Proposed vehicle power system

Submitted: Wednesday, Apr 02, 2008 at 16:39
ThreadID: 56194 Views:2213 Replies:4 FollowUps:13
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Hi All,

I want to run a recently aquired 35 litre Weaco compressor fridge in the cargo area of the Prado and am checking out the best overall power system to keep it going on a permanently installed basis. This is in addition to a 40 litre Weaco that will only be in the car for trips where one can be a fridge and the other can be a freezer.

The vehicle already has a Pirahna DBS180 dual battery controller feeding a Trojan 115AH deep cycle wet cell mounted in the engine bay. There is a 6mm cable from the deep cycle to the cargo area terminating in two hella plugs.

I have two new 100AH sealed lead acid batteries that I want to mount in the cargo area and they will fit neatly ahead of the fridge (behind the 2nd row seats) with appropriate securing frame bolted to floor.

I am looking at connecting an Arrid twin charge unit between the existing 6mm cable from the dual battery and the two rear batteries. I am also looking at an adjustable low voltage cutout between the Arrid and the dual battery set to around 12.8v.

This would mean whenever the underbonnet dual battery is receiving a charging voltage from the Pirahna controller (alternator is running) then the Arrid will also be charging the cargo area battery bank.

When the engine is off the Arrid would continue to charge the rear batteries until the voltage in the front battery drops to 12.8 and the low voltage device cuts it off. Same would apply if I was camping and put my generator powered charger on the front battery.

The rear battery bank would run the installed fridge. I can still run the 2nd fridge off the front dual battery if required and all batteries get charged whenever alternator or charger power is available.

Can anyone see any issues with this system or offer any contructive comments?

Cheers
Muddy
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Reply By: Sand Man (SA) - Wednesday, Apr 02, 2008 at 16:56

Wednesday, Apr 02, 2008 at 16:56
Hi Muddy,

The 12.8V cutout doesn't sound right to me.
12.8V is virtually fully charged.

11.8V is around 30% remaining in the auxiliary battery and would be more practical I believe.

Bill.

Bill


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AnswerID: 296155

Follow Up By: Muddy doe (SA) - Wednesday, Apr 02, 2008 at 17:06

Wednesday, Apr 02, 2008 at 17:06
The 12.8 is high because I don't want to take a lot of charge out of the front battery to charge the rear ones. In effect I am routing the charge to the rear Arrid charger VIA the already installed Pirahna system and the front battery.

If I did not put in a low voltage cutout then the Arrid would continue charging the rear batteries until the front battery was flat and that would not be good long term. I really only want to Arrid to charge the rear batteries when the front is getting alternator or charger power.

The alternative is to run another cable to the cargo area for a seperate charging system but it starts to get messy. I want to use what is already there to best effect and only add the minimum.

The attraction of the Arrid is that it ups the voltage a bit so that the rear battery bank gets optimum charge while driving.

Muddy
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Follow Up By: Member - Roachie (SA) - Wednesday, Apr 02, 2008 at 17:19

Wednesday, Apr 02, 2008 at 17:19
Sounds like a perfectly feasible system to me Muddy.

Because you will be driving the Prado virtually every day, there should be enough charge being put into the rear batteries to cater for the 35 litre fridge running 24/7.

Cheers

Roachie
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Reply By: Member - Andrew L (WA) - Wednesday, Apr 02, 2008 at 17:23

Wednesday, Apr 02, 2008 at 17:23
I've got a Prado with the fridge in the back and an 110AH AGM battery in front of the fridge (same as you). I'm using a 1000W pure sinewave inverter and 30 Amp 3-stage battery charger to charge the AGM.
I've got two 100Amp solid state relays in the circuit:
1. to isolate the inverter from the main battery when the vehicle is not running.
2. To isolate the battery from the charger whent he vehicle is not running.

I changed to this system after having issues with a redarc / wetcell under bonnet system. This set up gives me a much better recharge rate and fully charges the battery, allowing me to stay in one place longer before needing to recharge.
There are the additional benefits of having 240Vac available in the vehicle and being able to recharge the battery from any 240VAC supply (generator , caravan park etc.)
I have mounted the inverter and charger next to the fridge by utilising the third row seat mounting point.

I looked at the Arrid twin charge but was unable to get any written information about the I-V output characteristics of the unit.
Redarc also make a unit that is a boost converter with a 3-stage battery charge output. But the output is only 7amps, which was less than what I wanted.
Leachy
AnswerID: 296161

Follow Up By: Muddy doe (SA) - Wednesday, Apr 02, 2008 at 17:45

Wednesday, Apr 02, 2008 at 17:45
The Arrid is supposed to be a 20 amp charger looking at their website but I agree the amount of technical data on it is somewhat limited!

Inverter system sounds ok as well but I'm not too keen on having 240v happening in a moving vehicle.

Cheers
Muddy
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Follow Up By: Member - Mark E (VIC) - Thursday, Apr 03, 2008 at 03:20

Thursday, Apr 03, 2008 at 03:20
Re the Arrid Twin Charge........

I once rang them trying to get some answers to a number of technical questions about the unit, but found them to be unwilling/unhelpful (lacking in knowledge?) about the units, so passed on them.

