Dual battery problem

[TURBOMQ]

Ey guys, i've got a mq patrol 24 volt diesel, eveything was fine untill a few weeks ago when i noticed my aux battery was going flat and i jump started it and took it to work and recharged it, next couple of days i lost charge again, i have some 12 volt stuff hooked onto the second battery but nothing major just cd player and a few guages, could a dual battery system help like one from redarc or arb help equalise the charge because the main bettery is getting fully charged just not aux battery?
any help would be great
thanks

[chimpboy]

Hi mate, if you have a 24V MQ then that is not really a dual-battery system the way people normally mean it.

A 24V system is not a main battery plus an aux battery, it is just two main batteries that act as one. This means that if you keep taking 12V power off one battery you'll keep killing batteries.

imho the best option is a device like this: http://jaycar.com.au/productView.asp?ID=MP3063

... which lets you power your 12V accessories from both batteries at once, up to 20 amps. Also comes in 10A (cheaper) or 40A (more expensive).

The other thing people sometimes try is equalising the drain across the two batteries by running some 12V stuff off one, and some 12V stuff off the other. But I would rather just make a good solid 12V supply. ANother option is a third battery and second alternator to make a separate 12V system. Or convert the truck to 12V. Both are a lot of work but have been done.

[macca81]

i agree with the monkey! i had an 24-12v inverter in my mq and i never had probs with batteries.

[TURBOMQ]

ok looks like i should run a inverter then thanks for the help boys, also i have wanted to run a amp but dont know if the converter can handle it, how cani work it out?
thanks
benny

[chimpboy]

Jaycar are pretty good and will probably advise you on how many amps your gear needs.

The 40A unit is $159 or something and this will be enough for a small to medium amplifier, a really big one will probably draw too much power though, and then you'd be looking at a 12V alternator plus a third battery imho.

You need to look at the current draw for each item, a shortcut might be to see what fuses the amp and head unit have, if eg you have a 25A fuse in the amp then that will be a guide for the maximum current it will draw, same if the head unit has a 10A fuse or whatever.

[stuee]

You need to look at the current draw for each item, a shortcut might be to see what fuses the amp and head unit have, if eg you have a 25A fuse in the amp then that will be a guide for the maximum current it will draw, same if the head unit has a 10A fuse or whatever.

That's good thinking. I could also see one of those large capacitors coming in handy with a converter. Would help keep a nice smooth power supply to the amp if the converter gets a bit noisy for whatever reason.

[TURBOMQ]

yeh the amp is a kicker but its nothing major just a 600 watt but i think it draws around 25 amps max and headunit would be only about 5 or 10 so i should be safe with the 40 amp converter

[TURBOMQ]

just had a look my amp has a 40 amp fuse Lol

[stuee]

You'll find when you turn the stereo up very loud there will be spikes in power used when the amps trying to drive your bigger bass speakers (6x9's or subs). This is where the capacitor can come in handy to supply the added bit of power for those short spikes. In saying that, if the fuse is 40 amps then I doubt the 40amp converter will be enough for everything.

You don't want to be left short changed with the amount of power you need or you stereo may sound crap and you might get problems with your other electrics not working as they should. Or you might blow an internal fuse in the converter and be left without power.

It may be possible to use a couple of converters if your short on power though. Say a 40 amp one dedicated to the amp with another one running the head unit and gauges etc. I don't see a problem with this provided they are able to use a common ground. If not you might find it difficult to isolate the grounds of the bits and pieces your wiring up while the head unit may need a common ground with the amp for good quality signal transfer.

[-Scott-]

It may be possible to use a couple of converters if your short on power though. Say a 40 amp one dedicated to the amp with another one running the head unit and gauges etc. I don't see a problem with this provided they are able to use a common ground. If not you might find it difficult to isolate the grounds of the bits and pieces your wiring up while the head unit may need a common ground with the amp for good quality signal transfer.

Start with one 40A converter, and a decent capacitor for your amp. Chances are high that the "600W" amp is PMPO (peak music power output) - so average power consumption will be significantly less, and a decent capacitor will not only "smooth" the peak current demands, but probably improve sound quality whether you're using a converter or a battery.

[TURBOMQ]

do i run the cap off the converter aswell or no?

[-Scott-]

do i run the cap off the converter aswell or no?

Yes. As close to the amp as you can connect it.

When your amp is trying to create the big thumps of a decent bass line it needs bucket loads of current. When it tries to draw this current from the battery (typically at the other end of vehicle) the voltage drop on the supply cables means the voltage at the amp drops, just when it needs it most.

When you place a large capacitor on the amplifier's voltage input, the big thumps can draw power out of the capacitor, which re-charges between thumps. This means the amplifier has a more consistent voltage supply, and is better able to reproduce the music.

Note that if you attempt to enjoy these better thumps while camped within earshot of others, the last thump from your music may be that of a shotgun.

[chimpboy]

At this point it is probably worth asking what sort of power your alternator is capable of. It's not easy to put a beefier alternator in, in your case.

[TURBOMQ]

do i run the cap off the converter aswell or no?

Yes. As close to the amp as you can connect it.

When your amp is trying to create the big thumps of a decent bass line it needs bucket loads of current. When it tries to draw this current from the battery (typically at the other end of vehicle) the voltage drop on the supply cables means the voltage at the amp drops, just when it needs it most.

When you place a large capacitor on the amplifier's voltage input, the big thumps can draw power out of the capacitor, which re-charges between thumps. This means the amplifier has a more consistent voltage supply, and is better able to reproduce the music.

Note that if you attempt to enjoy these better thumps while camped within earshot of others, the last thump from your music may be that of a shotgun.

