Onboard Chargers
ProMariner ProSport HD Review: 20 Amps Total, Not Per Bank
Quick answer
The ProMariner ProSport HD 20A 3-bank charger is genuinely waterproof and uses Distributed-On-Demand technology to split a published 20 amps total across three banks, which is a smaller effective rating per battery than chargers that publish 10 amps to each bank independently.
The ProMariner ProSport HD line is one of the most common onboard chargers fitted as original equipment on new boats, and the waterproof housing is a real, published claim rather than marketing language. This review is built from ProMariner's own published specifications and the consensus of verified owner reviews, not a charger tested in person.
The three bank 20A version reviewed here is the one worth reading carefully, because ProMariner states its output as 20 amps total rather than 20 amps per bank. Distributed-On-Demand technology shares that total across whichever batteries need it most, which is a genuinely useful feature, but it is not the same specification as a charger that publishes a fixed amperage to every bank independently.
What does ProMariner publish about the ProSport HD 20A?
The ProMariner ProSport HD 20A 3-bank waterproof onboard charger uses ProMar Digital Technology, a microprocessor controlled multi stage charge cycle, and a tri-surface extruded heat sink across the upper, lower and rear faces of the case for cooling. Distributed-On-Demand Technology is the headline feature: rather than fixing a set amperage to each bank, the charger allocates its full published output to whichever combination of batteries can use it, so a bank that finishes early frees its share of current for the banks still charging. An LED fuel gauge style display reports charge stage and battery status per bank.
How does a 20 amp total rating compare to a per bank rating?
Charger output is per bank, not total, and manufacturers frequently market the total figure instead. This is the exact case: ProMariner states 20 amps total for this three bank charger, not 20 amps to each of the three banks.
A three bank charger publishing 30 amps total at 10 amps per bank delivers more to each battery than one publishing 20 amps total shared across the same three banks.
Published figure A published engineering, regulatory or manufacturer figure. It does not change because somebody disagrees with it.
| Charger | Published rating | Basis | Effective ceiling per bank |
|---|---|---|---|
| ProMariner ProSport HD 20A | 20 A | Total, distributed | Up to 20 A to one bank, less when shared |
| NOCO GENPRO10X3 | 10 A per bank | Per bank, fixed | 10 A per bank regardless of the others |
Distributed-On-Demand charging is genuinely useful when banks finish at different times, but it does not change the fact that 20 amps total is a smaller published ceiling than 30 amps total at 10 amps per bank.
What the 20 amp rating actually costs you
The catch is that on a fully discharged 36 volt bank, where all three batteries want current at once, this charger's published 20 amp total splits roughly seven amps to each bank rather than the full 10 amps per bank a fixed rate charger like the NOCO GENPRO10X3 delivers, which meaningfully lengthens the overnight recharge. This specific listing also does not publish a selectable lithium charge profile the way the smaller ProSport HD 8A model does in its own listing, so anyone running a lithium bank on this charger needs to confirm charge voltage and mode compatibility before use, or choose a charger listed with a published lithium profile instead.
Step down, step up, or choose one with a lithium profile instead
Step down to the ProSport HD 8A 2-bank for a smaller boat with two batteries, which is genuinely waterproof at a lower price and, on its own listing, does state selectable LiFePO4, flooded, AGM and GEL charge profiles. Step up in per bank output instead to the NOCO GENPRO10X3 or the Minn Kota MK-345PCL, both of which publish a fixed, selectable lithium mode to each of three banks independently rather than a shared total. Anyone with a mixed lead acid and lithium bank on a tight budget should read every candidate charger's own listing for the word lithium before assuming Distributed-On-Demand technology alone makes a charger compatible.
Sources
- ProMariner published specifications for the ProSport HD 20A 3-bank waterproof onboard charger
- ProMariner published specifications for the ProSport HD 8A 2-bank waterproof onboard charger
- Recurring themes in verified owner reviews of the ProSport HD line
Frequently asked questions
Is the ProMariner ProSport HD 20 amps per bank or 20 amps total?
Twenty amps total. ProMariner's Distributed-On-Demand Technology shares that published total across whichever combination of its three banks needs current most, rather than delivering a fixed 20 amps to each bank independently. On a fully discharged three battery bank, that generally means less current reaches each battery than a charger publishing a fixed per bank rating of similar size.
Is the ProSport HD actually waterproof?
Yes, ProMariner publishes a genuine waterproof rating for the ProSport HD line, not merely water resistant, which is a meaningful difference for a charger mounted in a bilge or a compartment that regularly takes on spray. That published waterproof claim is one of the strongest reasons this line gets specified as original equipment on new boats from the factory.
Does the ProSport HD 20A 3-bank support a lithium profile?
Its own published listing does not state one, unlike the smaller ProSport HD 8A 2-bank, whose listing explicitly states selectable LiFePO4, flooded, AGM and GEL profiles. Anyone with a lithium bank should confirm charge voltage and mode compatibility directly with ProMariner before connecting this specific 20A 3-bank model, or choose a charger whose own listing states a lithium mode.
How does Distributed-On-Demand Technology actually work?
Rather than fixing a set amperage to each bank, the charger monitors all three banks and allocates its total published output to whichever batteries can still accept current, so a bank that finishes charging early frees its share for the banks still working. It is a genuinely useful way to use every available amp, but the total available to share still tops out at the charger's published rating.
Should I buy the ProSport HD 20A or the NOCO GENPRO10X3 for a 36 volt bank?
The GENPRO10X3 publishes 10 amps to each of three banks independently, 30 amps total, and includes a selectable lithium mode, both of which beat the ProSport HD 20A's shared 20 amp total on a fully discharged three battery bank. The ProSport HD's real advantage is its published waterproof rating, so the better choice depends on whether recharge speed or mounting location is the bigger concern on a specific boat.
What is the smaller ProSport HD 8A good for instead?
The 8A 2-bank version suits a smaller boat running two batteries rather than three, and its own listing states selectable LiFePO4, flooded, AGM and GEL charge profiles, which the larger 20A 3-bank listing reviewed here does not state. It is also genuinely waterproof at a lower price, making it a reasonable budget pick for a two battery boat that also runs a lithium bank.
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Researched, not professional advice. This page is compiled from published engineering and regulatory figures, manufacturer specifications and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are boating convention rather than published standards, and they are labelled that way wherever they appear. Marine electrical work is not house wiring. Use tinned, finely stranded marine cable, size it for voltage drop and for the ABYC E-11 ampacity table rather than one or the other, and put overcurrent protection within seven inches of the battery positive terminal, because everything between the post and the fuse is unprotected. A lithium battery needs a charger with a lithium profile. Never load a boat past its capacity plate, and remember that canoes and kayaks carry no federal capacity plate at all, so their stated capacity is the manufacturer own figure. Wear the life jacket, and treat early season water as the hazard it is: cold water immersion takes your breath and then your hands long before it takes your core.