Deep Cycle Battery Setup

Submitted: Wednesday, Mar 17, 2021 at 14:15
ThreadID: 141265 Views:9437 Replies:8 FollowUps:10
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Hi there,

Very new to all this. Just got a 2013 Prado and have some camping gear for the family. Looking at a deep cycle battery setup to run a fridge, lights, and basic accessories. Wouldnt plan to be off-grid for too long at a time. 2-3 days without access to mains power max.

What I want to run with is:
inside the
- Engel Smart Battery Box Series 2

Firstly, does this work? Secondly, what's the cleanest and easiest way to keep this charged when driving? My prado has a 220v socket in the rear cabin? But I don't think this will be sufficient? The other way is to run to a 12v cigarette lighter socket, but that's all the way at the front. Seems messy.

What do other people do? How tricky is it to get a 12v socket in the rear cabin?

Any guidance here would be appreciated.

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Reply By: Frank P (NSW) - Wednesday, Mar 17, 2021 at 14:40

Wednesday, Mar 17, 2021 at 14:40
I cannot find the specs of the lithium profile in the charger in the battery box. Assuming they suit your planned battery, all should be good.

What is the max wattage of the 220V socket in the Prado's rear cabin? There will be an inverter somewhere which will have a wattage rating. It MAY be enough to run the box's mains input. You will also need to find out what mains wattage the box requires.

If this option is no good, then you need a 12V source. Ciggy sockets are notoriously unreliable in this application and standard wiring associated with them is inadequate. IMO you will need to run 8 AWG wiring from the engine battery to an Anderson or similar positive-locking plug and socket in the rear cabin. It's not easy to do neatly but can be done. You will have to remove or loosen some plastic trim and replace it, as well as find a location to pass the cabling through the body shell in the run to the engine bay. Look for dust plugs under the carpet.

I did it myself for a 2007 120 Series Prado years ago. It is fiddly but do-able for DIY.


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Reply By: RMD - Wednesday, Mar 17, 2021 at 15:21

Wednesday, Mar 17, 2021 at 15:21
Everyone has their own way or preferences. Do you need a smart battery box? perhaps just the battery plus other gear may suffice.
Firstly, if using a Lithium battery in a case you will need to charge it via 240v ac and using a 240v ac lithium charger or from vehicle or solar. A 240vac charger with Lithium profile charging will be needed if using the battery until getting to 240v power again. The way to charge the battery from the vehicle is to use a DC DC type charger which also has a specific lithium charge ability. Many devices use vehicle power and/or solar input to correctly charge the lithium battery. These usually require a dedicated line from vehicle battery system/alternator to do the lithium charge.
The 240v ac OUT in the Prado is probably only a small capacity 12v to 240vac inverter which most likely isn't a FULL SINE WAVE device and so what you plug into it has to be able to accept the “so called” modified sine wave power coming out of that base. Modern electronic fridges don't like that power type if ever using it for direct 240v connection to fridge and any modern inverter/switchmode power supplies used in laptops or Engel battery boxes may also not start or run hot. Best to have a full awareness of capabilities there, regarding 240 vac vehicle outlet and what the battery box likes to use/accept. Just don't believe any salesman's claim without being sure.
Using a ciggy plug power system isn't very good as it is limited in current ability and battery charging requires a decent sized cabling to the charger device. Ciggy ok for light duty though, but if used for a fridge supply while travelling they work loose and become hot and can burn the plug. If running fridge in vehicle, an Anderson plug on both the dedicated “from engine” battery charge line and the fridge wire supplies secure power.
Although adding a heavy cable run from engine bay to rear seems messy or tricky, it is really a straightforward addition to the vehicle and once done, it is then trouble free for future usage.
Not sure what an Engel battery box has in it, but you need the lithium 240v ac charger somewhere in the mix to use as required, also a DC Dc unit which uses alternator power to charge the lithium while driving. If the DC DC also has solar input, advise you have that, then portable solar panel or blanket can keep you out in the scrub for longer.

Once you have a DC DC unit to charge the battery, then a normal 240 vac multi stage battery charger can be used to apply to the engine battery, raise it's voltage as in charging and that additional voltage will activate the DCDC unit to charge the Lithium battery in the box. A slower process, but no other separate lithium charger would then be required, as was mentioned previously because you have a DC DC unit for solar or engine power charging.
AnswerID: 635643

Follow Up By: Frank P (NSW) - Wednesday, Mar 17, 2021 at 16:53

Wednesday, Mar 17, 2021 at 16:53

The Engel battery box has a 240V charger and apparently a DC-DC charger plus a small inverter, all within. They say the chargers are lithium compatible, so following Bazooka's post below, I think all the OP needs is some decent cabling from the crank battery to the rear cabin, terminating in an Anderson or suitable positive-locking alternative.

