12V 30A DC to DC Charger with MPPT for Solar & Alternator Input - Smart On-Board Battery Charger for RV, Marine, Car - Charge AGM, Lithium, Gel, Flooded Batteries

Why can't a company provide a clear installation manual / instructions ? When a customer receives a product, the first thing they do is the install. If the instructions aren't clear - I just send it back. The "instructions" for this are terrible. Especially around the ACC function. It appears that the manual says the charger will be ON, when the ACC is <8V - which it always is when the ignition is OFF. How can this be correct ? The charger can't be ON when the ignition is OFF. Even worse: it says the ACC connection is optional - which means the ACC line is ALWAYS 0V. Which means.... you guessed it.... the Charger is always ON. I've jumped through what seems to be intentionally difficult case creation on their website for clarification - but I'm not holding out for an intelligible/understandable answer. (I'm an electrical engineer. If I find this confusing - you will too). Update: Renogy customer support did answer my question quickly: unfortunately they confirmed my suspicion: this charger will try to charge from the start battery even when the ignition is OFF.

I’ve been running this Renogy DC-DC MPPT combo charger in my overland truck build for a while now, and it’s been solid overall, but there are a few things worth knowing before you buy. First off, build quality is great — the unit feels durable and the terminal screws are easy to torque without stripping, which I appreciated during install. Charging performance is strong once it kicks in, but that’s where it gets a little fussy. The charger doesn’t begin charging until the battery drops below about 12.6 volts (around 60% state of charge for lithium), which can be frustrating if you’re hovering mid-range. I personally don’t like dropping my LiPo that low just to trigger charging. Once it does start, though, it pushes a nice solid boost up to 14.4V.The charger defaults to prioritizing alternator input over solar, which is great for truck setups, but solar still does a decent job throughout the day. That said, if your battery stays above the boost return voltage (around 13.2V), the system may just sit idle thinking the battery is full — even when it’s not. This is especially noticeable with lithium batteries that hold a flat voltage curve and can “trick” the controller into staying off. If you want full control, the Renogy Bluetooth module is an absolute must. Without it, you’re stuck on the default presets, but with it, you can fully customize the charge profile, adjust start/stop voltages, and disable float — making it way more compatible with LiPo or LFP battery setups.Overall, the charger works really well once configured correctly, especially for dual-input rigs, but the default behavior out of the box is a bit rigid for lithium users. If you’re building a solar-plus-alternator system and can get the Bluetooth dongle, this is a reliable and efficient charger that’s worth the money.