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[jerrysimon]

Hi all. I have been commuting to work on my eBrompton for three years now doing some 4000 miles. It transformed my working day

For all that time I have been using the round A123, 26650 2.3Ah cells. I make up simple DIY packs (though its cheaper to buy them ready made up now) 6s1p * 2 connected in series to give me a 12s1p, 36v, 2.3Ah pack. The 6s1p packs are easier to balance using one of my RC chargers, not that I need to do it that often as they self balance pretty well. My 10.5 mile round commute is pretty flat. Initially I use to just charge at home and run it flat but I lost a cell after a year from that abuse. Anyway I replaced a cell and its been fine having now done over 800 charge cycles. Considering the pack only cost me £70 to make, I have more than got my moneys worth. Anyway just lost another cell which I will replace.

If I go out for longer journeys I tend to take two of these A123 packs with me. My setup is very light assist (lTongxin based) and I tend to pedal all the time. It probably draws an average of no more than 5-6amps and propels me along easily up to about 17mph without me helping that much.

Anyway I have been thinking about getting another higher capacity pack for longer rides. I will continue to use my A123s for work. Being only 1kg they are great for the Brompton for carrying etc.

The easiest solution would be to buy a ready made 36v 10Ah pack. Probably a LiFePO4, but I like the idea of being able to service it myself. I have thus been thinking of either a Headway 12s1p pack of 10Ah cells again split into two 6s1p packs which I would maintain the balance of manually, though I appreciate that these will not hold their balance as well as A123s.

Another alternative for a slightly larger pack than I currently have, is a 6Ah one using a 20 cell 10s2p pack (split into 5s2p packs) of the Konion cells. Saw these on ebay which seem good value if they are genuine Konion cells ?

http://www.ebay.co.uk/itm/320951949469?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I am not really interested in using a BMS, please don't flame me lol

Any comments/advice welcome. I am not really a lipo fan and though I know they can be safe as I charge at work sometimes I prefer to leave my battery unattended without any worry. I guess maybe not so important in that I will not be using this new battery for my daily commute.

Regards

Jerry

 

[jerrysimon]

PS that seller does a few of these sized cells including these

http://www.ebay.co.uk/itm/2-HID-Battery-10A-18650-INR18650-13P-1300mah-3-7V-Li-ion-Rechargeable-Battery-/320924045533?pt=US_Rechargeable_Batteries&hash=item4ab89050dd

Are the Konions still the best in this application with no BMS ?

mm maybe I should have stuck this in the battery forum. Happy for it to be moved.


Regards

Jerry

 

[docnjoj]

Well the original Konions were made by Sony and found in Bosch and Makita tool packs. They are excellent cells and generally do self balance. Those celll specs look similar but you would have to test to see if they can actually support a 10 amp draw, 5 bucks apiece with welding the pack is not a terrible deal. Fatpacks are going for $150-200 these days. That is for 20 cells in the case for 36 volts from various sellers.
otherDoc

 

[jerrysimon]

Yes the first link specifies them as SONY US18650VT V11

So if you were to get them made up into a 20s pack would it be best to get them made as 5s4p then connect them in series ?

This probably seems the best for manual balancing. As I said maybe I should move this to the battery forum.

Regards

Jerry

 

[docnjoj]

Hmmmmm......... that is about 90 USD delivered for 10 cells. And no guarantee that they are the real thing. Definitely testing is in order.
otherDoc

 

[arkmundi]

Hi all. ... I am not really interested in using a BMS, please don't flame me lol
Any comments/advice welcome. I am not really a lipo fan and though I know they can be safe as I charge at work sometimes I prefer to leave my battery unattended without any worry. I guess maybe not so important in that I will not be using this new battery for my daily commute. Jerry

See my saga thread: A123 AMP20 cells from Victpower, Agniusm's kit, build <1 day, no BMS, keep tabs with Watt's Up and/or Celllogs. Simple, clean and delivers!

 

[jerrysimon]

Thanks. I think I may try ordering two of those 5s2 packs to see what they are like. Still cheaper than my 12s1p A123s and a little more capacity. I have paid more for used Makita packs which had few useful cells in and I ended up using for my lights.

I am interested in the Headways (at first glance they look so simple) but it's a huge leap in capacity, weight and cost wise and would probably need a lot more care without a BMS.

Oh just saw Arks reply need to read that thread

PS Oh my that's a large battery. At the most I would only want 10Ah

That's the thing with Headways in pictures they look quite small, but I have realised in real life the are huge lol

Just to get an idea of the light assist highly portable bikes I like and use

This is a Titanium two speed Brompton with a light weight 1.5kg Tongxin motor. Total bike weight to carry is 11.5kg with the electronics i.e. controller and a 1kg 12s1p A123 battery pack in the bag. As I say I use this on my daily 10.5 mile commute charging at work each day.

