Dual battery setup

[Matt76]

Ah cool thanks

 

[Jason]

Hey Juiced,

A car alternator/charging system can never fully charge a deep cycle battery (only gets to around 70 to 80% I think), thats why it is recommended that you hook them up to a decent battery charger now and them to top them up and remove the sulphation caused by undercharging. Over time a car charging system will reduce the life of a deep cycle battery. I have bought a CTEK charger purely for this use and to charge up some other batteries I have, it is a great charger and designed to charge deep cycle batteries, it has modes specifically for removing the sulphation.

The CTEK website has some great info on it. Battery Charger Academy

So to answer your question it won't overcharge it.

 

[Krankin]

That stuffs made to carry 15amps 240V, you want to carry 100amps at 12V there's a huge difference!! I'm not an autolec but I'm pretty sure that the current flows around the outside of the copper so more strands means the more current can be carried. eg battery cable, thick full of multistrands.

...



Just to clear the matter of cables if i may.

Auto cable is multistranded for the purpose of being FLEXIBLE due to the enviroment it is installed in and is better suited to the style of crimp lugs/connectors used in that industry.

House type 240/415V cable, with the exception of flex( which is not the same as auto cable) is installed as FIXED wiring as is not subject to the same conditions as auto wiring.

Conductors, size for size carry the same current as each other no matter auto or house, copper is copper.

The difference is fixed wiring comes under AS/NZS 3000.2007 and is for one, sized and rated completly in a different way to auto cabling with respect to a multitude of other factors,
ie: protection type,bunching, lengths, etc, etc..

I hope this helps a bit, but its only the tip of an iceberg as far as electrical theory and practice is concerned.

Conclusion... use auto wiring for vehicles.
Welding cable is ok for Battery connections, u can get it double insulated but overall is more expensive but a better cable.
Leave the house wiring where it is made for.


Cheers

 

[Nomadic Navara]

Hey Juiced,

A car alternator/charging system can never fully charge a deep cycle battery (only gets to around 70 to 80% I think), thats why it is recommended that you hook them up to a decent battery charger now and them to top them up and remove the sulphation caused by undercharging. Over time a car charging system will reduce the life of a deep cycle battery. I have bought a CTEK charger purely for this use and to charge up some other batteries I have, it is a great charger and designed to charge deep cycle batteries, it has modes specifically for removing the sulphation.

The CTEK website has some great info on it. Battery Charger Academy

So to answer your question it won't overcharge it.

For a good explanation of the 70%(or 70-80%) see THE 70% DEBATE - HOW VEHICLE BATTERIES REALLY CHARGE.

To add further to that as reasons for not overcharging an auxiliary battery - most of these batteries are mounted anywhere but under the bonnet in our trucks. The article I linked to had been kept simple. To add to that, as a battery warms up, as the cranking battery under a hot bonnet does, you have to reduce the charging voltage. Or put it another way, the colder a battery the greater the voltage necessary to charge it.

The alternator has temperature compensation built into it. As the temperature of the alternator heats up it reduces its output voltage. I have been monitoring the system voltage of my D40 diesel. As I have no load on my cigarette lighter circuits there is no measurable difference between the lighter sockets and the battery (measured.) I therefore am using one of them for the measurements.

The system voltage is generally around 12.4 V immediately before starting. After starting the motor the voltage quickly rises to over 14 V. It peaks at 14.35 to 14.65 V depending on the ambient temperature. I have even seen it peak at 14.7 V but for a very short time on a cold day. When I am 15 - 20 minutes down the road the system voltage has dropped to 13.7 - 13.9 V On a very hot day I have seen it down to 13.6 V.

Loading and terrain have an effect on the running voltage. In hilly country the voltage drops when climbing and rises when descending hills. On one coolish afternoon I observed the system voltage average 13.85 V on the outward journey. On the return journey I was towing a 2 T van, the system voltage then averaged 13.75 V.

With alternators like I have measured on my D40 you can not charge a battery in a timely manner let alone overcharge it. If I did not have a RanOx battery booster in my van I would be hardly giving any charging to my battery.

PeterD

 

[Krankin]

For a good explanation of the 70%(or 70-80%) see THE 70% DEBATE - HOW VEHICLE BATTERIES REALLY CHARGE.

