Two chargers, opposite ends of the same job. The Battery Tender Junior is the minimalist: 0.75 amps, 12 volts only, four charging steps that end in float, a 12-foot cord, and a single purpose — keep a small battery full while the vehicle sits. The Schumacher SC1359 is the bench tool: 15 amps of rapid charge with a 3-amp maintain mode, automatic 6-volt and 12-volt detection, a built-in battery tester and a desulfation mode. Comparing them on headline amps alone misses the point, because one is bought for storage and the other for recovery. This head-to-head prints both makers’ own figures, flags every conflict, and routes you by the job and the battery size. For the wider field, start with our pillar guide to the best trickle charger.
One limit applies to both, and it is worth stating before any table: neither charger has a lithium mode. Both are lead-acid tools — flooded, AGM and gel in the Junior’s case; standard, AGM, gel and deep-cycle in the Schumacher’s. If any battery you own is lithium, this comparison is the wrong shortlist, and the lithium-capable picks live in the pillar guide and in our trickle chargers archive. Everything below is a lead-acid decision: maintainer or bench charger, storage or recovery.
How we researched this guide
We compared 2 chargers head-to-head, both carried over from this site’s verified research pools: the Battery Tender Junior (Deltran 021-0123, ASIN B000CITK8S) from our pillar and budget pools, checked against Deltran’s product page, specification material and motorcycle battery guide, and the Schumacher SC1359 (ASIN B0789697JT) from our mid-budget pool, checked against its Amazon listing item details and its owner manual as reproduced in that research. The SC1359 is the only Schumacher model verified in any of our pools, so it is the Schumacher in this comparison — no other model was substituted. Every figure traces to one of those pools; where a source conflicts — the SC1359’s weight and warranty — the conflict is printed, not resolved quietly. We do not bench-check chargers, and no prices appear here.
We reviewed owner reports across 5 sources — two RamForum threads, the Tundras.com charger comparison thread, Bogleheads and Deltran’s own rider guide — paraphrased and linked in each owner section. Junior coverage is deep, built on years of Deltran maintainer reporting; SC1359 forum coverage is thin, and its block says so plainly rather than borrowing themes from other Schumacher models.
The 30-second answer
Storing a motorcycle, ATV, UTV or other small battery for weeks or months: buy the Battery Tender Junior — 0.75A, four steps into automatic float, spark-proof, with a 5-year warranty and a cord that reaches the bike where it parks. Recovering flat car, truck or marine batteries, or running a bench that sees them often: buy the Schumacher SC1359 — 15A rapid charge, a 3A maintain mode, a built-in tester and desulfation. A big stored battery sits between them: the finder below routes it to the SC1359’s maintain mode, because Deltran publishes no size ceiling that covers it for the Junior. Lithium battery: buy neither — neither maker lists a lithium mode.
Best for Set-and-Forget Storage
Battery Tender Junior
Best if one small battery sits for months: a 0.75A four-step maintainer that drops to float on its own, senses at least 3 volts before it will output, runs a 12-foot output cord, and carries a 5-year warranty. Nothing to select, nothing to configure.
Best for Fast Recovery and Shop Use
Schumacher SC1359
Best if flat batteries are the problem: a 15A rapid charge with a 3A charge and maintain mode, automatic 6V and 12V detection, a built-in battery tester and a desulfation mode, on a bench unit with a digital display. Recovery first, storage second.
Quick compare: the two chargers at a glance
The makers’ own published facts, side by side. The amp gap is real and is the whole story of this comparison: these chargers were built for different jobs.
| Charger | Charge amps | Voltages | Chemistries | Temp. compensation | Warranty | Check Price |
|---|---|---|---|---|---|---|
| Battery Tender Junior | 0.75A | 12V | Flooded, AGM, gel, sealed MF | No | 5 years | |
| Schumacher SC1359 | 15A rapid / 3A maintain | 6V and 12V (auto) | Standard, AGM, gel, deep-cycle | Not published | 2 years |
Junior or SC1359 finder
Pick the job and enter the battery size in amp-hours (Ah) from the battery label. Routing is honest about what the makers publish: Deltran publishes no Ah ceiling for the Junior, so its branch is capped at 20Ah, the powersports class in Deltran’s own examples; Schumacher publishes no Ah ceiling for the SC1359 either, so its branches route by charge rate and role, never by an invented rating. Neither charger has a lithium mode — lithium owners should use the lithium picks in our pillar guide instead of either charger here.
