Solar Pecron E2000LFP - Battery Discontinued Bummer + DIY expansion details

Short version: I purchased a Pecron E2000LFP unit in April 2025, along with solar panels. At the time, the expansion battery was on my ‘get later’ list. But I was really late to the party, and by the time I was ready to purchase it last month, it was discontinued / sold out everywhere. Buying a used battery is a dicy proposition, but even that was not available. With PNW grey short days coming, this was a bummer!  After a few rainy days with the Pecron dropping down to 1% of battery, this was clearly not workable  (Cue Three Dog Night: One is the loneliest number...)

After researching, I found a DIY solution. I connected a third-party 24V 200Ah LiFePO4 battery to the E2000LFP's cascade port using ordinary 4mm banana plugs, 12 AWG wire and a 30A fuse at the battery. It is successfully running and charging from solar.

I'm not an electrician, no expertise with solar beyond plug and play, dyslexic with numbers, total newbie. I leveraged Claude.ai to work out the plan: to survey / research the Pecron specs and the source videos and forum threads, define and doublecheck the math (voltage class, fuse and wire sizing, wire resistance), and lay out each connection one step at a time, with multimeter check points / expected results. AI can be wonky and this involved electricity which can fry things and start fires... so I did a reality check on the plan with a builder friend with electrical experience. Total cost was about $880, though I bought tools and packages of items where I only needed a few and anyone with electrical leftovers might not have had to purchase. Also more experienced peeps might have been better shoppers - I ordered everything from Amazon in the middle of the night after verifying the plan. On implementation, what would have taken an electrician 5 minutes took me hours because I was doing new things, including multimeter checks before many steps. I'm posting the whole path so other E2000LFP owners stuck without an expansion battery can follow it or improve on it…  WARNING: Long post. Doing this certainly invalidates the Pecron warranty. And if they still had the ONLY expansion battery that works with my unit, I would have bought it and not done this. If you have a different Pecron unit, your math could be completely different.


How the DIY idea came together:

(1) Old Jarhead Youtuber introduced the idea  (https://youtu.be/-kITqaozULA?si=vFcGbDf27DeYlOLP)
He is a YouTuber who innovates with solar and tech gear. He showed exactly how he added an expansion battery to a Pecron E1500 unit with equipment links. In the comments, someone asked about the E2000 and he said it should work, "but check the voltage first."
After reviewing all of the documentation available about Pecron's now unavailable EB3000-24V expansion battery, it sure looked like he had duplicated that functionality.

(2) The Solar Lab Plus Youtuber naysayed the idea  https://youtu.be/zrOTqOSJbAs?si=VH798hjmSkdL3v-e
As I looked for a reality check, I viewed this video, which appeared to me to be poorly thought through. I honestly would have expected more reasoned evaluation from someone with this level of experience, as if he did not comprehend the difference between a trickle charge input battery and an expansion battery that builds the resource pool of charge. It's not an apples-to-apples comparison. He uses a Bluetti with an external lithium battery plugged into a power input, which basically makes it a trickle charger. When he shows the Pecron, it has its proper expansion battery and cascade connector, clearly not a trickle charger. His points on simplicity and safety are good. Two of his warnings still apply: the Pecron can't talk to a third-party battery, so its display showing battery percentage becomes inexact, and you become the one managing voltage matching, fusing and monitoring.


(3) UNACCEPTABLE One that Did the Stuff and Made a Video that had a working example for my Pecron unit:  https://youtu.be/vU4wKALAlj4si=VQW0WzLJLbLbqWgN
As I looked for any real world examples of someone who had DIY'd an expansion battery with my specific E2000LFP model, I found this video by a casual off-grid fella in a dusty crawlspace. He first reviews his car battery top-up through the DC input, and recharging it with a trickle charger from the Pecron's AC outlet - no big news. Then he probes the Pecron's cascade port (where an expansion battery connects to expand the total charge resource pool) with his meter and makes some guesses. The port measured about 26.6V at 84%, with about 27.3V expected at 100%. This indicates that it is a direct parallel connection to the internal battery. Two internal fuses sit behind it, which he believed were about 30A each. That guided a 30A fuse choice. His 4mm banana test leads fit the two large sockets in the cascade port. This suggested an alternative option to connect since Pecron's cascade cable was only sold with the E3000-24V battery, never separately, and also discontinued. Conclusion: Pecron's cascade port is a direct parallel connection to the internal battery: no charge controller in between, current flows both ways. Treat it like joining two batteries, because that is what it is.



Battery selection: VOLTAGE CLASS is apparently VERY IMPORTANT. The E2000LFP's internal battery is 25.6V nominal (8S LiFePO4, 1,920Wh).
Several Pecron models (the E1500LFP family) are 51.2V.
A 48V/51.2V battery on an E2000LFP cascade port would put roughly double the rated voltage on it.
The added battery must be a 24V-class (25.6V nominal) LiFePO4 for a Pecron E2000LFP.



