“Second” Battery Replacement Thought Process (1 Viewer)

[SnoViking]

Hey folks,
I’m trying to think thru buying a replacement second battery for my LX570 and want some opinions. I’m trying to not overthink things but know there’s a few pitfalls in regards to mixing battery types (and maybe the “smart” alternators the trucks have)

I have a 2008 LX570 with a DIY second battery tray on the passenger side. I’ve been running an old and basic charging relay (more on this later) and a standard wet cell (sealed) 24F battery (a Toyota/Lexus battery from 2014). The chassis battery is a Advance Auto Platinum 24F AGM (which is about 3 years old).
On our latest camping trip, the second battery (only used for an Indel B 40L fridge) wasn’t cutting it. I’d get about 6 hours and it would drop below 10.8V. One issue I had was the charging relay would not connect until it saw 13.5V or more. I rarely see more than 13.3 so it was not toggling on and charging. I manually toggled it and it worked then. I did purchase a Blue Sea ACR-SI as a replacement which should solve that issue. But I'm pretty sure the old toyota/lexus 24f is toast (it had a good run......)

I was originally going to get a EverStart Maxx Marine 24F from Walmart for $80 and use that as the second battery (simple and done). But I was thinking of getting a 27F size and replacing the chassis battery with the 27F and move the 24F to the second battery position (I do not have room for a 27F on the passenger side). But then I hear stories of people mixing AGM and non-AGM and having issues. I do not want to buy two batteries and replacement convenience is important to me. I want to be able to stop in any Walmart, Autozone, or Advance Auto and replace it. I’m not a huge Walmart guy but the longer warranties lure me in....

thoughts?
opinions?
Experience?

 

[TeCKis300]

I apologize if I'm being too candid here. What you're proposing going forward won't work for a number of reasons.

1) A single charging source (alternator) cannot tender multiple batts at different states of charge. You see this with your existing setup, and it will continue to be an issue. Smart alternators no longer produce excess current to charge secondary batts (true since early to mid 2000s) with simple charge relays. You need a DC-DC charger to tender the second aux battery.

2) I'd bet your 3 yr old AGM doesn't have the reserve capacity you think it does, and I'd go so far as to say its closer to end of life than new. AGMs don't like underhood heat and will prematurely fail installed in the engine bay. The stock alternator charge profile is only suitable for flooded lead acids, which means it's probably been overcharging the AGM without the right temperature compensations, further degrading it.

3) With the AGM in the aux position, it won't charge right due to #1. A DC-DC charger will charge it and can further help as they can be configured with the right AGM specific charge profile. But these battery types still don't like underhood heat. This can work if an AGM is installed in the rear trunk area.

4) If you want a cheap and effective solution, replace both batts with any standard flooded lead acid, even group 24 or 27. Wire them up as a single bank per the link below. You'll have immense reserves compared to any dual bank configuration. Immense current capacity. Also longer overall life as any reserve use is now divided in half between the batts.

KISS Dual Battery Upgrade

There’s been a lot of discussion on batteries and battery systems. Here’s my attempt to offer an easy button. The task of a battery first and foremost is to offer power and reserve capacity. There’s many battery setups and systems talked about. But perhaps some of those are solving a problem...

forum.ih8mud.com

 

[SnoViking]

I apologize if I'm candid here. What you're proposing going forward won't work for a number of reasons.
......

KISS Dual Battery Upgrade

There’s been a lot of discussion on batteries and battery systems. Here’s my attempt to offer an easy button. The task of a battery first and foremost is to offer power and reserve capacity. There’s many battery setups and systems talked about. But perhaps some of those are solving a problem...

forum.ih8mud.com

No need for the apology. That's why I'm here looking for info. I'm a bit out of current tech info these days and am trying to relearn as much.

Reading thru the KISS Dual Battery Upgrade post (lots of good info on there BTW) added a lot of good thinking points. I only run the Indel B 40L fridge and a few USB outlets. I don't run a winch, light bars, or other accessories. Generally speaking; We're only ever parked for 24 hours and then we're driving somewhere for something.

I'm currently using a Victron SmartSolar Charge Controller to "manage" my accessories.

I have a Blue Sea fuse block wired to this and keep tabs on my usage and voltage (and have a low voltage cut-off set).

I'm leaning towards the simple two 24F EverStart Maxx batteries wired in parallel. As much as I'd like to size up, I don't have the room on the passenger side. I think two 24F batteries in parallel will have more AH than one group 31. I do carry a jump pack and rarely travel solo (either with a friend exploring or to a camp ground). Running a second battery under the hood also helps free up some room in the cargo area. I had a DIY battery box made up previously which sat behind the fridge but space is at a premium inside.

I'm still debating whether or not I want to add an automatic charging relay to the system to be able to "separate" the two batteries if needed.

 

[sdnative]

Not going to fit a group 27 or even a group 24 in the PS engine compartment without work. If you have room in the back and can swing the cost maybe look into lifepo4 batteries? Or even a goal zero yeti. Even a small one will give you more usable capacity than a group 27 lead acid.

 

[SnoViking]

Not going to fit a group 27 or even a group 24 in the PS engine compartment without work. If you have room in the back and can swing the cost maybe look into lifepo4 batteries? Or even a goal zero. Even a small one will give you more usable capacity than a group 27 lead acid.

