The 150 series Dual Battery Guide

[derekclapham Junior Member Find all posts View Profile Close derekclapham]

All new lead acid batteries, including all forms of AGMs will now safely tolerate being discharged down to 11.58v or 20% and a number can be discharged down to 10.5v or 0%

@drivesafe are you saying that the "Don't discharge beyond 50%" (or 12.2v) is no longer applicable with new AGMs? If so, what kind of specs would one look for when buying a new AGM? I typically buy Fullriver.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi again Craig and thanks for the link.

It just demonstrates the lengths “sellers” will go to, to get sales.


Hi Derek and the “Don’t discharge beyond 50%” would be for a use specific requirement and to be honest, I have no idea as to what field that would be a requirement.

If you were living permanently off-grid and using your batteries as your main power supply, then depending on the brand, they should not be cycled below 65%

The 50% does NOT apply to RV use and it is quite safe to cycle RV batteries to 20% and still get a very good life span from the batteries.

BTW Fullriver is one of the better AGM batteries and their web site is a wealth of info.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

Pointing to various technologies in not succeeding in the Auto world, is not a satisfactory. Its an Ostrich's argument.

The fact is that Lithium is cheaper over the long term that AGM. The main downside of Lithium is that if it fails before its financial break even point with AGM, then you've done your money. Although you have saved weight and been able to discharge and re-charge quicker. But its the financial risk that scares most.

It scared Toyota with their hybrid cars, which had lead acid. Evidently the latest ones now get - Lithium (the latest Lexus SUV built on the RAV platform) is said to have Lithium recovery architecture. but the petrol starter is still lead acid - because Toyota can't don't want owners to have over warranty starter batteries, they'd rather save the money.

All the lead acid manufacturers provide data that shows their products have much less re-charge lives if you go below 50%. And the higher the CCA v AH levels, the worse such batteries are effected.

Lead acid also has major sulphation issues.

The thickness of their lead results in them charging slower and having less CCA amounts. But such batteries - with thicker plates - last much longer.

I have two Optima yellows and they have high CCAs and take charge quickly. This means they have a high percentage of thinner lead. it may be wound but physics is physics.

Lead Acid is also more sensitive to heat.

Lithium is a much better metal to use than lead. Its a super light metal, while lead is a very heavy metal. So its great for transport.

Lithium does not suffer from sulphating issues.

Balancing of charge was an issue - but its now a known technology, and all the time, balancing tech is getting cheaper. Many Lithiums have it standard. And people can buy lithium cells, and put on their own purchased balancing systems. That's what Kimberly would be doing. By doing so, they sell heaps of Lithiums, that are quite cheap to buy direct from China. They add the technology and they make a good profit. Plu

Lithium is standard on but one Karavan and all the Kruisers now (yes three single axle Kruisers have been announced), and an option on the flip tops canvas trailers. Kimberly say that the future need of off road power, will be over 800 AH capacity, as their customers lust for more luxury.

A lead acid at 30Kg for 80 AH (much better than an Optima can achieve) means that for 800 AH you'd need 300 kg. But you'd in fact, due to the depth of cycle issue, you need more like 500 kg of lead acid. Imagine that in severe off road conditions.

If you want lots of power and mobility - the choice is really Lithium, supplemented by solar and importantly a generator.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi MP and again, you are making it up half of your post as you go along.

CCA and Ah are totally unrelated and if your theory was correct, then Optima batteries would be the worst battery on the market, instead of being what they are, one of the best.

Next, sulfation is only a problem if someone discharges a battery and leaves it that way.

If you discharge a battery over a weekend away and then charge either on the way home or when you get home, there will so little sulfation take place in that short time that the charging will completely reverse the sulfation.

And if a battery is at 75% SoC or higher, no sulfation occurs in the first place.

Now back to the use of Lithium batteries in the RV field.

While many makes of lithium batteries can be charged by an alternator while driving, while this is ideal for lead acid batteries, this is anything but idea ideal for lithium batteries.

