You are not really drawing your batteries down deeply. You have a large bank in relation to your daily needs,and your plans on charging every 4 days is detrimental to the batteries.
Batteries do not like to sit there for 4 days and slowly be discharged a little further each day. they are not going to respond well to this treatment no matter what voltages you hold them at on day 5, nor for how long you can hold them there.
Now, when you batteries are well over 80% state of charge, and you put the PM 75 amper on it, and the batteries can only take this much current for a very short while, because they are over 80% charged, and over 80% charged they cannot accept much current.
It is the lead acid battery conundrum, batteries sulfate when sitting below 80% SOC and the lower and longer they sit there , the harder to redissolve the sulfate, but they cannot recharge quickly from 80% to 100%.
Where as below 80%, they can, within reason, accept nearly everything that can be thrown at them. My single 31 will easily take 75 amps at 50% SOC. So you see the 50 to 80 strategy is actually more efficient, generator wise, than the 80 to 100. You can do a 50 to 80 quickly, You cannot do a 80 to 100 quickly. They will gas a lot in the 80 to 100 range, and use a lot of water, They will not gas nearly as much or use much water in the 50 to 80 range.
But, a 50 to 100% cycle is required, absolutely necessary, after so many 50 to 80 cycles. Your PM and a generator are not Ideal to reach 100%. The MW can take over when the PM drops to 13.6v, and shoehorn in that last 20%.
Your batteries at this point are capacity compromised to some degree. The shallower the cycle the better mentality, is not always gospel in real usage.
Since you are up north, your Max SG on those Canadian brand batteries might very easily max out in the 1.300 range. I can tell you it is very obvious on my battery, the performance when there is a .025 difference in max SG attained each day.
Try not being frugal, take that bank down to 50% overnight one night, and let the Powermax's 75 amps loose on it, and when 13.6v is triggered, take a SG reading, and start up the MW crank it upto 15v, and when the Trimetric tells you they are sucking less than X amount* of amps at 15v, take another SG reading, and dial the MW upt max voltage at 15.5x and keep taking SG measurements every so often until the SG no longer rises.
*: X is to be determined by those who already cycle 6v GC batteries successfully, not me.
Make sure there are no bubbles sticking to the hydrometer float.
The electrolyte will get hotter when equalizing, and if not compensating for temp, it can appear as if the SG has stopped rising, whereas factoring in the higher temps and the SG is indeed still rising. If you got a plastic hydrometer, give it away to an enemy, and get a glass turkey baster style.
You need to find the absolute Max SG. Don't just assume 1.275 is indicative of a full charge on any particular battery. My previous Crown batteries would get upto 1.305, my USbattery I have seen 1.290 once on a hot day. Some other times I cannot get it up past 1.285. The max SG also changes with electrolyte level, the higher the level the lower the max SG will be, the lower the level, the denser the acid and the higher the SG. Mine will not exceed 1.275 when topped up, the 1.290 reading was at the lowest level I've let the electrolyte get.
I used to have 2 group 27's for 230 Ah in the same general overnight usage as I have now with only a single 31 at 130 A/h. I'm guessing at this point I will be getting longer service life cycling this 31 battery deeper daily than the larger bank shallower daily.
But checking the 2 27's SG was a huge PITA for me and I'd not dialed in the proper ABSv or duration, or Eq'd often enough, but since they did spend so much time in the 80 to 100% range, they used a lot of water, and both sets of 27s were compromised from slight plate exposure.
Also, check you converter/ battery cable terminations for heat when the Powermax is in bulk mode providing the 50+ amps. If they are Autopart store bought 4 awg cables with pressed steel ends and a hole drilled through them, you got to get that steel off of there and get some quality ring terminals properly crimped on. I don't like your description of how the Powermax drops off early when the other charger attached kicks on at significantly higher amperage and voltage. Me suspects high resistance somewhere in this circuit.
Also It is possible the trimetric is not reading all the current if any ground cable runs directly to any battery (-) without going through the shunt. Some chassis grounds might be finding their way to ground through the engine starting battery and not being measured by the shunt.
