Making your own battery pack

[Wizard9956]

Hi all , if i was to buy 10 of these batterys and join them together ,
4x Ultrafire CR123A Rechargeable Li-ion Battery 16340 L on eBay, also Other Rechargeable Batteries, Rechargeable Batteries, Batteries Battery Chargers, Consumer Electronics (end time 01-Feb-08 22:09:51 GMT)
the voltage would be 37 volts , but would the joined together batterys be 8.8ah or would they still only be 880mAh ?

Thanks Wizard

 

[flecc]

They'd still only be 880 mAh.

Connecting in series increases the voltage and keeps the capacity the same.

Connecting in parallel increases the capacity and keeps the voltage the same.

These cells have been discussed before, and if used, the battery would be heavier, larger and more expensive than present Li-ions, and would also lose to NiMh in size and cost.

The only advantage they have is longer life, and even that hasn't been adequately tested in an application like ours.
.

 

[Honk]

I have made my own batttery pack from 120 pcs of NiMH AA cells at 2.2Ah each.
Titanium AA 2200 mAh NiMH Rechargeable Battery (TPEH-TAA2200)

The pack capacity is 36V 8.8Ah at max 12 amp continuesly discharge.
The weight is 3.5kg including the homemade batt box and very special BMS.

I chose the AA cells as they have a good power to weight ratio and
they are also sold very cheap compared to other batteries.
The batteries cost $174 and shipping was $22 in two Flat Rate envelopes.
I asked Batteryjunction to mark the envelopes as samples at low value.
By this I managed to escape the othervise expensive customs duties.

 

[flecc]

Similar to the one I made Honk, though I used 128 cells to deliberately over-volt slightly, and my cells though cheap cost more than yours. Not really gutsy enough for the powerful eZee motors though.

Website page here.
.

 

[Honk]

Very nice review. I enjoyed reading it.

My own AA pack is divided into three 12V sections of paralleled cells.
Each section is made from 4 blocks of 10 cells in series.
When charging the AA pack each block in each section (a total of 12 blocks)
is being charged independently by a special charger I have designed.
This ensures each block of 10 cells in series being charged totaly separately
from each other. When charging is ready I simply reconnect all blocks into
a 36V pack inserting by a plain pin list into a header that handles the wires.
The charge and drain of all the 12V blocks is handled through this pin list.
It's very easy to handle the pack, safe charging and easy bike mount.
None of the AA cells of each blocks is soldered together. Instead I designed
a special battery holding technique by etched PCB:s, rubber strips and copper
teminations. This ensures great contact between all cells in each block.
The best part is that it just takes 10 minutes to swap cells in the whole
pack when the cells are old and is ready to be replaced by new fresh ones.

I intend to use a lower wattage Tongxin motor at 360W peak power.
Commutating to work is 8.5 miles in each direction.
I will peddle besides running the motor and I have calculated the pack
being more than adequate to assist me to work one way.
At work I will charge the pack before going back home.

 

[flecc]

That's very much better as a permanent pack Honk, and ideal for that Tongxin application. I especially like the easy cells changing capability.

As you've gathered, mine was purely experimental on a what/if basis and so not convenient for permanent use. Used a lot of solder too.
.

 

[delmumbles]

What about 24v

Can you give a configuration for a suitable replacement battery pack for A CURRIE PRODRIVE KIT and Heinzmann 200w kit. using the aforementioned cells.

 

[Tiberius]

Delmumbles,

You mean AA cells? For 24 V you will need 20 in series. That will give you 2.0 to 2.7 Ahr, depending on the cells you use. Suppose you use 2.2 Ahr cells and have 4 sets in parallel - 80 cells total - that will be 8.8 Ahr at 24 V.

You can get AA cells already welded up into a pack of 10 (12V). I used 6 such packs to make a 4.4 Ahr, 36 V pack.

If its a permanent pack and you are careful with charging, ie, have thermistors in the pack, the series/parallel arrangement isn't so important. Ie, 20 series/4 parallel or 2 x 10 series/4 parallel all work out as 8.8 Ahr, 24 V.

HTH,

Nick

 

[Syman]

Can you give a configuration for a suitable replacement battery pack for A CURRIE PRODRIVE KIT and Heinzmann 200w kit. using the aforementioned cells.

What do people think of this battery ThunderPower TP6000-5S3PL. I want to link two batteries together to create a 37V pack. I am going to be running a Heinzmann motor of 200w and takes 33A.
Do people think this battery would work?

 

[Footie]

My own AA pack is divided into three 12V sections of paralleled cells.
Each section is made from 4 blocks of 10 cells in series.
When charging the AA pack each block in each section (a total of 12 blocks)
is being charged independently by a special charger I have designed.
This ensures each block of 10 cells in series being charged totaly separately
from each other. When charging is ready I simply reconnect all blocks into
a 36V pack inserting by a plain pin list into a header that handles the wires.
The charge and drain of all the 12V blocks is handled through this pin list.
It's very easy to handle the pack, safe charging and easy bike mount.
None of the AA cells of each blocks is soldered together. Instead I designed
a special battery holding technique by etched PCB:s, rubber strips and copper
teminations. This ensures great contact between all cells in each block.
The best part is that it just takes 10 minutes to swap cells in the whole
pack when the cells are old and is ready to be replaced by new fresh ones.

