NOCO Genius GENM2, 2-Bank, 8-Amp (4-Amp Per Bank) Fully-Automatic Smart Marine Charger, 12V Onboard Battery Charger and Battery Maintainer

I was a little skeptical at first, but went ahead with the purchase based on reviews. After unpacking the item, I was impressed. The enclosure is larger than I expected, but very well built and sealed. The leads are large guage wire and well-insulated. Although description states "on board" charger, the manual cautions against charging when in the vehicle without disconnecting ground lead. I did a bench test where i purposely used a bit of one battery and left the other fully charged. Then connected leads with the two negatives hooked together. As i expected, the charger separately sensed and properly maintained each battery independently.I also very much liked the fact that the charger includes an electronic relay for charge output - this means when charger is de-energized (not plugged in to AC), there is no connection to the charger circuits. For protection of both charger and alternator, do not attempt to leave the charger plugged in while vehicle is in operation -- although there are protection mechanisms built in and it is very unlikely to cause damage, it is not recommended.This charger is now installed in my truck which has a dual battery system (isolated by a solenoid). The truck sits unused most of the time, but now, i don't have to worry about having a dead battery when I need to use it. I've also found that the vehicle's charging system doesn't necessarily do a good job at managing the dual batteries; the alternator charges the two batteries as if they were one thus the primary battery tends to not be fully charged and thus slowly, over time, the primary battery has degraded performance. With this charger, now the primary and secondary batteries are independently maintained and thus both are kept at optimal performance.

First point- If you are considering buying a charger or not buying an onboard charger, stop considering and buy one- imagine a world where you never again have to wonder “hopefully the boat will start today...” by having two batteries and an onboard charger you basically eliminate ever having the possibility for a dead battery again- even if one of your batteries is dead and/or your engine charging system stops working, you have another battery you can switch to so you have plenty of charge to get home... After doing it, it seems like the most obvious investment a boat owner should make and elimates so much heartache- I will never own another boat without it. Specific to this charger, it’s simple to use and install and has worked perfect every time since I purchased it 6 months ago. I cannot say I’ve tried others to compare it to, but I can say this one feels extremely solid and is very easy to use. The only other product I purchased for this is the basic 3 way battery switch- a neighbor who is a retired electrical engineer for a boat manufacturer said the one-way protection fuse stuff they sell is unessisary and I haven’t had any issues. I use one deep cycle and one starting battery. I also would add that prior to installing this, I was occasionally having issues with the radio turning off or shutting off when the boat was off- by adding this, somehow I’ve elminated that issue alltogether.

I put this in my boat for my two battery’s in my jon boat that I rebuilt to a bass boat it was easy to install and it works great I plug it in when I get home from fishing and I leave it plugged up until I go fishing again. Some people say it cooled the battery when they leave it plugged up but that hasn’t happened to me yet it shuts on and off like it should and keeps my battery bank ready to go at all times I definitely recommend this product!!

I love the feel of this charger, feels like a solid unit, but I can't tell you how it works because mine would not power on. First thing I noticed after removing from packaging (nice packaging too btw) is that the terminal rings showed signs of use & one had minor corrosion on it (see pics.)Well, I thought maybe it takes a minute to read battery status before it charges, but left it plugged in for 15 minutes with no change & I couldn't even get so much as an LED to illuminate. Because the whole deal is so simple I hooked it up to the batteries and plugged it in without looking at the instructions, so I thought now's a good time to take a look. To my surprise, some JA had put instructions for a tongue jack in the box & there wasn't any for the charger (see pic.)I suppose enough is enough & I will be returning immediately. Here's to hoping they're not one of these yahoos who try to charge you to return their defective product. I really want to like this product given it's solid feel, simple use, and very high rating, so I will be ordering a new one to see what happens.As a side note, if you haven't picked up on this yourself, someone returned a defective unit that was obviously never even re-inspected because it had a random set of instructions. They just out it right back out there and I was the lucky recipient. I put a hand written note in the box stating the unit is defective & to return immediately. I hope no one out there ever has to see that note.Hopefully the next unit actually works & I will update my review.***UPDATE***New unit came in, and the box was still in the plastic wrapping which was a good start.Same solid feel & it started working right out of the box. I put a voltmeter on each battery before starting, so we'll see how it shakes out.Seems to be working fine, of course time tells all, but I like where things are headed.Old unit is on the way back already, new one came in a few days with no hassle.So far, seems like the right choice to give this charger another try.***UPDATE 2***OK maybe I'm picky.First, I have been using the charger off my workbench and it has worked flawlessly. I've kept it plugged in for days at a time and the batteries are always fully charged. Unit hasn't been hot anytime that I've walked by and held my hand to it, so I count that as a good thing.Went to mount in the boat today, and as I'm considering the different positions I held it upside down by the flange to see if it would fit in a particular spot. Now, I know it wouldn't hang like this when properly screwed, but the fact I could see daylight through the gap is concerning (see pic.)Like I said, when screwed in the corners I wouldn't expect any deflection in the bottom plate if mounted upside down, but unless the internal components are waterproof I wouldn't call this thing sealed by any means. Seems like there should be a gasket or other means of sealing at this joint.Not returning it because I like the way it works, I'm just going to roll the dice & see what she looks like after a full summer on the boat.