72 Volt System, What Are My Options?

[blackstangt]

$500 MAX

If I go lead acid, I need 6x 12 volt, 35-40 Ah, what are my other options?

I know better batteries will give me the same range at lower Ah ratings, so keep this in mind.

Lithium, gel, etc?

 

[Link]

I'm pretty sure you can't even afford lead with only $500. Even my cheap PS-12350 35Ah battery cost me nearly $100.

$1000 would be a much better budget, if you can swing it.

 

[safe]

72 volt - 18 Ah

UB12180-B1 Universal 12 Volt 18AH Battery

http://www.batteriesasap.com/46.html

$33.92 * 6 = $203.52 + Shipping (which is usually not cheap)

Which translates to 1296 Wh... but after Peukert's Effect you should only expect to get about 700 Wh... still pretty good... :wink:

Weight: 13.1 lbs * 6 = 78.6 lbs (about the same as mine... in fact this is one modification I've considered before because two of the 18 Ah's fit in the same space as one of the 40 Ah's)

 

[TylerDurden]

My Vote...

500 bucks in sub-c nicads (shipping included):

200 pieces @ 2.1Ah = 504Wh

25lbs

Rapid recharge

>2000 cycles

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=162

You might want to ride more than one time per day... lead won't.

 

[blackstangt]

I found cheap Gel batteries at Wal-Mart...

12 volt, 75 Ah, Gel, Deep Cycle Marine batteries = $55

I need about 40 Ah, so lets say $50 with core charge = $300

I'm going to buy my frame first, and then worry about the exact size, but these seem like the best deal around.

Your suggestions give too low Ah rating...

 

[safe]

Breaking News

Scientists have discovered that lead is actually very heavy.

(just kidding... had to add some effect)

How are you going to build a bike with more than 100 lbs of lead? I had to build a custom frame and all I can say is that things like hubs and spokes start to break when you hit bumps at 50 mph while carrying so much weight.

I'm just not sure how you could build anything less than a motorcycle with so much weight.

53 lbs * 6 = 318 lbs

 

[safe]

You might want to ride more than one time per day... lead won't.

:? What?

I've been able to get as many as three rides in one day. It all depends on the ability of your charger to deliver current. I use a 10 amp charger. Most of the cheap one's deliver about an amp or two.

 

[TylerDurden]

I've been able to get as many as three rides in one day.

4hrs - 8hrs per charge. *yawn*

 

[EMF]

How are you going to build a bike with more than 100 lbs of lead? I had to build a custom frame and all I can say is that things like hubs and spokes start to break when you hit bumps at 50 mph while carrying so much weight.

He could put mags on a cheap steel frame add some gussets here and there. A quick google turned these up - 89 dollars for the pair, then go on a diet to help offset the weight of the batteries. (I did!) What would be cool also is some kind of trike. You could put batteries low and have storage on top. Of course you would need a front wheel drive, which might be a problem if the batteries were behind the rear axle. Just have to keep them a bit forward. THe trike on ebay can carry 500 pounds! You don't even need the mags or do any welding. This would make an interesting errand runner.

http://cgi.ebay.com/NEW-TRIKE-TRICYCLE-INDUSTRIAL-wheels-24_W0QQitemZ150236336630QQihZ005QQcategoryZ106945QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

http://www.coloredtuffs.com/shop/index.php?searchStr=mag+wheel&act=viewCat

 

[Link]

I'm just not sure how you could build anything less than a motorcycle with so much weight.

Good thing he's building a motorcycle then, innit?

 

[blackstangt]

Breaking News

Scientists have discovered that lead is actually very heavy.

(just kidding... had to add some effect)

How are you going to build a bike with more than 100 lbs of lead? I had to build a custom frame and all I can say is that things like hubs and spokes start to break when you hit bumps at 50 mph while carrying so much weight.

I'm just not sure how you could build anything less than a motorcycle with so much weight.

53 lbs * 6 = 318 lbs

more like 30-35 lb for what I'm going to end up using

SO 180-210 lbs...

