I use these to charge my portable boomboxes I build. They work great and aren't too much power at once for a nice slow charge on my sealed lead acid batteries.Constant voltage never over chargeWorks well so far. Time will tell how long they last.UPDATE 28/11/21 - I've been using this, but y'know, the issue I wrote about before continues to be a limitation. That is that it simply doesn't shut off soon enough when hooked to a car battery. The battery can be charged to 13.9v and still the thing hasn't powered off. If you're watching it closely, it'll charge your battery, but I don't use it as a "float, trickle" charger because I'm afraid it'll boil off my battery water. I have replaced it with one that cuts off at 12.8v, and which I don't have to worry about forgetting, I can just leave the new one hooked up.So this will charger a car battery, but I do NOT recommend leaving it hooked up. And since mine is, as of today, apparently the top review, I think I have a responsibility to update this.original review below:I bought this because my previous maintainer was stolen by a lowlife from my carport while it was on my car. That being the case, I didn't want an expensive one; this one was $13. Its display lights are simple - charging and finished, plus a light for reverse polarity which I doubt I'll ever need since my car batteries are well-marked and the battery clips are too.The wiring is fairly lightweight, but should be sufficient for .75 amp. I like the fact that they include both battery clamps and a fuse-protected permanent connection for when one is keeping non-automotive batteries topped off.I have to say that having the plug right on the voltage converter, instead of having a wire and plug coming out of it, is less convenient for car charging because it means you need to run you extension cord all the way inside the car hood... at least it does for me since I charge in the driveway. I suppose if you had a garage and a nearby plug and didn't mind tripping over the wire it might be OK, but still I think this sort of design with the plug prongs sticking directly out of the box is not as desirable.The indicator light is nearly too dim to see in the daylight, which is a shame. Fine indoors.In charging my wife's car, the yellow light never did turn green so it remains to be seen if it ever will. When taking the charger off, her battery showed 12.93v so it seems like the charger should have gone to standby mode by then, but it was still pumping in charge.So 4 stars for now, and I'll return to this with updated notions. I like the claimed 3 year warranty which would be great if they honor it, though as noted my last one was stolen. At least this one was $13 instead of 40 like that one.UPDATE 11/18/20I contacted the seller and got an answer back the next day, so good support. They provided info on the voltage switching points, so I tested it on a 12v gelcell battery and indeed it functioned just fine to charge it and then switch back to a maintenance voltage.So based on the low price, the features, the dual cord options, the long warranty, and the good seller support, I've raised my review to 5 stars and I think this is the price leader for now if you don't want to drop a lot of money on one of these.As a minor niggle, it doesn't charge and shut off as quickly as my previous charger rated at .75 amp, but I think that's just plausibly due to a different cutoff voltage, which I'm OK with.I purchased four first they worked so well I purchased four more for my other needs.Love it works as well as it doesThese are great little cheap 12v lead acid battery chargers. I use them for charging sealed lead acid batteries like you find in uninterruptable power supplies (1290's and such).They work great as long as the battery is disconnected from the load, bringing them up kindly to full charge and then "floating" or "maintaining" them at charge indefinitely.What doesn't work is if your battery is still connected to any sort of load. My guess is that the 750ma rate is just too slow to keep up with even tiny loads, so any load on the battery constantly pushes the charger back into "charge" mode.So if you want to charge a battery that is still connected to a load, you might look for a stronger charger. These are great for charging batteries "offline".Don't get me wrong, you CAN charge a battery even when it has a small load, but you'll probably see that it is always "charging" and never getting to "maintenance" mode, which may or may not be great for the battery. I'm not sure.I use this to charge my kid's Powerwheels battery because the charger that came with the toy is trash. So this primarily charges a small 12v sealed battery.The dummy lights help me understand whether it's charging the battery or when the battery is full. There's also a light to let me know I've got my +/- terminals mixed up. And once the battery is fully trickle charged, this will maintain the battery. A great function since I often forget to come back to the garage and unplug the charger... and that's what probably destroyed my kid's prior Powerwheels battery because I'd forget and let it run for days before unplugging it. Now with this smart charger, I don't have to worry about overcharging the battery and shortening its life.As an added bonus, this is great for actually maintaining my lawn mower battery over the winter when it's not busy charging up my kid's Powerwheel.The whole charging assembly is light, with long enough cords, and has so far functioned without a hiccup. Very reliable.Needed a charger for my 12v Generator Battery. Not only was this price great, but the charger worked perfectly to Charge up my new Battery for its first use. Can't say anything bad about this, works as described.Finally had to use this and after the first use the wires detached from the clamp….so much for back up emergency plan.works well for a great price. It's all you will needEspecial para los vehículos que no usamos a diario así cuando ocupamos usarlos no tenemos problema de descarga de bateríaBought 2 to maintain batteries on generators in a remote area.Work as described.