CTEK 40-186 D250SA 5-Step, Automatic DUAL 12 V 20 A Battery Charger

I've had the D250S running in my van every day, for the past 8 months. Once set up, you can pretty much ignore it. It just works. I've got a 105 ah AGM for a coach battery. I had seen some complex-looking coach battery diagrams, and, this setup looked easier, and more my speed. The main difficulty of the setup was determining what size cables to use [NOT anymore; see update at end of review], and getting those cables made. Page 13 of the user manual has the chart that shows what cable size to use for 1 meter, 2 meters, etc. Cable sizes are listed in cross-section area, as mm^2. For example, the positive cable from the CTEK, to the coach battery is supposed to be 6mm^2 for up to 1 meter in length. I had to find a conversion chart online, to find the cable size in AWG. Careful there, when you find such a chart: it's easy to accidentally be looking at a chart that converts cable diameter in mm, rather than cross-section area in mm^2. Anyway, I found that 6mm^2 converts to 8 AWG (which you should verify on your own, along with the other cable sizes).Another consideration in cable selection is whether you might someday upgrade your coach battery capacity; it is possible that I might want to add a second 105 ah battery. If I did, the 20 amp charge current of the D250S would be insufficient, as modern batteries like a charge current of roughly amp-hours / 5 (check your own battery specs). For this case, CTEK makes the SmartPass supplemental unit, to attach to the D250S. The SmartPass has a charging current of 80 amps (but, it is unclear whether the 80 amps is in addition to, or in place of, the 20 amps of the D250S. When using the SmartPass, heavier cables are required. The 6mm^2 cable noted above would then become 16mm^2, which becomes 5 AWG, which, based on availability, becomes 4 AWG. I used the heavier cable so that I would not have to redo the cabling if/when I add the SmartPass.I had a battery shop make up my cables. I had a problem with one of them, and had it redone. For a later electrical project, I got the TEMCo Hammer Lug Crimper Tool 5 Year Warranty. I wish I'd done my own cables for the D250S install. One reason is that heavy cables are more difficult to situate, especially if the terminals are not installed with the correct rotation-orientation on the cable. And, I believe that the terminals I crimped on myself are more secure and efficient than the ones I had done at the battery shop.I've also got a 50 watt portable solar panel that seems to be working fine through the CTEK unit, though it has not been rigorously tested.--- UPDATE ---I have become aware that CTEK is now providing AWG cable sizes, in the manual and/or on their website. That's a nice update, so, no more searching around for conversions. In fact, CTEK's published cable sizes are all one standard AWG size smaller than the conversions I had used. With regard to the cables I had converted, above, CTEK now has 6mm^2 cable listed as 10 AWG, and 16mm^2 is listed as 6 AWG.

Ordered 2 of these, installing flexible solar panels on top of a 2004 TRD Tacoma and a 2007 Tundra, with aux batteries. This all in one box is the ticket. Was able to screw it into the side of the truck bed with sheet metal screws. I did not get the smart pass, since I only have one 108aH battery for 200w of solar panels for each truck. It will be powering a fridge and occasionally a laptop and charging phones etc. I can read the incoming voltage with my voltmeter and it regulates the incoming solar voltage, and outputs a charging voltage to the battery, and isolates the starter battery from the system when alternator not running. A nice, magic, all in one box. Read the manual so you know that it is not reverse charge protected!

I have bought and installed this DC DC charger for my Ford Transit Camper. Connected sources are Solar Panels and Alternator through two separate 30 Amp breakers. My house battery currently at 12.9 Volt and this DC DC charger doesn't charge the battery half the time. It worked perfectly the first month. Not sure how the warranty works on this.

Simple to install, keeps the house battery in good condition and even charges the start battery also.CTEK chargers are good and this unit is such charger, MPPT controler and also replaces a relay to open for charging from alternator. Considering this, the unit is good value for money.

I installed the unit my Ford E350 stealth camping van. I added a 160 watt solar panel to the roof. I bought an 80 ah Lifeline RV AGM battery. The only appliance that I run is a 60 liter ARB fridge/freezer. It ran flawless on a 3 week camping trip through the Canadian Rockies.This product came highly recommended! The review on the Expedition Portal are amazing.The ARB fridge freezer runs 10% of the day and draws at most 7 amps. I cannot keep the battery charged with the alternator and solar panel.I connected the CTEK D250S to the solar panel for 3 days in full sun and it could not charge the battery over 12.4 volts. I tried 2 different batteries. I put a volt meter to solar panel and it puts out 22 volts open circuit.I called CTEK technical support and service representative listened and answered all my questions. I am sending the unit back to CTEK for testing.I will update this review after the unit gets tested and sent back.

got this product to charge the starting AGM and the accessory AGM batteries to run a back seat office setup in a minivan. I can't tell if it's charging at 25A since it'd take over 6 hours of driving to charge the auxiliary battery.Its incompatible with Lifepo4 batteries due to he desalinating feature built in. So basically, the real only practical use for this product is for OLD and LARGE battery banks in RVs etc.. with the companion SMARTPASS 120 and solar arrays up to 25A (400W or so) . But it's useless for a minivan car office - no room for heavy large lead or AGM, the 25A takes too long to charge. Minivans don't have enough roof space for a decent solar setup to be able to replenish the batteries in less than half the day.It's supposed to be an isolator, however it'll stay on for hours after the car is shut off draining the primary battery to charge the secondary .. so when I start the car the car has a error light on to replace the battery because it's drained.. it takes 20-30 min of driving to get the light off.I tried to maintain the starter battery overnight with a 4.5 amp CTEK charger and it keeps this thing on as well however it doesn't charge the accessory battery overnight this way...CTEK tech support suggested to check the ground so upgraded the ground method & wires from 10 (suggested by manual) to 8 gauge to no effect...so gotta get rid of on eBay and get a modern practical setup with a LIFEPO4 compact battery with a 50amp DC2DC charger that charge the battery in a couple of hours of drive-time per day since CTEK offers neither.