AC battery charger for AGM start battery and Lithium bank

[swampbush]

I am starting to think about Lithium and will need a new charger. Enerdrive make one that does lithium as one profile and 2 other banks with different charging. Lithium profile stops charging and turns on once a week to top up All settings seem adjustable. It suits 120 and 240v which is handy as my boat is both. Thoughts on suitability?

http://www.enerdrive.com.au/product/...ttery-charger/

A google search brings up the manual, but I can't find a link on the web page.
https://www.google.com.au/url?sa=t&s...JxeM6Frnp4nCWy

[john61ct]

Lithium should for good longevity be kept at as low as possible a SoC level while not in active use cycling.

But not so low as to be allowed to go dead flat, which instantly and permanently destroys them.

I have yet to see an OTS unit that would accomplish this automatically.

[OceanPlanet]

Originally Posted by john61ct

Lithium should for good longevity be kept at as low as possible a SoC level while not in active use cycling.

But not so low as to be allowed to go dead flat, which instantly and permanently destroys them.

I have yet to see an OTS unit that would accomplish this automatically.

Interesting concept...a long-term charging/load/monitor maintenance config that would do a monthly short balancing charge, then discharge to the low SOC.

Ideally the system would also do an occasional automatic capacity test and update itself...;-)

[CatNewBee]

Originally Posted by OceanPlanet

Interesting concept...a long-term charging/load/monitor maintenance config that would do a monthly short balancing charge, then discharge to the low SOC.

Ideally the system would also do an occasional automatic capacity test and update itself...;-)

Or simply just float at 12.4V. Cell voltage at 3.1 translates to 40% SOC (below 2.8V the cell dies, 3.65V the cell is full are the parameters for yellow Winston prismatic cells LiFeYPO4)

You then need a BMS that actively balances cells if difference is bigger than accepted threshold independent of SOC, mst cheap BMS only balance while charging above 90% SOC on the upper end.

[OceanPlanet]

Originally Posted by CatNewBee

Or simply just float at 12.4V. Cell voltage at 3.1 translates to 40% SOC (below 2.8V the cell dies, 3.65V the cell is full are the parameters for yellow Winston prismatic cells LiFeYPO4)

That's a good simple solution. Although after a long storage period without any balancing, would need to be careful on the first full charge as some cells would top up much faster than others.

Also, not sure how many marine chargers would have a float setting as low as 12.4. Perhaps there are...but never tried that low.

[john61ct]

Originally Posted by OceanPlanet

Interesting concept...a long-term charging/load/monitor maintenance config that would do a monthly short balancing charge, then discharge to the low SOC.

Ideally the system would also do an occasional automatic capacity test and update itself...;-)

Arduino or PLC based, probably would not even be that difficult for a geeky maker.

Open source would be ideal of course.

[john61ct]

Pretty sure even at whatever low voltage and current, constant "pressure" from float charging would not be optimum for longevity.

Lowest practical SoC is better than 30-40%.

Complete isolation at low temps is ideal.

[OceanPlanet]

Originally Posted by john61ct

Pretty sure even at whatever low voltage and current, constant "pressure" from float charging would not be optimum for longevity.

Lowest practical SoC is better than 30-40%.

Complete isolation at low temps is ideal.

Yes! Low SoC + low temps would be ideal.

[exMaggieDrum]

Originally Posted by CatNewBee

If you really love your LFP - GET A GOOD BMS AND LET IT DO ITS MAGIC INCLUDING BALANCING. Gurus are a good thing for believers. There is soo much nonsense in the forums about manual managing LFP. Just dont do it!

You can manually pump your bilge, but you hopefully have a automatic switch that drains it if necessary. You can manually control life values like oxygen, pulse etc, but in an ER they are monitored by computers.

You drop a significant amount of money for your cells, spend some 10..20% for a good BMS and bi-stable solenoids - like the BlueSea ML-RBS. This is a rewarding one time investment. Stop saving on the wrong end.