Hey Honk,
I was wondering how your homemade pack is going?
I've just got a kit, so I'm going to have a go at building a battery pack from 2400 AA cells, following your example.
4 blocks of 10 cells in series giving me three 12V sections of paralleled cells, I should hopefully end up with a 36v 9.6amp battery pack.
I'm planning to mimic the design of my existing ebikes battery, so I can use it as additional battery pack with both bikes. I hope to get a range of 30 to 35 miles in hilly Cornwall - Ideal for those long leisure cycle rides
.

 

[Footie]

Got a quick question for the technicals on the forum.
Being none electrical, building my own BMS would be impossible.
From flecc's experiments it seems during use there no need for fancy additions to the wiring.
However, when it comes to charging some form of BMS would be needed.
I have looked at this and I think I have found a way around the need for a BMS but would like opinions.

I don't know much about batteries, so I'm likely to make myself look like an ass here but;

If I assemble the AA cells in my DIY battery in blocks of ten - Using battery boxes from Maplin AA Size Battery Holders > Maplin

- Could I use a 500/1,000mA Smart charger (type used of RC race packs) Radio Control to charge the blocks separately, doing away with the need for a BMS?
.

 

[john]

Got a quick question for the technicals on the forum.
Being none electrical, building my own BMS would be impossible.
From flecc's experiments it seems during use there no need for fancy additions to the wiring.
However, when it comes to charging some form of BMS would be needed.
I have looked at this and I think I have found a way around the need for a BMS but would like opinions.

I don't know much about batteries, so I'm likely to make myself look like an ass here but;

If I assemble the AA cells in my DIY battery in blocks of ten - Using battery boxes from Maplin AA Size Battery Holders > Maplin

- Could I use a 500/1,000mA Smart charger (type used of RC race packs) Radio Control to charge the blocks separately, doing away with the need for a BMS?
.

Footie, you don't need a BMS for for NiMH batteries. What you normally do have though is a thermistor in the pack to detect the rise in temperature when they are fully charged. The charger you are looking at detects voltage instead of this, which should work, but not as reliable as temperature.

The other issue is that I am not sure that the connections on those Maplin battery boxes would be up to the current you are going to draw from the batteries.

 

[Footie]

john Posted:
Footie, you don't need a BMS for for NiMH batteries. What you normally do have though is a thermistor in the pack to detect the rise in temperature when they are fully charged. The charger you are looking at detects voltage instead of this, which should work, but not as reliable as temperature.

The other issue is that I am not sure that the connections on those Maplin battery boxes would be up to the current you are going to draw from the batteries.

Thanks for you opinion john.

My basic understanding was that the RC charger is designed to charge 10 cells (1.2v each) max 12v and that's what I will have (in the blocks). So my interpolation seems correct from what you say.

Not sure what you mean by a "thermistor" or how it would work I'm guessing it shuts the power off? Like I said my knowledge of electrics is very limited.

I hadn't thought about "everything going into meltdown"

You may be right - the wires do seem a bit thin. In truth, I'm trying to avoid soldering the cells together. I have to be able to separate the blocks for charging. I could solder them into 10's but it makes handling them difficult with the potential for wires coming loose, etc. I also wanted to be able to check the cells individually should a block develop a fault. If they are all soldered it makes it difficult. I may try a reduced size battery to see if the block wires fail. At least if things go "crispy" I will have only fried a few cells rather than the whole pack
.

 

[john]

I may try a reduced size battery to see if the block wires fail. At least if things go "crispy" I will have only fried a few cells rather than the whole pack
.

Yes you could try the connections with just a few cells first or you could ask Maplin what current the boxes are rated for.

 

[Footie]

I called Maplin Technical Support about the battery boxes.
Not sure what the max amps will be.
Bearing in mind, Honk said he was pulling 12 amps from his 36V 8.8Ah AA battery and my own ebike has a max of 20 amps.
I asked if the boxes would be ok for 15 to 20 amps - I was told the boxes where designed for the high drain 2700 AA's so they should be fine and would probably go higher.
So looks like they should be ok.

Edit Update:
I have tested the 500/1,000mA Smart charger and it charges a block of 10 cells (Maplin battery box) no problem.

Edit Update 2:
Finally finished charging all the cells (took a week). Used a Tronic charger (has intelligent charge control with individual port/cell monitoring). The 10 cell blocks are all reading 14 volts fully charged and 3 blocks together are reading 41 volts. All I have to do now is build a case for them.

Edit Update 3:
First test proved a disaster. Everything appeared to work fine. All the handle bar lights lit up. However, when the throttle was turned all the lights went out and the empty light came on. After examining the pack I found one of the wires to a 12v block was broken. Its possible that I may have only had 24v, which is why the empty light came on. The cap wires are too fragile and need rethinking. So I have dismantled the pack (for now) and will figure out another way to connect it all together again.
.

