Homemade Battery Packs

[DrkAngel]

I just capacity tested my 1 year old 25.9V 25.92Ah, homemade recycled Lipo pack.
(150+ cycles & and Winter usage)

1st step was to do a balance charge, to 29.4V (4.2V per cell), I used my new iMax B8.
Then I discharged to ~25.9V (3.7V per cell).

I rated 3.7V as optimal minimum usable voltage, based on the discharge test, graphed below.
Cell variance at max discharge was within ~2 100ths volt of 3.7V, excellent, IMO, for used cells.
(1 bank "patched" by adding 1 - 18650 cell)

(Different cell types have different discharge profiles!)

So test voltages were:
4.2V - full
3.7V - empty

The pack is a 7S12P, 3.7V 2160mah per cell.
With a 25.92Ah rating.
My iMax B8 balance re-charge, metered a 20.8Ah input.
Charging rate was 3A = .125-.15C, for maximum efficiency.
Giving a 80.2% , of rated, capacity!
Acceptable for old recycled cells! ... ?
(Maximum capacity input measured 24Ah, deeper discharge, (last year))

Please note!
This pack was built from the reject Lipo packs.
These recycled cells were pulled from the laptop packs that failed to recharge in the oem charger.
I still have 8kWh's of these packs that do charge properly - designated eMotorcycle "fodder".

Typically I do not charge this "fully" or discharge this deeply.
4.16V - full
3.75V - empty
are the voltages I use during "bulk" charging, and typical "lowest discharge voltage".
I, variously, use a modified Meanwell clone (1V-56V adjustable 7.3A) and a 29.4V (2A) Li-ion charger (trimmed with a blocking diode.)

I just capacity tested my 2 year old 25.9V 25.92Ah, homemade recycled Lipo pack.
(Hundreds+ cycles - Thousands of miles(~4000-5000+) & and Winter usage)
Only during this last year have I reduced peak charge voltage to 4.10V.
I try to never discharge below 3.7V per cell but delved there upon occasion.
25.9V to 28.7V (3.7V to 4.10V per cell) was 15.8Ah.
From an originally rated 25.92Ah pack this might sound horrible, but ...

1. Pack is partially "de-rated" due to reduced voltage test range.
2. This pack was built using only the defective packs ... the ones that would not charge properly
3. In the eZip pack it still outputs more than 2x the power that new, nearly twice as heavy, SLA batteries do.
(And 25.9V Li-ion is a tremendous improvement over 24V SLA!)

History
2011 - 24.0Ah (25.9 to 29.4V)
2012 - 20.8Ah (25.9 to 29.4V)
2013 - 15.8Ah (25.9 to 28.7V)

PS - Sometime last year 1 weaker bank was "patched" by wiring in 1 - 2600mah 18650 Li-ion cell.
Repair seems to have held up nicely.

Pack is nearing retirement, I got a goood supply! of donor packs for new builds.
15 packs per eZip rebuild.
Will restrict voltages to 4.05V peak charge and 3.75-3.80V discharge.
(This will reduce available Ah for 1st year but might increase it for 2nd year and extend usable life into 3rd, 4th maybe 5th year?)
With carefully matched, good condition cells might give me 3 - 5? years of reliable daily use.

Capacity map for these cells.

 

[emiyata]

I just capacity tested my 1 year old 25.9V 25.92Ah, homemade recycled Lipo pack.
(150+ cycles & and Winter usage)
Pack is nearing retirement

That battery pack don't owe you anything. I see that over the years you stuck to the same type of battery box. Is it mainly because it came with the bike or do you like the design and have not seen a better design?

 

[DrkAngel]

I just capacity tested my 1 year old 25.9V 25.92Ah, homemade recycled Lipo pack.
(150+ cycles & and Winter usage)
Pack is nearing retirement

That battery pack don't owe you anything. I see that over the years you stuck to the same type of battery box. Is it mainly because it came with the bike or do you like the design and have not seen a better design?

Got all the cells, plus spares for $40, $20 for the packs & $20 for shipping.

Love - Hate the battery box design.