CatNewBee, everyone is entitled to their opinions, especially if they can also provide solutions. What, specific, BMS are you using? Why did you select that one? What is the overall design of your system?



Interesting that MaineSail has decided to manually balance his cells and not through his BMS(s).



So far as doing things manually, some are better at that than others. To my knowledge there is yet to be BMS that is widely available, well tested in real boats out and about on the water, from a reputable vendor with long experience, that has all the features in one package that cruisers need, at an affordable price. If there is one I would like to know about it so I can go get it.


So far as saving money goes, that is not at the top of my priority list, as proven by all the gear I have purchased and not installed because someone else came up with something better. I would gladly buy a different BMS and other bits if it could meet my rudimentary list of requirements. I do not want to have to play electronic engineer to design and build circuits to blend the parts together.



Arduino-based, home-built, solutions are not, IMO, robust solutions. I will go ahead and install my little tiny HousePower BMS in a box I built, with solenoids I have to wire, to my amateur design, using a wide variety of parts from various vendors in the hope that, somehow, they will all magically work 100% of the time.



That is my plan, but, I will only consider that a backup for when I forget to do something or program something else in error, or the something else fails, e.g. Balmar regulator, solenoids, contactors, alarms, battery monitors, etc. All of which routinely fail. I dislike complexity, especially when complexity is created from too many vendors and too many devices. I prefer, and will use, a manual oriented management of my system.



In the meantime, I'm still waiting for the dust to settle and some robust, vendor-supported, solutions to appear. I do not want to go with the complete battery systems from Mastervolt, Victron and some others. I actually believe I can get better bang for my buck by manually managing what I have in a consistent and rigorous manner. Any device can fail and I am not inclined to put something in and then hope for the best. But even if I were a billionaire, if I bought one of these systems, I would know that I would also have to buy the technicians and spare parts to fix it as it breaks and replace my batteries along the way as part of the collateral damage.



BTW - I have a brand new Blue Sea ML-RBS in its original packaging that I bought two years ago that has never been installed because there wasn't a driver available that worked with any BMS that I could find to operate a bi-stable switch. So I am eager to see your solution. Perhaps I can use this expensive switch after all. I am not being facetious. Please share your design.

[john61ct]

Cat Newbie's LFP thread is here http://www.cruisersforum.com/forums/....php?p=2639756

[CatNewBee]

Originally Posted by john61ct

Cat Newbie's LFP thread is here http://www.cruisersforum.com/forums/....php?p=2639756

Yes it is described in detail there and in some other threads, if you miss something, feel free to ask.

It is the REC ABMS, an active balancing compact bms, totally customizeable, and the vendor offers custom programming for the signals with no additional charge according to your specs, what is awesome.

It works up to now flawless, I tested the system with all components at home for 2 month and the system is installed now on board and working for one month (LFP, BMS, Inverter/charger), solar running for 20 days now, completely off grid since then.

I cannot provide long term data yet, but it is doing what I want it to do so far, so no complains.

The developer / company is very responsive, I've got firmware updates within 4 hours to fix a issue with the 5kVA Quattro. Very impressive indeed. (it was about interferrences due to frequency of the inverter under high load and measuring the cell voltages, the sampling rate needed to be adjusted to mitigate jumping voltages based on the impulse phases.) Was a pleasure to work with them.

[svlamorocha]

Originally Posted by john61ct

And they are Dutch not German

That confusion can upset some..

[exMaggieDrum]

Originally Posted by CatNewBee

Yes it is described in detail there and in some other threads, if you miss something, feel free to ask.

It is the REC ABMS, an active balancing compact bms, totally customizeable, and the vendor offers custom programming for the signals with no additional charge according to your specs, what is awesome.

It works up to now flawless, I tested the system with all components at home for 2 month and the system is installed now on board and working for one month (LFP, BMS, Inverter/charger), solar running for 20 days now, completely off grid since then.

