14S100P+1

chuckp

chuckp

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Jul 29, 2018
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Hi guys

Sorry for another noob question that has most probably been asked before.

Thinking is a 14S100P/120P pack system with a 15th pack as a backup for maintenance proposes,
Planning on using a Batrium bms.

Has anyone come up with a way of connectinga spare pack that stays balanced with the 14S in already to swap out condition?

Thanks

Chuck.
 
Have been thinking of something like that, more of a extra pack connected to one of the14 main packs for a few minutes and then move on to the next pack...
So it will have always a kind of same charge as the main packs ... get it? :)

But never finished it... :https://secondlifestorage.com/showthread.php?tid=4683
 
The only way I can think of the extra pack being connected without interfering with everything else, is to have 2 sets of diodes on the terminals so that it can only "take" a charge, but not discharge. The Batrium would then bleed off any extra if need be.

Problem is the diodes have forward voltage drop which could effect the Batrium readings.

I don't know if the packs "have" to be connected to the string for Batrium to tend to it, or not. I am guessing not as you can have several strings all tied together with the longmons (if I understand the installation process correctly)

I'm sure daromer will bring his knowledge of Batrium to the table as he has several units and varying configurations
 
Personally I would just take that 15th pack, charge it to 3.7v its nominal storage voltage, and store it. I don't see the point of cycling something that isn't even being used all while adding additional complexity and monitoring to something that is a standby maintenance item for a "what if" scenario.

If you don't want any downtime then you should consider two separate banks in running parallel with a A, B, A+B combiner switch between two banks. Normal operation running in A+B in parallel. If you do isolate, you only need to get the voltage close enough before combining and allowing both to equalize. With a simple clamp meter, easy to keep an eye on things when flipping the switch.
 
Let the pack sit at a voltage that is most common for your powerwall. There is no way (easy) way to have it in the system all the time and balanced to be swapped out. There is no use for it either.

Thing is when swapping out the pack you need 2 min downtime and the voltage as such is not that important. As long as that pack isnt way off.
I have been doing this since many many many years and 3 years in the solar service now.

Batrium: Batrium does not care of if the pack is connected or not so yes you can have a 15th longmon hooked to it just for monitoring if you want. I dont the reason why you would want it though.
 
I'm looking to do the same thing for mine. I was planning to keep the spare completely separate and able to be charged separately to about 4.0v. A few extra long mons on it to quickly balance when needed. Once charged, unlikely to need much maintenance.

Any ideas on an adjustable voltage reasonably cheap charger suitable for a single pack?
 
JohnAllen said:
I'm looking to do the same thing for mine. I was planning to keep the spare completely separate and able to be charged separately to about 4.0v. A few extra long mons on it to quickly balance when needed. Once charged, unlikely to need much maintenance.

Any ideas on an adjustable voltage reasonably cheap charger suitable for a single pack?
Click to expand...

You are best off keeping the pack at storage voltage. Cells degrade far more slowly at storage voltage, about 3.75v.


As for a cheap charger for a single pack, it depends on how many amps you need. You could just parallel up a collection of TP4056, to the required amps. Otherwise you could use an RC charger (such as the imax b6). It depends on what you have on hand, and how much you want to spend.
 
Any CC/CV psu will work fine. I personally use my iCharger but an DPS unit works fine too (DPS is the first letters of a digital small very cute CC/CV thing)
 
wim said:
Have been thinking of something like that, more of a extra pack connected to one of the14 main packs for a few minutes and then move on to the next pack...
So it will have always a kind of same charge as the main packs ... get it? :)

But never finished it... :https://secondlifestorage.com/showthread.php?tid=4683
Click to expand...

Interesting idea.

I was looking for something that would be as simple as possible.

Reading through all the other comments I guess the best idea would be to just keep a pack at 3.7V as a standby to keep it simple.

I think still usean earlier idea of fitting a contactor to the pack terminals to switch the supply across a fused resistor when first swapping out packs. Should help with the current surge.

Thanks guys.
 
So I have 350W PC PSU kicking around that I'm thinking of using to charge up my individual packs and then do a discharge check and recharge prior to building the powerwall. What would be a good cccv module to use to control the charge rate on say a 120p pack?

Would I charged the pack to 3.75V or 4.2V prior to building the wall?

Thanks
 
chuckp said:
So I have 350W PC PSU kicking around that I'm thinking of using to charge up my individual packs and then do a discharge check and recharge prior to building the powerwall. What would be a good cccv module to use to control the charge rate on say a 120p pack?

Would I charged the pack to 3.75V or 4.2V prior to building the wall?

Thanks
Click to expand...

You can do testing on each individual pack, but before making the powerwall I would connect EVERYTHING in parallel and let it sit for a couple days and allow it to equalize... if you have a DC clamp meter you can easily use it check the movement between packs to see when it's done...

For discharge, a shunt and a load works well... just make sure you have something to disconnect the load if you are leaving it unattended.

As far as a CC/CV for larger packs, I use a large hobby charger that is capable of about 70 amps.Really depends on how much cash and current you want to throw at this thing. Plenty of options out there.
 
CrimpDaddy said:
As far as a CC/CV for larger packs, I use a large hobby charger that is capable of about 70 amps.Really depends on how much cash and current you want to throw at this thing. Plenty of options out there.
Click to expand...

What voltage cc/cv supply are you using for the 14S pack? I was looking at only charging to 4.0v

Should I get a supply that charges to each cell to 4.2v and use a BMS to cutt-off the charge when 4.0V is reached?

thus 14*4.2=58.8v?
 
@Bubba

Personally I don't/won't use a BMS to limit my top end charge, I use it as my last line of defense.

If I am not using a hobby charger, I use a Victron MPPT. Both options allow me to dial in the exact voltage I want.
14 x 4.1 = 57.4
7 x 4.1 = 28.7

It very much depends on which system or battery pack I have, but generally speaking I charge to about 4.1v

The current depends on the size of the pack, but for my larger stuff I dont have a charger big enough to even stress the cells.

Not all my system use a BMS either (EV batteries), but on those systems I charger closer to 4.0 on the top end and bottom balance the cells which seems to work out better for me because I don't charge to the top.
 
I'm planning on changing to 4.05V and discharge to 3.35V.
The inverter charger I'm looking at getting will also let me set the charge/discharge voltage and also set the charge/discharge rate from 20A to 60A.

For my first string I'll set it to 20A, as I'm building 40P packs that will be 500mA per cell, once the second string gets connected I'll up it to 40A and then the 60A max once the third and fourth strings are connected. In theory once all four strings are connected i will never charge or discharge at more than 375mA per cell and with the Batrium cell voltage range set at 4.05V to 3.35V hopefully this will give me plenty of cycles and a reasonable life span. Assuming that I'm getting all this correct.
 
Hey chuckp, what charger are you looking at that is adjustable.?
On my end I need to also find one that is CSA or CUL rated.
 
Bubba said:
Hey chuckp, what charger are you looking at that is adjustable.?
On my end I need to also find one that is CSA or CUL rated.
Click to expand...

Hi Bubba

Planning on using aSofar Mass Energy ME3000SP AC coupled grid tied bi?directional inverter/charger.

I'm in the UK and have a 230V single phase supply with time of use tariff, this inverter/charger will work with my grid tied micro inverters and also give me the ability to charge the batteries from the off peak tariff if needed.

The Batrium will also be connected in to control the charging cycle.
 
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