New build moving away from lead acid… what a nightmare they are!


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Spookyduckling

New member
Joined
Dec 16, 2021
Messages
3
Hi everyone,

I am currently moving away from 26KW lead acid 48v solution and have now purchased 650 x 3.7v - 2600mah - 7.8amp 18650’s (new). I have 3.7kw of solar panels and a 48v mppt controller that is also capable of Charing from mains (cheap rate elec storage) :) The mppt can charge at max 60A and I have access to every size cable so I’m currently using 50mm2 for everything but this will change for the new battery packs…so…

Questions:
1) I am thinking that I should pop them into 10p 13s for 48.1v and have 5 packs, or I could do 5p 13s and have 10 packs….
2) charging 5 packs would be 15A each pack or 10 packs would be 7.5A - what BMS would you recommend in this situation?
3) should I put inline fuses for each pack of batteries From the BMS to the BusBar?
4) Does a BMS need to have separate charge points or can a BMS use the same Pos and Neg for use age and charge..?

I think that’s all the questions I have right now…. The batteries turned up this morning and they look great! I’m doing this as my lead acid are just crap… but I had to learn the hard way didn’t i! Stupid me!

cheers
Spooky.
 

Wolf

Active member
Joined
Sep 25, 2018
Messages
1,693
I still have my 210Ah (10kWh) lead acids as an emergency backup. Especially in the winter time. I can charge them below 0°C without a problem and since they basically sit in maintenance mode are not deteriorating as quickly.

I would go with 14s XXp as most quality inverters will handle up to 60V. Not that I recommend running the cells at 4.2V (58.8V) anyway but closer to a max of 4.05V and a min of 3.45V. This range encourages longevity of the cells and gives you the best power band. Voltages above and below these numbers stress the cells and there really isn't that much power above or below those limits.

Place fuses and or breakers wherever you think it is necessary. I run cell level fuse sheets on both the pos and neg side of the cell packs and then use a breaker on each battery pack (14s80p) and finally a main breaker on the whole battery 14s80p X 4.
The BMS is only there to make sure all packs are relatively equal in voltage (and if necessary burn off extra energy on high voltage > than a preset voltage packs) and if there is a problem to shut the system down.


Wolf
 

floydR

Member
Joined
Aug 23, 2017
Messages
1,443
Listen to Wolf he is one of the most knowledgeable people here read his threads.Your current LA bank is 500 Ah? 250ah usable? you want to replace it with 3.7v 2600mAh 18650's 14s is the way to go. 14s100p would give you 260 Ah battery 14s200p would give you 520 Ah. The 100p back might be manageable. With the cells you have you can start with 14s40p, 5 banks of 14s40p would give you 14s200p. The defacto standard size of most 18650 based modules is 80p. You need at least 470 more cells to make a 14s80p battery bank.
later floyd
 

Spookyduckling

New member
Joined
Dec 16, 2021
Messages
3
I still have my 210Ah (10kWh) lead acids as an emergency backup. Especially in the winter time. I can charge them below 0°C without a problem and since they basically sit in maintenance mode are not deteriorating as quickly.

I would go with 14s XXp as most quality inverters will handle up to 60V. Not that I recommend running the cells at 4.2V (58.8V) anyway but closer to a max of 4.05V and a min of 3.45V. This range encourages longevity of the cells and gives you the best power band. Voltages above and below these numbers stress the cells and there really isn't that much power above or below those limits.

Place fuses and or breakers wherever you think it is necessary. I run cell level fuse sheets on both the pos and neg side of the cell packs and then use a breaker on each battery pack (14s80p) and finally a main breaker on the whole battery 14s80p X 4.
The BMS is only there to make sure all packs are relatively equal in voltage (and if necessary burn off extra energy on high voltage > than a preset voltage packs) and if there is a problem to shut the system down.


