EU2000i to charge batteries?

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Svenn

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Do I need to buy an inverter AND a converter AND a battery capacity monitor to complete a EU2000i charging system?  I simply can't find any clear instructions online on how to set this up.  

I roughly want to be at a place where I could power a 4.8 amp (~600 watt?) air conditioner off the batteries for about 3 hours before depletion.  I want AGM batteries so I understand I need double whatever the Ah required to do that is because you're only supposed to discharge to 50%.

Does this mean I need an inverter that's rated 600 watts+?  I want the batteries to charge as quickly as possible, does that I mean I need to get a fancy converter to go between the EU2000i and the batteries?  What about a battery monitor?  

Any suggestions of products would be great, including the batteries.
 
I just went through the exercise of charger/generator compatibility.

An Iota 55 amp charger pulls 660 watts, a Honda EU1000i generator is capable of putting out 900 watts continuous power.

A new generator will output full power.

BUT, big but, you will be running the generator continuously while charging the battery bank at about 66% capacity which is going to be hard on the generator. To get long life out of the generator a 2000 or a pair of 1000 would be better.

After many hair pulling moments I found out that my 10 year old, not properly cared for, generator was only outputting something less than 600 watts and wouldn't power the battery charger. Since I can't pick up and handle a 2000 size, unless I can find someone to do a complete engine rebuild on my generator I'm in for buying a new Honda 1000 this coming fall and the parallel cables so I can run both at the same time.
 
Almost There said:
 Since I can't pick up and handle a 2000 size, unless I can find someone to do a complete engine rebuild on my generator I'm in for buying a new Honda 1000 this coming fall and the parallel cables so I can run both at the same time.

I don't really know for sure, but I strongly suspect that trying to parallel a good generator with a malfunctioning one is not a good idea.  Possible outcomes range from not working well to actually damaging the new generator.  I would talk to Honda before trying this.
 
Optimistic Paranoid said:
I don't really know for sure, but I strongly suspect that trying to parallel a good generator with a malfunctioning one is not a good idea.  Possible outcomes range from not working well to actually damaging the new generator.  I would talk to Honda before trying this.

Yeah, that was only the suggestion of the technician at a small engine (Honda authorized) place I took my Honda in to. I want to get it home to talk to a couple of people I trust more than a stranger. I also have some faint hope that one of my two mechanics will see fit to strip it down and rebuild it...fingers crossed!

I have six months, I hope, of plugging in to shore power to keep the batteries charged.
 
I've charged batteries with my EU2000I. Works pretty good for it. Works better as a fast charger tho when you need it.
 
Odyssey or Northstar Group 31 AGM batteries, 3 or 4 of them In balanced parallel with 00 gauge ( or fatter) interconnects .  These thin plate pure lead batteries will hold higher voltages under higher loads than other AGMs.  They can handle, and actually require huge recharging currents when depleted to 50% or below.


2000 watt inverter of your choice.

Power this charger with the Honda 2000:

http://powermaxconverters.com/product/pmbc-12-volt/

They go as high as 120 amps.  At a minimum, get 30amps per 100Ah of battery capacity, Odyssey....40amps.

They have an adjustable voltage option. 
Use a short length of no thinner than 4 awg to powermax

 Northstar wants 14.46@77f

Odyssey wants 14.7v@77f. Odyssey dictates that when deeply cycled it requires a 40% charge rate, 40 amps per 100AH of capacity.

With batteries at 50%,

Set charger when unloaded ( not hooked to batteries) to ~0.15 V more than above voltages, adjusted for temperature. Higher battery temperature lower voltage, lower temp higher voltage.

mark/note position of voltage potentiometer.

Warm up honda 2000, plug in powermax, hook to batteries on opposite end of the string(+) on battery 4, (-) on battery 1.

Flip switch on.

Once the battery terminal voltage hits the desired absorption voltage which will take about 1.5 hours on 300AH with a 120 amp charger, you might want to back off the potentiometer a smidge. Hold desires absorption voltage  for ~3.5 more hours minimum, before these batteries can be considered fully charged.  Really  once amps taper 0.5 amps per 100AH of total AGM capacity at absorption voltage, so an accurate ammeter is required to truly know when these batteries are full.

http://www.amazon.com/DROK-Digital-...id=1462507045&sr=1-1&keywords=200+amp+ammeter

But these are not very accurate at low currents.