These readings could be caused by sulfated batteries or just plain undercharged batteries. They hydrometer should not lie if it is accurate and compensated for temperature. I only have experience with my single 130 Ah 31 where I took close readings with a hydrometer and clamp on ammeter. I would not trust any current readings on a charging source itself unless verified by other tools that are known to be accurate.
I don't recall seeing in this thread the length or thickness of the cables from your Powermax to the batteries. If the cables are too thin and too long then the PM will see 14.6 and shut down bulk mode, way before the batteries actually climb that high. When you put your other charging source clamps directly on the batteries then there is less voltage drop to deal with and it pumps all it can into the still thirsty batteries and more than the PM was capable of doing.
Check voltage at PM output and at battery terminals themselves when charging. Do not trust any voltmeter placed anywhere else along the circuit. Lots of underperforming charging systems out there due to too long and too thin of cabling between battery and charging source.
Others with GC batteries should chime in and state the amps required to take a near fully charged pair of GC's, to 15.5x or 16 volts. My 31 takes 6.2 initial amps to reach 16v after holding at 15.3v for an hour taking 1.5 amps or so to be held there. As the Sg rises the amps required to hold 16v taper to around 4 amps for this 130 amp hour 12v battery.
I'd treat your unknown GC batteries like Trojans and use their ABSV recommendations until proven otherwise by various tools, number one being a hydrometer and an accurate voltmeter taking readings at both battery terminals and converter output terminal
Power supplies in this application are basically voltage regulators, the battery itself is the amperage regulator. The power supply does no amperage regulation other than not being able to provide more than its rating, it regulates the voltage and the battery takes what it takes to climb to and match the power supplies regulated maximum voltage.
All charge controllers are basically just voltage regulators whether it be an alternator, a converter, a smart charger or a power supply.
I assume two power supplies can be run in parallel without confusing each other.
I do not think you need 2 MW's with the powermax 75 amper, just disconnect the powermax and switch to the MW once the PM drops to the premature and oh too slow 13.6v. At that point, at that state of charge, the MW should be able to hold 14.8v with no issues and rise to 15.5x no issues either if so desired.
Yes, the 6.2 amps is what my screwy 31 12v battery requires to be brought upto the 16v, after it has gone through the regular charge cycle which for my 31 is ~ 2 hours at 14.9v and 1.5 hours at 15.3v. The Schumacher can blow past ABSV and will require 15+ amps to hold 15.6 volts, and my monitor will indicate 20 amp hours from full, where as when I initiate an EQ cycle after the solar has done 14.9 and 15.3 for 3.5 hours, the monitor has already returned to zero.
Batteries themselves decide how much amperage is required to bring them to and hold them at a certain voltage. With Eq'ing just make sure the battery has gone through the normal ABSV cycle before initiating the EQ. Hold the ABSV longer before initialing the EQ cycle if you want to feel safer. The Hydrometer can help you determine the most effective ABSV if you cannot find manufacturer specs. I found my ABsv had to be higher than USbattery recommendations, or SG dropped further faster cycle after cycle and longer EQ sessions needed to max out SG.
The longer the ABSV is held, the more likely it is that less amps will be required to hold 15.5x or 16 volts, what ever the max voltage of the charging source allows.
The danger with cranking up the voltage too soon is that the battery did not have time to get near full charge before the EQ cycle was forced, and huge amp numbers will be required on an undercharged battery to bring it upto EQ voltages, and this, is abusive, even if effective at maxing out the SG.
I'll likely get the same power supply as you as I cannot trust my Schumacher. I don't mind monitoring it and moving the voltage pot. I am worried the pot will not like lots of adjustment though. I'd almost prefer to feed my solar charge controller with a 15.5v power supply as it allows precise setpoints be reached, but it is limited to 25 amps.
If there is too much amperage, above the 5 or 6% of capacity, then the batteries were not charged enough before the EQ cycle was initated.
I have a schumacher "automatic" charger which will just blow past the mid to high 14's and pump in 15 amps at 15.8 volts, which is too much. The battery needed time in the high 14s to reach near full charge.
