12 and 24 Volt Battery Chargers Compared: Samlex SEC and Go Power
An AC battery charger keeps a house, RV, boat or backup battery bank topped up from shore power or a wall outlet. Picking one comes down to three things: the battery voltage (12 or 24), the battery type, and an amp rating sized to the bank. Here is how the 12-volt and 24-volt chargers we carry compare, from 15 to 80 amps.
- Size the charger to the bank: a common rule of thumb is 10 to 20 amps of charger for every 100 amp-hours of battery
- Every charger here is for lead-acid batteries; lithium (LiFePO4) batteries need a charger with a lithium profile
- The Samlex SEC models charge flooded, AGM and gel; the Go Power GPC-MAX is for flooded and AGM only
- Most can also run as a DC power supply, and the Samlex models charge two or three banks at once without an isolator
Pick by your battery bank
| Output | Battery | Battery types | Banks at once | Suits banks of about | ||
|---|---|---|---|---|---|---|
|
Samlex SEC‑1215UL
Small banks
|
15 A | 12 V | Flooded, AGM, gel | 3 | 75–150 Ah | BUY NOW |
|
Samlex SEC‑1230UL
Best all-round 12 V
|
30 A | 12 V | Flooded, AGM, gel | 3 | 150–300 Ah | BUY NOW |
|
Go Power GPC‑45‑MAX
RV converter-charger
|
45 A | 12 V | Flooded, AGM | 1 | 225–450 Ah | BUY NOW |
Samlex SEC‑1250UL
Mid-size banks
|
50 A | 12 V | Flooded, AGM, gel | 2 | 250–500 Ah | BUY NOW |
|
Samlex SEC‑1280UL
Large banks
|
80 A | 12 V | Flooded, AGM, gel | 2 | 400–800 Ah | BUY NOW |
|
Samlex SEC‑2425UL
24 V, smaller banks
|
25 A | 24 V | Flooded, AGM, gel | 2 | 125–250 Ah | BUY NOW |
|
Samlex SEC‑2440UL
24 V, larger banks
|
40 A | 24 V | Flooded, AGM, gel | 2 | 200–400 Ah | BUY NOW |
What size battery charger do I need?
A common rule of thumb is 10 to 20 amps of charger for every 100 amp-hours of battery: a 100 Ah battery suits a 10 to 20-amp charger, a 400 Ah bank a 40 to 80-amp one. If the charger also runs loads while it charges — lights, a fridge, an inverter on standby in an RV — add their current on top. Your battery maker’s maximum charge rate always takes priority.
Is there one charger for both 12-volt and 24-volt batteries?
Not among these: each charger is built for one battery voltage, shown in its model number — SEC-12xx for 12 volts, SEC-24xx for 24 volts. Choose by your bank. A 24-volt bank made of two 12-volt batteries in series is charged as one 24-volt bank with a 24-volt charger such as the SEC-2425UL or SEC-2440UL; never charge one battery of a series pair on its own, which unbalances them.
Can I charge lithium batteries with these chargers?
No. The Samlex SEC and Go Power GPC-MAX chargers are designed for lead-acid batteries (flooded, AGM and, for the Samlex models, gel). Lithium iron phosphate (LiFePO4) batteries need a charger with a lithium charging profile; using a lead-acid charger can undercharge them or trip the battery’s protection.
Can I use these with gel batteries?
The Samlex SEC models are rated for gel cells. The Go Power GPC-MAX chargers are not: Go Power says gel cells can be damaged by their higher charge voltages, so use them with flooded or AGM batteries only.
Can one charger charge two or three battery banks?
Yes, with the Samlex models: the SEC-1215UL and SEC-1230UL charge up to three banks at once and the larger SEC models two, with no separate isolator needed. The Go Power GPC-45-MAX charges a single bank.
Can a battery charger be used as a power supply?
Yes. The Samlex SEC chargers can run as a DC power supply or, with a battery connected, as a DC UPS, and the Go Power GPC-MAX chargers can power 12-volt loads directly. In an RV that means the charger feeds the 12-volt system while you are on shore power.
What is the difference between 2-stage, 3-stage and 4-stage charging?
A three-stage charger runs bulk (full current), absorption (holding voltage while the current tapers) and float (a lower maintenance voltage), which charges fast without overcharging. The Samlex models can be switched to two-stage for batteries that power a load while charging. The Go Power GPC-MAX adds a fourth, automatic equalization stage that periodically boost-charges batteries that sit idle.
Bottom line
Match the voltage, check the battery type, then size the amps to the bank. For most 12-volt house and RV banks, the Samlex SEC-1230UL is the pick; the SEC-1215UL suits a single battery or small bank, and the SEC-1250UL and SEC-1280UL cover larger banks. In an RV with flooded or AGM batteries, the Go Power GPC-45-MAX doubles as a converter. On a 24-volt bank, choose the SEC-2425UL or SEC-2440UL. For lithium batteries, choose a charger with a lithium profile.
