PINNED - ADD ON PACK Step By Step 30ah Pack build / pictures

[greybeard]

I need some help guys.
My wife just had a spell in hospital and this has made me realise that many of the day to day things I should have been able to manage for myself have become impossible because the chair has lacked the range needed. I need to make an add on pack.

Problems:
I only have dumb 8amp chargers. The charging method needs to be via XLR socket.
I lack the funds for a power supply.
I lack the funds for a PL8.
I am 76 years old and have difficulty understanding and retaining the build information in the lithium build threads even though I read them religiously.
My hands shake too much for reliable soldering, not helped by lacking acute vision in one eye (no parallax for judging distances)

I would be grateful if you could all give me the benefit of your expertise and advise me the best way forward, eg what batteries would be best to give me a usable extra 30 or 40AH over my grp 34 batteries? (grp 24 will not fit in either of my chairs). What is the best place to order them from?

I understand that I will have to incorporate a BMS because of the only charging method open to me. At my age the shorter battery life is not a significant problem.

Shirley has kindly offered to source all the other parts required.

Thanks in advance.

[Burgerman]

Buy 8 cells, of adequate capacity and C rate. The biggest that will fit your battery space. See if you can get it measured to the mm inc height available. Then we will take a look.

Oh. Just realised, addon!
You really want a little more Ah than 30, or a high enough C rate (say 3C cells) for that.

I would allow shirley to send you some 30 to 40Ah cells, he does good tested cells at the right sort of money and about 6 weeks delivery. Slow boat!

[greybeard]

You really want a little more Ah than 30, or a high enough C rate (say 3C cells) for that.

I would allow shirley to send you some 30 to 40Ah cells, he does good tested cells at the right sort of money and about 6 weeks delivery. Slow boat!

Are you still able to supply the cells BM describes, Shirley? I know you advised me to source them myself but having read of the problems Expresso mentions in his 60AH addon thread, I would rather get them from a trusted forum member such as yourself.

[Dan]

Whats your budget @greybeard? 8 60Ah cells are about £500. The pound is a bit weak now.
https://www.aliexpress.com/item/4pcs-3- ... st=ae803_3

8 50Ah cells £520
https://www.dhgate.com/product/tax-free ... _wordrec-6

10 headway 40152s 15ah cells £300
https://www.dhgate.com/product/high-cap ... _wordrec-1

[rickystyx]

So I've ordered myself 16 of the headway 15Ah cels and should get them shortly and will charge them individually and group them after their recharge but -
I'm limited to my hobby charger which will ballance 4s as I now can't afford a different charger as well, so I'm thinking of setting the pack up as 2 x 12v+ batteries of 4s each so that I can happily ballance them and also so that I can put them as seperate packs either side of the chair below the arm rests and just above and slightly infront of the wheels and connecting each one in parrallel to one of the lead bricks. My thinking is that having added wider wheels (6in instead of 3in) having any extra weight there will be better for COG than sticking it behind the chair and also so that I can make seperate charging leads for each 12v pack so that I can use the ballance charger on them as needed (or as I might want to) and so I can fit cell monitors to see what is happening too.
I'm hoping that it may be ok to leave the packs connected to the chair and continue to charge using the MK 8A charger through the normal plug for general use or is that a bad idea?
Will I need to add any voltage protection or anything to the charger at all?
I haven't been able to find a BMS that has 3.65 max voltage protection but is adding a BMS a good idea anyway?
A schottky diode was mentioned in answer to oneof my earlier posts and I haven't a clue about them - I even tried watching some youtube explanations about them which has left me completely baffled - happy to add whatever may be required to keep things happy as long as I don't need to fork out lots of money at the moment - things may change if I can sell my old landrover.
Sorry for asking so many questions - I never thought I'd be doing this in a million years
Richard

[Burgerman]

Good luck. Too many things are guesswork and contradictory there. And your old hobby charger is likely to be useless.

[shirley_hkg]

You may charge the two 12V battery halves with your 4S charger, one by one, every night .

