Quick answer: A replacement 12V block fits the extended run time battery cabinet you already own only if six things check out: footprint, height over terminals, terminal type and hardware, connector reach, string weight and floor loading, and string count. The number that stops most orders is height over terminals, not case height, because the bolt, washer and connector sit above the case lid. The current blocks are S12V325FL, S12V370FL and S12V539FL, now sold under the Stryten Energy E-Series AGM label as AGM325, AGM370 and AGM539.
Key points
- Measure the vertical clearance of the shelf, then compare it against height over terminals. Case height leaves out the bolt, the washer and the connector bar, which is where the interference actually happens.
- The current blocks differ in case dimensions, terminal design and weight from the blocks they replace, so fit is confirmed before ordering rather than assumed.
- A current block is often smaller and lighter than the legacy block it succeeds. That creates slack in the shelf position rather than interference, and slack still has to be restrained.
- Terminals on the current line are threaded inserts: T6 on the AGM325 and AGM370, T8 on the AGM539, both taking a 6 mm bolt at 71 in-lb. A matching bolt size does not confirm a lug match.
- To preserve the runtime the cabinet was built to deliver, match watts per cell at the required duration and end voltage. Amp hours compared across generations will mislead you.
- Weigh the string, not the block. Block weight multiplied by the block count is what the cabinet and the floor have to carry.
- CPBS supplies the batteries. The cabinet, rack, breakers and UPS equipment itself stay with the facility and its integrator.
Current 12V blocks: specifications and quote
Full specifications, drawings, manuals and warranty documents for each current model.
Legacy blocks S12V300F, S12V370F, S12V370NGF and S12V550NGF are succeeded by these models. Case dimensions, terminal design and weight differ, so fit is confirmed before ordering.
An extended run time battery cabinet is doing one job: holding enough stored energy beside the UPS to carry the load for longer than the internal battery tray can manage. It does that with more blocks, larger blocks, or both. When those blocks reach end of life, the question that stops the purchase order is rarely which model to buy. It is whether the model you have been quoted will physically go into the cabinet that is already bolted to the floor.
This guide answers that question. It is written for facility and critical power managers, UPS service technicians, telecom and utility power engineers, oil and gas SCADA technicians, and the procurement staff who have to defend the order. Most of the people asking are holding a GNB Sprinter or Sprinter NEXT block with an S12V part number on the label.
Critical Power Battery Solutions (CPBS) is the battery division of Advanced Technical Services Inc., founded in 1981 and ISO 9001 certified, and is an authorized Stryten Energy reseller. Tom Kierna, who has more than 40 years in industrial batteries including 15 across GNB and Stryten, sizes every order personally. CPBS supplies batteries. Supplying, selecting, or quoting the cabinet, rack, breakers, or UPS equipment itself is outside the scope of what CPBS does.
Who this fitment guide is for
This guide is for anyone who already owns the enclosure and needs the 12V VRLA block string inside it replaced. The cabinet or open rack is installed, the UPS beside it is staying, and the blocks are due. Nothing here is about specifying a new cabinet or a new UPS.
- Facility and critical power managers signing off a replacement string on an installed extended run time cabinet.
- UPS service technicians confirming that quoted blocks will land on the existing shelves and connector bars.
- Telecom and utility power engineers holding a string that has passed its service window.
- Oil and gas SCADA technicians replacing blocks in unconditioned or remote enclosures.
- Procurement staff who need the order to be defensible on paper before it is placed.
If the enclosure in question sits in a raised floor computer room rather than a plant room, the application background is covered separately in the data center battery replacement guide. The fitment checks below apply either way.
The block in the cabinet and the block you will order carry two different labels
The Sprinter NEXT line is now sold as the Stryten Energy E-Series AGM line: same battery, same part number on the block, new label. AGM325 is S12V325FL. AGM370 is S12V370FL. AGM539 is S12V539FL. This is a label progression, not an acquisition, a merger, or a redesign of the product.
The full naming chain runs Exide Sprinter, then GNB Sprinter NEXT, then Stryten Energy E-Series AGM. This guide leads with Sprinter and the S12V part number because that is what is printed on the block sitting in the cabinet. The E-Series AGM name is given once so that you can match a current listing without wondering whether you are looking at a different product.
