Battery Setups and Needs

Hi Guys,

Have been looking into the whole dual battery setup stuff on here and have noticed some are even adding in a third battery. I guess what im getting at is how much electrical gear is needed to have 3 batteries?

Ideally i would like to have my D22 setup with a hard canopy (fridge in the back and camping stuff) and eventually have a camper trailer with a battery in there. Lucky enough to already have dual battery as stock, however was thinking about removing one under the hood (replacing the 2 stock batteries with 1 optima, also creating more space in the engine bay for catch can, etc) and placing one in the tub. Would the stock charging system thats already inplace be enough to charge the batt in the tub tray since it has already been charging 2 batteries?

Thanks Guys

It depends what your existing charging system is for the fridge battery?

My view is if you have additional batteries then a DC to DC charger is a essential. It provides isolation between the two batteries, it compensates for the voltage drop for the additional long charge feed wire and it also allows batteries with different chemistries to operate together. You could have Calcium in the engine and AGM in the back with these chargers. Just bridging them together is not a great idea.

In general batteries for fridges etc allow deep discharge cycles compared with start batteries. The Cold Cranking Amps (CCA) is important also if you want to be able to jumper the fridge battery across to emergency start the engine. The better fridge batteries often have low CCA's and small battery poles. I try to find a fridge battery with a standard size battery pole with reasonable CCA. It will allow a degree of deep cycling but also be able to start the vehicle in an emergency. (Ever tried to push start an auto diesel?)

With a single 100AH fridge battery you would be struggling a bit. The battery will deep cycle each night and its life will be reduced. With two fridge batteries (say 200AH total) they do not discharge as much during the night so the batteries will last much longer compared with a single battery.

The main advantage of AGM is it's ability to charge rapidly. This is desireable if you need to charge from a generator. A couple of hours of generator running is better than several hours it would take with a conventional battery.

JLA's on the money here.

You CAN spent gobs of money and buy something like an Optima D31A spiral-wound AGM deep cycle battery. Not as many amp hours as you'd get with a standard AGM, but 900CCA means you can drag it around the front, jumper it to your cranker and get going again. It's my current choice of doing it - but I want to change, so don't follow just yet!

My Optima is starting to get on in years now, so I am starting to plan for its replacement. Since we live about 50km from a shopping centre, we have two fridges in our ute, and a 130W solar panel + MPPT controller to maintain it, plus a 12V input from the car with inverter + 240V mains charger. It's a little messy but necessary so that in the middle of summer, we can get perishable stuff home intact.

I've found that 130W doesn't charge things fast enough, especially if both fridges are running. We're going to get a 200W panel (moving the 130W to the caravan, where it's not really needed but will be a nice addition). The battery will be replaced by a LiFePO4 unit - something like this one - but as you can see, they're stupidly expensive.

There are a couple of big differences with LiFePO4 and lead acid. LiFePO4 lets you discharge the battery further, so you have more usable capacity. LiFePO4 is lighter - the battery I linked to is 200Ah and 33Kg, my current 75Ah battery is 38Kg. AGM is supposed to last 5-7 years with around 1,000 discharge cycles. LiFePO4 is supposed to last upwards of 10 years, with up to 5,000 discharge cycles.

So that's where I'll be going. LiFePO4 seems like a bigger investment up front, but with reduced weight, greater capacity and less danger, LiFePO4 is a good option. There are cheaper units than the one I linked to - that was one of the first high capacity units that I found on eBay.

There's another upcoming technology that is going to do 2 things. The new battery type that's on its way will cause a reduction in price of the LiFePO4 (which is a stable, tried and tested tech now, so you can rely on it), but the new tech is supposed to have 5 times the power (can't remember where I saw this or what it's called yet, but then it's new so whaddayaspect?). There are other techs (lithium air, magnesium and more) on their way - no idea how reliable any of it will be for mobile use, but any other advances will make the older stuff cheaper and that's not a bad thing!

gez tony, it would be cheaper to run a power lead behind you to a power point! that battery seems unbelievably expensive.

