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dual battery amperage questions.

For all things Electrical.

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dual battery amperage questions.

Post by howsie »

Ok been scouring the net and this site for a few days now amd either the question has not been asked or.i am useless at searching (both just as likely).

With a dual.battery setup what's with the different average kits. My 80 has a 110 amp alternator so would i buy a kit that allows for 110 amp continuous or is it unlikely to pull that much. Also considering this setup will.be running a winch off the.main battery with both batteries joined. Was gonna run 2 dual purpose batteries rated at about 750 cca and 95ah each or would I be better off with a deep cycle 2nd battery as i would rarely need to jump using the second battery of at all.

Was more thinking of the dual purpose as the main reason is for installing would be to run fridge eventually overnight, more power / longer battery life when winching and for running a rather large stereo setup when in the middle of nowhere without having to get the.jumper cables out in the morning.

Basically will.have starting and normal car electric off main including winch, with 0 - 2gauge cable run inside the car to a distribution block to run stereo components and a whole bunch of 12 volt acc sockets for fridges, phones and.misc items
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Re: dual battery amperage questions.

Post by drivesafe »

Hi howsie, for a start, you will need two cranking batteries if you are going to be using the auxiliary battery while winching.

The exception to the rule is something like an Optima Yellow Top Deep Cycle. This battery is also rated as a winching battery, but most deep cycle batteries will have a VERY short life if you use them in any high current situations.

Cabling, if both batteries are under the bonnet, 3B&S ( 25mm2 = about 250 amps ) or 2B&S ( 32mm2 = 275 amps ) would be fine. If you want to run thicker cable go for it but there is actually little gained for the additional cost. Again if you want to use 2B&S ( 39.5mm2 = 300 amps ) or 0B&S ( 50mm2 = 345 amps ) is up to you.

While winching, you will rarely pull 150 amps from your auxiliary or cranking battery unless you are running your winch at near stall.

Normal heavy winching current with your set up could go to 150 amps from your two batteries and probably 70+ amps from your alternator, so you would have about 370 amps to run your winch and this is pretty high, except as above, if you run your winch at near stall.

As for the cable to the fridge and stereo set up, 6B&S ( 13.5mm2 = 95 amps ) would be heaps big enough for what you want and that size would also reduce voltage drop to the fridge and stereo.

NOTE, these are suggested cable sizes.
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Re: dual battery amperage questions.

Post by -Scott- »

Wot he sed. ^

I'm not sure what you mean by "different average kits", but there's a few differences between the kits of which I'm aware.

The most basic system is a solenoid (big relay) that connects the two batteries when the engine is running, but separates them when the engine isn't running. Simple.

Some use a "voltage sensing relay" that monitors the voltage on the main battery, and disconnects the second battery when the main battery voltage drops (indicating the engine is off) and reconnects when the main battery voltage indicates that it is well charged. These systems effectively "prioritise" charging of the main battery (makes sure it has a good charge, but not necessarily 100%) before the aux battery is connected.

Some systems use electronic controls to monitor both the main battery voltage and the aux battery voltage, and can limit the charge rate of an auxiliary "deep cycle" battery, some of which can theoretically be over-charged by a conventional alternator charging system. As best I can tell, modern "deep cycle" batteries (and particularly AGM batteries) aren't particularly bothered by this.

For most recreational campers, the largest current that passes through the isolator would be the charge current. IMHO (and others will differ) I don't believe a "typical" install will allow sufficient charge current through the second battery for the current rating to be much of an issue.

However, in your circumstance, where you want to run the winch using both batteries at once (which runs the risk of flattening both your batteries, and leaving you unable to re-start your motor should it stall) you need to ensure that the isolator is capable of carrying its share of the winch current - which is more than your alternator will produce.

When it comes to winches, I try to steer clear.
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Re: dual battery amperage questions.

Post by drivesafe »

Hi again howsie, and I forgot to cover isolators but Scott has done that in spades.

My apologies for spamming but I have a new isolator that is not on my web site yet but it may be of interest to you.

There is a thread running on the AULRO forum and it has plenty of info and feed back about the new isolator.

