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New Setup - Advice / Input required please


DennisD
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Good day all

This is my first post but I have read a lot on this forum but unfortunately the more I read the more confused I get.

 

I would really like your expert advise on the following:

 

I currently have a Xantrex GT5 (grid tie) inverter with 23x260w solar panels.  I had this connected now for just over 3 years.  Unfortunately this is not a load shedding solution and I am looking at adding the following:

1x SOL-I-AX-5K inverter

I need to decide on 1 of the following two options:

4x 200ah Vision AGM batteries or

1x PylonTech 3.5kWh  Battery

If the 200ah AGM batteries are capable of sustaining a 2500va load for 3 hours (I know this is not actual figures, just using as an example) my question is : how much time will the PylonTech 3.5kWh  Battery give with the same load ?

 

Thank you for your advise.

 

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19 minutes ago, DennisD said:

how much time will the PylonTech 3.5kWh  Battery give with the same load ? 

OK, so the AGMs are 12 * 200 * 4 = 9.6kwh. Let's ignore for the moment that at 2.5kw you're over C/5 discharge rates and Peukert effect will reduce the useful capacity, and just do a division sum: 3 hours ar 2.5kw, that is 7.5kwh out of the 9.6, that's an 80% DoD (depth of Discharge). You're looking at maybe 400 cycles at this sort of use, maybe even less.

The pylontech will give you 3.5/2.5 = 1.4 hours, that is one hour and 24 minutes. But you generally don't want to take them down to 0% either, so at 90% DoD it's more like an hour and 15 minutes. No significant peukert effect here. Pylontech batteries however doesn't want to be discharged much faster than C/2, so you're discharge rate is a little bit too much for just one module.

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Thank you for your quick reply Plonkster

Did I then calculate correctly : if the load is 1000w the duration would be 3hrs 7 min @ 90% DOD with the Pylontech battery ?

Would it be ok to add a second Pylontech battery a few months later or is it also recommended to have all batteries connected at the same time like the AGM batteries ?

Would you recommend that I rather go for the Pylontech battery than the 4x 200ah Vision AGM batteries ?

Any recommendations who I can contact for installation (electrician)? I am in Bellville, Cape Town.

Thank you very much for all the help.

Edited by DennisD
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38 minutes ago, SilverNodashi said:

A single Pylontech can discharge at 25A which is 1200W at 48V continuously. If this is within your load requirements, the Pylontech will last much much longer than the AGM. 

Slowly I'm looking at alternatives.

Tell me, can I boil a 2000w kettle / use a microwave with another say 400w existing load on, using Pylon's?

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17 hours ago, DennisD said:

Did I then calculate correctly : if the load is 1000w the duration would be 3hrs 7 min @ 90% DOD with the Pylontech battery ?

Yeah. 90% of 3500Wh is 3150Wh. Divide by 1000, that is 3.15 hours, which is 3 hours and 9 minutes. Close enough 🙂

Also, as @SilverNodashi says, look at the max recommended discharge. I believe it is 35A for the 3.5kwh modules, so you're good up to 1.7KW (ish). For the most part, you can use this rule of thumb: Pylontech batteries have C/2 charge and discharge rates, in other words, they want to be charged and discharged no faster than 2 hours. So a 3.5kwh unit can give you a peak of 1.7kw for 2 hours, or any combination as long as multiplying the two numbers yields the total of 3.5 🙂

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17 hours ago, The Terrible Triplett said:

Tell me, can I boil a 2000w kettle / use a microwave with another say 400w existing load on, using Pylon's?

I think what you need to add to the question is how many Pylons you have. I think what you want to ask is if you have two of the smaller pylons (so a total of 50A continuous discharge, or around 2,5kw at 48/50V), what happens if you go slightly over...

Well... nothing. The battery gets a bit hotter, its life is shortened a tiny bit faster than usual, but as long as you don't do this for too long on end, nothing happens. LFP can handle 2C discharges for short periods. If you go too long or do too much, the BMS tells you to stuff off and disconnects everything.

🙂

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1 hour ago, plonkster said:

I think what you need to add to the question is how many Pylons you have. I think what you want to ask is if you have two of the smaller pylons (so a total of 50A continuous discharge, or around 2,5kw at 48/50V), what happens if you go slightly over...

Well... nothing. The battery gets a bit hotter, its life is shortened a tiny bit faster than usual, but as long as you don't do this for too long on end, nothing happens. LFP can handle 2C discharges for short periods. If you go too long or do too much, the BMS tells you to stuff off and disconnects everything.

🙂

Two smaller Pylons = 4.8Kw so the 2Kw kettel will hardly make a difference. That's a draw of about 42A 

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