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Forum Index : Solar : Epever Tracer 4215BN & Lithium Batteries
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
BTW, temperatures quoted on the Winston data sheets are ?? Try to keep battery temp below 35C and above 5C when charging. Discharging at lower temps is OK. What they don't show is that the internal resistance starts climbing quite rapidly below 10C. It is still damn low, but if you are checking the health of your batteries, by measuring voltage drop under heavy load, try to do it at consistent "room" temperature. |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Trev did some experimenting with these LYP batteries a long while back. I recall that at 3V/cell they are practically empty. I set mine for a minimum 3.2V/cell to trigger cutout. Klaus |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Interesting, I d/l the winston data sheets at the time and they had a fairly flat plateau down to 90%, stopping at 11.6 for 90% discharged, then the last 10% dropped rapidly to 10v where the chart showed 100% effective discharge Thats why I put it at 11.8v, the charts I had showed that was still at just under 75%, so I thought I was leaving just over 25% capacity as reserve and not wanting to hammer them too hard I'll have to go look them up again and check |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Hi Finn, I made a chart a few years ago to help people get their head around the numbers.  nowdays I set the voltages a little bit lower boost at 3.49 or 3.4875 float at 3.35 HVD 3.75 boost reconnect 3.25 LVD 2.95 the green section between 3.6-3.65 is for a top balancing BMS. not sure why you cant lower the HVD maybe you have to lower another setting as well. regarding the voltages at the bottom, well it is all about how much load you are drawing and how confident you are the cells are even at the bottom. at low loads the cells can get very empty while staying at higher voltages. a typical solar system load is not that high compared to an EV pack. if you are going to run them really hard then you can balance the cells at the bottom and set the LVD to 2.5 there is no danger of one cell being driven in reverse if they are all flat at the same time, they dont have the energy to do any damage. thing is you shouldnt chop and change either balance at the top and stay away from the bottom or balance at the bottom and stay away from the top (if you know one cell is smaller in capacity than the others). I know active balancing all the time is trendy but if there is one cell with different capacity than the others it will be out of sync with the others every cycle and get corrected at the top and bottom every cycle. I wouldn't get to hung up with balancing once you have them set up and even. I done a test with 8 400ah calb cells. after 589 days cycling without a balance I had to transfer 0.6 watts out of two cells into the rest of the pack. cheers installers tip. I buy a new file to clean the terminals and lightly coat the joints with dialetric grease. I'm confused, no wait... maybe I'm not... |
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| Alastair Senior Member  Joined: 03/04/2017 Location: AustraliaPosts: 161 |
I have 320AH of LFP batteries in a nominal 12v house battery system in our Isuzu truck based expedition vehicle (motorhome). They are configured as as 4 parallel pairs of 160AH cells connected in series. When I first bought the batteries and associated gear I had quite a lot of 12v equipment otherwise I would have gone 24v and may still do if some of the 12v only things give up. This has the advantage of reducing currents and voltage drops, plus my truck is 24v which would make that charging route simpler. I make sure that everything I buy is 12/24 now. I was a novice with LFP batteries but spent lots of time reading and a more time playing with things in the workshop before I designed the filnal system and installed it. First I connected all cells in parallel and charged them with a bench supply to 3.6v. I discharged them with a headlight bulb to 3.2v and then repeated this cycle several times. I then disconnected them and measured the cell voltages over 12 hours. At first I found that the cells were different but by the time they had self discharged down to 3.4v they were all within a range of +- 0.02 v. I made pairs of the ones with the closest voltages and connected them i series to make my 12v battery. I now started a series of more serious charge/discharge cycles with a logger measuring the individual cell pair voltages. Under heavy charge/discharge (80A/250A) I did see up to 0.3v difference bn cells but when they were left to rest they settle back to essentially the same. Under low discharge currents the differences were minimal. I decided not to use active self balancing as my tests gave me confidence that the Winston cells were well behaved. I did install a cell monitor and it warns if cell differences exceed a preset value and cuts the system off if the difference exceeds another. I saw the active balancer as a source of complexity and potential danger. I have read numerous reports of problems of this type. I installed my system 3 years ago and have had no dramas. I am currently designing a Micromite based logger that will incorporate the warning system so i can see a more dynamic record of the cell behaviour. My most recent test of the system shows a range of only 0.03v at 3.4v after full charge to 3.5v and 0.05v range at rest when discharged to 3.2v. Very happy with that. My current system has the following settings: HV cutoff 4.0v Bulk Charge 3.2v absorb 3.5v float 3.2v LV cutoff 2.9v cell difference warning 0.5v - shut down 0.7v To date the system has never shutdown and the warning has only happened under test when I put a sudden load of 3000w on my inverter (6000w peak) and was pulling over 250A. The warning was short lived and the max difference I saw was about 0.3v. I am building the monitor system so have a better track on what is happeningas the batteries age. The batteries can be charged from the engine - Redarc 40A Dc-Dc, Solar 4x150W panels on the roof , and mains Projecta 35A. The solar controller is a Victron 75/50 mppt (75v/50A) which has presets for most battery types but is fully programmable which is what I use. The Victron unit is excellent and I now shutoff the engine charge