Low Budget Lifepo4 Experiences anyone?

[250224]

Originally Posted by donradcliffe

I have been living [snip]

Many thanks, interesting post!

A question: would it be possible to mention product details? When searching for a good setup it is interesting to know what others use, e.g. what do you mean with "My $115 BMS", "600w inverter" etc. (Just a remark in case you should have the details ready. And I don't address you specifically, it's meant in general when devices are mentioned: please add details, links, exact product names if you can, it is valuable! -- thanks).

[kenbo]

I have a similar system made from blue case aluminum cells and it works great but...

I bought A-grade cells in 100ah format for about 50USD. My battery is 300ah so 12 cells in 3p4s, about 600USD. A bit more money but the cells are perfectly matched. In the video you included you can see the presenter has one cell that is drifting from the other 3, that's bad and the imbalance will only get worse as the battery cycles.

Those smart Daly BMSs are all common port. What that means is if the battery goes out of parameter on discharge you cannot charge the battery without manual intervention.

The Daly BMS's balancing function is done through small (<50mOhm) resistors so your cells need to be able to stay in close balance. B-grade cells often have mismatched internal resistance.

I have a DGJBD BMS, it's 150a and was about 85USD with a Bluetooth module. It's similar to Daly in that the current goes through the BMS and it's a common port as well. But the difference is that the internal circuitry switches the discharge and charge current independently so no manual intervention.

[newhaul]

Originally Posted by kenbo

I have a similar system made from blue case aluminum cells and it works great but...

I bought A-grade cells in 100ah format for about 50USD. My battery is 300ah so 12 cells in 3p4s, about 600USD. A bit more money but the cells are perfectly matched. In the video you included you can see the presenter has one cell that is drifting from the other 3, that's bad and the imbalance will only get worse as the battery cycles.

Those smart Daly BMSs are all common port. What that means is if the battery goes out of parameter on discharge you cannot charge the battery without manual intervention.

The Daly BMS's balancing function is done through small (<50mOhm) resistors so your cells need to be able to stay in close balance. B-grade cells often have mismatched internal resistance.

I have a DGJBD BMS, it's 150a and was about 85USD with a Bluetooth module. It's similar to Daly in that the current goes through the BMS and it's a common port as well. But the difference is that the internal circuitry switches the discharge and charge current independently so no manual intervention.

What do you mean by manual intervention? My Daly does it all I don't have to do anything .

[kenbo]

Originally Posted by newhaul

What do you mean by manual intervention? My Daly does it all I don't have to do anything .

Has the BMS ever shut down because of over or undercharge at pack or cell level?

[newhaul]

Originally Posted by kenbo

Have the BMS ever shut down because of over or undercharge at pack or cell level?

Only one time and that wax in testing and it auto reset
The purpose of the test was to see if it did what it was supposed to do and it did great.

[kenbo]

Originally Posted by newhaul

Only one time and that wax in testing and it auto reset
The purpose of the test was to see if it did what it was supposed to do and it did great.

I'm not sure I understand autoreset. There is a voltage at either the cell or pack level where the BMS cuts off discharging current if any voltage goes under the Trigger value. Then reconnects when all cells rise above the Release value.

[newhaul]

Originally Posted by kenbo

I'm not sure I understand autoreset. There is a voltage at either the cell or pack level where the BMS cuts off discharging current if any voltage goes under the Trigger value. Then reconnects when all cells rise above the Release value.

Same same

[alaskanviking]

Originally Posted by tkeithlu

Can you afford a risky investment? You can be very sure of getting good Lead/acid flooded or AGM batteries, with warranties. You might score on these Li/ions, but if you don't, you are out money that you had budgeted for batteries. Personally, I wouldn't do that unless I really needed the space/weight, and had the money to risk. I don't have the need part, so I've stayed with flooded batteries, using the forum recommended Duracells from Sam's Club US.

There are a lot of people testing these right now. A lot of forums and videos. I don't believe everything I hear/see on the internet but I feel there is enough content available to really reduce the risk.

I was thinking of just getting 4 or 8 at first to keep cost and risk low, order more if it all works out. My current house bank 4 Costco gc2 6v gelcells lasted 7 years, they're toast right now but at least holding enough of a min voltage that they will run pumps and lights at the pier with the charger. Doing a lot of work at the moment so not going anywhere for a bit. Perfect time to wait a month or two for batteries. 4 are @ ~$450 with free shipping. That's what new 6v will cost me local. Cheap considering normal boat stuff, and if risk pays off more like doubling my current capacity.

From what I seen from others, these are pretty good quality. I'm less worried about the risk as the possible long shipping time. Stuff can happen in shipping, and I prefer having a tracking number.

[newhaul]

Originally Posted by alaskanviking

There are a lot of people testing these right now. A lot of forums and videos. I don't believe everything I hear/see on the internet but I feel there is enough content available to really reduce the risk.

I was thinking of just getting 4 or 8 at first to keep cost and risk low, order more if it all works out. My current house bank 4 Costco gc2 6v gelcells lasted 7 years, they're toast right now but at least holding enough of a min voltage that they will run pumps and lights at the pier with the charger. Doing a lot of work at the moment so not going anywhere for a bit. Perfect time to wait a month or two for batteries. 4 are @ ~$450 with free shipping. That's what new 6v will cost me local. Cheap considering normal boat stuff, and if risk pays off more like doubling my current capacity.

From what I seen from others, these are pretty good quality. I'm less worried about the risk as the possible long shipping time. Stuff can happen in shipping, and I prefer having a tracking number.

Not to mention the 3,000 to 5,000 warranty life cycle . And with lower C rate charging .5C or a bit lower the estimate is as high as 10,000 cycles. That's a few years worth of daily use the lower end of 3k is 10 years and with the 10k that's 30 years so somewhere between 10 and 30 years expected life I like that .

