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Isolating Lithiums; This look good? (Diagram inside)


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Long post: Engaged

TL;DR at bottom

 

So I'm still pretty fresh to Lithium batteries and the in's and outs/do's and don'ts of properly installing them. I know these things are nothing to fuck around with and use willy-nilly, so I'm trying to learn as much as I can and take the proper precautions as I install them. I'm hoping someone who's knowledgeable on the subject can chime in and back up my current plan and/or educate me on what to do. 

 

My question is this: Does this diagram look like a good/doable solution to isolating my rear lithium banks to avoid overcharging and engine-off draining? 

 

9yQDw5O.png

 

My goal is to have the ability to toggle the alternators charging to the Lithiums via isolators and a basic toggle switch while driving around, that way I can minimize the risk of overcharging and possible venting.

 

Here's some more info into my situation.

- This will all be going into my daily, which is one of the reasons why I want to keep the lithiums isolated from extended periods of charging from the alternator.

- I've never installed an Isolator, so I'm not even sure if my schematic is properly designed to get isolators working on a toggle switch properly as I'd like. Please educate me!

- I'm currently reading through the battery university articles on Lithiums, and have come to understand (could be misunderstanding, though) that LiFePo4 are sensitive to overcharging, especially at higher voltages surpassing their 3.6v cell maximums.

- I'm currently walled, so all the lithiums will be resting inside the cabin with me, directly behind the front seats of the vehicle (2014 Scion TC). Hence, the cautionary approach.

- The isolators would serve as a safety measure for me to use while I'm driving around and when I park. Turn them ON when I'm not draining the lithiums with full tilt stereo use, and when I park to prevent the agm from draining the lithiums.

- When driving around and using my stereo, I'd have the Isolators OFF and the lithiums would then connect with the front agm and receive the alternator charge. 

- When driving around and not putting a load from my stereo on the lithiums, I'd have the isolators ON to keep the lithiums from getting too much charging.

- As the image states, currently on stock alt. Will at some point upgrade to a 180amp alternator when I upgrade the amplifier.

- Amplifier will more than likely be a B2 riot 7500

 

What do you all think? Am I safe in my current plans? 

 

TL;DR: Does my isolator for lithium bank diagram look right/safe/doable? Am I missing something?

 

Thanks for any input guys.

 

My Channel on YouTube. Check it out for cinematic-style Car Audio videos.

https://www.youtube.com/channel/UCcSMhtT-rpopJbdybubDgnQ

 

New 2014 Scion TC 4th Wall Build

https://www.stevemeadedesigns.com/board/topic/217173-2014-tc-4th-order-build-3-fi-sp4-15s/

 

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A smattering of thoughts in no particular order
 

  • Your isolators are normally closed? Attempting to leave them energized such that they're open will cause a parasitic drain
  • That will work. It's my opinion that you're working hard to bandaid an issue though.
  • Don't forget a fuse on your switch. Also, I like switched grounds as opposed to switched positives.
  • Ditch your under hood battery. Install a dummy battery or replace it with a capacitor or something. Do NOT put lithiums under the hood. Too hot!
  • For insulation / fire safety, get some ceramic wool like is used in melting furnaces. Just be mindful you have a temperature control system in place. Too hot is bad. Too cold is bad
  • You should be running an externally regulated alternator when running lithiums. Or a similar means of preventing the differential hot / cold charging voltage.
  •  
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9 hours ago, SnowDrifter said:

A smattering of thoughts in no particular order
 

  • Your isolators are normally closed? Attempting to leave them energized such that they're open will cause a parasitic drain
  • That will work. It's my opinion that you're working hard to bandaid an issue though.
  • Don't forget a fuse on your switch. Also, I like switched grounds as opposed to switched positives.
  • Ditch your under hood battery. Install a dummy battery or replace it with a capacitor or something. Do NOT put lithiums under the hood. Too hot!
  • For insulation / fire safety, get some ceramic wool like is used in melting furnaces. Just be mindful you have a temperature control system in place. Too hot is bad. Too cold is bad
  • You should be running an externally regulated alternator when running lithiums. Or a similar means of preventing the differential hot / cold charging voltage.
  •  

1. Ah, gotcha. I had it reversed. When I said isolators on I meant it as in isolators stopping the flow of current. But yes, I want them OPEN when I want Alternator charge and CLOSED when I don't need it.