The battery box does not have solar input. If the OP wants to use solar he will have to get a lithium-compatible regulator.


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Reply By: Bazooka - Wednesday, Mar 17, 2021 at 16:15

Wednesday, Mar 17, 2021 at 16:15
From what I've read on Prado forums the rear outlet spec for the 150 is 220V, ~0.45A, 100W.
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Follow Up By: Frank P (NSW) - Wednesday, Mar 17, 2021 at 16:47

Wednesday, Mar 17, 2021 at 16:47
Thanks Bazooka. Probably a bit skinny for the OP's application.

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Reply By: Bazooka - Wednesday, Mar 17, 2021 at 16:50

Wednesday, Mar 17, 2021 at 16:50
Andrew - a few things to consider:

Some fridges will happily run directly from that outlet but you'd need to test yours. That would save the lithium/battery box for your camp.

Some back of the envelope numbers worth knowing (you can test these later).
- Depending on your fridge, how packed it is and how often you access it, environmental conditions, etc you'll use ~30+A/day.
- Lithiums can be run flat (ie to around 11.5V) but for longevity most retailers suggest limiting your use to ~80% DoD which equates to nearly 3 days off grid with no topping up for your 100Ah battery. 120Ah would be better obviously, but more expensive. The Renogy capacity should be accurate, unlike many cheap Ebay LiFePO4s.

The setup required really depends on what you intend doing and how long you're away from 240V - ie are you intending to move around and are reliant on alternator re-charging for your lithium or will you have access to 240V every few days?

Have you considered solar for keeping the battery topped up?
AnswerID: 635648

Reply By: Member - McLaren3030 - Wednesday, Mar 17, 2021 at 17:16

Wednesday, Mar 17, 2021 at 17:16
Hi Andrew,

Seeing as you said you are new to this, and not sure what you are doing, I would strongly advise you seek advice from a reputable Auto Elec. Not that the advice being provided here is wrong or bad, in fact it is exactly what you need to do, just that if you do not know what you are doing, there is a good chance that you could damage your vehicle’s electrics, the auxiliary battery and/or the fridge.


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Follow Up By: RMD - Wednesday, Mar 17, 2021 at 17:43

Wednesday, Mar 17, 2021 at 17:43
Good advice Macca, There are lots to consider with aux battery systems and unless Andrew's money supply is endless, a few options offered may allow him to choose wisely first time. We have never wasted any money have we, oh no not me. An Engel smart box may be ok in this case but not my desire though.
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Reply By: Andrew W36 - Wednesday, Mar 17, 2021 at 22:17

Wednesday, Mar 17, 2021 at 22:17
Great advice all,

Ill run with the Engel box as it should be a complete system and ready to go. Various options for charging inc 240v and has a 240 outlet with internal 300 watt inverter. That will cover me.

Looks like ill get an auto electrician to run cabling from the engine battery to the rear cabin and charge via the Anderson. The 220v outlet in the prado I dont think will cut it.

Also, if i think ill need it. Ill get a solar panel with its own regulator and go into the anderson plug or the terminals provided on the box. Doing some reading on the Engel, this should be fine.

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Follow Up By: Frank P (NSW) - Wednesday, Mar 17, 2021 at 22:57

Wednesday, Mar 17, 2021 at 22:57
Just make sure your auto sparky uses 8 AWG cable or better, and fuse (25A should be ok for your 7amp charger) near the engine battery.

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Follow Up By: qldcamper - Thursday, Mar 18, 2021 at 08:04

Thursday, Mar 18, 2021 at 08:04
Frank, if he chooses to take it to a sparky it is because he wants professional workmanship.
Dont tell someone that specialises in something how to do their job, it just pisses them off.
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Follow Up By: Frank P (NSW) - Thursday, Mar 18, 2021 at 09:00

Thursday, Mar 18, 2021 at 09:00

If you contract work out you have to specify the work to be done, otherwise the contractor is working blind.

IMO "Put an Anderson in the rear cabin" is not an adequate spec and invites a less than adequate result.


