Just ordered 2x280Ah 12v Eel Batteries with custom JK BMS pre-installed by Howard's t

[Tytorres]

After weeks of research, I finally decided on Eel Battery: https://eelbattery.myshopify.com/pr....39865471008857

Better bang for the buck thank Ampere Time, and more secure and easier for a newbie like me than fixing a bunch of Docan power EVE cells with steel plates and rods etc. Plus Eel is more flexible and has better metal case than Chin or Ampere time and cost per Wh is substantially less also. Basically for $200 more than cells from Docan Power, I get a metal case all assembled and a 5 year warranty. Finally, Howard is awesome. Asked for JK BMS instead of factory BMS and he agreed. Told me I just needed 1 JK for both batteries in parallel, so I saved money there. He also welcomed my questions about setup after they arrive.

Ships tomorrow and 30 days en route to the southern AZ desert. I'll keep you guys posted after they get here.

This is for a 2009 Trailmanor 2720SL. Upgrading from 2x60Ah deep cycle lead acid batteries of slightly different sizes and ages from previous owner. Currently have his 2x100w solar panels and a Windy Nation SCC that I don't think works very well (battery indicator says "empty" but voltage says 16+v and my batteries seem to be ok with my current hyper-conservative use patterns).

Will probably upgrade with 3x200w Rich Solar panels in addition to the existing 2x100w. Still need MPPT controller that can handle all that and a large inverter.

Thinking of getting this inverter: https://www.ebay.com/itm/290987608713

Rickst29 just thoroughly tested one of those and it passed with flying colors. Lots of bang for the buck.

Power usage will be high, between coffee maker, microwave, and perhaps occasional (and brief) air conditioner use. Also thinking of powering a 110v 335kWr/yr fridge/freezer unit.

I admit I wish I could get the BMS, SCC, and Inverter to all talk to each other using a single app. Not sure if there's a way to do that.

Also, my ultimate goal is to find a way to automatically make my camper let me use all my built-in AC outlets on battery power UNLESS I plug in. I know that involves and automatic transfer switch but I don't know where that piece goes among my components. Also trying to avoid replacing my factory Trailmanor converter if possible.

Any other tips and tricks (and especially instruction and correction!) would be most welcome.

[Casey Freswick]

I am certainly not the expert in these matters. Rickst29 is. But he made it clear to me when I went to a lithium battery that I would need a new converter that charged lithium batteries. Check out his suggestion. In addition I replaced the wires to hand the heavier electric output. But things are now working much better.

[rickst29]

Without compression rods and plates, the cells within their uncompressed case will have somewhat shorter lifespan. But it might not matter very much.

With two parallel battery packs, each should be protected by 350A class-T fasting acting fuses on their way to a common "+12V" shared bus bar. Do not use a mere ANL fuses to protect BMS and the battery packs, they're far too slow to respond to a short circuit. This one, in quantity 2: https://www.ebay.com/itm/284848435149. Or you could "downgrade" to smaller size (300A) and get a more famous manufacturer, with fuse block and cover supplied, here: https://www.ebay.com/itm/265680106840

Photo show my own Bussman Class-T, with the containing project box temporarily opened and set on top for the photo. (Bus bars were also temporarily uninsulated, for the purpose of testing high-current "active balancing".)

For the case of Littlefuse, you will have the hassle of building or buying similar small project boxes to contain the fuses, connecting your top-most cells using an extremely short wire segment no smaller than AWG 2/0. Depending on the distance to your inverter lugs, you might want to upgrade the longer wires (from the "output" sides of the two fuses, each reaching to the Inverter's 12V input terminal lug) up to AWG 4/0, for less voltage drop while running at high power.

You might also want to add a coulomb counter for each battery (along the grounding cables into the Inverter grounding lug, although the BMS voltage readings should be your main guide regarding battery State-of-Charge. JK BMS provides a "remaining battery percentage" which isn't very accurate.

I use the Inverter's DC lugs as my DC bus bars. If you do the same, you will have 3 high quality terminal lugs stacked on each of the Inverter's DC power lugs (one from each battery pack, the other supporting TM shared 12v loads and grounding) In my case, the "12v" wire contains a smaller 100A fuse (not yet fast-acting Class-T, but i have ordered an upgrade for that ANL fuse) and ends at a plastic-enclosed "12v" power distribution block.