For instance, 14.7v is the optimum charging voltage for most new Standby type AGMs, but you can fully charge AGMs with as little as 13.0v. In fact Fullriver have a graph on their web site that shows the time required to fully charge one of their batteries, using different voltage levels.

And while it would take 30 hours to fully charge a low AGM battery, it would still be fully charged.

The same applies to wet cell batteries and the reality is that most will be charged with at least 13.8v ( and better with one of LeighW’s fuses ).

The difference is that the closer you get to a lead acid battery’s OPTIMUM charge voltage the short the time required to fully charge them.

This is not so with a Lithium battery. The OPTIMUM charge voltage is 14.6v. But just lower the charge voltage to 14.4v and no matter how long you keep that voltage applied, a lithium battery being charged with 14.4v will only reach a 95% charged capacity.

The lower the charge voltage applied to a lithium battery, the lower the capacity you get.

So you are not only up for the higher cost of lithium batteries but you have to add the cost of the special charger needed to get the maximum out of lithium batteries. Something not needed to get the maximum out of lead acid batteries.

Now to another bit of misinformation.

That is the reduced life span caused by discharging a lead acid battery down to 20% SoC.

This one is used regularly to try to “scare” people into thinking there lead acid battery is going to have a short life span if you cycle it down to 20% like you can safely do with a lithium battery.

The theory is correct but people using this argument, always neglect to give the full story.

Fullriver state that their batteries will only get 750 cycles down to 20% SoC but will get 1,250 cycles to 50% SoC.

The reality is that Fullriver are one of the better quality batteries, but I’ll halve their cycle rates so as to better represent a larger cross section of batteries being used by RVers.

So lets say we only get 300 cycles down to 20% SoC when we use battery Brand X.

So if we go out every weekend, and every weekend, we cycle the battery down to 20% SoC. This would only give us an expected life span of 6 years, as long as we look after the battery in all other aspects.

I don’t know about the rest of you, but 6 years from a battery being used like that is pretty good.

Now lets look at a more realistic use and say the battery is used one weekend a month, but is still cycled down to 20% SoC and you now have a “SHORTENED” life expectancy of 24 years.

As we all know, a battery is going to die of natural causes way, WAY before that and way before the 20% cycle rate has any effect of the battery’s real life span.

MP, try putting up all the details, and not just the bits that best suit your argument.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

I think you made some good points drivesafe, the main one being that we all need to analyse our bottlenecks and also our requirements. That why batteries can be confusing - we can all have different set ups and as long as we are aware of the issues that effect us, they'll all work OK, with the odd lesson along the way. Whatever battery setup we have IMO our bottom line should be to ensure that we can always start our Prado's motor.

Its ironic drivesafe that you have a go about not putting up points, when you leave things out yourself! I guess that is the fun of this great site! For instance the heat and ampage limitations that for Optima specifically apply to their batteries. You know - their "if over 10 amps them monitor the temperature".

And while you criticise Lithium for 95% charge issues, you neglected to point out that 95% state of charge with a lithium doesn't hurt them, and that 95% still still allows much greater capacity. And not to mention that Lithium's almost flat power curve compared to lead acid's constant drop off. Something that further pushes Lithium's usable power advantage.

And with a lead acid, when you don't fully charge them, they loose their capacity because sulphication effects the non re-charged areas. Not fully charging Lithium doesn't damage them nearly as much - only due to more cycling from a 95% level rather than 100%.

Notice to those of us with costly batteries like my Ultimas: don't think that the battery will get fully charged from short drives. It is best for such battery owners to invest in a 240v smart charger - they provide much longer battery life, because they get the battery fully charged. Drivesafe - IMO you don't agree with that, but its accepted by most IMO including LeighW.

I do agree with your overall point though drivesafe - I interpreted that for the casual 4WD'er you'd go for a lead acid. For me if prices continue to drop, one day I'll go Lithium. I wish they came standard from the factory. And if not, then why not at least a deep cycling capable battery in our brand new Prado's? Or at least the option of one?