Some big vans and motorhomes have up to 6 of them Bever, the price of Lithium is actually coming down. Bloody expensive though as you say.

18 months ago I did some work for a top end caravan manufacturer. They offered Lithium upgrades to their existing customers for about $5,000. This included a couple of lithium batteries (can't remember capacity) and a lithium battery management system which included DC-DC as well as 240-DC. In five years, for those using Lithium there has never been a failure. AGM's can fall over in two years depending on how deeply they are discharged etc.

The normal charger Flood/Calcium/Gel/AGM etc is no good for lithium on any of those settings - needs a specialised lithium charger. Perhaps by now there are reasonable chargers that offer the full ranges of chemistries including lithium?

10 years of trouble free reliable service does seem likely with Lithium. One possible issue is parking the van with no solar and no 240 charger in a dark garage for 12 months or so. Slow discharge from monitoring devices etc. means the battery eventually discharges. No problems, the battery does not care too much but it then begins to take on a reverse polarity. This can build up to a level where reverse polarity damage is possible to the charging system etc. Solutions to this are: Get a skylight so the solar works; plug charger into 240v; or simply add an isolating switch so all load is removed from the battery, then it will not go flat.

There's supposed to be at least one brand of LiFePO4 battery that has circuitry built in to allow it to operate as a replacement in a system set up for lead acid batteries. Not sure if I'd want to go that way - it means the circuitry has to fool a battery charger designed to handle a battery that indicates its state of charge by the surface voltage present.

While that's convenient, it does introduce a layer of componentry that creates a potential failure point. Just something more to consider!

I've heard about the Lithium "drop ins", but wondered how good they really were. 'Compatible' lithiums have been available for a couple of years and in the past there were many warnings about
'don't do it". I have not heard how well the current ones perform, perhaps they work OK?
For me lithium is still in development, so I'll wait a while yet until they become mainstream.

There are a ton of new alternatives out there. Seems like the dotcom bubble has moved to the battery industry.

It's about time. I heard someone (a few years ago now) say that if batteries had developed at the same pace as computers since inception, the humble AA battery would hold the energy equivalent of the nuke they dropped on Hiroshima. That might be an exaggeration, but when I was racing RC cars and looking at 2000mAh cells being the latest and greatest but too unstable so we all went with 1700mAh cells, and looking back at how old the tech was, you'd find it hard to argue with the Hiroshima argument.

Seems some extraordinary claims coming for the car industry too. Saw one that said on a single charge, their electric car could do 1100km ... almost as much as my Navara! Can it tow?

I have been looking at Lead Crystal batteries which is just a specialised AGM battery.
18 year service life
Fast charge, two or three times faster than flood. Probably faster than any other AGM battery.
100A/H is around $500 to $600.
A daily discharge down to 20% charge = good for 1,600 cycles (big advantage)
A daily discharge down to 80% = you get 6,000 charge cycles.
Seems to be OK with any AGM charger, does not need new battery management. There are "certified" Lead Crystal chargers around, but they seem to be describing AGM.
Can store for two years without charge top up.
Classed as non-hazardous for transport.
Been available for 5 years.

The depth of discharge with this type of AGM is a big advantage. If you discharge it down to only 20% left and recharge every day then it will last about 4.5 years. That is huge. Same thing but only down to 80% every day it will last 16.5 years. For the average camper with a small amount of care anyone can make this battery last the 18 years.

The fact that you can discharge down to 20% means you can get say two or three times the capacity out of these batteries compared to standard AGM.

There are some YouTube videos where they totally flatten a Lead Crystal battery and then charge it again. After six months there was no particular loss of performance.

The maximum charge current is high probably higher than your charger can deliver. This is never a problem, the battery will take a bit longer to charge if the charger cannot match what the battery can take. It does mean that generator charging will take a shorter time.

I think we will see more about these chargers. Like at AGM, it won't won't run straight off the alternator but will through a DC to DC charger.

If you use 2 x 100A/H batteries you may get away with just one 100A/H of the Lead Crystal because you can discharge it much further and probably get double the energy ?