Diesel Truck Battery Charger vs Gas Truck Charging: What Changes
A gas truck can usually be charged with a standard 10A to 15A charger. A diesel truck often runs two batteries and may use a 24V system, so it does better with a charger that handles 12V and 24V and puts out more current. The charging steps are the same. The difference is the size of the job and how well the charger matches it.
E-FAST TK2500Best overall
PZ.P 215Best color screen
NEXPEAK EU5-NC315Longest cablesWhy diesel and gas trucks charge differently
Both engine types use a lead-acid starting battery, and both batteries charge the same way. The difference comes from the truck's setup. Diesel engines use high compression and need a lot of cranking power, so diesel pickups commonly carry two 12V batteries wired in parallel. Many heavy and commercial diesel trucks go further and use 24V systems.
A typical gas pickup has one battery. That makes it the easier case for a charger. A small unit will do the job, just slowly if the battery is deeply drained.
Two batteries in parallel act like one larger battery, so there is more capacity to refill. A small charger can take a very long time to finish the job, or it may never bring both batteries to a full charge.
Diesel vs gas charging at a glance
The table below sums up the practical differences. Check your owner's manual for your own truck, since setups vary by model and year.
| Factor | Gas truck | Diesel truck |
|---|---|---|
| Typical battery count | Usually one | Often two in parallel |
| System voltage | 12V | 12V on most pickups, 24V on many heavy trucks |
| Charger size needed | Modest current is often enough | More current saves time on large batteries |
| Voltage support to look for | 12V | 12V and 24V |
| Cold-weather concerns | Real, but less demanding | Higher, because hard starts drain batteries faster |
| Maintainer use | Helpful for parked trucks | Very helpful for work trucks that sit between jobs |
Charging two batteries on a diesel truck
Two batteries in parallel should be kept in balance. If you charge only one, the pair can wear unevenly, and the other battery keeps pulling on it. You have two good ways to handle this.
The first is to charge them together. Clip the charger's positive lead to the positive terminal of one battery and the negative lead to the negative terminal of the other, at opposite ends of the pair. Because the batteries are linked, the charger treats them as one larger battery. This is the simplest method, though it takes longer.
The second is to disconnect the batteries and charge each one on its own. This gives you a clearer view of each battery's condition and is useful when one seems weaker than the other. It also means more handling, so wear gloves and eye protection.
If your truck has AGM batteries, make sure the charger supports them. Our best battery charger for AGM batteries page compares chargers with AGM modes.
Picking amps and voltage
For a diesel pickup, our best battery charger for diesel truck page suggests 15A to 25A as a good range, and the chargers listed there run from 10A to 40A. Higher current charges big batteries faster. Very small chargers are better kept for maintenance than for recovering a drained pair.
For a gas truck with a single battery, a lower-current charger is often enough. A multi-stage charger with a maintainer mode will keep it ready between uses. Our best battery charger page covers general-purpose options.
Here is how a few chargers from our diesel page compare on published specs:
| Charger | 12V current | 24V current | Stages | Extra |
|---|---|---|---|---|
| E-FAST TK2500 | 25A | 15A | 8 | Booster mode for 12V only, 3.7 lb |
| PZ.P 215 | 15A | 8A | 9 | Color screen, 6.7 ft cable |
| NEXPEAK EU5-NC315 | 15A | 8A | 9 | Color screen, 8.9 ft cable, 2.39 lb |
| E-FAST TK-1200 | 20A | 10A | 7 | Desulfation, maintainer mode |
Features worth having on either truck
A few features matter more than the raw amp number:
- Multi-stage charging, so the charger moves from bulk charge to float without overcharging.
- Maintainer mode, which holds a parked truck at full charge.
- Temperature compensation, which adjusts the charge for hot and cold garages. The PZ.P 215 listing notes an operating range of 14°F to 82°F, so check that range if you charge in a very cold shed.
- Reverse polarity protection, which guards against clipping the leads on backward.
- Desulfation or repair modes for batteries that have sat unused. The E-FAST TK2500 listing describes a 16-hour repair mode, though repair modes cannot revive every battery.
How to charge safely
Lead-acid batteries can give off hydrogen gas while charging, and the acid inside can burn skin and eyes. Treat the job with care.
Follow these steps for either truck type:
Charging steps and safety notes
Work through these steps in order. Always read your charger's manual first, since connection order can differ slightly between models.
- Park the truck in a ventilated area, switch off the ignition and remove the key. Keep sparks, flames and cigarettes away.
- Put on safety glasses and gloves.
- Confirm the battery voltage, 12V or 24V, so the charger setting matches.
- Make sure the charger is unplugged. Connect the positive clamp first, then the negative clamp, following your manual for where to attach it.
- Select the battery type, such as AGM or flooded, and the current if your charger allows it.
- Plug in the charger and let it run through its stages. Do not charge a frozen or swollen battery, and stop if a battery gets hot or smells of rotten eggs.
- When done, unplug the charger before removing the clamps, negative first.
Which one should you buy?
If your truck is a gas pickup with one battery, a mid-range charger with maintainer mode covers most needs. If you own a diesel pickup, lean toward a charger with enough current for two batteries and 12V and 24V support, since that gives you room if you add a second vehicle later.
Some drivers also want help with a dead battery on the road. A combo unit may suit that need, and our best battery charger and jump starter combo page compares those options. Note that the E-FAST TK2500's booster mode works on 12V batteries only, so check what your truck's system needs before you rely on any assist function.
Frequently asked questions
Can I use a gas truck charger on a diesel truck?
Often yes, as long as it matches your system voltage. The catch is speed. A small charger may take a long time to refill two large batteries, and it may be better suited to maintaining than recovering.
Can a 24V charger charge a 12V truck?
Only if it supports both. The chargers on our diesel page support 12V and 24V and detect or let you select the right one. Never assume a 24V-only unit will work on 12V.
Should I leave a charger connected all the time?
Only if it has a maintainer or float mode. Those modes hold the battery at full charge without overcharging it. A basic charger without them should be unplugged when the charge is done.
Do I need to disconnect the batteries to charge them?
Not always. Many people charge a parallel pair together with the batteries still connected. Check your owner's manual, because some trucks have electronics that call for disconnecting first.