A clamp on DC Ammeter can also work for measuring when amps taper to 0.5% of total capacity at ABSV.
http://www.amazon.com/Craftsman-Dig...&qid=1462507336&sr=1-7&keywords=clamp+ammeter

Shop around spend 35+$, make sure it can measure DC amps as well as AC, cheapos do only AC

Like all lead acid batteries, they require a true 100% recharge every so many deep cycles, or they will lose capacity faster.

AGMS seem to lose capacity faster when not returned to 100% more regularly, and all of them enjoy higher charge rates, upto 30% on the lower end AGM, and no upper limits on the Lifeline/Northstar/Odyssey AGMs.

When the AGMS get beat down from many cycles without a full recharge, one needs to do the high amp recharge from 50%, and hold absorption voltage until amps taper to 0.5% of total capacity. 
 This might take 10 hours or more!
With the last 1% taking 3.5 of those hours, so even smaller amounts of solar, once it along can maintain the few amps needed to hold absorption voltage  can really help reduce generator run times, and also slightly lessen the load on the batteries around solar noon.

If you go with less expensive AGMS like Deka Intimidator( oft relabelled sold in sams and costco), get another 100Ah capacity so as not to exceed a 30% charge rate on them.

Even if you can't run the generator and hold absorption voltage as long as might be needed/ desirable, 300AH+ of  TPPL AGM batteries will gobble everything up that a 120 amp charger can produce, the Honda 2000 'Should' be able to power it.

The key to getting your money's worth out of 1000$+ of lead acid battery in your stated usage, is get the batteries to ABSV as fast as possible, and hold it for as long as you can.  If you can hold it until the solar can maintain 14.4 to 14.7, and the solar holds it 1t absorption voltage the rest of the day, all the better.

The reason I recommended a Manual adjustable voltage charger/converter, is because the automatic ones might not hit the right Absorption voltage for the battery, and its temperature, and they certainly will not hold ABSV for the time needed. There is little point in running the generator when the charging source prematurely drops to 13.8 volts automatically.  Intermatic sells wind up timers, get a 6 hour one and then no real fear of overcharging.


The Powermax converters are also power factor corrected, meaning they are more efficient.  120 amps on a standard 15 amp household outlet. other brands require a 20 amp outlet for ~80+ amps.

If you get enough solar that can still seek and hold absv when an automatic converter reverts to a lower voltage, that works too, but the solar controller would then need to be programmable too so it can hold absorption voltage instead of the premature float that is so common.
 
Thanks so much SternWake! I've spent a few hours researching

I'm thinking I want a 200Ah bank total, maybe just one big heavy battery. That should power my 5 amp appliance for 20 hours I think if I discharge to 50% (though further if I get a Northstar?).

Which Powermax charger should I get then in amps? You seem to say I should get a charger that is 30% of the total battery bank's amount if it's AGM, which in my case would be the 55 amp charger? But you're also saying if I go with Northstar I can get a 120 amp charger? Man that would be fast! But isn't a Northstar-120amp charger combo going to be really expensive? I don't want to spend more than say ~$1000 for the battery, charger, and inverter together.

How long would a 55 amp charger, being powered by the EU2000, take to replenish 100Ah of my bank? Am I right it will be about 2 hours?

I'm confused why the Powermax you linked to doesn't have the 'smart' 3 or 4 stage charging other folks talk about. What about Mastervolt, Xantrex, or IOTA?
 
A battery can only be recharged so fast to 100%

A good AGM battery can be charged very quickly to 80%, but that last 20% takes 3.5 hours minimum. Charging to 80% is fairly effiecient, the battery can absorb most everything the charger can make, after that it slows down, and more so the closer it gets to full, and getting to full regularly is paramount to battery longevity

If you are trying to run a 600 watt Air conditioner flat out for 3 hours, you are going to have to have at least 300AH of quality AGM to maintain enough voltage to power the inverter and keep the batteries from getting overdischarged.

Below 80% charged, time to 80% is simple math. After 80%, 3.5 hours minimum to 100%, no matter how powerful the charging source.

Read up on the Peukert effect too. Large loads reduce the total available capacity.

A 100 Ah battery can power a 5 amp load for 20 hours, but it CANNOT power a 100 amp load for 1 hour.

Any loads over 5 amps on a 100AH battery reduces the total available capacity. The higher the load, the more significant the capacity reduction.

600 watts at 12.2v is a 50 amp load, but add 10 more amps for inverter inefficiency.

