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The Rich Solar 40 Amp 12V DC-DC Battery Charger (model RS-DC40) charges a 12V auxiliary or house battery from your vehicle's starter battery and alternator at a nominal 40A (500W). It works as a battery isolator and a charger in one, keeping the two batteries separate so each can use its own chemistry.
Set the mode switch for standard lead-acid, gel, AGM or LiFePO4, and the charger handles the rest with smart or conventional alternators. Rich Solar designs it for RVs, vans, boats and commercial vehicles, in a fan-cooled metal case measuring 10.3 x 7.4 x 3.1 inches.
STD, GEL and AGM settings charge in three stages, bulk, absorption and float, at 14.4V, 14.6V and 14.8V, then float at 13.5V, 13.5V and 13.8V. The LFP setting charges to 14.6V in two stages and skips float. A POWER mode holds a steady 13.2V for use as a power supply.
The RS-DC40 runs on 10 to 16V DC from the starter side, and its isolated input and output keep the charging output stable. Expect the input to draw up to 50% more current than the charge current at full output; Rich Solar lists input current limiting at 68A or less.
The charger stays off until its D+ terminal detects 12V from the ignition circuit, so it only charges while the engine runs and won't drain the starter battery. Rich Solar recommends 18 to 16 AWG solid copper wire for this connection, which isn't included.
Feed 12V to the LC terminal and output drops to 50% of the rating, 20A on this model. Rich Solar suggests it for older or low-capacity alternators and weak power sources.
When a lithium battery's protection circuit has turned it off, the charger automatically sends a small current to wake it and begins a normal charge once the cell voltage is correct.
The RS-DC40 protects against over-voltage, under-voltage, over-temperature, reverse polarity and short circuit, and a red ERROR LED lights on a fault. Integrated fans cool the case, and idle draw is under 0.6A.
An RJ11 port accepts an optional temperature sensor, sold separately, for temperature-compensated lead-acid charging. Rich Solar says not to use it with lithium batteries.
RVs. Recharge the house battery bank on travel days, even when the house bank is lithium and the starter battery is lead-acid.
Camper vans. Put up to 40A back into a 12V LiFePO4 or AGM house battery from the alternator.
Boats. Charge a house battery from the engine. Rich Solar recommends having a qualified electrician or installer verify boat installations.
A basic isolator connects the batteries while the engine runs, so the house battery sees the alternator's voltage as-is. The RS-DC40 keeps the batteries isolated and charges the house battery with a profile matched to its chemistry, including LiFePO4.
All three share the same input range, battery modes and features. The RS-DC40 is rated 40A (500W) and weighs 4.9 lb. The RS-DC20 (20A, 250W) is shorter and lighter, and the RS-DC60 (60A, 750W) is longer and needs heavier wiring and larger fuses.
For runs up to 10 ft (3 m), Rich Solar's wiring table calls for 6 AWG on the starter (input) side and 8 AWG on the house (output) side, with heavier wire for runs up to 30 ft (9 m) as listed in the specifications. Recommended fuses are 60A on the input and 50A on the output. Use ring terminals and one common negative ground.
Install the charger close to the house battery in a dry, cool place with some airflow and at least 1.97 inches (5 cm) of clearance on all sides, secured with four screws. Keep it out of salty, wet or damp areas and direct sun; above 122°F (50°C) ambient, it stops until it cools. It works with 12V batteries only.
Yes. The input and output are isolated, and Rich Solar notes the two batteries can be different chemistries. Set the switch to LFP for a LiFePO4 house battery.
Not when the D+ terminal is wired to the ignition circuit as Rich Solar directs. The charger only runs when that circuit is live with the engine running.
The box holds the charger and its user manual. You supply the battery cables, fuses and D+ wire, plus the LC wire and temperature sensor if you want those functions.
No. It's for 12V batteries only, and the manual says batteries must be above 10V (lead-acid) and can't exceed 15.5V.
The Rich Solar 40 Amp 12V DC-DC Battery Charger charges a lithium or lead-acid house battery at up to 40A from your alternator, with ignition control, battery isolation and a 20A low-current mode. If you'd like help choosing wire and fuse sizes for your install, the Outbound Power team is happy to help.
Rich Solar 40 Amp 12V DC-DC Battery Charger Specifications |
|
|---|---|
| Model | RS-DC40 |
| Input | |
| Nominal Input Voltage | 12V DC |
| Operating Voltage Range | 10-16V DC |
| Input Current Limiting | 68A or less |
| Idle Consumption | Under 0.6A |
| Output | |
| Rated Output Power | 500W |
| Rated Output Current | 40A |
| Operating Current Range | 37-43A |
| Low Current Mode (LC) | 20A (range 18-22A) |
| Float Charging Current | 3-5A |
| Ripple Voltage | Under 500 mV RMS |
| Efficiency | Over 85% (at 14V DC, 30% load) |
| Charging | |
| Battery Types | AGM, flooded, gel, sealed, LiFePO4 (LFP), lithium-ion |
| Mode Switch Settings | STD, GEL, AGM, LFP, POWER |
| Charging Profile | 2-stage for lithium, 3-stage for lead-acid |
| Charging Voltage | STD 14.4V, GEL 14.6V, AGM 14.8V, LFP 14.6V, POWER 13.2V (±0.1V) |
| Float Voltage | STD 13.5V, GEL 13.5V, AGM 13.8V, LFP none (±0.1V) |
| Absorption Time Limit | 3 hours maximum (default) |
| Lithium Activation | Automatic |
| Protection and Controls | |
| Protection | Over-voltage, under-voltage, over-temperature, reverse polarity, short circuit |
| High Voltage Shutdown and Restart | 16V and 15.5V |
| Low Voltage Cut-Out and Restart | 8V (lead acid) and 10V |
| Over-Temperature Stop | Ambient above 122°F (50°C) |
| Fault Indicator | Red ERROR LED |
| Ignition Control | D+ terminal, 18-16 AWG solid copper wire recommended (not included) |
| Current Limit Terminal | LC terminal, 50% current limit (wire not included) |
| Temperature Sensor Port | RJ11, optional sensor sold separately, not for lithium |
| Wiring and Fusing (Rich Solar Recommendation, 0-3% Voltage Drop) | |
| Input Cable to Starter Battery | 6 AWG (0-10 ft), 4 AWG (11-20 ft), 4 AWG (21-30 ft, 3-10% non-critical drop) |
| Output Cable to House Battery | 8 AWG (0-10 ft), 8-6 AWG (11-20 ft), 4 AWG (21-30 ft) |
| Input Fuse | 60A |
| Output Fuse | 50A |
| Physical | |
| Enclosure | Metal, with integrated cooling fans |
| Operating Temperature | -4°F to 122°F |
| Installation Clearance | 1.97 in (5 cm) on all sides |
| Dimensions | 10.3 x 7.4 x 3.1 in |
| Net Weight | 4.9 lb |
| Package Dimensions | 13 x 9 x 5 in |
| Gross Weight | 6 lb |
| Certifications | CE, RoHS |
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