Two questions come before fitment and are answered elsewhere. If you need to know which legacy block corresponds to which current block, that mapping lives in the Sprinter cross reference and replacement guide. If the label is in front of you and you need to know what the characters mean, the breakdown is in the guide to reading a Sprinter NEXT part number. This guide picks up after both of those, at the point where you know what to order and need to know whether it will go in.
Current 12V block dimensions
These are the published dimensions for the three current blocks, and the last two columns are the ones that decide fitment. Height over terminals and weight are what the shelf and the floor actually experience.
| Model | Length in | Width in | Height in | Height over terminals in | Weight lbs | Terminal |
|---|---|---|---|---|---|---|
| S12V325FL (AGM325) | 10.24 | 6.61 | 8.19 | 8.31 | 52.9 | T6 |
| S12V370FL (AGM370) | 12.05 | 6.61 | 8.15 | 8.27 | 61.7 | T6 |
| S12V539FL (AGM539) | 13.19 | 6.77 | 10.83 | 10.95 | 93.5 | T8 |
The number that matters for shelf clearance is height over terminals, not case height, because the bolt, washer and connector sit above the case. Measure the vertical clearance of the shelf the block sits on, not the block.
Why case height is the wrong number to measure against
Case height stops at the lid. The block does not. Above the lid sits the terminal itself, then the bolt and washer that clamp the connector, then the connector bar or cable lug that carries current to the next block. That stack is what meets the underside of the shelf above.
On the current line the published difference between case height and height over terminals is 0.12 inches on all three blocks: 8.19 to 8.31 on the AGM325, 8.15 to 8.27 on the AGM370, and 10.83 to 10.95 on the AGM539. That figure is the terminal and its landing, and it is measured before any hardware is fitted. The bolt head, the washer and the connector bar sit on top of it, and their combined height depends on the hardware in your installation rather than on the battery.
The practical consequence is that a shelf which measures a comfortable clearance against a published case height can turn out to be tight or unusable once the string is assembled. Measure shelf to shelf clearance in the cabinet, subtract the height over terminals figure, and confirm what is left is enough for the connector, the bolt head and a hand with a torque wrench in it.
The six fit checks
Six checks between a quote and a purchase order will tell you whether the block fits. They are ordered so that the ones that stop an order outright come first.
- Footprint. Compare block length and width against shelf depth and the per position width in the existing cabinet. A current block can be shorter and narrower than the legacy block it replaces, which creates slack rather than interference. Slack is easier to solve than interference, but it still has to be restrained so that the block cannot shift on the shelf.
- Height over terminals. Use height over terminals, not case height. Confirm against shelf to shelf clearance with the connector and bolt installed, not with the bare block on the shelf.
- Terminal type and hardware. The current blocks use a threaded insert in tin plated copper alloy: T6 on the AGM325 and the AGM370, T8 on the AGM539, both taking a 6 mm bolt torqued to 71 in-lb. Legacy Exide era blocks listed on the older selection guide use an Insert M6 terminal. A similar bolt size does not confirm that the hardware or the cable lug will match. Confirm terminal type, terminal height, and lug fit as three separate items.
- Connector reach and post spacing. If block length or terminal position changes, the inter unit connector bars already in the cabinet may no longer land on both posts. Connector length is fixed hardware and cannot be stretched. Confirm post to post spacing on the actual installation before ordering, and budget for new connectors if the spacing moves.
- String weight and floor loading. Multiply block weight by the number of blocks in the string. Confirm that the cabinet or rack and the floor beneath it support that total plus any auxiliary equipment mounted in the same enclosure. Where seismic conditions are anticipated, floor anchoring is the responsibility of the user.
- String count and paralleling. Confirm how many blocks run in series and how many strings run in parallel. Stryten Energy recommends a maximum of four parallel strings in high rate applications, where high rate means a load that would discharge the battery in 60 minutes or less. Cable connections from the bus or the load to each parallel string are preferred over paralleling the strings to each other.
Five of the six are measurements you can take with a tape and a torque wrench in an afternoon. The sixth is a question for whoever commissioned the system. None of them require the battery to be on site first, which is the point: every one of these is answerable before the order is placed.