 

[prState]

I have made my own batttery pack from 120 pcs of NiMH AA cells at 2.2Ah each.
Titanium AA 2200 mAh NiMH Rechargeable Battery (TPEH-TAA2200)

The pack capacity is 36V 8.8Ah at max 12 amp continuesly discharge.
The weight is 3.5kg including the homemade batt box and very special BMS.

I notice at that link a year later, they sell 2600 mAh AA Titanium batteries for same price as the 2200 now.

 

[john]

Edit Update 3:
First test proved a disaster. Everything appeared to work fine. All the handle bar lights lit up. However, when the throttle was turned all the lights went out and the empty light came on. After examining the pack I found one of the wires to a 12v block was broken. Its possible that I may have only had 24v, which is why the empty light came on. The cap wires are too fragile and need rethinking. So I have dismantled the pack (for now) and will figure out another way to connect it all together again.
.

Have a look at a 13Amp mains cable (kettle, toaster etc). This is the sort of thickness of copper you need in cables from and between batteries.

Also, make sure you put a fuse in your pack somewhere before testing!

 

[tony18m2001]

Ezee Cadence battery pack with Aldi 'C' cells

I've just started on the journey towards rebuilding my old kn*****d Li-ion battery by buying 31 packs (2 cells spare) of Aldi Activ Energy C cells (4Ah) - recently reduced in price to £1.99 for a pair - that's £61.69 for the set - cheapest on the planet AFAIK. I've numbered them 1 - 62 and am setting about charging them and doing a discharge test on 8 at a time at 1.2A each to weed out the any weak cells. I'll keep you posted of the stats on this. When the battery is complete, I intend to monitor it on my Ezee Cadence with my newly acquired CycleAnalyst power monitor. Watch this space - and Flecc might have to come to you for answers on best mechanical/electrical arrangement in the battery box.
Tony

 

[Fecn]

I did some tests on my Aldi C-Cell pack over the last couple of weeks. My pack is 66x 4Ah C-cells arranged as a 22S3P pack (26.4V, 12Ah). The last 50-watt discharge run I tried, I managed to get 11849mAh out of the pack (just 151mAh short of the theoretical maximum).

I am well chuffed! The pack seems to have no problem whatsoever delivering the relatively high current that the bike uses (up to 15A, ~435W at times), and when running in parallel (through a schottky bridge) with the bike's normal battery my effective range increases from ~25 miles to more like 75-80 miles.

I really can't fault my Aldi pack - The only downside I can find is the extra 5KG of weight. (The Aldi NiMH cells weigh in at 71.7 grammes each.)

More details of the pack I put together are on this post... http://www.pedelecs.co.uk/forum/44206-post10.html


Having used the packs in parallel (schottky bridge) and felt the difference in performance that results from having a 'stiffer' supply which doesn't dip under high loads, I am now of the opinion that the Li-Poly pack isn't really up to the job of handling 15A loads anyway.

Sorely tempted to buy a bunch more Aldi cells and make a super-large pack (48Ah) for when we go camping.

 

[tony18m2001]

Rebuilding an Ezee Cadence battery pack with Aldi 'C' cells continued

I posted this in April and need some advice. I did discharge tests on the 64 Aldi C cells and was happy with their 4Ah capacity (although I did manage to overcharge a couple which exploded the plastic insulator end of their cases - still seem to work OK, but presumably now of lower capacity so I wont be using them). I have finally got round to opening up my Li-ion battery case and have a problem - I cant work out how to fit 64 (or 60) cells in it. I always end up with a few that I cant sandwich between the 2 layers and still close the case. I am loathe to throw away the C cells and start again with AA cells as Flecc did So I am wondering what would happen if I substituted some 2500mAh AA cells in the assembly. I have just ordered 32 AA NimH from Hong Kong (eBay) at around £0.50 each. There are various ways I could do it and I would appreciate advice on the following options - originally I was going to connect 2 C cells in parallel and then 30 or 32 duos in series to make 36 or 38.4V, 8Ah:
1. I could make a 6.5 Ah battery by connecting 1 AA in parallel with 1 C, then these duals in series - is there a problem with self discharge between just 2 cells of different capacity?
2. I could probably stretch this idea to C + 2 X AA - would fit I believe.
3. I could substitute triplets of AA cells in parallel (=7.5 Ah) for some of the paired C cells - would this overstress the AA's? - I might be able to squeeze some sets of 4 AA's in parallel which would then presumably be safe from overdischarge
4. I could make a whole bank of AA's in series and parallel it up (via Schottky diodes?) with a bank of C cells.

ps I can post some pics of the Phylion Li-ion cells if anyone is interested - the cases were quite swollen after a year or so of disuse.
pps Flecc - your NimH 'loan' battery is now cutting out regularly after over 2000 miles or so at around 4Ah of discharge - the internal impedance has gone too high, I guess - my Cycle Analyst shows a minimum voltage as low as 25V. I might try and see if the problem is with just a few of the cells, once I've got a working substitute battery.