Cheers,

Mark
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Reply By: KSV. - Wednesday, Apr 02, 2008 at 17:37

Wednesday, Apr 02, 2008 at 17:37
As for me sounds very well though trough set-up. Only one thing what I can suggest instead of low voltage cutoff device just put simple 30A relay and activate it only when engine is running.

Cheers
Serg
AnswerID: 296166

Follow Up By: Muddy doe (SA) - Wednesday, Apr 02, 2008 at 17:40

Wednesday, Apr 02, 2008 at 17:40
Yep that sound like what i am looking for!
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Follow Up By: Member - John and Val W (ACT) - Wednesday, Apr 02, 2008 at 18:15

Wednesday, Apr 02, 2008 at 18:15
Muddy,

"I really only want to Arrid to charge the rear batteries when the front is getting alternator or charger power." I agree with KSV - a relay operating while the engine is running will ensure the Arrid only receives power when the alternator is running. The only downside is that the relay wont operate automatically with the charger running. Can your charger provide the 20A for the Arrid plus anything useful to the wet battery at the same time? Probably not. I think I'd connect the charger directly to the rear batteries on the few (?) occassions it's needed there, and independently to the wet battery as required. It's a bit manual, but you'll know exactly what's happening.

One difficulty with the 12.8v sensing is that it may well hunt - you'll quickly lose your 12.8V once the arrid cuts in, which will disconnect the Arrid, so voltage rises, cuts in, cuts out.......

HTH

John
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Reply By: Member - Olcoolone (S.A) - Wednesday, Apr 02, 2008 at 18:20

Wednesday, Apr 02, 2008 at 18:20
Why do you want to make it so complicated and use an Arrid twin charge?

The 6mm cable is way to small for what you are trying to do, would recommend 3 B&S min.

I would not use the Arrid twin charge and just use the 3 batterys in parallel or if you want to isolate the 2 rear batterys when the voltage drops below 12.8 volt, use a Redarc smart solinoid between the two back batterys and the aux one under the bonnet.


Regards Richard
AnswerID: 296175

Follow Up By: Member - Mike DID - Wednesday, Apr 02, 2008 at 18:37

Wednesday, Apr 02, 2008 at 18:37
I agree, you will get MUCH better value for money if you put in an adequately sized cable - from front to rear - 4Ga minimum.

Arrid's are good - but they can't create power. Forget the Arrid.
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Follow Up By: Peter McG (Member, Melbourne) - Wednesday, Apr 02, 2008 at 19:31

Wednesday, Apr 02, 2008 at 19:31
Was just about to ask the same question. I'd first check voltage at the rear batteries. I get 13.8 at the battery in our camper from a piranha setup which is exactly what the Arrid provides. Check cable size and voltage first I reckon. You should get about 2 days from the Trojan battery when camped and with daily driving it should eb enough for the Waeco.

Peter
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Follow Up By: KSV. - Thursday, Apr 03, 2008 at 09:00

Thursday, Apr 03, 2008 at 09:00
Muddy’s idea is totally right – use not so thick cable to back only to use it for charging back battery, i.e. need to carry 20A max and 6mm totally adequate to do this. But you *WILL* have voltage drop even if use thick 4GA cable, thus Arrid charger came very handy. And fridge itself will be run directly from rear battery. As I said in my post above I recon this is very well though through setup. Probably (just probably) a little overkill, but promise to be very robust. If I ever decide to put extra battery in the back, I am surely follow similar path.

To Mike DID – Arrid can not create power, but it can increase voltage effectively compensate for any voltage drop. It is actually brilliant idea and Muddy use it just as it intended to use.

Cheers
Serg
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Follow Up By: Member - Olcoolone (S.A) - Thursday, Apr 03, 2008 at 21:48

Thursday, Apr 03, 2008 at 21:48
Why not do it right the first time?

Why use an Arrid when it is not needed?
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Follow Up By: Member - Roachie (SA) - Thursday, Apr 03, 2008 at 22:00

Thursday, Apr 03, 2008 at 22:00
I use an Arrid to charge my Fullriver and am thinking of adding another one to the camper trailer. They have the ability to provide a higher voltage, using thinner cable, than the alternator actually pumps into the main batteries on my rig. Sounds strange, but's what happens.

Roachie
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Follow Up By: Muddy doe (SA) - Thursday, Apr 03, 2008 at 22:07

Thursday, Apr 03, 2008 at 22:07
I looked at the Arrid as I had seen it in Roachies setup. It seems to be able to deliver a good charge voltage irrespective of location in the vehicle.

I don't want to parallel the 3 batteries because they are not all the same type. The wet cell up front is also nearing 4 years old while the SLA'a are new. The Arris is in effect an isolator and charger in one.

Anyway - some good points raise in this post which is why I posted it in the first place. It pays to ask!

Thanks for the support Serg! I thought it was a good idea and am yet to be convinced that there is anything wrong with my idea. Just wanted advice as to whether there was a better way, taking into account what is already installed.

Cheers
Muddy
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Follow Up By: Member - Phil G (SA) - Thursday, Apr 03, 2008 at 22:18

Thursday, Apr 03, 2008 at 22:18
Arrid bumps the voltage up to a steady 14.4 volts, which is a bit more than you'll get out of most alternators anyway - especially some of the Toyota ones that drop to 13.5v as the temp warms up.
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