Battery Chargers


CTEK Power Inc


Battery Charger


Vehicle Battery to Auxiliary Battery




Lawn Mower





CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty

CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty

Item # CTEK40186

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CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty Vehicle Battery to Auxiliary Battery CTEK40186
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  • Reviews (2)
  • Q & A (150)
  • Videos (1)
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  • Why etrailer?

CTEK Power Inc Battery Chargers - CTEK40186

  • CTEK Power Inc
  • Battery Charger
  • Vehicle Battery to Auxiliary Battery
  • Car/Truck/SUV
  • Lawn Mower
  • Boat
  • RV/Camper
  • DC to DC
  • Charges/Maintains
  • 12V

  • Uses a vehicle alternator or solar panel for a power source for automotive, truck, tractor, marine, or RV use
  • Ideal for charging vehicles that do not have access to power grid
  • Works well with the CTEK SmartPass (CTEK56676 - sold separately)
  • 2-Year warranty

40-186 CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty

Replaces CTEK Power Inc CTEKD250S (56-677)

Video of CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for CTEK Power Inc Battery Chargers - Battery Charger - CTEK40186 Review

Speaker 1: Today we're taking a look at the CTEK dual battery charger. This unit is a 20 amp on board charger that can charge your service batteries while on the move. It charges the service batter either from an alternator or from a solar panel or from a combination of both. With selectable charge voltages, the charger is optimized also, for AGM batteries. It delivers a fully automatic five step charge that will charge, condition, and maintain any 12 volt lead acid service batter from 40 to 300 amp hours. This unit can be connected directly to solar panels, and it has a built in regulator, and maximum power point tracker to ensure that maximum power is generated from a solar panel.

It can also deliver a maintenance charge to the starter battery from a solar panel or the service battery.It does work well in conjunction with the CTEK smart pass that's available at and sold separately with part number CTEK56676. I also want to point out that located here on the top portion of the unit, you have a series of indicator lights. These lights make it very easy to know when there's an issue. You take the lights that show up. You look in the included manual, and you look up the fault indications to see what the issue is, and the recommended resolution to fix the issue.I do want to go over the inputs with you real quick.

Now, all these terminals are able to connect very easy. You can take that out, make your connection, thread it back in, then it can be tightened all the way down with an Allen wrench. Basically, right here, this is the input solar panel. This one right here is input alternator. This one right here is the output for the service battery, and this one right here is your ground connection.

You have two small cables on this side. The red one is smart alternator cable. The black one is AGM cable. Then this right here is your temperature sensor. When it comes to the input, that's 11.5 to 23 volts or 25 amps.

Output, maximum is 14.4 volts or 20 amps. Battery capacity is 40-300 amp hours, and the recommended solar panel size is 50-300 watts.Now when it comes to the actual dimensions of this unit, I took a measurement edge to edge going this direction, got a measurement of about four and 5/16 of an inch. Length, just measuring the base was about seven and a half inches long. The overall thickness or height from bottom to the very top was about two and a half inches tall. Mount holes are separated apart from one another going this direction by about three and 9/16 of an inch, and then this direction on center by about six and 9/16 of an inch.That's gonna do it for today's look at the CTEK dual battery charger.

Customer Reviews

CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty - CTEK40186

Average Customer Rating:  5.0 out of 5 stars   (2 Customer Reviews)

- CTEK40186

I ordered two of these, one to charge the battery in our 4runner and one to charge the battery in our camper trailer. These were a better choice for us because they bulk charge at 14.7 volts. Our batteries which are Batteries Plus X2 Power need 14.7-14.8 volts for a full charge. This battery is made by Northstar and is their Pro Series Battery. it came within a few days and well packed. I have never been disappointed ordering from etrailer. Great communication and service. 611923

- CTEK40186

Mine was a simple project. I used this CTEK unit to keep a large auxiliary battery property charged in the back of a pickup truck. This setup was critical for powering a CPAP machine enabling me to sleep at night. After 36 days on the road in Canada and Alaska I'm pleased to report flawless results. With 10,400 driving miles, including much washboard gravel this charger is perfect... I soon forgot it was even there. 565635