Battery size decides most of this category, and it is the figure buyers guess wrong most often. Our battery runtime guide shows how amp-hours behave under load, and the battery table further down lists typical sizes by vehicle class if the label on yours is long gone.
How to choose between Battery Tender and Schumacher
Charge amps vs the job — storage needs almost none, recovery needs plenty
A maintainer’s job is to replace what a parked vehicle slowly loses, and that takes very little current: the Junior’s 0.75A is sized for it, and Deltran’s own example has it bringing a half-flat 10Ah motorcycle battery to full in about 6.7 hours. Recovery is the opposite job. A flat car battery on 0.75A is a wait measured in days, which is why the SC1359 leads with 15A rapid charge and settles to a 3A maintain rate. Decide which job you actually have; the amp row then decides the charger.
Maintainer vs bench charger — the format follows the job
The Junior is a fit-and-forget maintainer: small, light at 0.65 lb, clamp or ring-lead connection, a 12-foot output cord, and lights instead of menus. The SC1359 is a bench unit at about 3.3 lb with clamps, a retractable handle, a digital display and push-button controls — built to be carried to a battery, used, and put back on the shelf. Neither format is better in the abstract; a bench charger left in its box maintains nothing, and a maintainer on a flat truck battery recovers nothing in useful time.
Voltages and chemistries — and the shared lithium limit
The Junior is 12V only, for flooded, AGM, gel and sealed maintenance-free lead-acid. The SC1359 detects 6V and 12V automatically and adds deep-cycle to its lead-acid list, which makes it the only one of the two that fits an older 6V system or a marine deep-cycle battery on its maker’s own wording. The shared limit matters more than either list: neither maker lists a lithium mode, so neither charger may be connected to a lithium battery on any profile either of them offers.
Desulfation vs prevention — two answers to the same failure
Sulfation is the main killer of stored lead-acid batteries, and these chargers answer it from opposite directions. Schumacher builds in an automatic desulfation mode: its manual describes the attempt as capped at 10 hours before the charge aborts with a fault code if it has not worked. Deltran builds in no repair mode at all — the Junior’s strategy is prevention, holding storage voltage in float so sulfation does not form in the first place. Prevention suits a battery that starts healthy; an already-neglected battery is the Schumacher’s case to attempt, with no resurrection promised by either maker.
Temperature compensation — neither charger claims the full answer
Lead-acid batteries want a higher charge voltage in the cold and a lower one in heat. The Junior has no temperature compensation — Deltran’s own rider guide steers extreme-climate owners to its larger Plus model for exactly that feature. Schumacher’s documents make no compensation claim at all, so our tables print Not published rather than assuming one. The honest reading: both chargers are at their best in ordinary garage conditions, and a battery stored through severe winters deserves a compensated charger from the pillar guide instead.
Safety behaviour — sense thresholds, timers and protections
The Junior is spark-proof and reverse-polarity protected, runs an 80-hour safety timer, and will not output at all until it senses at least 3 volts from the battery — a protection that also means a truly flat battery is outside its reach. The SC1359 answers with colour-coded non-sparking clamps and reverse hook-up protection, and its manual adds a second abort: maximum maintain current for a continuous 12 hours also ends the charge, which usually points to a load draining the battery or a battery that has failed. Both sets of behaviour are printed in the troubleshooting table below.