Wolf
Hi Wolf,

Thanks for taking the time to reply.
I want to move away from my lead acid as they are essentially knackered. I have 4 x 110ah 12v in series x5 giving 550ah. I have never been able to charge them to 100% (85% max) and after having them running for over a year all I get out of them now from a full charge from the mains is 3.5kw. I got them from advancedbatterysupplies and spen a fortune on them. I wish I had gone with lithium in the first place but you live and learn don’t you.
My inverter I’m on now is MPP solar hybrid 5kva, nice as i charge my batts off peak with cheap elec and use it during the day with solar panels as well.

im still looking for a BMS as it’s the only component I have not bought yet - do you have any recommendations?

many thanks
 

Oberfail

Member
Joined
Jun 22, 2021
Messages
241
Stuarts DIY BMS has a big community around it, but its hard to get your hands on it due to the chip supply shortage.
Batrium is super expensive, the support rather meh but its not a bad BMS.
JKBMS is affordable and in stock, the community is rather small but there are some tools for it and it may grow due to the affordable price & availibility.
 

italianuser

Member
Joined
Feb 25, 2020
Messages
478
Hi there, Spookyd, yes 14S is the Lithium version of 48V batteries. Check your inverter voltage range, most probably a 14S will be ok for the inverter, but do check the datasheet.

For BMS choice you must consider: both the current you will use to charge batteries and the current your load requires. And you get the maximum of the two, double the number and then start choosing BMS. It's a good idea buying a BMS double of the maximum amps you want to handle so the device will normally work around 50% load which is good for many reasons. So if you think you'll be charging at 60A, then a 120A BMS (even 100A) would be a good choice.

Wolf, Floyd and Oberfail's answers are surely good.

> 1) I am thinking that I should pop them into 10p 13s for 48.1v and have 5 packs, or I could do 5p 13s and have 10 packs….
14S ok.

> 2) charging 5 packs would be 15A each pack or 10 packs would be 7.5A - what BMS would you recommend in this situation?
I would avoid the cheapest and the most expensive ones. And get double the Amps you need.

> 3) should I put inline fuses for each pack of batteries From the BMS to the BusBar?
I always thought of putting fuses, 100%. But... now I'm getting near to days I'll be mounting and I might avoid individual cell fuses at all... At pack level absolutely a good idea to have them.

> 4) Does a BMS need to have separate charge points or can a BMS use the same Pos and Neg for use age and charge..?
Mine use same cables. I bought these Daly for my 14S20P batteries. I bought an extra one in case one brakes. It's not a smart BMS, I would have liked all that extra monitoring but price was too high for my budget.

DALY 40A-20A BMS.jpeg
 

Spookyduckling

New member
Joined
Dec 16, 2021
Messages
3
Hi there, Spookyd, yes 14S is the Lithium version of 48V batteries. Check your inverter voltage range, most probably a 14S will be ok for the inverter, but do check the datasheet.

For BMS choice you must consider: both the current you will use to charge batteries and the current your load requires. And you get the maximum of the two, double the number and then start choosing BMS. It's a good idea buying a BMS double of the maximum amps you want to handle so the device will normally work around 50% load which is good for many reasons. So if you think you'll be charging at 60A, then a 120A BMS (even 100A) would be a good choice.

Wolf, Floyd and Oberfail's answers are surely good.

> 1) I am thinking that I should pop them into 10p 13s for 48.1v and have 5 packs, or I could do 5p 13s and have 10 packs….
14S ok.

> 2) charging 5 packs would be 15A each pack or 10 packs would be 7.5A - what BMS would you recommend in this situation?
I would avoid the cheapest and the most expensive ones. And get double the Amps you need.

> 3) should I put inline fuses for each pack of batteries From the BMS to the BusBar?
I always thought of putting fuses, 100%. But... now I'm getting near to days I'll be mounting and I might avoid individual cell fuses at all... At pack level absolutely a good idea to have them.

> 4) Does a BMS need to have separate charge points or can a BMS use the same Pos and Neg for use age and charge..?
Mine use same cables. I bought these Daly for my 14S20P batteries. I bought an extra one in case one brakes. It's not a smart BMS, I would have liked all that extra monitoring but price was too high for my budget.

View attachment 26636
 

Wolf

Active member
Joined
Sep 25, 2018
Messages
1,693
I have never been able to charge them to 100% (85% max) and after having them running for over a year all I get out of them now from a full charge from the mains is 3.5kw
I am slightly confused. (Not that it takes a lot) I see several style 110Ah batteries from Advanced Battery Supplies and am wondering what type you got AGM or Leisure or another style. Also why you are only able to charge to 85% and from a full charge from the mains? (85% or 100%) you are only getting 3.5kWh. Believe you me I am no advocate of Pb batteries and I do understand their issues but something is wrong here. At a guess you spent £150.00 per battery 4 X 5 = 20 = 3000.00 Quid. Quite a respectable deduction from the pocketbook:cry:.
550Ah (26 kWh) in Pb terms is really only ≈ 225Ah (10kWh) unless you want to treat your Pb batteries to a very short lifespan, and those numbers are only in the best of circumstances. But only 3.5 kWh has me scratching my head.

