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

4.5 4.5 out of 5 stars 796 ratings

$78.75
FREE Returns
100 Amp
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Brand WirthCo
Color Black
Product Dimensions 6.7"D x 10.5"W x 2.3"H
Item Weight 16 ounces
Specification Met ip62

About this item

  • Water resistant (IP62) - suitable for marine use
  • Priority charging for starting battery. Not suggested for Lithium Batteries
  • Automatically charges auxiliary battery
  • Manual override for starting battery
  • Over current and surge protected for vehicles with electronic systems
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Important information

Legal Disclaimer

This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm.


From the manufacturer


Battery Isolator

Product Features

  • Water resistant – suitable for marine use (IP62)
  • Priority charging for starting battery.
  • Includes mounting bracket.
  • Over current and surge protected for vehicles with electronic systems.
  • Automatically charges auxiliary battery.

WirthCo 20090 Battery Doctor 75 Amp/100 Amp Battery Isolator

Battery Doctor 75 Amp/100 Amp Battery Isolator

WirthCo Battery Doctor Battery Isolator - 75/100 peak ampere is a state-of-the-art, fully automatic, dual battery controller that is suitable for any vehicle with an auxiliary battery. Smaller and lighter than other standard battery isolators, the battery isolator employs electronic switching control technology. High-performance electronic isolator allows you to charge two batteries from a single alternator, and keeps the starting battery isolated from the second battery.

Also, with a single push of the override/reset button, you can change the batteries to parallel mode for jump-starting.It includes a mounting bracket and over-current and surge protected for vehicles with electronic systems.

About WirthCo Engineering, Inc.

WirthCo Engineering, Inc. is entering our fourth decade as a prime manufacturer of practical products for making life easier and safer - at home, in the workplace, on the road, in the campground and on the water. We are grateful for valued employees and customers and we are dedicated to continuing growth based upon integrity and service. We are also proud of our heritage of providing innovative quality products.

Product Description

WirthCo Battery Doctor Battery Isolator - 75/100 peak ampere is a state-of-the-art, fully automatic, dual battery controller that is suitable for any vehicle with an auxiliary battery. Smaller and lighter than other standard battery isolators, the battery isolator employs electronic switching control technology. High-performance electronic isolator allows you to charge two batteries from a single alternator, and keeps the starting battery isolated from the second battery. Also, with a single push of the override/reset button, you can change the batteries to parallel mode for jump-starting. This is water resistant; making it suitable for marine use (IP62). It includes a mounting bracket and over-current and surge protected for vehicles with electronic systems. For over 30 years, WirthCo has been a prime manufacturer of practical products for making life easier and safer. California Prop 65 - Warning, This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.

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

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


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  • Unit^Instruction Guide
  • Product guides and documents

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    Price$78.75$107.99-9% $104.99
    List:$115.41
    $43.44-23% $114.87
    List:$149.97
    Delivery
    Get it as soon as Thursday, May 16
    Get it as soon as Thursday, May 16
    Get it as soon as Thursday, May 16
    Get it as soon as Thursday, May 16
    Get it as soon as Thursday, May 16
    Customer Ratings
    Easy to install
    4.6
    4.6
    4.5
    4.4
    Value for money
    4.0
    4.0
    4.3
    4.2
    Tech Support
    4.1
    4.1
    4.1
    Sold By
    Amazon.com
    Amazon.com
    Amazon.com
    Amazon.com
    LJ Distribution LLC
    input voltage
    240 volts
    24 volts
    12 volts
    12 volts
    weight
    1 pounds
    1 pounds
    0.95 pounds
    0.7 pounds
    8 ounces

    Looking for specific info?

    Customer reviews

    4.5 out of 5 stars
    4.5 out of 5
    796 global ratings

    Customers say

    Customers like the performance, ease of installation, value, and weight of the battery charger. For example, they mention that it works great, the instructions are good and simple, and it's worth the money. That said, some complain about the quality and charging.

