80Ah ADD ON build

[expresso]

I just got my new 80ah Cells - not bad looking - i will start the charge soon and hopefully i cross my fingers they are all in good shape when put together as a pack - they fit perfect in my plastic shoe box i been using - this time i dont have to cut to extend it - more than enough room to fit width wise - tall wise - they are maxed out - i wont be able to use the cover without adding a inch or so higher - i will figure something out .

took about 2 weeks to receive - the only thing i dont like is the connectors they gave me - they are very thin if you ask me and not sure they are good enough using - unless maybe if i double up on them or triple if i have enough of them - not sure if thats a good idea or just waste of time - i may just end up making cables like i did before - much more robust.

i will post more pictures as i go along but to be honest it wont be much difference than my previous 60ah built - same thing only larger Cells this time - thinner but taller - and 80ah !!! this will be going on my new chair bounder - when all said and done - i will have 180ah on it - and i need it all since its a gas guzzler for sure -

i hope to get at least 40 miles safely when all said and done. -

[expresso]

Connectors i received - too bad i feel they are too thin to use - i may be wrong ? or i can try to double up on them ?

[expresso]

This is the Diode cable i am making for Quickies Chair for her ADD ON pack - two diodes in line - hopefully this will work out good for her to give her the best range with her smaller pack and lead - i know for a fact one diode works - - this is the first time i am trying two of them -

anyone who wants to make an ADD ON to use with Lead - should at least use one diode inline to get the best range. only use a diode if you are combing lithium with lead - if all lithium - no need for one.

Pizza time

[BugBayMx]

Try to explain, as easy as possible, the photos will be of great help to me, I will be attentive to your tutorial, I want to make my rides longer, thanks.

[expresso]

viewtopic.php?f=2&t=6873

you can start here - this i think is step by step for the most part should be good to follow - and also this -

viewtopic.php?f=2&t=8023

more or less same idea - just larger cells being used - i am always learning also - and like you - i like it in simple easy terms - with pictures - helps me alot and i hope it helps others also - i try my best to answer - i am sure BM will jump in - and i would follow what he suggests and dont worry - you can do it also

[shirley_hkg]

Seems the connecting holes are not original . May be hand tapped by seller . Don't tighten it too hard .

[expresso]

yeah i noticed that the screws dont screw all the way down - theres a small gap - they dont go all the way down flat - either i use a shorter screw on top or i can add a few washers to fill the gap on the ones i dont have cables on. i think with the cables rings - they would fill the gap and should be fine.

do you think its Ok to use washers to fill the gap ? or try to find shorter screws ? or just dont tighten all the way and leave it alone with a small gap - would use locktite

what do you think is best way , easiest way is just add a few washers to fill the gap and thats it - is that considered a M8 screw ?

[expresso]

What about those connectors ? they are thin - i dont feel they are thick enough - to use - am i wrong or can i double up on them ?

if not i will just make new cables like i did with the 60ah Cells - in that case that would fill the gap and the screws should be good then with no washers

i am not going to rush to make this - but want to get it going and hope they are all good - crossing fingers - - and last - will replace weak cell from the 60ah pack - i got the seller to send me another one - and i used the same seller for these Cells -

[shirley_hkg]

That copper connector can handle a thousand amp . Don't worry .

Add teeth lock washer as cushion . Apply Loctite and don't over-tighten it.

[Scooterman]

Connectors i received - too bad i feel they are too thin to use - i may be wrong ?

If you have a metric micrometer you could measure the thickness of the link and multiply it by the width to give you the csa in mm2.

A solid copper core/link can carry more current than an equivalent mm2 stranded core. At least that's what the IEE wiring regs used to say...

[Scooterman]

i will post more pictures as i go along but to be honest it wont be much difference than my previous 60ah built - same thing only larger Cells this time - thinner but taller - and 80ah !!!
-

I'm really interested in this build Expresso, so if you can detail each step I for one would really appreciate it .