Lol thanks for the help scott, also i have got a 1 fared aeropro cap will that do the job mate?
cheers

[-Scott-]

Lol thanks for the help scott, also i have got a 1 fared aeropro cap will that do the job mate?
cheers

1 Farad is farkin' huge capacitance. If it's designed for car audio applications, I think it would be a perfect place to start.

Let us know what happens - right down to the make and model of shotgun.

[stuee]

http://www.jaycar.com.au/productView.as ... BCATID=595

http://www.jaycar.com.au/productView.as ... BCATID=595

These are the 1 and 2 Farad capacitors from jaycar designed for car audio. I'm tempted to get one in the back of mine near the amp just for the bling fac... ahh I mean voltage read out...

[TURBOMQ]

Lol thanks for the help scott, also i have got a 1 fared aeropro cap will that do the job mate?
cheers

1 Farad is farkin' huge capacitance. If it's designed for car audio applications, I think it would be a perfect place to start.

Let us know what happens - right down to the make and model of shotgun.

Haha yeh i will let everyone know what happens, the two kicker 12inch's wil cause some mayem Lol

[chimpboy]

As the costs start to look higher, I am just wondering if you should look at a separate 12V alternator and battery. It's a bit of work but not that bad.

[TURBOMQ]

when i install the cap will the 40amp converter be ok to run the amp i mentioned before and cap ??

[stuee]

when i install the cap will the 40amp converter be ok to run the amp i mentioned before and cap ??

A cap wont draw power like the amp. It acts like a reservoir. When you power up the converter the capacitor "fills up" (so yes briefly at the start it will take a bit of power away). Once the capacitor is full you don't even notice its there. Then when your amp draws more power than the converter can put out (like a heavy bass beat), the capacitor empties enough of its "reserves" to power the amplifier. When the amplifier is not drawing all of the power from the converter the capacitor fills back up again.

I'll try and find a better explanation on the web for you of how it works but thats as best as I can explain it this early in the morning.

edit* heres a good one off How Stuff Works:

Like a Water Tower
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way and can then release them later.

[TURBOMQ]

yeh i just wasant sure if the cap would draw any amps from the converter, anyone know if i can get a converter cheaper than jaycar?

[TURBOMQ]

will the ground on the cap be ok to run to the same ground as the amp ?

[-Scott-]

A cap wont draw power like the amp. It acts like a reservoir. When you power up the converter the capacitor "fills up" (so yes briefly at the start it will take a bit of power away). Once the capacitor is full you don't even notice its there. Then when your amp draws more power than the converter can put out (like a heavy bass beat), the capacitor empties enough of its "reserves" to power the amplifier. When the amplifier is not drawing all of the power from the converter the capacitor fills back up again.

I'll try and find a better explanation on the web for you of how it works but thats as best as I can explain it this early in the morning.

edit* heres a good one off How Stuff Works:

Like a Water Tower
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way and can then release them later.

I don't know stuee - I reckon your explanation was better than How Stuff Works.

will the ground on the cap be ok to run to the same ground as the amp ?

That's how I would do it - as close to the amp input as you can, with wire as thick as you can.

[TURBOMQ]

ok thanks heaps for the help boys, will let u know how i go

is there any converters out there that can handle more than 40 amp???

[chimpboy]

What sort of alternator are you running mate? Does it have more than 20A to spare? Because you aren't getting those 40A for nothing, even with the converter.

[-Scott-]

What sort of alternator are you running mate? Does it have more than 20A to spare? Because you aren't getting those 40A for nothing, even with the converter.

Doh! Good point. Here I was getting carried away with all this talk about a capacitor, forgetting it's not a flux capacitor.

[murcod]

Just be careful with those big capacitors- it will draw a large in rush current when first powered up. I'm not sure how happy the convertor would be in that situation?

I guess there's only one way to find out!

(A capacitor will basically act like a short circuit when first connected to power. The current draw will drop off as it charges up.)

[TURBOMQ]

What sort of alternator are you running mate? Does it have more than 20A to spare? Because you aren't getting those 40A for nothing, even with the converter.

Sorry mate what do u mean?

[chimpboy]

What sort of alternator are you running mate? Does it have more than 20A to spare? Because you aren't getting those 40A for nothing, even with the converter.

Sorry mate what do u mean?

Sorry. I mean that if you need more than 40A for your 12V gear, then you will be stealing something like 25A from your alternator's output. (Roughly half the amps because you are halving the voltage, but then only about 85% efficiency).

Now a standard MQ 24V alternator is only a 35A @ 24V device I think. So really, you are taking more than two thirds of your alternator's output and pumping it into your stereo gear. You are only leaving 10A or so of your alternator's output to keep doing its main job that it is designed to have 35A for.

This might be okay but it might not.

What I am thinking is that instead of spending, say, $300ish for a 60A convertor, you might be getting to a point where it is better to buy an 85A 12V alternator from pick-a-part, make a simple bracket, and mount it to your motor. Ultimately it is going to provide more power than you could possibly ever need.

I tend to think that if you are looking at more than 20A you might be better off doing a separate 12V alternator, and if you are looking at more than 40A you almost definitely should go the separate alternator. Then you can mount a good sealed battery near your amp(s) and have the kind of sound system it sounds like you want. And you will be set for 12V devices like spotties, winches, etc, anything else you might want down the track.

When I suggested the DC-DC converter I was thinking more along the lines of more basic 12V stuff drawing 20 amps or less.

If you didn't have a diesel it might be better to just upgrade your existing alternator but diesels are a bitch to upgrade, due to the vacuum pump.

[TURBOMQ]

thanks for the help mate, yeh i am thinking it mite be worth just running a seperate battery and alt. with the bracket is there someone on the forum that has done a 2nd alt on a mq???? or someone that may have a idea of doing this? and how and where do i run the belt for the 2nd alt?
cheers