To add further to that as reasons for not overcharging an auxiliary battery - most of these batteries are mounted anywhere but under the bonnet in our trucks. The article I linked to had been kept simple. To add to that, as a battery warms up, as the cranking battery under a hot bonnet does, you have to reduce the charging voltage. Or put it another way, the colder a battery the greater the voltage necessary to charge it.

The alternator has temperature compensation built into it. As the temperature of the alternator heats up it reduces its output voltage. I have been monitoring the system voltage of my D40 diesel. As I have no load on my cigarette lighter circuits there is no measurable difference between the lighter sockets and the battery (measured.) I therefore am using one of them for the measurements.

The system voltage is generally around 12.4 V immediately before starting. After starting the motor the voltage quickly rises to over 14 V. It peaks at 14.35 to 14.65 V depending on the ambient temperature. I have even seen it peak at 14.7 V but for a very short time on a cold day. When I am 15 - 20 minutes down the road the system voltage has dropped to 13.7 - 13.9 V On a very hot day I have seen it down to 13.6 V.

Loading and terrain have an effect on the running voltage. In hilly country the voltage drops when climbing and rises when descending hills. On one coolish afternoon I observed the system voltage average 13.85 V on the outward journey. On the return journey I was towing a 2 T van, the system voltage then averaged 13.75 V.

With alternators like I have measured on my D40 you can not charge a battery in a timely manner let alone overcharge it. If I did not have a RanOx battery booster in my van I would be hardly giving any charging to my battery.

PeterD

Pete,
if i can add to this,
I,m not aware of any alternators that have purposely inbuilt features to lower voltage output as temp go's up, but,
what i can add is that conductors have a resistance.
As current flows, heat builds up.
the more current the more heat, the more heat the bigger the volt drop hence your lower volt readings as the overall temp rises.
all conductors have differing resistances...Gold has lower resistance than copper but is less feasable than copper overall,but gold and silver are used extensivly in electronics and PCB's.
Resistance is lower with colder temps therefore alt output is higher in the cold morn's.
Lead for example is a superconductor at around -245 degreeC meaning it has no resistance at that temp but its not practicable for use in everyday scenarios.

Jim.

 

[Nomadic Navara]

Pete,
if i can add to this,
I,m not aware of any alternators that have purposely inbuilt features to lower voltage output as temp go's up, but,
what i can add is that conductors have a resistance.
As current flows, heat builds up.

Jim.

Then have a look at Car and Deep Cycle Battery Frequently Asked Questions (FAQ) Section 5. Just over half way down the page you will see the temperature compensation characteristic for Bosch alternators. The text above it states:

"As in the Bosch Voltage Regulator example below, most voltage regulators are temperature compensated to properly charge the battery under different environmental conditions. As the ambient temperature decreases below 77° F (25° C), the charging voltage is increased to overcome the higher battery resistance. Conversely, as the ambient temperature increases above 77° F (25° C), the charging voltage is decreased. Other factors affecting the charging voltage are the alternator temperature, battery's condition, State-of-Charge (SoC), sulfation, electrical load and electrolyte purity."

PeterD

 

[Krankin]

Then have a look at Car and Deep Cycle Battery Frequently Asked Questions (FAQ) Section 5. Just over half way down the page you will see the temperature compensation characteristic for Bosch alternators. The text above it states:

"As in the Bosch Voltage Regulator example below, most voltage regulators are temperature compensated to properly charge the battery under different environmental conditions. As the ambient temperature decreases below 77° F (25° C), the charging voltage is increased to overcome the higher battery resistance. Conversely, as the ambient temperature increases above 77° F (25° C), the charging voltage is decreased. Other factors affecting the charging voltage are the alternator temperature, battery's condition, State-of-Charge (SoC), sulfation, electrical load and electrolyte purity."

PeterD

The passage above and the voltage graph both show what i"ve said.. temp increases-voltage decreases.

Also I've not seen any Bosch alt's on jap manufactered vehicles. (correct if wrong)

Also Voltage regulators ( for the purpose of output) sense the batt voltage via the sense wire and (not by ambient temp) control this voltage by switching the alternator excitation field current on and off.
If batt voltage is below regulated voltage, the power transistor is switched on.
If batt voltage goes higher than than spec limit, the transistor is switched off, causing voltage to drop.

