Running parallel is common practice. You can read about it here https://learn.sonicelectronix.com/how-to-big-3-upgrade/

Agreed on the uprating of winch control cables if extending. I was thinking of running the compressor inside the second battery box if possible (Still need to check fit, but this will at least keep it high up and offer a little bit of protection against dust and road salt).

I will most likely do a flexible (portable) solar panel that I can use whenever I am using the battery box outside of the vehicle. Planning on running a soft roof top tent for trips which leaves very little room for hard mounting a panel on the roof rack.

Really appreciate your input on this, thanks!

 

I’ve had an AGM for a while in my not-oft driven 2005; and it’s a pain in the ***.

 

Picked up another AGM today. EverStart H8 Platinum from Walmart for $180. The FLA H8 wasn't much cheaper at $160. AGM has a 4 year warrantee and the FLA has 3. My reasoning was that I'll most likely never be more than an hour away from a Walmart if I ever needed to claim against the warrantee and if it lasts me 4 years that should be fair at $45 per year. Have it sitting on the Garage floor being charged by the C-Tek. Will do my best to hook it up to the charger once or twice per month to make sure the battery is topped up.

 

4 years I think in the lr3. It was the only battery

 

No need to change to an aftermarket alternator for a winch and DCDC charger, my traxide controller can take up to 80a and never been an issue with my winch or 85ah agm auxillary battery running fridge and lights.
That battery is over 6 years old and main is a lead acid that is 4 years old, winch, spotlights and 42 " led lightbar are only used when engine is running so doesn't affect the batteries.

 

Is that DC to DC converter stepping up the voltage to charge the LiPO4 battery?
There are people in my club that run winches on the LR3 without issue. I just added a winch and don't forsee a problem.
I have seen my alternator put out 14.8 volts when the battery is down (these cars seem to draw a lot even when shut down).
Lastly, I run my fridge from a 100 Ah AGM battery and can go 2 or 3 days before it gets down much. Just using the fridge as a fridge, not freezer, so runs less.

 

Thanks for the input! I will stick with stock size for now and see how it goes. There are so many variables to consider that it is next to impossible to do a calculation and come up with a simple answer. Worst case I will kill the AGM start battery sooner rather than later.

Just FYI - AGM and Lithium have very different charge absorption and discharge rates. Lithium has a very low internal resistance and is generally rated for 1C discharge - meaning you can discharge a 100Ah battery at 100A for one hour without damaging the battery. It will also take a 100A charge rate meaning a 100AH battery could be recharged in as little as one hour (this is not recommended for longevity). AGM on the other hand goes through stages - bulk, absorption and float. During the bulk phase, they can consume between 0.2C and 0.4C In your case, an 85Ah battery will draw between 17A(0.2C) and 34A(0.4C) after which they switch to the absorption phase and the charge current starts to drop off quite steeply. The closer they get to full charge, the less current is consumed - in the end only around 1A or 2A. This is actually great for the alternator and the starter battery as there is time to meet the charging needs of the secondary battery. You can read more about it here - https://marinehowto.com/how-fast-can...ry-be-charged/

Obviously the downside to AGM (from our perspective) as a secondary battery, is the time it takes to recharge the battery due to the charging characteristics, the weight of the battery, and the fact that you shouldn't discharge an AGM to less than 50% if you want to ensure a long life. This means if you have a fridge that draws 2.5A (eco setting) and runs for 30min per hour (consumption of 1.25Ah), you would be able to run said fridge for 40h on a 100Ah AGM battery, whilst you could run the same fridge for 80h on a 100Ah Lithium battery. Discharging lithium to 100% isn't recommended either, so lets say we will only discharge it to 20% SOC, giving us 64h runtime out of our battery. To equal that in an AGM Battery, we would need a 160Ah AGM Battery.

Recharging the batteries once we get going - via the vehicle - we could recharge the Lithium from 20% SOC to 100% SOC using a 50A DC to DC Charger in as little as 1h40m, whilst recharging the 100Ah AGM from 50% SOC to 100% SOC could take 5h assuming a 0.4C charge rate and constant Voltage supply. The same holds true for solar in terms of time needed to recharge a battery, so ultimately there are a lot of benefits to Lithium, and that's why I chose it as a secondary battery.