You'd need 1000+ Ah of battery capacity for peukert not to be a factor.

Your not going to power a 600 watt AC off inverted battery power for 3 hours on 200Ah of AGM battery, and not reliably for less than 1000$ in battery and charger, not including inverter or AC or thick copper cabling with professional terminations.

The powermax adjustable voltage unit is one key to maximum charging in minimum time, and the Odyssey or Northstar or lifeline batteries have no issues with huge charging currents. Other AGM batteries are limited to 30 amps per 100AH. No it is not automatic.

Automatic 3/4 stage , and minimum charge time/ max recharge in minimum time.
DO not belong in the same sentence.

Automatic chargers will not hold absorption voltage for long enough, and very likely, not the correct absorption voltage.
 
You might want to consider LiFePO4 rather than AGM batteries. Maybe a bit more expensive up-front, (probably less than you think if you properly size the AGMs) but cheaper in the long-run.
 
SternWake said:
 300AH+ of  TPPL AGM batteries will gobble everything up that a 120 amp charger can produce, the Honda 2000 'Should' be able to power it.

'Should' makes me a little nervous, ought I to go with the 100 amp charger or lower charger instead to make 'sure' the Honda 2000 can power it?  


What's at stake here?  If I get 300Ah of Northstar batteries, a good charger, and a good inverter, can I simply say something like "I'll charge the batteries for about 3 hours for every time I run the air conditioner for 2 hours" and leave it at that?  I realize I might not be getting 'maximum' capabilities out of my system, and I might be shortening the life of the batteries because I'm not discharging/monitoring right, but is that all that's at stake?   I just don't have enough knowledge to do everything exactly right... I'm still reading your initial post over and over trying to understand! Many thanks :)
 
NOt having a honda 2000, or a 120 amp Powermax I am hesitant to say it will absolutely work when the batteries are depleted and easily able to suck up 120 amps. Talk to Errin at Powermax directly, and I recommend ordering the adjustable voltage manual versions directly from him.

Not getting to 100% each recharge will cause the batteries to lose capacity faster. How much faster depends on how close they are getting to 100%, or not. Also if one can plug into the grid every two weeks for 24 to 36 hours and hold absorption voltage until amps taper to 0.5% of capacity, well this can 'reset' the capacity back upto its remaining maximum. But not its 'when new' capacity.

These TPPL AGMS hold higher voltages under higher loads than other lesser$$ AGMS of the same capacity, but then under ~40% charged the voltage will nosedive to the same level as the lessers, and fall to 10.5v(100% discharged) at the same time.

The higher the voltage the battery can maintain, the more efficient the inverter will be, so in a high constant inverter load situation like powering a 600 watt AC, these TPPL AGMS are superior to other AGMS and flooded batteries, AND they can also take HUGE recharging currents, without issue.

Lifepo4 batteries are superior in every way, but they require precise control to not overcharge or overdischarge them, as one over charge/discharge can kill them. $$$$.$$

Bimmel20,

Interesting that the adjustable voltage models have made it to Amazon. Note that the pic shown is a 75 amp unit, with 3 40 amp fuses. The 100 amp unit is 1.5 inches longer and has 4 40 amp fuses. Back when these were first on the scene there were a bunch of 75 amp models being sent to those who ordered 100 amps, my friend being one of them. Not sure if it was an honest mix up or deliberate dishonesty bait and switch. At least with Amazon there is a good return policy, but I would be very surprised if a 100 amp adjustable voltage version showed up if that particular link was ordered.

Do note the adjustable voltage models are NOT 3/4 stage automatic, unless they have significantly altered the design of the units very recently. The ADJustable voltage chargers are manual, single stage NON smart, non Automatic chargers, and will seek the chosen voltage and hold it as long as it has 120vac power to feed upon. Meaning it can overcharge the batteries if left on indefinitely at 14.x volts. This is why I recommend an intermatic 6 hour spring wound timer on these if one wants some measure of protection.

100 amps into a pair of flooded/wet depleted GC-2s is excessive. Trojan recommend a 10 to 13% rate and upto 20% is 'acceptable', and 10% of 232AH capacity would be 23.2 amps, so 100 amps is well over this. If used on 232AH of depleted gc-2 batteries they would nearly instantly reach absorption voltage and start bubbling aggressively away. This is hard on such batteries, and should only really be done when absolute maximum recharging is needed in minimum time. Even then for just 2 flooded GC-2 batteries I would recommend the 45 or 60 amp adjustable voltage powermax for its ability to seek and hold absorption voltage and still recharge to 80% quickly and then hold 14.x volts as long as it takes for Specific gravity to max out at 1.275+ or amps to taper to 2 to 3% of capacity.

