Battery management in the 200 series

Can anyone advise the best way to set up battery management in the new 200 series landcruiser when using a 12V fridge in the back
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Reply By: Battery Value Pty Ltd - Friday, Jul 16, 2010 at 21:44

Friday, Jul 16, 2010 at 21:44
Replace your cranking battery with a 50Ah, 800CA, 690CCA spiral wound deep cycle AGM cranking battery.
Double up the capacity by wiring another one of these in parallel as your auxiliary battery B&S 1 or 0 wire.
No relays, no isolation switches, no hassles.

Gives you more than two days of fridge run time (compressor fridge), and have enough juice left to start your 4WD.

Best regards, Peter
AnswerID: 424263

Follow Up By: Willharry7 - Friday, Jul 16, 2010 at 23:36

Friday, Jul 16, 2010 at 23:36
Hi Peter,

thanks for your reply. So just to confirm you are saying to replace one of the 2 standard batteries with 2 of those your described connected in parallel
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Follow Up By: Member - Captain (WA) - Saturday, Jul 17, 2010 at 06:02

Saturday, Jul 17, 2010 at 06:02
But what happens if you run the fridge in freeze mode on a couple of hot days? The problem with not using an isolator is that you will need to monitor power usage and voltage levels otherwise you may not have enough power to start the vehicle. It may be simple but how does this improve the current setup and thats after spending close to $1000?

As John mentions below, check out the LCOOL site, here is a link to one of the battery threads (use the site search function for more), follow it thru and there are pics of some installlations as well as some good discussion on various ways of having an aux battery.
LCOOL Aux battery thread


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Follow Up By: Battery Value Pty Ltd - Saturday, Jul 17, 2010 at 11:17

Saturday, Jul 17, 2010 at 11:17
@ Captain,

fridges have a low voltage cut out device, leaving enough charge in the starter battery for cranking.
Spiral wound AGM batteries have the advantage here because they keep their internal resistance low even in partially discharged state.
BTW, the setup cost for a couple of 50Ah spiral wound AGM batteries doesn't have to be more than 450 bucks, batteries and heavy gauge wires included.
A stylish sub 20 Dollar voltmeter you plug into the ciga lighter for a good indication of state of charge in your batteries is definitely an advantage.

Of course, if you feel you need to make this more complicated, please read on ;)

@ Willharry,

you're welcome.

Here are the following options for you:
1) leave everything unchanged:
existing wet cell batteries not being designed to sustain repeated deep discharges (say below 20% SOC) will show accelerated ageing.

2) replacing just the auxiliary battery with spiral wound AGM:
that's ok, if you isolate it from the flooded cranking battery with an isolation switch (manual, solenoid, or electronically controlled solenoid). If you don't isolate it, your cranker will suffer the same fate as describded in option 1.

3) like 2, except for substituting the spiral wound AGM with a flat plate deep cycle AGM battery:
flat plate batteries suffer more under high temperatures than pure lead/tin spiral wound AGM, because corrosion effects are more pronounced due to calcium and other alloying ingredients in the grids (which are necessary to give the flat plate structure the required stiffness).

4) replacing both wet starter and auxiliary batteries with spiral wound AGM:
both batteries can contribute to the deep cycle load pattern, and can share the high cranking current if not isolated by an electronic solenoid.
If you rather have them separated by an isolating device, that's ok too if you don't mind the lower available capacity.

Pros, cons and costs of each option:
1) cheap in the short term, expensive in the medium term due to early battery failure under cyclic load pattern.
This is the easy way and probably the best way if you only need to power your fridge through 50 nights or so, per year.
Initial cost: nil

2) moderately expensive taking into account the cost of isolation device and a new spiral wound battery: ~ 350 bucks.
3) same cost as 2) with the immediate advantage of higher capacity per Dollar (100Ah instead of 50Ah), drawback being faster battery deterioration which makes this option slightly more expensive than 2) in the medium term: ~ 350 bucks.
4) most expensive option with minimum room for things to go wrong (no isolation devices to play up, or creating spikes on the +12V supply line for ECU etc). But potentially cheaper than other options in the medium to long run: ~ 450 bucks.

