Replies to This Discussion

Permalink Reply by Brendan on October 11, 2009 at 1:48pm

I use 12v Ni-MH batteries. You can find them on a few different hobby websites (battery zone, I think?). They are primarily designed for model robots. They are relatively lightweight, really compact, and work well with a smart charger. I have also never had any trouble with them in cold weather. They are pretty pricey though.

Permalink Reply by buddaa38 on October 11, 2009 at 4:33pm

I use 2 wheelchair batteries. I've never run out of power. I have 1400 watt car amps. I got mine at battery plus .com or go to the store.

Permalink Reply by Spencer "Thunderball" Thayer! on October 11, 2009 at 4:53pm

Brendan,

How long does your setup last and how many do you have?

Howard,

I agree for the most part it should be people powered. But part of the reason why I want to upgrade is because I want my girlfriend to be able to use this too. So I may one day mod it with an electric assist motor but it's not in the initial plan but it's a possibility I am going to keep open to. But I think gears would be all she'll need.

Anyway thanks for the tips I'll look into them.

Permalink Reply by Todd Allen on October 11, 2009 at 7:12pm

There really is no best. There's lots of tradeoffs. The lithium ion batteries I use on my sound system I wouldn't have actually selected for my system if I had to buy them for that purpose. I got them to power my electric bike. But after a few years of that duty they had degraded to where they were no longer fit for that use but still work ok for powering my sound system.

The downside of lithium ion and lithium polymer for sound system use is that they degrade more by time than by useage, ie whether you use them every day or once a month doesn't matter too much. You can slow the degradation by storing them in a refrigerator but still due to their cost I wouldn't recommend them for infrequent useage.

Nimh batteries suffer similarly although a new variety often referred to as "low self discharge" such as the Sanyo eneloops have a much better shelf life. However, I've only seen these in a AA size. For a sound system you will need larger capacity batteries. And you can't charge nimh batteries in parallel arrays.

There's a relatively new form of lithium battery, called lithium iron phosphate, that should in theory have a much longer shelf life but they have just slightly better energy density than nimh at a significantly higher price. And they are fairly new so it remains to be seen which brands will actually achieve the advertised life spans.

There's also a new form of lead acid battery that uses a lead foam electrode. These will likely replace the Optimas as the new gold standard for AGM type lead acid batteries as they have significantly better performance. But currently they are only available in a 75 lb size - kind of big for sound system use.

If you were building an all new system from scratch, I'd first try to select the speakers. They vary greatly in efficiency and sound quality. Then try and find an efficient amp that is a good match for the speakers. Start off using whatever old battery you can scrounge up. After you know how much power your system takes at the volume levels you want to run then you can calculate how much battery you will need for a given run time.

Once you know the battery capacity you need and how much battery weight you'll tolerate then you can pick the type of battery - at least so far as funds allow. Or if you are afraid of being criticized for not being a self powered purist then you should skip the battery altogether and go with a pedal powered generator system. Of course it will suck to power it unless it is very small or you are Lance Armstrong.

As for the appropriateness of electric bikes on the mass, I'd say for the most part they fit right in. There are some models which make an annoying whining sound but there are plenty that are quite stealth. And even though I've been riding electric bikes on the mass for many years and they are finally becoming a somewhat more common sight most riders are still blissfully unaware when there is an electric bike in their presence. I'd say claiming a silent electric bike doesn't fit in makes about as much sense as complaining that exotic racing bikes don't fit in. If that is what people enjoy riding and they ride at the group's pace, then what does it matter? Although many cycling events are about demonstrating one's superior fitness or speed that isn't what the mass is about.

Permalink Reply by Brendan on October 12, 2009 at 5:49am

I have something similar to this: http://www.batteryspace.com/nimhbatterycombo12v13ahbatterycharger96...

It kind of depends on how loud I am playing it, but I can usually get about 4 - 5 hours of playing time. I have a few different battery packs of different sizes that I will combine in parallel array depending on how far I am going and/or if there will be a CM that night.

Todd had some excellent points. I definitely agree that you should start with your speakers and work from there. I originally started with really cheap speakers an AutoZone had on clearance and a lead-acid motorcycle battery. It took me a while to find the right balance of output and power with new speakers and batteries.

The Nimh batteries will self-discharge at a non-trivial rate, so I usually have them rotating on a smart charger. However, as Todd mentioned, it does not work to charge them in parallel.

Since your goal is to make one huge rocking system, I'd start with the best speakers you want to use, and see what you can find to make to go. I use my system on my bike for every day commuting so light weight convenience is more a priority.

I also second Todd's opinion that there is no shame in electric bikes. One of the best aspects of CM is seeing all the different kinds of bikes out there.