I cannot provide long term data yet, but it is doing what I want it to do so far, so no complains.

The developer / company is very responsive, I've got firmware updates within 4 hours to fix a issue with the 5kVA Quattro. Very impressive indeed. (it was about interferrences due to frequency of the inverter under high load and measuring the cell voltages, the sampling rate needed to be adjusted to mitigate jumping voltages based on the impulse phases.) Was a pleasure to work with them.

Thanks for passing this on. I will study it carefully. I really would like to find a better BMS solution. I can't look at it for a couple of days but will soon.

[exMaggieDrum]

I've made a quick pass over your designs and explanations. It seems complete and very elegant. I have to look at it some more. The REC ABMS looks very promising. I found a German company which ships to the US - price 299 euros plus 22 euros shipping (not sure if customs would apply but the duty/tariff situation is in flux as I write). If appears to have the basics needed.


Forgive me for being somewhat digitally challenged but I still have the question of how to drive a bi-stable latching switch, such as the ML-RBS, if the BMS outputs a steady signal (positive or to ground) (high to low?) since the ML-RBS requires a momentary pulse only and will not accept a steady input. I read the PDF on the REC and it appears to me that it is a steady output for external switching of contactors. One place it says that two outputs are "digital" but I am not clear as to what that implies.


I did find an adaptor in Australia that seems to provide a conversion from a steady input to a momentary output but the PDF for it does not explicitly say that in terms that I understand at least. The company website says it is a "REC" product but it does not appear on the REC website in Slovenia.



Mbartosch was kind enough to design a DIY circuit to do this and I bought the parts to build the small circuit board. I believe I can put this together but would much prefer an off the shelf product. A web search finds many momentaty to steady circuits and relays but none that I could find which does the reverse.



This issue is why I decided to put my ML-RBS on the "to sell in the future" shelf and go with regular high amp contactors. A latching switch is preferred, of course, because they use much less power for the on/off relay.


I have been consumed by other projects after installing my LFP batteries and am just now getting back to the BMS issue so I did not see your excellent posts on your system. Thanks for putting that out on the forum.

[CatNewBee]

Originally Posted by exMaggieDrum

I've made a quick pass over your designs and explanations. It seems complete and very elegant. I have to look at it some more. The REC ABMS looks very promising. I found a German company which ships to the US - price 299 euros plus 22 euros shipping (not sure if customs would apply but the duty/tariff situation is in flux as I write). If appears to have the basics needed.


Forgive me for being somewhat digitally challenged but I still have the question of how to drive a bi-stable latching switch, such as the ML-RBS, if the BMS outputs a steady signal (positive or to ground) (high to low?) since the ML-RBS requires a momentary pulse only and will not accept a steady input. I read the PDF on the REC and it appears to me that it is a steady output for external switching of contactors. One place it says that two outputs are "digital" but I am not clear as to what that implies.


I did find an adaptor in Australia that seems to provide a conversion from a steady input to a momentary output but the PDF for it does not explicitly say that in terms that I understand at least. The company website says it is a "REC" product but it does not appear on the REC website in Slovenia.



Mbartosch was kind enough to design a DIY circuit to do this and I bought the parts to build the small circuit board. I believe I can put this together but would much prefer an off the shelf product. A web search finds many momentaty to steady circuits and relays but none that I could find which does the reverse.



This issue is why I decided to put my ML-RBS on the "to sell in the future" shelf and go with regular high amp contactors. A latching switch is preferred, of course, because they use much less power for the on/off relay.


I have been consumed by other projects after installing my LFP batteries and am just now getting back to the BMS issue so I did not see your excellent posts on your system. Thanks for putting that out on the forum.

to make an impulse out of a steady signal on signal change from low to high a capacitor in line does the trick. to discharge on high to low I use a led with a resistor, it also shows me the current signal state.

here a picture of the interfaces i built. There are other solutions around, but this is simple, efficient, informative and low power.