Best Power FERRUPS Replacement Batteries

About Best Power FERRUPS Replacement Batteries

Replacement batteries for Best Power FERRUPS UPS systems

The Best Power FERRUPS line is a family of ferroresonant uninterruptible power supplies ranging from roughly 500 VA up to 18 kVA. A FERRUPS unit depends on a string of sealed lead-acid (SLA/VRLA) batteries to carry the load during an outage. Those batteries wear out and are the single most common reason a FERRUPS drops the load or throws a battery fault. The batteries in this collection are compatible replacements matched to specific FERRUPS models.

Battery type and how capacity scales

Every cell used across the FERRUPS range is a 12 volt sealed lead-acid battery. What changes from model to model is the amp-hour (Ah) capacity and the number of batteries wired in series to reach the pack voltage your unit needs. Smaller FERRUPS units typically use 12V 18Ah batteries; mid-range units use 12V 35Ah; and the larger frames use 12V 75Ah. Because capacity varies by model, we do not quote a single number for the whole series — the exact voltage and Ah for your unit are shown on each product page in the grid below.

Identify your battery by exact model

FERRUPS model numbers are specific, and a battery that fits an FE-2.1K will not necessarily fit an FES-1.8K or an FER-3.1K. Find the model label on the front or rear of your UPS (for example FE-700, FES-850, 0800-3K, FE-4.3K, FER-1.8K, or FE-18K) and match it to the product titled for that exact model. Confirm by model first; the product grid then shows the per-battery voltage and Ah so you can verify before you order.

Genuine OEM vs. aftermarket

Best Power and FERRUPS are trademarks of Eaton Corporation. You can buy factory battery kits through Eaton, or you can fit aftermarket SLA batteries of the same voltage, capacity, and terminal type. Quality aftermarket batteries use the same C&D, CSB, or equivalent SLA chemistry as the originals and are a compatible, lower-cost replacement. The batteries sold here are aftermarket replacements, not Eaton-branded OEM kits.

Battery lifespan

Sealed lead-acid UPS batteries typically last 3 to 5 years in service. Heat is the main enemy: as a rule of thumb, battery life is roughly halved for every 8 °C (about 15 °F) of sustained operating temperature above 25 °C (77 °F). A FERRUPS kept in a hot closet or a warm equipment room will need batteries sooner than one in a climate-controlled space. Plan to test under load annually and replace proactively rather than waiting for a failed self-test.

How to replace the batteries

General steps for a FERRUPS battery swap:

1. Confirm the exact UPS model and order the matching battery set.
2. Check whether your FERRUPS model and your site procedure support live battery replacement — many FERRUPS frames offer a maintenance bypass or are rated for battery service while supporting the load, but this varies by model and configuration. If your unit and procedure do not explicitly support a live swap, shut the UPS down and isolate it before disconnecting any battery. Consult the manual for your specific FERRUPS model before working on the battery string.
3. Note the wiring and polarity of the existing string before disconnecting anything.
4. Remove the old batteries, install the new set in the same series/parallel arrangement, and reconnect observing correct polarity.
5. Run the UPS self-test and a brief load test to confirm the new pack holds runtime.
6. Recycle the old SLA batteries through a proper lead-acid recycling channel.

FAQ

How do I know which battery my FERRUPS needs?
Match by the exact model number printed on your unit, then confirm the per-battery voltage and Ah on the product page.

Are these the same as Eaton OEM batteries?
They are compatible aftermarket SLA batteries of the same voltage and capacity, not Eaton-branded kits.

How often should I replace them?
Typically every 3 to 5 years, sooner if the UPS runs in a warm environment.

Can I replace just one weak battery?
Replace the whole string at once. Mixing old and new SLA batteries shortens the life of the new ones and can cause uneven charging.

Do you ship to Canada?
Yes. Orders ship from our Canadian warehouse.

Best Power®, FERRUPS®, and Powerware® are trademarks of Eaton Corporation. UPSPLUSBATTERY.ca is not affiliated with, endorsed by, or authorized by the manufacturer; aftermarket batteries are compatible replacements.