Additional considerations:
temperature effect on batteries in your 200 series: should be relatively benign because the 200 series have the batteries mounted in front of the hot engine?
For other models like the 70 series which have the batteries mounted on the sides, the hot environment may make it slightly cheaper in the medium term to leave the flooded batteries in there and replace them whenever they die after 3 years or so, with another pair of flooded batteries. This life span can be shortened by frequent cyclic load pattern though, which may make it more economical to replace them with spiral wound AGM again.
If you're anxious to run out of cranking power if no isolator is in use, I recommend to take along a small 30~80W solar panel which replaces enough charge for cranking within 30 minutes of sunshine. Or, purchase another compact spiral wound AGM battery for backup (self discharge is basically a non issue with these) which you then use for jump starting.

Alternator voltage:
in a more recent development, the alternator voltage is controlled by the ECU.
This means the voltage will rise to 14.4 or higher for a short while after starting, and then drop off to as low as 13.3V for the rest of the journey.
If your alternator does that, it'll take quite a long time for the batteries to get recharged in a cyclic load application.
Countermeasures: on-bord DC/DC chargers, or solar panels/regulators wired in parallel to your batteries.

To start with, I recommend to get one of these sub 20 Dollars ciga lighter plug voltmeters so that you can observe the alternator output voltage when cruising along.
Once this voltage pattern is known, you can then make up your mind as to how to proceed with your battery setup.

Hope this hasn't become too long winded and confusing.
More info to be found in my profile, and the links in there.

Best regards, Peter

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Follow Up By: Member - Captain (WA) - Saturday, Jul 17, 2010 at 12:53

Saturday, Jul 17, 2010 at 12:53
Hi Peter,

I am going to get on my soap box now, so I will apologise for my rant upfront :( !!!!

First of all, far from all fridges have a low voltage cut-off. With Engel fridges accounting for around 50% of all fridge sales, they for one do NOT have a low-voltage cut-off. One model that does have a low voltage cut-off is Waeco, but the reason for this is to protect the rotary compressor, it has NOTHING to do with protecting the battery, that is just a side benefit. The Engels fridge, which uses a solenoid style compressor, can run on very low voltages hence why it does not have a low voltage cut-off!!! Additionally, the Waeco has a selection of voltage cut-offs and the lowest setting often does not allow a vehicle to start, especially a large capacity V8 diesel.

Secondly, why add a "$20 volt meter" when the cruiser already has one in the dash board!!!

Thirdly, the 200 series cruiser has a temperature compensated alternator, it lowers the charging voltage based on temperature, not state of charge of the battery. Once the engine bay is warm the 200 generally only charges at 13.1 - 13.5V, with variation mainly based on the ambient temperature affecting the underbonnet temp. While this does a great job of protecting wet cell batteries from over-charging, it also makes fully charging any battery a difficult proposition.

Now, as for your options I will make the following comments:
1. I agree that the existing batteries are not designed for deep discharge, they are starting batteries. but by the same token, any battery discharged to 20% SOC will suffer life issues. It is generally recommended not to exceed 50% SOC if you want long life from your batteries.

2. Why would you even recommend mixing AGM and wet cell batteries? They have different charging voltages and by simply commoning two types of batteries you are introducing problems. Also, why recommend a flat plate AGM under a bonnet? I know you alllude to why in 3. below, but why even recommend this as an option?

3. I agree that spiral wound are more suited to 4x4 use than flat plate AGM's, but the original problem of mixing wet cell and AGM's remain.

4. While replacing both batteries of the same type is good, you still talk of not using an isolator and then talk about considering a solar panel as a backup device, or carry around a 3rd battery!

Now, while there is some good factual information in your comment, there is also some misleading advice and lack of knowledge about the specific vehicle referred to.