My screwy 31 after ~2 hours at 14.9v, then after 1.5 hours at 15.3v, the amps will have tapered to about 1.8 required to hold 15.3v
Changing the solar setpoints to 16v at this point, and 6.2 amps are required to bring the battery to 16v. By the time SG has maxed out, amps have tapered from the 4.2 to 3.8 range.
I've done this enough I can just end the EQ cycle when I see the amps required to hold 16v drop below 4 without dipping the hydrometer. But this will likely change as the battery ages. Here is a good video that shows the relationship between amps and voltage on a fully charged battery.
Lots of his videos are pertinent to the RV world.
So basically, just don't begin an Eq cycle until the battery has sat at the manufacturer recommended absorption voltage for a good while, until the current required to hold absV is a small percentage of the battery capacity. Don't crank it upto 15.5x until it has sat at 14.x for a good while and the amps required to hold 15.5x will not be abusive to the battery. But crank it upto 15.5x well before the battery is in the 95%+ range, and large abusive amp numbers will be required to hold the battery at 15.5x volts
I do wonder how long before Lifepo4 becomes affordable. No peukert, no worrying about partial discharge storage, ability to accept insane charging currents, support huge loads.
No more 6v vs 12v threads..........
Don't get me all riled up about muffin fans......
Back before I knew better, I replaced the failing extremely noisy fan in my Coleman 800 watt MSW inverter, with the same exact fan.
I'd thought if I did not use the same exact fan the unit would blow up.
Well the new fan started getting loud in about two weeks.
Sleeved bearing Chinese POS!
Lots of fan options are out there, some of them downright impressive with the effort and technology and design to not only move air, but move air more effectively for less noise and less current consumed.
Here, I ripped the loud 40MM fan from my Schumacher sc2500a and installed a 60mm Noctua, which is basically inaudible. The magic blue smoke is still safely contained within.
Also, I take issue with the locations some products choose to locate their fans. Any resistance behind the fan blades.... the closer the resistance is to the fan blades, make the fan less effective and also make it louder.
I Put a Noctua 120mm fan pushing air through my compressor fridge condenser, replacing a sleeved bearing higher noise higher CFM fan pulling air through it, and performance increased, and noise decreased, and the fan itself draws less than half the current.
Don't believe me, go put your fingers near the back of a spinning muffin fan. Airflow will decrease by a significant amount and the noise the fan makes will increase. Put your fingers in front of the fan and it will move nearly the same amount of air, and make no more noise.
So instead of mounting the fan in a manner where it can be most effective, they just use a higher RPM fan in the most appearance friendly location, as the expense of fan life and noise.
BTW, with muffin fans, you cannot just reverse the polarity to reverse fan spin direction, and the better fan blade impellers will not be effective in reverse.
I did a quick dip yesterday.
I've been using the battery pretty hard. Monitor reporting 40 to 60 A/H removed each night. 95% solar recharge. Infrequent driving and a smidge of 25 Schumacher amps in the morning on some cloudy days.
My PVL-68 is partially shaded most of the day for the last 10 days, causing an ~ 2 amp drop in max solar current, but I still get to float each day, just a little later.
While I've set my float at 15.3v I've had my Max battery volts set at 15.0v.
So 14.9 absV and 15v float since last report.
SG Reading as of yesterday when taking 1.5 amps to hold 15.0v
1.255, 1.250, 1.260.
That lack of time at 15.3v finishing/top charging daily was apparent in SG readings, and during discharge too, as it drops fast to 12.4, and then 12.2, but it seems very reluctant to drop below 12.0. It is quicker to lose voltage under load, but seems to man up and fight at the 12.2v level despite the loads on it at that point which will touch 11 amps at times.
Anyway the battery is being worked hard, and I'm going to remove that 15.0v max lock today as it is just obvious to me this battery needs time at 15.3v daily, and it is also due for some time at 16.0v and the 'reset' caused by getting all the cells above 1.275 and close to 1.285.