'Topping off' requires time at absorption voltages, and not very high currents, It might require 8 amps at 80% to hold 14.8v on a 100AH battery and by 98% it might require only 2 amps, so the 100 amp capacity of a charger for topping off, is unneeded.

These amp figures above are general meant for example, each battery will be different and change as it ages.

There are other adjustable voltage options that one can use to ensure topping up of a battery, as most every automatic charging source will prematurely drop to float voltage. I use a Modified Meanwell rsp-500-15, and there are even super cheap power supplies which can fit the bill too, but with less overhead or safety margin, as a depleted battery can ask for everything a charging source can make, beyonds its limits to be able to dissipate the heat it generates.

Solar with adjustable voltage setpoints is a good way to top up, if the day is long enough, and one has an ammeter and hydrometer or both to know how long to hold ABSV.

Keep in mind true 100% recharge is for maximizing battery longevity. One can certainly compromise longevity intentionally by not worrying so much about getting to 100%. Just do not expect the manufacturer claimed cycle life when not charged to 100%. The manufacturer's claimed cycle life is in LABoratory conditions, when the battery is recharged to 100% after each and every discharge.

One must also keep in mind one can not just cycle lead acid batteries from 50 to 80% over and over. the batteries will fail very prematurely in such usage. Lead acid needs the 100% recharge every so often, and the more often the better.

When they are recharged to 100% often, they can retain their capacity very well cycle after cycle. My Northstar group 27 AGM at 90AH is my only battery, for house and engine, and is over 300 Deep cycles at this point with another 150 to 200 shallower cycles on it, and while not performing like it did when new, is still performing extremely well, because I can meet its high amp recharge and can hold absorption voltage until amps taper to 0.4a at 14.46v most every recharge.

I suspect it would already have been replaced if I never bothered to meet its specific recharge demands, But I do, and work it hard, and it keeps on ticking. I have high confidence in it, so much so that I do not have a dedicated battery for engine starting, even though I have a location and all the wiring hooked up for doing so easily.

That said I am going to go Lifepo4 when this battery's capacity can no longer meet my demands, but I expect that to be some time away.
 
SternWake said:
NOt having a honda 2000, or a 120 amp Powermax I am hesitant to say it will absolutely work when the batteries are depleted and easily able to suck up 120 amps.  Talk to Errin at Powermax directly, and I recommend ordering the adjustable voltage manual versions directly from him.

Not getting to 100% each recharge will cause the batteries to lose capacity faster.  How much faster depends on how close they are getting to 100%, or not.  Also if one can plug into the grid every two weeks for 24 to 36 hours and hold absorption voltage until amps taper to 0.5% of capacity, well this can 'reset' the capacity back upto its remaining maximum.  But not its 'when new' capacity.

These TPPL AGMS hold higher voltages under higher loads than other lesser$$ AGMS of the same capacity, but then under ~40% charged the voltage will nosedive to the same level as the lessers, and fall to 10.5v(100% discharged) at the same time.

The higher the voltage the battery can maintain, the more efficient the inverter will be, so in a high constant inverter load situation like powering a 600 watt AC, these TPPL AGMS are superior to other AGMS and flooded batteries, AND they can also take HUGE recharging currents, without issue.

Lifepo4 batteries are superior in every way, but they require precise control to not overcharge or overdischarge them, as one over charge/discharge can kill them. $$$$.$$

Bimmel20,

Interesting that the adjustable voltage models have made it to Amazon.  Note that the pic shown is a 75 amp unit, with 3 40 amp fuses.  The 100 amp unit is 1.5 inches longer and has 4 40 amp fuses.  Back when these were first on the scene there were a bunch of 75 amp models being sent to those who ordered 100 amps, my friend being one of them.  Not sure if it was an honest mix up or deliberate dishonesty bait and switch.  At least with Amazon there is a good return policy, but I would be very surprised if a 100 amp adjustable voltage version showed up if that particular link was ordered.