Additionally, there is no discussion on the use of alternative wet cell batteries, just a straight jump to AGM's that IMHO do not offer the performace vs $$ factor. Or the fact that the Panasonic batteries supplied as standard in the 200 are an excellent battery in themselves and IMHO it is worthwhile getting some performance from them rather than simply junking them.

Normally I don't make such a negative post when an "ordinary" poster replies, but as you are a business advertiser and your logo implies a certain level of knowledge, I simply cannot sit back and see such misleading advice be given, abeit mixed up with some good advice!

Now, there are many ways to skin a cat and I advise the original poster to read widely on this subject, it is one that has many differing views and causes some of the most endearing discussions on this forum. The hard part is to seperate the wheat from the chaff, especially when you are not a farmer!!!

I appreciate you put in the time to respond, but then so do all other posters and we have zero vested interest either! Once you imply a certain level of authorative knowledge, as done by your logo, you need to be 110% correct!!!


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Follow Up By: Battery Value Pty Ltd - Saturday, Jul 17, 2010 at 13:21

Saturday, Jul 17, 2010 at 13:21
Hello Captain,

thank you for the additional information and your view of things.

Knowledge evolves, so it's only a matter of time to be 110% correct - are you there yet? ;)

Best regards, Peter

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Follow Up By: Battery Value Pty Ltd - Saturday, Jul 17, 2010 at 14:55

Saturday, Jul 17, 2010 at 14:55
@ Willharry,

thanks to Captain's car specific knowledge, I can give you the following summary:

Charging voltages:
13.1 to 13.5V represents a problem for cyclic battery charging.
These voltages are only suitable for float charging (just) a battery which never sees any serious discharge beyond a few Ah.

If you decide to ignore this, the battery/ies will have their specified cycle life severely reduced due to negative plate sulphation.

1) You might try and find ways to keep your alternator from dropping the voltage that low.
This may be as simple as swapping the alternator/regulator with a constant 13.8V device, or an external/adjustable unit.
Again, my apologies for not knowing the vehicle specifics - anyone?

If that avenue is not for you, then:
2) Installing a solar panel plus multi stage solar regulator, to fully boost charge your deep cycle batteries while stationary, or even on the go.
If both your cranker and auxiliary batteries are of the spiral wound AGM type, then you don't need an isolation device between the two batteries.

3) have your auxiliary battery isolated from the cranker at all times, and charge your auxiliary by a DC/DC charger during cruising.

Pros and cons:
1) may be the cheapest way to achieve a half decent state of charge in your deep cycle batteries.
2) a very precise way of charging your batteries if the solar regulator is configurable to your type of batteries.
The solar regulator also has battery protection built in, such as low voltage cutout, and some offer battery temperature sensing.
Care should be taken, when selecting the regulator, as most of them are 'common positive'. Especially with the Engel's it's highly advisable to use 'common negative' regulators.
3) the main drawback of the DC/DC option is, there is no charge going into your batteries while stationary, plus these units tend to be pricey.

My choice would be:
Two identical batteries, for the cranker and the auxiliary - namely spiral wound AGM with their cranking and additional deep cycle capability.
This gives you 100Ah of deep cycle capacity, more than enough for most load situations, especially when augmented by properly tuned solar power. Isolation switch not required. That's because in the unlikely case the solar controller won't disconnect your loads in time, you've got your solar panel to put enough cranking juice back within minutes of sunshine.

If you only anticipate loads of less than say 20Ah before starting your 4WD, leave the existing wet cells in there, and add the solar option.
Again, no isolation device necessary, as the solar controller takes care of preserving the charge required for cranking.
As said earlier, select B&S 0 or 1 for the connection between cranking and auxiliary batteries.

Any questions, pls let us know.

Best regards, Peter

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Reply By: Member - John Baas (WA) - Friday, Jul 16, 2010 at 22:38

Friday, Jul 16, 2010 at 22:38
There's a good number of threads on this on this site and on the LCOOL site ( Use the search facility.