Regards

Jerry

 

[dnmun]

i just cannot imagine how you can balance a pack without a BMS. i know you guys assume it happens naturally but i hate to see people losing cells and capacity when they overcharge or over discharge these lifepo4 cells.

i guess if you have a balancing charger it is possible, and you could use the balancing charger on multiple packs so it would be more practical in terms of cost, but i just cannot imagine how i could balance these packs i have without a BMS.

i have to use big power resistors to get the high ones back in line, so time consuming.

 

[jerrysimon]

Exactly dnmun which is why I am being very cautious about the next battery pack I want. The A123s to which I refer are pretty bomb proof though not indestructible if you abuse them.

The Konions look good if I maybe just want to go up to 6Ah packs. The Headways look like more of a risk.

Given my lower current draw requirements, maybe I should just buy myself a good value generic 8-9Ah bottle battery and be done with it lol

Regards

Jerry

 

[docnjoj]

We run a group of 6 Fatpacks parallel and use the single Bosch charger. We never go below 50% since they are also // with a Ping, but of course charged separately. These packs were purchased when Fatpacks were $45 delivered each and have been in regular use for about 3 years. I haven't done capacity tests recently but they all chare up and hold a charge for weeks. No balancing on the Fatpacks. I'm convinced that those cells (Sony V an VT) do self balance and do it well.
otherDoc

 

[Punx0r]

It's a bit potluck, but there's a 36V10Ah battery on ebay at the moment. I assume it has a BMS.

It only caught my eye because it started at 99p

http://www.ebay.co.uk/itm/110949120413?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[jerrysimon]

Yes Punx0r I saw that. They are sold off from the Electric Transport Shop usually ones they get in to test I think. Its shrink wrapped so not much advantage over my DIY ones.

http://feedback.ebay.co.uk/ws/eBayISAPI.dll?ViewFeedback2&userid=guddies7&&_trksid=p4340.l2560&rt=nc&iid=110949120413&sspagename=VIP:feedback&ftab=FeedbackAsSeller

I was thinking of something like this

http://www.ebay.co.uk/itm/36v-9ah-water-bottle-type-lithium-Li-ion-electric-bike-battery-/140828417278?pt=UK_Bikes_GL&hash=item20ca071cfe

Quoted as 2.8kg. Pretty much plug and play in my application. Cheaper from overseas but then import duty becomes a lottery. One of the ebike sellers on the pedelec forum sells a LifePO4 rear rack 36v 10Ah battery for just over £200 so probably better (has a two year warranty), last longer although heavier.

Regards

Jerry

 

[Punx0r]

The general advice is that packs from ebay are generally not a good idea. Apart from a couple of known-reliable sellers, many seem to be of very dodgy quality, and not even *that* cheap.

I only mentioned the blue one because it's worth a chance on it being ok or not if it sells cheap.

Perhaps you had the right idea all along making your own packs from known-good cells

Or consider RC lipo...

 

[jerrysimon]

Or consider RC lipo...

lol thanks

Jerry

 

[jerrysimon]

Hm looking at that ebay seller again looks like they are US18650VT cells which as I read are not the same as US18650V cells having less capacity

Regards

Jerry

 

[dogman dan]

Anything less than 20-30c lipo after A123's will really be a letdown. I'd say keep doing what you do, just add more capacity a123's.

2c lifepo4 will only dissapoint you.

 

[jerrysimon]

Thanks Dogman but notice my setup is only very light assist mostly drawing no more than 5-6 amps. My lightest motor only provides 180-200W of assist.

Regards

Jerry

 

[Punx0r]

Another DIY thought: a few weeks ago there was a UK member on here who had gotten a load of used Dewalt 36V tool packs with A123 cells and was selling them for £20 each. It'd be a case of testing and weeding out a few duds, but it could be a cheap option for high quality, safe cells?

 

[jerrysimon]

Yes I already use 26650 A123 cells and build 12s1p packs.

As you say great safe cells

I guess I could build a bigger pack and use a BMS cough cough

Regards

Jerry

 

[arkmundi]

i just cannot imagine how you can balance a pack without a BMS....

There's been a lot of discussion about this. Yes, keep the cells reasonably balanced. But there is the digital component approach and the manual approach. I've take the latter to avoid the BMS-mess (and yes, its a real mess). The balance only need be done ocassionaly - I'm doing it once a month. This is a KISS you approach ("keep it simple stupid"). Adding in uncessary complexity is stupid. BMSes are for larger electric vehicles with regenerative braking, lot's of start/stop, charge/discharge. LEV's with the AMP20 cells DO NOT NEED A BMS.

FYI, just bought a second set of cells from Victpower for $16.50 a piece, half-tab of course.