Typical battery sizes, and which charger each size points to
Sizing starts from the battery. Powersports figures are Deltran’s own examples from its motorcycle guide; car and marine figures are typical published capacities for each group, linked under Sources & changelog.
| Vehicle class | Typical battery size | Junior (0.75A maintainer) | SC1359 (15A / 3A bench charger) |
|---|---|---|---|
| Motorcycle, ATV, UTV | About 10Ah typical | Its home class — Deltran’s own 10Ah example | Works, but a bench unit is oversized for the job |
| Touring motorcycle | About 18–30Ah | Upper edge of its class; slow from flat, fine from full | Covered easily on the 3A maintain mode |
| Car and sedan (Group 24 class) | About 45–80Ah | Maintenance only in practice; recovery takes days | Its home class for recovery and maintain |
| Marine and RV deep cycle | Group 24 about 75Ah · Group 27 about 95Ah · Group 31 about 120–130Ah | Not its class — no deep-cycle listing, no published ceiling | Deep-cycle is on its maker chemistry list |
| Diesel truck, dual batteries | About 130–150Ah combined | Not its class | Recover one battery of the pair at a time on the bench |
The pattern matters to winch owners: the battery that works hardest is the one that comes home discharged. Sizing help for the battery itself lives in our winch battery guide, working figures are in how many amps a 12V winch draws, and the seasonal routine sits alongside the rest of the kit in our winch maintenance checklist.
Battery Tender vs Schumacher by buying position
| Position | What you get | Example pick from this comparison |
|---|---|---|
| Smallest commitment, one small battery | A dedicated maintainer that lives on the vehicle all season | Battery Tender Junior |
| Fastest recovery on a bench | 15A rapid charge, a tester and desulfation in one unit | Schumacher SC1359 |
| Two-job garage | The Junior left on the bike, the SC1359 free for cars and boats | Both — one of each |
| Larger or lithium needs | Neither charger here is the honest answer | Step up to the pillar guide picks |
No prices appear in this guide by policy; check the live listing on each button. The budget question here is not which charger costs less today — promotions move — but whether you are buying storage, recovery, or one of each. The sibling cuts of the full ranking sit in our guide to the trickle charger under the lower budget line and the trickle charger at the mid-budget line.
Types of trickle charger, compared
| Type | What it is | Pros | Cons | Best for |
|---|---|---|---|---|
| Compact maintainer | Low-output staged charger that ends in float — the Junior’s class | Set-and-forget, long cords, tiny footprint | Recovery is slow to the point of useless on car batteries | Powersports and stored small batteries |
| Bench charger-maintainer | High rapid-charge rate with a low maintain mode — the SC1359’s class | Fast recovery, tester and desulfation in one box | Clamp-only bench format; not a leave-it-connected routine | Shops, farms, flat car and marine batteries |
| Smart multi-mode charger | Selectable chemistry modes, temperature compensation, repair modes | Widest battery coverage incl. lithium on the NOCO class | Menus and modes to choose correctly | Mixed garages — covered in the pillar guide |
| Multi-bank charger | Two or more independent outputs, usually hard-mounted | One unit covers several stored vehicles | A different, permanent-wiring buying decision | Boats and multi-vehicle garages (pillar guide) |
Both chargers in this head-to-head are lead-acid tools; the multi-mode and multi-bank rows are covered with their own picks in our pillar guide to the best trickle charger and in the trickle chargers archive. One warning applies to every type: a maintainer holds a battery at full charge; it does not fix a vehicle that drains one. If a parked truck kills a battery in a week, find the draw first — our guide to whether winches drain batteries walks through the usual suspects.
Detailed reviews
Each charger is judged on its maker’s own published specifications for the exact ASIN linked: charge rates, voltages, chemistries, protections and warranty. Owner sections paraphrase real reports and link them; where coverage is thin, the block says so.
Best for Set-and-Forget Storage: Battery Tender Junior
Maintainer pick
Why the Battery Tender Junior is our pick
The Junior is what a maintainer should be when the battery is small and the vehicle simply sits. Its four-step program — initialization, bulk, absorption, then float — runs with no mode to select and no menu to get wrong, it is spark-proof at the clamps, and its 12-foot output cord reaches a motorcycle or ATV where it actually parks instead of where an outlet happens to be. Deltran backs it with a 5-year warranty, the longer paper in this comparison by a wide margin. It does one job, at 0.75 amps, and owner history says it does that job for years.