Extended run time: what actually changes when you replace the string
An extended run time cabinet holds more blocks or larger blocks so that the load stays up longer, and that runtime is only preserved if the new blocks carry the same watts per cell at the same duration and the same end voltage. Watts per cell at a stated duration is the number to match. Amp hours is not.
The reason is the load. A UPS presents a roughly constant power draw, so as battery voltage falls through the discharge the current rises to hold that power. An amp hour figure quoted at a long rate does not describe what happens on a 15 minute or 30 minute UPS duty cycle. Constant power at a stated duration and end voltage does.
| Model | 5 min | 10 min | 15 min | 30 min | 60 min | 90 min |
|---|---|---|---|---|---|---|
| S12V325FL | 441.8 | 325.1 | 290.0 | 182.2 | 107.2 | 80.0 |
| S12V370FL | 499.6 | 401.3 | 330.8 | 206.7 | 121.6 | 90.5 |
| S12V539FL | 710.1 | 530.7 | 458.9 | 312.2 | 190.2 | 142.9 |
Constant power discharge, watts per cell at 25 degrees C, to a 1.75 volts per cell end voltage. Read the column that matches the backup duration you need and the end voltage the system is actually set to, then compare that against the load per cell. Do not compare amp hour ratings between generations.
Working out the load per cell from the UPS rating and the string configuration is the sizing step, and it is covered in full in the VRLA battery sizing guide. The aging and design margin factors that sit on top of the raw number, and the mistakes that most often undersize a string, are covered in the walkthrough of common IEEE 485 sizing mistakes. If what you want is simply how long a given string will hold a given load, that arithmetic is set out in the guide to calculating battery runtime.
Temperature changes which block actually meets the target
Battery performance falls as temperature falls, so a cabinet in an unconditioned space delivers less than the 25 degrees C table above. That makes room temperature a fitment question and not only a maintenance one, because it changes which block size actually meets the runtime target in that particular room.
Temperature variation across the string matters as much as the average. Keep variations across the string within 3 degrees C (5 degrees F). Heat or cooling directed at one part of a cabinet creates cell voltage differences between blocks that sit in the warm zone and blocks that sit in the cool one, and those differences shorten life across the whole string rather than only in the warm corner. A cabinet positioned against a hot wall, or directly in front of a room air handler, is a common cause.
The correction factors that turn a room temperature into a sizing adjustment belong with the sizing method rather than here. Where the room needs air changes calculated for the hydrogen evolved on charge, that calculation is set out in the guide to battery room ventilation requirements. Where sustained high temperature is the concern rather than sizing, the failure mechanism and the conditions that lead to it are covered in the guide to preventing thermal runaway in VRLA strings.
What a generation change actually looks like on the shelf
One worked example makes the six checks concrete. The S12V300F is a legacy block still widely in service, and the current block that commonly succeeds it is the S12V325FL.
- The legacy S12V300F measures 10.25 by 6.85 by 8.80 inches and weighs 63.0 pounds, on an Insert M6 terminal.
- The current S12V325FL measures 10.24 by 6.61 by 8.19 inches with a height over terminals of 8.31 inches, weighs 52.9 pounds, and lands on a T6 threaded insert.
Read against the six checks, that comparison says four useful things. Length is effectively unchanged, so shelf depth is not the issue. Width drops by roughly a quarter of an inch per block, which across a full shelf leaves slack that needs restraining. Height over terminals at 8.31 inches is still below the 8.80 inch legacy case height, so vertical clearance improves, but only if the connector and bolt stack is measured rather than assumed. And the terminal changes from an Insert M6 to a T6 landing, which is the check most likely to require new lugs even though both take a similar bolt.
The weight change is the one worth doing the arithmetic on. Just over 10 pounds per block sounds minor until it is multiplied by the block count in an extended run time cabinet, where a saving of several hundred pounds across the string can change the floor loading conversation entirely. Multiply the per block delta by your own block count rather than working from a percentage.
Treat this as a fitment check rather than an assumption. Case dimensions, terminal design and weight differ between generations, so fit must be confirmed on the actual installation before ordering.
Test the string you have before you order the string you need
The measurements that confirm fit are worth taking at the same visit as the measurements that confirm condition. One trip to the cabinet with a tape, a torque wrench and an ohmic tester produces everything needed for both the quote and the decision to place it.
