My Adventures with PowerMax: A Review

I didn't really see any substantive reviews of PowerMax's PM3 converters prior to purchasing one, so I thought I would post some comments for those who are curious. My bank consists of 3 x 110Ah 12V AGM batteries connected in parallel for 330Ah total. I previously used an Iota DLS + IQ4 and needed to upgrade as I increased the size of my bank.

The PM3 purports to work exactly like the Iota + IQ4, only the charging intelligence is built-in and there's no need to attach an external module. I also prefer the PM3's chassis as it has a nicer higher-quality finish. What I didn't prefer was the complete lack of technical documentation. Sure--these units are plug-and-play, but I still want to know all the details. For example, there's no mention of an equalization stage. Under what conditions will the PM3 send a boost charge to stir the electrolyte? And what happens if I lose grid power? Will I have to disconnect the PM3 from the grid to prevent it from drawing power from my bank?

I engaged PowerMax in a dialogue and more details emerged. According to PowerMax, the PM3 will not draw DC when there's no AC. They also confirmed that there's an equalization stage and that a boost charge will occur once every seven days of float-charging. In other words, the PM3 works exactly like the Iota + IQ4.

The problem was that I couldn't seem to verify any of this, and my own tests appeared to run contrary to what I was told. For example, when I disconnect the PM3 from the grid, the fan still runs, indicating that it is in fact drawing power from the bank. When I plug the converter back in, I'm told it should go into bulk-charging mode, yet that doesn't happen and it stubbornly remains in float mode.

Without really resolving why my PM3 doesn't operate as expected, I learned that PowerMax makes a different version of the PM3 known as the PM3-P. They sent me one free of charge for evaluation. When it arrived, I was surprised to discover that PowerMax has adopted Iota's technique of putting the charging intelligence in a separate module that connects to the unit with an RJ-11 (phone type) cord. The difference is that this module also has a button on it. When it's pressed, the converter goes into bulk/boost mode for four hours. So it's like an Iota + IQ4 only with a bit more manual control (admittedly, you can also force an Iota into bulk mode with a jumper cable, but the button is more convenient).

Now I know what you're all wondering: what happens if you plug an Iota module into a PowerMax and vice-versa? Sadly, I'm too scared to try it and find out, but I did pass the question along to PowerMax for consideration.

The PM3-P itself is physically different from the PM3, resembling more of a prototype, with a smaller but more complex looking chassis, and external cooling fins bolted along the length of the fan side. Speaking of the fan, that aspect of the charger has also changed. Whereas the fan in the PM3 seems to run all the time, the PM3-P's hardly runs at all. Note that the converter still draws at least some power from the bank when it's unplugged, since I can see the green LED pulsing away on the module even when no grid power is supplied. This is exactly how the Iota works; the module retains its state from the bank when there's no grid power so that, for example, it will not lose track of its seven-day equalization cycle in the event of a momentary power outage.

A general lack of documentation is the norm with PowerMax converters, and the PM3-P is no exception. Here are the charging regimens of the various converters:

Bulk   Absorption   Float
  DLS + IQ4   14.8         14.2    13.6
        PM3   14.4         13.6    13.2
      PM3-P   14.4         13.6    13.2

According to PowerMax, the PM3's values can be adjusted whereas the PM3-P's are fixed, so that's something to consider when ordering.

In conclusion, I would say that PowerMax is on the move and definitely giving Iota a run for its money. PowerMax needs to improve their documentation and make it available online, but I sense they're aware of this shortcoming and that more technical PDFs are forthcoming. Only time will tell if these converters are reliable, but I have no reason to doubt it; they look and feel like an Iota line that's been recently refreshed. Since I believe that both Iota and PowerMax converters are more or less equivalent, I would let price dictate your choice.