Battery Tender Junior key specs
- Part number: Deltran 021-0123
- Charge current: 0.75A (750mA)
- Battery voltages: 12V only
- Chemistries: Flooded, AGM, gel and sealed maintenance-free lead-acid; NO lithium mode
- Battery capacity: Not published by Deltran — its own guide uses a 10Ah motorcycle example; this guide caps its branch at 20Ah
- Program: 4-step: initialization, bulk, absorption, float (storage)
- Repair mode: None — prevention by holding storage voltage is the design
- Temperature compensation: No — Deltran steers extreme-climate riders to the Plus for this feature
- Dead-battery behaviour: Will not output until it senses at least 3 volts from the battery
- Protections: Spark-proof, reverse-polarity protected; 80-hour safety timer
- Cords: 12 ft output cord; 12.3 ft total reach (Deltran)
- Certifications: ETL and CETL, FCC, ICES, CEC, DOE (Deltran product page)
- Weight: 0.65 lb, charger only
- Warranty: 5-year limited
Battery Tender Junior: fits and best for
Motorcycles, ATVs, UTVs, mowers and seasonal small batteries up to the 20Ah class of Deltran’s own examples — the vehicles in our ATV winch and plowing coverage, stored cars that start the season already full, and any small battery whose owner wants one connection made in autumn and removed in spring. Fit the ring lead once and the routine is seconds; our UTV winch guide covers the battery sizes in that class.
Battery Tender Junior pros and watch-outs
- Simplest operation here: four automatic steps, no modes to select
- Longest warranty in this comparison: 5 years
- 12-foot output cord reaches the vehicle where it parks
- Spark-proof with an 80-hour safety timer and a 3-volt sense floor
- Featherweight 0.65 lb — it lives on the vehicle, not the bench
- 0.75A cannot recover a flat car battery in useful time
- No lithium mode and no repair or desulfation mode
- No temperature compensation for severe-climate storage
- 12V only, and Deltran publishes no Ah ceiling to size it by
Battery Tender Junior: what owners report
On RamForum’s long Battery Tender thread, owners credit Deltran maintainers with exceptional battery life in exactly the Junior’s habitat: sled and motorcycle batteries lasting whole ownerships, season after season on maintainers, and one factory Corvette battery reported at 12 years on a Tender.
Deltran’s own 12V motorcycle battery guide describes the connect-in-autumn, disconnect-in-spring pattern as routine for this class of unit — maker copy, printed here as a usage pattern rather than a result. The balance, from Bogleheads, is that owners defend Deltran as a genuine staged maintainer rather than a basic constant-current trickle charger, which is the correct technical description of the Junior too.
Battery Tender Junior: who should not buy
Skip it for car, truck or marine batteries that come back flat, for any battery past its small-battery class, and for lithium — Deltran lists none of those jobs for it. The covered upgrade inside this comparison is the Schumacher SC1359, with the rapid rate, the tester and the deep-cycle listing.
Battery Tender Junior: pair it with
Pair it with the Battery Tender Ring Terminal Harness 081-0069-6 — the fused 18-inch SAE quick-disconnect harness in the Junior’s own family, so the charger plugs in without lifting the seat or opening a panel: Check Price — ring harness.
We may earn a commission at no cost to you. Listing shown for the Battery Tender Junior, ASIN B000CITK8S — confirm model 021-0123 on the listing before ordering.
Tip: Fit the ring harness permanently and route the quick-disconnect somewhere dry and reachable; the install discipline is the same as our winch hook-up guide sets for the rest of the vehicle.
Best for Fast Recovery and Shop Use: Schumacher SC1359
Bench charger pick
Why the Schumacher SC1359 is our pick
The SC1359 earns its place on a different axis from everything Deltran makes: raw recovery speed with diagnostics in the same box. Schumacher rates it at a 15A rapid charge with a 3A charge and maintain mode, automatic detection between 6V and 12V, multi-stage charging with float monitoring once the battery is full, and a built-in battery tester, and it adds an automatic desulfation mode its manual caps at a 10-hour attempt. For a garage or shop that sees flat car, truck and marine batteries regularly, that combination — recover, check, maintain — is the whole case.
