Allen Jackson

John Weiland wrote:
As an aside, the weekend's project will be to remove 6 X 6V legacy (=HEAVY!) lead acid batteries from my farm-yard golf cart...one or more seem wonky or underperforming and it's a good time of year to do some testing. In the meantime, I'm going to try replacing them with 3 and 4 LiFePO4 batteries (100Ah each) to provide the stock 36V or alternatively an upped 48V to the system.  Good rumor has it that the better quality carts of yester-year had components built like a tank....hence motors and controllers that can handle the increased voltage to 48V (power draw is the same....just a slight reduction in current).  The one component I did invest in is the solenoid which some say is best to keep at the same voltage as the battery pack.  The experiment:  Can these "non-locomotion" 12V batteries (100 amp BMS) power the cart at either 36V or 48V?  Because of the current demand at 36V, the BMS might be tripped.....but if the potentially 200-250A draw is distributed *equally* across all 3 batteries, it might be okay--especially as start-up and cruising amps range from ~50 - 150A.  It also could be a complete bust....but that's the excitement of experimentation!   Fun!!......

I typed out a detailed reply to this, and it disappeared... Round 2?

The current drawn is exactly equal in all the cells of a series stack, and your BMS shouldn't allow you to abuse your batteries for very long under those conditions.

For that application, you'll be much better off, with something like the 280 Ah cells and a 200 amp BMS.

I'm struggling with the choice to build something to my needs, vs build to the BB requirements...

As I contemplate building a better version of the "Charge and Carry" lithium battery box BB (because having AC available would be really nice), I realize that I can build to the posted minimum requirements, or I can build something that would be truly useful in a field/off grid/camping experience.

The conundrum comes down to weight/capacity. My biggest issue with my DC 12 volt system, is that it's uncomfortably heavy, especially for that cheap plastic toolbox. Unfortunately, my calculations suggest that for camping with family (not solo), I probably want to have 8 KWh of energy stored, for the various electric appliances/cooking apparatus I'd love to have available to use. The DC box is close to 60+ lbs and the weight would more than double if I made a system with double the battery capacity AND also had an inverter, plus all the AC outlets/breakers, etc.

I suspect that a 150 lb box of anything won't qualify for the BB, and it would surely be a challenge to carry or transport too, so I'm contemplating if making it modular would disqualify it for that BB, or worst-case scenario, I buy some more 105 Ah cells, and build a much lower capacity, but lighter box that only had 2560 Wh (2.5 KWh), but weighed less than the 12 DC system...

If I go the modular route, I can wire it so that the BMS power is disabled until both battery modules are connected, and the BMS automatically measures the resistance of the balancing wires, so I don't have to worry about those either. The AC side would also have to be a separate module too. At what point does it stop qualifying for the BB?

If I just build with 105 Ah cells, I'll need to pony up another wad of cash, to get more of those, because I only have 4 right now, but I expect I'll have to find a new use for them after the BB is completed, because I don't think I'm willing to live with a 2.5 KWh energy cap - isn't that why hand trucks exist???

I'll try asking for guidance in the BB clarification thread, and see where that goes, even though they have not answered my last question about the same BB - where I'd pointed out that the 220 volt requirement was an error - none of the examples they gave can support or provide 220 VAC. (It's a 120 Vac 30 amp RV outlet, NOT a 220 volt outlet)

This was educational... I'm finding that when my engine is off (with no loads on the battery box) it's slowly charging my vehicle battery/electrical system.

With no other loads on the battery box, and the engine running, there is a very slight charging going on, where the vehicle is charging the battery box, but it's only about 1.44 amps, which beats a sharp stick in the eye, but not the level of charging I was expecting by any means. The regulated voltage of the vehicle is just not high enough to get a significant amount of charging current, so I'd have to go with some DC to DC booster/charger, if I really want vehicle charging. I'd probably be better off unfolding a few panels on the roof - they're already paid for 😉

On the plus side, if I make sure it's fully charged before leaving home, it will probably run much longer with no other charging for much longer than I am willing to travel?

I'm not exactly sure where best to post this, but I won't submit it as a BB to keep from complicating things.
If it's worth some oddball points, fine too, but I'm primarily trying to go on record as to what is there for the next person to be able to find.