Pros ...
Handy, to carry, lock, charge etc.
I love that I can take the oem design and do so much more with it than the manufacturer.
18650 cells pack in nicely.

Cons! ...
Limited size and shape of aftermarket batteries supported.
Seldom held properly in oem rack.
Rattles, sometimes dis-powers on bumps.
Contacts can over heat - melting contact too deep into battery box or melting contact sleeve - causing disfunction.

Fixes ... ?

Sloppy Rack fit:
Rack tightened by bending side rails.
Heavy bungee cord holding pack down.
Wedge!

Melting contacts:
Keep pack firmly contacted, "jittery" connection seems to produce the worst heat.
Instead of insulated wire, from contacts, inside pack, I intend on trying an oversized tinned copper braid as a heat dispersion device. Similar for the bike contacts.

Contacts on pack sometimes melt into plastic pack.
I "repair" using my 230w soldering gun, gently repositioning then remolding plastic.
I wedge contacts down using masonite (anything solid, fireproof, melt resistant etc.) board, protecting battery from contacts and insuring good contact extension.

Also tried an AC power cord connection, bypassing contacts.
Might quick switch between contacts and Deans Plug direct to alternate pack.
Unplug battery wire from contact module, plug int battery pack on top of rack, or alternate location (backpack?).

 

[emiyata]

Got all the cells, plus spares for $40, $20 for the packs & $20 for shipping.

Love - Hate the battery box design.

You have good and bad with most everything. Why I was asking was I will build a 48v 30ah pack(s) and the big dummy has a place to hold packs like that and would not take up space in the cargo bags in the back. The batteries would be fairly low mounted on the bike. They look like they can be moved to another bike. I guess the Andersons for power connections are working good for now and would like to build that into the pack.
The other design is using the tail of the bike and build a cover that opens up and you can remove the batteries. I don't like how high the batteries ride and that weight would add to cargo weight in the back.
I have a small battery pack 48v 10ah that works fine. I have a 60 tooth sprocket so I can pedal along at top speeds. The drain is very low. I have had the bike up to 30ish but 20mph or so is my normal speed.

 

[LeftieBiker]

How well do the AC power cord connectors work? I'm probably going to put my Ping 20AH pack in the right pannier (balancing it with other stuff in the left one) and I want a good reliable connector that isn't a PITA to put together. Less likely, I may try to build a battery box that can largely fit into the EZIP battery rack, but doesn't use the actual EZIP case or connectors...

 

[emiyata]

How well do the AC power cord connectors work? I'm probably going to put my Ping 20AH pack in the right pannier (balancing it with other stuff in the left one) and I want a good reliable connector that isn't a PITA to put together. Less likely, I may try to build a battery box that can largely fit into the EZIP battery rack, but doesn't use the actual EZIP case or connectors...

I would not go over 20 amps max. I could be wrong but I think the connector is rated 15 amps continuous. The connector I use is Anderson powerpole they are color coded and rated for different voltages and can go to very high currents. http://en.wikipedia.org/wiki/Anderson_Powerpole you can interlock them if you wish and make multi-conductor connector with them. I put something over them to prevent water from getting into them but many people that use them don't use anything over them and they say they have had good results. The one disadvantage is price. They don't give them away. Others have used other connectors and I am sure they will chime in.

 

[LeftieBiker]

How well do the AC power cord connectors work? I'm probably going to put my Ping 20AH pack in the right pannier (balancing it with other stuff in the left one) and I want a good reliable connector that isn't a PITA to put together. Less likely, I may try to build a battery box that can largely fit into the EZIP battery rack, but doesn't use the actual EZIP case or connectors...

I would not go over 20 amps max. I could be wrong but I think the connector is rated 15 amps continuous. The connector I use is Anderson powerpole they are color coded and rated for different voltages and can go to very high currents. http://en.wikipedia.org/wiki/Anderson_Powerpole you can interlock them if you wish and make multi-conductor connector with them. I put something over them to prevent water from getting into them but many people that use them don't use anything over them and they say they have had good results. The one disadvantage is price. They don't give them away. Others have used other connectors and I am sure they will chime in.