Schumacher SC1359 key specs
- Part number: Schumacher SC1359
- Charge current: 15A rapid charge; 3A charge and maintain at 12V
- Output at 6V: 2A DC (owner manual specification section)
- Input: 120V AC, 60Hz, 3.6A (manual specifications)
- Battery voltages: 6V and 12V, automatic voltage detection
- Chemistries: Standard, AGM, gel and deep-cycle lead-acid; NO lithium mode listed by the maker
- Battery capacity: Not published by the maker — sized here by charge rate and shop role, never by an invented Ah rating
- Functions: 4-in-1 per maker copy: battery tester, charger, desulfator, maintainer
- Desulfation: Automatic on detection; manual caps the attempt at 10 hours before abort
- Temperature compensation: Not published — no claim in the maker documents we read
- Display and controls: Digital display, LED indicators, push-button controls; retractable handle
- Protections: Reverse hook-up protection; colour-coded non-sparking clamps
- Dimensions: 3.63 x 10.5 x 7.75 in (manual specifications)
- Weight: About 3.3 lb (retailer spec data; the Amazon weight field is an obvious data error and is not used)
- Certifications: DOE (listing spec data)
- Warranty: 2-year limited per the manual warranty text (Amazon item details print 1 year — conflict flagged)
Schumacher SC1359: fits and best for
Shops, farms and busy garages recovering flat car, truck, SUV and marine batteries; a single deep-cycle battery that needs hours back rather than days; owners who want a tester in the same unit as the charger. It maintains through its 3A mode and float monitoring, but it is a clamp-on bench unit, so a battery that lives on a maintainer for months is the Junior’s shape of job at small sizes and a pillar-guide smart charger’s at large ones. Boats in this size class are the same batteries our electric boat trailer winch guide works around.
Schumacher SC1359 pros and watch-outs
- Fastest recovery here: 15A rapid charge, twenty times the Junior’s rate
- Built-in battery tester and automatic desulfation in the same unit
- Automatic 6V and 12V detection, including deep-cycle lead-acid
- Digital display and push-button controls suit bench work
- Float monitoring maintains a full battery after recovery
- No lithium mode, and no temperature-compensation claim in maker documents
- Maker publishes no Ah ceiling, so sizing guidance is by role, not rating
- Warranty evidence conflicts: 2 years in the manual text, 1 year in listing details
- Clamp-only bench format — no permanent ring-lead routine in the box
- Heavier at about 3.3 lb; it travels to the battery, it does not live on it
Schumacher SC1359: what owners report
Owner-forum coverage of the SC1359 specifically is thin, and we say so plainly rather than borrowing themes from other Schumacher models: the truck forums behind the Junior’s block discuss Deltran, NOCO and CTEK units at depth, and no comparable Schumacher thread pool surfaced in this research. The deepest model-specific pool is the listing’s own owner reviews, which skew to cars, trucks and marine batteries recovered on a bench — the exact duty its 15A rating is sized for; read them on the SC1359 Amazon owner listing.
The wider owner context, from Tundras.com’s charger comparison thread, is a caution that cuts both ways in this head-to-head: several owners report moving away from Battery Tender units after failures, while others in the same thread run their maintainers around the clock for years — brand loyalty in this category is earned per unit, which is why the finder above routes by job and size, not by badge.
Schumacher SC1359: who should not buy
Skip it for lithium batteries, for a small powersports battery that needs a season-long connection, and for storage in unheated severe-winter spaces, where its maker makes no compensation claim. The covered alternative inside this comparison is the Battery Tender Junior for the storage job, inside its class.
Schumacher SC1359: pair it with
Pair it with the Battery Tender Junior — not an accessory, but the honest pairing for a two-job garage: leave the Junior connected to the stored motorcycle or ATV full-time, and keep the SC1359 free for bench recovery work instead of tying it up as a maintainer: Check Price — Battery Tender Junior.