My family was recently staying at Allerton Abbey, as SEPPers.
The pressurized water system up at the labs stopped working.
They're a little short-handed for bootcamp labor and probably are prioritizing tasks to better prep for the winter.
No one who was involved in the original construction of this system, is available, and probably no longer at Wheaton Labs.
They don't have, or don't have access to any documentation of this system.
I volunteered to look at the solar pumping system, to troubleshoot and at minimum document it for future users.
Everyone in my family likes water 😉

This is not a complete documentation of the system, as it wasn't necessary to get to the failure - more on that later.

There are 2 strings of solar panels feeding the combiner box near the panel mount. The lower 3 are the same models and are in series. They are about 335 watts each. The top two are in the other series string, they're newer, and probably a higher power & different voltage than the lower ones, but that turned out not to matter, because that part of the system is working fine - there's solar power available at the charge controller, move on to the next part...

The charge controller was a few firmware revisions out of date, but the Bluetooth pairing code is on the sticker on the unit. Connecting to it immediately started one of the updates from my tablet (I own 2 of this same model charge controller).  After updating, the unit showed briefly, a slight charge current on the battery pack, then it dropped off to zero. It shows a battery capacity of 100 Ah, which may or may not be accurate, but it matched the battery monitor display on the side.

I say it may or may not be accurate, because that's part of the initial configuration process, to tell the system what size battery is connected, and the shunt that is being used, is likely a Renology brand shunt (not a Victron shunt), and it plugs directly into the battery monitor (shunts periodically need to be recalibrated to stay accurate, because they will drift over time).

The biggest reason for suspecting a battery size mismatch, is the physical size of the batteries that are barely seen from above, without taking the system apart. There's a Daly brand 200 amp BMS, sitting on top of a wooden separator that mostly covers the batteries. From the visible edges, it looks more like a set of 8 cells, in the ballpark of 280 Ah capacity, and incorrectly wired as 2 strings of 4 batteries, so they could get by with only one BMS. Unfortunately, that also means that there really isn't any monitoring of the battery health, but it's probably still at least greater than 100 Ah. If the BMS and the battery monitor are both claiming that the battery is only a 100 Ah battery, the solar charge controller won't keep charging it past that point BUT even THAT shouldn't keep it from working at all, so move on to the next part...

The label on the BMS claimed that it had Bluetooth as a feature, but every Daly BMS I've ever seen that supported Bluetooth had a plug in dongle for it, and the port for that was empty. The Daly website also doesn't appear to list this exact model BMS as a supported model anymore, but STILL that's NOT the root cause of the system failure... If the BMS wasn't working, it wouldn't show voltage from the battery positive to the ground terminal, so either way, the BMS is NOT the problem...

There's 14 volts at both the fuse panel and at battery system main power switch, which is also what's wired DIRECTLY to the pump (There's NO external fuse or breaker on the pump supply line!). According to the pump mfg website, this model pump is internally "protected from overload", and has an internal pressure switch, which is supposed to turn off around 55-60 psi.

The external pressure gauge shows only 25 psi, and the motor leads show proper voltage, but the pump doesn't turn on...

I would guess that the internal pressure switch is not working properly but without further disassembly, there's no way to tell, and disassembly would probably void any warranty remaining, which is supposed to be 4 years (according to the website), and according to Paul, "this is a NEW PUMP!", so I won't try taking it apart.

I'd recommend an external circuit breaker in the future version, so the motor doesn't have to destroy itself to protect from any overload condition. Ideally a 20-amp resetting breaker inline, instead of a fuse, because it's not in a particularly accessible location and a breaker will mean less man-hours to keep the system running

I think I've finally completed the requirements for the electricity sand level badge.

I humbly submit my small DC only solar system:
https://permies.com/wiki/21/112937/pep-electricity/Small-DC-solar-system-PEP#3999395 - 4 points
Repair a 12 Vdc lamp here:
https://permies.com/wiki/112695/pep-electricity/PEP-BB-electricity-sand-lamp#3758426 - 1/2 pt
And installing a permanent 110 VAC light fixture:  https://permies.com/wiki/35/112697/pep-electricity/Install-permanent-AC-light-fixture#3756419 - 1/2 point

For 5 points & no duplication here

Logically, the next step is to show the container I used to build it in. I ended up using a cheap plastic toolbox from Harbor Freight, that came as the outer box of a nested set of 4 toolboxes. It works so far, but it's less than ideal, because the latches & hinges are the weak points, and this will probably be over 60 lbs when done.



