native pepper wrote:My oh my, of course it doesn't add up, the 14v was meant to be 13v. As the top voltage setting is 14v and doubt it ever gets to that because of the charge regimes of the alternator, Using a grinder for 20 minutes would most certainly take a lot of energy out of the pack. The point was trying to make was, it still fired the car up instantly and could have turned over a V8 diesel engine probably. Compared to using a lead acid car battery of equivalent capacity, which I believe would struggle to turn the engine over after using a grinder and drill for 20+ minutes. Then again being technically challenged, I could be wrong.
A leadacid batt of the same size would do it but would need a while to recover first. Something about internal resistance
I am a bit like that nowadays
native pepper wrote:My oh my, of course it doesn't add up, the 14v was meant to be 13v. As the top voltage setting is 14v and doubt it ever gets to that because of the charge regimes of the alternator, Using a grinder for 20 minutes would most certainly take a lot of energy out of the pack. The point was trying to make was, it still fired the car up instantly and could have turned over a V8 diesel engine probably. Compared to using a lead acid car battery of equivalent capacity, which I believe would struggle to turn the engine over after using a grinder and drill for 20+ minutes. Then again being technically challenged, I could be wrong.
A leadacid batt of the same size would do it but would need a while to recover first. Something about internal resistance
I am a bit like that nowadays
Same here, but maybe for different reasons. Have used lead acid a lot for running power tools over the years and in the early days, found myself unable to start the vehicle. So used to run the engine, but that comes with it's own problems and costs. Now when needing power where I can’t get an engine to at home, I'm putting together a 40ah to 120ah pack of lifepo4 at 12v or half at 24v, got a cheap ebay lifepo4 cell voltage meter and alarm for when they get down or up to their voltage settings. Just switch the charger off when the alarm goes off, or stop using it when the DOD setting goes off. Luckily no technical skill involved, just wire a few things up, I'll put it in an aluminium one and will have a good size portable mobile power pack of 12 or 24vs, which will come in handy when on the road and round home.
Had my 2 x 40ah solar chargers connected to my 120ah lifepo4 pack for the last 2 weeks and so far they are acting excellently, haven’t had to do anything about balancing. When the pack reaches 14v the charger switches off and when checking each cell, the voltages are within .1-.3v of 3.5. So far after 4 recharges from 13.6v, (using the pack to run my veggie oil centrifuge pumps and lifting winch) one cell has gone over 3.5v twice, the other two times it has been other cells and none more than 3.5.3v. When I'm satisfied will put them on the bus and then get the house system running on them. May even stick with paralleling 40amp chargers instead of trying 60amp ones, as they are working so well.
Looks like I'll be getting a dedicated 20-40amp mains charger with lifepo4 settings in the next month or so, asked about it and was told it's in the pipe line. So looks like dedicated solar and mains charge controller specifically designed for lifepo4 will soon be readily available, for a reasonable price and will work as claimed. Unlike the expensive claims advertised, yet still have lead acid settings and parameters, been told they may be sold on ebay to the general public which would be good.
native pepper wrote:Had my 2 x 40ah solar chargers connected to my 120ah lifepo4 pack for the last 2 weeks and so far they are acting excellently, haven’t had to do anything about balancing. When the pack reaches 14v the charger switches off and when checking each cell, the voltages are within .1-.3v of 3.5. So far after 4 recharges from 13.6v, (using the pack to run my veggie oil centrifuge pumps and lifting winch) one cell has gone over 3.5v twice, the other two times it has been other cells and none more than 3.5.3v. When I'm satisfied will put them on the bus and then get the house system running on them. May even stick with paralleling 40amp chargers instead of trying 60amp ones, as they are working so well.
Looks like I'll be getting a dedicated 20-40amp mains charger with lifepo4 settings in the next month or so, asked about it and was told it's in the pipe line. So looks like dedicated solar and mains charge controller specifically designed for lifepo4 will soon be readily available, for a reasonable price and will work as claimed. Unlike the expensive claims advertised, yet still have lead acid settings and parameters, been told they may be sold on ebay to the general public which would be good.
I'm guessing that should read 12.6v, sounds like the cells are well balanced.... and possibly the charger reads output voltage not terminal voltage so it shuts off a bit before the full 14v is reached. A good thing even if for the wrong reasons. are the solar chargers full MPPT or are they really PWM with an MPPT feed function available? In out words, the MPPT side is set to a fixed 14v output and the PWM controls that output to maintain the 14v output voltage if needed. This would make a much better Li battery charger as a single stage charger is all that is required so the circuitry would be far simpler to design and build.
