LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[durundal]

Originally Posted by goboatingnow

Conformal coating maybe, interesting the justification for conformal coating is not really justified on basically all digital circuitry. Good gold plated boards are often better

Mounting. Personally I prefer running a fused wire to each cell and a single BMS board that can be mounted outside the battery box.

The alternative idea is a two board solution, with the analog sensing on a small board at the battery box, with a serial link to a board mounted behind the panel, hence easier to wire in indications and button to a panel

Latching relays good idea , kgtechnologies make a good line , sterlings is very dear , there are several manufacturers that provide low power operation by using magnets.

The board will have on board small signal relays to all driving a wide range of contactors/relays including a relay that operates before the contactor relays , this can used for make before break , or things like field disconnect of a alternator

Wire interface , absolutely , no Mickey Mouse wires.

Currently not proposing a display , but the system could easily drive a cheap 2x16 LCD

The board would provide outputs for the various lights ( HVC, upper limit, lower limit, LVC , imbalance ) two buttons ( alarm silence , reset contactors )

I will probably put the LEDs and buttons on the board directly and publish a panel cad to allow people to make the panels ( front panel express etc )

Dave


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I'm not an EE so my interest in the conformal coat is for a moisture/shorting barrier, it ends up being standard application for any board in a high reliability environment for that reason alone. Was its benefit in analog circuits in reducing surface charging or something?

I very much like the idea of running the wires down to the battery. Are you thinking the outputs are 5V ttl stuff or closing contactors?

Andy


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[goboatingnow]

Originally Posted by durundal

I'm not an EE so my interest in the conformal coat is for a moisture/shorting barrier, it ends up being standard application for any board in a high reliability environment for that reason alone. Was its benefit in analog circuits in reducing surface charging or something?

I very much like the idea of running the wires down to the battery. Are you thinking the outputs are 5V ttl stuff or closing contactors?

Andy


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Yes , in the past I've used CC in sensitive analog front end circuitry etc. it's benefits in a battery monitor are much less well defined. It's easy enough to add spray on conformal coating. Bit I'm not sure it adds much on this instance over a quality gold tinned board and high quality silk screen. It can sometimes help against salt buildup, but digital circuitry is not as easily disrupted by small, leakage currents the way sensitive analog systems.

I'm open minded though

What I'm now thinking of is a two board solution, one board carries the lights, optional 2x16 char LCD ,button etc. the other board mounts in or near batteries, is wired to the cells and contains the small signal relays that can be used to drive various power relays, contactors, or latching/low power relays. The two boards communicate over a serial link. ( RJ11 telephone cable, which includes power )

The system would use user supplied power relays or contactors as these have to sized for the charging and load systems of the boat

I was thinking of making the LVC system NO relays. Ie the relays drop out open , but it means the contactors are powered on all the time. But it provides a fail safe. HVC would be NC

It will be a open source hardware, and software project. So people can add or modify the system easily

Dave


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[campr]

It would also be nice if a way of measuring SOC were available, by current consumption/charge. I.e. a MV measurer (shunt) or a hall-sensor attachment.

It would also be nice if it could measure 8 cells, not just 4. You might just need a larger atmel for that.

Logging on SD card would also be desirable, with an adjustable time-interval.

All relatively easy on an arduino mega as a prototyping platform?

Robert

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[goboatingnow]

Originally Posted by campr

It would also be nice if a way of measuring SOC were available, by current consumption/charge. I.e. a MV measurer (shunt) or a hall-sensor attachment.

It would also be nice if it could measure 8 cells, not just 4. You might just need a larger atmel for that.

Logging on SD card would also be desirable, with an adjustable time-interval.

All relatively easy on an arduino mega as a prototyping platform?

Robert

Sent from my Nexus 7 using Cruisers Sailing Forum mobile app

I think in relation to BMS, this strays into battery measurement. SoC on lithiums can be very tricky especially on large Ah capacity as the curve is almost flat. But unlike LA, voltage is a good indicator of SoC, but you can be measuring very small voltage changes.