[newhaul]

Originally Posted by tkeithlu

Can you afford a risky investment? You can be very sure of getting good Lead/acid flooded or AGM batteries, with warranties. You might score on these Li/ions, but if you don't, you are out money that you had budgeted for batteries. Personally, I wouldn't do that unless I really needed the space/weight, and had the money to risk. I don't have the need part, so I've stayed with flooded batteries, using the forum recommended Duracells from Sam's Club US.

So no lfp and no desire to use them ?

[alaskanviking]

Originally Posted by newhaul

For larger banks the bms doesn't care but if you are going to run large inverters you should get the bms that has the ability of handling the amperage you might draw .

Personally I like the Daly bms they are robust and most important for us water proof

The Daly BMS is the ones I was looking at. Decent price seems to work without issue, and cheap enough to grab a spare or 2. I believe the BMS inside of battle born and the like are similar.

Of course the victim BMS won't work with raw cells. But REC BMS works with victron. They're $700 a pop though. There are a couple others but also expensive. Not 100% what they will pass to the victron bus/nmea2k that I couldn't do with a Daly BMS and a Victon smart shunt or the Venus/colorGX and Thier kin.

[alaskanviking]

Originally Posted by donradcliffe

I have been living full time in my Mercedes diesel based RV using a 200ah set of LifePo4 cells salvaged from another RV that had a disastrous BMS (it drew 3 amps). I have 400w of solar and a genset besides the 160 amp main engine alternator. After a year, I am also convinced the LifePo4 cells are a game changer because they have very little voltage sag and you only need to put back 105% of the energy you take out, vs 125% with lead acid.

A lot depends on your electrical load and charging systems. My load is minimal, because I have a propane powered refrigerator and all LED lights. In fact, I leave my 117 dollar 600w inverter on 24/7 to power laptops, CPAP, and 3 TVs just because I can. My $115 BMS is rated at 120 amps, which means that if I want to run the microwave, I turn on the genset. I also added an active cell balancer for $10. The house battery is has a combining relay with the AGM starter battery which only connects them when the main engine is running. I have set my $140 MPPT solar controller to 13.8v bulk charge and 13.6 volts float, and I bought a $25 Life plugin to my shore power charger which will maintain the battery at 13.4 volts or bulk charge it at 14.5 volts when I run the genset or am plugged in. The only concern I currently have is that the main engine alternator may overcharge the battery a bit on long runs, because it is regulated at 14.1 volts. The alternator charges 65 amps into the house battery when it is low, which I have limited by putting a 12 ft piece of #6 wire into the circuit as a current limiting resistor.

I chose the BMS and inverter on the basis of cost vs function, Not only do they cost less, they have lower parasitic losses. When the RV sits unplugged, it consumes 0.2KwH (15 ah) per day with the inverter and refrigerator off, versus 0.4 KwH/day with them on. The BMS does not have the power to start a diesel, even though the cells do. If the start battery is to weak to roll the main diesel, I can force the combiner on to charge it enough from the solar/generator/house battery in less than 15 minutes.

All has been going well for a year with only about 10% of my time on shore power, and I just load tested the cells again with less than 5% capacity loss. In the event I had a significant loss in the cells, I would have replaced them with the 280 ah aluminum case cells, which are physically smaller and cheaper than lead acid. With the rate that the LifePo4 systems are improving, I expect to pay less for replacements in the future.

The alternator is the other big issue I haven't solved fully. Swapping in a better smart regulator works, but I don't want it to fry the batteries. One of the reasons I was looking for a BMS that communicates with the victron bus, so the BMS can tell the charging sources/alternator to stop and won't damage the alternator by cutting it from the battery. I have a 120amp 24v alternator. Most solutions are made for a much smaller capacity alternator.

I have found sterling power makes a 200 amp alternator to battery charger that appears to function better than a smart regulator. Not sure yet

[alaskanviking]

Originally Posted by newhaul

Not to mention the 3,000 to 5,000 warranty life cycle . And with lower C rate charging .5C or a bit lower the estimate is as high as 10,000 cycles. That's a few years worth of daily use the lower end of 3k is 10 years and with the 10k that's 30 years so somewhere between 10 and 30 years expected life I like that .

Well I suspect that ordering A's or B lithium battery's on AliExpress or its like may have a warranty, but that realistically it will be difficult to do anything about it and doubt years down the road that that specific vender will even still exist.

But that's ok and is the real risk I have to accept going this route. Worst case I only get half those cycles I'm still better off than the 6v's. I have to remove the plywood holdown/tray due to all the acid

[alaskanviking]

I was going to get some 3" pink foam board and sand or shave it's thickness slightly to match these batteries. Then cut out a bunch of battery sized blocks.

Should be the cheapest/easiest way to figure out new battery box and space fitment.

[s/v Jedi]

I recommend to only connect cells in series, so use the 280Ah cells rather than multiple smaller ones in parallel.

If you need more capacity then make multiple batteries, each with it’s own BMS. You can connect those, each with it’s own main battery switch, to the main busbar, either with both switched on, or keep one offline as a standby. Just keep an eye on charge levels, making sure they are in the green zone.

The reasons for only connecting in series: cleaner, safer, less balancing problems, less connections, redundancy if multiple batteries are made this way etc.

Also, if you need to buy new charger/inverter and are considering things like induction cooking, consider going up in voltage from 12 to 24 or even 48V. This allows double or 4x the power using the same cells without connecting them in parallel. Simply add a dc-dc converter for your 12V loads (keep 12V AGM start battery for 12V loads and keep that in float charge using the DC-DC converter)