Electrolyte still clear. Water use not excessive, battery is being worked hard and responding well to the (ab)use and near top charging daily.
Good idea but it's too late for me. I ordered a 40 amp mega watt power supply.
I'm nearly at that point too Came very close to clicking 'place order'. My Schumacher sc2500a is unpredictable and can be violent, as it rushes well past 15 volts while pumping 15+ amps into a 130 amp hour battery.
I like the fact that it can do 16v. I don't like that I have no control over when it does this, or that it does not go constant voltage for a while in the mid to high 14's. Even the AGM setting will go hard and fast and dangerous, sometimes.
I wish somebody would make a converter/charger/powersupply in a relatively compact package which had a temp sensor, a voltage pot for ABSV, a timer to hold ABSV, and a voltage Pot for float.
Imagine that, a tunable automatic charger, as opposed to a 'we know what is best for you' algorithm.
Seems the regular options are PD 14.4 max. no thanks.
or the PM Reach 14.6v then instantly goto 13.6v, no thanks
14.8v, but exceed 105f ambient, and it shuts down.
Screw all these converters. Not one of them comes close to what my batteries need/want.
Maybe I should have the option feed my solar controller with a 15v 25 amp power supply. At least my MPPT solar controller allows for voltage adjustments and durations, and I'll never need more than 25 amps if I have grid power.
Trojan recommends 10 to 13%. Even 13% is hardly a number the Trojan will not accept, and besides, a portion of the solar current is going to go straight into any appliances running when the solar can indeed some close to that recommended range.
There are reports of these large 12v Trojans requiring higher voltages for longer, compared to GC batteries, to max out the SG.
I have a single 12v group 31 ( claimed 130 A/h) that will happily gobble up 65 initial amps when depleted. It recommends a 10% rate, which would be 13 amps. My solar can just do this for a few hours on a cool June21st, and with everything electric turned off.
Charging rate maximums, IMO. apply to Gel batteries, and to lower end AGM's which say no more than 30%. When the next discharge cycle begins just before sundown, gosta do everything one can to get them near 100% before then.
HOw many LEDs are you running in series?
I've been using this one for a month continuously and it can hold, at a fan rated at 1.3 amps, 1.2 volts below input voltage, and the output voltage stays steady no matter load or input voltage.
They have less expensive versions without the voltmeter display.
I put 2, one decimal mini voltmeters on my dashboard. I tested them with my DMM, and turned the adjustment pot to dial it in and have the sense wires right on the battery terminals. Very informative.
This made me realize how much more informative a two decimal digital voltmeter would be, and I found one on Amazon for about 7$ with a red display, and knew it had no adjustment, and when testing it, found it was close to 0.20 volts off.
Non adjustable, useless. My recourse, a bad review and a 'product no longer available'.
Anybody want it? just pay for shipping.
I've found Amazon shipped products from China say they will take 3 to 6 weeks to deliver, and show up 7 to 10 days later.
One electrical product I ordered on Ebay said it was to be shipped from china, but shipped from Brooklyn, with missing parts, but they made it right. I'd found the same product on Amazon for 1$ more, and it arrived before the Ebay replacement.
I wound up taking ~60 A/H from the 31 last night, and the lowest voltage recorded by sunrise was 12.0x when the compressor fridge cycles on with the fan load about 3.5 amps total.
The night before, it was hitting 11.8x under the same general depletion and max loads. Even the incomplete eq cycle restored voltage to younger battery expectations.
Just before noon today, and 32A/h from full, taking 9.2 amps at 13.7v, I allowed it to see alternator current. Took 37 amps + 9.5 solar amps to bring voltage upto 14.9, and tapered to 22amps by the time I parked in front of ocean 5 minutes later, where I separated the AGm and 31 after I shut down engine. 9.5 solar amps had 31 at 14.1v.
Alternator not able to hold 31 at 14.9v at idle speed en route. Dang traffic lights.
No alternator current on return trip as it was already in ABSV mode when I rinsed off the salt water at 2pm. Starting engine during ABSV mode triggered 15.3v float mode, even though 31 was not hooked to alternator, drops back to 14.9ABSV with engine off.
