Myrtle gets a split personality

myrtleGot bored with Myrtle running out of electricity while entertaining the Damage lot with tunes at shows so decided to fit a split charge system. Started by investigating what was needed and came to the conclusion that I needed a lot of 25mm2 cable, fuses and a relay. What I didn’t know is what relay would I need? I know the alternator pumps out 55amps but would I really need a relay to cope with all that? The trusty threads on VZI had a range of people fitting all kinds of ratings so I had no definitive answer there.

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Underseat area cleared

I then decided to actually ask someone who worked in the automotive electrical industry. This was a good move. I had previously used Altec Automotive to procure a few bits and bobs so decided to email them as they had a few custom built split charge relay systems listed on their website. First thing they asked was what would the nominal power consumption of the audio sytem be? Well I don’t really have the foggiest so grabbed the manuals for the amplifiers to try and find out. Didn’t really have much luck so sent the details over to Jonathan at Altec who informed me that I was looking at a 70amp draw, but as the altenator only chucks out 55, that’s all I would need. Typically, no off the shelf system they had would suit my needs.

I was wondering if the guys running smaller amp relays were replacing them frequently or just had very small amplifiers, so asked the question:

“Do I REALLY need that much capacity? Surely when the amplifiers are on, no charge will cross the relay anyway?”

Jonathan replied

“If you run the auxiliary battery down to zero, and you were to start the car to charge it back up while continuing to run the stereo, you will draw all the power from the starter battery across the relay” (paraphrased)

Ahhhhh. I see. Quite a specific scenario I thought. But then realised jumping in the car after a show with an empty aux battery and driving home you are

Antares unit

Antares unit

likely to want some tunes on. So, where do I go from here? As it happened Altec came through for me and had a few second hand Antares units going cheap at £55 + VAT. Rated at 140amps this puppy would future-proof the system for quite a while .As the JL Audi

o subwoofer amplifier states a minimum of 4awg(!) cabling, I decided to use 25mm2 cable throughout the build to keep costs down of terminals and fuse holders. A decent amount of cash exchanged hands and the build could begin.

Revised placement for the Antares

Revised placement for the Antares

We already had a 4 channel amplifier fitted under the passenger seat that powered two 6″ x 9″ Kenwood 3 way speakers and the other two channels were bridged to power a 10″ JL Audio subwoofer. All speakers are fitted in a  custom 18mm MDF compartmentalised box with the subwoofer compartment ported. As I was using heavier cable for the new subwoofer monoblock, I decided to move the 4 channel amplifier to under the driver seat so the cable run from the auxiliary battery to the new amplifier would be shorter. (As is stands now, I am thinking about running heavier cable for the 4 channel amplifier so that was a bit of a waste of time, but hey ho). Upon finding the existing MDF mounting to be a bit soggy, we forgoe using bolts to fix the wooden battons to the floor. The existing holes got welded up and gripfill was substituted as the fixing mechanism. No more leaky floor for me. One word of advice if you do use this way, make sure you stick the battons to the actual metal car floor, not the rubbery sound deadening crap that I had.

Amplifier mounting battons

Amplifier mounting battons

Next work turned to making up the cables. Again, lots of googling as to the best way to make up what essentially are battery cables. There were basically 3 ways of doing it,

  • Solder
  • Crimp
  • Solder and crimp

After reading stories of solder melting in the terminal and the cable plopping out, I decided again the ask Altec. The answer was a simple “If you have access to crimpers, use them as it’s simpler and cleaner”. Luckily I have a Magic Mike, and he works somewhere that have a need for big crimpers so I called in a favour. Mike promptly turned up with a massive set of new hydraulic crimpers that he had never used before. And couldn’t use. And even if he could use them, we didn’t have the correct dies. Legend.

It was a bit of a stroke of luck really as the terminals that came with the fuse holders were a bit odd and wouldn’t have really worked in either Mike’s crimper of the one I eventually bought from Altec along with another bag of normal terminals to replace the “odd” fuse holder items.

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Making the cables up

Making the cables up

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Brilliant crimpers

Brilliant crimpers

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Fuse holder internals (M8 bolts!)

Fuse holder internals (M8 bolts!)

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The Antares unit was going to be fitted next to the starter battery but space was starting to get a bit tight so I moved it up and mounted it to the speaker box behind the rear seat. Annoyingly I decided to do this after I had cut the cable lengths and luckily another mate happened to have a long length of 4AWG left over from a previous build. Next, I connected everything up and tested the Antares box to make sure it was charging when the car was running and disconnected from the main system when not.

Order of connections were:

  1. Starter battery positive terminal to 60 amp fuse.

    Testing the Antares

    Testing the Antares

  2. Fuse to “Main” terminal on Antares.
  3. “Aux” terminal on Antares to 60 amp fuse.
  4. Fuse to leisure battery positive terminal.
  5. Blue wire from Antares to any earth.
  6. Connect both negative battery terminals to the car body ensuring a good contact.

Using a multimeter, I tested connectivity between the two positive terminals of the batteries. Nothing. Good. Started the car and then tested the voltage going to the leisure battery. 13.8V. Fabulous. Finally the amplifiers got fitted, wired up and tested.

Final Fitting

Final Fitting

Next on the list will be tidying up a few terminals that didn’t get heat shrink and also fitting two battery trays with clamps.

As always, Thanks to Mark for the help 🙂

 

 

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