Spencer "Thunderball" Thayer! said:

Brendan,

How long does your setup last and how many do you have?

Howard,

I agree for the most part it should be people powered. But part of the reason why I want to upgrade is because I want my girlfriend to be able to use this too. So I may one day mod it with an electric assist motor but it's not in the initial plan but it's a possibility I am going to keep open to. But I think gears would be all she'll need.

Anyway thanks for the tips I'll look into them.

Permalink Reply by Spencer "Thunderball" Thayer! on October 12, 2009 at 7:00am

Brendan,

I already have a setup that is suitable for what I need at the moment and I cannot justify replacing the speakers or the amp when they work wonderfully well. I just want a lighter more efficient power source in conjunction with a more stable less prone to breaking trike on which it all will sit. Thanks for the input!

Permalink Reply by Spencer "Thunderball" Thayer! on October 12, 2009 at 10:31am

The Optima Yellow Top is 26 pounds that's a lot.

Permalink Reply by buddaa38 on October 13, 2009 at 7:50am

Did you check out battery plus. That's were I bought mine. I run 1400w amp's. (2)6x9"s (1)10"w, (1)8"w. Have yet to run out half way down. I have 2 35ah. I'd like to get one at maybe 80/90ah. They're small & compact.

Permalink Reply by Todd Allen on October 13, 2009 at 8:01am

It's good you are happy with your audio components. That makes your task well defined. And it makes it possible to know how much power you need.

What is your current power source? I know it's a lead acid battery, but do you know what make/model
/year? Or at least how heavy it is and what its amp hour rating is? I can run a capacity test on your current battery and tell you what it is now. If the battery is old it might be well below its original rating. In which case you might do fine replacing it with the same one if you need more capacity or a smaller one to get the same capacity at a lower weight.

If you want a significantly lighter battery though you'll have to go with a different chemistry such as nicad, nimh, lithium iron phosphate, lithium ion or lithium polymer.

I listed those battery types in terms of increasing energy density by weight. Nicad is about 1/2 the weight for the same capacity as lead all the way up to lipos which can be as little as 1/6 the weight for the same capacity. Unfortunately, those are also listed in terms of increasing cost. And if you go with expensive batteries you'll really should buy a quality charger and quite likely a battery manager/alarm to avoid over discharging too.

And every chemistries has its quirks and drawbacks. Lead batteries suck in cold weather. Nimh can't do high discharge rates in the cold. Nicad are super tough but ironically can be damaged by simply sitting unused for too long. They are also very toxic and are getting increasingly harder to find. Nimh self discharge and need to be charged just before use and are prone to being overcharged and slowly cooked to death by cheap chargers. All of the lithium batteries can be damaged by discharging too deeply. And lithium ion and lipos can burn/explode if charged improperly or discharged at too high a rate.

And all batteries are damaged by high temperatures, especially prolonged storage somewhere hot, although lead and nicad are more tolerant of heat than the other battery types.

If I was going to buy new batteries for my sound system I'd probably go with lithium iron phosphate (LiFe). But it is a fairly expensive way to save weight. If you are currently using 35 lbs of lead you might cut that to 12 lbs of LiFe. But you might be able to save 20 lbs more cheaply by using lighter materials for your speaker enclosures, trailer/vehicle, etc.



Spencer "Thunderball" Thayer! said:

Brendan,

I already have a setup that is suitable for what I need at the moment and I cannot justify replacing the speakers or the amp when they work wonderfully well. I just want a lighter more efficient power source in conjunction with a more stable less prone to breaking trike on which it all will sit. Thanks for the input!

Permalink Reply by Spencer "Thunderball" Thayer! on October 13, 2009 at 8:26am

Todd, let's talk Turkey tonight at the CCW Patrol. I don't have the equipment to do said tests and I would love to do it.

Permalink Reply by Madopal (16.5 mi) on October 30, 2009 at 5:55am

Chiming in late...

When I was building my setup originally, I didn't find any good source 12V batteries, so I just opted to buy a bunch of 2600 mAh NiMH AA's. Amazon had 4 packs for less than $1 a battery.

Doing a quick search, looks like you can still get the 2600 mAh ones for fairly cheap.

http://www.all-battery.com/freeshipping24pcsofaa2600mahhighcapacity...

Anyway, then I just got a bunch of 10 pack AA holders from Digikey, and I have 3 of them. My amp can take up to around 14V, so the effective range goes from like 14.4 V down to 11.5 V or so. With my small T-amp, I can get about 3 hours per 10 pack. I haven't done extensive testing, but my anecdotal trials have bore that out.

And I echo Todd's comments. The downside of having the NiMH is that I have to do charging the night or two before, and the new smart charger I have is much slower. So I really have to plan my outings.