Pylontech in parallel with generic Lifepo4

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max-payne asked Mar 15, '24

Pylontech in parallel with generic Lifepo4

I wanted to show you that pylontech system in parallel with a generic (15s!) lifepo4 system is totally possible. Both Daly and JK Active BMS.

3 Batteries are connected to a Lynx Distributor and all 3 Multiplus are as well.
1x JK 1x Daly and 1x pylontech US5000.

I wanted to comment on the lifepo4 linearity for example with 80A continuous at 50.50v for 90minutes increased the voltage to 50.60v today. So 0.1V accross 15 cells! and 4kwh absorbed.

The currents split themselves from the Distributor to the battery packs according to the kwh installed. So the bigger batteries get more current.

Having paid 55€ per 305Ah cell grade A I wonder what the disadvantage of my setup is. It is clear that the pylontech warranty is voided. But I quite like the setup of having a main BMS (pylontech) which limits the current to 80amps and the "dumb" batteries run in parallel being watched by their own BMS.

Am I missing something?

ESS Pylontech lifepo

1710507232968.png (86.4 KiB)

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Michelle Konzack commented · Mar 15 at 01:13 PM

Where did you get the cells for this price?

I need 64 cells of this size for my DIY EV (it is a Mini-Truck N1 using a MultiPlus-II 48/10000)

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max-payne Michelle Konzack commented · Mar 15 at 02:51 PM

NKon.nl with german 0% VAT.

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Michelle Konzack max-payne commented · Mar 15 at 06:02 PM

64 Eve LF304 A-Grade with delivery time roughly 80 days to Estonia:

Grand Total

€5,363.94

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Michelle Konzack Michelle Konzack commented · Mar 15 at 06:41 PM

Hmmm, even with 4 JK Smart BMS 200A I am still at 6104€.

I think, I will order from them.

Can not get the cells cheaper in Estona.

P.S.: I use in the EV a GoldenMotor with 20kW which is enough to drive 80km/h with 3,5t plus 2,8t Trailer (in theorie, because nobody pack a BobCAT on a trailer and try a racing)

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max-payne Michelle Konzack commented · Mar 15 at 07:07 PM

62Kwh of Lifepo4 for same price as 10kwh Pylontech.

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Al commented · Mar 16 at 12:33 PM

Well done so far.

50.5V is only 3.36V per cell, having them all within 100mV in the flat part of an LFP charge curve is normal or even a bit high, it's when they reach above 3.4V-3.5V and the deviation is less than <10-30mV you can be happy.

I have three an 8s (25.6V) DIY batteries in parallel and see 10-20mV deviation when charging with 180a - 250a across all 24 cells up to around 3.46V per cell, then if they're unbalanced, deviation can get up to around 100mV until they re-balance to <10mV during absorption.

There are a couple of people on the Camelot forum who have 15s DIY LFP banks in parallel with Pylontech and they seem happy, so it's perfectly possible to get it running nicely once they're all balanced.

Personally I don't like the idea of no communication between the DIY and VenusOS for cell OV and UV alarms or call for charge current. Only the Pylontechs can communicate and control charge settings. It shouldn't be an issue though as long as the DIY BMS's charging setpoints, OV + UV alarms and cutoff points are set properly and protect the DIY bank in case of an problem.

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Answer 1 · 2024-03-15T19:39:38Z

Michelle Konzack answered · Mar 15 at 07:39 PM

or 600kWh compared to an EV Battery!

Hahaha, 25-60k Euro for 100kWh. They are simply sick!

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Answer 2 · 2024-03-16T08:30:08Z

lee-taylor answered · Mar 16 at 08:30 AM

This is something I am interested in trying on my main system. I already do something similar with a 12V setup that was using a Renogy battery with inbuilt bms. I added a pair of Pylontech 12V batteries and this kind of works, albeit the Renogy discharges faster than the Pylontechs. My main setup has four Pylontech batteries, in hindsight I should have bought generic 16s batteries as Pylontech ones are expensive for what they do. I might give this a go as It would be a cost effective way to increase storage.

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max-payne commented · Mar 17 at 07:00 PM

I have seen some people go for a 18s system with victron. Since everything in a 48V multiplus can be configured up to 63V / 18 = 3.5V (100% anyways).

If I built a new system from scratch thats what I would do nowadays.

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Answer 3 · 2024-03-16T09:16:48Z

nickdb answered · Mar 16 at 09:16 AM

Don't jinx yourself. You can only declare victory after a few years of happy, stable running.

There are cheap batteries and there are good, long lasting ones, everything has a compromise.

I don't see the point in buying a commercial battery to only void the warranty, if you want to DIY, just DIY.

You will see many posts from DIY builds that have run into problem, it comes with the territory when you choose to go down the untested route.

Be sure those cells you bought are all from the same batch, are the same age etc.

it just takes one to be iffy to throw off a system, then you don't have warranty or support to fall back on.

Most of us just want the reassurance that it will last, that software updates won't break the stability of the system and if something does happen in the 10 year life that we don't have to reach into our pockets. For a reasonable amount extra, for me, it just isn't worth the effort to make your own.

It is worth remembering that a commercial 300AH battery pack, has a fair bit more capacity in the pack, as it is derated to provide longevity.

There are many self builds out there with happy owners, each to their own, but I would skip the hybrid route, it is just an unnecessary complication.

But thanks for sharing, and expect a few chirps if the next post is about a system having a speed wobble ;)

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max-payne commented · Mar 17 at 06:59 PM

Oh the system is pushing 2 years in summer. So no problems yet.

Hard part is connecting the system first time. All batteries have to have the same voltage and SOC there is no auto current limit like with pylontech.

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Michelle Konzack commented · Mar 18 at 11:16 AM

I fully agree with your comment.

This why I run into financial problems with my EV Battery, since I need 16S but 1200Ah (60kWh) in one go.

If you have not the money to buy them in one go and from the same batch, let it be and wait for a better opportunity or a Lotto-Win.

I have currently for experimenting 2 Sets of 320AH (8S for a 24V System) using the DalyBMS 200A with Balancer and CAN controller and even if it should work from scratch, I have problems keeping two Batteries parallel in sync.

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