Do note the adjustable voltage models are NOT 3/4 stage automatic, unless they have significantly altered the design of the units very recently.  The ADJustable voltage chargers are manual, single stage NON smart, non Automatic chargers,  and will seek the chosen voltage and hold it as long as it has 120vac power to feed upon.  Meaning it can overcharge the batteries if left on indefinitely at 14.x volts.  This is why I recommend an intermatic 6 hour spring wound timer on these if one wants some measure of protection.

100 amps into a pair of flooded/wet depleted GC-2s is excessive.  Trojan recommend a 10 to 13% rate and upto 20% is 'acceptable', and 10% of 232AH capacity would be 23.2 amps, so 100 amps is well over this.  If used on 232AH of depleted gc-2 batteries they would nearly instantly reach absorption voltage and start bubbling aggressively away.  This is hard on such batteries, and should only really be done when absolute maximum recharging is needed in minimum time. Even then for just 2 flooded   GC-2 batteries I would recommend the 45 or 60 amp adjustable voltage powermax for its ability to seek and hold absorption voltage and still recharge to 80% quickly and then hold 14.x volts as long as it takes for Specific gravity to max out at 1.275+ or amps to taper to 2 to 3% of capacity.

'Topping off' requires time at absorption voltages, and not very high currents, It might require 8 amps at 80% to hold 14.8v on a 100AH battery and by 98% it might require only 2 amps, so the 100 amp capacity of a charger for topping off, is unneeded.

These amp figures above  are general meant for example, each battery will be different and change as it ages.

There are other adjustable voltage options that one can use to ensure topping up of a battery, as most every automatic charging source will prematurely drop to float voltage.  I use a Modified  Meanwell rsp-500-15, and there are even super cheap power supplies which can fit the bill too, but with less overhead or safety margin, as a depleted battery can ask for everything a charging source can make, beyonds its limits to be able to dissipate the heat it generates.

Solar with adjustable voltage setpoints is a good way to top up, if the day is long enough, and one has an ammeter and hydrometer or both to know how long to hold ABSV.

Keep in mind true 100% recharge is for maximizing battery longevity.  One can certainly compromise longevity intentionally by not worrying so much about getting to 100%.  Just do not expect the manufacturer claimed cycle life when not charged to 100%.  The manufacturer's claimed cycle life is in LABoratory conditions, when the battery is recharged to 100% after each and every discharge.

One must also keep in mind one can not just cycle lead acid batteries from 50 to 80% over and over. the batteries will fail very prematurely in such usage.  Lead acid needs the 100% recharge every so often, and the more often the better.

When they are recharged to 100% often, they can retain their capacity very well cycle after cycle.  My Northstar group 27 AGM at 90AH is my only battery, for house and engine, and is over 300 Deep cycles at this point with another 150 to 200 shallower cycles on it, and while not performing like it did when new, is still performing extremely well, because I can meet its high amp recharge and can hold absorption voltage until amps taper to 0.4a at 14.46v most every recharge.

I suspect it would already have been replaced if I never bothered to meet its specific recharge demands, But I do, and work it hard, and it keeps on ticking.  I have high confidence in it, so much so that I do not have a dedicated battery for engine starting, even though I have a location and all the wiring hooked up for doing so easily.

That said I am going to go Lifepo4 when this battery's capacity can no longer meet my demands, but I expect that to be some time away.

I do plan to add about 300 watts of solar in the near future, but one step at a time for now and I already have the batteries and generator. I would like to go out on some weekend trips and kind of "test out" the off grid lifestyle. Do you have a specific charger that you would suggest that would compliment my current set up of 2 Duracell GC2's and the 3100/2800 generator while also having an eye to the near future when I add solar? While not the only consideration, price is definitely one. I have a small popup camper that I am working with...
 
The progressives dynamics PD9245is a good converter, and with its remote pendant, can be forced to choose 14.4v, 13.6v or 13.2v. I hear they can also make them so they seek 14.6 or 14.8v custom order.

Batteries like trojan recommend 14.8v absorption voltage at 77f. 14.4v is good, but 14.8v will recharge a bit quicker and more easily prevent and redissolve sulfation.

I do not like the charge algorithm's on automatic 3/4 stage converters from Powermax as they drop voltage to 13.8 as soon as it hits 14.6v. I only like their user adjustable single stage manual chargers for their ability to hold ABSV as long as the user decides to power the unit.

Iota dls 45 and 55 would also be a pretty good charger for a pair of flooded gc-2, but one cannot choose/force the voltage ' stages' as one can with the PD9245, pd9260 or pd9270.