Capacity is the definitive answer to whether a string is finished, and the procedure for a discharge test along with what the result means is set out in the UPS battery testing guide. Ohmic readings are the faster proxy between discharge tests, and how to establish a baseline and trend against it is covered in the guide to internal resistance measurement. Take the ohmic baseline on the same device each time and compare a block against its own history rather than against a published figure.
When to act on those readings, and the service window at which a Sprinter or E-Series AGM string is worth planning around rather than testing again, is the subject of a companion guide on replacing these blocks at the four to five year mark.
What to have ready before you call
Every item below shortens the quote, and the first two shorten it the most. A photograph of the label answers more questions than a description of it.
- Model number and quantity, read from the label on an existing block.
- Cabinet or rack make and model, if it is known.
- Shelf to shelf clearance and shelf depth, measured rather than estimated.
- Number of blocks in series and number of parallel strings.
- Required backup duration and the system minimum voltage.
- Ambient temperature of the room the cabinet sits in.
- A photograph of the label and a photograph of one full shelf.
- Existing connector type, if it is visible without disassembly.
How CPBS handles a block string replacement
CPBS supplies the blocks, confirms the fit against your measurements, and documents what was quoted and why. Tom Kierna reviews the model number, the measurements and the photographs personally before anything is quoted.
CPBS is consulting based and does not perform on site installation, commissioning, or maintenance. The installation itself stays with your own technicians or your service contractor, and the cabinet, rack, breakers and UPS equipment stay with the facility and its integrator. What CPBS owns is the battery decision: which block, whether it fits what you already have, and the paperwork that supports the purchase.
Send the model number and the photographs to Tom Kierna at 630-984-9718 or sales@criticalpowerbatterysolutions.com. Most requests are identified the same day. Current line blocks carry an 8 to 10 week domestic lead time, which is worth knowing before the string reaches the point where the decision is being made under pressure.
Frequently asked questions
Will a Sprinter NEXT block fit in my existing battery cabinet?
Only after six things are confirmed: footprint, height over terminals, terminal type and hardware, connector reach, string weight and floor loading, and string count. Sprinter NEXT blocks are now sold as Stryten Energy E-Series AGM blocks under the same S12V part numbers, and they differ in case dimensions, terminal design and weight from earlier generations, so fit is confirmed on the actual installation before ordering. Most cabinets accept the current blocks without modification, but the confirmation is what protects the order.
What is the difference between case height and height over terminals?
Case height measures the block to the top of its lid, while height over terminals measures it to the top of the terminal landing. On the current line the difference is 0.12 inches: 8.19 and 8.31 on the S12V325FL, 8.15 and 8.27 on the S12V370FL, 10.83 and 10.95 on the S12V539FL. Height over terminals is the figure to use for shelf clearance, and even that is before the bolt, washer and connector bar are fitted on top of it.
How do I measure shelf clearance for a UPS battery block?
Measure the vertical distance from the surface the block sits on to the underside of the shelf or structure directly above it, at the position the block will occupy. Take the measurement at the terminal end rather than the middle of the shelf, because that is where the clearance is consumed. Then subtract the height over terminals figure for the block and confirm what remains is enough for the connector, the bolt head and access for a torque wrench.
Do I need new connectors when I replace a 12V block string?
You need new connectors whenever block length or terminal position changes, because connector bars are fixed hardware and cannot be stretched to reach. Terminal type is the other trigger: a move from a legacy Insert M6 terminal to a T6 or T8 threaded insert can require different lugs even though the bolt size is similar. Confirm post to post spacing on the actual installation, and treat connectors as part of the order rather than as something to check after delivery.
What terminal type do the current 12V blocks use?
The current blocks use threaded inserts in tin plated copper alloy: T6 on the AGM325 (S12V325FL) and the AGM370 (S12V370FL), and T8 on the AGM539 (S12V539FL). Both take a 6 mm bolt torqued to 71 in-lb. The T8 is the larger landing of the two, so a ring lug sized for a T6 will not necessarily suit it. Legacy Exide era blocks on the older selection guide use an Insert M6 terminal instead.
How much does a 12V UPS battery block weigh?