If you are interested, the link below gives you all the info about my new isolator, the USI-160 and the info covers most of what you seem to want.

http://www.aulro.com/afvb/verandah/1189 ... lator.html" onclick="window.open(this.href);return false;
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Re: dual battery amperage questions.

Post by -Scott- »

drivesafe wrote:My apologies for spamming
You're not spamming (and you never do). Spamming is normally posting of links that have little (if anything) to do with the forum and/or topic. In this case, your link is both highly relevant to this topic, and of general interest to users of this forum. Your new isolator looks very good.

And it's good to see you here again. :)
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Re: dual battery amperage questions.

Post by drivesafe »

Thanks Scott, and I’m always lurking but I have been busy.

BTW, I offer a special price on the AULRO forum and this is also available to members here.
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Re: dual battery amperage questions.

Post by howsie »

Different average kits is meant to read different amperage kits. The way I was going to do it with a dual purpose battery would be the way to.go.then it seems I have one in the car now and it is a high discharge staryer battery with better than average ah.

Drivesafe will definatly check that link out was looking at the abr sidewinder kits.on eBay rated at 140 and constant with a smart isolator and the ability to link batteries via a push button for emergency starting.
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Re: dual battery amperage questions.

Post by drivesafe »

Hi again howsie, and no worries.

Have a look at the link anyway and just compare the two isolators.
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Re: dual battery amperage questions.

Post by howsie »

Looks like a good setup you've got but I don't want the light for.inside the car just the isolator what can you do these for by themselfes. At the moment with no wiring just isolator and switch I'm looking at 80 bucks for the sidewinder but not sure if I want to get the 160 of yours for.the added power. Both from what ive read connect and disconnect automatically, have manual override for jumping and have surge protection. Was going to hook it up to twin digital volt gauges for readout and a switch for manual linking.

Does yours have a time delay on linking the batteries so the main battery gets charged first or is it set by voltage or both.
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Re: dual battery amperage questions.

Post by drivesafe »

Hi howsie and I’d better correct some of the advertising B/S first.

There is no such thing as DC surge protection. I know a number of DBS sellers state their gear has surge protection but unless you intend to plug the isolator into 240VAC, they can claim to have all the surge protection they want, it doesn't do anything.

Surge protection is only relevant in AC circuits and for sellers to make out their product is better because it has surge protection is nothing short of an adverting con job.

If you do a google for electrical surge protection, all you will find in surge protectors for AC, with a couple of exceptions where there are dual AC/DC devices and again the surge protection is only to protect the device while it’s being used in an AC circuit.

As to the start up delay. The USI-160 has an 8 second delay and this is to allow the vehicles voltage to stabilise before connecting the auxiliary battery(s) to the vehicle’s electrical system.

There is actually nothing to be gained by delaying the connection time because the alternator is the ruling factor, not the state of charge of the cranking battery.

If the alternator is big enough, and 99% are, it will easily charge a number of batteries at the same time so why delay the charging time?

Next, my isolators are made here and come with a 2 year warranty and a life time repair guaranty. Now as most of the Asian made isolators are packed in epoxy, once out of warranty, if the play up, you throw them away, they can not be repaired.

As for the In-Cab module, the USI-160 does not need the In-Cab module to operate, it functions with out the module connect and it automatically runs in SHARED mode.

The In-Cab module allows you to operate in SHARED mode ( only available on my isolators ), in IGNITION mode, which is how all other isolators work.

You also need the In-Cab module to be able to operate the Jump Start feature and to put the isolator into WINCH mode, again the way my isolator operates in WINCH mode varies from any other isolator and gives you and your batteries far greater protection while winching.

Another feature not found on other isolators ( without needing extra wiring ) is the way the LED in the In-Cab module dulls after 60 seconds so it does not distract you while you're driving at night.

There are a number of other battery protection features in the USI-160 that are not found in other units.

Anyway, it’s your choice but one more word of caution, when you see someone advertising that their device has SPIKE protection, again, this is just another advertising con job.

If they didn’t have spike protection, nothing would happen to any of the devices in your vehicle, but THEIR ISOLATOR would be destroyed without out spike protection being built in, just like spike protection is built into every single electronic device ever made. Again it’s a con job.