Ask the Experts about this CTEK Power Inc Battery Chargers

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  • How to Charge a Trailer Battery for Use with a Bulldog Jack
  • What you described is actually the best solution! Connecting your battery to 12V Power wire from the 7-Way on your trailer is a great way to provide a maintenance charge on your battery to operate a Bulldog jack like part # BD500199. Mounting a battery inside a box like part # 329-HM300BKS inside your trailer will further help to keep your battery safe from the elements (although battery boxes do a pretty good job at that). Please note that the 12V power from your vehicle will not...
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  • Wiring a Trailer With Dual Batteries and Solar Charger
  • Let's try and take this one at a time to make things easier; to start with the black wire from the 7-way plug (the 12V) should be run to the pair of 12V batteries you already have in the battery box. In terms of grounding they will be grounded through your charger, such as in the accompanying diagram of the CTEK D250S Dual Battery Charger # CTEK40186, which you would want to use with the SmartPass CTEK56676. The LED lights each need to be grounded to the frame of your trailer; they...
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  • Best Way To Power an Enclosed Travel Trailer
  • I do have a few options for you to power a cordless drill, lights, and coffee pot inside you enclosed travel trailer but using a solar panel would not be the best or most cost effective setup. Basically, you are going to end up having to cover the entire roof of your trailer to power the above items. Instead, I recommend purchasing a 12 volt auxiliary battery like the one you would find in a car and then using a power inverter like part # WC3720 as well as a battery charger like part...
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  • Adding a 7-Way Trailer Connector to a 212 Subaru Outback and How to Charge Trailer Battery
  • I do have a video that will be very helpful when installing a 7-Way connector on your 2012 Subaru Outback. I have linked that video for you. But not all parts of the video will apply to your situation simply because of the type of brake controller you are using. So you can just ignore those parts. You will need # ETBC7 which comes with the 7-Way and the wiring and other accessories you will need. The installation is not difficult and if you have even a little experience with automotive...
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  • Recommended Vehicle to Trailer Battery Charger with Solar Power Option
  • The CTEK battery charger # CTEK56353 is a great charger for when you have shore power, but will not work for a vehicle to trailer battery charger. To charge your trailer battery from your Outback 2.5i, you will need a different type of charger. If you are a fan of the CTEK brand, then you would want the CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty # CTEK40186. This will allow you to use your vehicle battery to charge your trailer battery without draining your vehicle...
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  • Can Trailer Battery Be Charged from Vehicle, Solar Panel, and Wall Outlet Charger
  • Basically you'd want the CTEK D250S Dual Battery Charger # CTEK40186 to cover the solar panel and alternator charging of the battery and then when wanting to charge the battery from shore power you'd want a charger designed for that like the # CTEK56353. You can install the quick connects of this kit to the battery and easily connect the charger when needed. This would not require the removal of the D250S either. Basically it would just be a matter of letting the trailer charger setup charge...
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  • Recommended Trailer Battery Charging System for Enclosed Motorcycle Trailer for Tools and Mattress
  • You can absolutely use a battery in your trailer to do all the things you desire. You will simply want to get a deep cycle battery and get the amp hour rating you desire. The CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty# CTEK40186 along with the discontinued CTEK SmartPass Energy Management Unit for CTEK D250S DUAL Battery Charger CTEK56676 are a great combination for that as the D250S alone will not work well on the high-capacity deep cell batteries. Instead...
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  • How to Connect Auxiliary Battery to Popup Camper 7-Way for Off Grid Camping
  • If you were wanting to just plug in your current 7-Way on your popup to a 7-Way that is connected to your auxiliary battery then you could install the Hopkins # HM47210 on your trailer. Then you would need to ground the white wire to a clean, bare-metal surface on your trailer and run some 10 Gauge Wire # 10-1-1 from the Red wire on this connector to your battery. Even though this would work it wouldn't be as clean as just hardwiring your battery into the 12V Power circuit on your trailer....
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  • How To Install an Electric Winch On a Lund Boat Trailer
  • The Fulton XLT Powered Winch part # F500620 comes with a 15' long strap that is sufficient for use on boats up to 20' long. According to my research, your 2018 Lund 1875 Impact is just under 19' so this winch should be perfect for you in regards to length. The strap cannot be replaced with a longer option but this should not be needed anyhow. If you do need a longer strap then you would want to use the Dutton-Lainson StrongArm Electric Winch part # DL25200 instead as it comes with a 20'...
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  • Installing DC Power And Power Inverter To Cargo Trailer
  • For DC electricity, I can help you out. You can run a 10 gauge wire like # 10-1-1 sold by the foot from a 6-way or 7-way connection from the 12V to a deep cycle 12V battery and then run the battery to a ground on the trailer. You can use a solenoid like # TR118665 in your tow vehicle if you want to ensure you don't drain the vehicle battery when your truck isn't running. This will isolate the deep cycle 12V trailer battery. To charge your battery, you can use a CTEK D250S DUAL Universal...
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  • Adding a Battery to a Trailer with a 4-Way Connector
  • To run a charge line to your battery you will first need to install a 7-Way on your trailer. This can be done using the Epicord 7-Way Molded Trailer Plug with Junction Box # 277-000141. The Black wire in the junction box is the one that will carry the 12V power. Just simply use a ring terminal like part # 44-5310A and run 10 Gauge Wire # 10-1-1 to the positive terminal on your battery. The 4 wires that are currently on your trailer and tow vehicle are only for the lights and are not...
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  • Can a CTEK Battery Charger be Used to Charge a Battery Through 7-Way on Trailer
  • The CTEK D250S Dual Battery Charger # CTEK40186 can be spliced into the 12V Power wire from the 7-Way on your trailer. It then connects to your trailer battery and provides a maintenance charge. This basically just help to keep your battery from draining, it will not necessarily charge it. To charge your battery you will also need to add a solar panel like part # PTW2997 and connect it to the CTEK battery charger as well. The CTEK charger will then from the solar panel and your 12V power...
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  • Powering a Refrigerator in a Trailer While Towing
  • Some items in a trailer or RV will run off of 12 volt DC power or AC power so if your fridge runs when not connected to shore power then it will run off of the battery. That battery can receive a maintenance charge from the 12 volt circuit on a 7-Way trailer connector but the fridge would draw power faster than the 12 volt circuit can charge. What you would need to do to provide the best charge to the battery is use a DC to DC charger while you are towing such as # CTEK40186. If the...