Applying your argument about battery life and the 300 cycles - for the front weight sensitive Prado: Save the weight, avoid heavier per Amp hour AGMs, and go for a flooded marine style deep cycle capable battery. Or a rugged flooded. They are cheaper than AGM, more heat tolerant, provide more amps per kg and their main downside is that they recharge slower. That last point is the confusing one IMO. And if marine, check its warranty - as some are not warrantied if under the bonnet. Check the length and weight if its in the Prado's front spare spot - over 260mm and their length effects the air conditioning pipe which is in close proximity.

As far as campers who travel a lot and want lots of power, weight becomes a real issue, especially to us Prado users, either towing or just doing it all out of our Prados. Kit out a Prado with a few people and its easy to go over our weight restrictions (and we can only pull 2.5 tonne in most Prados but a GXL or GX can be upgraded to 3 tonne for $3k). So if we have a big electric power requirement the game changes - light weight becomes increasingly important. That's why more and more off road setups like Kimberley's ones are appearing with air con, then Lithium wins there, despite the cost, which is a big reason why most Kimberly non canvas pop ups now ship with Lithium.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

I picked two batteries that are designed for car applications and readily available: Optima maximum charge current = No current limit as long as battery temperature remains below 52C approx, 30 minutes to charge to 90% SOC at 100A charge current. Fusion max recharge 40A, normal recharge 20A. Optima operating temperature say 52C for above reason. Fusion 60C. Max discharge 830 amps Fusion used to state 100 amps from memory but now they don't seem to list it, not much good for winching. A quote from someone in the industry regarding Lithium: I notice the 3 warranty period for the Fusion, this seems very low to me when the battery has qualities that far exceed normal wet/agm type batts and many of them have 3 year warranties. As for Kimberly, their customers want 12V air conditioning, judging from the chassis failures they are having I not surprised they are opting for light weight batteries. Will Lithium take over, if the price comes down and reliability is proven maybe, but then again their already talking about different chemistries that will supposedly make Lithium obsolete.

[InnerCityBoy Junior Member Find all posts View Profile Close InnerCityBoy]

Hi - first post from a new Prado owner. This thread seems pretty hard-core, but I couldn't find another thread for newbie questions so apologies if this is the wrong place.

Am planning to install a second battery in the future (into my camper trailer, not actually in the Prado) but am not yet ready to take the plunge with isolater switches, Anderson plugs and pulling the trim apart just yet.

For the time being, and for the sake of having something in place for some camping over Christmas, is there any reason I can't just hook up a second battery (which is in a battery box) to the 12v power running in to the trailer via the tow connection? I get this probably won't deliver rapid charge, but it would seem to be a relatively fool-proof option. After all, it can't drain the starter battery (as long as I don't have acc on) and I'm assuming the second 12v battery would be unlikely to pull a current that the standard trailer wiring couldn't handle. The trailer already has a cigarette lighter socket installed so I think in can handle putting together a simple cable with a fuse for good measure.

BTW although this thread is hard going for non-auto electricians like me , I've picked up a lot of great advice and have a good sense already as to what my eventual solution will be.

Thanks - Sim

[Prone Member Find all posts View Profile Close Prone]

It scared Toyota with their hybrid cars, which had lead acid. Evidently the latest ones now get - Lithium (the latest Lexus SUV built on the RAV platform) is said to have Lithium recovery architecture. but the petrol starter is still lead acid - because Toyota can't don't want owners to have over warranty starter batteries, they'd rather save the money.

The Toyota Hybrids (Prius at least) have used nickel metal hydride (NiMH) batteries for the traction supply to date. 200+ 6.5AH cells in series to make 200+ volts, the final voltage and cell count depending on the model. The original Japanese model was reputed to have used NiMH "D" cells to make up the battery! The small 12 Volt auxiliary battery has been lead acid.

The computer control is very aggressive in not letting the capacity drop too low. (But it can be a fun task driving to see how low you can get it.) Later models are even more aggressive at protecting the battery. This is my opinion based on 3 vehicles in the fleet where I used to work.

