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

[snaker]

So as I understand, this add-on solution only works if using lead acid batteries in the battery box, doesnt it? Can we make the add-on work with a full lifepo4 pack (in the battery box)? I mean a switcher automatically switches the power source between the add-on and the pack. E.g the add-on works first till it is nearly drained. The switcher (or something else) monitors the add-on's voltage. If it's too low (i.e 24.0V), it automatically disconnects the add-on and switches the power source to the pack in the battery box. Or better if the pack works first then the add-on. Is that possible?

[Burgerman]

The 2nd one is. Main pack first. Just dont plug in the addon. But that would just then recharge the main pack when you did... And many amps flow. And why would you want to do that? You could add switches. Again you would be driving on only a small 30Ah addon. Which will decrease cell life. You WANT to use both.

[snaker]

Yes, I just think if possible use both (main pack + add-on). That's because the current battery box is too small, maybe it only contains ~75Ah in maximum. And I lost my hand control, so I need automatically switching. If I can use both, this add-on solution seem easier and saving money. If not I have to think about modifying and enlarging the battery box first. In this case I will only use the main pack.

[Burgerman]

You only need plug it in and forget. It makes one big battery.

[snaker]

You only need plug it in and forget. It makes one big battery.

Is it that simple? You make me more vague

Supposing that:
- I have 75Ah main pack in the battery box, 50Ah addon on the back. They are parallely connected.
- Each hour of driving consumes 10Ah.

1. Does it make a 75 + 50 = 125Ah pack?
2. What will happen if I have driven in 5 hours? 6 hours? I mean how many Ah remain in the add-on after I have driven 5hrs, 6hrs?

[Burgerman]

No idea. But both main pack, and add-on will be at the same PERCENTAGE.

The fullest one charges the emptiest one all day long until voltages are equal.

[LROBBINS]

The only thing your probably have to remember to do is have the main pack fully charged before you connect the add on the first time. Then just leave them connected together and treat them as one big battery - there is no need for any kind of switch.

[shirley_hkg]

I would recommend BOTH batteries be fully charged , when connecting them .

Once connected , leave them CONNECTED all the time .

[rustyjames]

What would be the consequences of connecting up to weak lead blocks?

[Burgerman]

Your lithium will charge them, with high amps initially.

[Gnomatic]

You only need plug it in and forget. It makes one big battery.

Is it that simple?

Yes, it is!

The ADD ON and lead bricks are connected and charged together. Look at this pic of expresso's setup.



The charger(CellPro PL8) is connected to the chair by a single cable. The ADD ON is is connected to the lead bricks in the chair. The PL8 is charging both the ADD ON and lead bricks simultaneously! Not only is it charging both, its charging them at a higher current than what your standard mobility charger, which means faster charging. On top of this, the Gel lead bricks are being charged at their proper charge voltage, helping ensure maximum service life. Standard mobility chargers cook Gel batteries with too high of a charge voltage, greatly reducing their usable lifespan.

So your $500 set of MK gels are going to last MUCH longer with the ADD ON, as the depth of discharges will be shallower, and because they will be getting charged at a voltage that maximizes their service life. The benefits of using an ADD ON this way are many.

[expresso]

What would be the consequences of connecting up to weak lead blocks?

Nothing really it will work still but you wont get the Best results and the ADD ON will work harder i believe - you wont get the best range you can get - if you want to use your lead first and kill them down till you replace them - then replace your Lead with new MK gel 24 - and Connect the ADD ON together - never even using the Lead Alone - charge both first fully and then connect as One - thats the best start you can have to getting the best results out of it

you dont need switching anything - just leave it alone connected all the time - if you have a PL 8 charger - you use it - forget about any BMS with this - just get a PL 8 if you dont have one - and use that - its works best and easy enough - once all done - one cable connected from the ADD ON to the PL 8 to charge - thats it -

BM can make a preset i am sure - i can give you the one i use which BM did for me

[Burgerman]

He already has a small bms lithium. No lead. But you can still do this, as the PL8 will charge both as one big battery. It will balance the addon properly, and the bms will balance the on board battery in a fashion.