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  • How to Use an AC Powered Air Conditioning Unit on a DC Powered Travel Trailer
  • I do have a way for you to install an AC powered air conditioning unit on your travel trailer that operates on DC power but the 12 volt power circuit on the 7-way trailer connector will not be sufficient to power an inverter running a 10,000 btu air conditioning unit. A 10,000 btu air conditioner in going to require around 2,000 watts for startup and 700 watts of continuous power to run. These figures are averages and you will want to check your unit for exact specifications. If you...
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  • DC to DC Charger and Solar Panels for Best Charging of Multiple Batteries
  • The CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty # CTEK40186 has a maximum output of 20 amps. When used with the (discontinued) CTEK SmartPass Energy Management Unit for CTEK D250S DUAL Battery Charger CTEK56676, my contact at CTEK said it has a max amperage output of 120 amps not the 80 they have previously stated in the past. This combination will allow 14.4 volts and 120 amps to pass to your batteries whether using solar or alternator. He also stated that you can...
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  • Comparing CTEK D250S and SmartPass vs Redarc DC-DC Charger
  • I reached out to my contact at CTEK and the CTEK D250S Dual Battery Charger 12V- 20a, 5 step, Heavy Duty # CTEK40186 does utilize the Maximum Power Point Tracker (MPPT) as well. When partnered with the (discontinued) Smartpass CTEK56676 you will be able to run your fridge/freezer as you stated. The Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1240D will also be able to accomplish this so it is a better option for this application. You will also need the fuse kit # 331-FK60 for this...
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  • What Fuses Are Needed When Using CTEK D250SA Battery Charger with SmartPass 120
  • I spoke with my contact at CTEK regarding the fuses needed when using the D250SA Dual Battery Charger # CTEK40186 with the SmartPass 120. He did state that because of the start assistance that the SmartPass 120 provides, they highly recommend using a 300 amp fuse and not a 120 amp unit. You will also want to use a 30 amp fuse instead of a 25 amp before the solar panel input.
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  • What Would Allow Solar Panel Charge Kit to Charge Trailer Batteries as Well as Charge From Outlet
  • You can use the solar panel charge kit # 34272628 with the battery bank of your camper and still charge the batteries with a separate charge source (vehicle alternator, power outlet) but you'll also want the CTEK D250S part # CTEK40186 which balances the charge between the two sources and prevents any backfeeding or other issues like you mentioned. So basically you'd run your two charge circuits to the CTEK and then it would charge the batteries. See attached picture.
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  • Trailer Battery Charger and Power Inverter for Coleman Pop-Up Camper with Deep Cycle Battery
  • For a DC battery charger to maintain your trailer's deep-cycle battery I suggest the Redarc In-Vehicle BCDC 40-Amp Battery Charger # 331-BCDC1240D. This unit installs in your vehicle and delivers charging and maintenance current to keep your trailer battery topped off. This is made for high-capacity batteries of 200 amp-hours and above. It also allows the option to add a solar panel to provide a secondary power input. You will also need MIDI Fuse Kit # 331-FK60. A lower-price option...
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  • Can the Tekonsha Two Stage 12 V DC Battery Charger # 2024-07 be Used for Deep Cycle Battery
  • You are on the right track with your thinking, and I do have a solution for you, but the Tekonsha Two Stage 12 V DC Battery Charger # 2024-07 that you referenced is for smaller breakaway batteries and will not work for your application. Since you are wanting to charge and maintain a deep cycle battery you will need to use the CTEK D250S Dual Battery Charger # CTEK40186 instead. This comes with a way to connect your battery to the alternator as well as a solar panel like part # TLA7713...
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  • Recommended Trailer Wiring To Charge Battery And Use Solar Panels
  • To wire your vehicle battery 12V to charge a trailer battery, I recommend using a 40 amp In-Line Circuit Breaker - Perpendicular Mount Bracket # 9510 along with # 10-1-1 to wire your trailer connection. In order not to drain your vehicle battery, I recommend you use the Tow Ready Battery Isolation Solenoid # TR118665 to only allow the trailer to draw power when the vehicle is running. You will need to use an ignition-controlled circuit in your truck to activate the solenoid. The radio...
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  • Can Solar Panel 287-32407 be Used with CTEK DC to DC Battery Charger for Two 12 Volt Batteries
  • If you only used solar panel # 287-32407 with the CTEK battery charger # CTEK40186 it would not be able to charge up two 12 volt batteries. It would keep them from draining when sitting but to charge up the batteries you would want to have the charger connected to a 12 volt circuit from a trailer connector or directly attached to the output of the alternator. The CTEK charger does have a pulse-maintenance stage. It has 5 stages of charging: 1) Desulfation stage is the initial charging...
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  • Battery Charger and Solar Panel for Winch Battery on Car Hauler Trailer
  • You can use your truck 7-way 12V power circuit to maintain both the trailer's breakaway battery and a utility battery that operates the winch. But keep in mind that this 12V power feed is strong enough to maintain batteries but is NOT able to re-charge two depleted batteries. So you will want to use a shore-power AC charger like CTEK 3300 12-Volt Universal Battery Charger # CTEK56158 to fully charge both batteries before a trip; then the 12V feed can maintain them as you travel. A good...
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  • DC Power Battery Charger for Maintaining Service Battery on Dump Trailer
  • For charging a dump trailer's on-board battery each of the vehicles towing it needs to have a fully-functioning 7-way trailer connector. The 7-way includes an auxiliary 12V power circuit that is carried on the pin at the 1:00 position as you view the socket (please see the linked photo). This circuit can deliver trickle-charge power to the trailer battery, but to keep it fully charged you will want to install a heavy-duty DC to DC charger like # CTEK40186 that takes in that same 12V power...
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  • Trailer Battery on Load Trail Keeps Dying
  • I understand that you have an issue with the trailer battery going dead which then in turn does not allow the air compressor for your airbags to kick on but I am failing to see how that affects the trailer brakes. The trailer brakes should receive a signal from the brake controller on the tow vehicle is they are all electric. If you instead have hydraulic brakes that are controlled via an electric over hydraulic actuator then the actuator will need to receive 12 volt power from the tow...
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  • Simple, Clean and Temporary Solution To Top Off Trailer Battery
  • There are a couple options for you to charge the battery when the solar power panels have not produced enough to charge the battery. However, there is not going to be a temporary way to charge the battery from your vehicle's battery. If you wanted to truly charge the battery from your vehicle's battery, you would want to use a CTEK D250S Dual Battery Charger part # CTEK40186 which is designed to connect to the solar panel and the vehicle's alternator to charge the auxiliary battery....
    view full answer...

