Custom Battery Packs, Built to Your Specifications

The pack your machine needs isn't made anymore. Or there was never an off-the-shelf version of it to begin with.

That's the work we take on. We design and assemble custom battery packs to your specification, one at a time or by the run. Send us the dead pack, a drawing, or just the requirements, and we'll build one that fits.

Get a quote on your custom pack  |  440-942-2555

What "Custom" Actually Covers

  • Voltage

    Cell count set to whatever the equipment calls for.

  • Capacity

    Match the original rating, or go higher when the cells and the space allow it.

  • Shape and Footprint

    Stick packs, side-by-side, L-shape, split packs with a harness running between halves.

  • Chemistry

    NiCd, NiMH, or lithium-ion, chosen for the duty cycle rather than the trend.

  • Leads and Connectors

    Reuse your existing connector, splice to a new one, or terminate to a spec you supply.

  • Housing

    Shrink-wrapped, fitted into the original case, or built to a hard shell you provide.

Chemistries We Build

Nickel-cadmium (NiCd). Still the right call for high-drain tools, emergency lighting, and anything that lives on a float charge. NiCd takes abuse and deep discharge better than most of what would replace it.

Nickel-metal hydride (NiMH). More runtime per cell than NiCd in the same footprint, and no cadmium to dispose of. Good for medical carts, survey instruments, and handheld equipment where the extra capacity earns its keep.

Lithium-ion. Where weight and runtime matter most. We build custom lithium battery packs from 18650 and 21700 cells, with the battery management system matched to the pack: cell balancing, over-discharge and overcurrent protection, and the charge profile the equipment expects. A custom 18650 battery pack is one of the most common builds that comes through the shop, usually replacing a nickel pack in equipment that has outlived its original power source.

If lithium is wrong for your application, we'll tell you instead of building it. Some equipment can't charge it correctly and some low-voltage cutoffs will run a lithium pack into damage. We can build you the pack you asked for, but we can't do it in good conscience if we already know how it ends.

Tell us how the equipment gets used and how it gets charged, and those two answers usually settle the chemistry on their own.

How a Custom Battery Pack Assembly Comes Together

  • 1. Spec review

    We go over the requirements with you: voltage, runtime, physical constraints, connector, charger, how the equipment actually gets used. If you still have the old pack, send it. It answers half the questions by itself.

  • 2. Cell selection

    We pick cells that fit the space and the load. This is where capacity upgrades happen. High-capacity Sub-C cells at 3300mAh will often drop straight into a footprint that originally held something much smaller.

  • 3. Spot-welded assembly

    Every pack gets spot welded in-house on our own equipment. Our lead rebuilder has been on this bench 12 years, and the man who trains our rebuilders has been here about 30. Welded tabs, not solder on cell terminals. Soldering puts more heat into a cell than a cell should ever see, and it shows up months later as a pack that dies early.

  • 4. Load testing

    Packs get tested under load before they leave. Checking voltage proves nothing. A pack can read 12V and collapse at 5 amps, and you'd never know until the machine quit on you.

  • 5. Warranty

    Custom builds carry a six-month workmanship warranty. If something we did causes the failure, we make it right.

Most builds run about a week once the spec is settled. Complex assemblies, or cells we have to bring in specially, run longer. We'll tell you which one yours is before you commit.

Why the Packs Hold Up

  • 36 Years, One Location

    Bulldog has worked DC power out of the same Willoughby shop since the beginning.

  • Built and Tested Here

    Every pack is spot welded, load tested, and inspected in-house before it ships.

  • DC Power Is All We Do

    The difference between a shop that assembles a pack and one that knows what your application will do to it.

  • We Know Who Built It

    If a pack comes back, we can trace exactly who built it and what went into it.

What We Get Asked to Build

  • Replacements for OEM packs the manufacturer discontinued or orphaned
  • Medical and EMS equipment: monitors, pumps, powered cots, transport gear
  • Industrial and shop equipment still running long after its power source stopped being made
  • Robotics, test fixtures, and one-off prototypes
  • Capacity upgrades where the original pack was undersized for how the machine actually gets used
  • Small production runs for equipment builders who can't source what they need

Obsolete is normal here.

One Pack or a Hundred

There's no minimum. If you need exactly one custom battery pack for one machine, that's a job we'll take, and it's most of what comes through the door. Per-unit pricing does come down on repeat orders and small runs, so say so when you request a quote and we'll price it that way.

This is where a shop like ours fits better than a large custom battery pack manufacturer. Most of them want a purchase order for several hundred units before anyone will start a drawing. We'll build you one.

Start your quote

Battery Pack Assembly and Rebuilding

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Already Have a Pack That Just Needs New Cells?

If your existing pack is structurally sound and the cells are simply worn out, re-celling is usually the cheaper path. See our Battery Rebuilding service for pricing and turnaround on rebuilds.

Built and Tested in Willoughby, Ohio

Every pack gets assembled and tested at our shop on Vine Street. Customers across Lake County, from Mentor and Eastlake out to Painesville, plus the east side of Cleveland, drop equipment off and pick it up. Everyone else ships packs in and we ship them back.

Nickel packs go out standard ground. Lithium packs ship under DOT rules, which we handle on our end, and it changes nothing you have to do.

Custom Battery Pack FAQ

Can you build a pack that's no longer made?

Usually. Discontinued and obsolete packs are a large share of the custom work we do. Send us the old pack, even a dead one, and we can generally work back to the cell count, capacity, and connector from it. A photo of the label plus the equipment model number gets us close if the pack is long gone.

What's the minimum order?

One. Single packs and prototypes are welcome. Per-unit pricing improves on repeat orders and small runs, so mention it if you'll need more than one.

How long does a custom pack take?

About a week for most builds once the spec is agreed on. Assemblies needing cells we don't stock, or unusual housings, run longer. You'll get a timeline with the quote.

Can you build a pack with more capacity than the original?

Often. Cell technology has moved a long way, and a footprint that held 1800mAh cells twenty years ago will frequently take 3300mAh cells today. Whether that's a good idea depends on your charger. A higher-capacity pack needs a charger that can actually fill it, so we check that before recommending it.

Can you convert my nickel pack to lithium?

Sometimes, and it's worth asking. A custom lithium ion battery pack can cut real weight and add runtime. But the charger and the equipment's low-voltage cutoff both have to be compatible, and if they aren't, we'll say so rather than build you something that disappoints in six months.

Do you ship battery packs?

Yes. Nickel packs ship standard ground. Lithium packs ship under DOT hazardous-materials rules, which we take care of on our side. Ship your old pack in and we'll ship the new one back.

Do you do custom chargers too?

Tell us what the pack needs and we'll get you to the right charger. Getting the chemistry right and then charging it wrong is one of the most common ways a good pack dies young, and it's the easiest thing on this page to get wrong on your own. Call before you buy one.

Get a Quote on Your Custom Pack

Tell us what the equipment is, what the original pack was rated at, and what it has to do. A photo of the old pack's label covers most of it.

Call 440-942-2555 or 800-721-1119, or use the form below. We'll come back with a spec and a price, and we'll get you taken care of.

Request a Quote