We may earn a commission at no cost to you. Listing shown for the Schumacher SC1359, ASIN B0789697JT — confirm part SC1359 on the listing; Schumacher sells other bench chargers under other model numbers.
Tip: Use the 3A mode, not the 15A rapid rate, for small batteries, and let the built-in tester speak before a long charge, not after; our AC power guide covers the related bench-power basics.
Spec comparison
Every figure is the maker’s published figure for the exact ASIN here. Where a maker publishes nothing, the cell says so; where sources conflict, the conflict is printed in the cell.
| Spec | Battery Tender Junior | Schumacher SC1359 |
|---|---|---|
| Part number | Deltran 021-0123 | SC1359 |
| Charge current | 0.75A | 15A rapid / 3A maintain (12V); 2A at 6V |
| Battery voltages | 12V only | 6V and 12V, automatic detection |
| Chemistries | Flooded, AGM, gel, sealed MF | Standard, AGM, gel, deep-cycle |
| Lithium mode | No | No |
| Maker battery range | Not published | Not published |
| Program | 4-step, ends in float | Multi-stage, float monitoring |
| Repair / desulfation | None (prevention design) | Yes — desulfation, 10-hour cap (manual) |
| Battery tester | No | Yes — built in (maker copy) |
| Temperature compensation | No | Not published |
| Protections | Spark-proof, reverse polarity, 80-hour timer, 3V sense floor | Reverse hook-up protection, non-sparking clamps |
| Format | Maintainer, 12 ft output cord | Bench unit, digital display, retractable handle |
| Weight | 0.65 lb | About 3.3 lb (retailer spec data; listing weight field is in error) |
| Warranty | 5 years | 2 years (manual text; listing details print 1 year) |
| Check Price | Check Price | Check Price |
No score row is printed for this comparison: with jobs this different, a single number would pretend the 0.75A maintainer and the 15A bench charger were ranked on the same scale. The finder above is the ranking tool — it routes by the job and the battery in front of you, which is the honest version of a score.
Connection and installation basics
The two chargers connect in opposite routines. The Junior is made to be fitted once and left: bolt its ring lead or an SAE harness to the battery, route the quick-disconnect somewhere reachable and dry, and from then on connecting for storage is a ten-second job with the hood or seat left closed. Keep the lead clear of belts, fans and exhaust parts, keep the fuse accessible, and remember its protection logic — it will not output until it senses at least 3 volts, so a battery flatter than that needs recovering on a charger that will start lower before the Junior can maintain it.
The SC1359 is made to be carried: clamps on, red to positive and black to a ground away from the battery where the vehicle maker allows it, charger plugged into the wall last, mode selected, and the display watched for the first minutes. Its non-sparking clamps and reverse hook-up protection forgive a hurried connection, not a careless one. When the charge finishes it monitors on float, but the honest routine is to return it to the shelf and let a maintainer own the months between uses. The terminal discipline is the same as the rest of the vehicle’s heavy wiring: our winch-to-battery wiring guide, essential winching accessories and the accessories hub cover that work.
Safety essentials
Six rules that outrank either charger in this comparison:
- Work with the charger unplugged while you make or break battery connections, and connect the charger to mains power last.
- Connect positive first and negative last; on the vehicle, put the negative on a chassis ground away from the battery where the maker allows it.
- Never charge a frozen, cracked, leaking or swollen battery, and never run a desulfation attempt on a battery showing those signs.
- Keep sparks, flames and smoking away from a charging battery — charging lead-acid batteries vents hydrogen gas.
- Never connect either charger here to a lithium battery: neither maker lists a lithium mode, on any profile either charger offers.
- Route and secure every lead clear of belts, fans, steering and exhaust parts, and check a permanent install monthly.
Three companions from this site’s verified pool pair with these chargers; the lithium item is a safety alternative, not an accessory for either pick:
Battery Tender Ring Terminal Harness 081-0069-6 — the fused SAE harness that makes the Junior’s fit-once routine possible.