Also of interest is that the Functional diagram does not show the true picture of an alternator because in actual fact they generate a 3phase AC current which is rectified by 6 to 8 Zener diodes down to Dc output.

Never the less the article is an interesting read...Thanks.

 

[Bosshog]

Mate and I put a dual battery (105 ah) in my D40 during the week. As you can see its mounted it in the tray. I screwed a merit socket to the bullbar for the air compressor etc. Two merit sockets and two conventional 12v sockets also in the tray tucked up out of harms way. Most importantly designed it so that it allowed room for a sliding tie down point to get into the corner.

Also rewired the GPS, UHF and the in-dash 12v socket into to second battery all are routed through a seperate fuse box. Wired in the monitor and the 'red button' (to enable the second battery to act as the crank) this afternoon.

Gus

 

[yz250muz]

in the process of fitting a dual battery set up in my d21 . im a bit of a tight arse so im using a 100 amp relay and switching it with the oil presure switch so it is only connected to the main battery when the oil pressure is up (engine running) so i cant leave the ingtion on while camping and drain the main battery. hope this helps

 

[Old.Tony]

That's pretty clever!

 

[SOLID D22]

in the process of fitting a dual battery set up in my d21 . im a bit of a tight arse so im using a 100 amp relay and switching it with the oil presure switch so it is only connected to the main battery when the oil pressure is up (engine running) so i cant leave the ingtion on while camping and drain the main battery. hope this helps

Instead of calling yourself a t arse, that is actually very clever, by the sound of it you have eliminated the use of a solenoid.

 

[WIR35]

in the process of fitting a dual battery set up in my d21 . im a bit of a tight arse so im using a 100 amp relay and switching it with the oil presure switch so it is only connected to the main battery when the oil pressure is up (engine running) so i cant leave the ingtion on while camping and drain the main battery. hope this helps

That's clever, not tight!

 

[Oudaere]

So sh*t they don't fit in under the bonnet!!!!!

 

[user 1279]

Mate and I put a dual battery (105 ah) in my D40 during the week. As you can see its mounted it in the tray. I screwed a merit socket to the bullbar for the air compressor etc. Two merit sockets and two conventional 12v sockets also in the tray tucked up out of harms way. Most importantly designed it so that it allowed room for a sliding tie down point to get into the corner.

Also rewired the GPS, UHF and the in-dash 12v socket into to second battery all are routed through a separate fuse box. Wired in the monitor and the 'red button' (to enable the second battery to act as the crank) this afternoon.

Gus

Bosshog ... thanks for posting the picks. Looks good. Where did you get your battery tray from (and how much) ?

Does the top of the battery box sit higher than the side of the tray or does it just fit ?

What size cable did you run to your rear battery and what size circuit breakers did you put on each end ?

Cheers ... Gregg.

 

[run a muck]

Guys I hope this works as it is my first attempt at posting pics.
This is my new Thumper 105 amp hr pack that I have just had fitted... Comes with jumper leads via an Anderson plug connection plus you can see at the push of a buttom how much charge is left... Plus a couple of aux power outlets... Hope this helps others with limited space for a dual set up.......

 

[ljacko78]

looks pretty soild Muck.... what did that box set you back?

I just put in a projecta 150 isolator kit and 90A bat in my D22. was hoping to squeeze one in under the hood, but it's ended up in the tray as well in a $25 SCA box. Which is working perfectly with my new CF80 waeco

 

[run a muck]

Jacko.... The whole thing supplied & wired in was around $1400... I know that sounds hexy but this can be removed if you need it closer to your camp site, or fit to another truck....
It will run my 80ltr Waeco at -15 for at least 3days.... Whole things is about 28kgs so its not light...

 

[asthomas]

Hi
Don't know if this helps or not, I put an Anderson Plug on the back of my D40 ST and ran the cable from the battery down through the chassis rails, made the job so much easier used the heavy duty cable from ABR - SIDEWINDER with one of his dual battery relay boxes.
Mounted that on the flat plate between the battery and engine.

 

[WIR35]

Now that my drawers are finished, I've finally got around to buying stuff for my dual battery kit. I have an 09 D22 with standard dual batteries, but for the uninitiated both batteries are mounted under the bonnet in parallel from the factory.

