Will you be using this charger while you still are using DC loads?
If so it might stay in abosrption voltage for longer, and perhaps too long thus overcharging, as these loads make it appear that the battery is still accepting more current than it actually is and a battery still accepting high current is far from being a fully charged battery
I think electrically, relialability wise, Samlex has a pretty good name.
If you are going to power loadswhile trying to threee stage charge, well this charger can do so, but then I believe, without scrutinizing the directions, that when the battery with load dip switch is chosen, the 13.5v voltage chosen for this stage, defeats the 3 stage charging.
The 13.5v might be a little low to prevent self discharge with load on too.
If I hold my battery at 13.5v when fully charged but while still powering loads at about 65F, and then bump voltage upto 14.7, the amperage the battery accepts and the duration it still accepts this higher amperage, indicates to me the battery is now less than fully charged. if I hold it at 13.6v when fully charged, them goose voltage to 14.7v, then the amperage quickly tapers to 0.4a or less indicating the battery is still fully charged and I spin my voltage dial back to 13.6v.
The exact float voltage which will keep a battery fully charged while loads are still present, varies with temperature and any particular AGM battery. 13.5v float, for me, is a deal breaker, at least with my current AGM battery.
13.5v float for days on end on a hot battery in high ambient temperatures, might also prove to be too high.
Also it appears there is no battery tempersature sensor capability, adn the 30 amp model, well I do not know if that is 10 amps max on the three outputs, or if only one output (+) is used, if it will send 30 amps in bulk mode to just one battery.
Everything is a compromise though.
My personal preferences are for manual voltage control., and I generally choose one of two voltages for my powersupply to seek, 14.7v when the battery is less than fully charged, 13.6v when it is.
I understand the desire for automatic, but the automatic, is largely guessing. will the guess be good enough? well, it depends.
When you pluig in to charge, will you have 4 hours, 12 hours or 36 hours? if you have 36 hours then it likely will be good enough, 4 hours, well the 100Ah battery would likely need 6.5 hours from 50% with 40 amps initially available. 12 hours, well there is some leeway. Finish Charging those last few%, at float voltage, well chrging slows way way down.
If the operator sees float voltage/float mode, how does one know the battery is indeed fully charged? well by the amperage the battery accepts at absorption voltage. If the charging source does not allow the operator to boost voltage upto 14.X volts, and see the amperage flowing, then there is no way to know if the AGM battery is fully charged.
UNless one has a lot of faith in green lights, and no desire to question it.
If an automatic source is required, well I like those that still allow an operator to override the automatic algorithm, and force it back to boost or absorption voltage.
While not a perfect charging source by any means, the PD92xx series of RV converter, will allow this.
But the minimum amperage is 45, which will be more like 40 once it gets warm. This 'might' be excessive for the lesser $ AGM batteries.
Well it would exceed the 30% general maximum amperage( 30 amps per 100Ah capacity) that most le$$er AGMS will state.
While I will not outright say you can safely exceed the 30% percent manufacturer max amperage recommendation, please keep in mind this recommendation is designed solely to minimize the possibility of warranty returns.
If the battery does not heat excessively when charging above its recommended maximum, then I feel there is little issue exceeding it.
Also keep in mind that most AGMs used as starting batteries, also have this 30% max amperage recommendation. Yet if the battery were inadvertently discharged to the point it needed a jumpstart, or even to 50%, it will gobble up most everything the alternator can make, which can be 100 amps and this battery will heat up not only from charging at a high rate, but from engine compartment heat too.
So if exceeding the 30% rate were really a big nono battery killer, then the internet's automotive forums would be full of stories about AGMS failing left and right. But most report greater longevity when AGMS are used solely as starting batteries, or perhaps their owners just want to justify the purchase price.
If my desires were for automatic, and my choices were the 30 amp samlex for 200$, or the Progressive dynamics PD9245 converter with charge wizard for 165$, well the PD wins, in my opinion.
The samlex certinaly appears to be physically sexier though.
I do have experience with a PD9245. It briefly exceeded 45 amps on a depleted quality AGM battery but then when hot dropped to about 40 amps. The 3 voltages stages are supposed to be 14.4, 13.6 and 13,2 I measured 14.56, 13.71 and 13.32v. The fan is variable speed and made weird high pitched noises when it was turning slow at lower amperage outputs.
While I cannot recommend any product I have not personally used, I think if one had their heart set on a gargae automatic charger in the 20 amp range, then this one seems to get some kudos on some automotive forums:
https://www.amazon.com/Pro-Logix-PL2320-Battery-Charger-Maintainer/dp/B007ESQW08
I've no idea how well it will actually charge a often deeply cycled hard working AGM. If one is using a sub 25 amp charger, i recommend using the linked product below, or one of the many clones available, on its DC output so one can see how many amps are flowing and at what voltage, and how many AH and WH the charger has delivered into the DC system. I'd say into battery, but vandwellers usually have DC loads running when the charger is charging, so some amperage goes to those loads and not into battery.
https://www.amazon.com/GT-Power-Analyzer-Consumption-Performance/dp/B00C1BZSYO
As I type I have my Adjustable voltage power supply set to 14.7v, and it is delivering 19.7 amps at 14.5v into my battery. The wattmeter on the power supply itself says it is making 29.72 amps at 14.72 volts, and has delivered 26.73AH since I plugged it in. So i Got about 10 amps of load at the moment.
If amps into battery have not tapered to 0.4 or less by the time I goto bed, I will twist the dial to 13.6v, and 8 hours later it likely will be very close to fully charged. If awakening before sunrise and the onset of solar wattage, i will twist dial back upto 14.7, if amperage does not taper to 0.45 or less then I would leave it at 14.7 until it does.
But in general in that situation my solar has no issues getting the battery to and holding it at 14.7v until amps to cross that threshold.
So with that samlex, see if it can do 30 amps on one channel or that 30 amps is spread out on 3 channels at 10 amps max each. Know that if you have DC loads on it, and choose the power supply/battery load setting, it might defeat the 3 stages and hold the battery at 13.5v, which might not allow it to fully charge by the time you unplug.
I know full well the manual charger/ adjustable voltage power supply route I Use is not for everybody, but this battery load/power supply dipswitch also requires human oversight. i;d rather spin a voltage dial after looking at a voltmeter/ammeter for more precise control.
I am not sure the 500$ programmable chargers by magnum or mastervolt can actually do everything I would want an Automatic charger to do, and I would never spend that much dough. My meanwell power supply (rsp-500-15, is 40 amps for ~ 90 dollars.
But it is modified with more heatsinking, ventilation and a better potentiometer for voltage adjustment, as well as the wattmeter.
