Thread: lithium dual battery ideas

Tim from Traxxide is really knowledgeable in this area and knows the D4 quite well

Interested to see how you go,i have the same issue,and have been thinking what to do.

Different brand vehicle,no smart alternator,with Traxide DT 90,lucky to get two days,usually 1 1/2, out of fully charged batteries,the Aux is 105AH,AGM,which fits under bonnet.

Both the start and Aux are almost 3 yrs old and tired,and i charge them up separately at least once a month,often twice a month,overnight,but still only lasted 3 yrs.

I can fit a Lithium Aux,100/120/130AH under bonnet,with 40A DC/DC,many do this with no issues,and have been doing it for a few years.Leave the start as a wet cell,as it is now.I dont really want a battery in the vehicle.
But that is huge money,around $500 for the DC/DC,anything from $1K upwards for a lithium,when i can get another AGM,for around $400 or less,SS whatever they are,stay with DT90,then i should be fine for another 3 yrs.And in 3yrs time the Lithium tech will probably be even better.

Going lithium i may also need a low voltage cut out module,many use a Victron.So more $.They seem to use hardly any power.ATM the DT 90 is the low voltage cut out.

Not greatly concerned about the $,more so is it worth paying for a lot more for not much gain?Or will it be heaps more gain?I don't know,depends who you listen to.

My son now has a 300W solar blanket,so i was thinking maybe borrow that and use with a new AGM.

Hi Maca and I go through this type of situation with my customers, once or twice a week, and more so since Covid.

The problem is not the isolator, or the batteries, or even your vehicle.

It is the way you use your vehicle.

I bet you either do lots of short drives and/or leave the D4 for long periods, because what you have described indicates a classic case of badly sulphated batteries.

If you are interested in seeing if you can recover your existing batteries, have a look at the two links below.


Scroll down the page till you get to “LOAD TEST”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-10.html


Scroll down the page till you get to “Battery Maintenance”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-8.html



With the setup you have, when the batteries are in good condition, even if they are discharged down to the lowest level the isolator will allow, because you can replace that used battery capacity with a constant 100+ amps while driving, in a little over an hours driving, you can have both batteries at over 95% SoC.

Now if you still want to go to lithiums, you may find you have a very expensive but just as disappointing setup, and for the very same reasons.

The problem is now the recharge time.

You could safely use a 50 amp DC/DC device and in a perfect world, you will still be looking at at least 6 hours of constant driving to get those batteries up over 95% SoC.

But because your D4 has a SMART alternator, which you have already pointed out that the voltage drops when the cranking battery is full, most modern DC/DC devices have a maximum INPUT current limit.

With older and some of the cheaper new DC/DC devices, as the INPUT VOLTAGE drops, to be able to maintain a constant OUTPUT CURRENT, these devices increase their draw on the INPUT CURRENT from the vehicle.

This input current draw can be massive and I read of one guy in New Zealand, who was monitoring both input voltage and current as well as the output voltage and current and he noted that his 50 amp DC/DC device was pulling in 98 amps and only charging his batteries at 46 amps. And note, the input voltage was something like 13.5v, which is not that low.

It is pretty obvious what the potential danger is with such a setup.

With new good quality DC/DC devices, for safety reasons, the INPUT current draw is limited, so while the input voltage is high, say 14.5v, the OUTPUT Charging current might be 50 amps.

But as the voltage drops, because the input current is limited, at 13.0v input voltage, you might be getting as little as 30 amp output charging current and at 12.5v, a common operating voltage for any vehicle with a SMART alternator, who knows how little the charging currents is.

So again, as I posted above, your recharge time for those batteries, if in a low state, could be quite a bit longer than 6 hours driving time.


SPECIAL NOTE, if you go lithium batteries, you will need a DC/DC charger that can charge lithium batteries and make sure you set it to IGNITION sense NOT voltage sense, because while the IGNITION will reduce the output charging voltage when the D4’s voltage is low.

With the VOLTAGE setting selected, which most so called experts use, when the D4’s voltage drops below 12.7v, the DC/DC deice will turn off and not charge at all.