6 cells , actually I was looking at 24 voltage systems by daisy chaining the measuring boards together.

Logging , I again think a serial or USB output to a pc might be a better option.

Ardunio is fine for a prototype but in no way is it useful as a final useful product (Way too electrical fragile )

Since I develop using these systems I have a host of CAD based designs, so its easy to pull out a circuit ( and I have stacks of suitable prototypes )

Dave

[msmith132]

This is a FABULOUS thread, and I want to express my thanks to the numerous knowledgeable contributors here who are obviously contributing a lot of their time for our benefit. Over the past month I have read this entire thread and am about to order all of the necessary goodies to convert my Lagoon 421 to lithium while situated in Grenada, so I am trying to ensure that I capture all of my needs in one US shipment. This leads to a couple of questions with which I'm hoping you folks can help me.

First, some background info. I am planning to install 12 v X 560 AH using 12 CALB 180 AH cells 3P4S. My charging sources are 2 Hitachi 80 amp alternators (never used for charging, incidental charging only while entering or leaving anchorages), 400 watts of solar with ProStar 30 PWM controller, and 2 X 40 amp Cristec battery chargers supplied with 220 VAC via generator (my primary charging source for whatever solar can't provide).

Xantrex ProLink already installed. I will be installing the HPBMS, am getting a Celllogger, and am planning to leave the AGM start batteries in the circuit to protect the alternators. I will also install manual switches on the alternators (via MaineSail's method explained earlier) for those rare periods of prolonged motoring. I will top balance.

Is it acceptable to use only one HVC contactor in the charge bus to interrupt all charge sources instead of placing one on each charge source? (Separate load bus) I can't imagine why I would want the HVE to only disconnect one source, and multiple contactors add failure points.

My house load is about 200 AH/day which means I will only need the genset every 2-3 days to charge. My question is in regards to the solar panels charging the house bank on the non genset days...do these mini-cycles adversely affect cell life expectancy? I would hate to give up the 100 AH charge that this contributes on those days.

Relays are not one of my strong suits, so im looking for any recommendations on which relays to use for HVC and LVC? Can these be the same model of relay for both applications to reduce my spares requirement, or is there some difference in the application requiring different relays?

I am getting the impression from my various readings that cell compression is not required in this fractional C configuration, is this correct? I'm not positive that my impression is correct, so I want to double check here. I'd really be kicking myself if I destroyed these batteries through my poor interpretation of information sources.

Following installation and commissioning, my next step will be to add to my genset charging capacity (another 75-100 amps), primarily focused at reducing my genset run time and increasing its load.

All input or suggestions would be greatly appreciated.

[goboatingnow]

Cell compression ? , do you mean cell balancing

Dave


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[msmith132]

By cell compression, I meant having the cells contained between rigid plates to prevent expansion. Sorry for the lack of clarity.

[goboatingnow]

Originally Posted by msmith132

By cell compression, I meant having the cells contained between rigid plates to prevent expansion. Sorry for the lack of clarity.

Large format lithiums benefit from mechanical rigidity, I and others re commend strapping etc.

Dave


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[dlentz]

Originally Posted by msmith132

By cell compression, I meant having the cells contained between rigid plates to prevent expansion. Sorry for the lack of clarity.

Just to be a contrarian, It has not been shown that strapping/compression is necessary in a house bank used/charged at fractional C. That being said strapping/compression will not hurt and in the case of an overcharge or very high C environments it might reduce some damage and preserve some capacity. It has also been shown that bulged cells have recovered some of their capacity by compressing them after an "event".

However, I think most consider it "best practice" to strap them and my bank is compressed in an Aluminum box which also isolates the cells.
Dwain

[Singleprop]

I think that it is advisable to use a strap around the batteries since it reduces the movements of the cells and therefore reduces the strain on the battery straps and posts, please read this article, page 8 http://media3.ev-tv.me/cellcare.pdf.

[roetter]

Quote:
...

Is it acceptable to use only one HVC contactor in the charge bus to interrupt all charge sources instead of placing one on each charge source? (Separate load bus) I can't imagine why I would want the HVE to only disconnect one source, and multiple contactors add failure points.
......