BUT because Lithium has such low resistance, it is a current hog, and will happily suck all the current it can until it is fully recharged. This isn't great on shorter drives, as you have a huge load (50A) on top of charging the starter battery which will enter its Bulk charge stage requiring between 20A and 35A as soon as the vehicle starts. Add to this the requirements of heated seats, heated windscreen and AC (All used from the moment the vehicle starts), and it obvious that doing this (short drives only) repeatedly over a couple of weeks/months and not putting the starter battery on a tender will most likely kill the AGM starter battery pretty soon.

Batteries are there to act as a shock absorber for the electrical system and also as a means to run the starter motor before the alternator gets going. An electrical system should always be designed for worse case scenario in terms of current draw and headroom added on top of that for safety. That means the Alternator should be able to cope with the entire load of the system in terms of its output at IDLE. Inthe case of a winch, the starter battery will supply the winch needs only up to a point. Winches are irregular draws on the system, so unless you are winching multiple times per day, whilst barely idling, you should be ok.

In my case, there are things that I could do to mitigate the draw:

• Set the DC to DC to deliver a lower output to the Lithium battery. Say 30A instead of 50A (in the ideal world, there would be a smart DC to DC charger that is connected to a shunt on the starter battery, and adjusts its draw/output to account for vehicle draw - in effect sensing when it can ramp up, and ramping down when the vehicle needs more power from the alternator),
• Add solar panels to keep the Lithium battery topped off (there are drawbacks to the battery life doing this), reducing the need to run the DC to DC charger,
• Have the DC to DC charger switched in the cab, so it can be disconnected in cases where the winch needs to be used for example.

All this being said, I may still end up with a larger alternator because I choose to only go wheeling in the hottest months, run my entire fridge as a freezer so I can eat Ice cream multiple times per day, get myself in over my head on the wrong trails and have to winch twice as much, camp under trees for days at a time, refuse to get a second/larger secondary battery etc. Running a larger alternator on a system with larger demands is good practice. No alternator will provide its maximum output rating constantly. As it works, it heats up, and output starts dropping off. A 50% duty cycle on a 250A alternator is better than an 83% duty cycle on a 150A alternator.

This is longwinded, I know. The point is, just because something works one way for one person, doesn't mean it will work for someone else. Your system may be very different to mine, so you cant say "I don't need a high output alternator so you don't either". There are so many differences to account for - You run a FLA as starter, AGM as secondary battery (most likely wired up to the starter battery seeing that you have a traxide installed) which means you have a much larger shock absorber/reserve to draw from when you winch. You are not putting a 85A load on your battery/alternator just because your traxide is rated to 85A. Because of your battery chemistry and the way it is wired up, you wont have a constant 50A draw on your system or alternator either, your largest load will be during bulk charging and it will be short. My lithium battery is also not wired into the system as a supply. It is only there to run my fridge/camping accessories, and does not act as an additional shock absorber/reserve during high draw situations like idling whilst running the AC whilst winching.

All of the factors have to be taken into account. I may very well be overthinking this, but it has been a very enlightening exercise and the questions have made me read more and dive deeper into the topic. Thank you!

 

Yes, it has profiles so you can select which type of battery you will be charging, which alters the charging profile (including charge voltage).

Thanks for the feedback! I have a dual zone, but can run both as fridge or freezer. I suppose it depends on you needing ice cream when you reach your destination or not

I believe the 14.8V ramp up is only for a short duration - I read after startup it will do that to try and quickly recover the energy used by the starter.

 

Dude rad! Puts my mind at ease. Thanks!

 

Maybe I should have clarified the idea from the start. I don't have a way to measure the amp draw on the current OEM setup (it will differ in different scenarios so ideally it has to be data logged over a longer period to get an accurate reading of the max amperage draw on the system) to see exactly how much room I have to add accessories Here is the setup I am aiming for:

LR3 V8 HSE
AGM H8 Battery
To add:
10/12K Warn Winch - 396A Max
ARB Single Compressor - 30A Max
50A DC to DC Charger - Selectable but ideally 50A

DC to DC Charger will be responsible for recharging a 100AH Lithium battery in a case (think of it as a Jackery) that can be removed from the vehicle. Box contains a DC to DC Charger and MPPT controller for solar. Fridge will be connected to the battery box. Battery box and fridge will only be in the vehicle for longer journeys as Lithium does not like temperature extremes and vehicle lives outside.

There are ways to use the Lithium battery to charge the start battery, but as my battery will be in a case, I dont have the room to install extra switches and relays to do this. I will carry a NOCO jump pack with me if I do end up killing the battery. If I end up needing more than 4 jump starts, the NOCO can be recharged of battery case.