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4.5
This DEWALT DXAEC2 Professional 2-Amp Automotive Battery Charger and Maintainer appears to be a basic float charger. Once the battery voltage goes below the float voltage of about 12.85 V, the yellow charging light comes on, and it charges at up to 14.25-15.0 V, about the same as a car alternator (see updated details below). It only gets slightly warm if charging for a long period, otherwise is cool. Doesn't seem to vary the voltage with temperature.I now have two of these. The one has an observed float voltage of 12.90, and the other 12.83.I've had the one outside under the hood at minus 5 degrees F, on a 75 foot extension cord, kept doing its thing. While it's probably not waterproof, it's fairly closed up, so a few drops of water probably won't kill it.It's probably safe to leave this connected continuously as a maintainer on sealed lead-acid (SLA) auto batteries. I've left it connected to a vehicle for a few months with very good results, vehicle always started right up.Note that before starting the vehicle, it's probably best to completely remove this charger from under the hood, otherwise cords could get pulled into belts, burned on hot surfaces, etc. If you do leave it attached to the battery when starting, be sure it's clear of all belts, and I also recommend unplugging it first. That way it won't go into charge mode while the vehicle is starting and running, perhaps giving the electronics in it a longer lifespan. Leaving the charger powered while starting could expose it to voltage and current spikes from inductance, etc. I also put a note on my dash reminding me or anyone else that the charger must be removed before starting and driving away!Seems like a well-made, durable product. The clips are a bit sub-par (cheap plastic, not a great grip on the teeth), but sufficient for the task and amperage. I've used one of them regularly for a couple years now. I would say it's suitable for anything up to a car or small truck, as a maintainer or slow charger.For Gel batteries, I am a little hesitant to use it, because often they have a maximum charging voltage of 14.4 volts. This charger seems to exceed that, briefly at least. Whether that's okay with the relatively low amperage is hard to say, but using too high of a voltage with Gel batteries can cause bubbles to form in the gel, which reduces the performance. I'd check the maximum charging voltage of your Gel battery.DETAILSBelow are some detailed observations on charging, for those who want the nitty gritty. I didn't measure the current coming out of this charger, just the voltage while it was connected to SLA automotive batteries.When connected to a battery which is NOT installed in a vehicle (so it has no load on it), the charging circuit turns on and off fairly frequently (every 20-30 mins?) for brief periods. Once the battery drops below about 12.85 V, it will charge at up to about 14.9-15.0 V for a few minutes, then will shut off.When connected to a battery which IS installed in a vehicle (meaning there is always a small load on the battery), the observed charging behavior is somewhat different, and seems to be two-stage.In this case, when the battery drops below the float voltage of about 12.85 V, the charging circuit will come on and the voltage will begin rising gradually. This stage is probably constant-current charging at 2 amps. Once the voltage reaches about 14.85 V (which could take minutes or hours depending on the battery's state of charge), it will stay there for a few minutes, then will drop to constant-voltage charging at about 14.25 V. (Constant voltage charging means the voltage is held steady, which means the current is likely allowed to decrease below 2 amps. It's basically topping it off at this stage.)It will stay at that 14.25 V for maybe 30-90 minutes (depending on any minor loads on the battery), then will shut off. The battery voltage will then slowly decrease. In a healthy battery, it will level off at about 12.90 V. With most vehicles, there is still a small load even when off, so it will continue slowly decreasing.After usually a few hours, the voltage will reach the float voltage of about 12.85 V, and the two-stage charging cycle will begin again.All of this tells me that this is probably a pretty safe maintainer for a vehicle's battery, unlikely to overcharge by very much over time, yet keeping the battery well topped off. SLA batteries like a full charge, it helps their lifespan. So if you're not driving your vehicle every few days, keeping it on this maintainer continuously, or at least turning on the maintainer for a couple hours daily, will likely improve your battery's lifespan and performance.If you'd like to monitor what this or any other charger is doing, and keep an eye on a battery more closely over time, I found the ANCEL BM200 PRO 12V Lead Acid Battery Monitor to be very handy. You can see my review for that as well.