    AI-generated from the text of customer reviews

    120 customers mention95 positive25 negative

    Customers like the performance of the battery charger. For example, they mention it has been working great, has no problems, and the jump start feature works fine. Some say it's easy to install and looks like a good product.

    "...Turns out it is working properly, I was just not getting the proper voltage due to a pre-existing alternator condition...." Read more

    "BEST PRODUCT ONTHE MARKET! SUPER EASY INSTALL AND WORKS AS IT SHOULD. WILL BE BUYNG MORE FOR AUXILIARY POWER IN OTHER VEHICLES!" Read more

    "...It was really great while it worked, but now long after I have shut the engine off, the blue light continues to burn...." Read more

    "...the isolator installed for [three years] and it has worked great, no problems.I would like to bring up a few points:*..." Read more

    75 customers mention71 positive4 negative

    Customers find the installation of the battery charger to be easy. They mention that the instructions are good and simple. Some say that the wiring is pretty simple.

    "...Installation was easy and followed very easily. I have a 7 month old starter battery...." Read more

    "BEST PRODUCT ONTHE MARKET! SUPER EASY INSTALL AND WORKS AS IT SHOULD. WILL BE BUYNG MORE FOR AUXILIARY POWER IN OTHER VEHICLES!" Read more

    "Extremely easy install. Works as advertised. Very happy with this purchase, so far...." Read more

    "...It works well, requiring very little in the way of installation. (couple screws, couple wires, etc)...." Read more

    17 customers mention17 positive0 negative

    Customers appreciate the value of the battery charger. They say it's the best product for the money, well worth it, and a great buy.

    "This is a great product. Inexpensive, economical, and well built item...." Read more

    "For the price this is really good...." Read more

    "...A MUST HAVE FOR EVERY BOAT. Best product for the money. Never have to charge my house battery again!..." Read more

    "...Good quality parts at a very reasonable price. Contains everything you need to hook up a second battery and instructions were good...." Read more

    8 customers mention8 positive0 negative

    Customers are satisfied with the size of the battery charger. They mention that it is very compact and fits almost any where.

    "Nice compact gizmo , comes with easy to use mounting bracket .Simple hook up , yea no problem ,mounted on firewall under hood of my camper tow..." Read more

    "This isolator is very compact and easy to install. I am using it to charge a deep cycle auxiliary battery that powers my inverter...." Read more

    "It works fine keeping batteries charged. Easy to install and fits almost any where." Read more

    "Use it for my Polaris RZR and works as described. Very compact and can mount in small corner." Read more

    6 customers mention6 positive0 negative

    Customers like the dual battery of the charger. They mention it's easy to install, and does a great job of separating two batteries. Some appreciate the ability to isolate and bridge batteries as necessary on the fly.

    "...I like this unit's ability to Isolate and Bridge batteries as necessary on the fly. Works as advertised and the user selected option are convenient...." Read more

    "This thing does a great job. Separates two batteries, one for truck and one for the plow itself. Charges one full, then goes two the other one...." Read more

    "...a second battery on my UTV, very simple to install and seperate's the batteries and keeps both charged up. excellent device." Read more

    "Awesome product for a two battery setup. Easy to install." Read more

    43 customers mention23 positive20 negative

    Customers are mixed about the charging of the battery charger. Some mention that it's excellent, keeping their dual battery system charged nicely. However, others say that it started to fail to charge suddenly, and that it continues to draw power from the vehicle battery after engine off.

    "...Works as advertised and it keeps my Yello top charged." Read more

    "...UPDATE****Batteries, mostly the starter battery was low. Decided to put it on a charger while still in the vehicle...." Read more

    "...Will not drain starting battery, one way flow only lets you charge house battery AFTER starting battery is fully charged." Read more

    "...With that said, it will only charge your secondary battery IF your main battery is charged past 13.4V...." Read more

    36 customers mention9 positive27 negative

    Customers are dissatisfied with the quality of the battery charger. They mention that the Isolator trips with a flashing blue light as soon as the power is applied, it has broken off on its own after about a year of solid use, the bolts are fragile material and breaks when tightening the nut, and it did not even last a YEAR. The red light stays blinking with vehicle on and off, and the light fault indicating an overcurrent condition.