Check Price — Battery Tender ring harness
NOCO GENIUS1 maintainer — the lithium answer neither charger here can give: a 1A maintainer with a lithium mode for LiFePO4 batteries with a management system, maker-rated to 30Ah. If the battery is lithium, this class of charger is the safe purchase, not either pick above.
NOCO GC002 X-Connect M6 eyelet terminal — the fused permanent lead that pairs with that GENIUS1, so a lithium powersports battery gets the same fit-once routine.
Check Price — NOCO GC002 eyelet terminal
General battery-handling rules also sit in our maintenance checklist and winch cover guide makes the same weather point for the rest of the kit.
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Junior shows no output at all | Battery under its 3-volt sense floor, so the charger will not start by design | Recover the battery first on a charger that starts lower (the SC1359 on the bench), then maintain it with the Junior |
| Junior stops before the battery seems full | Its 80-hour safety timer ended the cycle | Disconnect, reconnect to restart the program, and have the battery checked if it happens again — a healthy small battery finishes well inside the timer |
| SC1359 aborts desulfation with a fault code | The manual’s own path: the 10-hour desulfation attempt ended without success | Have the battery checked and expect replacement; do not loop the desulfation cycle hoping for a different answer |
| SC1359 aborts during maintain | Maximum maintain current ran for a continuous 12 hours (manual behaviour) — a load draining the battery, or a failed battery | Remove any loads, then have the battery checked; find the draw before blaming the charger |
| Lights flag a reversed connection | Polarity reversed at the battery — both chargers protect against exactly this | Unplug, remove both clamps, confirm positive to positive, reconnect positive first |
| Float light on, battery weak a week later | The battery accepted a surface charge but cannot hold capacity — age or a failing cell | Have the battery load-checked; if it passes, hunt the vehicle’s parasitic draw instead |
Who should NOT buy these
Your battery is lithium. Neither maker lists a lithium mode for either charger, and no lead-acid or desulfation profile may be used on a lithium battery. The lithium-capable picks are in our pillar guide to the best trickle charger, and the GENIUS1 in the safety section above is the small-battery version.
Your vehicle kills batteries from a fault, not from sitting. A parasitic draw, a failing alternator or a dying battery defeats both chargers at any amp rating. Diagnose first — start with why batteries drain — then maintain the fixed vehicle.
You need a battery started today. These are chargers and maintainers, not jump starters — even the SC1359’s 15A is a charge rate that works in hours, not a cranking output that works in seconds. Keep a jump pack for emergencies and a maintainer for prevention; they are different tools.
Your storage is off-grid, or your winters are severe and unheated. Both chargers need mains power, the Junior has no temperature compensation and the Schumacher’s maker claims none. A compensated smart charger from the pillar guide, or a solar maintainer for the off-grid case, is the honest route — both live in the trickle chargers archive.
You run a fleet or a multi-bank garage. One clamp-on bench unit and one small maintainer are not a fleet system. Multi-bank chargers exist for that job and are covered, with their own picks, in the pillar guide.
Final verdict
Best for set-and-forget storage — Battery Tender Junior: the 0.75A, four-step, 5-year-warranty maintainer for small batteries that sit. Check its price.
Best for fast recovery and shop use — Schumacher SC1359: 15A rapid charge, a built-in tester and desulfation for flat car, truck and marine batteries. Check its price.
Lithium, multi-bank or severe-winter needs: step up to the wider picks in our pillar guide to the best trickle charger rather than stretching either charger past what its maker claims.
FAQ
Battery Tender Junior vs Schumacher SC1359: which is better?
Better depends on the job, because these chargers barely overlap. The Junior is a 0.75A dedicated maintainer for small batteries in storage: automatic float, a long cord, a 5-year warranty. The SC1359 is a 15A bench charger for recovering flat car, truck and marine batteries, with a tester and desulfation built in. Storing a bike points to the Junior; a flat truck battery points to the Schumacher; a two-job garage honestly uses one of each.
Can the Battery Tender Junior charge a car battery?
