps likley means the batteries reach a higher state of charge when one shuts down the generator, and they wil lnot be discharged as much as otherwise that night, and that is likely overall better for the batteries than coddling them with lighter currents.
Looks like the WFco only did 60 amps when you had a huge load on the DC system, and it never bothered getting the batteries upto absorption voltage. This is fine when plugged into the grid but not fine for boondocking.
Follow BFL13's advice, when boondocking and generator recharging, The powermax adjustable voltage chargers will pump out maximum output until they reach the voltage you have chosen, and then they will hold that voltage as long as you run the generator, and thus basically charge the batteries as fast as safely possible.
When at home and plugged in the Wfco is fine and dandy but if using it to generator recharge you are wasting time and gas and shortening the lifespans of the batteries, especially if the next discharge begins when they are no where near fully charged and you do this every day for 2 weeks.
When one can spin a voltage dial and watch how many amps flow at that voltage, the mystery of how batteries recharge mostly disappears.
I still have an automatic 25 amp charger, but I cannot trust it, and always have to monitor it and second guess it. With the adjustable voltage power supply, the only guessing is how long it will take 40 amps of constant current to achieve absorption voltage, and how long at absorption voltage will be required before amps taper to 0.5% of AGM battery capacity.
I beat the Snot out of this AGM battery by discharging it well below 50% regularly, but then I recharge it to full promptly and often. At 700 + deep cycles the time it takes in absorption to reach full charge is much longer than when it was new, and it can accept 65 amps for less time before reaching absorption voltage, and battery voltage falls further when cranking my engine, but overnight discharges, the voltage held under X amount of amps with X amount of AH removed from battery, well the voltage held is still raising my eyebrows as I have never had any set of batteries last this long and do this well even at half the depth of average discharge.
And it is all due to recharging fully, promptly.
So I Snort in contempt at automatic charging sources, other than my solar controller, whose absorption voltage duration and end amps can be programmed. But hte solar could not keep this battery happy, as there is not enough amps available from my 200 watt array.