I initially tried putting the batteries at one end.



That proved to be too imbalanced to carry with the handle, so they were moved to the center and blocked with some of the close-cell foam packaging they arrived with...



Moving into this box was also in conjunction with switching to a much higher capacity BMS, shown here:



And connecting the balancing/cell sensing wires:



The unused wires can just be coiled up and taped out of the way.



A 300 Amp BMS should have a 300 amp-capable wiring harness and connections! As I'm really not intending to need or use that much raw current, I'll wire for 200 amps, & fuse for less than that. The recommended max normal charging rate is 157 amps for this battery pack, so I can do at least that...

This 2/0 welding cable is rated for over 200 amps, so it should be sufficient, and I have adequate crimps to put on the ends.



But since I really don't expect to have reason to push the 150 amp breaker, I'll use this 2 gage cable - it's much easier to bend, and this welding cable has pretty high temp insulation (105 C), so it should be good for up to 215 amps.



My initial mockup included 12 Vdc outlets with USB charging ports, to charge my tablet and mp3 player while working on wiring the BMS and the rest of the system, but I found out the really cheap fuse holders for the USB outlets started melting (without blowing the fuse!, so I scrambled for a heavier duty fuse and wiring harness for them.



Very heavy-duty 12 Vdc socket, with a 20 amp fuse and 12 gage wire



Public service announcement:
If you are ever tempted to buy & use these cheap breakers from Amazon, under NO circumstances, should you be using 6 AWG wire that these terminal lugs are sized for - if you do, your wire will burn up long before you EVER get to 300 amps.!  Use large enough wire to carry 300 amps, or use a smaller breaker rated to protect the size wire you actually are using...



This is a much better design for a heavy duty breaker, but I didn't find it soon enough to replace the other one (yet)



These are what I'm trying to use, but their ports aren't really large enough to support the large enough wire to match their rating without a lot of work & modification.


Working with larger crimps requires bigger tools:






The struggle to fit it is in this post:  https://permies.com/t/120/274663#3772120

It's a good idea to put heatshrink tubing on the ends, but don't cover up the flats of the lugs, for best contact.



This is one of the solar charge controllers in the system (one of 3), and it's the one I started with:



Testing a mockup in the back yard, showed that it didn't generate enough heat to worry about additional ventilation, so it's ended up inside the box now.




The negative bus bar is shown here too, prior to connecting anything to it.  The left edge of the 300 amp BMS is toward the bottom right & mostly out of the frame here.




Here's a glimpse of the positive bus bar, with the 150 amp inline breaker and the 2 AWG copper cable connecting to the main battery positive post:



The 100|30 amp Victron in it's final home, working just fine:



I used 10 gage PV wire for the battery and PV sides of the 30 amp controller because neither of them will ever see more than 30 amps, although the mfg still recommends putting a 40 amp breaker on the battery side and some kind of DC-rated disconnect on the PV terminals too... I skipped that for now, but I'll get there eventually?

This is where & what I used for the initial 10 gage PV wire - I just cut off sections of the raw ends as needed to make the shorter connections and saved the rest for connecting to the solar panels later:  10 gage PV wire from Amazon

The top right corner shows the original parts before chopping the cable up, and the bus bars are also in this collage too.

(what's left of the 2 rolls is laying on the toolbox below the pouch that holds a multimeter)

And temporarily connected here:


The 40 amp inline breaker is visible on the far right side of this collage, and the lower left corner shows the USB outlets (which are truly awesome, but don't use the stock wiring that they come with, it will melt...
Best to put spade lugs on your own 12 gage wire with a 20 amp inline fuse...



I also replaced the ring terminals on the ends, with smaller ones, because there's no way those wires needed to be connected to a 5/16" lug on the bus bar...

I've added a few more controllers, but they are the 100|50 amp variant




The 6 gage terminal lugs I ended up using on the 6 gage wire, when needed (for 50-amp connections to the bus bars from the 50-amp controllers):



BTW, this is the basic schematic I'm following for this build - although I have more than one charge controller they always connect in parallel), and initially, I've skipped the circuit protection on solar side. I DID include a main breaker on the battery positive connection (not shown in the schematic), though!



