Renogy 12V 40A DC-DC Charger
#11 in 40 A and upFull review
A cheap, quiet way to add alternator charging to a van or camper with a lithium house battery. Pay more for Victron if you want built-in Bluetooth.
Amazon $179.99$179.99
The Renogy 12V 40A DC-DC Charger is the better DC-DC charger overall, rated 3.0 to 2.6. The Renogy 12V 40A DC-DC Charger leads on value. The Sterling Power BB1240 40A wins on efficiency. The Renogy 12V 40A DC-DC Charger costs $201.66 less ($179.99 vs $381.65).
Sterling Power BB1240 40A
#21 in 40 A and upFull review
For boats and vans where keeping the start battery charged matters as much as the house bank.
Amazon $381.65$381.65
Prices were last checked November 2, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Renogy 12V 40A DC-DC Charger for value ($4.50 per amp ($179.99, 40 A) vs $10.04 per amp ($381.65, 38 A)).
- Choose the Sterling Power BB1240 40A for efficiency (98% peak efficiency vs 94% peak efficiency).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 40 A and up DC-DC charger; a clear win is highlighted. How we rank explains each one.
| Factor weight | Renogy 12V 40A DC-DC Charger | Sterling Power BB1240 40A |
|---|---|---|
| Overall rating | 3.0/5 | 2.6/5 |
| Value 30% | 92 $4.50 per amp ($179.99, 40 A) | 34 $10.04 per amp ($381.65, 38 A) |
| Charge current 20% | 0 40 A | 0 38 A |
| Efficiency 10% | 67 94% peak efficiency | 100 98% peak efficiency |
| Features 20% | 25 smart alternator support | 25 smart alternator support |
| Warranty 20% | 25 2-year warranty | 25 2-year warranty |
Specifications
| Renogy 12V 40A DC-DC Charger | Sterling Power BB1240 40A | |
|---|---|---|
| Charging | ||
| Charge current | 40 A | 38 A |
| Input battery | 12 V | 12 V |
| Output battery | 12 V | 12 V |
| LiFePO4 profile | Yes | Yes |
| Smart alternator support | Yes | Yes |
| Peak efficiency | 94% | 98% |
| Isolated | No | - |
| Solar | ||
| Solar input | No | No |
| Build | ||
| Bluetooth | No | No |
| Weight | 4.1 lb | 1.8 lb |
| Warranty | 2 years | 2 years |
| Released | 2025-09 | - |