I already have a 24F mounted on the passenger side.

 

[sdnative]

Sorry I missed that. Maybe a matched set of group 24 would fit your needs then. Still not a lot of Ah though.

 

[SnoViking]

Sorry I missed that. Maybe a matched set of group 24 would fit your needs then. Still not a lot of Ah though.

I was looking at various different battery banks and solar generators and have considered them. Going with a second 24F I'm hoping to get an "additional" 30-35Ah that puts me inline with the GZ Yeti 500 for less than 1/3 the price....

Why is trying to keep beer in remote places cold have to be so difficult!?

 

[bemerritt]

Theres a lot of info on this site, and discussions tat ultimately go in circles. What has worked for me is upgrading my main battery to an odyssey extreme which gives 100 ah and changing the fuse for a higher charge voltage. Additionally, I added a 100 watt panel on the roof to give the battery a higher voltage charge experience which the agms like.

Like you, main use is dometic fridge and cell phones.

I like that its one battery, dont have to balance two. The charge voltage is a problem, but thats the problem I've chosen to deal with instead of the others. Bonus is the solar will pretty much run the fridge indefinitely, so longer stays in one location and sitting in the driveway for long periods are no problem.

 

[SnoViking]

Theres a lot of info on this site, and discussions tat ultimately go in circles. What has worked for me is upgrading my main battery to an odyssey extreme which gives 100 ah and changing the fuse for a higher charge voltage. Additionally, I added a 100 watt panel on the roof to give the battery a higher voltage charge experience which the agms like.

Like you, main use is dometic fridge and cell phones.

I like that its one battery, dont have to balance two. The charge voltage is a problem, but thats the problem I've chosen to deal with instead of the others. Bonus is the solar will pretty much run the fridge indefinitely, so longer stays in one location and sitting in the driveway for long periods are no problem.

I have a basic solar setup and think my current panel is on the fritz which is not helping. It's a foldable 100w and best case I see maybe 30-35 watts (super clear sun, with me playing with the position and watching the output.) That combined with a failing house battery I think is getting me.

I'm on my third different 100w panel setup and have no found one that last more than a two years. :-(

 

[bemerritt]

I have a basic solar setup and think my current panel is on the fritz which is not helping. It's a foldable 100w and best case I see maybe 30-35 watts (super clear sun, with me playing with the position and watching the output.) That combined with a failing house battery I think is getting me.

I'm on my third different 100w panel setup and have no found one that last more than a two years. :-(

I think those portable ones are really prone to failure. You aren't the first person I have heard have such experiences. I have had and helped with probably 6 or so Renogy panel setups and all have stood the test of time. Obviously permanently mounted solar is a committment that probably many don't want to make for a variety of reasons. But for this application it serves its purpose.

 

[Fisher23]

You may want to look at the litium setups on this thread

Working to finish up 12v Aux System, and have a few questions

We seem to be on similar paths with our builds. Here is what I am working on now. Just placed there to mock up component mounting. The batteries are only 40Ah each, so 80Ah with them wired in parallel. A little smaller than I would like but still more usable capacity than a single group 31...

forum.ih8mud.com

 

[sdnative]

You may want to look at the litium setups on this thread

Working to finish up 12v Aux System, and have a few questions

We seem to be on similar paths with our builds. Here is what I am working on now. Just placed there to mock up component mounting. The batteries are only 40Ah each, so 80Ah with them wired in parallel. A little smaller than I would like but still more usable capacity than a single group 31...

forum.ih8mud.com

I have since changed gears since my post there and am now planning on building a larger battery out of raw cells. At least that's the plan today anyway.

 

[TeCKis300]

2x group 24s as a single bank will easily do the job and have about 70% more capacity than stock. More significantly, it's still 60% more usable capacity than even the largest group 31 single battery or dual battery dual bank solution. 60%!

A single group 31 still a great solution, especially if augmented by a solar panel.

I'd recommend again, a flooded lead acid (FLA) to avoid the charging workarounds that ultimately will not stand the test of time IMO.

There's high quality FLA batts out there that have many of the qualities we seek from AGMs, including robust construction, vibration resistance, lower internal resistance for higher amp charge/discharge support, etc. Example

I likewise use a portable solar panel for extended weekend camping stays. I have it setup with a SAE pigtail. As I already have a permanent SAE pigtail on my battery for a float charger when I'm on longer vacations, it's easy to plug in.

 

[Markuson]

Theres a lot of info on this site, and discussions tat ultimately go in circles. What has worked for me is upgrading my main battery to an odyssey extreme which gives 100 ah and changing the fuse for a higher charge voltage. Additionally, I added a 100 watt panel on the roof to give the battery a higher voltage charge experience which the agms like.

Like you, main use is dometic fridge and cell phones.

I like that its one battery, dont have to balance two. The charge voltage is a problem, but thats the problem I've chosen to deal with instead of the others. Bonus is the solar will pretty much run the fridge indefinitely, so longer stays in one location and sitting in the driveway for long periods are no problem.

Agree about the circular discussions on this issue.

Have you done a write up or post on your solar setup? If so, would love a link. If not...maybe post up?