Pylon Cables and advice please

[Val33]

Hi all,

I’m after some advice.

I have a stack of 9 pylon batteries connected to a Lux acs.

I don’t really like the standard Connection scheme with such a big stack and am considering splitting the stack (5/4) in terms of power connection to the inverter and using two sets of the long cables direct to the inverter, keeping the single data cable. Good idea or pointless?

One of my us2000 packs has a slightly low cell, I’ve had this before on another pack and a long spell, two days plus, on charge normally sorts it. I’d really like to just disconnect this pack from the stack and connect it to a suitable power supply or trickle charger so that I can continue to use the remaining batteries as normal. To do so, without having to take the whole stack apart, I need a pair of slightly longer link cables, any ideas where to get them? And, any recommendations for a cheap charger?

Finally, on the connection to the inverter. Currently, the batteries are connected directly, no cut off switch or fuse. Should I be adding these? If so, what exactly should I add and where is it best to buy from?

Many thanks

[Stinsy]

A better way to do it is to have a 2nd set of long cables connected to the unused black/red terminals at the top/bottom of the stack. This method is described in the manual.

[sharpener]

Finally, on the connection to the inverter. Currently, the batteries are connected directly, no cut off switch or fuse. Should I be adding these? If so, what exactly should I add and where is it best to buy from?

Many thanks

Yes. I don't but the Pylon Force-L2 BMS incorporates a circuit breaker instead. Without that, good practice would be to fit them externally - fuses are reckoned to be more reliable than breakers. Most decent solar suppliers will have them.

And the long leads - you can use them to charge the dodgy unit on its own, and subsequently fit them to the other end of the full stack as @stinsy suggests. Try midsummer or off-grid engineer for example.

[nowty]

How big is your inverter ?, if its only 3.6kW there is little point changing it from a single cable connection. However if its larger then the official Pylontch way mentioned by Stinsy will work but its not ideal as the middle packs in the stack will get exercised less than the outer ones.

To do it properly the packs can be split this way (taken from a Victron recommendation), ideally equal number in each stack and DC cable lengths to the intermediate DC bus bars equal.

From the diagram ignore the Victron cable and pretend the reference to Goodwe is your LUX. The DC cables from the intermediate DC bus bars to your inverter(s) can then be higher spec.



Link cables ?, for the DC ones I buy a long and short cable and splice them together with a butt splice crimps. The data cables are just standard ethernet patch cables.

You should have suitable fuses and preferably a DC switch.

[Val33]

Many thanks all.

Thanks Nowty for the diagram, that’s exactly my intention as although the inverter is only 3.6kw I do worry that the middle of the stack is suffering.

While I’m at it, I’ll add in the fuses too.

In case anyone else has not realised this, the pylons only balance the cells when fully charged. If you regularly run them out in the winter months, it makes sense to delay the discharge start time (or grid charge end time) in the morning by however many hours you normally have them idling empty in the evening, then, they will be at 100% for much longer, allowing the cell balancing to do its stuff. This seems so obvious to me now, but had never occurred to me until today!

[sharpener]

In case anyone else has not realised this, the pylons only balance the cells when fully charged. If you regularly run them out in the winter months, it makes sense to delay the discharge start time (or grid charge end time) in the morning by however many hours you normally have them idling empty in the evening, then, they will be at 100% for much longer, allowing the cell balancing to do its stuff. This seems so obvious to me now, but had never occurred to me until today!

This is perhaps over-cautious. Looking at the record over the last week my batts have reached full charge on only 3 days out of the last 7. Yet the balance seems OK, the max-min delta V is 30mV at the point of full charge and 20 or less the rest of the time.

Over a longer time scale I can see that after a week of being completely discharged every night the first charge to 99% resulted in a delta V of 40mV with an initial spike of 50, after which it quickly settled back to the same pattern as above.

My main concern with scheduling the cheap rate charge is the compromise between running out the following evening and leaving enough room to benefit from any daytime PV there is. Adding the third pack was a big help with that, the downside is the current required to charge it fully during the night now results in fan noise from the inverter.

[AlBargey]

.... the downside is the current required to charge it fully during the night now results in fan noise from the inverter.

You can programme the 'disable fan' assistant in Ve.Config to disable the fan during charging, which lowers the charge current to stop the fans kicking in. I've done this for an install and still see the full 48v 70a output at the beginning, then the Multi ramps down to 55a - 45a to stop the fan coming on.

[sharpener]

.... the downside is the current required to charge it fully during the night now results in fan noise from the inverter.

You can programme the 'disable fan' assistant in Ve.Config to disable the fan during charging, which lowers the charge current to stop the fans kicking in. I've done this for an install and still see the full 48v 70a output at the beginning, then the Multi ramps down to 55a - 45a to stop the fan coming on.

I get 1 hour cheap between 2300 and midnight so charge then at full power. I've tried using Node Red to limit the current after midnight; when the limit was set to 20A the fan didn't come on at all. But I now need 25A over 6 hours to complete the charge and this brings the fan on.

So I would be surprised if the disable fan assistant allows more than that but I will try it and see. Also it will limit the charge rate during the day, and now that I have 8 more panels I can achieve the 70A max in full sun even at this time of year. Charging the batteries is worth 43p/kWh so is of more value than diverting the excess to the immersion heater at 11p.

[Tinbum]

Charging the batteries is worth 43p/kWh so is of more value than diverting the excess to the immersion heater at 11p.

Pehaps stop the immersion during the day, so it doesn't use power from the battery. You heat the immersion during the cheap rate and have to put less back into the batteries during the cheap time. (if your not already doing that).

[sharpener]

Charging the batteries is worth 43p/kWh so is of more value than diverting the excess to the immersion heater at 11p.

Pehaps stop the immersion during the day, so it doesn't use power from the battery. You heat the immersion during the cheap rate and have to put less back into the batteries during the cheap time. (if your not already doing that).

Immersion is on a diverter so in the daytime it only uses what otherwise could have been exported at nil recompense (can't get SEG).

So HW either heats at cheap rate (11p) or I use the oil boiler which is coincidentally almost exactly the same price.

Whereas charging the battery from PV displaces daytime consumption at 44p/kWh (plus VAT, minus round-trip losses).