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Forum Index : Solar : Epever Tracer 4215BN & Lithium Batteries
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| Finn Newbie  Joined: 16/01/2018 Location: AustraliaPosts: 15 |
Cheers Mate :) I want to bottom balance my batteries could someone you run me through the procedure please I have 4 LYP Winston cell 130AH? I will only be able to recharge them with my solar system. |
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| Boppa Guru  Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Ive never bothered with bottom balancing, I paralleled them and charged when I first got them and simply used the monitor setting for imbalance between the batts to disconnect if one gets too out of wack- hasnt happened yet (that little monitor has a lot of handy stuff in it, the low volts, high volts or imbalance between cells all disconnects the load and batts using the output relay on the monitor- the little 2 way plug) The highvolt disconnect is a separate circuit I already had floating around, it opens the 200a N.C solenoid I had- handy as the solenoid only pulls current from the charging source (the car alternator in this case) when its in fault condition and not from the batts, so there is no current being drawn in its normal state (apart from the mA drawn by the voltage checker) once it gets over 16v it turns on the solenoid and disconnects the batts Should never happen, but belts and braces lol I really should look at a secondary lowvolt disconnect for the fridge (and caravan when its plugged in) as the monitor currently turns off the fridge when the batts are low (via a 30a changeover relay ) but I'm not that worried as the fridge has its own lowvolts turnoff too, as does the caravan, and the monitor is the 2ndary one |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
Thanks for all your advice Boopa can you recommend a charger I can purchase so I can charge my batteries in parallel? Cheers Finn |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I didnt use a charger, I had a 0-20v 4a power supply I have been using for years as a bench supply, just set it to 4v and kept an eye on it until the amps dropped off, then called it good |
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| Finn Newbie Joined: 16/01/2018 Location: AustraliaPosts: 15 |
G'day again, I have a 12v Compressor that I carry around in case I get a flat or a puncture it says it draws up to 45 Amps, would this be ok to use with my LYP 130 AH batteries it would be for bursts of around 5-8 Minutes? Cheers |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
They are quite capable of that lol- not even stretching their legs! 130AH lyp have a maximum constant discharge rate of 390A (ie 3x CA), and pulses of up to 1300A (10x CA) are within their specs too (they dont actually specify pulse duration tho grrr) Interesting the Winston batts have a much wider temp range than many quote ie -45 deg to 85 deg C (i am wondering if that isnt a mistake- many online people seem to think its about 5 to 30 deg, 85 deg F is about 30 deg C, and 45 deg F is close to 5 deg C or have yanks just looked at that 85 deg and assumed its in that weird F thing they use, when its really in C???? must check with them... edit email sent edit again, forgot link to specs page winston 130ah lyp edit to add again I am certain that this 5/30 nonsense (which seems to be quite widespread over the net) is nothing more than a yank confusing 45 (specs say -45) and 85 as being in that stupid F instead of Celsius.. 100% convinced of this, but awaiting confirmation from Winston as to the true operating temps and capacities at various temps especially since Winston at least specify their temps as -45-85 deg C (I think someone read that as 45 to 85 degs Fahrenheit....) and everyone has just accepted it as gospel...  |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Good luck with asking Winston. They didn't reply to my request for clarification, but they did replay when I asked the manufacturing dates of my cells. Might be worthwhile searching through this site: GW They seem to have quite a bit to say about LiFePO4 and as far as I can work out they are NOT American. There is a graph of internal resistance versus temperature on this site which shows IR going up 10 times the room temperature value ... at 0C. I suppose one plus could be that if you do charge at 0C that the battery will warm up quickly! |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Ive looked at that site, and its graphs seem to agree with other manufacturers Ive checked. Yes they have a voltage drop as the temp decreases,(ETA and their capacity decreases) to the extent that at 0 deg C you have effectively lost 50% of capacity, and at -20 deg C you are down to about a third of your rated capacity is available, but all batterys exhibit this capacity loss, and lyp is actually better than either gells or L/A in this regard In extremely low temps, some low volt cutouts may trigger early and cut your power off when some capacity is still available, a programmable low volts cutoff that triggers according to temp may be good in such a situation (Canada or the south pole) I dont agree with your conclusion about the internal resistance, it increases as the temp lowers, so with the same charging voltage, as the temperate drops the charging rate will also decrease- if the internal resistance (which effectively displays as a series resistance to the cell) increases 10x at 0 deg, then with the same charging voltage, the charging current will actually decrease!!! as expected... So charging will take longer, (eta maximum) discharge currents will decrease, and capacity will also decrease- exactly as shown on those charts.... |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Well I just received a reply, which confirms operational temp is -44 deg Celsius to 85 deg C added was a pdf with the battery specs and charge/discharge graphs (similar to most other ones I have seen on other manufacturers sites)   |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Good to hear Winston confirmed the temperature range. I will place comments made in the link and by Electrodacus.com for recommended temperature range in the "nice to have basket". At the risk of deviating too far from the OP I do submit my calculations for comment: 4 * 60 cell panels at 250 Watts about 1KW. Say a Vmp of 33V and a short circuit current of 50Amps. Panel source resistance = 33V / 50A = 0.66 Ohms. My 26V batteries have an IR of 0.035 Ohms. Current into the battery = 33V / 0.66 + 0.035 Ohms = 47.5A. Heat in battery IR = 47.5 * 47.5 * 0.035 = 79 Watts. Battery IR increases to 0.35 Ohms. Current into battery 33V / 0.66 + 0.35 = 32A. Heat in battery IR = 32 * 32 * 0.35 = 372 Watts. This does assume that the Vmp stays constant from 25C to 0C, so there could be at least one error in my calculations. Maybe the short circuit current varies with temperature as well. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I cant actually see where you are going with this, apart from showing that if your calcs are correct, a cold battery would rapidly rise back up into the 20 deg range anyway, where it would be back at normal IR again Lead acids as an example have a higher IR than lith batts anyway, which is one reason I installed 200a breakers as the short circuit current on a winston is way higher than the equivalent LA batterys can deliver |
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