LiFePO4 - The future for off-grid battery banks?

[david3]

This one might suit your needs

Thanks. It looks like their 48V model only handles 15 cells (vs. 16). And there's not much information about the individual units that would connect to the cells.

It lists a "Mosfet Switch" that can handle 270A, but "Cell Balance Current" is 0 - 1.5A.

here is some information also on ones available here in Australia. I havent used one of theirs as have made my own as mine were only need for small system,,,

http://lithbattoz.com.au/index.php?p...ry-diagnostics

Thanks. Not much in the way of product information there.

[john p]

here is some information also on ones available here in Australia. I havent used one of theirs as have made my own as mine were only need for small system,,,

http://lithbattoz.com.au/index.php?page=battery-diagnostics

Battery Management and Diagnostics
What is the difference between a Battery Management System (BMS) and the BMI Voltage Management System (VMS)?

A BMS is an electronic circuit board used in conjunction with a lithium ion battery which serves to prevent over charge, over discharge and it provides a balancing function for the cells in a battery pack. By doing this it ensures the longest life and best performance from the battery. For certain chemistries of lithium ion batteries the BMS provides a vital safety function since with over charge, over discharge and cell imbalance are conditions where certain more hazardous chemistries of lithium ion batteries could possibly catch on fire (or even explode under certain circumstances). This discussion is primarily aimed at the only safe chemistry of lithium ion i.e., Lithium Iron Phosphate (LiFePO4). BMI only manufacture safe LiFePO4 batteries. A BMS is especially important where multiple cells are used to construct a much larger battery pack. The BMS manages cell balance during charging and/or discharging as well as having the ability to disconnect the battery from the load when the batteries charge has been fully exhausted. This is very important since LiFePO4 cells can be severely (or even permanently) damaged if excessively over-discharged. Likewise a BMS should disconnect the battery from a charging source when the battery has received a complete charge so as to not become excessively overcharged since this can also lead to a reduction in the life of the battery.



A VMS and BMS both manage and provide the cell balancing function in a battery pack. This is where the similarity ends.


A VMS differs fundamentally from a BMS in that it will not disconnect a battery automatically from external devices connected to it during over-charge or over discharge conditions. It will only provide a signal output or some other visual or audible warning when approaching these conditions. This signal output is used by electric vehicle (EV) manufacturers to interface with their own external control systems in different ways. For example the signal generated by the VMS when the battery becomes fully discharged might be used to drive an external relay or contactor via suitable switching transistors. The relay contacts then disconnect the battery from its load thereby preventing further discharge which could lead to battery damage and thus maintaining long battery life. The signal outputs from the VMS can be used in many different ways and are only limited by the imagination of the EV designer.





The BMI VMS is built into the HPS series of battery packs. We do however supply the VMS in kit form for those experienced battery constructors who would like to assemble their own custom battery. The complete VMS kit includes two circuit boards, interconnecting ribbon cables, temperature sensing thermistor and wiring loom to connect the VMS board to the individual cell terminals. There is no soldering required since all wiring and sensors are terminated with connectors and simply plug into the main VMS circuit board. The second circuit board is optional since it is required only for advanced applications but is useful to have due to the warnings it provides by indicator LED's and warning buzzer. This board is a display board and has two DB9 data connectors fitted so that batteries can be monitored on a computer via an RS-232 data link. A battery data converter and software is available which interfaces the VMS with a PC. Each VMS board connects to and monitors four cells and several VMS boards can be linked together "daisy chain" fashion to accommodate any number of cells. So for example if a 36V battery was to be assembled this would require twelve cells and three VMS boards.



Please enquire if you require additional information about the BMI VMS system.

LiFePO4 Battery Balancers


Lithium Batteries Australia supplies the world's highest quality battery balancer for those who do not want to use a BMS and would prefer to balance their cells via an external balancer rather than a BMS. This balancer is the highest quality unit on the market and is very fast and accurate in its balancing ability due to its high 1.5 amps shunt current while charging. These are a very high quality unit made in an extruded aluminium case. They are made in Europe exclusively for LBA by our european partners.

Balancers are available in all the common battery voltages of 24V, 36V, and 48V. Custom units can be supplied for any quantity of cells upon special order. Please enquire if you have a special request.

mabe this be of help

I have bought cells from this company and have found them to be very good quality and their BMS appear to me to be good quality.
Their products are aimed at all markets not just the EV market.
They also make up batteries from 12 to 144 v with the BMS built in.
Their web site is not the best design and lacks detail

but if you contact them they always helpful


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[Sunking]

This one might suit your needs

[david3]

david3 you certainly are going to need a BMS or the cells are going to have an unhappy life. Easy to make for cells below 20ah but harder for ones you need for over 700ah. You should consult the manufacturer of the cells see what they recommend. I have noticed they seem a bit overpriced all of them but in the total scheme mabe not that much extra expense. But you are going to have to use one.

