Battery thoughts. (1 Viewer)

[Dave 2000]

Hi all, those 'sparkies' amongst you please have a glance at the four diagrams below if you would. They relate to my dual battery setup. I have run diagram #1 for the last four and a half years I guess when I converted 24v starting to 12 volt, so I know it works with some minor irritations, poor lighting for the first couple of minutes until the VSR kicks in, obviously the aux battery also takes longer to come to full charge as it is the one that is exposed to the longest period of drain, so I am now in the process of refining everything, fitting the correct starter (as opposed to my custom 3.0 kw unit), reducing cable runs and generally tidying the whole affair up. The cables running from the battery and alternator presently run under the radiator being protected by the main cross member in the event of a shunt. I am now planning to run under the slam panel where the bonnet lock runs, this will provide a shorter run, but assume all fuses are where they are supposed to be.

A quick run down to offer some extra information which may or may not colour your thoughts. The aux battery is the one being pulled on by parasitic drain i.e. clock, alarm, and when camping fridge but this is minimal and only at night as there is a solar panel that covers the fridge draw during the day, the fusible links are still in use from there as well. The aux battery is now struggling to maintain it's voltage and to be fair has done it's job, and the real reason to consider replacing the pair in the very near future. The starter battery apart from the short period of time it is paralleled with the aux does see the parasitic draw until the VSR splits them, other than that, it is for the starter use only. I chose to keep the left battery for the starter to keep voltage drop down, and run the alternator to it for the same reason i.e. prioritise starting/charging to that supply.

I had been studying other ideas/diagrams for the refinement process, and one that caught my eye was the idea of NOT relying on the chassis for earth across the batteries as in diagram #2 i.e. run another negative cable to each negative battery terminal, if this is going to reduce voltage drop then connecting the alternator to the auxiliary battery should yield less voltage drop to the auxiliary hopefully extending it's working life, and still offer the minimum voltage drop to the starter battery, I am following the standard rule 3% or less for voltage drop as I have done for all my vehicle electrical projects.

I see all four working and I am planning on the rewire to follow #3 as it seems to be the most logical but, an alternative is #4, in this diagram I have transferred over the 3 fusible links to the starter battery, this does mean additional wiring work but as they are starting to look a bit tatty and were being replaced anyway I thought now would be the most opportune moment, I cannot see a strong enough argument to do the move though.

#1

#2

#3

#4

Your constructive critique would be appreciated.

Many thanks,

regards

Dave

 

[Dave 2000]

Giving this a bump as there was 70 plus views buy no sparkies on MUD over the weekend. As per the text just looking for other peoples thoughts, you know in case I am having a blonde moment.

regards

Dave

 

[sbman]

#4 looks best to me, drawing the vehicle systems power off of the same circuit as the starter is the safest. A fully charged battery that can run the starter but not power the EFI, Fuel Pump, etc... doesn't seem especially helpful.

The batteries should be grounded from each battery to the same point on the chassis/block, with all of the OEM ground strap(s) running from frame to block, the same as the OEM configuration. Grounding each battery at a different point opens the possibility of ground potentials being different for each battery, especially with a high load device (starter) on one of them. A bridging connection as shown still has losses that can contribute to ground oddities. Although the grounding of the batteries as shown should work fine, I thought your original grounding scheme was better.

I'm not familiar with your VSR device, so I can't offer any help there.

 

[Douglas S]

I have mine setup as #3.

Alt supplies power directly to the aux battery (important for me as this is the battery my winch is attached to). One battery dedicated for the starter reducing the changes of having to self-jump due to a draw, which can be hard on batteries.

 

[Dave 2000]

Hi and thanks for the input.

@sbman. Being diesel I do not have the draw of the fuel pump/EFI but do have the substantially higher draw for glow plugs, this was why I thought the starter battery would see this high load before the starter was engaged. I see it would make fault finding easier having the fusible links on the same battery as per stock but would also expose the starter to parasitic loads from the stock clock etc. I see your point about the earths, I though earthing from starter battery thru the aux to the chassis would be sufficient? Your comments about earths makes me think that an additional earth from the aux to the block mirroring the starter battery to block earth could be useful, if the present starter/battery earth (in ALL my diagrams) went bad I would lose both starter AND alternator performance, good call.

@Douglas S. # 3 my preferred option as well, at the moment I have no winch but would like to think there will be one in the future, with the recent availability of high amperage alternators at a sensible prices with outputs off 300 + amps means that putting a decent cable between the alternator and aux battery now means a simple bolt in of one of these high powered beasts would be a walk in the park, my present Sequoia 150 amp unit ok for the moment, I think #3 but with the additional earth mentioned by sbman may make this the winner.

Thanks guys, it will be interesting if anyone else can offer any futher thoughts about improving my wiring diagrams.

regards

Dave

 

[tlin]

I'm no Sparkie but this, given your thread, might be of interest/value to you. GL.....

 

[Dave 2000]

I'm no Sparkie but this, given your thread, might be of interest/value to you. GL.....

Thanks for that, unfortunately the first line 'get a beer' followed by a diagram of no body earths is a bit worrying.

Of note thought that is the very same site that I saw the idea for diagram #3, but definitely not the same author.

Thanks for the thought though,

regards

Dave

 

[Dave 2000]

Finally got rid of the leg cast and will be finalising the 'heavy' wiring (batteries/start/charge) this week.

So to this end I would like opinions on the following diagram. It is about the alternator connection, in an attempt to have just three cables going to the aux battery positive that is battery to VSR, battery to fuse boxes, battery to winch (later). This will keep the battery area nice and tidy.

My first thought was to have the alternator un-fused direct to the battery, this is not as bad as it first sounds assuming the cable is well protected, and years back there was never any fused protection however, this is about making the car wiring tidier and bringing it up to today's standards. The OE alt was fused and removing that would in effect be a backward step against what I am trying to achieve.

So to the diagram,

Blue un-fused to battery, not ideal and is another cable on the terminal which I am trying to avoid. But, and a big BUT, I may run a winch from here and even run a larger alternator, I am in just thinking of future plans, and trying to save a rewire which never looks as good as the original plan. So perhaps #1 is the better option long term?

Purple means the alternator is in essence un-fused with such a large fuse rating, it will also cause some bunching with two heavy cables in the same outlet of fuse box one.

Red is my preference, the alternator has the 150 amp fuse, the cable entry into fuse box two is neat an tidy, it looks too easy but it means in the future, a winch addition means altering the wiring again. As I am using quite heavy cable from the alt now, then the winch addition may not be such a big deal?

Thanks for your thoughts?

EDIT: I am pretty much certain I am going the red 'route'. I will cable the winch from the other main battery, the cables between more than capable of handling the 'pull' between them. If you see anything a bit 'hinkey' then let me know by Saturday

regards

Dave