when the bulk charge level is reached and let the solar do the rest unless of course it is dark. I find the solar system works brilliantly and for our normal use the batteries are back up to full on a sunny day by midday. We have no gas, electric jug and induction cook top. We do much of our cooking on a portable gas bbq outside plus camp fire where allowed. When I can I will install an electric hw heater which will use the excess solar power. I bought an expensive diesel hw and air heater but decided to not install it after doing our first period in the truck without it having run out of time. No one here would understand. It is no big deal to use the jug for normal hw and not having the shower was no big deal as we have traveled for years doing the bucket bath. Getting older was the reason for putting in a shower. Sorry for the ramble but it looks like my voltage endpoints have ended up very near the same as Yahoos. There are many 'experts' out there on the best way to treat LFP batteries but I only take note of those that have used their systems in anger and can cite the behaviour. My values have varied a little but are now stable until I see battery performance with age changing. At the moment mine have changed little from new over 3+years. A point to note that if you do not plan to use your batteries the manufacturer recommends discharging them to ~50%. I take mine to 3.2v on the few times I remember. Mostly I just park and then remember when I check from time to time. Initially I just left the solar running which was bad and now I just turn it off and leave the system to slowly run down. Self discharge of LFPs is trivial. OOPs - sorry I did not realise i had gone on so much. Cheers, Alastair |
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| Finn Newbie  Joined: 16/01/2018 Location: AustraliaPosts: 15 |
Thanks Guys, I'm getting a good idea of how to set up my system which is a massive learning curve for me. Boppa, Thanks for your advice and help it is much appreciated "my 5 core goes batteries, to balancer (unfused- I am of 2 thoughts about whether it should be fused or not" As I have not setup my balancer yet should I fuse both monitor and the balancer and can I fuse them both on the same circuit or would I need to separate them and run separate wires? They balancer will be next to the batteries and the monitor will be about 2 metres away (wire Length). Dave, Thank you also for your help and advice, I'm gaining the confidence to hook up my batteries. The Charge/Discharge temps quoted on the Winston for my Lwp site if I'm looking at the right thing is -45c-85c, I don't foresee my battery temp ever getting above 30c or below 10c I don't like cold weather so I move around to suit. Yahoo2, Thank you also for your advice and input. The most draw on my batteries would be no more than 10amps at any 1 time most of the time it would be around 4amps for the fridge. I have the balancer now so I'm going to connect it up, what I don't understand is does the cell monitor cut off the charging to the batteries in undervoltage or overvoltage situation or is that where my Solar controller kicks in? Alistar, Thanks for your write up it was a great source of knowledge for me, I will be taking up your suggestion and start upgrading to 12/24v accessories. Thanks to all of you for your help a few more questions to come and I feel I will be confident to hook up my batteries. Cheers Everyone and please excuse my bad grammar and misuse of punctations etc |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I still am of two minds about fusing the balancer- in theory it would be bad if a fuse blew/ went high resistance as it would then prevent the balancer doing its job. I'm looking at putting a second monitor in the cab of the ute so it can be checked more regularly while driving, the current one is in the back (ideal for when camping). I prefer it to be fused as it is running through 3 steel panels (in grommets) and thus has the chance of getting a possible short on it- shouldnt happen, but I thought it prudent considering the power these cells can pump out and each of those wires goes directly to a cell connection.... (the cabin monitor is worse as it has to run under the body (inside a chassis rail) and pass through several panels as well, lots more possibility of failure!) Currently the monitor in the ute has provision for cutoff on high. low and individual cell failure alarms- it has a small 2pin connector that is used to disconnect the batterys if something goes wrong via a N.C. 200a contactor thats fed from the front battery and also sounds an alarm in the drivers cabin (piezo horn) In theory this isnt totally foolproof as the contactor will eventually flatten the front battery and reconnect the back batterys, but it literally takes days for this to happen |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
the way I build my gear the bms controls a relay that throws a contactor and both supply from panels and load is behind that point, once it is activated it must be manually reset. if you want the celllogger to do something like this on an alarm condition you will have to probably build that yourself. You would have to read the controller manual, I would assume the controller will disconnect the panels at high voltage and if you wire everything through the controller disconnect the load on low voltage. I would also assume it will automatically reconnect again. It is a judgment call on how many layers of safety you need, I dont trust controllers, I use an independently controlled contactor and it is automatically cycled once a month to check it is not fused. Not just for Lithium, everything I build is done that way. only cos this freaks me out.  I'm confused, no wait... maybe I'm not... |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
"the way I build my gear the bms controls a relay that throws a contactor and both supply from panels and load is behind that point, once it is activated it must be manually reset. if you want the celllogger to do something like this on an alarm condition you will have to probably build that yourself." are you able to show me some pictures or a diagram as what you said sounds like a good idea to me. What type of relay do you use please Boopa? |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Finn, You are looking at the right thing, but the information is not "helpful" look here Some useful info on this site. |