I note that the possibility of Lithium Ion types in up coming variants and some European models, in particular the "plug in" models.

Cheers
Prone

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

I'm assuming the second 12v battery would be unlikely to pull a current that the standard trailer wiring couldn't handle.

Thanks - Sim

A heavily discharged lead acid battery will pull 60 amps plus, it is quite possible it will
blow the fuse protecting the trailer wiring assuming it is around 15A and not designed
for battery charging.

Cheers
Leigh

[InnerCityBoy Junior Member Find all posts View Profile Close InnerCityBoy]

OK sounds like a non-starter ... thanks for the guidance Leigh.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

Thanks Prone.

I've read articles about why the auxiliary battery is led acid. The answer is cost! Its the starting battery for the petrol motor, its main power drain i think.

I test drove the latest (here in Australia at least) NX hybrid SUV by Lexus, based on the RAV floopan. Toyota claim its hybrid batteries are Lithium now. I read too that I think Hyundai hybrid came with Lithium.

Strangely though IMO if the energy recovering system was 100% efficient, I'd argue that low weight was a lower priority for such vehicles. While with conventional vehicles, and camper trailers especially with high power needs (and where low weight is a big benefit for going further off road) Lithium is a big advantage.

[MelbournePark Member Find all posts View Profile Close MelbournePark]

I picked two batteries that are designed for car ....

Optima's typical yellow and blue top specs are:
" Alternator: 13.65 to 15.0 volts
Battery Charger (Constant Voltage): 13.8 to 15.0 volts; 10 amps maximum; 6-12 hours approximate
Float Charge: 13.2 to 13.8 volts; 1 amp maximum; (indefinite time at lower voltages)
Rapid Recharge: Maximum voltage 15.6 volts. No current limit as long as battery
(Constant voltage charger) temperature remains below 125°F (51.7°C). Charge until
current drops below 1 amp.
Cyclic or Series String Applications: 14.7 volts. No current limit as long as battery temperature
remains below 125°F (51.7°C). When current falls below 1 amp,
finish with 3 amp constant current for 1 hour.
All limits must be strictly adhered to. "

If you want to continue pushing the Optima brand, then why not show us a link which reveals their discharge characteristics?
My Optimas seem OK, but their most powerful feature is their huge marketing and distribution program.

With Lithium, IMO they upset battery sellers, because the conventional battery distribution chains have been controlled by lead acid manufacturers. With Lithium, this is much less that case. Conventional (ie lead acid wet, flooded, AGM And Gel) sellers in all their niches, have less access to Lithium and if one goes back a couple of years you on PradoPoint you see battery sellers querying where they can find Lithiums. This situation has found companies sourcing cells from China and doing the electronics themselves, some in Australia. Its no wonder the warranties vary enormously for them.

.... As for Kimberly, their customers want 12V air conditioning, judging from the chassis failures they are having I not surprised they are opting for light weight batteries. Will Lithium take over, if the price comes down and reliability is proven maybe, but then again their already talking about different chemistries that will supposedly make Lithium obsolete.

This is a battery thread, and I think to make claims about Kimberly having chassis failures requires a statistical basis and either editing or substantiation. They are a popular quality product IMO that has been going for years and they even export.

And while Kimberly customers may want 12v air conditioning, all "luxury" campers all do!

However, Kimberly don't supply 12v air conditioning. They did, for a short period, mostly 2012. Now, Kimberly use 240v Air Cons. They use the batteries as a supplement for the starting of the air con's compressor's high amp starting kick - mostly via a decent inverter which draws from their batteries (which converts 12v to 240v). They call this I think their "hybrid system". They've even registered the name ... the hybrid includes: significant battery back-up; significant solar back-up; and using a portable generator.

The 12v unit would run down about 200 AH in around 6 hours I am told by someone who knows. The unit was 0.9 power draw compared to the current 240v 2.2. With heat pumps, power draw doesn't always indicate BTU issues, but its said that the 12 volt unit made it much more comfortable, but hardly cold. Unlike the latest tech, which really requires a small portable generator to run for a couple of hours per day to keep even their top line systems cool in the bush.