I can't find a problem with your reasoning, but it still seems "wrong" that a cord connection that can run a shop vac or a 1500 watt electric heater can't handle the power going to a 500 watt E-bike motor...

 

[emiyata]

I can't find a problem with your reasoning, but it still seems "wrong" that a cord connection that can run a shop vac or a 1500 watt electric heater can't handle the power going to a 500 watt E-bike motor...

Lets do the math .

120v AC
Watts/voltage = amps
1500 watts/ 120v = 12.5 Amps (yes it can handle that current)
but your motor runs on 48vdc not 120vac
850 input watts ( going up a hill)/48v = 17.7 amps (yes this is ok because your going up hill for a small percentage of the time.)
500 watts (on the flat)/48 v = 10.4 amps (yes it can handle this all the time.)
now 36vdc
500watts /36v =13.8 amps (ok but getting close)
now the hill
850watts/36v = 23.6 amps ( I think your connector is getting warm now)

Hope this helps

 

[LeftieBiker]

Then since I'm running a 24 volt pack, it should still be ok. I'll look into other options, though.

 

[DrkAngel]

When I decided to upgrade the battery for my eZip I wanted to try multiple ideas.
1st testbed was 36V SLA with a shitload of jumper wires, most notably the larger gauge directly to the pack contacts.

Next stage was 36V SLA in toolbox with HD AC power cord plug connection.

At the time I still connected through the contacts, tho I did use an adapter withe HD alligator clips.
Yes ... I bought a 6' cord and cut in in 2, rather than buying 2 plugs and wire.

Finally went LiCo!

At first I just strapped pack on top of rack.

Contact failure and subsequent removal, combined with the judicious use of pack inserts allowed side rack mounting!
A much better method.

High density foam offered a fair bit of cell protection.

AC plugs worked much better than oem contacts. They never got anywhere near as hot as the contacts!

Going the same route again, I would go with Deans Plug (T Plug). Typically rated at 60A continuous and 100A surge, should handle any foreseeable projects ... for a little bit anyhow ...


Oh! ... Insulated lunch bags (with handle) are available at K-mart for <$6.
A common item, should be available at any department store.


Oh! Oh! ... Yeah!
LiCo Rules!

 

[alsmith]

I like the racks, the way that the batteries are supported.
I've been looking for a way to support the weight of mine in panniers and have got part way to creating an aluminium cradle (tray kind of thing) to support the batteries then going to bolt through to a bar behind the rack down tubes.
Are they custom made racks, or a retail thing?

...............

High density foam offered a fair bit of cell protection.

...........

 

[DrkAngel]

OEM eZip - Izip.
Controller, switch etc. in center "box".

 

[alsmith]

I'll have a look at them but I bet they aren't cheap. What's the distance between the two vertical tubes that the battery fits between?

 

[emiyata]

Then since I'm running a 24 volt pack, it should still be ok. I'll look into other options, though.

You can do the math for your size of motor and see when you should do brisk pedaling.

Lets use the example 15 amp power cord 24v pack
Battery voltage of pack X current rating of the contacts = how many watts continuous
24 X 15 = 360 watts input

So many are saying what does this all mean? In general the lower you go in voltage the higher the current to deliver the same wattage. That means thicker wires and bigger contacts.
It should work with with very little heat on flat ground but it will generate heat going up hill.

So many are saying no big deal the wires are not melting I should be ok.
The problem is you loose range, your contacts may get very hot and melt what holds your contacts and gain nothing other than save some money.

This brings us to system efficiency.

Some members on the example above are saying that battery connector will handle 350 watt motor at full output all day long an a big laptop pack.

That is not true . The calculation is for input power but the motor is rated for output power.

power output (motor rating) + losses in the motor ,contacts,wires,ect = input power

Members are saying I know the wattage of my motor but how do I know the losses of the motor?

Well you don't but the people that makes motors do and have charts and graphs to help you. For our motor brushed lets say it's 70% efficient.

Now here is the updated formula and a 250 watt motor
power output + ( power output x losses (100-eff )/ 100) = input power

250 + (250 X(100-70/100)) =
250 + (250 x 30/100) =
250 + (250 x .30) =
250 + 75 = 325 input watts

This means the contacts can handle a 250 watt brush motor all day long without heating on flat ground at full output.

