Building a 24v battery pack to tbi millenia

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gilesw

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Joined 2012
#1
Hi all,

I'm looking for some advice on building a battery pack in the UK. The amp can draw 3A at 24v when using it's a/c power pack so I'm looking at these batteries:-

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

Please go easy on me, I've never done anything like this before!
 
#2
Proceed with caution; the max recommended supply voltage for the amplifier IC in that unit is 26V with 30V being the absolute maximum rating (meaning don't come close to this or SMOKE!).

Two SLA batteries in series off a fresh charge can supply upwards of 27V.

I would hate to see you fry that overpriced little chipamp. 😉
 
#4
A fuse won't protect the IC from overvoltage.

It might be fine with ~27V, but that's really pushing it's limits. Not sure who would be willing to test that out on a $500 amp. Just trying to give fair warning.

Sorry, didn't mean to offend you by calling it overpriced. The product is based around a $4 amplifier IC and the manufacturers decsription of the unit comes off as pure hyperbole.... that's a real turn off to me. This is all OT though so I'll shut up now.
 
#5
I'm sure if I had the skills I could build a class d amp for a tenth of the price but I don't. I'd like to be using one of these hypex ncore kits I've been reading about, they come in mola mola amps that seem to retail for $1000's but it's not going to happen with my knowledge level. I can solder okay but I'd probably blow it up before I got it built.
 
#6
theAnonymous1 said:
A fuse won't protect the IC from overvoltage.

It might be fine with ~27V, but that's really pushing it's limits. Not sure who would be willing to test that out on a $500 amp. Just trying to give fair warning.

Sorry, didn't mean to offend you by calling it overpriced. The product is based around a $4 amplifier IC and the manufacturers decsription of the unit comes off as pure hyperbole.... that's a real turn off to me. This is all OT though so I'll shut up now.
Click to expand...

Unless you have actually listened to it, you should not be running your mouth about it. 🙄

I have listened to this amp with the battery, and it sounds FAR better than most amps within the power range on a 24 volt SLA battery. It is shocking (no pun intended) how good this thing sounds. It puts most low power amps to shame by comparison. 😱

The OP will be very happy with this amp once he gets the PS in house. :drink:
 
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#7
If you connect the batteries in series to get to 24 volts dc (28 at full charge) that will still only give you 12 ah capacity. In parallel you would get 24 ah, but at the same voltage as one battery.
 
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#8
theAnonymous1 said:
A fuse won't protect the IC from overvoltage.

It might be fine with ~27V, but that's really pushing it's limits. Not sure who would be willing to test that out on a $500 amp. Just trying to give fair warning.

Sorry, didn't mean to offend you by calling it overpriced. The product is based around a $4 amplifier IC and the manufacturers decsription of the unit comes off as pure hyperbole.... that's a real turn off to me. This is all OT though so I'll shut up now.
Click to expand...


I don’t mean to come across harshly, but one should not pass judgment on Sonics of a given product unless one has actually heard the product. The copy on the amp operating principals may sound like hyperbole, but in this case, the sonic results speak for themselves. The preamp on the TBI is an impedance matching setup, and it works very well. I don’t want to offend anyone’s setup, but this TBI sounded better than most low wattage big ticket amps I’ve heard. Had I not listened to it myself, I may have otherwise agreed with you.


I had the amp in house for two weeks on loan, and the SLA batteries were two 5AH wired in series. And it works flawlessly. I would recommend getting a 10 to 12 AH setup to get more longevity out of the PS. With speakers that were 88 db/w at 8 ohms nominal, I only got about 6 to eight hours before a charge was required.
 
#9
The chap that makes the amp sent me some more details that he wanted me to post up to explain a bit more about the amps protection features:-

the Millenia is equipped with an electronic crowbar that will blow virtually any sized fuse (short supply to ground) even one that might melt the trace on the board and protect the chip. Tom on the forum expressed his experience when he triggered this by supplying over 27V on the amp. It blew the fuse. It typically takes >27.5 volts to crowbar. The chip maximum is 30V operating. The on board capacitance coupled with the extremely fast crowbar prevent a voltage rise from ever being seen on the main board.

The electronic crowbar will occur when the over voltage is applied to the amp before voltage is supplied to the amp circuitry by the power switch. It wouldn't matter as the fuse will still protect even if it is in the on position.

He also went on to answer some of my questions regarding the Ampage specs of batteries:-

The difference is how long the battery can supply the required amperage. The aH is amp-hours and the more amps used the less time you have. The power supply is rated at a continuous rating with no time limit. 2A, 5A etc. You always want to use a regulated AC power supply for sound quality purposes and to prevent the fuse from blowing. Most inexpensive linear power supplies are not regulated but can be used if their unloaded voltage remains below 27.5V. You also should monitor the battery voltage with an inexpensive voltmeter (dedicated) so you will always know what it is especially immediately after charger is removed.
 
#10
However, I didn't really wanted this thread to be about the amp itself, I just wanted some help building the battery pack, and a sanity check on the components I've selected. Have I been dumb and missed the obvious how to build your own battery pack thread on here? I'm struggling to find a uk components site too so it looks like I'll be forced to use fleabay.
 
#11
gilesw said:
However, I didn't really wanted this thread to be about the amp itself, I just wanted some help building the battery pack, and a sanity check on the components I've selected. Have I been dumb and missed the obvious how to build your own battery pack thread on here? I'm struggling to find a uk components site too so it looks like I'll be forced to use fleabay.
Click to expand...


Thanks for the additional information on the amp.

I would think any good quality SLA setup would work correctly. The one that was sent to me on loan was made by Gary Dodd of Dodd Audio. He put a fuse in line with the harness as additional protection.

If you send me a PM, I can send you some links of examples as to what would work. The links are all US based, but will give you a good idea. Most scooter parts stores have batteries that will work, and some have the necessary wiring.
 
#14
#16
I wonder why all these expensive hi-fi specific battery systems use LiFePO4 batteries, is it a size thing? Presumably unlike car batteries scooter batteries are designed to fully discharge and then charge up again so why don't hi-fi systems use lead acid?

Anyway I found one of these which I can use to see what the output is, it would be interesting to see what it is while the charger is connected:-

New Mini Blue LED Digital Volt Meter Voltmeter Panel DC 4.5~30V UK Post | eBay
 
#18
This will allow both the charger and the output to be connected at the same time.

OEM-T inline Powerpole splitter [BY-T] - $14.99

I wonder what I can to stop the charger from running while the tbi is plugged in. I could put a flick switch in the circuit, or could I use a transistor on the circuit powering the amp to shutoff the charger circuit automatically?

The chargers appear to detect when the battery is full but that wouldn't stop me from switching it on while it was still charging, any ideas?

g.
 
#19
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