Renogy 40A DC-DC Battery Charger with MPPT Solar and Alternator Dual Power Input, for Flooded, Gel, AGM, and Lithium Battery

It is a very good charger, it charges very quickly at 550w real with a 4 meter long cable, it doesn't heat up, you can even hold your hand on it, it's barely warm because I chose 4 awg cable from the main battery, which is very important to choose a thicker cable, thin cable is cheaper but it heats up the cable, risk of melting and the dcdc charger is hotter

this is 40amp for it to work right your system has to at least have a 100w alternator or you will just burn out, i have 380w solar 100w alternator charging 2 engine starter batts in parrallel MPPT then charges the lith house bank 2 280w lith in parrallel works great no issue at all i recon the negative stuff here is people having the wrong set up my set up is a sailing yaght.

this charger has failed after two weeks and about three days, I was 3 days into my holiday when I noticed that my voltage had dropped on my lithium 100ah battery, when I checked the dc to dc charger it was not working, not sure when it failed, Now the problem I have is not with the dc to dc charger failing but with the customer service that renogy provide, as other reviews have said it is abismal at best, they want me to do all the testing on the battery I have, the charger, they want video proof of everything and wont accept a return for testing even though I said I would pay for sending and return to me, apparently they dont test them in the UK, so sending back is not happening, the warranty was two years I believe, I have had this since 16 January 2025 and they wont do anythig but keep asking me for more testing and videos of testing.apparently this how the company does warranty claims.You have to prove its not working by testing and videoing everything they ask for.Think twice before buying anything from renogy as if it fails you will get nowhere with customer service or technical for a long time if ever.

Well when looking for the PERFECT. EVERYTHING CHARGER this ticked all the boxes as it.did solar 40a batt batt for.my 300w lithium battrey the one must have was a way to monitor solar and b2b as shore power was never going to happen after meticulous research on the advert it clearly states add renologys bt2 bluetooth dongle via rj connector and the magic will happen well on arrival I paid my auto electrician to fit it got it home and went to plug in the magic box and guess what NO MAGIC HARRY POTTER HAS LEFT THE BUILDING as it has no port to plug in to on repetedly contacting reneolgy to rectify it nope no response so it's not what was described at this point I'm out the instalation cost and hassle and time if I rip it out instead of joy just gutted

Excellent piece. Charging from alternator is incredibly fast. Solar charge also keeps the 2x100 lithium batteries charched all week round. Also saves space as 2 units combined.

Spot on

5 stars because was refunded..

Be aware that many of the reviews here are for a different product. This is a newer product that is cheaper and more compact but does not allow the Bluetooth connection. There is no way to see what is happening with the solar or charging currents etc other than the LED status. Works well as a fit and forget but not as good for those interested in monitoring numbers etc.

Le chargeur n'est pas compatible avec le boîtier Bluetooth Renogy bt-2, car il n'y a pas de port de communications comme indiqué dans la description