    "...kept draining while the aux batter remained charged...but still no blue light...." Read more

    "...worked, but now long after I have shut the engine off, the blue light continues to burn. I tried pushing the reset button. It didn't work...." Read more

    "This is a great product. Inexpensive, economical, and well built item...." Read more

    "...charging voltage will be seen on the starter side and the relay will not disconnect. This may or may not be what you want. See below...." Read more

    6 customers mention0 positive6 negative

    Customers are dissatisfied with the power of the battery charger. For example, they mention that it shuts itself off after a minute, the blue light remains on when the engine is off, and the aux battery was suddenly losing power at a rapid rate.

    "...I start the vehicle and the blue charging light never came on. Thought, well I will drive around and see what happens...." Read more

    "...When the AGM is slightly depleted, the blue light shuts off about a minute after I shut the ignition off. This is apparently very normal." Read more

    "...the main battery without losing power, but found out that it simply shuts itself off. It’s a good thing...." Read more

    "...I was at first concerned that the charging light was remaining on when the engine was off...." Read more

    Dual Battery & Battery Isolator Set-up
    5 Stars
    Dual Battery & Battery Isolator Set-up
    I like this unit so far. Installation was straight forward. I replaced a mechanical battery isolator made by Cooper Industries (Sure Power 1314) with the Battery Doctor. I like this unit's ability to Isolate and Bridge batteries as necessary on the fly. Works as advertised and the user selected option are convenient. Instructions are good and simple. Make sure you install a circuit breaker/Fuse on the AUX battery as denoted in the instructions. It needs to be 150 Amp. I installed this unit on my Polaris Ranger. Pictures included. I don't drive my Ranger every day so the 30 mA standby power draw is a concern. So as stated in the instructions insert a switch between the unit and the Ground. Black wire with ring.
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    Top reviews from the United States

    Reviewed in the United States on April 22, 2018
    Size: 150 AmpVerified Purchase
    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!
    30 people found this helpful
    Report
    Reviewed in the United States on March 15, 2024
    Size: 150 AmpVerified Purchase
    BEST PRODUCT ONTHE MARKET! SUPER EASY INSTALL AND WORKS AS IT SHOULD. WILL BE BUYNG MORE FOR AUXILIARY POWER IN OTHER VEHICLES!
    One person found this helpful
    Report
    Reviewed in the United States on December 19, 2018
    Size: 150 AmpVerified Purchase
    Extremely easy install. Works as advertised. Very happy with this purchase, so far.
    UPDATE: I've adjusted the 5-star rating to a 3-star rating.
    Well, the honeymoon is over. LOL. The unit has been installed for a week and it's already acting fritzy. It was really great while it worked, but now long after I have shut the engine off, the blue light continues to burn. I tried pushing the reset button. It didn't work. I had to disconnect the entire unit to get the blue light to go off. When I reconnect it, the red light burns solid, as it should. I turn on the engine, the blue light clicks on. I shut the engine off...the blue light stays on. I've come back hours later to find it still burning. The only way to get it to turn off is to disconnect it. It's seems to be a defective unit. I'll probably be sending it back, unless there is some insight that WirthCo can share with me.
    The aux battery IS an agm battery, so that might have something to do with it. If this is normal behavior for the isolator when connected to an agm, my apologies. I will correct my rating back to 5-stars.
    UPDATE FOR THE UPDATE:
    The blue light will stay on when the AGM battery is completely full, which mine often is, since I wired it to a solar panel,too. When the AGM is slightly depleted, the blue light shuts off about a minute after I shut the ignition off. This is apparently very normal.
    31 people found this helpful
    Report
    Reviewed in the United States on June 3, 2018
    Size: 100 AmpVerified Purchase
    Update 2023: when my FLA bank died I replaced it with 150Ah of LiFePO4. I assumed I'd need a DC-DC. But I fired it up with the VSR in place and it works fine. Over the last ~20 runs, the average state of charge before start was 72%, bank voltage 13.20v. Charge acceptance after start was 0.183C (27.39A). See note below about using a switch to deactivate the VSR when desired.