And it is a Motorcycle. Probably a Kawasaki Ninja 250 Chassis, gonna look cool too.

 

[blackstangt]

I've been able to get as many as three rides in one day.

4hrs - 8hrs per charge. *yawn*

I'm going to have a 2.5-3.5x the range I need for my commute. I can ride to campus, the store and a friend's house on the same day, good enough. If I can charge it at school, even better.

 

[blackstangt]

How are you going to build a bike with more than 100 lbs of lead? I had to build a custom frame and all I can say is that things like hubs and spokes start to break when you hit bumps at 50 mph while carrying so much weight.

He could put mags on a cheap steel frame add some gussets here and there. A quick google turned these up - 89 dollars for the pair, then go on a diet to help offset the weight of the batteries. (I did!) What would be cool also is some kind of trike. You could put batteries low and have storage on top. Of course you would need a front wheel drive, which might be a problem if the batteries were behind the rear axle. Just have to keep them a bit forward. THe trike on ebay can carry 500 pounds! You don't even need the mags or do any welding. This would make an interesting errand runner.

http://cgi.ebay.com/NEW-TRIKE-TRICYCLE-INDUSTRIAL-wheels-24_W0QQitemZ150236336630QQihZ005QQcategoryZ106945QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

http://www.coloredtuffs.com/shop/index.php?searchStr=mag+wheel&act=viewCat

That's pretty sweet, I'm building a motorcycle to go 45+ MPH though, otherwise for an e-bicycle it would be awesome.

 

[blackstangt]

I'm just not sure how you could build anything less than a motorcycle with so much weight.

Good thing he's building a motorcycle then, innit?

lol

 

[TylerDurden]

Keep in mind most EVers spend the bulk of the $$ on batteries for good reasons. Safety, reliability, power, weight, space and lifecycle.

We can mostly agree that any flooded system (no-gel) is to be avoided on a vehicle that can fall over.

Malcom's bike is probably the closest example of what you propose, but he bought some nice Hawker SLA batts that cost a bit more than $5C.

http://www.endless-sphere.com/forums/viewtopic.php?t=465

As stated by others, the batts you can get for $500 *might* do the job marginally for a year.

I'm as cheap as anyone in the group (cheaper actually)... that's why I bought lithium. They're cheaper in the long run.

 

[blackstangt]

I would love to spend more on batteries, but it's only got to last about 8 months, then I'll have a real job...(graduating) The cost of batteries is 'make or break' for the budget, finding these batteries at wal-mart put me within budget, and make the project possible.

I'm pretty sure they're gel, so they're safer than regular lead acid batteries.
They give a lot of Ah, more than any other battery for even close to the price.
Deep-Cycle = longevity in lead acid world.

The advantage of buying better batteries is not worth the cost on my project, I can always switch when I have the money.

 

[safe]

A Word About SLA

When you use SLA it's either possible to get a lot of value out of them or to throw your money away. It all depends on how you design your system. This chart gives some idea about how you might select your Ah rating in order to set up a machine that had a 40 amp current limit. You can see how the decline rate is important because it's actually the ability to achieve your peak current that declines with time that you notice.

So... good design... good economics.

Poor design... you lose money.

Every year you lose about 20% of your capacity... so you need to ensure a little excess capacity (ideally double or more) so that a battery with a slight decline can still deliver enough to do the job it once did. SLA's cam only pull 5C maximum and that's relative to it's current capacity that drops with time. (so 5C on day one becomes 80% of 5C compared to day one after one year)

You can see that a 40 Ah battery can be kept in use for an extra year over a 20 Ah battery, but that's about it. So there is a "middle ground" that is ideal.

Too small and the decline in peak amps is the problem.

Too big and your up front investment is lost because of shelf life issues.

Example:

If someone made the mistake of using a 10 Ah battery on an ebike that uses a 40 amp current it would work fine for about a year then it would no longer be able to deliver enough current to achieve peak amps. That battery would be junk after only a year.