Otherwise , you need 3.65V BMS as you said , but it costs not much cheaper than a PL8.

[ex-Gooserider]

You absolutely MUST use balance wiring and charge with a charger that can do balancing, OR (bad choice, but....) use a BMS so that the pack gets balanced.

Wiring is fairly flexible as long as you understand what you are doing, and end up with the 24V add-on in parallel with the main 24V batteries. As long as you do this and use reasonable technique for your build (heavy enough wiring, good connections,etc.) it doesn't really matter how you get there.

As BM said you may or may not have luck using your low cost hobby charger - most are designed for the much smaller packs used in RC models, and run into issues with large packs - among other concerns their balancing current limit will result in it taking a VERY long time to balance the pack....

The diode is something You-tube and such won't really help with as we are using it a somewhat non-standard way.... In essence diodes have a certain 'voltage drop' across them when they are conducting, the amount of the drop depends on the type of diode. By putting a high power (remember it needs to pass a lot of current) diode in the line between the add on and main batteries, it slightly shifts the balance between which battery supplies more power to the chair so that you pull more power out of the main batteries before the add-on starts 'helping', which results in slightly greater range...

ex-Gooserider

[rickystyx]

it's a very steep learning curve - first learning about the different litium batteries and the different cells then I'm having to learn about the different chargers and their capabilities too - Knowing what you want doesn't mean it is always easy to get what you want - I'm getting there but I haven't played with batteries for years (when ni-cad were all the thing) So I'm slowly learning.
I'm still sticking with making the cells up as two batteries and I'll be borrowing a Hyperion duo charger to charge them until I can fund a powerlab 8 which I'm beginning to see is the only realistic option for charging these packs efficiently. Fortunately I already have a suitable powersupply so won't need that as well. I'll get there as long as people keep on giving me the relevant information - even if it does take a while to sink in (lack of absobtion by my little grey cells - they are too full of other stuff)
Thanks for the help folks
Richard

[Burgerman]

A. the hyperions are not reliable, and I worked for 3 years with the head of hyperion to fix the lead and lithium algorythm on the 14S charger. That is different to all the rest and can do 14 cells. It has reliability issues, and I have a pile of dead ones here. But this firmware with all the mods was only for that one charger.

B. It doesent have adequate cell balance current at 300mA.

C. The DUAL hyperion chargers have common negative terminals. So you cannot charge an 8S pack as there will be smoke. In order to do that you would need 2 SEPERATE chargers without common ground, and 2 seperate power supplies that are floating and the hyperions will be totally seperate.

D. Theres no way to set the termination current on the hyperion, so you will end up with batteries on 3.600v for long periods after charge ends. This isnt ideal for them.

E. they have a Ah limit, that may well cut in and end charge after X time and after X Ah has been added.

This is what I mean when I say most chargers wont work, or wont work properly. And While the firmware was OK when I was helping to stop them doing it wrong, I have no idea what they are doing with their firmware now. It may be that there are a few more traps awaiting you! Such as starting balance too soon as most manufacturers do. Or any number of other things that will cause problems on large packs.

[rickystyx]

Thanks BM - In that case i'll just build the packs up and wait until I can afford the powerlab charger - I have a birthday coming up so I can drop some big hints - I don't want to get it wrong. I don't understand why there is only one company making a decent charger, you would have thought others would have copied it or at leat have brought out their own version.
Cheers
Richard

[Burgerman]

Because primarily they are making LIPO chargers and think they can just do the same at a slightly lower voltage for LiFePO4. And they cant for a bunch of reasons. It works with tiny hobby sized packs, but causes problems on big packs.

I wasnt able to use the PL8 either for LEAD or LiFePO4 for 2 years, until I finally got them to change the PB charge parameters, error voltages, etc, etc, and 4 or 5 of the hidden safety parameters for LiFePO4, hidden problems such as the maximum allowed gap between low and high cells, the point where balancing begins raised to 3.500V, and a few other things. Even then, I have a way of changing the PRESETS to work properly for us on larger packs that is not available in the normal PC software. So you will need to use firmware 3.33, and my profiles (presets) regardless even on the PL8. Things are not as simple as they appear!