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Follow Up By: qldcamper - Thursday, Mar 18, 2021 at 10:45

Thursday, Mar 18, 2021 at 10:45

A good sparky working blind is a lot more reliable than armchair experts on a forum.

A sparky working in the field will do more installs in a week than most people on forums do in a lifetime so if you think they need to be micro managed you have the wrong sparky.


Find a decent auto elec, tell him what you want to achieve and then let him suggest the best way to achieve and let him (or her) engineer the system as he will be more familair with the products on hand than anyone on forums that might have put together a couple of set ups.

They dont have to look up specs on the intetnet because they have done it many times before and get to know their products and know what works and what doesnt.
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Reply By: Member - LeighW - Thursday, Mar 18, 2021 at 14:59

Thursday, Mar 18, 2021 at 14:59
It is relatively easy to get power to the rear of the Prado if you know how to remove the sill trims etc. Most run cable through the left side cable grommet into the interior and then through the sills. Be careful penetrating the cable grommet as many have come to grief damaging the wiring loom.

Prado charge voltage is pretty much ideal to directly charge a Lithium, starts off around 14.2V in temperate climate and drops to around 13.5V, Many Lithium profiles are around 14.2V - 14.4V and 13.8V float. The higher charge voltage is really only required for cell balancing and if the Lithium gets to full charge occasionally the 14.2V will allow cell balancing.

Personally I'm running a specialty Lithium under bonnet with very good results so far.

A 40ltr fridge/freezer will consume around 2Ah per hour in temperate climates, or 48Ah per day, asking 3 days out of a 100Ah battery is a big ask.

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Follow Up By: Bazooka - Thursday, Mar 18, 2021 at 18:49

Thursday, Mar 18, 2021 at 18:49
Different setups and usages will (obviously) result in widely varying daily Ah usages Leigh but that 2A/hr (probably closer to 2.5-3A) is when the fridge is running. If a fridge is typically running 24 hours a day on a 2-3 day outing then there's something wrong. Doing simple things like running your fridge at home before setting out and packing pre-chilled food should ensure it doesn't need to be constantly cycling. Better to be on the conservative side until you actually test your setup in the field though :-).
Useful power usage info here for anyone interested:
12 Volt Blog

Just fyi Andrew. Did a bit more reading on the Pradopoint forum and apparently there is an unused 12V plug behind the panel adjacent to the 220V outlet. Problem is the wires are very thin so not ideal for your application. Handy knowing though.
Pradopoint link

The wires for the 220V outlet are also thin. Don't know what Toyota was thinking when they did that.

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Follow Up By: Member - LeighW - Friday, Mar 19, 2021 at 19:49

Friday, Mar 19, 2021 at 19:49
My Waeco 40ltr units consumes around 2Ah per hour running as a freezer set to -15C in temperate climates. 80ltr consumes around 4Ah per hour. Actual consumption per hour not running current.

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Reply By: Member - peter g28 - Saturday, Mar 20, 2021 at 22:29

Saturday, Mar 20, 2021 at 22:29
I agree with many of the comments..the vehicle cig socket will not "cut it" lithium batteries will take all the amps you can throw at them due to their efficiency, so you "may" have the problem of the wiring to the cig socket overheating.
That being the case...
The Renogy lithium100Ah battery for the price point is a good purchase...Will Prowse on his Youtube channel did a complete tear down of this battery and was impressed with the build quality of the BMS, its connections, wiring and lithium pouches.
In regards the wiring to battery is best to run the wiring from the engine bay and terminate it with a Anderson plug, but with a decent amp fuse on the positive lead.
AnswerID: 635681

Follow Up By: Bazooka - Sunday, Mar 21, 2021 at 12:26

Sunday, Mar 21, 2021 at 12:26
While good 12V LiFePO4s with decent BMSs can apparently take charging up to 1C Peter the conventional wisdom is that fast charging reduces battery life. Hence most reputable sellers recommend roughly 0.3C, or 30A for a 100Ah battery for example.

Enerdive Specs for example:
Battery................EPL-100BT-12V...............PL-125BT-12V............EPL-200BT-12V G2...........EPL-300BT-12V
Max Charge....50A @ 25C 30mins.......60A @ 25C 30mins.......150A @ 25C 30mins.......150A@ 25C 30mins
Rec Charge ...............<=33A.............................<=40A....................................<=60A.................................<=90A

Will Prowse is very good!
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