Batteries and alternators

[VR457]

After having to replace both recently i thought it would be useful to share some info for members potential benefit. Corrections may be necessary ...

Basically, there are three types of batteries: Wet cell, Gel and AGM. The wet cell batteries do not like being used for equipment that require heavy current, such as bass systems, winter weather conditions etc. They take time to recharge and if heavily used, die quicker. They also require maintenance.

AGM's on the other hand do not require maintenance, can give out loads of current on demand and charge back up fast. They can be discharged 50% or more hundreds of times and still come back for more. They can be left disconnected for long periods of time and lose very little power.

So, a no brainer then? Well.....according to this site http://www.bitwrangler.com/wt/lv-ab-agm.html an AGM can kill an alternator if it's regulator is weak or everything on it is not tip top. Also, an AGM does not last as long as a gel or wet battery. It does not like to operate under lots of heat either. Also charging it back up seems to be a pain.

Gel batteries are a sort of compromise with the newer ones requiring virtually no maintenance, really good pricing and shed loads of cranking current (starting).

Regarding battery makes i found that Lucas, Varta and Numax are one and the same. Check the power outputs, battery sizes and terminal design and you can see for yourself. I purchased a Numax 096AGM and got a Lucas 096AGM from the company! Why AGM? Because for the current i will need, that is 120A, (1500w / 12.4v) only an AGM can keep up with the demand.

So, avoid problems with your alternator by checking your batteries every once in a while. Leave the battery disconnected for 12 hours or run the headlights for 2 minutes first. Use a dc voltmeter which you can get for about £5 from Maplins and check your voltages:

12.65 - battery is 100% charged
12.45 - battery is 75%, limit for normal wet batteries
12.24 - battery is 50%, limit for deep cycle batteries
12.06 - battery is 25% only and damaged
11.89 - battery is less than 5% - it's discharged and dead

I had an Optima yellow top for a total of 9 years and should have replaced it about 4 years ago. So instead i duffed the alternator with it and had to replace the alternator and the battery at the same time.

[foxdie]

Hmm, interesting read, I just bought an AGM battery and it's pretty damn good, but I didn't realise it'd rape an alternator.

Anyone able to advise how good / poor the alternator is on cold and warm spec 8Gs?

[VR457]

It's not the alternator as such but rather if the AGM is in poor condition i would have thought. I had a 4 gauge wire running from the alt + to battery + for a year and eventually as the AGM was dying the alternator started screaming and giving out lots of smoke. Took the wire off, all was quiet, but no charge to the battery, minimal lighting on the dash and general bad news.

This would not have happened in the Saab! It had an electronic voltmeter on the dash!

[foxdie]

Hi Jamil,

Resurrecting an old thread here for more information, I'm going to ask Nick to fit a cold spec 120A alternator, looking at this guide (http://www.powerstream.com/Wire_Size.htm) it seems the safest way to "route" that 120A to the battery is via 0 AWG or 1 AWG cable, as the latter isn't all that easy to get hold of we're left with 0 AWG but I remember you saying it being quite difficult to attach it to the alternator.

What do you think the best way to get all that current back to the battery will be?

[HMG1K]

Just seen this thread - I've had an AGM battery fitted for over two years now, running amp, headunit, bass tube - no hassles at all with the starting performance or power. :-)

[foxdie]

Just seen this thread - I've had an AGM battery fitted for over two years now, running amp, headunit, bass tube - no hassles at all with the starting performance or power. :-)

You've clearly got a healthy Alternator / Regulator then :)

[VR457]

Hi Jason. The problem was in fitting the lug onto the alternator. Here is an example of a lug - http://shop.ebay.co.uk/i.html?_nkw=4+gauge+lug&_armrs=1&_from=&_ipg=.

Nick should be able to recall the problem we had. Basically you have to fit the lug on to the alternator prior to moving it into its holding position. After that it doesnt really matter how you route the wire to the battery. In theory you should be able to trim the ends of a 0 gauge wire, fit a 4 gauge lug onto it and then fix it to the alt.

By the way don't forget the other two factors of TB3; battery to ground and alt ground to chassis. I grounded the battery in several places on the car as per Ralliart style. Re alt to chassis, that remains unresolved but i will have to find out where that is.

[foxdie]

Hi again :)

Was it a case of not being able to get a lug for 0AWG cable? Or wouldn't it fit?

I'm planning on using 2AWG cable throughout now, would something like this (http://cgi.ebay.co.uk/Amplifier-amp-wiring-ring-terminals-1-red-1-black-2AWG-/150560965553?pt=UK_Cars_Parts_Vehicles_Terminals_C abling_ET&hash=item230e2203b1#ht_573wt_907) fit?

My plan was to run both positive and negative 2AWG cable from boot to fusebox in the engine bay, periodically cutting into the ground wire along it's trip and tapping it to the chassis like the following photo (only picture I could find, naturally it won't be corroded!)

43729

Also, how does the alternator connect to ground? There's only 1 lug on the alternator, I presumed that to be positive, are the 4 or so mini spade connectors the ground?

[VR457]

You can get 0 gauge lugs, it won't fit on though....Again, fit the 4 gauge lug on and fit the 2 gauge wire onto the lug.

I don't know why you want to run cabling from boot to fusebox but ideally you need a single grounding point for the negative wire, not multiple ones.

Re alt to chassis ground, on the Saab 9000 it was a single 4-8 wire. It ran from the engine block to the coilspring mount (strut brace point). I don't know where it is for the VR4. Maybe the multiple grounds i have done back to the battery negative is just that and the battery grounds back to the chassis?

Anyway, whatever i did must have worked because with driving around and subs maxxed out using 1500 RMS, plus the 3-400 wrms of the midrange plus headlights, the voltage only fluctuated between 13.6-13.9v.

[foxdie]

Sorry Jamil, I don't wanna seem like a retard, the lug itself won't go over the thread/post on the alternator +VE output? Or won't fit around the vicinity of the engine bay?

I was thinking multiple grounding points along the length of the run to hopefully give better ground connections and more reliable / clean power flow.

I was also thinking of fitting a grounding kit in the engine bay to ground various parts of the engine to various parts of the chassis.

[VR457]

It's ok, it's always better to be clear. Afai can remember, 0 gauge lug will end up sitting on top of the plastic recess where the alt positive wire fits it and so won't fit. So, you have to position the 4 gauge lug onto the protruding bolt, put the lug on and then the normal alt + wire. The thicker gauge of the wire can't help because it seemed an effort (for Nick) to manoevure the whole alt back into position even with the 4 gauge.

Re multiple grounds i still think its best to avoid and go for a single, fat ground. I used the position under the rear back seat where the boot joins.

[VR457]

437444374543746

Best view i can get with the camera. It appears that the alt + wire went on first, then the 4 gauge wire, then a retaining nut on top.

Nevertheless you can see how tight it looks down there.

[foxdie]

Jeez, Nicks gonna have fun with mine then :)

Is it possible to just replace the alternator wire as a whole instead of augmenting it with 4 AWG?

[VR457]

Good luck doing that. I wouldn't know where to begin! I suppose you could figure it with the engine out where the wiring goes and links up.