[rickystyx]

Whilst still on a high learning curve I came across this - it isn't BMS as such just a balance charging board for each cell - would there be any mileage in using these? https://www.batteryspace.com/Balance-Mo ... -Pack.aspx

[Burgerman]

Only if you charge at around 1.4A absolute maximum.
Meaning a 176Ah battery (many use) will take around 5 to 6 DAYS to charge.

Why?

The balance module will keep each LFP cell’s voltage at 3.60V peak during charging by draining excessive voltage with selectable discharge current (0.65A/ 0.9A/ 1.1A /1.44A. Manufacturer preset at 1.44A

So while charging merrily at say 15 to 40A, one or another cell group will shoot up suddenly as charge reaches the full point, from 3.45V to anything up to 5V or greater, literally in seconds. As soon the first cells becomes full. Almost as suddenly as as filling up 8 glasses of water with 8 hose pipes. Then using a tiny straw as an overflow to stop it overflowing! While the other 7 catch up. So that doesent work...

So in order to hold that cell or cell group down to a safe 3.60V then its balancer will need to be able to sink a 15 to 40A current - whatever charge rate you choose! Or it must be able to slow down the charge RATE (amps) by throttling the charger proportionally, to less than the BMS balance current being used. Thats what the PL8 does.

A full BMS does the same thing. Only usually at even lower balance current like just 100mA. At 3.60V it adds a 100mA load/drain to the cell. To try and balance the high voltage cell downwards. When that has almost no affect (as you are charging at 40A), a cell reaches 3.85 to 4V which happens very fast (or often even higher). So it then also then DISCONNECTS the charger completely via a mosfet, and waits till the high cells sees 3.50V and then reconnects the charger all over again. And it does this over and over and over while the dismally low balance current attempts to pull the high cell down. Sometimes for days. This is ONE reason that typical BMS murders your cells. Theres others too.

[rickystyx]

I only start to understand these things by asking my daft questions - still learning

[Burgerman]

On 99% of forums, and utube, and other places that discuss lithium bateries they are still asking daft questions because the experts are all clueless. Its the blind leading the blind. Utube same! Quite entertaining to hear their ignorance. Even battery suppliers. All think a BMS is an essential thing. Theres expensive ones, BT ones, advanced programmable ones etc. NON of them are required in a properly implemented system. And if they are, and the cell protection systems, actually cut in, you already have other problems. And as far as charging is concerned all of them do a much worse job than the PL8.

[rickystyx]

I'm convinced - the more you look at the information available and then look at the actual requirements there does appear to be a massive gap. Most of the Lifepo4 BMS systems advertised appear to be woring at a much higher than safe cell protection voltage and as you have pointed out have this on off issue built in. I'm now on a fundraising mission for the PL8 and I'll keep myself busy for a few days building the pack as my cells will be arriving in a couple of hours. I can already see this growing into a full pack build before long - at least I wont need to buy another charger once I've got the PL8 (at least I hope I won't) I think it is time to shut the laptop and take the chair out for a spin I'm getting restless
Ric

[Dan]

I had an extra headway 40152s 15ah cell sitting in its box for almost two years. I charged it up it then discharged it down to 3V I got just over 14Ah out of it.
I guess thats OK for a cell thats been sitting for two years?

[Burgerman]

Its OK. If you discharge to 2.5V, and cycle it a couple of times it will give the full 15Ah probably.

15Ah is from a fully charged 3.650V - sat at CV until 1000th C and then discharged at 25 centigrade at .2 to .3C down to 2.500V.

So 14Ah from a 3.600V to 3V, and 20C? is about right. Cells stored for a long time without excersize tend to improve with a few cycles too.

[Irving]

I had an extra headway 40152s 15ah cell sitting in its box for almost two years. I charged it up it then discharged it down to 3V I got just over 14Ah out of it.
I guess thats OK for a cell thats been sitting for two years?

