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Bush Man

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  1. Bush Man

    Fridge

    Thx! My concern was more that the Axpert cooling fans would start every time the fridge starts up, which would be noisy and add to the Axpert's wear. From my recollection with the first installation though, the Axpert's additional fans only kick in somewhere past 1kW. In addition, the fridge's supposed 800W start-up draw would only be for a second or so, probably in any event too short to trigger the Axpert's additional fans.
  2. Bush Man

    Fridge

    Let's say every start-up uses 5 x 160W = 800W, it wouldn't be nice if the 5kva 3kW Axpert has to start its fans every time the fridge comes on. Do you possibly know at what watts the Axpert's additional cooling kicks in?
  3. Bush Man

    Fridge

    Thanks! Inverter is a 3kW Axpert, with 8 x 200 (260) Ah Omnipowers and 12 x 250W panels, so start-up current should be fine. I wonder why two similar models would have such a large difference on wattage? Is it possible that the new model has a "turbo" function and only uses the 160W when that is switched on, otherwise only using around 90-100W? Or would the 160W be a fixed figure, with the compressor running for shorter periods than for the 90W model? Will buy, measure and revert for posterity in any event.
  4. Bush Man

    Fridge

    Afternoon! Two years ago I installed a Bosch fridge-freezer in an off-grid place which I built - model KGW36XL30S, A++, 90W, 226kWh/year (619Wh/day). It's still running beautifully. I measured consumption over a period of 3 days, and it was spot on at arount 600Wh/day. That model is no longer in stock. For the place that I'm building now (also off grid), I'm looking at the similar Bosch Fridge-freezer KGN46XI32, A++, 160W, 258kWh/year. My concern is the 160W, vs the previous model's 90W, although the annual kWh is similar. Should I be worried about the almost double wattage?
  5. Bush Man

    Axpert Low Voltage Warning Error

    Thanks to all! I'm in a remote off grid location, so that makes load testing a bit complicated. The system was commissioned in September last year. About two months ago I checked and noticed that on the one bank there was a substantial voltage variation. The lowest was at 11V and the highest above 13V (no irregular low voltage warnings at that point). The second bank was well balanced. At Chris Hobson's advice I brought the lot back to town. I charged all the batteries to around 13V, and they all held their charge perfectly for the three weeks that I monitored them. The only exception was the 11V one, which wouldn't accept charge at all. Sinetech tested and exchanged it for me. I re-installed the lot with a HA-02 battery balancer on each bank. My typical load is very small - energy efficient fridge (600Wh per 24h) and LED lighting (say 300Wh per 24h) only. 6x250W panels in 2 strings of 3. It's a big schlep to bring the lot back to town for testing. Is there no reliable test that can be done with my voltmeter? There is a 1500W microwave oven which I use occasionally for a minute or two, so I can put a load on the system for testing purposes. My voltmeter readings have always agreed with the Axpert reading to within 0.1V. If there were a bad cell, would the Axpert not show an actual low voltage reading? Why would the low voltage warning start blinking at 51V if it is only supposed to do so at 49V? My sense is that I should start by resetting and reprogramming the Axpert in case it became confused somewhere along the line?
  6. Bush Man

    Axpert Low Voltage Warning Error

    Morning to All! I have the 5KVA 48V Axpert connected to 2x4 150Ah Omnipower Batteries. The Axpert's low voltage cutout is set at the highest possible setting - 48V.. It's very rare for me to go below 50V. On the odd occasion in the past that I did so, the HS04 Low Voltage Warning started blinking at around 49V, and the system cut out at 48V. Of late, the low voltage warning starts blinking at around 51V, and the system cuts out at around 50V. This is despite the low voltage cutout setting still being at the highest possible 48V. Any ideas how to set this right?
  7. Bush Man

    Omnipower Initial Charge Current

    Thanks again, Don! Would the following calculation not also be correct to determine amps available for charging during sunlight hours? Total load in a 24 hour day: 1500 watts Average load per hour: 1500w/24h = 62.5W Say 80W, as the fridges would be running more during daytime. Now take the present 1500W panel array less losses = 1300W Deduct the 80W base load, to arrive at 1220W available for charging. Now calculate Amps: 1220W/48V = 25.4 Amps available for charging Could one then take this figure further and say that 25.4Amps/300Ah of batteries translates to charging at 8.5% of capacity? According to Karl 10-13% of capacity would be the norm for flooded lead acid batteries, as opposed to the stated minimum of 25% for AGM Gels.
  8. Bush Man