Howsie, sorry for the long winded reply but I just hate the amount of dishonesty that is being used by a number of isolator sellers as a means of trying to make their gear look better than it really is.
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Re: dual battery amperage questions.

Post by drivesafe »

One more point I forgot to cover.

Howsie, don’t waste your money on voltage gauges, they give as much deceptive info as they give useful info.

If you want more on the subject I am happy to cover it but it will be another long winded post.
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Re: dual battery amperage questions.

Post by stilivn »

i got the sidewinder you are talking about but the previous model, accidently earthed it out an now its phucked. Ps they are $10 chinese imports rebadged
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Re: dual battery amperage questions.

Post by drivesafe »

Hi stillvn, you did not mention when you did the deed but your post reminded me to post up my warranty details.

My gear comes with a 30 day INSTALLER WARRANTY, and it covers accidental damage caused by the installer and if one of my isolators is damaged by the installer, the unit will be repaired or replaced under warranty.

Now I have had this INSTALLER WARRANTY in place for more than 30 years from way back when I started in the auto electrical field, producing car alarms and get this, it was not introduced because DIYers were damaging my gear while installing it.

The INSTALLER WARRANTY was introduced after a suggestion from my biggest customer, an alarm installer, after I told him about all the returns I was getting. All from auto electricians.

The alarm installer was buying up to 400 alarms a month and not a single return yet I was getting a return rate of as much as 1 in 20 from auto electricians.

The problem was not so much the number of returns, it was that the auto electricians always stated that the unit they were fitting just didn’t work or had some mysterious problem.

I would then spend hours trying to find some non existing problem and this is where the alarm installer’s suggestion came into play.

He suggested I give the auto electricians an unconditional warranty that included covering them for their mistakes and it worked a treat.

Instead of trying to make out the unit just mysteriously failed, they would tell me what they had done wrong.

This 30 day warranty had a two fold benefit. The auto electricians kept buying my gear because they knew their own stupidity was covered, plus I would find out how they had damaged the units and progressively designed ways to avoid the problems the auto electricians were causing.

Point is I still have the same warranty and it covers all installations, be it professionally done or be it done by a DIYer.
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Re: dual battery amperage questions.

Post by howsie »

Good to know where do.we purchase your unit from. Is be looking at this after rego around christmas time. You mentioned volt gauges are a bad idea any alternatives out there. Would really love a reading on the state of both batteries
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Re: dual battery amperage questions.

Post by drivesafe »

Hi howsie, the problem with volt meters used to keep track of batteries in a vehicle, once you start your motor, no matter how charged or discharged any of your batteries are, the only voltage you will read is your alternator voltage.

Now add to this that once a battery has received any form of charge, it will now have a surface charge voltage that will be anywhere between the battery’s actual SoC and the voltage of what ever was charging it and the surface voltage can last up to 24+ hours. So again, a voltage meter is not going to be of much use, and you can get a surface voltage on good and stuffed batteries.

And just to make things more difficult, lets say you have a battery in the rear of your vehicle and you what to monitor it to see if it’s charging.

While the motor is running and with a long cable run, you could get say 14v at the cranking battery and 13v at the auxiliary battery.

Problem is, is the voltage drop caused by a problem with your wiring ( which is a bad thing ) or is the battery so low and pulling some much current that it is causing a voltage drop ( which is a good thing ).

Then the opposite can be the case where you have 14v at both batteries. Does this mean your rear battery is full and therefore not causing a voltage drop or does it mean your rear battery is stuffed and not taking a charge and again not causing a voltage drop.

The only time a volt meter is of any realistic use is while you’re camping, when you are running a few things like a fridge and some lights, what ever, you can do a voltage check to see if your battery is still fairly full or if a bit down but you know it’s still got a good few hours of use, or if the voltage is low, you know it’s time to charge your battery.

In this situation, having a volt meter mounted on your dash is actually going to be more inconvenient than useful and a $10 digital multi meter would be far more useful.

You can now get meters that have both a LCD volt meter and an amp meter in the same unit. These are more useful but they are still guesswork as to what is actually going on.

The only way to get a useful indication of whats happening with your batteries is to install a battery monitoring system but these start at around $450 to $500 for a kit and require a fair bit of installing and in my opinion, not really worth the money for most uses.