Whatever you do, don't get a third battery set-up like mine which was installed under the rear wheel arch. The location is very difficult to access and battery protection is also difficult.

AnswerID: 424272

Reply By: CJ - Saturday, Jul 17, 2010 at 14:34

Saturday, Jul 17, 2010 at 14:34
Peter from Battery Value, I disagree totally with your advice

Firstly the 200 already has two batties in parralel.
Secondly, a fridge low volrage cutout does NOT leave enough to crank the car, specially on a cold morning and with OTHER draws like lights attached.

Willharry7, There are a number of options. The simplest is to split your two batteries with a solanoid (Redarc or another reputable brand) You can replace the crancker with a higher rated battery, and replace the Aux with a higher Ahr. This way you will always be able to start your car.

The single cranker is enough to start the car every time.

Then there are more options which will cost more money, this simple option is used by many and are worry free.

Personally I'd put a 100+Ahr AGM battery as Aux. They charge much faster.

AnswerID: 424314

Follow Up By: Willharry7 - Saturday, Jul 17, 2010 at 16:27

Saturday, Jul 17, 2010 at 16:27
Thanks CJ.

So to confirm are you suggesting the simplest way to go is to replace both the original batteries and split with a solanoid?
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Follow Up By: Member - Graham H (QLD) - Saturday, Jul 17, 2010 at 16:40

Saturday, Jul 17, 2010 at 16:40
As in a 100 ser Buy a Redarc split the batteries put in two 65cca N70ZZ or similar.

I have two Yaesu Hybrids in mine. Have had for 2 years. Cranker is down about 35cca and Aux is down 10 when I had them checked last week at Battery world.

Have had a 60lt Waeco running most days in car for last 12 months.

Whole lot cost $650 all installed by myself. Two batteries were just under $275 each and Redarc was about $115 from Derek who advertises on here.

Had some wire and got Battery World to crimp ends on for me.

Half a days work.

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Follow Up By: CJ - Saturday, Jul 17, 2010 at 17:35

Saturday, Jul 17, 2010 at 17:35

Yes that is my suggestion. The beaut of this simplistic system is that you can actually split the batteries only, or do it with one new battery or both batteries depending on your budget and time. For example if you are only planning a weekend away in the next few months with a big trip in 12 months, you can split them now so you have peace of mind on your weekends away;; It will see you through your weekends and you can use the original batteries for a while. Then replace the batteries before your big trip

Ultimately you will need to replace the Aux with a more suitable battery like an AGM, at that time I would replace the cracker as well. There are many clever people (who's opinions I respect) who suggest that the batteries need to be the same and that the car's alternator is not the best way to charge the AGM's. But when you interrogate their thoughts, it comes back into perspective; yes with a DC-DC charger you will provide the optimal charge to the AGM, BUT the straight alternator charge is not that bad! it is like comparing a Mercedes solution to a BMW solution, one may be better but both are very good!

In fact I am told that with a discharged battery you can actually charge it faster to 85% straight from the alternator than trough a DC-DC.

SO as far as charging, the alternator does a very good job
So as for same batteries, similar sized batteries provide a very good match.

I suggest to put the biggest CCA battery that fits into the existing space (N70) as cracker (650CCA+) and the biggest Amp-hour AGM (approx 105AH) as Aux.

You can do a lot more, but with marginal gain in charging time and battery life


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Reply By: Member - Captain (WA) - Saturday, Jul 17, 2010 at 21:24

Saturday, Jul 17, 2010 at 21:24
Hi Willharry7,

There are many ways to set up a battery management system in a 200, but there is no "best" way! It all depends on what you want to do with your vehicle and how much money you want to spend. I will describe what I have done to my vehicle and why, but it doesn't mean its the "best" thing to do.

As the 200 comes with 2 quality batteries, abeit NZ50 size, there is no real need to junk 2 otherwise good batteries. I iniially split my batteries with a redarc isolator. here is a pic of it installed, just behind the aircleaner and uses origonal captive nuts already present (I hate drilling holes in a new vehicle if I can avoid it).