    Omnipower Initial Charge Current

    Thanks for all the input, Don! Am I correct then in my understanding that the configuration of the panels is also critical in determining the Amperes produced? In this example, I presently have two strings of three panels together producing 16.2 Amps. If I reconfigured to three strings of two panels each I would have 8.1 x 3 = 24.3 Amps? The Volts would then drop to 30.83V x 2 = 61.66V. This is still within the 5kva 48V Axpert's range of 60-115V. If I were to add more panels, would one then rather look at stringing them two together rather than three?
  9. Bush Man

    Omnipower Initial Charge Current

    In comes Victron with their Gel and AGM Battery manual attached. 15. Charge current The charge current should preferably not exceed 0,2C (20A for a 100Ah battery).The temperature of a battery will increase by more than 10°C if the charge current exceeds 0,2C. Therefore temperature compensation is required if the charge current exceeds 0,2C Their maximum charging current for AGM Gel is thus 20%. They don't specify a minimum, as opposed to Omnipower's stated minimum of 25%. Victron-GEL-and-AGM-Batteries-Manual.pdf
  10. Bush Man

    Omnipower Initial Charge Current

    Went to Sinetech yesterday to collect my replacement 150Ah battery (thank you!) Sat down with Karl. He's their senior technical sales manager and really seems to know his stuff - been doing batteries for about 20 years. He remains adamant that one needs an intial charge current of around 25% of capacity for AGM Gel batteries, irrespective of the depth of discharge of the battery. His words were "amperage is key". He said that if there is not enough current, the impedence (or resistance) of the battery increases which leads to negative chemical processes in the AGM Gel batteries that he explained but that I didn't quite follow. I mentioned that my three stage charger only does bulk charge up to about 12.5V on the Omnipowers, and then goes into absorption stage with a reduced current. Karl said that even if the battery is at 12.8V, you still need the high initial charge current. Karl's suggestion was that with my very limited base load of 1500Wh per 24h day (energy efficient fridges and LED lighting only) I would be much better off if I removed one of the two strings of 150Ah batteries and add 2-3 more panels to my current 1500W array for more current. My depth of discharge would go up from 10% on two strings to 20% on one string, However, he says this would have a much smaller impact on these batteries' longevity than the shortage of current that I have at present. I'm not sure how to calculate the amps currently produced by the panels (6 x 250 Watt Enersols, 2 strings of 3 each). However, Karl says they do not even provide enough current for a single string of 150Ah batteries (36A required), let alone two strings (72A required). He says this will seriously reduce the lifespan of the batteries. I would appreciate any thoughts.
  11. Bush Man

    Omnipower Initial Charge Current

    Will chat to them and revert.
  12. Bush Man

    HA-02 Balancers

    How does this relate to the minimum current of 72 Amps that may be required to charge a 300Ah Omnipower bank as being discussed in the thread below? Do the HA-02's limit the charging current to 10 Amps?
  13. Bush Man

    Omnipower Initial Charge Current

    Thanks, Chris If one reads Sinetech's intro at http://www.sinetech.co.za/battery-care.shtml it says that bulk charging takes place up to 85% of battery capacity. Wouldn't it then be correct to surmise that at anything below 85% one needs a minimum charging current of around 25% of capacity? I'll appreciate some thoughts that I can run past Sinetech when I (hopefully) go and collect my replacement 150Ah battery. They were quite adamant about having sufficient panel array capacity to supply the minimum charge current. Will revert after chatting to them.
  14. According to the staff at Sinetech and the Omnipower Care Sheet attached the Omnipower 150Ah (and other gel) batteries require an initial charge current of 36A, or 72A for two strings. This translates to 24% of capacity, whilst the general wisdom on the forum would not exceed 13%. Two 150Ah strings would thus need about 4000W of panels to provide sufficient initial current, or a daily capacity (5hrs) of around 20 000Wh. In my off-grid setup (48V, 8xOmnipower 150Ah, 5kVA Axpert) I rarely use more than 1500Wh per 24h day (Energy efficient fridges and LED lighting only). My 1500W panel array would be more than sufficient for that, providing 7500Wh per day less some losses. Does that mean that in order to use Omnipower or other gel batteries I would need three times as many panels as I currently have, only for the sake of initial current? Would that also mean that for a low base load it doesn't make sense to consider gel batteries? Omnipower Battery Care.pdf
  15. Bush Man

    Charging matters

    Thanks, Chris! I have a Meanwell 3 Stage Switching Mode charger http://www.bushpower.co.za/products.asp?pid=256 Will that do the job?
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