Electrically it will maintain a full car battery, and Deltran publishes no Ah ceiling that forbids the connection — but at 0.75A, recovering a flat car battery takes days, and Deltran’s own examples for the Junior are motorcycle-class batteries. Our finder therefore caps its branch at 20Ah and routes car batteries to the SC1359. Treat the Junior on a car as a maintainer for a battery that starts full, never as the recovery plan.
How long does the Junior take to charge a motorcycle battery?
Deltran’s own guide gives the honest maker figure: a 10Ah motorcycle battery from half charge to full in about 6.7 hours on this class of unit. A fully flat small battery takes proportionally longer, and the Junior will not even start on a battery under 3 volts, because its sense floor is a protection. From normal storage discharge — its real job — it simply holds the battery at float indefinitely.
Is the Schumacher SC1359 a battery maintainer or just a charger?
Both, on its maker’s wording: a 15A rapid charge and a 3A charge and maintain mode, with float mode monitoring once the battery is full. The honest distinction is format, not electronics — it is a clamp-on bench unit, so it maintains while it is connected and attended in a way the Junior, fitted once and left for a season, is designed not to need. For months-long storage, the maintainer format is the better tool.
Can either charger desulfate a battery?
Only the Schumacher attempts it: its automatic desulfation mode runs on detection, and its manual caps the attempt at 10 hours before aborting with a fault code. The Junior has no repair mode — Deltran’s answer is prevention, holding storage voltage so sulfation does not form. Neither approach fixes a shorted cell or a cracked case; if the Schumacher flags the battery after an attempt, believe it.
Which charger works on a 6-volt battery?
Only the SC1359. Schumacher lists automatic 6V and 12V detection, with a 2A output at 6V in its manual specifications. The Junior is 12V only — this exact model, the 021-0123. Owners of older 6V systems should also note the Junior’s bigger Deltran siblings are separate models; the listing linked here is the 12V unit.
Can I use either charger on a lithium battery?
No. Neither maker lists a lithium mode for either charger — the Junior covers flooded, AGM, gel and sealed maintenance-free lead-acid, and the SC1359 covers standard, AGM, gel and deep-cycle lead-acid. Charging lithium on a lead-acid profile is a safety issue, not a performance one. Lithium owners need a charger with a dedicated lithium mode, restricted by its maker to LiFePO4 batteries with a management system; those picks are in the pillar guide.
Which has the better warranty?
The Junior, on both length and evidence: Deltran’s 5-year limited warranty is printed consistently for the 021-0123. The SC1359’s evidence conflicts — its manual warranty text prints two years while the Amazon item details print one — so we print 2 years, manual governing, and flag the conflict wherever the figure appears. A longer, cleaner warranty is a real point in the Junior’s favour for a unit bought to be left connected for years.
Why does the Junior refuse to charge a completely flat battery?
By design: Deltran’s manual behaviour is that the Junior will not output until it senses at least 3 volts from the battery, which protects it against being connected to a short or a non-battery load. The practical consequence is a two-step routine for a truly flat small battery — recover it first on a charger that starts lower, the SC1359 being the one in this comparison, then hand it to the Junior for storage.
Sources & changelog
Manufacturer and listing sources: Deltran Battery Tender Junior page · Deltran 12V motorcycle battery guide · Schumacher SC1359 listing, item details and manual warranty text · Battery Tender Junior listing and item details · Battery Tender ring terminal harness 081-0069-6 listing · NOCO GC002 eyelet terminal listing · NOCO GENIUS1 listing and item details.
Owner and reference sources: RamForum Battery Tender thread · RamForum charger thread · Tundras.com charger comparison thread · Bogleheads car battery thread · F150Forum installation thread · BatteryEquivalents Group 24 data · RV Forum group-size amp-hour chart.
Changelog — October 16, 2026: guide first published.
By Leo, Founder, WinchInsider
Leo writes WinchInsider’s buying guides from maker documentation and owner reporting — no bench claims, no borrowed ratings. Battery care sits next to winching on every truck he covers, because the winch only works as well as the battery behind it. More at About WinchInsider.
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