The AC charger has clamps, and I'm debating whether I want a permanent dedicated socket for it or not... Maybe a combo port for the AC charger OR a vehicle charger connection???

Here's a glimpse of the BMS screen, showing the function.



The 30 amp charge controller is way too small in capacity for my patience and my luck, as it can only charge a 12 Vdc system at a max rate of just over 410 watts in my real-world testing. For a 4 KWh battery, that would require about 10 hours of GOOD sunlight to recharge from empty, and the charge current of 30 amps or so, is far below the recommended max normal charge current of 0.5 C, which is 157 amps for this pack. I can and should strive to do better. I opted to switch to a pair of the 100|50 amp charge controllers that the top of the box, because they seemed to fit really well up there; I'll pull out the 150|35 amp controller and save it for a higher voltage project.



I've gone back and forth about the placement of the bus bars, but I realized that putting them on their sides at the bottom, would save space, but make them inaccessible, so that wouldn't work out well. I've split them up with positive and negative on opposite ends of the battery, which makes it a lot safer to work on too.  After the bus bars are placed, the rest of the placement is easy and mostly falls into place, since the wiring for everything else is much more flexible than the main bus bar feeders are.

The positive cable was more of a challenge because of the need/desire to put a breaker on it.


The most space-efficient place to put this is deep down here, but there's no tool access to connect anything else later!


These look like better options for general access and use, but getting the positive cable attached?!?


The negative side has far less drama...


Where the positive cable has landed. I cut off the insulation and just used heatshrink to get more bend.


We can do better than this - we have additional M4 connection points!


Have crimp, will travel?


For the negative side


And for the positive side too


Now both can easily attach to the M4 screws on the bus bars

I have one more placement challenge - if I were to ever want to use this box with an inverter, where I put that connector?!? If I put it on the end where the 3rd charge controller is sitting, it will interfere with pulling it out and I'll need to wire it in place before covering it up (the block of wood with the DIN rail breakers is slated to go over the negative bus bar).

The positive end of the box will be cluttered up with the other load connections and switches, so that's still a challenge.

I currently only have 4 of the black SB50 connectors, and if I'm going to actually use them for the solar/high-voltage inputs, I'll need 3 on the box for the 3 charge controllers, and 3 more for the cable harnesses to connect each to its own solar array, so I'll order more...


Anderson SB175 panel mount connector here - for either battery expansion or an inverter - will block removal of the controller


Wiring up the 50 amp controller - THIS IS A HORRIBLE PLACE TO GET STRAY WHISKERS! DON'T!


I found a hot glue gun!


I bought several variants of this breaker, from 40 amps up to 150 amps

The 60 amp version is a reasonable fit for the top-mounted controllers, and these terminals actually will fit 6 gage wire just fine.




it looks like a tight fit, but it worked, including the ferrule and the weather seal


When stripping wire, make sure there's no extra plastic left


It will fit, and there's enough play to open/close the lid too, with both 60-amp breakers under the lid.

I plan to hot glue the breakers in place, but I want to get both of them wired and make sure I can close the lid first.

This is also about as far as I had gotten with the mounting of everything, although I still should put holes in the box, to allow all the panel mounted items to be, well, panel mounted... And then the trip to Wheaton Labs happened, and it got packed up and carried across the country, while running a refrigerator and freezer, and recharging our other devices too.

It wasn't real pretty with the lid propped open to access the cables, and I forgot to pack the Allen wrench to tighten the connector on the 60 amp breakers, plus the other PV cables too, but it worked well enough to get us through the week! (And it technically does meet the requirements for the badge bit, as is, but it's certainly not the best version of itself yet).

I ended up finding a local solar dealer who would sell me some PV cable, so I was able to hook up 2 of the 3 controllers and 800 watts of panels. They seemed to max out at just over 600 watts total in the best of sun, but I don't promise that the panels were perfectly aimed, either.  It was certainly good enough for this trip.

First of all, I wish to apologize to the volunteer reviewer staff that I subjected my initial BB to, as it was a truly sloppy submission & I both know better, and can/should do better.  As I shall illustrate here:

Next, the disclaimers - electricity can be dangerous and so can stored energy systems, ie. batteries, so be careful, and if there's something/anything that is unclear, get help!  This is NOT a how-to guide, but rather a "How I did" journal. Use your best judgment on how to proceed with your own projects. Neither I or this site bear any responsibility for your actions, for better or worse. Best of luck with your own builds!

