Building a rechargable battery pack

[gilesw]

Hi AOSERS,

I've ordered a class d amp that can be powered using 2x 12v batteries with a charger:-

http://www.audiocircle.com/index.php?PHPSESSID=re4389asj7spp18dqht2fjj9k2letv fp&topic=108242.0

Do any of you know a UK supplier of this sort of thing.

The other battery related device I'm considering is this:-

http://www.m2tech.biz/palmer.html

but at 800 euros it seems a bit over priced to say the least...

[Martinh]

Hi AOSERS,

I've ordered a class d amp that can be powered using 2x 12v batteries with a charger:-

http://www.audiocircle.com/index.php?PHPSESSID=re4389asj7spp18dqht2fjj9k2letv fp&topic=108242.0

Do any of you know a UK supplier of this sort of thing.

The other battery related device I'm considering is this:-

http://www.m2tech.biz/palmer.html

but at 800 euros it seems a bit over priced to say the least...

Hi Giles,

800 euros to power a 500 dollar amp seems like a lot. Also, the m2tech unit uses LiPo cells, which are not suitable for domestic use IMHO. Other manufacturers of battery powered hifi (i.e. J Kenny) use LiFe cells, which are more suitable, as they are more robust and more forgiving of abuse.

The problem with all of the Lithium type cells is that they need a special charging regime and mustn't be allowed to over discharge. The old type Nicad, Nimh and lead acid cells are easy to charge and don't become unstable/damaged if overcharged or over discharged.

I would recommend trying your new amp on battery power before spending any money. It's easy to do and wont cost much to try it. I can send you an old (old but still great for what you want to do) Lipo pack FOC if you are interested in giving it a go.

Maybe also consider something like a decent linear supply like the Mark Grant S-booster unit (assuming that its powerful enough), as many people on this forum have tried it against battery power with great results.

Cheers,

[sq225917]

The M3Tech unit uses A123 batteries, if they are good enough for almost every electrical vehicle manufacturer it's safe to assume they will be good enough for a bit of hifi.

[Martinh]

The M3Tech unit uses A123 batteries, if they are good enough for almost every electrical vehicle manufacturer it's safe to assume they will be good enough for a bit of hifi.

The spec says its a lipo :scratch: did you not see that?

If they got it wrong and its an A123 (LiFePO4) then that's good. :)

Martin

[gilesw]

Heya Martin,

I read your reply with great interest regarding the battery types. I am totally new to this side of hi-fi so I freely admit to not knowing what the hell I'm on about.. I mentioned the m2tech because I have a young dac so I've been thinking about a psu for that, not the amp. I'm going to hopefully get one on loan next week along with a squeeze-upgrade 15v power supply. That way I'll be able to compare the two side by side in my own system. I'll be sure to post the review here!

g.

[sq225917]

It was lost in translation Martin.

[NRG]

A123 cells are not LiPo....Lithium Polymer is a type of cell construction.

A123 are as stated LiFePO4...they are more durable than LiPo and can withstand more abuse, they would make a good battery supply. You will still need to balance charge them now and again and provide some form of low voltage cutoff protection but they are more robust than RC LiPo cells.

[gilesw]

This is my plan:-

2 x ULTRA MAX 12V 12Ah (as 14Ah & 15Ah) - MOBILITY SCOOTER WHEELCHAIR BATTERIES | eBay

Plugging them together in series.

Which should give 24Ah total so should give a decent charge time.

I need a cable and connectors to connect the batteries together, presumably I could just solder on any sort of wire.

and a cable for connecting the battery terminals to the amp, I could cut up one of these:-

Universal AC DC 3 Pin UK Mains Power Plug Adaptor 300mA 3v 4.5v 6v 7.5v 9v 12v | eBay

And then something to charge it with:-

12 VOLT TRICKLE BATTERY CHARGER 12V CARAVAN/CAR/BIKE/QUAD/MOTORHOME ETC | eBay

I also need to get hold of some sort of inline voltmeter so I can see what it's putting out. I'm struggling to find any websites for these sorts of components. I suppose there is always maplin, but they tend to be a right ripoff.

[Martinh]

Hi Giles,

Yes, your plan looks good to me - don't forget to put an inline fuse in circuit (connected to the battery +ve terminal), as short circuit could be nasty otherwise.

One thing though is that I'm not sure about how good a lead acid is in terms of sound quality. It's not just the smoothness of the voltage, but also the ability of the battery to deliver current fast enough. I'm not qualified to say if it would be better than a PSU or lithium type battery. Maybe someone else can comment?

Maplin is good for the short lengths of cable you need, I reckon. Go for nice flexible cable and use heat shrink to ensure that there's no chance of a short circuit.

[NRG]

This is my plan:-

2 x ULTRA MAX 12V 12Ah (as 14Ah & 15Ah) - MOBILITY SCOOTER WHEELCHAIR BATTERIES | eBay

Plugging them together in series.

Which should give 24Ah total so should give a decent charge time.

I need a cable and connectors to connect the batteries together, presumably I could just solder on any sort of wire.

and a cable for connecting the battery terminals to the amp, I could cut up one of these:-

Universal AC DC 3 Pin UK Mains Power Plug Adaptor 300mA 3v 4.5v 6v 7.5v 9v 12v | eBay

And then something to charge it with:-

12 VOLT TRICKLE BATTERY CHARGER 12V CARAVAN/CAR/BIKE/QUAD/MOTORHOME ETC | eBay

I also need to get hold of some sort of inline voltmeter so I can see what it's putting out. I'm struggling to find any websites for these sorts of components. I suppose there is always maplin, but they tend to be a right ripoff.

Connecting them in series will give 24v and 12Ah....I think you meant parallel 12v and 24Ah.

Lead acid batteries can delivery huge amounts of short term current so you should have no issue.

If the charger is an 'intelligent' type it will look after the voltage for you...all you would need would be a changeover switch...battery to load or battery to charger.

[NRG]

If the charger is the one I think you are buying then I'd say its not appropriate.

This is the sort you need to get:

http://cpc.farnell.com/ideal-power/ac0212a/charger-12v-2a-lead-acid/dp/BT03796


It has the correct charge profile for SLA IE: Fast, Normal and Float with auto shutdown on full charge and reverse polarity protection.

[daytona600]

small Off grid 12/24v solar panel with a charge controller to feed the battery

[gilesw]

Thanks for that link NRG, that site looks like the sort of thing I need for UK parts. I've done some more investigation though and it turns out scooter parts are the way forward for a 24v pack. I found all the parts I need from a UK site and have documented here:-

http://www.diyaudio.com/forums/power-supplies/218070-building-24v-battery-pack-tbi-millenia-2.html

I'm not buying anything till the amp arrives though.. see if I like the thing first.