    ------

    I've had the isolator installed for [three years] and it has worked great, no problems.

    I would like to bring up a few points:

    * folks often say that this voltage-sensing relay connects the Aux battery when the starter battery is "fully charged"; that's not really what happens. Per the manual and my observation it makes the connection when the starter battery is >= 13.4v. Lead-acid chemistry batteries take hours to get "fully charged" (100% state of charge). In practice this means you'll start the vehicle and a few seconds later the relay will 'click' and you are connected. I don't know but I suspect this stepping-up in load is easier on the alternator.

    * if you are charging the aux battery[s] from another source while the batteries are connected (engine running, or recently turned off) any 13.4v+ charging voltage will be seen on the starter side and the relay will not disconnect. This may or may not be what you want. See below.

    * you can put a switch on the slim ground wire to deactivate the isolator. This might be useful if you want to do something like equalize the house batteries without feeding that voltage back to the vehicle. [I installed a High Voltage Disconnect (a few bucks here on Amazon) to disconnect the Doctor when solar raises the house side above 14.1v.]

    [I read a report about one of the connectors getting overheated - I suspect that person had a loose connection that overheated and melted the plastic. Remember to check your connections when you maintain the battery bank!]
    17 people found this helpful
    Report

    Top reviews from other countries

    Translate all reviews to English
    Dee
    5.0 out of 5 stars excellent
    Reviewed in Canada on February 8, 2024
    Size: 150 AmpVerified Purchase
    just solid
    Jp C
    5.0 out of 5 stars Buen funcionamiento!
    Reviewed in Mexico on February 7, 2019
    Size: 100 AmpVerified Purchase
    Hasta el momento a funcionado bien, es de buena calidad.
    Customer image
    Jp C
    5.0 out of 5 stars Buen funcionamiento!
    Reviewed in Mexico on February 7, 2019
    Hasta el momento a funcionado bien, es de buena calidad.
    Images in this review
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    Customer image
    One person found this helpful
    Report
    Carolyn Clairvoyant
    5.0 out of 5 stars Good Quality
    Reviewed in Australia on September 5, 2020
    Size: 150 AmpVerified Purchase
    Just purchased a solar system for the caravan and this product was highly recommended to compliment and stop battery drainage. The product is as explained and is of good quality .
    Cody
    5.0 out of 5 stars Canadian tough
    Reviewed in Canada on August 23, 2019
    Size: 150 AmpVerified Purchase
    I had to buy a battery isolator because I had a small draw on my main battery.

    It was very nice, and useful. It isolated the second battery from the first battery 100% .

    If my first battery was completely dead, I just popped the hood and push the button and the vehicle started without any problems .

    Installation was as easy as it gets, and everything you need is included.

    Shipping was fast, and this thing worked very well in the coldest environment of Canada .
    One person found this helpful
    Report
    Sorrenson
    5.0 out of 5 stars works great without having to add switches etc
    Reviewed in Canada on August 10, 2021
    Size: 150 AmpVerified Purchase
    I previously used a cole hersee on my last truck.it worked great but required external switches and led. This unit is smaller, cheaper and required no extra switch or light.

    Seems to work great and is electronic vs solenoid so time will tell Very pleased so far

    2020 chev. suburban, install required 2 x 150 Amp breakers plus 30 Amp breaker hard wired to trailer feed. The second battery in the truck powers and recharges my trailer battery and allows effectively endless use as every time we drive the truck it recharges the battery and then we can reconnect to the trailer using extension cable
    the ability to boost the truck is a nice bonus which saved me on my last truck as the battery aged but this one is still young and the battery isn't dying yet
    update.. year later 8 camping trips 50,000 kilometers more on the truck and this unit is working great very very pleased