I too have the Traxide full setup in my D4.
I'm waiting on delivery of a Defender and need to set up the D4 in case it's needed for our trip next month. My approach is a 'semi-transferable' setup that will transition to a permanent fitout in the L663 (if/when it arrives!)

Battery - PowerPaul Cub Scout 190Ah, 250A BMS
Case - Aldi battery box with a bunch of connectors ready to go so I don't have to source and wire those in the short term.
the battery comfortably fits in the box and I can just secure it in the cargo space initially.
Charger - Victron DCDC 12/30A
I will use the Traxide rear anderson plug to feed the DCDC charger by pulling it into the cargo space.
System will run a 3000W inverter, induction cooktop, coffee machine, 75L fridge/freezer, travel oven as I am not going to use gas anymore.
In the D4 I will still have use of the Traxide set up as well as the lithium and they will be separated while in camp.
Permanent solution will include Victron MPPT solar charger for solar charging.
You'll find PowerPaul on Facebook and he's going to soon have more battery options including slim format. Passion for quality in a locally made and supported product.

Originally Posted by scarry

Both the start and Aux are almost 3 yrs old and tired,and i charge them up separately at least once a month,often twice a month,overnight,but still only lasted 3 yrs.

Hi Scarry, you first need to totally reverse the effects of Sulphation, before you do the once a month followup.

Doing a once-a-month charge does not reduce the sulhpration by much and it soon builds up again.

You need to get rid of as much as the sulphating as you can and then the Once-A-Month charging will help keep sulphating at bay.

Again I suggest you follow the info in the links.

Originally Posted by jwb

You'll find PowerPaul on Facebook and he's going to soon have more battery options including slim format. Passion for quality in a locally made and supported product.

I have been following his Facebook page for quite a while and he sure knows his stuff.

Originally Posted by drivesafe

I bet you either do lots of short drives and/or leave the D4 for long periods, because what you have described indicates a classic case of badly sulphated batteries.

negative. I drive >30 minutes 2x day, 4x a week. At least twice a week the trip takes up to an hour. Very rarely is the car left for more than a few days. I don't doubt the batteries are sulphated but it won't be because of the reasons you've suggested it is.

Originally Posted by drivesafe

If you are interested in seeing if you can recover your existing batteries, have a look at the two links below.


Scroll down the page till you get to “LOAD TEST”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-10.html


Scroll down the page till you get to “Battery Maintenance”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-8.html

I've tried the battery maintenance before with no noticeable effect.

I appreciate the advantage of your systems is charge time but for my purposes - when I'm driving on a trip, I'm driving for a good while, at least a few hours between camps sometimes a lot more, then spending a few nights before moving on. So charge time is less of an issue than capacity is.

If it's weekly or more that someone is having similar issues of premature battery failure, batteries overly sulphating, batteries not charging sufficiently, then perhaps it's just not a suitable setup for a car with a smart alternator? An ignition sensing DCDC charger would at least draw down on the cranking battery when the car is on which would trigger the BMS to ramp up the smart alternator charging.

Originally Posted by Macadamia

I appreciate the advantage of your systems is charge time but for my purposes - when I'm driving on a trip, I'm driving for a good while, at least a few hours between camps sometimes a lot more, then spending a few nights before moving on. So charge time is less of an issue than capacity is.

If it's weekly or more that someone is having similar issues of premature battery failure, batteries overly sulphating, batteries not charging sufficiently, then perhaps it's just not a suitable setup for a car with a smart alternator? An ignition sensing DCDC charger would at least draw down on the cranking battery when the car is on which would trigger the BMS to ramp up the smart alternator charging.

The Traxide should be helping on both fronts - draws from the starter and aux with the engine off to maximise capacity, then charges both with the engine on. ie, it ramps up the voltage just as you describe?

That said, my USI160 failed recently, forcing me to link the batteries directly together full time as a workaround. I ended up with far more capacity than I had ever had with the isolator installed - the voltage in the car was higher in the morning than it had been previously (with a fridge running in the back overnight). I accept of course, this is hardly a scientific process, but options were limited whilst on holiday... The difference was start though - typically seeing 12.2 or so at first, and 12.6 after linking. Both, after receiving a full charge prior. I suspect my USI160 unit was faulty for a while though, as the red plastic caps on the terminals had melted on from the heat it was producing!