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| Alastair Senior Member Joined: 03/04/2017 Location: AustraliaPosts: 161 |
Finn, A few thoughts from when I built my system up. Over many years I have gained a lot of experience with lead/acid & AGM batteries in boats and 4wds. My tests with the LFPs taught me that they are very different beasts. My load tests showed little voltage drop with quite large currents hence the internal resistance of the LFPs must be very low. Having shorted a Pb battery in the past I made sure that my mounting methods and connections minimised risks. 1. I have manual isolators at both + & - ends, 500A key style. This allows the system to be properly shut off for making changes. 2. The BMS shunt needs to be protected even though it is at the ground end 3. The cuttoff solenoid I use is a Blue Sea 500A latching type mounted at the + end. I use high quality marine stuff where possible to minimise failures. 4. The wires going to each cell for the monitor/balancer stay live even when the isolators are off so I kept them light gauge so they act as a last resort fuse. 5. I have a sheet of clear perspex mounted over the top of batteries so that if anything falls down the chance of a short is minimised. 6. I have several leds right on the connections that show which are live. The current drain is tiny by comparison to the battery capacity so can be ignored. It is very easy to forget if an isolator is on/off when making changes or tests. The led is a reminder. 7. Vibration is a killer especially in boats or vehicles. Even a short section of unsupported wire hanging off a terminal will risk breaking unless heavy gauge. I tend to put a sleeve of clear heat shrink over the last part and cable tie it to a support. Not trying to teach egg-sucking but ... Cheers, Alastair |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Sorry finn, i am not home at the moment and my memory is obviously failing. I got someone to look at my notes where I thought we used a celllog to power a relay. it says i took it out and replaced it with a little board with a PIC micro and a ULN2003a ??? thats a relay driving chip. drives up to seven relays or the outputs can be ganged to drive bigger stuff. it seems I have not kept the code or circuit for that particular build. maybe the PIC could be replaced with arduino and a relay could be driven in a similar way. it is only a failsafe for a faulty controller or to stop a load from completely draining the cells. the cells themselves are pretty placid, I have some 12v jump packs that get an absolute caning, they are charged with a charger that cant go over 14 volts and they have been bottom balanced, there is no safety on them at all. although I do use a low voltage cutoff switch that evwest sold me if I stick one on a portable electric fence. I'm confused, no wait... maybe I'm not... |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
Cheers for the info. Would any of you blokes know of anyone in western Victoria who could help me set up my batteries? I'm happy to pay but I would like to work with them if possible so I can learn. |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
G' Day. Is it ok to insulate around my Lyp batteries or should I leave them open to the air? |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I left the top and bottom open(ish) on mine with a airgap at the bottom, and the top open, however as mine are using an aluminium box as the clamps thats bolted to the tub of the ute (admittedly with an airgap on the bottom 2/3) I havent any concerns about overheating. Trev did have issues with his ute with the original fiberglass tub which was replaced with Al, but his situation is vastly different, he's pulling much higher currents than anyone else is likely to see. Personally I wouldnt insulate them unless you have a heat source very close |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Finn, Because it is recommended not to charge below 5C, the batteries are outside the house and we are at 260metres on Banks Peninsula (near Christchurch) I have the batteries in an insulated box. Inside the box is a 25W heater made out of electric blanket wire. The temperature normally cycles +/- 1C around 20C. Even with the heat wave we have had for the last few weeks I have not seen battery temperatures above 23C. Internal resistance for my 24V battery is 3.5mOhms. At 50A that is 50A * 50A * .0035Ohms = about 9 Watts. And that only happens when the toaster is on! Average power dissipation more is like 5A * 5A * .0035Ohms = 90 milliWatts. If it rarely goes below 5C at your place then it is probably not worth the bother. Depending where you live keeping them under 35-40C might more of a worry. |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
I have them setup in my mobile home and heat sometimes is a big issue as temps can hit 60c or more in my rig once the steel of the bus gets hot, if I can take the air away from around them I know I can regulate the heat too 20-30c I also plan to have a temp gauge fitted in with them. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
I also have a temperature sensor connected to an alarm system using Gmail's SMTP server and your very own email2SMS service at aussiesms $20US for enough credits to hopefully last me the rest of my life. Cheap insurance. Good luck with the build. Dave |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
Boppa, or anyone who can tell me please How did you connect your wires from your fuse box to your Monitor did you cut 1 end off The 9 wire plug that came with the Monitor and join the wires? |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Yeah, soldered and heatshrinked, I looked for a plug/socket arrangement to fit it, but ran out of time and just did it the cheats way (the ute had to go to Tassie for a holiday and I didnt have time to wait for a socket to arrive) eta I used the trailer colour code for 5 core trailer wires so it would be easy to remember (I grew up in nsw, and thats the trailer plug wiring I grew up with) 1 tail brown 2 left yellow 3 right green 4 brake red 5 ground white You can use anything you like but write it down so you know later on- thats why I used the old trailer wire code- I'll never forget it lol |
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