2. Awesome, thanks! I'm not really sure how else to approach my situation other than this. I really want to run lithiums in my daily vs heavy AGMs, but I do agree there's quite a bit extra I'm doing lmao.

3. Forgot to draw that fuse in, lol. And the isolators on the negative, what would be the reasoning behind that? I'm not opposed to that at all, I just like 2 Isolators option vs 3 for space reasons.

4. Yeah, for sure no lithiums anywhere near the engine bay heat. I have the AGM under the hood mainly because I like having an extra battery for some extra juice should I need it when demoing, and also since I had bought it before I knew how much I'd have to do to work in Lithiums lmao. Also is nice to have there so I don't have to modify any stock wires to extend out reaching to the lithiums in the back.

5. Thats what I need, THANKS! I plan on building a battery box with a hinged top that I can latch down so in the case of venting there's another layer of something between me and the batteries. I couldn't figure out what kind of fire proofing material I should use, but I knew I wanted to line the box with some form of added fire retardant material. thanks! Also (though not shown in the diagram), I'm gonna grab some temp sensors off ebay/amazon and wire em up to each battery individually. Might even try to tie in some fans too.

6. This was also another concern of mine that I'll address. For now, my plan was to simply keep the isolator circuit closed until the alternator warms up to it's normal operating voltage. Even then, stock alt charges COLD at about 14.2. When I do upgrade however (DC Power 180), I'm definitely gonna find some type of regulator to adjust cold charge voltage. 

 

I'm still looking for a decent model temp sensor though. All the ones I can find, though cheap, include a switch relay and buttons which is what I don't need.  Also, the board is a bit too big for me, as I want the LED display to be relatively small to fit on the dash.

 

Thanks for the info!

My Channel on YouTube. Check it out for cinematic-style Car Audio videos.

https://www.youtube.com/channel/UCcSMhtT-rpopJbdybubDgnQ

 

New 2014 Scion TC 4th Wall Build

https://www.stevemeadedesigns.com/board/topic/217173-2014-tc-4th-order-build-3-fi-sp4-15s/

 

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1. Open / closed refers to contacts. Closed = completed circuit. Open = no current flowing
3. Not isolators on the negative. Just the switch used. It simplifies wiring. Instead of having two wires through the firewall, you only need one, and can just complete the ground circuit inside the vehicle where convenient.
5. SMD / D'Amore offer an adjustable fan turn on / temp monitor
6. What alternator do you have? I'd do some serious cost analysis here. 500 amp solenoids are what... 75 to 100 bucks a piece? A transpo 911-02R external regulator will run you about $115. Just need to figure out how to wire it into your alternator, whether it be a direct connection because it's externally regulated from the factory, or you need to swap the regulator / brush pack out

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17 minutes ago, SnowDrifter said:

1. Open / closed refers to contacts. Closed = completed circuit. Open = no current flowing
3. Not isolators on the negative. Just the switch used. It simplifies wiring. Instead of having two wires through the firewall, you only need one, and can just complete the ground circuit inside the vehicle where convenient.
5. SMD / D'Amore offer an adjustable fan turn on / temp monitor
6. What alternator do you have? I'd do some serious cost analysis here. 500 amp solenoids are what... 75 to 100 bucks a piece? A transpo 911-02R external regulator will run you about $115. Just need to figure out how to wire it into your alternator, whether it be a direct connection because it's externally regulated from the factory, or you need to swap the regulator / brush pack out

Thats right, I totally forgot about the SMD module. I'll have a look at that one too. As for the Isolators, There's a few 500 amp ones that sell for around 60 a piece. I'm reading up on the voltage regulator too, from what I understand my stock alternator on my car is internally regulated. I'll be upgrading to a DC Power 180 amp later down the road. 

 

And I can't believe I NEVER thought to throw the switch onto the ground of a circuit. I think that's what I'm doing from now on LOL

 

thanks for all your input! 

My Channel on YouTube. Check it out for cinematic-style Car Audio videos.

https://www.youtube.com/channel/UCcSMhtT-rpopJbdybubDgnQ

 

New 2014 Scion TC 4th Wall Build

https://www.stevemeadedesigns.com/board/topic/217173-2014-tc-4th-order-build-3-fi-sp4-15s/

 

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