Lithium Batteries, who has them?

[T1 Terry]

For any interested in the dedicated 80a lifepo4 solar charger I've been testing, forget it, it was a total failure and couldn’t handle the input without stuffing up and over heating. I'm now testing 60ah controllers in parallel and so far it is functioning well on 2kw of panels. In the next few weeks will have 4 x 40ah controllers which will test in parallel to find out whether the 60a or 40a works the best.

Very interesting exercise, seems large ah controller can't handle constant bulk charge and actually only ever get to their stated capacity for very short periods, They are also much more susceptible to temperature variances and on hot days get very hot and have only about 50-70% input. Smaller controllers in parallel overcome this problem I've found and do operate very well when only using 70-85% of the input capacity. Which could mean your charge controller should not work any harder for any length of time at full capacity when used with lifepo4 you have lifepo54 charge parameters

This is exactly what I have been saying for yrs now, the heat generated by the MPPT function is far greater than that generated by a PWM controller so the losses to heat require additional cooling that also uses even more of the harnessed energy, the end result is a lower output via MPPT than by PWM over the full day. What would be interesting is a either a wetback cooling plate or a Peltier effect module to a fan cooled or wetback plate to control the temperature run away. The wetback idea would at least harness some of the wasted solar energy and use it for heating the shower.

[T1 Terry]

I am interested in your research Pepper, as my "Fangpusun" Chinese knock off of a Flexmax Outback 80 is definitely not doing the business. My 600AH LiFePO4 battery was at 493AH remaining yesterday with full sun on the 1080w x 24v panels and the controller was 'snoozing" and not putting out any charge current. Even running the microwave for a couple of minutes did not trigger the unit back into bulk charge mode. I have been considering installing a pair of eTracer 45Amp MPPT units. These appear to have a reasonable reputation and have fully customisable charge protocols. Anyone had experience with these?

Cheers Chris

Add a switch into the solar input, off for a few mins will trick the unit into believing it is a new day and return to the bulk charge mode. This is a common MPPT controller problem as they are designed for lead acid batteries, they need to see less than 12.6v to believe the battery is any less than fully charged, that is very close to fully discharged for an Li battery.
A lot of people have been caught by these knock off Outback power MX80 copies, the outside looks similar but the internals aren't even close to the real thing.... and how could they be at the price they are selling them for??? The Outback MX80 is expensive but that is because there is a lot of very expensive gear inside that big box...... how anyone could believe that a unit any smaller could do the same job is beyond me

T1 Terry

[native pepper]

What voltage are you at @pepper? 12 or 24??

We tried them on 12 and 24v, it made little difference, but 24v did last longer. We are now trying 40a controllers in parallel to see how they handle lifepo4, an 80a PWM controller we tried worked, but it produced way less input than the MPPT and here in Tas, that makes a huge difference in winter. Now we are testing 2x40a MPPT with the same parameters and so far after 2 weeks not a problem, the cell balancers haven't started working, and the input seems very smooth, Using the 80a, near midday, the pack filled rapidly and cells went over 4v before the balancers could cut in properly. That has yet to happen with the 2x 40a controllers, but it is early days and things may change.

Another thing I've learnt with lifepo4, we've had a very cold winter so far, many morning well below zero and days hanging round 8-10deg. I have lifepo4 starters in our cars and about to put them in the earth mover and tractor, they are wonderful, but have a bug when it is very cold and you try to start the car, you get virtually nothing and the volt meter says they are at 12v. After many experiments, have worked out you have to put a short term high load on the battery for a few seconds and then it provides all you need instantly and the voltage instantly goes to 13.8-14.2v depending on temp So starting on very cold mornings, involves switching on the ignition and radio. turning the key for a second them letting it sit for 5 second, then doing it again and bingo it fires like the engine is warm. Different with the bus and house packs, as they have a constant draw and seem unaffected by the cool temps.

[native pepper]

I am interested in your research Pepper, as my "Fangpusun" Chinese knock off of a Flexmax Outback 80 is definitely not doing the business. My 600AH LiFePO4 battery was at 493AH remaining yesterday with full sun on the 1080w x 24v panels and the controller was 'snoozing" and not putting out any charge current. Even running the microwave for a couple of minutes did not trigger the unit back into bulk charge mode. I have been considering installing a pair of eTracer 45Amp MPPT units. These appear to have a reasonable reputation and have fully customisable charge protocols. Anyone had experience with these?

Cheers Chris

G'day Chris, know how you feel, we've tried many different off shelf controllers, big brand and low cost Chinese. Yet none came up to scratch for lifepo4, so they decided to source a dedicated lifepo4 controller themselves and to my knowledge have been hunting for the right one for the last 2 years. Now they have a manufacturer who understands the situation and is keen to produce what is needed for lifepo4 and that's where I am getting my test units from. I know they approached major non Chinese manufacturers, but they were not interested and told them their controllers were suitable for lifepo4 with the LA parameters of float etc and LA high and low settings. To me that smells like wanting to establish a Lead acid mentality for lifepo4, so they can lower the lifespan, increase their turn over by lowering life spans of lifepo4 packs and LA controllers will certainly do that.