The cheapie 40 amp chargers for under $80 from evil bay do just that and are trim pot adjustable for max current and voltage, pity one of the transistors on the AC side relies on the base pate for its cooling, if spacers aren't used when mounting the charger on the carpet floor of the motorhome/caravan, the poor thing cooks its insulating pad and goes short dead to earth taking a few components out before the fuse finally fails. As usual, a great design with a crap implementation as sacrifices have been made to minimise the package size and a poor component layout on the board does not allow the transistor to be mounted on the top side of the board in the cooling air flow from the fan. Simply dialing the output current back to 25 amps seems to work, but frustrating to have a charger that can rally pump out 50 amps continuous strangled by a poor layout design
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
I'm told, the charge controllers are fully MPPT and set to restart charging when the pack drops to 13.6v, not 12.6v. I believe this is because in off grid situations and mobile, energy is being used constantly by fridges etc so switching back on at 13.6v means the pack doesn't get very low before it recharges. They are also a single stage charger, just bulk to 14v then off. Have noticed when the charge disconnects, after awhile they come back to below 3.5 when not in use.
These 40ah controllers are nothing like ebay ones, are big and cost $300 each. Can't say any more about them until they get into the bus. Doing it this way is my way of testing them without the hassle of making inside changes that may have to be done again. Also have more panels to put on the bus and as it gets used all the time playing, need to be sure everything works before installing anything.
Was told they tested these with a constant 40amp input and big draw downs of energy 24/7 to simulate big use over a long period and after 1 month their test gear showed they hadn't been effected in any way. So hopefully they will continue in that way for a long time.
OK, it's just that 13.6v is the equivalent of 4 perfectly balanced cells fully charged, so if that was as low as they drop they never actually cycled at all, they just supplied the current for the loads supplied. A lithium cell is not considered to have cycled unless the cell voltage drops below 3.2v, a shallow cycle is a drop to 3.3v and a deep cycle is a drop to 2.8v. Maintaining 13.8v while the sun shines will stop the continual repetitive over voltage charge of cycling from full to over full or 3.4v (full) to 3.5v (over charged) although high current input systems will benefit from a slightly higher boost cell end voltage to counteract the slight voltage spike seen near the end of charge created by high current being applied to a nearly fully charged cell. I guess the 13.6v to 14v regime could result in a faster to end of saturation regime in a multi cell in parallel pack as the 0.4v hysteresis allows for a bit of intercell balancing before the charging resumes. Might be an interesting experiment, I can set the hysteresis on the Dingo/PL20 to what ever I want, set the charging to slow switching instead of PWM switching and see what difference it makes at different charging currents. I must admit that the solid state relays don't see the funny side of switching rapidly under full load (150 amps) and tend to fire the cooling fan up on a 75% duty cycle for the last bit of charging, so a slower switching speed would suit them better.
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
G'day Terry, sorry but don't have a clue what you're talking about, but it sounds good. I just go by what my late mates kids tell me and it seems I'm now the test bed, but unlike Slowie, have little tech knowledge at all. They've been playing with these things for many years and seem to have a handle on how they work, I know their approach is to get the most use out of them for the longest time. So what you say about the charge restart voltage makes sense, as slowie once told me the aim was to use them without cycling much to extend their lives and keep them balanced.
So far haven't seen the controller fans come on, but it is winter and I'm only putting in 680w of panels into them. Things may change once they start getting 1kw+.
Thanks for the explanation, makes it easier to understand what they are up to and their mind set.
Finished testing the 40amp solar controllers and they work great, haven't had to touch my pack in any way and not one cell has gone over 3.5v in the last two weeks. It switches off at 14v and when I first put them on, one cell line would always go over 3.5, but the last two weeks they seem to have balanced up nicely and as the pack is being used every day for lights, winches and pumps, it switches back on at 13.6v and all the cells are virtually even all the time. I'm charging and drawing energy from the 4 points of the pack, instead of two, seems to help in balancing during charge and discharge.
Did say they would be about $300, but been told they will be dearer, have yet to get the bill. They will be for sale on ebay within the next couple of weeks I'm told, once the new batch arrives. They are also going to test a 60amp solar controller and will have a 20 amp mains charger with the same parameters within the next couple of weeks to test as well.
Talked to the Stone kids and they tell me they use 13.6v for charge restart, because the pack they've been testing for the last 6-7 years is set at that voltage and the pack has lost nothing in its capacity. It runs their office and night security system, so gets heavily used.
Yes, it is. They have taken over from slowie and going their own way, my only involvement is waiting for the 3 x 60amp solar charge controllers I paid slowie for and they should be here in the next couple of weeks. Don't have a clue about anything else, but know the youngest daughter has moved into slowies place and running things from there, so I'm told. I'd be useless any way as my technical knowledge is extremely limited and already having to research things myself to figure out how I should wire everything into the bus. Especially the 24vdc-12vdc charger, it's 60-amp, runs lead acid parameters and the solar controllers are only 40amp each and need to have their own panels. So will be putting 500w of solar into each charge controller on the bus, maybe I could use a 40amp and 60amp on the bus and run the dc-dc charger through the 60, when needed.
Certainly love the 40amp controllers, they are so good, the cell balancers haven't needed to work at all since using one. Tried them both out on the new lifepo4 pack and very happy, they shut off at 14v, the pack settles down to 13.8v without load, even though one cell line always goes over 3.5v. With a load on them, no cell lines go over and are pretty well balanced.