The current blocks weigh 52.9 pounds for the S12V325FL, 61.7 pounds for the S12V370FL and 93.5 pounds for the S12V539FL. Legacy blocks are generally heavier than the current blocks that succeed them: the S12V300F, for example, weighs 63.0 pounds against 52.9 pounds for the S12V325FL. Handling is a two person job on the larger blocks, and the weight that matters for the cabinet is the block figure multiplied by the block count.
How do I know if my floor can support the battery string?
Multiply block weight by the number of blocks in the string, add the weight of the cabinet or rack and any auxiliary equipment mounted in it, then confirm that total against the floor loading the structure is rated for. On a raised floor or an upper storey that confirmation belongs with a structural engineer rather than with the battery supplier. Where seismic conditions are anticipated, floor anchoring is the responsibility of the user.
Do I have to replace the whole string or can I replace some blocks?
Replace the whole string. Blocks in a series string share the same charge current, and a new block placed alongside blocks that have aged for years will not match them on internal resistance or capacity. The string performs to its weakest block, so the new blocks do not deliver their rating and they are pushed to work against the older ones. Mixing generations compounds the problem, because case size, terminal type and rated capacity all differ.
How do I keep the same runtime when I replace the blocks?
Match watts per cell at the duration you need and at the end voltage the system is set to, rather than matching amp hours. Read the constant power table at the correct column, compare it against the load per cell, and confirm the string configuration is unchanged. If the replacement block carries a lower watts per cell figure at your duration, the cabinet will hold the load for less time than it did when it was commissioned, whatever the amp hour rating suggests.
What is watts per cell and why does it matter for cabinet fit?
Watts per cell is the constant power that one 2 volt cell inside the block can deliver for a stated duration down to a stated end voltage, and a 12V block contains six cells. It matters for cabinet fit because it is the figure that decides how many blocks the cabinet needs to hold. If a higher rated block lets you meet the duration with a shorter string, the fitment question changes from whether the block fits to how many positions you actually need to fill.
How many battery strings can I run in parallel?
Stryten Energy recommends a maximum of four parallel strings in high rate applications, where high rate means a load that would discharge the battery in 60 minutes or less. Cable connections from the bus or the load to each parallel string are preferred over paralleling the strings to each other, because that arrangement shares current more evenly between them. Confirm both the series count and the parallel count before ordering, since the total block count drives both the quote and the floor loading.
What information does CPBS need to quote a 12V block string replacement?
The model number and quantity from an existing label, the shelf to shelf clearance and shelf depth, the number of blocks in series and strings in parallel, the required backup duration, the system minimum voltage, and the room ambient temperature. A photograph of the label and a photograph of one full shelf answer most of the remaining questions. Send them to Tom Kierna at 630-984-9718 or sales@criticalpowerbatterysolutions.com and most requests are identified the same day.
About the author: Tom Kierna is a Battery Systems Specialist at Critical Power Battery Solutions with more than 40 years in industrial battery systems, including 15 years across GNB and Stryten. He specializes in Sprinter and E-Series AGM block battery selection, cabinet and rack fitment confirmation, and UPS application sizing. Last updated August 6, 2026.
References
- Stryten Energy. E-Series AGM325, AGM370 and AGM539 product brochure: rated capacity in watts per cell, nominal dimensions, height over terminals, weight, terminal type, and constant power discharge tables from 5 to 90 minutes at 25 degrees C.
- Stryten Energy. E-Series AGM installation and operating instructions: terminal torque, temperature variation across the string, floor loading and anchoring responsibility, parallel string limits, and connection practice.
- GNB Industrial Power, a division of Stryten Manufacturing LLC. Marathon and Sprinter NEXT installation and operating instructions: installation practice for the preceding generation of the same blocks.
- Sprinter UPS Block Battery Selection Guide, UPS top terminal valve regulated lead acid block batteries: published dimensions, weight, and terminal type for legacy Sprinter blocks including the S12V300F.
- IEEE Standards Association. IEEE 485 Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications, referenced at the method level for duty cycle sizing and aging margin.
- IEEE Standards Association. IEEE 1188 Recommended Practice for Maintenance, Testing, and Replacement of Valve-Regulated Lead-Acid Batteries for Stationary Applications, referenced at the method level for ohmic baselines and capacity testing.
