Can I change to a Lithium battery without changing my converter/charger on my 2004 2619? And which converter do I need?

[rickst29]

My hassles with the "suicide plug" (and related circuit breaker shut-downs) only apply to using my Inverter to providing power backwards through the existing "downstream" circuit.

 

[bkncd]

Hi. I've been away on a multi-state RV trip, and may good replies have occured since my last post. Let me start at the END of the Thread, rather than your questions from from my earlier post.

I also have a 2619, but it is a later model than than yours (late 2006, after the factory switched to using a "WFCO" powerr center. I have a 12-cell compressed battery assembly underneath the storage seat, but I wired up 3 BMS units to use it as 3 "12.8 volt" packs in parallel (Not 12 cells in series at 38 volts). The low voltage is compatible with everything using 12V in the TM.

In order to connect between the new battery location and the original power center replacement components, (under the bathroom wall and the raised "seat" of the bathbtub) you need to add a new and larger 12V DC cable to support high current between to AC->DC power converter and the batteries. My AC->DC converter (a "55A" PD model) board can put out 60 amps, that is more than any port of the WFCO board can handle. (it is far above the limits of your older Parallax fuse board, you wil need to replace that board ) I route the +12V output of the converter board into a fully insulated "4-port power distribution block" behind the WFCO unit. The second port connects a long 12V wire, AWG-6, to the front battery section of the TM. That wire runs through LiquidTite conduit clamped underneath the TM, I also ran a portion of the unbroken conduit into and through a section of the of the street side steel frame box, a section which did not have interference from torsion bars.

That "long 12V connector" comes up into the front seat storage. It connects into port #1 of a 4-port Maxi-Fuse block with a 60A Maxi Fuse. (The 6-AWG cable is good for 65 Amps).

Looking back at the other end (under the bathtub, behind the load center) that wire connects into port #2 on a non-fused power distribution block". (The PD Converter 12v output went into port #1.) Ports #3 and #4 are both used to connect the WFCO DC circuit board power ports, with balanced wire lengths leading to 40A fuses on the WFCO fuse board. (This use of "balanced wires with smaller fuses" is illegal in home wiring, but it is my best scheme for the WFCO fuse board. Those dual ports "left side" ports can only handle wire size AWG-8 and 40A fuses. The combination of wires might be good for 60A total, but if high DC downstream loads caused one 40A fuse to fail, the second 40A fuse will also fail quickly in a cascade of overcurrent burnouts.)

In addition to a 3 BMS units, you see slightly unusual negative wiring (from the BMS units) into a pair of coulomb-counting current monitors. One handles two battery packs with in parallel with 200A maximum continuous current each, the other handles a single BMS with a higher BMS limit (280A amps).

What is the voltage of each cell? I have run across someone selling some CATL 3.2v 310Ah extra cells that he supposedly never installed for $40 each. Was thinking of grabbing 4 of them to connect in series for a 12.8v 310Ah Lithium battery... or maybe even 8 of them for 2 batteries. But I'd still have to wire up some safeguards like you have and I don't know that that would take or cost. The price of the cells seems a bit too good to be true, but the seller has a great reputation.

 

[Wavery]

What is the voltage of each cell? I have run across someone selling some CATL 3.2v 310Ah extra cells that he supposedly never installed for $40 each. Was thinking of grabbing 4 of them to connect in series for a 12.8v 310Ah Lithium battery... or maybe even 8 of them for 2 batteries. But I'd still have to wire up some safeguards like you have and I don't know that that would take or cost. The price of the cells seems a bit too good to be true, but the seller has a great reputation.

Something does sound a bit fishy.

Go see the cells and bring a multimeter. Be sure that each cell reads 3.2V. More than likely, they are the older style cells with female threads (in aluminum) for the cable connectors. Be SURE that the threads aren't stripped. They are pretty easy to strip and once they are stripped, drilling and tapping to a larger size is quite iffy. I've read reports of success and failure. If they are laser welded studs, you should be good (in that regard).

$160 for a 310ah battery is pretty hard to pass up. All you would need is 3 curved busbars, a good BMS and 3 plastic separators.

Just remember, you aren't done with just the cells. You'll need about $150 worth of other stuff to make it a battery so you'll end up with $310-$325 in the thing. Still not bad.

Be sure to get the correct size

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[bkncd]

Something does sound a bit fishy.

Go see the cells and bring a multimeter. Be sure that each cell reads 3.2V. More than likely, they are the older style cells with female threads (in aluminum) for the cable connectors. Be SURE that the threads aren't stripped. They are pretty easy to strip and once they are stripped, drilling and tapping to a larger size is quite iffy. I've read reports of success and failure. If they are laser welded studs, you should be good (in that regard).

$160 for a 310ah battery is pretty hard to pass up. All you would need is 3 curved busbars, a good BMS and 3 plastic separators.

Just remember, you aren't done with just the cells. You'll need about $150 worth of other stuff to make it a battery so you'll end up with $310-$325 in the thing. Still not bad.

Be sure to get the correct size

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I asked this question:

"Have these ever been installed? The listing implies that you bought them and never got around to installing them. Have they been used?"

His response was to simply mark the listing as "Pending".

So, who knows if it was such a great deal somebody bought all of them (he said that he had 32) or if it was bogus. The listing had only been posted for 17 minutes when I asked the question.

 

[rickst29]

What is the voltage of each cell? I have run across someone selling some CATL 3.2v 310Ah extra cells that he supposedly never installed for $40 each. Was thinking of grabbing 4 of them to connect in series for a 12.8v 310Ah Lithium battery... or maybe even 8 of them for 2 batteries. But I'd still have to wire up some safeguards like you have and I don't know that that would take or cost. The price of the cells seems a bit too good to be true, but the seller has a great reputation.

All LFP cells are sold with a "nominal" voltage of 3.2 volts. That's around 40% SOC, The actual voltage range is from slightly above 2.5 volts to a maximum of 3.65 volts. Its best to spend almost zero time at or near those limits, except that you should boost to nearly maximum voltage every 3-4 months to help assure high capacity oover the cell lifespan.

If those cells were sitting at shipping (around 2.8 - 2.9 volts) for more than a few months, they might be able to reach 3.65 volts anymore. If the seller will guarantee the terminals to be undamaged AND the maximum charge voltage to be above 3.60 miminum volts, it sounds like a good deal.

Brand new cells like those shipped to your house, qty=4, are around $75-80 each. I can seel you a slightly used BMS, with maximum discharge current limit of 200A, at a deep discount. (You would need to upgrade to much larger "battery wires" to go any where near that limit.) I have a number of spare busbars as well - fixed length but with terminal holes which do fit those cells. If you don't want to mess with compression, your only remaining hassles would be upgrading wires the the charger voltage.