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  3. Colin

    Axpert battery recomended charge voltage

    I have noticed that the Axpert will only go to 57.8V bulk charge if the available charge is at least 50Amps, as current drops, so does the voltage. On cloudy day with only 1KW available from solar (10A into battery), battery voltage will only be about 52V -When I run geny, battery voltage climbs with current, 30Amps into batteries - voltage at 54V, 40Amps -55.5V, then only gets to the 57.8 at 50Amps. Then again as batteries nearing full, current trailing down, voltage drops along with the current. Should this voltage not stay constant at 57.8V till current drops enough? Running 73.00b with setting 32 - bulk charging time set to aut
  4. Yesterday
  5. Coulomb

    Axperts and Bypass

    My battery bank is an extreme DIY job. I bid on an EV kit on Ebay. It had the battery, motor, motor controller, battery charger, and other bits. I think I won it for about AU$2000, including 45 160 Ah LFP cells (nominally 144 V). These were older cells, from 2009, about 5 years old at the time. The EV kit was an impulse purchase by a business person on an overseas trip. [url=http://forums.aeva.asn.au/viewtopic.php?p=45314#p45314]EV Conversion Kit[/url] on AEVA has pictures and a full list of contents. 45 cells is a bit of an odd number, when 16 cells makes a nominal 48 V system. It's just a little short of 3 48 V strings. In retrospect, I should have been thinking 15 cell strings, but that wasn't on my mind at the time. Weber was interested in one string of 16, so that left 29 cells, enough for 14.5 buddy pairs. It happened that a colleague in Brisbane was converting a car, and had an accident that ruined some 24 odd cells. I bought those for AU$200. His was a small car, and he used 100 Ah cells. So I had enough there to make an 8S2P 24 V pack to replace my ailing lead acid lighting system pack, and several cells left over to finish off my 48 V system. So I used two 100 Ah cells to buddy with one 160 Ah cell, and four 100 Ah cells to make the last "cell" of the 16S bank. So most "cells" of the 48 V bank were 320 Ah, the "hybrid" was 360 Ah, and the "quad" was 400 Ah. I figured that because the 100 Ah cells were abused and were unsuitable for EV work, I could not count on them being full capacity, but I thought I might end up with roughly 320 Ah each. So that makes about a 320 x 48 = 15,400 Ah or 15.4 kWh bank, or it would have been when new. LFP loses capacity of a percent or two per year, so realistically about a 14 kWh bank. Alas, the abused 100 Ah cells had a much higher internal resistance than the 160 Ah cells, which although now 9 years old, were unused before I put them in my energy system. Weber and I have our own battery management system, called LyteFyba, which can accommodate different internal resistances, so I put up with it for years. But now the quad "cell", which has by far the highest internal resistance, seems to be causing the whole pack to have low capacity. I work the pack pretty hard; it often drops overnight to 40%, sometimes 30% SOC. We have some of the most expensive power in the world here, so it's worth minimising mains power usage. So that's what I mean by one of my cells failing. I plan to swap out some of the bad 100 Ah cells for better ones in my 24 V system, hopefully in such a way that the 24 V system is still usable. The latter is convenient as a test pack for battery charger repair, and as an emergency backup for the main energy system. It still runs a few lights in the house as well. Edit: my latest figures for internal resistance are 490 μΩ for the 360 Ah buddy pairs, 850 μΩ for the hybrid, and a massive 1,800 μΩ for the quad. [ Edit: it's the quad with the highest resistance, not the hybrid. ]
  6. Most chargers use three stage charging. Bulk, followed by Absorption, followed by float. For example, let's say you set absorption to 57.6V and float to 54V. Bulk: the charger will charge with the maximum configured current until the voltage rises to 57.6V. Absorption: The charger holds the voltage at 57.6V, while the charge current tapers off on its own as the battery charges. Float: The battery is about 90% full at this point. The charger drops its charge voltage to 54V in order to reduce off-gassing. Because the battery isn't full yet, it needs to spend quite a bit of time at float level. Now, the battery will always accept more charge current at the absorption voltage than at the lower float voltage. So a tail current of 1% at the higher voltage is a better indication of a full battery than the same tail current at the lower voltage. So, the recommendation from Victron, for solar systems that are cycled daily, is to set the BMV "charged voltage" to just a little bit below the higher absorption voltage. If you do this, the BMV can never reset once the charger goes to float. It can only do a reset if the tail current drops really low while it is still in absorption charge. This is not a problem when using other Victron kit: They don't go to float too easily. Their absorption phase is calibrated according to how long bulk took. But the Axpert goes to float really easily. If you use the Victron advice, it might never reset because it doesn't spend enough time at the higher voltage. So I'm saying you then need to use a little bit less than the lower float voltage and hope for the best. Of course, it is not a problem on systems that are not cycled too often.
  7. what i ACTUALLY meant is the 'republic of wp' - but the road is important, it'll be congested though, one way south...
  8. Thanks pilotfish so basically a higher bulk voltage to ensure that the batteries are being charged up fully and equilised if necessary but because it is programmed for utility/standby a lower float voltage (but higher than 54.0V) so I don’t kill the batteries if we don’t have consistent power outages and they remain in float for excessive periods. Unfortunately this is the issue, don’t have any specs for these batteries apart from what’s printed on them as per the pic above and I have tried searching for them on the net but cannot find anything on them whatsoever so am guessing since they are gel batteries your recommendations should work for them? @plonkster would love your feedback on my post below cheers
  9. I must have miss-heard - I thought that the saying went "the only good things in WP came out of Gauteng"
  10. I hope that they do - that will give OUTA ammo in court to send them back to the drawing board and delaying for another 6 months.
  11. If Utility priority leave the setup as 57.6 bulk and 54.4 float (or there about, try and find your battery spec for standby voltage), if you keep your batteries at a high voltage for a long time they will dry out and fail prematurely. I can do it because on SBU setting my batteries don't spend a long time at [57.6/56.8] - some days not reaching there at all. On average my BMV will sync every second day.
  12. Aaaah you mean like the only good thing to come out of Gauteng? The road to Cape Town? :-P
  13. what ever happened to the republic of wp drive?
  14. So gents my current set up is more for backup during the frequent power cuts we get in Malawi. However of late they have installed some emergency generators and instead of 4 days a week where we have no power for up to 20 hours a day we are now down to 1 or 2 days a week. So would you say I should set up the charging voltage parameters for cycle or standby use? Depending on the reliability of our utility power in the future I may decide to swap to a Solar priority from Utility priority which is what the inverters a set to on program 01 currently.
  15. That is exactly my current setup - bulk at 57.4 and float at 56.8 to avoid excessive gassing.
  16. That's probably better than dropping to float too soon. I'm just talking from my own observation after moving from a Microcare MPPT to a Victron charger. They stay in absorb much longer. Then I did a full charge with a Multiplus, goodness, it remains in absorb even longer! In the beginning I thought it was overcharging the batteries... then I noted how the tail current continues to drop... right down to below 1%. And then the inverter went to float. That's when I realised what it really takes to get a full charge on lead acids...
  17. Hi Pilotfish - when I use to have AGMs I would do exactly as you describe. Before I changed to Coulomb's firmware due to the charging bug we would go to float early and I noticed that the batteries would still accept 15-20A at the lower float voltage and then tail off. Only after I changed the firmware did it behave correctly with <3 A going into the batteries at float. I mention this since it seems that batteries not near fully charged it still can accept a fair charge rate even at the lower float voltage. At 25°C the gassing voltage is 57.4V but this drops to 56.8V if batter temps reach 30°C. I have found my AGMs were about 3-4 degrees above ambient temperature while charging so it is something to consider with VRLAs.
  18. Still does not account for them wanting off-grid systems registered. I suspect they will try and introduce this over the Xmas break (standard ANC practice for anything when they try introduce controversial legislation.
  19. gabriel