What does this say about my wires and connectors on a 500w motor? As long as you pedal some and brisk pedal up hills you should be fine for now but you should find better connectors in time. Your wires and contacts are sized for a 250-350 w motor.

I hope this helps

 

[DrkAngel]

On the other hand ...
The eZip, with 35A controller and 40A pack fuse seems to be wired with 14AWG wire, UL rated at 15A.

Obviously ... UL standards don't seem directly applicable to eBikes. (8AWG wire required by UL)
UL standards are rated for home and industry safety standards for continuous and prolonged use with a large safety margin.

Double the amps for reasonable periods might be acceptable?

Of course, lighter wire will waste more energy as waste heat, and
induce a voltage drop, especially with longer lengths and high amps..

 

[emiyata]

On the other hand ...
The eZip, with 35A controller and 40A pack fuse seems to be wired with 14AWG wire, UL rated at 15A.

Obviously ... UL standards don't seem directly applicable to eBikes. (8AWG wire required by UL)
UL standards are rated for home and industry safety standards for continuous and prolonged use with a large safety margin.

Double the amps for reasonable periods might be acceptable?

Of course, lighter wire will waste more energy as waste heat, and
induce a voltage drop, especially with longer lengths and high amps..

Now days contacts are cheap compared to the big hitters batteries. I calculate the contacts based on using the contacts at full rated load. I want this electric bike to be reliable and when you talk savings your better off targeting the big ticket items mainly the battery. We all now why we are reading this thread.
UL standards are not used on anything from what I can see. The supply to charge my battery don't have UL or TUV stickers on it. It is what it is a ebike kit made in China.
I did UL testing and we put cheese cloth over product and the guy from UL would tell you where to put a short and apply power and the cheese cloth can't catch on fire. This is the destructive testing . They also require you to show them your thermal data on the product to make sure you don't go out of range and verify spacing. It's more a safety thing that building large tolerances. I am starting to drift off topic now . It's time to get back to the construction of battery packs using laptop batteries.


Double the amps for reasonable periods might be acceptable?
Wow that is a hard one. My answer is it depends... wire if you don't go over the temp rating of the wire. If you have Teflon wire in most cases you would be hard pressed to over heat it. I would say the copper would open before the wire coating would melt. With a high temperature wire short duration it should hold up in most cases. If you run it for minutes it may become so hot you would not want touch it. The other thing is if you heat cycle copper over time it will become brittle and will fail as a wire or in contacts. I recommend using the correct size of wire and contacts. The costly part of wiring is the water proof connectors.

 

[DrkAngel]

An eZip with 29.6V 31.2Ah pack, (8s12p), without any regearing, will push to (legal - USA) 20mph capability!
With a substantial torque increase ...
A 24% torque increase, as opposed to the 20% (initial) torque decrease associated with 16T or similar with the 13T mod.
Problem is, finding a controller that is 29.6V capable.
Except for the pre-mid 2008 eZips, universal voltage controllers seem to be the only available.

Representative 24v to 29.6V comparison


Power (red lines), beyond the road load-wind resistance line (black), looks like ...
+50% - 10 mph
+100% - 12.5 mph
+200% - 15 mph

Hill climbing capability seems impressively increased!

 

[LeftieBiker]

Hey Drkangel: what is the brand/model of insulated cooler bag you are using as a battery bag - the one with what looks like a sunrise on the logo? That looks like a really good fit for the EZIP rack, and the ones I'm seeing around here are a bit too big. I need to get ready to instal the Ping pack when it arrives in three weeks...

I'm still undecided on what connector to use. I'll look for the heavy trailer type plug locally, but if I don't find that, I'm not sure. I don't like the fact that the Anderson connectors are so exposed to even gentle mist. They have a newer, weatherproof "Solar" connector but it looks like overkill, and there isn't even a price listed yet. The fallback option is a good, heavy AC extension cord or two, cut in half. I've never ridden the bike under full throttle for more than a second or so, including up hills. Actually, I've *never* ridden at full power up a hill, only on level road.