The power distribution block contains wires for the Solar Charge Controller, a fan for the battery+inverter compartment, an external 12v power port, and the WFCO 12v "main wire", which ends at another distribution block behinds the WFCO. (That 'behind-the-WFCO' block also connects the 120-VAC power Converter and two wires into the WFCO's 12-Volt fuse board, using both the "Inverter Input" and "Battery Connection" ports as input power connections to the Board. My Power Converter can exceed the 40 limit of the WFCO fused "inverter input" connector. Use of another power distribution block allows high current from the Converter to go directly to the batteries, bypassing the fuse board entirely. The presence of dual 40A inputs also allows the fuse board to receive more total current, although I don't think that such high current has ever been used by my "downstream" DC connections.)

Your JK BMS units don't have the heater function, but are otherwise similar to mine. Lot of settings will need to be tuned (especially maximum charge current, and over-voltage/under-voltage limits). The 'Discharge Overcurrent Protection should be pretty severely reduced, because JK does not have a separate setting for the maximum instantaneous current. (I've got my value reduced to 2 seconds, allowing for just a bit of peak draw from the Inverter on AC rotor start-up and possibly high-reactive loads coming into the Inverter from the Microwave Oven).

The default values of Under-Temperature Protection for charging, and its corresponding recovery parameter, are both FATALLY LOW for LFP battery cells. They must be raised above zero, "recovery" temperature raised first. My values are 3.0 C for charging shutdown, and 7.0 C for subsequent recovery.

The maximum CMOS temperature limit in JK BMS is not tunable, and preset to a value of 100.0 C. I feel that to be "too high" and wish that it could be configured to kill high-current discharge in cases where the measured temperature exceeds 85 C.

[Tytorres]

Thanks for the replies so far!

Howard let me know that the factory is making a custom metal case for me to make all the cells into a single battery that will fit inside my TM battery compartment. This should mean I'll only need one fuse, right?

Also, I finally won the Advanced Power 5kw/10kw inverter auction. On my way now!

I'll post again when I find out exactly how this unfolds but so far so good!

[rickst29]

Originally Posted by Tytorres

Thanks for the replies so far!

Howard let me know that the factory is making a custom metal case for me to make all the cells into a single battery that will fit inside my TM battery compartment. This should mean I'll only need one fuse, right?

Also, I finally won the Advanced Power 5kw/10kw inverter auction. On my way now!

I'll post again when I find out exactly how this unfolds but so far so good!

The custom case should contain 2 separate battery packs within the single box. To run the air conditioner, you will need separate BMS and fuses for each set of 4 cells. Each 4-cell "set" should run its own pair of main cords ("12v" and grounding to reach the Inverter input posts.

The Inverter posts mounts can handle multiple "main" cords on each post. Use a screw, lock washer, nut, and regular washers to hold the lugs on the cord ends very tight.

I have wired my Inverter "DC" posts as primary "power distribution" and grounding bus connectors for TM "12V" loads. Battery "12v" cables go from the battery fuses direct to the Inverter 12' input, but a 3rd cord (kinda large, I used a 1/0) goes from the same lug, as the power source for a multi-connector DC power distribution block. That insulated block terminates all of the "12v" load and charging wires (I have several things which don't go through the main fuse panel).

Similarly, I have a 3rd wire from the Inverter's 12v Ground post, same size, going into another distribution block for the 12v grounding connectors (one wire to the DC fuse panel and Converter Board within the WFCO panel; another for the Solar charge controller; another for the external 12V port; another to drive the battery heating pads in extremely cold weather, and maybe some "etc" which I've forgotten at the moment).

The larger "main" grounding wires from the battery packs go through "Coulomb Counter" monitors first, then into the corresponding BMS "P-" leads, and then into the lowest cells of the battery packs.
- - -
Your Inverter is very large, but it still might not "like" supporting the extreme loads of 'compressor start' with each power cycle of the AC compressor. It's more money, and requires that you remove the existing start+run capacitors from the AC unit - but these have a pretty good reputation: https://www.ebay.com/itm/403149743516

[Tytorres]

They want to use just one BMS for the 8 cells inside the custom metal case. Since I bought that big inverter they actually want to change to a higher-charge BMS, but it is not a JK and doesn't have a Bluetooth feature, which was important to me. It's actually the reason I went with Eel to begin with. Not sure now if I want to proceed.

Data Sheet on proposed BMS replacement:



Thoughts?