This set of batteries can pack a lot of energy in a small space:
314 Ah cells in a 4S configuration = 314 amps x 3.2 volts x 4 cells, which equals 4019.2 watt-hours, or 4 Kwh. Even if they were 100 Ah cells, it would still be a KWh of energy, so be careful with yours, no matter what size you use!

This thread is to showcase what I ended up using, not necessarily what I started with, as there was certainly learning along the way. As I also am building a larger system along with this one, some of the components are the same as used in both, and some components were simply purchased at the same time/arrived in the same Amazon box, etc., I will try to notate when it's unclear which parts are for which systems, but for example, Anderson SB connectors have a color code, which I will follow as close as I can, so red ones are for 24 Vdc connections, yellow ones are for 12 Vdc connections, and black ones are for officially 72 Vdc connections, although I will stick to using black for solar input connections of any voltage, to make them incompatible with either of the lower voltage ones (for safety).

Having said that, I did skip the permanent connections initially, for testing, but I fully intend to get there, and it will be pretty when done!
The same can be said of circuit breakers, but skipping those, is starting to gamble with some higher stakes... Please use common sense on that!

Starting with the batteries, or rather, the cells:
These are the commonly available EVE MB31 cells. I bought mine directly from a Chinese vendor in a bulk purchase. The specific cells I used in this build came from the factory with double M6 terminals. These pictures are not the exact ones that I used in the 12 Vdc build - I didn't take pictures of the unboxing of those, but these are the exact same model cells - I bought 80 of them for personal use at the time...

Ladies and gentlemen, I am happy to report that while I didn't get around to unloading the appliances from the minivan until this evening (wife and I were both zonked from the trip back), and had left it running both the refrigerator and the freezer (which needs defrosting now, too), it was only down to 43% capacity, which leads me to believe that I didn't start the trip with it fully charged in the first place.

I also found that my small DC solar badge bit submission was flagged incomplete, and really, I can't complain, because while many of you have been following along, the volunteer review staffers probably haven't and I really need to clean up the submission, so it looks more like a step-by-step journal of the build, which should make it much easier to judge it.

To be clear, no one is questioning my results, they continue to speak for themselves, but my documentation is lacking, so I will try to assemble something more coherent and methodical in a separate thread. It doesn't mean I will abandon this thread, at least not until Eric finishes his build 😉, but I really should post a separate and clear thread of my specific build.

Remember to be kind to the volunteer staff of this freely available platform!

A note to the reviewers of my BB:  In retrospect, I realize that my submission is more than a bit messy, and as such, may be harder to follow and/or judge.  If it doesn't meet the required or desired standards, please reject it, and I'll try to come up with a cleaner presentation.

Now that I'm away from Allerton Abbey, my internet access is greatly improved, so there's likely to be much less frustration and time wasted trying to get anything to upload or post.  Sorry for the bother.

Oops... I'd started making collages of the parts pictures early on, but I forgot about them, & there have been a few changes as the project evolved.  They aged out enough to get out of view in my photo collection.

Note, some of these parts ended up failing and being replaced with better, some parts are for both this project and the "Charge and Carry" badge bit (like the USB power outlets, etc.), and some parts were either deprecated, or haven't been used yet, because they are to upgrade or augment some aspect of the system, like there are quite a few breakers that haven't been installed yet, but will be, before I quit fiddling with it...

I submitted it when I did, because it's proven to be fully functional enough to live off of, even before adding the other bells and whistles (which are mainly for my own comfort level, and aren't specifically called for in requirements), like breakers, etc., but the build really started in earnest in this thread https://permies.com/t/40/274663/Building-AH-LiFePo-Battery-Box#3766993, where I was trying to show some examples to help the others building their 100 Ah battery systems.

If required, I will sift through the photos, and try to separate the specific & exact parts that ended up in this version of the box, but it's still a bit of a work in progress, that I won't be trying to submit as a duplicate (ever again). This one will be refined, to best fit our uses for it but I still have another 24 Vdc system to complete, with an inverter.