[LROBBINS]

If there is a large difference in the state of charge of the two batteries, and Shirley is quite right it could be either one, there will be a large current flow from the full one to the empty one, possibly at a higher current than your connectors or wires should be subjected to and possibly a nice healthy flash as you connect them. If they're both full the first time you charge, and you always leave them connected, you don't have to do anything except connect the charger and start it.

[Burgerman]

He means me I think! Once connected, then both your lithium batteries will always be at the exact same state of charge. In use, during charge, always. No switch, no swapping, no anything. Just connect them together. This is then one big battery.

[rustyjames]

What's the consensus on where to buy the cells, for those in the US?

[Gnomatic]

Several of us have bought cells from EV Assemble. They've been fine to deal with.

ex-Gooserider recently looked at several sources, and I believe he went with a company that was recommended by Headway Headquarters, the US distributor of Headway cells in the US.(HH no longer sells retail) The company is Boka Energy Technology Co. Ltd, Michelle Lu. Their contact email is bote_2014@163.com.

Boka was a bit cheaper than EVASS.

[Burgerman]

Also good service from evassem. But UK. 6 to 8 days 3 occasions. But get adequate square connectors, etc as getting the ones you were short costs a lot of shipping!

[rustyjames]

Thank you both for the input.

[expresso]

OK - I Tackled making another Charge Cable - this would be on the ADD ON end and it would stay connected to the ADD ON in the chair all the time - I managed to destroy Two Sub D connectors when i first started - this is my Forth Cable since i destroyed the first Two and so far all have worked out fine - May not be perfect - its always a 5 hour job for me and even after all the planning and prepping - i still made a mistake or two - turns out i made all my wiring with Female ends -
i was suppose to make this charge Cable with Male ends but didnt - not a big deal - i will replace the other cables to Male to connect this Charge Cable - just shows how much time and planning needs to be done - i did make it a bit on the short side - didnt want to take up too much room inside the Bag it will stay - I will making Another Charge Cable later on for the PL 8 - this time - at least 3 feet -

here are the steps i took -

First i prepared the Wires - i Strip a bit longer wire then i really need to Tin them - then i measure the wire with the Sub D - and Cut to size - - then i fill the Sub D with solder - I start with the Single large pin for Neg. 12 Awg wire is used -
and work my way across the top row of small pins - which would be 0 1 2 3 4 and then Large Pin for Pos 12 Awg - the very end Large pin would be empty -

then i flip it and fill in the small pins again - start right under 0 and that would be 5 6 7 8 and the last small pin would be empty also - so you should have two empty pins - One large and one small pin bottom row

prepare the heat shrink, sleeve to cover it all - before you solder all the wires on the Sub D -

If using these XT90 Connectors - - when soldering them - also keep a pair connected - Male and Female - - Solder the one you need - and let them cool after your done - before taking them apart - to keep there shape during the solder - or you may solder one end and then find out its a tight fit when connecting - it could be from the heat may have distorted it just a bit and dosnt have a good fit - - if you keep both ends connected during the soldering - this shouldnt happen

Also - always test fit them before you do anything - see how they fit - if you can remove them etc, - i have had some that were too tight - and returned them -

Tinned Wires

[expresso]

Wires Cut to size

[expresso]

XT 90

[expresso]

XT 90 Done

[expresso]

Sub D Connector

[expresso]

Sub D - more

[expresso]

Sub D Charge Cable Almost Done

[expresso]

Finally Done - hope to improve as i make more all the time - i always stress out when i have to make this Cable - and this was my last Female Sub D i had -

[expresso]

Last of it - -

I have to make new balance wires with Male end and one XT 90 replaced with a Male for this Charge Cable to work - then i can connect them and test the pack - i got the bag ready to hang it in - just need to go find a plastic container to sit it in -
i am sure i will need to cut it and make it work - but as long as it fits inside length wise and height -

[steves1977uk]

Pity you didn't live in the UK expresso, I'd buy a ready made charge cable from you Your cables are professional looking like BM's

Still trying to get mine built up so I can get someone to help me rebuild my pack.

Steve

[Burgerman]

If you knew how long it takes...


$$$$$$$$$$$

Seriously, planning, CORRECT materials, good iron, cleanliness, and a massive block or two of blue-tack is the secret. Expresso, buy 20x more! You can line up connectors, wires, etc and work with everything fixed in place.