Overcoming Voltage Drop

[Paul2131]

Hi,

I hope someone can clear this up.

I have wired my Waeco direct to my dual battery using a cigarate socket with a 15 amp fuse in between using 26/0.25mm Cable.

My compressor will now not fire up but when move the battery closer it will or when I start the engine it will. So I gather (From a long time ago in some school lesson) I have a voltage drop issue due to the distance to the battery and the size of the wire.

What is the ideal wire size to overcome this? and should i be using an anderson plug.

The distance from my Waeco (40L) to the battery is 4.1meters.

I hope someone can help here as I have had a good look in the search engine and cant find much.

Thanks for any help that may come

[chimpboy]

There's no simple answer to what is the ideal wire size, but I would be looking at something like this:

http://www.jaycar.com.au/productView.asp?ID=WH3060

It's still cheap and easy to run, and it should handle your fridge's current requirements without even trying.

Alternatively, run an even bigger cable and have it ready in case you want to run other things as well later.

Jason

[dirtyGQ]

cut that cigarette lighter plug off and put a good quality merit style plug and socket . Secondly run 2 minimum 4mm wires with a continuous 25 amp rating (available from jaycar) and thirdly have your battery checked at a battery shop ,and contrary to belief your alternator will only charge your battery to 70% capacity so pays to charge off a 240 volt charger once a month. I have just been through all that myself and can be super frustrating but now works a treat get 3 days out of my 60ltr eva cool before recharging.

[drivesafe]

Hi Paul, as chimpboy posted, go for thicker wire.

What you have there is about 1.5mm2, which is way WAY too small.

You need at least 6mm auto cable ( about 4.5mm2 ) and relatively cheap in twin sheathed form or if you don’t mind the cost, do as chimpboy suggested and go for the 8g ( 8B&S ) cable and you will have very little voltage drop which will mean your fridge won’t have to work as hard.

Cheers

[DamTriton]

http://www.outerlimits4x4.com/PHP_Modul ... hp?t=85746

Pretty well covered here

[-Scott-]

...and contrary to belief your alternator will only charge your battery to 70% capacity...

I've seen this claim made a few times now, but I've yet to find an adequate explanation for WHY this is so.

So, until somebody can provide a link to a reasonably scientific explanation to back up this claim, I'll say it's wrong - and here's why.

An automotive charging system is a relatively simple system, designed primarily to "top up" the battery after a couple of seconds of cranking. Being a simple system, the charge current is effectively regulated by the level of charge in the battery - the higher the charge in the battery, the lower the charge rate. So, if you deeply discharge your battery every day, then drive for only 5 or 6 hours to recharge it, I can accept that you will struggle to charge your battery to much more than 70% each day - because that last 30% will be at a low rate, and take a long time.

But, when you get back from your trip, switch off/remove the fridge and return your 4by to regular commuting duties your second battery will be fully recharged within a few days.

And, while I'm at it, just because you CAN run your fridge for three days before recharging, it doesn't mean you SHOULD do it. The deeper you discharge ANY lead acid battery, the more you shorten its life. If you want to sit for days on end without driving your car, buy a Chescold and run it on gas.

Scott

[Paul2131]

Thanks Guys

At least after a trip to Jayco I will be able to have a cold beer after a long drive as my fridge will be working.

Thanks again for all your help and advice

Very much appreciated

Paul

[dirtyGQ]

No i don"t sit for days without running car just an example, btw i have been told by 3 battery suppliers you must charge with deep cycle once a month. That is what i will be doing from now on.

[drivesafe]

...and contrary to belief your alternator will only charge your battery to 70% capacity...

I've seen this claim made a few times now, but I've yet to find an adequate explanation for WHY this is so.

So, until somebody can provide a link to a reasonably scientific explanation to back up this claim, I'll say it's wrong - and here's why.

An automotive charging system is a relatively simple system, designed primarily to "top up" the battery after a couple of seconds of cranking. Being a simple system, the charge current is effectively regulated by the level of charge in the battery - the higher the charge in the battery, the lower the charge rate. So, if you deeply discharge your battery every day, then drive for only 5 or 6 hours to recharge it, I can accept that you will struggle to charge your battery to much more than 70% each day - because that last 30% will be at a low rate, and take a long time.

But, when you get back from your trip, switch off/remove the fridge and return your 4by to regular commuting duties your second battery will be fully recharged within a few days.

And, while I'm at it, just because you CAN run your fridge for three days before recharging, it doesn't mean you SHOULD do it. The deeper you discharge ANY lead acid battery, the more you shorten its life. If you want to sit for days on end without driving your car, buy a Chescold and run it on gas.

Scott

Hi Scott, it’s so nice to hear someone else question the crap about not being able to charge your battery above 70% off the alternator.

Try this site and read the “ MYTH “ about not fully charging a battery and more importantly WHY.

http://www.uuhome.de/william.darden/car ... m#recharge

You hit the nail on the head by pointing out that we, as 4x4 users, are NOT doing the shopping trolly trips that may well mean that the battery will not be fully charged.

We usually drive for at least a few hours and this will, even with slower charging wet cell batteries, get the bulk of the charge back into the battery and with your suggestion of driving for 5 hours. Even starting out with a battery at say 20% SoC, after 5 hours, I would bet your battery(s) would be closer to 85% SoC.

Cheers and good to see some people do use common sense.

[Paul2131]

Thanks Guys

Did what you said and got some bigger wire and an anderson plug and it runs a treat

Cheers