After a few errands, and back home, I Released the solar 15v max hold I had on the 31 switched loads to AGM27, and 6.2 amps were required to raise 31 to 16v.
1.270, 1.275, 1.280
30 minutes later, 4.1 amps
1.285, 1.285 , 1.290
So nice having flooded battery at easy eye level. Pop hood, pop cap, dip hydrometer, turn manual switch, change solar voltages......
wait a minute, thats a lot of steps!
Cycling AGM tonight, as it was already 12ah in the hole come sundown.
I've been cycling the 31 pretty hard, 40 to 70 aH removed every night. Twice I allowed the Schumacher help when there was clouds/drizzle all day. It skyrocketed past the high 14's holding 12 to 14 amps until the battery voltage was 16.1v. I have to get a better charging source, this thing is just a bit ridiculous. I'd unplug it and let it restart. it would just go into float and hold 13.2 V as expected. One night I just let is stay at 13.2v while I cycled the AGM, and once again the AGM held 12.4 where the 31 would have dropped to 12.0 in the same usage. The 31 was taking about 5 seconds of .25 amps and then shutting off for about 15 seconds, before .25 amps again were required to hold 13.2v.
The last few nights, I was a little nicer to it, and took no more than 45 A/h from it, and not enthusiastic about voltages held under load.
Dipped today after 15.3v was in effect for 2 hours and taking 1.6 amps.
1.255, 1.260 and 1.270
Turned CC upto 16 volts. 6 initial amps tapered to 4.2 amps, as usual, SG had risen to 1.275 1.275 and 1.285 when the sun got too low to hold 16v about 45 minutes later. No Noticeable water loss
So it was a premature ending eq cycle.
Electrolyte is still clear, no gray particles.
Right now 9 amp hours removed, 7.8amp load, 12.34 volts, which is better than last night.
Battery not like new, but still meeting my needs, and I am going to keep making the SOB work, and work hard, and I'm gonna keep Solar ABSV at 14.9 and float/finish at 15.3v while I cycle it hard every night.
I use this device to limit voltage into a fan whose hub gets too hot at battery charging voltages. The output voltage stays the same no matter the input voltage.
I just found one of my T10 LED bulbs starts flickering at voltages under 11.5. I'm not taking my batteries that low, but this same distribution point feeds my laptop, which can take 90 watts and pulls down the voltage on the circuit, so it would be nice to have an adjustable boost converter too.
Some of the sailboat buys are getting along well with their Lifpo4.
One guy is saying he can detect no capacity loss after 400 cycles.
NOt in the same price league as Mex's link, but I've been watching these Lithium jumper packs come down in price.
I believe the highest capacity 18650 Li-ion cells are now only 3600 Mah. Panasonic NCR 18650b were the standard and are 3400 Mah. All sorts of other cells, especially those with 'fire' in their names, are likely 18650 cells taken out of laptop batteries with a new shiny wrapper wrapper and some fancy marketing.
They like to claim to have protection circuitry too when none exists. I believe I own such a reclaimed laptop cell, and it lasts about 1/4 the time in my Nitecore HC50 as do my Orbitronics 18650's which are based on the Panasonic NCR18650B cell. I have two bare panasonic cells too.
It'll be nice when prices drop.
My old compressor Norcold had a Jamicon 80mm 24v fan blowing upwards through condenser/compressor but it would only turn on if temps exceeded 115F.
So possibly, your absorption fridge is doing the same thing regarding the fans.
Muffin fans are polarity sensitive. They won't just spin backwards if polarity is reversed.
I've saturated both carbon fiber and fiberglass with superglue to bond plastic parts together which broke. The fiberglass is easier to see when it is completely saturated as it goes clear. I take the dremel to it to sand down any sharp edges, and then another drop or 2 or superglue to make it pretty again
In general I use epoxy to saturate re enforcing fabrics, but epoxy bonds poorly or not at all with most plastics, and epoxy needs to be mixed precisely, making small batches more prone to error.