    charge pattern

    it seems to fit the pattern, although i'll monitor and let you know. in the meantime images of the situation just before 100 soc
  20. pilotfish

    Axperts and Bypass

    Haha - I think you may have caused some heart issues
  21. I agree with this statement, but I have recently come to believe that it is as a result of incorrect advice on the forum and not necessarily an Axpert fault. If you look at any number of AGM/GEL battery spec sheets for example the advice is fairly similar (but please use your own spec sheet); From Vision 6FM100P-X spec sheet Cycle Use = 2.4 to 2.45 VPC = 14.4 to 14.7 per 12v battery = 57.6 to 58.8 per 48V bank Standby use = 2.2 to 2.3 VPC = 13.2 to 13.6 = 52.8 to 54.4 per 48V bank The thing is that we are (mostly) using our batteries in Cycle Use and not Standby, but for some reason we all charge out batteries to Cycle Use voltage and then drop off to Standby Use voltage, not allowing the time to fully charge and equalize. Nowhere on the spec sheet does it mention dropping to standby voltage when in cycle use! So why not set bulk and float BOTH to 57.6V (the lower end of the scale to minimize gassing and stay away from 60V capacitor limit), then your batteries will get charged properly - problem over!
  22. Chris Hobson

    Axperts and Bypass

    Hi Coulomb could you expand on this. How big is your battery bank? Is it 16S or 17S? How old is the cell is it a recycled cell or something that was new when you bought it?
  23. Take a photo of the unit and a photo of its SN sticker.
  24. Thanks plonkster, very informative, will amend my settings as you have recommended. In terms of tail current percentage is this the residual current after the batteries have reached float or is it the difference between bulk/absorption currents? Also for lead acid batteries why is 4% too high? Is the current threshold at 0.10A OK? Is this setting for when absorption charge is over? I did watch the video and your edit has me a little confused. When you say set the charged voltage 0.4V under the absorption voltage, did you mean float voltage? So with the Axpert absorption voltage issue will I have an accurately synchronised monitor ever? Another issue I am facing is connection over Bluetooth, which works seamlessly on my Android phone but not at all on my iPad Pro, it just keeps saying no devices found in the VictronConnect iOS app. Any idea why this is?
  25. pilotfish

    Electric Bicycles

    Check out the bikes on this site - maybe they can sell you something or point you in the right direction; http://e-lectricventures.co.za Note that a typical Argus cyclist can produce 250w (a finisher, not the winner!) for about 1 minute before collapsing in a heap - so a 250w is more than enough for a pedal assist motor.
  26. plonkster

    Victron Bluetooth Dongle for BMV702

    You just need the vedirect-usb cable you presumably already have. Of course you can only connect it to one device at a time, so you cannot also have it connected to ICC. Same is true for the bluetooth dongle though, it plugs into the single vedirect port on the bmv, so you cannot have that in place and also use it with ICC. To get it going, see here.
  27. plonkster

    charge pattern

    I would ideally want to see the charge current and voltage as well. What you want to see is 1) voltage held at absorption level, 2) current dropping off nicely to under 2A, 3) SoC rising while all this is happening, and then after the current has been that low for long enough... should follow the jump in the BMV SoC.
  28. gabriel

    Victron Bluetooth Dongle for BMV702

    i have not investigated that route, it seems i can access the rpi via my present pc screen, keyboard and mouse. if so that should do the trick. would there be need for an extra cable to the shunt or axpert? [stupid q i believe] so if i get an rpi and am able to interact with it with my present hardware it would be far more cost effective for i can use the rpi for other tasks as well. this is uncharted territory for me and i believe i will have to start with 'rpi for dummies'
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