Optima D34 Yellow top or SSB DryCell HVT-50D AGM

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Originally Posted by Victim

Thanks for the input, I will give this a try when I can. The vehicle is generally driven multiple times every day, so it could be a while before I can confirm results.

FYI - Traxide isolator is the SC-80. Both batteries have Bluetooth monitors fitted.

I posted about this issue due to a recent interstate overnight work trip - as a precaution, I had charged both batteries to float overnight the previous evening, then double locked my car at the airport carpark at 7am on a Monday. I left the fridge running, as I was due to return the following afternoon around 2pm. On my return, I could see the fridge had already turned off. I downloaded the Bluetooth battery history before unlocking the car, and could see that the Traxide had disconnected the main battery around 7am Tuesday (24hrs after fully charged at home). The fridge only managed 1x full compressor cycle on the Aux battery after this, then it cut out during the next cycle 1.5hrs later. Both batteries had settled at around 12.2V for the next 5 hours before I returned to the vehicle. I could see that once the main battery had disconnected, the Aux battery voltage dips much lower when the fridge compressor runs and it appears to have dipped far enough to trigger the 11.6V cutout of the ABG-25 low voltage cut-out module and turned off the fridge.

As a test, is it safe to just disconnect the negative lead from the Auxiliary battery and still drive the car as usual during the day, or do I need to completely disconnect the SC-80 as well? This way I could compare the drain from just the main battery running the fridge overnight compared to running both batteries via the Bluetooth history.

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Hi again and unfortunate just charging for one night is not enough to reverse any Sulphation that may have built up over time.

It does sound like sulfration is the problem and the data from your BM2 indicates the Traxide isolators are working to spec, you are just down in battery capacity.

Have a look at these two links and see if they help you.

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 had three yellow tops since 2014 or was it 2015? I felt my caravan at a friends house in Brisbane due to getting caught with Covid and Victoria shutting down. The car was for 10 months i think ... he reckoned the drove it regularly, (and in fact he took it to the Flinders Ranges with my permission) but after that I think he left it and the batteries both failed. So i reckon but for that the 2nd yellow top might still be going ... but i have an Autofridge and they are Eutectic, so they only need to run for 3 hours a day (unless as a freezer where its an extra hour if under 40C ambient). So not much work for the battery. Using Traxide of course.

But if I had a normal always on fridge, I'd put an el-cheapo iTech lithium in the back with bluetooth so I could see the cells, which can be charged with normal 12volts, and have a switch so it doesn't drain the secondary battery (And they can have bluetooth. Batter quality ones cost a lot more and also you have to add a DC-DC charger. And blue tooth also adds more cost (but IMO is worth it). The advantage of lithium is that they don't sulphate and you can run them down to 20% with little effect on life. But full charging shortens their battery life. So knowing their state is essential IMO, hence the benefit of bluetooth. However lots of batteries can get complicated when they run out ... one then has to charge them somehow, and you are essentially back to have a secondary battery. I use a solar panel (el cheap kings) and plug it into the yellow top. Maybe that is why they last so long for me.

If no traxide, I'd be tempted to KISS and run a rear lithium off solar panels. My Kings old blanket 200 watt seems to produce around 14-16 amps (their 360 watt they claim 30 amps so I'd estimate 20 amps in full sun) and if a fridge uses 45 amps a day, a panel will provide in sunshine lets say at 14 amps, 6 hours, 14x6 =84 A/H less 45 you are in front. A 200 AH lithium will provide (and if iTech I think a 200 is really in watt hours quite a bit less so say 180), to 20% is to 40 A/H, so 180 - 40 = 140 A/H, divided by 45 for a days run, that is 140/45=3 days of running the battery without sunshine. Get a full day of sun = 14 Amps x 6 = 84 less 45 = about 40 A/H gained, almost an extra day. Worth thinking that way IMO.

A 200w solar blanket doesn’t generate anywhere near 20a. They just aren’t that efficient.

And I wouldn’t be charging any battery - Itech or otherwise off 12.7v and expecting it to be fully charged.

Hi Melbourne Park, first off, as Tombie posted, you are not going to get the ampere return you think you will get from any solar panel setup.

First you need to keep moving the panel to get the maximum sun coverage at all times.

Next, the maximum “Advertised” output is almost impossible to achieve in normal use and the hotter the temperature of the panel, the lower the output will be.

Lithium batteries do not charge well in any vehicle with a SMART alternator operation and will actually discharge while driving long trips.

This is the reason it is imperative to use a DC/DC device to recharge lithium batteries while driving, and even then, if the alternator voltage goes to low, and depending on how low the alternator voltage gets, you may get a reduced charging current or no charge at all.

In an case it will take much longer to recharge any battery, lithium or lead acid, when using a DC/DC device in an type of vehicle.

An Itech 200Ah battery actually only has about 150 amperes available. Their Lithium Battery BMS shuts their batteries down at around 25% SoC.

Most lithium batteries shut down at around 20% SoC and you have no say in the shutdown level.
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Now before you get the wrong idea about me, I actually am a big fan of lithium batteries, BUT only when they are used in the right environment.

In a camper trailer or caravan, lithium batteries have a whole host of advantages over lead acid batteries.

In vehicles, they are not so advantageous.

All batteries, lead acid or lithiums, do not like engine bay heat, but lithium batteries are far more susceptible to heat and it can dramatically shorten their lifespan, depending on the brand of lithium battery.

Another drawback that most people are unaware of is that most lithium batteries can not be used to jump start a motor, as they will either just not start the motor or can be permanently damaged after just one jump start.