  • Is a Diode Needed to Prevent Backfeeding from Trailer to Tow Vehicle
  • There is a possibility of back feeding but this should not really be of a concern as the odds of it happening are slim to none. If you did choose to use a diode then you would need one rated for the components it would be powering. The highest rated diode we carry is the Roadmaster Single Park Light Diode part # RM-690 which is rated at 85 amps. There are a few things you will need to take into consideration for your winch and breakaway system. For starters, it is not advised to run...
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  • How to Charge a Battery on an Enclosed Trailer
  • If you are referring to a breakaway battery then you can use the 12 volt (usually black) power wire that is present in the 7-way trailer connector to charge it. I have attached a photo that shows where the 12 volt power wire is located on the 7-way trailer connector. If you are referring to an auxiliary battery used to power a winch or appliances and lights then you are going to need to use a battery charger. For this, I recommend the CTEK D250S Dual Battery Charger part # CTEK40186....
    view full answer...

  • Recommended Vehicle To Trailer DC to DC Charger for Multiple Trailer Batteries
  • Your auxiliary power wire gauge at your 7-way along with the # CTEK40186 will be sufficient to charge your trailer batteries. The CTEK D250S Dual Battery Charger # CTEK40186 will amplify the signal from your auxiliary power to boost it to 20 amps versus the 2-3 amps of a system without the CTEK unit. Changing your gauge of wire to 8 and adding the # DL24086 connections will help slightly but if you are wanting to charge multiple batteries well and more quickly/efficiently, you really...
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Info for this part was:

Edited by:
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Expert Research:
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Expert Research:
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Expert Research:
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Installed by:
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Written by:
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