Other charging sources, like solar, will confuse the automatic chargers depending on the battery voltage at the time they are started. Forcing it to seek 14.4v+ is much better than trying to trick an automatic charger into seeking 14.4v by loading the system until voltage falls to 12.6v or below then starting charger/converter.

Thick short cabling between converter and batteries plays a huge part in charging efficacy. Too thin and the converter might think it has reached 14.4v, but the voltage drop on that too long too thin cabling might only have the batteries at 13.8v, which is no good.
 
SternWake said:
A 100 Ah battery can power a 5 amp load for 20 hours, but it CANNOT power a 100 amp load for 1 hour.

Any loads over 5 amps on a 100AH battery reduces the total available capacity.  The higher the load, the more significant the capacity reduction.

600 watts at 12.2v is a 50 amp load, but add 10 more amps for inverter inefficiency.

I'm confused- Home Depot says my air conditioner's amperage is "5 amps," which I thought meant 5amps x 20 hours = 100 Ah

Why is it when one converts the 5 amps to 600 watts it's suddenly a "50 amp load" as you say? So instead of 20 hours the aircon will run only 2 hours?
 
600 watts at 120v is a ~5 amp load
600 watts at 12v is a ~50 amp load

volts x amps = watts
 
SternWake said:
The progressives dynamics PD9245is a good converter, and with its remote pendant, can be forced to choose 14.4v, 13.6v or 13.2v.  I hear they can also make them so they seek 14.6 or 14.8v custom order.

Batteries like trojan recommend 14.8v absorption voltage at 77f.  14.4v is good, but 14.8v will recharge a bit quicker and more easily prevent and redissolve sulfation.

I do not like the charge algorithm's on  automatic 3/4 stage converters from Powermax as they drop voltage to 13.8 as soon as it hits 14.6v.  I only like their user adjustable single stage manual chargers for their ability to hold ABSV as long as the user decides to power the unit.

Iota dls 45 and 55 would also be a pretty good charger for a pair of flooded gc-2, but one cannot choose/force the voltage ' stages' as one can with the PD9245, pd9260 or pd9270.
 
Other charging sources, like solar,  will confuse the automatic chargers depending on the battery voltage at the time they are started. Forcing it to seek 14.4v+ is much better than trying to trick an automatic charger into seeking 14.4v by loading the system until voltage falls to 12.6v or below then starting charger/converter.

Thick short cabling between converter and batteries plays a huge part in charging efficacy.  Too thin and the converter might think it has reached 14.4v, but the voltage drop on that too long too thin cabling might only have the batteries at 13.8v, which is no good.

So the "charge wizard" would not be considered some sort of automatic or smart charger? And the high end of 14.4 volts would not be prohibitive?

Brian
 
Svenn said:
I'm confused- Home Depot says my air conditioner's amperage is "5 amps," which I thought meant 5amps x 20 hours = 100 Ah

Why is it when one converts the 5 amps to 600 watts it's suddenly a "50 amp load" as you say? So instead of 20 hours the aircon will run only 2 hours?

Thats probably 5amps at 110V. If your using an inverter and batteries, then the general rule I use is X10 on the amps. So 5amps at 110V would pull 50amps at the 12v battery. Its a general in the ballpark rule that I learnt and I use it to good results when I decide what appliances to buy for my RV.
 
Powermax tells me the PM3 75 watt would be best for the Eu2000; I'm just confused since it's only ~$150?
 
' best' is quite subjective.

I'd love to tell you that the honda 2000 can indeed power the 120 amp powermax flat out on depleted AGMS, but I can't, I don't know.

In theory I could test the 100 amp powermax when it is flat out, but this would require putting an unnecessary deep cycle on batteries that are not mine, with time I can better spend elsewhere.

I can tell you that 300AH of 50% depleted Northstar, lifeline or Odyssey AGMs can easily drink everything a 120 amp charger can deliver. 3 hours of powering a 600 watt AC will have 300AH of battery in this range or lower.

Keep in mind with lead acid batteries, you only have the top 50% to really work with, going below 50% is significantly harder on lead acid batteries, requiring even more time at absorption voltage to get back upto 100% charged. Without this they just degrade that much faster and have less capacity to deliver each and every discharge, and it just gets worse and worse as one basically just discharges them even deeper each consecutive cycle.


I will not recommend any powermax 3/4 stage automatic charger, only the adjustable voltage manual options
 
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