My plan is to remove the battery & tray from under the bonnet, and mount it in a hatch that I've made up under the false floor in my drawers (pics will follow). I will either mount the ABR Sidewinder 140A auto isolator under the bonnet or inside the same hatch in the tray - not sure yet. I've ordered a 60A circuit breaker which i will mount under the bonnet. I will run either 16mm2 or 25mm2 flexible orange XLPE cable, with some good solid crimp lugs (XLPE has a layer of hard plastic insulation around the core and then an outer sheath as well - better current carrying capacity and better mechanical protection too). I will wire in an anderson plug close to the second battery so that I can remove it easily if need be. I've also bought a 600w (1200w max) inverter which will also go in the hatch, and will wire in a 240v IP56 socket outlet near the rear of the tub for plugging in fridges/power tools/work lights etc....

Will get stuck into it next weekend so hopefully should have some photos up then.

I'll persevere with the stock battery until it either packs it in, or I get sick of it not holding decent charge, but we'll see how it goes. I'm not going to go to the expense of buying a deep cycle battery yet, just see how it goes....

 

[WIR35]

Found that the 2nd battery didnt charge enough and ran low. To much voltage drop with the cable I used.

I just removed the black conductor from the negative post on both batteries and joined it at each end with the red conductor to double the cable capicity between the Positive on both the batteries.

I just then ran a earth from the second battery to the body of the tub.

When the engine is running now the voltage drop between the front battery and the 2nd is only 0.3v.

The 2nd battery was only running at 12.7v before and now runs at 13.6v so should charge ok I think.

Took some pics to ilustrate cable entry to the tub ect.

Hey mate,

Not trying to have a go at you or anything, mainly just trying to help you, and others reading this thread so they don't get themselves into any strife, and can maybe get their systems right first time. I read that you seem to have it sorted now so that's good.

Your old relay setup would have worked 'okay', but the main problem with that is that means your aux battery will be connected to your main battery when you turn your key on. This means that if your aux battery is flat, it will draw a lot of current from your main battery to level out the charge, thus drastically reducing the voltage and current capacity to start your engine (as well as being not good for your whole vehicle electrical systems & starter motor)- all at the same time. As you've changed it to an isolator, then that should solve this problem. There are other ways to do it using clever ways such as previously mentioned on this thread, using oil pressure or engine temperature switches, or using battery chargers between the main battery and aux battery, but for most people the isolator is easy and it works.

Cable use - 2.5mm2 TPI cable is good for up to 24-25amps @ 240v (at absolute best), but ELV systems suffer from far greater voltage drop, so for the length of cable between your main battery and aux battery, it's probably good for less than half that, maybe as low as 5-10 amps. So even doubling up the conductors in parallel is only going to give you around 20 amps. Also, 240v cable is a no-no, the strands break very easily with the vibrations in a vehicle, and when a strand breaks it creates a hot spot in that section of the cable and reduces the current carrying capacity, then the insulation will melt, possibly catch fire etc. And then if it touches the chassis with no insulation, you'll either blow a fuse (at best) or if you haven't properly fused the cable anywhere then you'll short out your battery and probably blow it up or cause serious damage to your car's electrics. Oh, and remember to use a cable for your negative/ground wire that will carry the appropriate current for your equipment, it's just as important as running the right sized positive cable. It doesn't necessarily need to be the same size as the positive cable, generally you would bolt the negative cable to your chassis very close to the actual equipment, so you don't need to allow for as much voltage drop. If your ground wire is too small, or if you have a bad connection to the chassis, the cable will melt.

People should keep in mind that even though you're only dealing with 12 volts, and the voltage isn't enough to electrocute anyone, it's still enough to cause a fire or a battery explosion.... Even auto electrical needs to be treated with respect, so if you're not trained or at least have a good degree of knowledge about it, I would recommend leaving it to the professionals, or at least discuss your plans with a professional and get them to check it over for you once you're done. After all, you don't your electrical work causing your car to catch fire, or frying your car's electrical system.

Even as a licenced electrician & electrical engineering student, I will still consult my auto electrician friend from time to time, there's a good reason why they spend 4 years learning their trade...