Now this results in the 200 cranking on one battery (passenger side) and the other is your auxillary battery, so connect any accessories to that battery.

Now this so far has cost around $150 for an isolator and cables, you have a single 550A cranking battery and a starting battery as your aux. Experience by many people (LCOOL forum) has proven that the 200 will crank on a single OEM battery unless well below 0C. If you use the original battery as an aux and only have a light load (say then this will be fine for some time, particularly if you drive long distances. The reason for long distance driving is to give the battery a good charge due to the alternator characterisitics.

Now while the above works well, when cranking the 200 on a single battery, the votage drops low enough for my radio to lose its station settings (I have an aftermarket replacmement radio with GPS etc...). So I replaced my starting battery with a wet cell ~750CCA and this works very well for me. I did not use AGM's as their is no cost benefit IMHO and the high underbonnet temps is not an ideal place for them. I do use AGM's in my van, I am not against AGM's but only use them where I feel they are suited.

Now, your vehicle starting needs are well taken care of by spending another ~$200 for a quality starting battery, but you still have the OEM battery for the aux - plus a spare OEM one from the starting side to replace it in ~6 months to 18 months depending on things like how much load and how often you drain it down.

If you only run a single fridge for 24-48 hrs before driving, then the above setup should work well. However, I run two Engels, one as a freezer, and I would not get 24 hours before the aux battery was way too low for any sort of decent life. So I replaced it with a wet cell hybrid battery. By Hybrid, I mean one designed to give some deep cycle action, but also be able to be used safely as a cranking battery. They are a jack of all trades, master of none type but suit me best due to my needs. As I have a winch, I need something able to give high amps as well as be able to run two Engels and also be able to be used as a starting battery. While AGM's are a good candidate here, I would not advise mixing battery types and still do not believe in the $$ vs benefit of AGM's under the bonnet (many will disagree about this, but this is my opinion).

Now my above setup works well for me and my needs, but is doesn't mean its right for everyone. I also have 2 AGM's in my van that can be commoned with my vehicle aux to provide close to of battery capacity. Also, I am aware of the compromises and limitiations of my system and have chosen what i believe is the best cost effective solution for me.

One could use AGM's, install DC-DC chargers and spend a small fortune and have a "technically" better solution, but in practise there will be marginal difference and it won't be as capable as charging back to 80-90% SOC as quick as an alternator only solution.

So, for most people with a 200 (this can apply to many other vehicles, but I am specifically talking for a 200 here ) with only the need to run a fridge for a day or so, the most cost effective solution IMHO is to spend ~$150 and isolate the original batteries. As your needs increase, spend the $$$ and get more battery capacity as you require. As for the need to replace the alternator or install solar panels (where?) to charge the battery while driving, well its up to you on what you want to do with your vehicle.


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Follow Up By: LeighW - Wednesday, Jul 28, 2010 at 14:01

Wednesday, Jul 28, 2010 at 14:01
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Reply By: LeighW - Wednesday, Jul 28, 2010 at 14:02

Wednesday, Jul 28, 2010 at 14:02
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Reply By: Maîneÿ . . .- Wednesday, Jul 28, 2010 at 14:58

Wednesday, Jul 28, 2010 at 14:58
From what I read on here, I understand the 200 series is happy to start on just one cranking battery.

Therefore, the 2nd battery is not (maybe never) required for cranking, so the economical way is to just fit a battery isolator between the 2 batteries and run the fridge off the 2nd battery.

When the 2nd battery dies prematurely, as it will, replace it with an AGM Deep Cycle battery.

Even if the Cranker gets tired one cold day you can then use the AGM as an assisance cranking battery till you replace the original 200 series cranking battery by just bypassing the battery isolator with a (small) jumper lead as I used to do before I installed the manual 140 Amp bypass switch in-line.
Image Could Not Be FoundMaîneÿ . . .
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