As well as the physical build can you detail the non-physical initial charging, voltage graphs, etc, for people like me who've never done lithium before but plan to, and using prismatic cells. (for me not an add-on but a lead replacement on my road mob scooter)

[Burgerman]

Still think 2 diodes MAY be a bit much. But if so, easy to remove 1 with tools! Do those bus bars allow room for cell insulation?

[Scooterman]

anyone who wants to make an ADD ON to use with Lead - should at least use one diode inline to get the best range. only use a diode if you are combing lithium with lead - if all lithium - no need for one.

Hi, I've scanned through your 30Ah build but can't find the reason why you recommend using a diode with an add-on pack? I'm guessing it's something to do with lithium and lead being different battery technologies connected in parallel???

[shirley_hkg]

One way to ease your worry about over-stressing a low C add-on is to put a diode in its discharge path .

-0.6V will match the discharge platform of MK gel perfectly .

Didn't you hear BM mentioned before ?

[Burgerman]

In a perfect world. the addon would be the same voltage as the lead. But its slightly higher. So as you drive the first 1/3rd of your miles come ONLY from the addon. It takes all the load. So lets say you have 60mile range.

After 20 miles, the lead is still 100% full. The addon is half discharged.
After 40 miles, the lithium is about 80% used, and the lead about 20...
Keep going and you run the lithium too low, and the lead still has some remaining but you must stop.

Add a high power low resistance low voltage drop forward diode, with around a .25V approx drop. Now the lithium is used less, the lead more, by around 15 to 20%. SAdd 2 and you will use all the lead, and may have some lithium left. Ideally you need somewhere between the two. Expresso is experimenting to see what works best. 1 or 2 of those diodes.

[Scooterman]

In a perfect world. the addon would be the same voltage as the lead. But its slightly higher. So as you drive the first 1/3rd of your miles come ONLY from the addon. It takes all the load. So lets say you have 60mile range.

After 20 miles, the lead is still 100% full. The addon is half discharged.
After 40 miles, the lithium is about 80% used, and the lead about 20...
Keep going and you run the lithium too low, and the lead still has some remaining but you must stop.

Add a high power low resistance low voltage drop forward diode, with around a .25V approx drop. Now the lithium is used less, the lead more, by around 15 to 20%. SAdd 2 and you will use all the lead, and may have some lithium left. Ideally you need somewhere between the two. Expresso is experimenting to see what works best. 1 or 2 of those diodes.

Thank you that's a great explanation, I understand now.

[Burgerman]

fORGOT TO ADD:

Diodes come in many types.

Normal diodes (Power diodes) allow electricity to pass in one direction only. But always drop the voltage a little.
Sillicon diodes drop around .7 of a volt. Too much.
Schottky diodes are generally around .25V drop. So not bad for our purposes here. Depending on other specs, the greater the current the higher the drop. So it increases under load. So it also matches the lead better.

We really want about .35 to .4 drop for a perfect match.

[Scooterman]

This is probably a really dumb question but it's on my mind so I might as well ask it...

Why a diode and not a resistor, if it's just a case of dropping a bit of voltage so the lifepo4 voltage matches the lead?

[BugBayMx]

I'm with you I want to learn, it is also new for me this lithium explain to us easy and detailed

i will post more pictures as i go along but to be honest it wont be much difference than my previous 60ah built - same thing only larger Cells this time - thinner but taller - and 80ah !!!
-

I'm really interested in this build Expresso, so if you can detail each step I for one would really appreciate it .

As well as the physical build can you detail the non-physical initial charging, voltage graphs, etc, for people like me who've never done lithium before but plan to, and using prismatic cells. (for me not an add-on but a lead replacement on my road mob scooter)

[expresso]

That copper connector can handle a thousand amp . Don't worry .