 

[DrkAngel]

Hi Top Munch Sak - $5.99 (K Mart)

Various colors available in store?

 

[Allex]

Will I get the same amount of range with same amount of Wh?
Example:
37V20Ah will get me 20km
What happens if a connect them like:
74V10Ah
Still same amount of Wh, but will i get the same range?

 

[DrkAngel]

Will I get the same amount of range with same amount of Wh?
Example:
37V20Ah will get me 20km
What happens if a connect them like:
74V10Ah
Still same amount of Wh, but will i get the same range?

Only if you run at the same speed, acceleration ... etc.

 

[alsmith]

Will I get the same amount of range with same amount of Wh?
Example:
37V20Ah will get me 20km
What happens if a connect them like:
74V10Ah
Still same amount of Wh, but will i get the same range?

Only if you run at the same speed, acceleration ... etc.

Not in the real world then!

 

[LeftieBiker]

Hi Top Munch Sak - $5.99 (K Mart)

Various colors available in store?

Thanks! looks like I'll have to visit a store. though. There are worse colors than "red" but I'd prefer something less eye-catching.

 

[DrkAngel]

An eZip with 29.6V 31.2Ah pack, (8s12p), without any regearing, will push to (legal - USA) 20mph capability!
With a substantial torque increase ...
A 24% torque increase, as opposed to the 20% (initial) torque decrease associated with 16T or similar with the 13T mod.

Hill climbing capability seems impressively increased!

Torque-speed comparison between oem 24V and proposed 29.6V battery build.
Also charts 24V w/16T mod.
Targeting for the USA "legal" 20mph.



I am hoping that additional heat production be manageable.
Since I have successfully run the same setup at 37V for thousands of miles, should present no problem ... for me.
Looks to provide excellent available torque, 200% of 24V at 12.5mph, a good minimum hill climbing speed.
Best of all the 29.6V pack should have the same energy usage at 20mph cruising speed.
Great acceleration and hill climb ability when necessary but the same cruising energy usage as the 24V w/16T mod.
More power, if and when you want it!

And 29.6V 31.2Ah cells fit in the same eZip case as my previous 25.9V 31.2Ah builds. (a 14% Wh increase)

 

[DrkAngel]

An eZip with 29.6V 31.2Ah pack, (8s12p), without any regearing, will push to (legal - USA) 20mph capability!
With a substantial torque increase ...

Placing 29.6V eZip packs into production.
Ordered 2 iMax B8's from HobbyKing.com, 2, to save shipping.
Found 8s balance cables-connectors, might attach a 9pin serial connector to pack and use computer serial cable for balance-monitor.

I plan on building 2 - 8s 29.6V 31.2Ah packs.
Primo pack will use 96 2600mah cells that maintain 4.22-4.24V after being charged to 4.25V and left setting for 3 months.
Segundo pack will use 96 2600mah cells that maintain 4.18-4.20V after being charged to 4.25V and left setting for 3 months.
Peak charge will be 4.10V.

They make no specifically compatible controller (33.6V full charge) but I do have 1 2008 eZip that handles 24-36V, and I have modified a 12-36V 25A controller ,with deans plugs to the oem connectors, from a bad eZip controller.
So I can swap various "universal" controllers into any of my eZips.

I plan on running a heavy tinned copper braid as the power rails between banks and extending directly to the pack contacts.
Hopefully, the heavy copper braid will act as an effective heat dispersion "sink", keeping the contacts form getting too warm.
(Same tinned copper braid as used on 22.2V 41.6Ah)

I'm still pondering possibilities for cooling the bike contacts as well.

Might take a couple weeks to get chargers and cables, but should have pack ready sooner ... for test runs.

Will also have a recycled Lipo pack, or 2, or more, put together.
Gotta rebuild my 2 year old 25.9V 25.92Ah with top quality cells (and treat better 3.7V-4.05 working range), and
will build 11.1V modules in 25.92Ah, 30.24Ah, or larger?
For modular builds of 33.3V, 44.4V etc.
11.1V module as emergency power through 12V DC to 120V AC inverters.