---I used one Blue Sea Solenoid for the load bus and one for the charge bus on 3 boats I installed LiFePo so far.

....
My house load is about 200 AH/day which means I will only need the genset every 2-3 days to charge. My question is in regards to the solar panels charging the house bank on the non genset days...do these mini-cycles adversely affect cell life expectancy? I would hate to give up the 100 AH charge that this contributes on those days.

.......

--- just stay away from high voltages and you are fine. There is research showing that all electrode plating occurs at the very top end. Do not charge over 13.8V. High temperatures are bad too. Do not install in the engine room.


......
Relays are not one of my strong suits, so im looking for any recommendations on which relays to use for HVC and LVC? Can these be the same model of relay for both applications to reduce my spares requirement, or is there some difference in the application requiring different relays?

.......

--- yes the same models for both solenoids

......
I am getting the impression from my various readings that cell compression is not required in this fractional C configuration, is this correct? I'm not positive that my impression is correct, so I want to double check here. I'd really be kicking myself if I destroyed these batteries through my poor interpretation of information sources.

.....

---- The CEO of Balqon told me strapping is not required.


....
Following installation and commissioning, my next step will be to add to my genset charging capacity (another 75-100 amps), primarily focused at reducing my genset run time and increasing its load.

.......

---- I guess you are planning to add another charger to the Cristec. I installed LiFEPo recently on a friends L450. His boat is in Grenada. He has a generator and uses the regular Cristec and a Victron Multi 3000 inverter/charger. He uses both for charging to load the generator better on a 1400Ah LiFEPo install. Works great.

The Cristec charger is connected to the charge bus and will be disconnected when over 13.8 V. It continues to charge the starter batteries.

The Victron is on the load bus. We reprogrammed it to 13.8V and 13.3V for the float.

BTW the Victron is connected to the shore power connector. This is a 220V boat from Europe. The Cristec has been removed from the boat's power circuit and is on its own. It can be used to be plugged into any voltage and frequency in the world separately. When the Cristec is plugged into 110V shore power then the inverter has to drive all the 220V on board.

I have 1800W on my own L450 and do not own a generator and we use oodles of power, definitely much more than 200Ah. Wife has just started the washing machine. Yesterday we ran the water maker for 5 hours. We have 3 fridges, cappuccino maker, counter top ice maker, toaster, microwave. We are always good with just the solar, even in winter in the Bahamas. The solar install was about $3500. In the summer I could run AC (which I don't have) for the night and still have enough without a generator.

The L450 in Grenada has my previous solar install of 950W.



Rolf

[sparrowhawk1]

Rolf. NICE set up. How was the cristec charger disconnected from the charge bus?

[roetter]

Originally Posted by sparrowhawk1

Rolf. NICE set up. How was the cristec charger disconnected from the charge bus?

Please see the screen capture of my install schematics below. The Cristec house output was disconnected from the battery - after the manual battery positve switch - and connected to the charge busbar.

Attachment 84229

[sparrowhawk1]

Roetter. Thank you

[ColdEH]

Originally Posted by Maine Sail

Dave,

I have a few items:

*HTC - High Temperature Cut Individual cell temp monitors for each cell.

*LTCC - Low temp CHARGING cut. Loads still allowed but no charging. Same monitors but no charging allowed below 0C/32F..

*I would also prefer a device that can drive latching relays such as the Blue Sea 7712 etc..

*Can incorporate charge HVC / Load LVC cuts at a warning level and emergency level.

*Can have LVC and HVC levels adjustable as well as hysteresis on warning level

*user configurable warning and emergency level outputs selectable normally closed or normally open (gives more options when choosing relays & contactors)

*Any balancing must be done manually and preferably "attended" just like equalization charging. A manual override of warning level HVC would be required to drive the bank to shunting levels.

I know I have more and will think of them the minute I am away from the computer.....

Hey Main Sail

Been watching for your new article on LIFePo4 . Looking forward to it .

Always great work!

Regards