My 40152s have been similarly sitting around. After some use they have improved from 15Ah (3.65v down to 2.9v) to 17Ah

[Burgerman]

They actually have a calender life of at least a decade, if stored between 30 and 70% charged and kept cool. Maybe a fair bit longer. As long as quality cells and few impurities or water. If assembled in a humid basement for e.g. instead of a dehumidified room, they will die faster. So best to stick to known manufacturers or well tested known cells.

[ICEUK]

Hi all, are these batteries ok 176amp? Are there any better batteries or more credible source? Its for my jive,

http://m.rj-lithium.com/sale-11546471d- ... ttery.html

[Burgerman]

Those batteries are VARIOUS capacities.

There are some there that should fit, (measure) that are 176 AMP HOUR. Not Amp.

An Amp is a measure of current.
An Ah or AMP HOUR is the measure of capacity. A 176AH battery can give 176A for 1 hour. Or double that for 30 mins. Or 1A for 176 hours. etc.

A good source? Several here have used them without issues.

Remember that they will need a mm or so of insulation between each cell.

[Irving]

Hi all, are these batteries ok 176amp? Are there any better batteries or more credible source? Its for my jive,

http://m.rj-lithium.com/sale-11546471d- ... ttery.html

Hey ICE, did you get a price yet?

I'm thinking of getting some too. Maybe there's an opportunity to do a bulk buy and get better pricing?

[ICEUK]

Best price i got out of them was $1118, delivery all taxes and duties paid. They should. Fit i got a pair of batteries Length (mm) 259 Width (mm) 168. Height (mm) 212.5 and they are a tight fit. I coild ask if they will do better deal if we got 16.

[steves1977uk]

I will be after 8 176Ah cells too for my Groove chair I'm getting help with to get it in working order. It'd be cheaper to do a bulk order I would think.

Steve

[Irving]

Best price i got out of them was $1118, delivery all taxes and duties paid. They should. Fit i got a pair of batteries Length (mm) 259 Width (mm) 168. Height (mm) 212.5 and they are a tight fit. I coild ask if they will do better deal if we got 16.

Hmm £938 ish.

My battery tray takes 2 X sonnenschein 74ah 278L X 174W X 190H with a 4mm spacer to the sides and a 10mm spacer between, gives a footprint of 282W X 358L X 190 high. So 8 X 176Ah fits easily and 8 X 200Ah will be a squeeze but might be possible.

[Burgerman]

Hmm £938 ish.
My battery tray takes 2 X sonnenschein 74ah

At best, you discharge aroung 40-Ah from the 74Ah sonnenschein batts before you grind to a halt.
They are then approx 400 pounds UK, Divided by 40Ah = 10 pounds per Ah.


The 176Ah lithium is all usable. But lets be nice to them, and leave you a safe reserve. Call them 160Ah batteries. For 938 pounds. So 5.85p per Ah.

So lithium is HALF the cost per Ah than gel. Approx.
Your lead lasts 9 months discharged to that level at best. The lithium a decade. So lets say 10x as long.

Now that lithium is 58p per Ah, instead of 10 pounds per Ah over 10 years. And some of mine are 10 years old, and still almost as new.

So lead is actually 16x more expensive...
If you swap 176Ah for your 74Ah batteries, it will not be 16x cheaper, but only about 7 or 8x cheaper over a decade. But it will be for 4x or 5x the range!

I cant afford lead.

[Irving]

Hmm £938 ish.
My battery tray takes 2 X sonnenschein 74ah

I'm well aware of the economics! It's more a case of do I buy a set of prismatics or stick with my 75Ah headway pack (which I bought 18m ago but only deployed a month or so back). I suppose I could sell them, or keep them for the backup chair. The money isn't an issue directly but it's the effort of doing it all again...

[ICEUK]

They said if we were to order 32. 175ah lithium cells we would get a 10% discount. I personnally dont think its worth it, as we still have to ship them within uk to other members.