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I use this in my overlanding setup. I have a 24v system in my Toyota landcruiser and I needed somthing to connect from my 24v to 12v converter to charge an auxiliary battery.
In my situation, my alternator puts out 24v, that will fry this thing. So! I wired it to the output of my converter (12v out).
I asked the question before buying this and everyone said 'no it won't work'. I bought it anyway cuz my options were limited. Well, it works. My aux battery has been staying charged while I drive and my fridge freezer has been staying cold. Mission accomplished.
After recently upgrading our house batteries, and doing much reading. Charging our batteries while we drive with this unit has been great. Since a alternator only gets a battery to maybe 80% this brings them right up with out added stress . Installation was very easy.
Installed this charger as I wanted to run my RV fridge on 120v instead of propane while travelling down the road.
So my truck’s alternator provides power to this charger who in turn charges the RV batteries. Then I have installed a 1000 watt inverter to provide 120v to the fridge. Runs like a charm I can now turn off the propane while on the road
This Renogy 40A DC to DC charger is a very good product with reasonable price. Most of the similar product would cost more than $300, but this one is under $200. I just wired this charger to charge a 12v 100ah lithium iron phosphate battery (second battery) in my camper van from the van alternator. The dip switch setting was a little of confusion, but figured out the setting for 12v lithium iron phosphate battery. My settings are s1 = off, s2 = on for constant voltage of 14.1v (you can set it at 14.4v, but I am afraid of shorting the battery life); s3 = on, s4 = on for constant amp at 40.0 A up to the voltage of 14.6v; s5 = off for lithium iron phosphate battery. D+ signal wire has to be connected to your ignition switch signal voltage (usually +12v), otherwise there will be no output charging voltage. You will see a green light at the output side of the panel if your signal voltage is on. I tested it by hooking up a multi-meter to measure the charging amp, it was 39.5A. I usually camp overnight and need battery power to run a mini-fridge, lighting and cell phone charging using the second battery. When I drive my van during the day, I would like to charge my second battery quickly; thus I chosen 40A charger instead of 20A one. So far so good, only time will tell if this product will be reliable.
Works great but be careful when charging at full speed with the 40A model or higher! I was using fairly thick cable that was originally used for jumper cables thinking if they could handle 700+Amps they could handle 80A. Turned out they started melting in the middle and I had to throw them out! Crazy! I mean they were a heavy Gauge and still couldn't handle the load from this charger for more than an hour! On a better note this charger let's you choose a cut off voltage and battery chemistry type so that's cool! All clearly explained in the direction booklet. There are two small wire connections on the from of the unit. One is basically an on/off switch that's designed to be connected to your vehicle ignition wire or something. Basically it needs positive 12v dc in order to turn on the unit.. The other connection is LC or low current mode. I believe it keeps the charge rate set to half of the units rating, so the 40A model will charge at 20A if the LC 'low current' is connected to a live 12v wire. Handy to know. I've used this charger a lot since getting it and found that it works well! I would definitely buy from Renogy again!
Really pleased with the performance of our 40 amp Renogy DC to DC charger. We power it with the 220a alternator on our Ram 3500 Cummins truck. Use a battery isolator to turn the charger off when the truck's engine is not running (alternator off-line). Ran approx. 25 ft. of 2 gauge welding cable between the truck's positive battery terminal (via a 60a Zcase fuse) and the charger mounted inside our truck camper (used the truck's frame for the negative run). Connect the truck to the truck camper via two pairs of 175a Anderson-type connectors mounted in the truck bed. The 2 gauge cable nets us 40a of charge current with only a 43.5a load on the alternator. You can use smaller (physical size) gauge cable but it will increase the load on the alternator. Just used this charger extensively on a 3000 mi. cross-country trip. We use a 200ah LifePo4 battery pack in our truck camper to power our a/c unit when we stop for breaks on the road. This 40 amp Renogy dc to dc charger does an outstanding job of charging our battery pack back up to 100% SOC in plenty of time for our next break. Gotta love it!