WirthCo 20090 Battery Doctor 75 Amp/100 Amp Battery Isolator , Black

No Luck so far making this device operate. I have a 1971 VW Bus and wanted a aux battery for accessories without draining the starter battery. Installation was easy and followed very easily. I have a 7 month old starter battery. Once I hooked in a ground wire from the aux battery to the frame the red blinking light turned solid red as stated in the instructions. I start the vehicle and the blue charging light never came on. Thought, well I will drive around and see what happens. I found out that my starter battery kept draining while the aux batter remained charged...but still no blue light.Basically it has killed my (fairly new) starter battery and I got it replaced - did find out on numerous occasions that the jumpstart feature works GREAT!!!New starter battery in, same thing exactly as written above. Back to square one. Called tech support, "Tim" was very helpful and said it may be that the circuit board is defective and to return it. I did and waiting on a replacement. I hope it works, but the new starter battery has probably suffered some damage from being discharged frequently. Tech support also mentioned that the unit will not work on a positive grounded vehicle and suggested that may be my issue. No, the VW Bus has a negative ground system....but people who may have a European car that has a positive ground system, this will not work.I will update once I get the replacement, but just don't think it is going to work but hoping for the best. The instructions said it goes into charging mode when the starter battery is above 13.4v....well, that is probably the problem as even the starter battery read 12.8 volts BRAND NEW. Not too sure how to get it up to 13.4?Really disappointed this did not work for me so far and caused a lot of troubles along the way. Looks like many people had a good experience.****UPDATE****Batteries, mostly the starter battery was low. Decided to put it on a charger while still in the vehicle. Next morning to my surprise the blue LED light was on! Turns out it is working properly, I was just not getting the proper voltage due to a pre-existing alternator condition. Got the alternator wiring corrected and this product works as described and like a champ!

If you’re running a second battery, I’d highly recommend getting this. You want to hear it, here it goes.This is a smart battery isolator, charger, and jump starter all rolled into 1 palm-sized device. When installed correctly, you can run power into your secondary battery without affecting the main starting battery. The device stays on for less than a minute between shutting off your vehicle and running parallel with your main battery. So there will be a small parasitic draw for balancing both batteries during that minute.This compact device has 3 connection points, main battery, secondary battery, and pre-wired ground. I highly recommend using a fused 4 gauge or higher cable from the main battery with the fuse or breaker fuse closer to the main battery, and a fused same gauge or lower wire out to your accessories from your secondary battery.Following the instructions I realized it wasn’t charging my secondary battery and wondered why. I later found that my main battery was faulting and after charging it for 8 hours didn’t hold a charge past 64%. With that said, it will only charge your secondary battery IF your main battery is charged past 13.4V.Once I got my main battery sorted (new one), everything was working as it should be. FYI, if either your main or secondary battery loses connection, the isolator will shut off by default. I tried to run the isolator in override mode to swap out the main battery without losing power, but found out that it simply shuts itself off. It’s a good thing.I also found out that this thing has a built in voltage spike regulator, similar to a power conditioner. But I wouldn’t consider it to be a conditioner either. Before this, I had an 80A Stinger battery isolator/relay between the main and secondary battery. I also had a 150A fuse breaker between the secondary to my rear fuse box for my accessories that kept tripping only during vehicle startup without any accessories ON. Battery to battery was fine over 80A relay, but the surge of power introduced by the alternator kept tripping my 150A breaker. After installing this, I had my 250W light bar ON running out of the secondary battery without tripping the breaker during startup. So in short, it can detect power spikes and send the correct signals.I highly recommend this if you’re into the whole secondary battery and trying to stay within budget. What’s $53 compared to potentially burning your entire electrical system (undercharging or overcharging) or getting stuck in a remote place without jumper cables.Hopefully this helps you think about what this thing is actually doing and what you’re protecting. I have a truck with a V8 5.0L engine and a stock 150A alternator, and the 125A/150A works for me. V6 and smaller motors with smaller applications can easily use 75A/100A system.

Seems like a great product . I installed this and first thing on start up it had a flashing red light. look though the instruction and this code indicates its wired wrong. Well i triple check all my wiring and could not find any problems . So i let that lay aside and started the rig and got the voltage up to where it should of cut in and start charging, but that was a no go to. So i called their tech support and they were great,, however this Produit will not work with a lithium ion battery they said. otherwise really like how it installed.

I've been using this for over a year now. My primary battery is an Odyssey Extreme which is the starting battery, and I have a smaller Braille AGM that runs the winch, emergency lighting, and siren/PA. This reliably charges the secondary while preventing unwanted discharge from the primary. It only charges once the main is fully charged just like it should. The override also works well and is easy to use, so the secondary can charge the primary like a jumpstarter if needed.