 

[blackstangt]

so If I need a 33.3 Ah battery for my range (which is about right), I should use about a 55Ah battery, so a year from now I can still go the distance needed.

This is pretty strange, because I beat up my car battery pretty badly, killing it over and over (bad alternator) and I checked it at Autozone, and it exceeded it's design specifications for these ratings, 2 1/2 years later. Maybe it's just a really good battery (normal lead acid), but I killed it over and over.

 

[kbarrett]

Most Lead-Acids aren't designed to take complete discharges and recharges on a daily basis.

Number of complete cycles are what is going to eventually kill them.

Accidentally draining your car battery and recharging it once in while doesn't compare to hammering the sucker and recharging it twice a day for your commute.

 

[blackstangt]

Most Lead-Acids aren't designed to take complete discharges and recharges on a daily basis.

Number of complete cycles are what is going to eventually kill them.

Accidentally draining your car battery and recharging it once in while doesn't compare to hammering the sucker and recharging it twice a day for your commute.

The comparison I'm making is that a battery that is not designed to take deep discharge was left for a day here a day there, completely dead... This wasn't a couple times, I'd say maybe 40+, 2 1/2 years later, completely fine, up to brand new specs.
A marine deep cycle battery, which is made for this abuse should be able to handle more than that and still be 'like-new'.

regular lead acid - 40+, 2 1/2 years - 'like new'
marine deep-cycle - 100-150 discharges in 8 months should be 'like new'

Taking into account that I'm not going to be discharging these as thouroughly as my bad alternator was (dome light wasn't even coming on), this seems reasonable.

With my 72v 40+ Ah capacity which should give me 15+ miles and 6-7 mile round trip, they won't be getting abused too badly.

 

[monster]

i'ld go for NiCd over lead any day.

lead is dead !

 

[blackstangt]

Whatever, isn't nicad dead as well, being replaced by newer, safer technology?

 

[TylerDurden]

Whatever, isn't nicad dead as well, being replaced by newer, safer technology?

For low-drain applications, NiMh has replaced NiCd. RCers still use NiCd (if not lith), since it can pull serious amps.

For my bike, I decided it would be a better value to buy my LiMn batteries on credit, than to buy lead and upgrade in a year:
1) instant benefit from reduced weight and size
2) recharge in an hour = many more trips per day
3) no need for retrofit in 1 yr... a big deal for a motorcycle
4) 7% per annum ($70) is less loss than $500 after one year's use (or two).

Note: My bike is a tool, not a toy. I use it like any other tool. I wouldn't buy five shitty drills in a row, instead of one good drill at the outset... especially if the five shitty drills cost me two times more in the long run.

 

[safe]

Most people using SLA batteries for ebike applications are using unrealistically small Ah ratings because they have no ability to carry the considerable weight of lead. If you can find a way to carry the larger amp hours then the economics get to be very good.

So it's a flawed message to say that "Lead is Dead"... it's not a good solution for someone without the ability to build a custom ebike, but if you really do your homework the price to performance ratio is still pretty good.

It's hard to beat SLA's from the economic angle if you use them in the proper sizing.

When it comes to SLA's it's:

"Sizing, Sizing, Sizing..."

 

[blackstangt]

Whatever, isn't nicad dead as well, being replaced by newer, safer technology?

For low-drain applications, NiMh has replaced NiCd. RCers still use NiCd (if not lith), since it can pull serious amps.

For my bike, I decided it would be a better value to buy my LiMn batteries on credit, than to buy lead and upgrade in a year:
1) instant benefit from reduced weight and size
2) recharge in an hour = many more trips per day
3) no need for retrofit in 1 yr... a big deal for a motorcycle
4) 7% per annum ($70) is less loss than $500 after one year's use (or two).

Note: My bike is a tool, not a toy. I use it like any other tool. I wouldn't buy five shitty drills in a row, instead of one good drill at the outset... especially if the five shitty drills cost me two times more in the long run.

$300 or so for my batteries...
No money for the other types.
they'll be cheaper when I have them money, possibly paying for my lead ones.