With the attacks on much of that industry from the Chinese importers; the amount of claimed Aussie made trailers companies bleeding; all mostly due to Chinese stuff being assembled here; that is far from Australian manufacturing standards IMO; I don't understand why attacking an Australian manufacturer in a battery thread is necessary.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Now now MelbournePark, you made some claims regarding Lithiums can be recharged faster than lead acid, I just provided manufactures specs for an Optima and a Fusion Lithium which clearly showed the Optima will recharge faster and that Fusion recommended recharge rates of 20 amps. A Marine Pro would recharge much faster than the Fusion battery at the recommend 20 amp rate and have a similar recharge times as the Fusion battery when it is charged at it's not recommended maximum rate of 40 amps.

You also made claims that all Lithiums can provide huge discharge currents, yet fusion only recommended (from memory as I can't find it listed now) maximum discharge rates of 100 amps, clearly it would seem is not designed for high discharge rates.

Yes I have seen Lithium starting batteries and of course lead acid starting batteries, and yes some AGM's should only be discharged at maximums of 20 amps and I see fusion also specify 100AH capacity at a nominal 20 amp rate.

As for pushing Optima, I said at the start I believe the Marine Pros offer best bang for buck.

The Kimberly Karavan is well known for having chassis cracking issues a shocker failures which would appear to be directly attributed to the units weight. In my opinion one of the driving reasons Kimberly would have chosen to use Lithium batteries would have been the weight reduction the offer. Also fitting temperature tell tales to the shockers and then saying if they overheat it the owners responsibility is a bit of a cope out in my opinion from a company that advertises our units can go anywhere your car can, clearly from the number of failures occurring this is not the case, mind you there may be a few other companies pondering rewording their advertising after some recent court cases.

If Lithiums are still around in 10 years time and the price comes down I will look at them myself though I suspect that I'll be having similar discussions with someone regarding a different battery chemistry or fuel cells by then.

As for Aussie made trailer companies bleeding, well maybe they need to look at their act, the company I brought my camper from is thriving, they offer a quality made product which is not cheap but people are prepared to pay extra for a good quality well made unit that is not going to give them any trouble.

[Momo Lurker Find all posts View Profile Close Momo]

Ive been following this very interesting and informative thread. It appears there are a few viable options for dual battery set up. I dont think i need a full-time DB set up in the truck but might be stuck with one anyway unless someone has a good suggestion? ..

Want to run a fridge in the back of the truck that i can take out as would really only use it when camping. (dont have the fridge yet). I tow a CT and have a larger marine battery in that (have to check the specs on it, been a while). I charge it from mains power at home and just basically run lights and charge phones etc in camp. Wife is getting some ideas re: coffee machine and a few other luxuries so will likely run an inverter.

Should i bite the bullet and put in a second in-car battery or can i get away with a system to charge the portable in-box battery that i can move to the back of the car if i just want to run the fridge when not towing? Your learned opinions much appreciated.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Really hard to say, depends on how you use it and for how long.

A fridge will draw around 2 - 4 Ah per hour down south on mild days, if you
run it as a freezer maybe double that on hot days, so if you have a 100 AH battery in back
of car, only discharge it to 50% SOC you'll get around 25 hours at 2 Ah average draw, if you go to 80% then 40 hours. With my setup, a marine pro and waeco 40 Ltr running as a freezer, if I pull up around 3PM I can camp for around two days without having to move and not using solar when heading north from April on ie mild days and cool nights.

80Ltr Fridge/freezer in van on the other hand draws 6 amps, and has a 40% on 60% of duty cycle ambient 30C. So van is fitted with two 100Ah AGM's.

You need to get the fridge and do some current measurements you'll than be able to work
out how long your going to get out of your battery.

If your talking coffee machine as in a proper stem heat unit your looking at big wattage's,
my little Krups pulls 1200W, that's over a 100 amps from your battery when running, even if only for 10 minutes operation that's a big hit on a 100 Ah battery.