MaySpare12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charging Relay Dual Smart Battery

Since this was my 3rd attempt/hail mary at completing my dual battery system and running low on funds spent after purchasing 2 lemons twice the price, I figured if I somehow got another lemon then I'd just bitterly accept that it was never meant to be and move on.However, after connecting the relay to the appropriate places, and proceeded to start my car, something magical happened.It works (the lights turned on)!So I'm not sure if I'm that lucky or if they're just that good, but this is awesome!Thanks to this nifty puppy, I now have 3 batteries in my 2001 4runner fully charged at all times with the lead acid starter in the front and 2 AGM batteries in my trunk so I can bring my 1000W microwave for Hot Pockets while I'm in the great outdoors... By microwave, I mean 3 stage speakers/subwoofers with 1000W RMS total (which isn't much IMO, but I'd take that over a hot pocket any day.)Mayspare, I'm a fan.When it comes to most things , you get what you pay for.But every so often, you find those gems where the value far outweighs the price point.So far, this seems to be fit that category like a glove.

Great automatic battery disconnect. Very easy setup to vehicle and no maintenance required when done properly. Customer service is amazing and very prompt on getting back to. highly recommend for anyone setting up dual batteries or other project where you want to isolate high amperage circuit to prevent battery drain.

It is compact and simple and works to keep both boat batteries charged without risk of draining starting battery

I use this to isolate my auxiliary battery from my house battery on my 1987 Jeep Wrangler. I use the auxiliary battery to power an auxiliary fuse block, and what's that battery gets depleted I didn't want it to start drawing from my house battery. I tested this on my DC power supply and it works exactly as advertised. cut in and cut out voltages are exact. Works just as well installed in the vehicle it's been used every day for a couple months now no problems whatsoever.

I've used this in my truck to hookup my second battery and have not had 1 issue with it. Works exactly as it should and never has given me an issue. I've used this with Solar on my truck as well and it worked flawlessly than as well. It's been 6 months since I installed it so I don't recall the instructions if they were any good. I see in 1 review that someone doesn't know what the yellow cable is for and I thought I'd clarify.Black = GroundYellow = *WHEN GROUNDED TO METAL* Will connect both batteries to each other regardless of voltage. ONLY WHEN GROUNDED. You can test it out and hear an audible "click" of the relay connecting the batteries together.Overall it's worked out perfectly, I would recommend for anyone looking to do a similar setup for cheap.

At first this was a great idea. Provides a bypass switch to turn it on manually to connect the batteries. The issue with this is that it connect the batteries whenever it wants to and does NOT kick off when it says it should. I'm not having to reinstall everything with a better isolator.

I have twin engines in my boat and I installed two of these so that after my engines start from their start batteries, then once that short burst of amperage is replaced by the respective engine, these devices note when each start battery has reached full charge and then switches over the balance of the alternator output to charging my inverter bank. I love giving the start batteries priority in the charge cycle.

I installed this kit on my side x side. I run a dual battery set up with my led lights, light bar, sound system, and rear winch attached to it. I noticed that my last couple rides that my amp would clip and cut off if I had the bass turned up. Then it would clip with the subwoofer turned all the way down. I thought it was that my 2nd battery was bad so I purchased a new battery. Guess what.... I had the same problem. So to enjoy my sound system i bypassed the isolator and I'm bumping know! 😎I'll probably try another one because I like the idea of not being sick on the trail due to lack of power! I'll also probably add a 2 Faraday cap for my power hungry 5 channel amp!

Hooked it up on my boat to charge my trolling motor battery. Work great and charges fast.

Works , good buy

Great product for adding a second battery, easy to install and good value.

Very easy to install. It works perfect for a dual battery set up. So far it's holding up great in -25C Temps. I have a bypass switch on order so I can use the yellow wire bypass the isolator if needed.Sure, you can go with a manual isolator however if you want an easy and automatic solution then this is it.

I converted a Ford Transit Connect into a camper and used this isolator in it. Been over a year and still working great. Used wire from jumper cables to connect the main vehicle battery to 2 batteries in the back that I use to power the lights/fan/water pump and usb outlets. No issues with the main vehicle battery draining. Great value for the price.