1639745711534.png
Can you post a picture of your battery bank? I am curious. Here is mine.
1639746306883.png
All this being said I applaud your decision to go with Li-Ion. The usable energy is far greater in a much smaller package although that package can grow considerable due to the addictive nature of making and storing your own power. We always want more.
I am now thinking 14s80p X 4 hmm is it really enough.............:unsure:
1639746683787.png
So as far as BMS is concerned......
I run a Batrium BMS. I say that with reservation as the purchasing and installation was relatively easy. Cost well yea its expensive. I have spent AUD $2619.32 on my Batrium BMS and fortunately I am done for now. I will purchase another 14 longmons for AUD $369.73 just as spares for in the future in case I have longmont failures which Batrium claims is due to exces bypass. Not so! As I go into bypass maybe twice a year and then only for a very short period of time and I limit the longmont bypass temp to 55°C. Support and warranty questions are touch and go. If I spend this kind of money I do expect to be able to discuss a potential warranty problem and get it resolved quickly. For some reason it always is the users fault and then if you are willing to "pay for support" a teamviewer meeting to discuss what may be wrong. There are NO electronic parts that are 100% reliable and failures do occur. Communication with Batrium is an unfortunate ½ Star 1639747785579.png and the product I would rate at 1639747934849.png3.9 out of 5 Stars. OK enough ranting. You are here to get educated.

If I were to do it again I would go with Stuarts DIY BMS. There I can talk directly to the warranty department. ME! I would also recommend it if you are electronically capable and know which end a soldering iron gets hot. You get to build and program the BMS and in the process understand the principles and operation of it all. The only issue is that you have to build it and that does take some time. Matter of fact I am seriously considering building one just because.

I am more inclined to go with a passive BMS than an active one. In your case it probably doesn't matter as much as you are using new cells.
Even with used cells if the packs are built proper there should be very little passive or for that matter of fact active balancing going on. If you are constantly dependant on the balance function of a BMS to keep your packs in line you have some major problems that need resolving.
I reiterate again a properly built battery with properly built packs will require a minimum of interaction from the BMS. It is the watchguard in case there is a potential catastrophic failure in sight, will sound an alarm, then gracefully shut the system down before any serious damage can occur.


I am not necessarily opposed to the "Smart BMS's" Daly, JK BMS, etc. You name them they are out there most all will have Bluetooth, or some communication protocol for you to program and or monitor it. In my case I like to have instant access to my systems parameters and adjust if necessary no matter where in the world I am and I cannot do that with bluetooth. There are many communities (SLS included) out there that have written interfaces for these "Smart BMS's" using Linux, RasPi, Python etc. so you can forward these parameters to Node-Red, Influx, and Grafana etc.
The world is your oyster.

Wolf
 
Last edited:

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
2,032
Agree with your assessment of Batrium - although my problems are a bit different. I've not had any longmon failures out of the 100 I have in operation - but rather some longmon cabling and Shunt SoC issues. At least once a year I have to 'wiggle' the cables (I'm narrowing in the bad one) because the network stops and twice this year I've had the Shunt 'jump' to 0% SoC for no good reason which requires manual intervention.

The problem with Stuarts DIY BMS is just the entry level. I've been following @Adam Welch youtube for years now - and it just a level of knowlege that I'm not willing to invest in - although I certainly get it! Lately it seems like you can buy the units fully assembled? but still the process of making them operational is more detailed that Batrium.

I absolutely *love* the 'central unit' with external/cell level monitor/balance design as apposed to traditional 14s/16s BMSs which is common to both Batrium and Stuarts - and found that invaluable to enable gradually adding more and more 'batteries' to the battery bank over the course of several years.

Are there any others with central processing / remote units?
 

floydR

Member
Joined
Aug 23, 2017
Messages
1,443
Are there any others with central processing / remote units?

REC BMS Master – Slave configuration is suitable for higher voltage systems. It allows to connect up to 240 cells in series and it’s compatible with all REC BMS products. https://www.rec-bms.com/battery-management-system/


https://www.elithion.com/lithiumate.php

There are more out there.
Later floyd
 
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