Again, a $10 digital multi meter and a bit of battery knowledge is a far better way to keep track of your batteries.
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Re: dual battery amperage questions.

Post by -Scott- »

drivesafe wrote:Again, a $10 digital multi meter and a bit of battery knowledge is a far better way to keep track of your batteries.
This.

My voltmeter tells me if my alternator (regulator) is putting out about the right voltage. I check both my batteries with my multimeter to guesstimate if they're properly charged, and I occasionally take some multimeter measurements while the engine is running, to look for voltage drop in the system, which can be an indicator of dodgy contacts and less than optimum charging.
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Re: dual battery amperage questions.

Post by stilivn »

Drivesafe it was done on installation and yeah was my bad, you don't own sidewinder do you? Was over a year ago now so am trying to fix it myself next time I get a chance to drop into jaycar. Point I was trying to make is op is better off spending a few more $ on a quality unit. This is what I will be doing next time.
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Re: dual battery amperage questions.

Post by drivesafe »

stilivn wrote:Point I was trying to make is op is better off spending a few more $ on a quality unit. This is what I will be doing next time.
Hi stillvn, that was actually what I was, in a roundabout way, trying to push.

The price USUALLY reflects the quality and product backup.

As far as knowing Sidewinder products, trust me the less said the better.
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Re: dual battery amperage questions.

Post by stuee »

-Scott- wrote:
drivesafe wrote:Again, a $10 digital multi meter and a bit of battery knowledge is a far better way to keep track of your batteries.
This.

My voltmeter tells me if my alternator (regulator) is putting out about the right voltage. I check both my batteries with my multimeter to guesstimate if they're properly charged, and I occasionally take some multimeter measurements while the engine is running, to look for voltage drop in the system, which can be an indicator of dodgy contacts and less than optimum charging.

This is essentially what I run my voltmeter for. I can see when the thermo's or AC kicks in as well as if the alternators putting out when I get up to revs. Although when the alternator actually died I had a dash light to tell me so probably wasn't really required :lol:
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Re: dual battery amperage questions.

Post by Matt_85Lux »

I'm pretty sure we use drivesafe's products (low voltage cutoffs) in the caravans at work and in the 5 years I've been there I can't think of any issues we have had with them, so I can say the reliabilty is great. Will have to look into upgrading to one of those new isolators after christmas.
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Re: dual battery amperage questions.

Post by JJBigWheels »

Firstly apologies if this is a thread hijack but I think there is some relevance to the original topic. This is partly, I guess, a direct question for drivesafe. I have a safari (ie imported GQ Patrol) so my vehichle is 24 volt - ie 2 batteries but want to run a third for 12 volt accessories (there is a small nissan 12V converter which is not sufficient to even run a newer stereo). Does the isolator you produce cater for this 24V to 12V situation? I have been looking at the Redarc 1240 as this is the only unit I have been able to find that will also drop the voltage from 24 to 12 as well as isolate and charge a deep cycle properly.........well I thought? I am now a little confused.

Drivesafe - Do you have anything in your range that is suitable? Anybody else I would appreciate your thoughts ideas. Cheers Joe
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Re: dual battery amperage questions.

Post by drivesafe »

Hi 33BigWheels, while the SC80 can control two different voltage circuits and the same time, it is not a step-down device.

BUT, I am in the process of adding some new gear to my web site and this includes the range of Sterling Power Products.

One of the devices they make is their BB2412-30.

This is a 24v to 12v battery charger. It takes in up to 30 amps at 24v and produces up to 50 amps at 12v.

The normal retail price is $689 but I was talking to the supplier this morning and mentioned your enquiry and he has put a Christmas special price on the units of $599 including Express Post.

Have a look at the link below and if this is of interest to you, let me know and also ask any questions you like and I can get more info if needed.

http://powerstream.com.au/battery-batte ... p-151.html" onclick="window.open(this.href);return false;
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Re: dual battery amperage questions.

Post by GETNHI »

Hi Drivesafe,
Can you please PM me your details I would like to purchase 2 USI-160 units.
Cheers
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Re: dual battery amperage questions.

Post by drivesafe »

Hi Mick and MP sent.
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