[rickst29]

Originally Posted by Tytorres

They want to use just one BMS for the 8 cells inside the custom metal case. Since I bought that big inverter they actually want to change to a higher-charge BMS, but it is not a JK and doesn't have a Bluetooth feature, which was important to me. It's actually the reason I went with Eel to begin with. Not sure now if I want to proceed.

Thoughts?

Insist on dual JK2A8S20P-H units (or one each 'JK2A8S20P-H' and 'JK2A8S20P', without the heater interface and about $4 less costly.) For your big Inverter, you need more than 200A continuous power:

200A * 12.9 Volts = just 2580 input VA. With power lost converting to 120-VAC in the Inverter, that's probably not more than 2200 watts at the 120-VAC outlets. You should be able to provide double that into your Inverter, with higher peaks.

SO, in the same box or not, you have two separate battery packs (with separate BMS on each 4-cell pack, separate 350A "Class-T" fast acting fuses). That allows a bit less than 700A total extremely short periods, or a bit less than 400A continuous (total). Why downgrade into cheaper BMS units with pathetically weak balancing current, no cellphone App, and the same current maximums? Even with two of them, it makes no sense.

[Cya3124]

Originally Posted by rickst29

Without compression rods and plates, the cells within their uncompressed case will have somewhat shorter lifespan. But it might not matter very much.

On the subject of "to compress or not to compress", may I present the following. I have decided to go non-compressed with my home-built 100 Ah bank (four cells). The lifespan of the normal user is incredible even without compression.

[video]

[rickst29]

Originally Posted by Cya3124

On the subject of "to compress or not to compress", may I present the following. I have decided to go non-compressed with my home-built 100 Ah bank (four cells). The lifespan of the normal user is incredible even without compression.

This reply is extremely detailed.

First, you're looking at a fairly old video (cell anodes have been changed in design, chemistry, and manufacture after that time.) The guy does a lot of unqualified yammering (with no tests), and refers to older-model battery cells with inferior anodes. (Although cells also cost a lot less money, back in the days of this video.) He has nothing to say about specific issues of aging due to high discharge rates, such as electron starvation.

His 'conclusions' seemed to be that you should limit your use of an LFP battery to only 50% or 60% depth of discharge, leaving at least the bottom 40% of battery capacity unused. The chemistry and construction of modern cells of modern cells allows for higher depth of discharge, down to roughly 20%, with virtually no effect on lifespan.

EVE does know more about their battery cells than this 'garage guy', and they designed their test well. They took the cells all the way down to accelerate the aging process on purpose, shortening the total amount of testing time required.
- - -
My own opinion (which is way more qualified and expert than that of "garage guy"), that "it might not matter so much anymore" is based on the fact that very recent improvements by EVE, CATL, and CALB have been leading to very generous lifespans without adding compression.

If 3000-4000 cycles (old cell designs) is "good enough" for you, and it might be, compression might not be worth the trouble and expense and added cost. In his opinion, 3000 cycles is "incredible", while I think that such a lifespan basically sucks. But, In the most modern cell designs, you can approach or even exceed 6000 cycles WITHOUT compressing them. Even I consider that to be a more than adequate lifespan.

The video showed several supposedly "compressed" battery pack photos which did not use springs. These springs are a very costly item, but any attempt to construct a "compressed" battery pack WITHOUT springs is virtually useless, and may actually be harmful, because the amount of compression varies far too greatly as the cells expand and shrink with changing SOC and temperature.

Only springs can do a half-decent job of emulating the test press, which provided totally fixed PSI on the cell faces (even as their width changed with SOC). With "6000 cycle" cell designs now available in the marketplace, even I think that the cost and hassle of adding springs is hard to justify. In your own case, with a mere 100Ah battery pack, the high cost of the springs (around $40) is also hard to justify. Two end plates, and a set of "L" channels needed in order to spring pressure across the entire surface of the cells, also adds more construction time and money.

[Cya3124]

Originally Posted by rickst29

This reply is extremely detailed.
First, you're looking at a fairly old video

It is on his Videos page as posted two months ago. And if it was old, everyone waited until two months ago to comment? Not sure where you get that the video is "very old".

I'm not sure he was advocating limited discharge, just an observation on how the average user would utilize the battery(ies). I plan to use mine camping or on the boat over a day or 3, so it would see limited DOD. I feel I fall into his "compression won't do much" category. My batteries are of the new(er) design. They are maybe a year old, but by your reasoning, I should toss them.