Ingredients:  (what I actually used)
- Battery: NEBUQUIC 24V (25.6V nominal) 200Ah LiFePO4, 5,120Wh, built-in 200A BMS, about $650. Max charge voltage 28.8V per its manual. Terminals are recessed threaded inserts with supplied bolts (not posts).  ($716.75)
- Fuse holder: Blue Sea 5191 MRBF terminal fuse block (bolts onto the battery + terminal). ($38.30)
- Fuses: Blue Sea / Bussmann MRBF 30A, 58V (5,000A interrupt rating at 32V DC). Buy two; a blown MRBF must be replaced. ($51.48)
- Wire: Kenhihi 12 AWG silicone wire, tinned copper, 15 ft red + 15 ft black ($16.27).
- Pecron end: 4mm screw-type banana plugs, rated 32A, red + black. ($13.02)
- Battery end: AIRIC heat-shrink ring terminals, 12-10 AWG, 5/16" stud (yellow). ($10.85)
- Tools: multimeter (Klein MM325) ($32.76), wire stripper/crimper (Haisstronica) ($32.57), a wrench, a lighter or heat gun, electrical tape, toothpicks (really), dish soap, adhesive cable clips for the floor run.
Why 30A and 12 AWG: the fuse sits below the weakest part of the circuit (plugs 32A, wire about 36A) and matches the roughly 30A internal fuses reported behind the port.


Recipe:  (thanks Claude.ai and my electrical friend - there is no way I could have worked this out on my own)
1. Find the cascade port polarity. Pecron doesn't label it. Multimeter on DC volts (range above 30V), Pecron switched ON. One probe in each large socket. A positive reading means the red probe's socket is +. On mine, looking at the port, the RIGHT socket is +, reading 26.6V. Marked + with tape or a dot.
2. Measure the new battery's resting voltage. Mine: 26.5V vs the Pecron's 26.6V. Close voltages ideal for first connection, as the charge will try to equalize.
3. Build the banana plugs. The wire enters the end of the plug and a side set screw clamps it. My 12 AWG silicone insulation was too fat for the plug sleeve, so I trimmed 3/16" off the sleeve's narrow tip and slid it on with a little dish soap. Measured the plug's bore depth with a toothpick (mine was 1/4") and strip slightly more than that (5/16"). Tighten, then tug-test.
4. Check that the new battery's stock bolt is long enough that it still grips with the fuse block under it. The threaded hole was 3/8" deep and the supplied bolt 3/8" long. Counting hand turns: 6 3/4 turns with just its washers, 5 turns with the fuse block tab added. That was plenty for a 30A circuit, so no longer bolt was needed. Don't overtighten; the threads are in soft metal.
5. Measure the real wire route, not the straight line. Mine was 139" (11 ft 7 in) around cabinets and along the floor. I kept the full 15 ft uncut because this setup will move as I graduate from glamping in a little trailer to tiny home. Extra wire length coiled loosely at the battery. Acknowledged minimal cost of wire length travel both ways: at a typical 10A, about 0.5V drop and 5W of heat in the wire.
6. Crimp the ring terminals (yellow insulated die) onto the other end of the red and black wires, tug-test, then heat-shrink until snug with a little bead of glue showing.
7. Fuse block onto battery + (fuse out): bolt head -> lock washer -> flat washer -> fuse block tab -> battery +. Point the block away from the - terminal.
8. Black ring onto battery -: bolt head -> lock washer -> flat washer -> ring -> battery -.
9. Black banana plug into the Pecron's - socket. No circuit yet.
10. Fuse and red wire together on the fuse block's output stud: fuse -> red ring terminal -> flat washer -> lock washer -> nut, moderately tight (Blue Sea max 75 in-lb). Close the red cover. IMPORTANT: From here the red banana tip is live: tape it or wrap in paper
11. THE KEY CHECK: measure across the last gap. Unplug solar so the Pecron's voltage holds steady. Meter between the red banana tip and the Pecron's + socket. Mine read 0.11 to 0.15V, which by my estimate means a first surge of about 2A. My go/no-go: under 1V go; 1-2V let it settle first; over 2V don't connect.
12. Red banana plug into the Pecron's + socket. No spark, no click, the display didn't change, and the red connecting wire and red 'gnome hat' fuse cover stayed at room temperature.
13. Confirm it's actually working (the Pecron screen won't tell you). Plug the solar back in, wait 15-20 minutes, and measure the battery terminals again. Mine rose from 26.5V to 26.7V. Meanwhile the Pecron only gained 3% (72 -> 75%) from about 120-140Wh of solar, when it should have gained 6-7% if it were taking all of it. Roughly half the solar went into the new battery. Connected and charging.

Outcome and questions
- The Pecron's percentage only measures its own internal battery. Because the two batteries sit at the same voltage, it's still a rough guide to both.
- The "hours remaining" figure is now far too low. It doesn't know about the extra 5,120Wh, which is about 3.5 times the Pecron's own capacity.
- I usually turn it off at night - press AC button to stop, press DC button to stop and the display screen goes dark. Not any more. Display stays on all night, only showing the lit up battery graphic with percentage under it
- To disconnect: pull the red banana plug first. Pulling the MRBF fuse also isolates the battery.
- STILL OPEN: I don't know the Pecron's peak charging voltage at the cascade port. My battery's max is 28.8V. When the Pecron nears 100% on a sunny day, I'll measure at the battery terminals and report back here. If you already know this number for the E2000LFP, please post it.

Questions, suggestions, corrections and improvements  welcome.  I'd especially like to hear from anyone who has measured the E2000LFP's charging voltage at the cascade port, or who has run a setup like this through a winter. I have 700W of solar panel connected to this Pecron unit, and will be watching the charging...