Alga

[nut17]

Thanks for the update Alga. I will persist with my existing controller for the time being (Terry's suggestion to disconnect the power from the panels then re connect seems to work) so I can wait for further developments. These http://www.trademe.co.nz/Browse/Listing ... ermanent=0 controllers are well priced and supposedly can be set to suit LiFePO4 so maybe a pair of these will do the job OK?

Cheers Chris

[native pepper]

Thanks for the update Alga. I will persist with my existing controller for the time being (Terry's suggestion to disconnect the power from the panels then re connect seems to work) so I can wait for further developments. These http://www.trademe.co.nz/Browse/Listing ... ermanent=0 controllers are well priced and supposedly can be set to suit LiFePO4 so maybe a pair of these will do the job OK?

Cheers Chris

I'm no expert Chris, in fact not that technically minded. But looking at your link it seems they are unsatisfactory for lifepo4, there is no indication of upper limit cut off, lower cut off is well below 12v and a 4 stage charger is not good for lifepo4, all we need is bulk.

Of course you could contact them and see what they say about them for lifepo4 charging and work it out from there. Could be wrong, but most say their chargers are fine for lifepo4, yet have just L/A charge regimes and parameters. Finding a charger or controller which caters for lifepo4 exclusively is very hard, that's why my friends have gone to the trouble they have to source them.

I really get sick of having to watch my lifepo4 packs to keep them in line, the relays I currently use to control charge and discharge, are just more things to go wrong. So I like most I talk to, want a stand alone all inclusive charge controller so we don't have to keep looking at our systems constantly. If the controller I'm testing does the job, that will be half the way there.

Alga

[nut17]

I did ask the question, as they are advertised as being suitable for LiFePO4 chemistry, and the comment was that the output voltages are all able to be customised to suit battery manufacturers specifications. I am unaware of any other manufacturer who can offer any controller more suited.

Cheers Chris

[kiwipaul]

I'm just using a PWM type; I can say that I was out of the country for @ 3 weeks the solar connected to the batteries & them to the fridge. I considered disconnecting the battery but being a believer of "it should run automatically" I left they system fully connected (without the HWS working). There is a thought that dropping the cell voltage to @ 40% range then leaving disconnected is the "best" storage method (like how they are supplied).
Back here & the fridge ice blocks are still blocks, the battery voltage is still 13.6V and (at this stage) believe they are fine but I'm not conducting a deep discharge test.

[T1 Terry]

Thanks for the update Alga. I will persist with my existing controller for the time being (Terry's suggestion to disconnect the power from the panels then re connect seems to work) so I can wait for further developments. These http://www.trademe.co.nz/Browse/Listing ... ermanent=0 controllers are well priced and supposedly can be set to suit LiFePO4 so maybe a pair of these will do the job OK?

Cheers Chris

This is an MPPT controller, unless they have internal linking capability that makes one unit the control and the other units slaves you can only have 1 on a battery, 2 unlinked units will see each others input as battery voltage and adjust their charging regime to suit. Unless the back to boost is fully adjustable for both time and voltage you will be no off better than you have now. What if I build you a secondary control unit that will shut the supply off to the controller you have if a cell goes high voltage so you can reset the float voltage higher to ensure the battery remains fully charged without damaging the battery. This will reset the controller each time and get around the non return to boost problem without holding the cells a damaging high voltage.

T1 Terry

T1 Terry

[bagmaker]

What voltage are you at @pepper? 12 or 24??

We tried them on 12 and 24v, it made little difference, but 24v did last longer. We are now trying 40a controllers in parallel to see how they handle lifepo4, an 80a PWM controller we tried worked, but it produced way less input than the MPPT and here in Tas, that makes a huge difference in winter. Now we are testing 2x40a MPPT with the same parameters and so far after 2 weeks not a problem, the cell balancers haven't started working, and the input seems very smooth, Using the 80a, near midday, the pack filled rapidly and cells went over 4v before the balancers could cut in properly. That has yet to happen with the 2x 40a controllers, but it is early days and things may change.

Another thing I've learnt with lifepo4, we've had a very cold winter so far, many morning well below zero and days hanging round 8-10deg. I have lifepo4 starters in our cars and about to put them in the earth mover and tractor, they are wonderful, but have a bug when it is very cold and you try to start the car, you get virtually nothing and the volt meter says they are at 12v. After many experiments, have worked out you have to put a short term high load on the battery for a few seconds and then it provides all you need instantly and the voltage instantly goes to 13.8-14.2v depending on temp So starting on very cold mornings, involves switching on the ignition and radio. turning the key for a second them letting it sit for 5 second, then doing it again and bingo it fires like the engine is warm. Different with the bus and house packs, as they have a constant draw and seem unaffected by the cool temps.

Aircraft usually have a heating system to keep the battery warm.
http://www.lange-aviation.com/htm/engli ... ystem.html
It would be a simple enough exercise to sit them on a pad heater used for aquariums or homebrew.