
I eventually settled on this model because once you get this large the "automatic" feature seems to be harder to find, but this one has it. Otherwise you're setting an amperage (like 40A) and a time, and you need to get it right or risk cooking the battery. This removes that risk (unless you choose to use the manual modes, which are all still there).
Decent quality, but it won't likely be an heirloom you pass down through the generations. My first one arrived caved in (and the box was undamaged). Of course Amazon handled that surperbly, but it still added a few days until I had a properly working unit.
This model has both voltage and amperage gauges, and they're analog.
Keep in mind that bigger is not always better. Even though this is rated at putting out 300A, I can't get a normal car battery to take more than 100 or so at best. I presume that's a function of the internal resistance of the battery, but there is indeed a limit to how fast you can charge a lead acid battery. 300A might be overkill for automotive stuff (but might be handy for large trucks, campers, golf cars, etc).

I bought this for my husband for Christmas. First time he used it was last week, and with the 4 Amp Auto feature, it overcharged/boiled a 1,000 amp RV battery. Trying to troubleshoot using another battery, it pegged out the voltage again and started overcharging that battery.
Called Schumaker for a warranty repair, they asked for the serial number. Once they looked it up, they told us the unit was out of warranty. Amazon sold a unit as 'new' with a 36 month warranty, even though it was 'new' in 2009 and now there is not a warranty! Amazon refuses to take it back, so we are going to the local news channel to let everyone know what a SCAM is being ran by Amazon!
Buy Schumacher PSW-70300A Manual or Automatic High Performance Charger Now
This tool offers a range of useful features, which are not available on cheaper devices such as genuine quick charge and starting capabilities. The auto charge feature is better than it was on my last charger because it brings the state of charge close to full. Useful meters indicate what is happening.
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I purchased this charger for a fire house to replace a similar, 20-year-old Snap-On charger that had finally given out.
Pros:
* Durability Not quite as solid as our old Snap-On charger, but acceptable in this day and age when every piece of metal and plastic seems to be thinner than a comparable part from the past. Seems to be built well enough for "fire house" use (and abuse) as well as use in a repair shop and/or home garage. Certainly well above the "made in China" or "Harbor Freight" quality level.
* Microprocessor control, etc. Relatively goof-proof settings mean less chance that people who think they know what they're doing (but don't) will damage batteries or vehicle electronics (or themselves) by setting the controls incorrectly or hooking up the cables backwards. Yellow (charging) and green (charged) indicator lights as well as amperage draw and voltage meters give a good indication of what's actually going on during the charge beyond "oh, the fan in the charger is running, so something must be happening." The timer makes a very subtle "tick" so you know it's not stuck.
* High amperage engine start assist capability Bigger is better when you're dealing with vehicles with two (or more) batteries, and 300 amps is close to the high end of what's available.
* Knobs are solid and easy to grasp I don't expect to need replacements any time soon, and people with big hands or wearing gloves shouldn't have any trouble manipulating them. There's a good, solid, substantial-sounding click when you change the knobs from one position to another.
* Battery desulfation capability, float mode charging capability, and alternator performance testing mode provide additional flexibility and utility.
* Amazon pricing for this unit was the best I could find anywhere on the web or in stores.
Cons:
* Cables are probably adequate, but they don't seem QUITE as hefty as those on our old Snap-On unit or those on some jumper cables I've used (yes, I'm aware that fatter cables aren't always better because sometimes the fat is from extra layers of plastic insulation being wrapped around the cable to give the illusion of heft/quality). The cables are apparently up to the task and do not get hot during the charging process. The clamps also have a stop on them so that they won't slide down a battery post.
* The control panel has the word "Ampers" on it (should be Amps or Amperes). How embarrassing.
Other:
* I used this unit to charge the batteries on a fire truck that has two mammoth batteries that had been discharged from sitting unused for several months, and the charger worked beautifully.
* Other reviewers mentioned packaging issues. The charger I received was packed in a cardboard retail box, which had been slid inside a plain brown packing box, and the brown box had then been placed inside a larger Amazon box that was filled with the usual crumpled paper and inflated plastic air-pillow packing. In other words, it was packed properly for UPS shipping. The unit was in excellent shape when it arrived with no damage whatsoever.
Bottom Line:
* All things considered, I am very pleased with this charger and have no regrets about purchasing it. I recommend it to others with needs similar to mine.
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This unit was received in damaged condition. I read a previous review written about this item and completely agree with that reviewer that person's first unit was also damaged. The unit comes in its own cardboard box with no outer box and the handle is packed tightly against the cabinet of the unit with very little clearance to the cardboard box. Therefore, if it is banged against other packages during shipping, it is very likely to be damaged. Hard to believe the manufacturer doesn't know this or doesn't care, I guess. The unit looks like it will work OK, but the shipping packaging is very poor. Large dents on the sides and top of the unit. With Amazon's return policy, you cannot return this item and must dispose of it as "hazardous material". (Remember, this weighs about 40 pounds). I ended up talking with an Amazon customer service person and she was very helpful. They offered to order a replacement unit or fully refund my purchase price. I opted to try ordering again. She processed an order for another unit for me at no charge so I will see how that one looks/works when it arrives. Good luck if you order one of these! Follow up comment: Amazon sent a replacement unit to me within 5 days. It was triple-packed in cardboard boxes and arrived with no damage. Works great have had to use it to jump an older 5.0 L engine and with a dead battery twice and engine started right up this unit has plenty of power!
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