Add teeth lock washer as cushion . Apply Loctite and don't over-tighten it.

for some reason the pictures of the connectors seem thicker than they really are - i can bend them easily - but ok if you say it works - it would make it easier for me to use instead of making new cables - i may need more than just one lock washer to fill the gap - maybe a flat washer and lock washer - with locktite also - i have to test it later to see what i can use to fill that gap -

do you think its good idea to double up on the connectors ? instead of one use two ? i have enough of them to use two -

what size washer do you think i would need - M8 ?

[Burgerman]

because a resistor drops zero volts at all at no current. A little bit at light current. And so much at high current you dont move. In other words its got too much resistance to drive anything. Or its got so little it drops nothing. We need a constant small voltage drop, almost regardless of load. Which the right diode provides.

[Burgerman]

If you can use 2 then it will work instead of washers...

[expresso]

i will post more pictures as i go along but to be honest it wont be much difference than my previous 60ah built - same thing only larger Cells this time - thinner but taller - and 80ah !!!
-

I'm really interested in this build Expresso, so if you can detail each step I for one would really appreciate it .

As well as the physical build can you detail the non-physical initial charging, voltage graphs, etc, for people like me who've never done lithium before but plan to, and using prismatic cells. (for me not an add-on but a lead replacement on my road mob scooter)

Hi - dont have a micrometer etc, - i will try to be detail as i can - i may start on Sunday - its very similar to the 60ah ADD ON section - only this time i may use the connectors i received and see how that works out - will add a fuse also to the pack - which i will add to my other ADD ON packs i have this winter.

[Scooterman]

because a resistor drops zero volts at all at no current. A little bit at light current. And so much at high current you dont move. In other words its got too much resistance to drive anything. Or its got so little it drops nothing. We need a constant small voltage drop, almost regardless of load. Which the right diode provides.

Thank you I totally get it. I'm glad I asked.

[expresso]

Still think 2 diodes MAY be a bit much. But if so, easy to remove 1 with tools! Do those bus bars allow room for cell insulation?

i havnt finished this cable yet - i can still use just one before i finish it this afternoon - if you think 1 is enough - maybe i leave 1 instead - i rather not have to touch it once its done. how would i know if 2 would be too much once its in use ? this isnt going on my Chair so i cant really keep an eye on it myself -

i know for sure 1 works - since i have it on my chair and i extending some range by about 5 miles extra - not bad at all - will vary between chairs etc, but its still something -

what do you think i should do - 1 or 2 ?

[Burgerman]

Its a case of being there and testing!

[expresso]

If you can use 2 then it will work instead of washers...

i think i may have to use 2 connectors and a washer - i will check later how much i need to add to fill the gap - the cells which would get a cable on them ring connector etc, should be fine - maybe need a washer there also if still not enough - but those shouldnt be a big deal to fix - the other cells with no ring connectors cables are the ones which i have to fill the gap -

i check it later and take a picture

[expresso]

Its a case of being there and testing!

i wont be there when its in use etc, - how would i know - what can i check the charging graphs - ? and she may not even use it yet till she gets her 646 chair set up with it - now its just on the Rival chair she dosnt use and charges once a week -

[Burgerman]

After she stops, or gets home with say a couple of oranges, you will get about 40Ah back into the MKs, since thats all they really allow you to take out. And then see how low the lithium is. Try it with 1 and 2 mosfets. 2 is safe, she just may hit a red light, before using up all the lithium Your PL8 will tell you.

[expresso]

After she stops, or gets home with say a couple of oranges, you will get about 40Ah back into the MKs, since thats all they really allow you to take out. And then see how low the lithium is. Try it with 1 and 2 mosfets. 2 is safe, she just may hit a red light, before using up all the lithium Your PL8 will tell you.

Ok we made the cable today - will install when shes ready to use the chair etc, - and i will check it when she gets back - will check with both batteries combined and then disconnect to check each one - - then recharge at 3.6V and see what that does - will be a while before shes uses it and with the cold weather - who knows

its not the best looking cables , i hope it works at least