Anyone know which hour rate ebike maufacturers typically use when labelling their batteries? For instance, my bike has 12V20AH cells... but is the 20AH measure a 20 hour or 5 hour measure? Would be important for matching their capacity on replacement/upgrade batteries.

There's a nice battery chart here:

http://www.mobilityun...

-Vic

Neat, thanks. I suppose I'll take their use of a Powersonic battery in the picture as being another vote of confidence for that brand.

Actually, this *sounds* like yer talking about a DC to DC converter... Ya plug it into eg 48V and 12V pops out the other side?

Nah, I was intending on keeping the stereo's electronics completely seperate from the motor's. That way, if I drive somewhere, park, and turn on the stereo, I know that I'm still going to have the same amount of juice left for the motor as I did when I parked. I'd rather have the stereo stop and lose my music than have the motor run out of juice.

OK. Gotcha. Depends on how big a system ya want to run maybe. This kit for a stereo amp is rated to output 2x 38W:
http://www.sparkfun.c...

Otta be enough to drive these OK:
http://www.motorcycle...

If the thing was only 80% efficient it'd still be consuming less than 100W... Will ya be running separate batteries for your lights too (wink)

...don't happen to have a link to those 25A ones, do ya?

Fred mentioned them here:
http://www.ebikerider...

...from Urban Mobility in Montreal, here:
http://www.urbanmotio...

As far as chargers, I've been glancing at these two over at Canadian Tire. Any reason to prefer one over the other for purposes of pack balancing? If I'm reading the specs right, the second one might be a little quicker at it.
http://www.canadianti...
http://www.canadianti...

Yup, the second charger has a 6A option... would charge your pack in 1/3 the time approx. Caveat is, SLA batts have a limit to how fast you should charge them. Check the specs on those Power-Sonics you mentioned, for example. It'll work out to 20% of their rated Ah capacity I believe so for a 20Ah pack that'd be a max of 4A charge rate. They'll take 6A (full recharge from 20% to 100% in 2hrs 40mins flat!)...but this will likely shorten their cycle life

One nice thing about Power-Sonic is that they offer their own chargers as well so these should be exactly matched to their own batteries.

Thanks for all the advice so far, you're a wealth of information.

Yer welcome! I've wasted my life as an accountant. Been trying to understand all this battery etc stuff myself so it helps me to write it down. And in a public forum in the hopes that others can correct my mistakes and oversights...

I don't know why I am telling you all about lead packs... After almost ten years of beating myself up rolling on lead, I bought lithium

Probably just a more expensive way to beat myself up, but I want to try...

loCk

Anyone know which hour rate ebike maufacturers typically use when labelling their batteries? For instance, my bike has 12V20AH cells... but is the 20AH measure a 20 hour or 5 hour measure? Would be important for matching their capacity on replacement/upgrade batteries.

Hi Greg... the battery manufacturers all use the same standard... a C/20 rate. In other words, a 20Ah batt will deliver ONE AMP for 20 hours. So you can use their rated Ah capacities to compare apples and apples, it's just that you always end up with oranges when you discharge the batts at faster rates.

Power-sonics came up here already. Here's their technical manual as a PDF:
http://www.power-soni...

Look at Table 2 on page 5. They rate their batts based on diff discharge rates. For their 12V 20Ah batts:
20hr...rate...20Ah
10hr.............18.5Ah
5hr..............17.0Ah
1hr..............12.4Ah (!)

So if ya run these Power-Sonics completely down in say 2hrs, the actual Ahs you will see will only be somewhere between 12.4 and 17Ah...

All lead acid batts behave like this

Some might do better than others. Depends on quality of design and construction... Best you can do is compare the detailed specs from the diff manufacturers but for the China made batts these are often unavailable or incomplete.

Lock

OK. Gotcha. Depends on how big a system ya want to run maybe. This kit for a stereo amp is rated to output 2x 38W:
http://www.sparkfun.c...

That kit looks a fair bit nicer than what I was thinking originally (either to disassemble an iPod dock stereo and use the internals from that, or to try to get Veloteq to send me the parts they use to install the stereo available as an option in their bikes), I may end up ordering one.

But just to make sure I'm doing this right: (2x38)/12 means that thing would draw, at maximum power, 6 and 1/3 of an amp, right?

Yup, the second charger has a 6A option... would charge your pack in 1/3 the time approx. Caveat is, SLA batts have a limit to how fast you should charge them. Check the specs on those Power-Sonics you mentioned, for example. It'll work out to 20% of their rated Ah capacity I believe so for a 20Ah pack that'd be a max of 4A charge rate. They'll take 6A (full recharge from 20% to 100% in 2hrs 40mins flat!)...but this will likely shorten their cycle life

Yeah, I'd noticed the 6A output but wasn't sure if this was desirable/useful. Sounds like, for the kinds of batteries I'm dealing with, 6A would be overkill.

So if the intent of it is for balancing use and potentially for charging the small stereo battery, I don't really need the 6A option and can get whichever one's in stock. Cool.

That kit looks a fair bit nicer than what I was thinking originally (either to disassemble an iPod dock stereo and use the internals from that, or to try to get Veloteq to send me the parts they use to install the stereo available as an option in their bikes), I may end up ordering one.

Note too that the folks that sell those speakers also sell similar with amps built into the speakers. Might be a cleaner way to go (for more money of course):
http://www.motorcycle...

But just to make sure I'm doing this right: (2x38)/12 means that thing would draw, at maximum power, 6 and 1/3 of an amp, right?

Yup. at 12V supply. It's rated up to 22V and at that max V for 76W it'd only be sucking 3.45A (this ignores losses in the amp - why I rounded up to say might draw less than 100W. At 12V 100W would be 8.33A. These are all max/worst case power numbers too. Actuals should be less if you are not cranking the volume up to 11 all the time.

I've opportunity charged, plugging into outlets all over town. I'm never too worried about being able to find *somewhere* to plug in, parks included!

Lock

Here's a link I stumbled on that looks pretty informative regarding Deep Cycle Batteries - Q&A.

Can't find if this one has been posted elsewhere in the forum, so apologies if it is a dup.

The Battery University link I know has been posted before, but am putting it here for those who may not have seen it. It is a very good tutorial on battery technology, charging, etc.