Yeah, there's no question about that. A BMS is required. Do you have any suggestions as to which one would be best?

David the off the shel BMS out there now are aimed at the DIY EV market, Currently there is no demand for the RE market. So you are correct the AH capacity is smaller because th eEV market is a much higher voltage application.

From the engineering POV the RE technology or I should say the Off-Grid Battery, is really dysfunctional and make no sense operating at such low voltages. The only justification is the DIY nature of the off-grid nature and the safety factor associated with the lower voltages.

The plan would be to use a 16 cell 48V battery system. It would be great to operate at an even higher voltage, but most of the inverters available operate at 48V max.

To be safe, the BMS should be able to handle 250 amps across the whole 48V battery system, to deal with surges.

I imagine there are at least a few out there that would work, but I'm not sure which ones. It would be nice if there was a nice, neat, shrink wrapped BMS for this sort of application. And if I could dream, it could even come in a case.

[Sunking]

David the off the shel BMS out there now are aimed at the DIY EV market, Currently there is no demand for the RE market. So you are correct the AH capacity is smaller because th eEV market is a much higher voltage application.

From the engineering POV the RE technology or I should say the Off-Grid Battery, is really dysfunctional and make no sense operating at such low voltages. The only justification is the DIY nature of the off-grid nature and the safety factor associated with the lower voltages.

[john p]

david3 you certainly are going to need a BMS or the cells are going to have an unhappy life. Easy to make for cells below 20ah but harder for ones you need for over 700ah. You should consult the manufacturer of the cells see what they recommend. I have noticed they seem a bit overpriced all of them but in the total scheme mabe not that much extra expense. But you are going to have to use one.

[Sunking]

Are you talking about controllers??

No he is talking about a BMS

[SteveC]

Are you talking about controllers?? I have an 1875 amp hr. bank charged by a 2000 w. array [12 v. battery] and use two Outback MX60s [now they sell the newer FM 60]. Works great. There are a number of similar controllers out there. The array and bank have been working for many years, no problem.

Is this what you're asking about??

[david3]

Any idea which battery management system to use if you were to get a set of large AH batteries for a solar-electric system? Like 400AH or 700AH cells (x16)?

While there are lots of battery management systems out there, details on them are often sketchy. And many seem to be for smaller batteries.

[Mike90250]

Lets not pull this LiFePO4 thread off into Pb vs NiFe.... please.

[Sunking]

There is an incorrect figure below

No I am correct and you know it. Even your own website you use to promote your products verifies my claim

Top end 10 year Lead Acid batteries cost $0.14/Kwh
From your own website cost for NiFe $1.60 to $6.0/wh.

Ian you can argue all you want, but the facts are facts NiFe cost are 11 to 47 times higher.

[isoutar]

price comparison of lead acid to nickel iron is only about 3 to 4 times

There is an incorrect figure below ... nickel iron batteries cost about 3 to 4 times more than the highest quality industrial single cell lead acid batteries.

For a number of decades now the price differential has been 3 to 4 times (not 10 to 40 as indicated in the post quoted below).

Ian Soutar
Vancouver Isalnd
BC Canada

Right, who in their right mind will pay 10 to 40 times more for a battery, and has to add 40% more solar panel wattage to make up for their lousy charge efficiency. Edison did not renew his patent, and Exide quit making them in 1974 for a reason.

[livesley]

i personly havent looked any more into the batteries

after doing a bit of tweeking with my system its doing extremly well capabilertys of 10,000wh 200ah . ive moved my panels (15 X 80w 21volts max each) to slightly due east 35 degrees angle fixed manly set for the winter 3 banks of 5 putting out 105volts on each bank bigger cables running through a mppt tristar feeding my 48v bank of 16 x Yuasa EN160-6 VRLA Batteries feeding my new studer aj400 inverter for general running (studer great bit of kit low consuption amazing 1000w serge cerpacity) & an old 6000w ups for bigger stuff washing machine etc linked up to my lister 6kva generator to charge my batteries (only run the generator for about 100hous total in winter used about 12 liters of diesel) all in a sound proof box half under ground o & my wind turbine has had a blade up grade now its doing a bit better need to get my other tristar linked up to see what thats doing.but now ive got electric to burn welders been goin large power tools & still fully charge at the end of the day . the mppt tristar is great just go on the laptop to check every thing trying to get it on a web page for any one to see all in all

[Arctic Donkey]

steveg,

Any particular reason you went with Seiden over others like Winston or CALB?

Not a lot of time has passed since you posted the information about your setup, but any new updates would be appreciated.

[Sunking]

Hey everyone, I have been reading your post about these alternative battery systems.

There is another option that you must consider - Nickel Iron.

If you take into consideration the future replacement costs of any other battery system, then paying a little more up front is really worth it.

Right, who in their right mind will pay 10 to 40 times more for a battery, and has to add 40% more solar panel wattage to make up for their lousy charge efficiency. Edison did not renew his patent, and Exide quit making them in 1974 for a reason.