Not an electrical kind of guy at all. I want to add a 2nd battery to my truck. Plan on getting a 100ah LifePoe4 deep cycle battery. Mainly for weight savings. I plan to use the linked box.
I want to have the battery charge when the truck is running and when the truck is not running a solar panel.
I guess I need some sort of isolator or charger
Newport Vessels Trolling Motor Smart Battery Box Power Center with USB and DC Ports https://a.co/d/5xF9Zpr

This will be kept in the bed but will also want to be able to take the battery box out of the truck if I need.

You’re looking for what they call a battery to battery, or dc to dc charger. I have used Victron equipment, but there are probably less expensive options.

If you have a 7 pin trailer plug, tie into 12v wire.
https://www.ajtnt.com/Info/7-Way-Diagram

Use a 12v relay to control it in run position.
https://www.amazon.com/4-PIN-3...SSD7xDxoC8tUQAvD_BwE

Use a RV panel solar panel.
https://www.amazon.com/Upgrade...XhoCldMQAvD_BwE&th=1

quote:

Originally posted by a1abdj:
You’re looking for what they call a battery to battery, or dc to dc charger. I have used Victron equipment, but there are probably less expensive options.

Looks easy enough.
I watched a couple YouTube videos.

One ran the positive and negative from the vehicle battery to the DC to DC charger.
The other ran only the positive cable to the battery and grounded the other to the truck.
One used 4 gauge wire and the other used 2 gauge wire.
Is one way better than the other?
Both used a 40 amp Renogy unit. Renogy seems to be popular on the YouTube channels and has good Amazon reviews.
Not the cheapest out there but not crazy expensive either.

quote:

Originally posted by rizzle:
If you have a 7 pin trailer plug, tie into 12v wire.
https://www.ajtnt.com/Info/7-Way-Diagram

Use a 12v relay to control it in run position.
https://www.amazon.com/4-PIN-3...SSD7xDxoC8tUQAvD_BwE

Use a RV panel solar panel.
https://www.amazon.com/Upgrade...XhoCldMQAvD_BwE&th=1

I thought that 7 pin provided very little power and is not really sufficient for doing much more
than a trickle charge.

5 to 15 amps on the 12v 7 pin, depending on make/model of truck. Works for RV trailers, I did not realize that you want to charge completely discharged battery with it. So, do not use the trailer plug if you expect it to charge a dead battery. It will maintain a charged one though.

What is the rating of your truck’s alternator? Does it have enough spare capacity to charge a second battery?

Say you discharge your 100amp LiFePo4 battery to 20%, it will take over 5 hours for your truck to charge it back up to 100% if your alternator can provide an extra 20 amps.

And yes, you’ll have to have the appropriate sized cable to run the charger. I have a book for boat electrical systems that has tables for cable sizes for length of run and amperage, but I’m not at home at the moment to look it up.

This is the calculator I use for determining wire sizing. It’s pretty handy and worth bookmarking.

http://circuitwizard.bluesea.com/#

Don’t forget to use a charge controller. You can put switch in line to turn the system off but the controller will keep it from overcharging and killing your battery. Wires from panel go to charger, then from charger to battery. Renogy makes some cool 100watt and up thin, flexible, light weight panels that I plan to add to my solar setups.

quote:

Originally posted by trapper189:
What is the rating of your truck’s alternator? Does it have enough spare capacity to charge a second battery?

Say you discharge your 100amp LiFePo4 battery to 20%, it will take over 5 hours for your truck to charge it back up to 100% if your alternator can provide an extra 20 amps.

And yes, you’ll have to have the appropriate sized cable to run the charger. I have a book for boat electrical systems that has tables for cable sizes for length of run and amperage, but I’m not at home at the moment to look it up.

That would be the case if I only used an isolator setup to charge correct?

If I use a DC to DC charger that is 40 amps it boosts that level to 40 amps cutting the time to about 2.5 hours correct?
https://www.renogy.com/support...-rng-dcc1212-40.html

quote:

Originally posted by a1abdj:
This is the calculator I use for determining wire sizing. It’s pretty handy and worth bookmarking.

http://circuitwizard.bluesea.com/#

Thank you

quote:

Originally posted by 10X-Shooter:
Don’t forget to use a charge controller. You can put switch in line to turn the system off but the controller will keep it from overcharging and killing your battery. Wires from panel go to charger, then from charger to battery. Renogy makes some cool 100watt and up thin, flexible, light weight panels that I plan to add to my solar setups.

Thanks. I plan on finding the largest panel I can find that is slightly smaller as a section of my trifold bed cover. So I can add some soft spacers just to the outside of the panel so I can still fold my cover if need be and not have remove the panel.
Or I might buy one of those folding ones and build a bracket to attach it but be able to remove it.

quote:

Originally posted by Black92LX:

quote:

Originally posted by trapper189:
What is the rating of your truck’s alternator? Does it have enough spare capacity to charge a second battery?

Say you discharge your 100amp LiFePo4 battery to 20%, it will take over 5 hours for your truck to charge it back up to 100% if your alternator can provide an extra 20 amps.

And yes, you’ll have to have the appropriate sized cable to run the charger. I have a book for boat electrical systems that has tables for cable sizes for length of run and amperage, but I’m not at home at the moment to look it up.

That would be the case if I only used an isolator setup to charge correct?

If I use a DC to DC charger that is 40 amps it boosts that level to 40 amps cutting the time to about 2.5 hours correct?
https://www.renogy.com/support...-rng-dcc1212-40.html

Yes, provided your alternator has more than an extra 40amps available in order for the charger to provide 40amps because the charger will not be 100% efficient.

It'll take a bit longer than 2.5 hours. The battery can only accept the full 40amps to a certain state of charge. From that point, the charger will reduce voltage to finish charging the battery.

Victron dc to dc charger. Blue sea add a battery kit is popular too. Amps and recharge rate are all about the math when it comes to time to recharge. Lithiums will take as many amps as you give it, problem is they can also overheat your alternator if not regulated with a dc to dc charger. Wire size will be determined by length of run and amp draw, I always like to go up 1 or 2 sizes. They make some good quick disconnects for trolling motors that are rated for 50 amps, if you want to make the battery removable

IF you or anyone on here needs a lithium battery, I'm a Dakota dealer and will give a sigforum special discount.

I don't know how often you need to switch between the truck system and the solar panels so I'll leave that to others.
I'd recommend you use some version of Andersen connectors for the removable battery, both for the truck hook-up and whatever you'd be connecting to when the battery is away from the truck
They make a wide variety of hardware that is top quality and relatively inexpensive.
Their 50 A connector series most likely but here's an example of the connector and their catalog of items.

Connector example:
https://powerwerx.com/sb50-gray-pp45-adapter-cable

Catalog of terminals:
https://powerwerx.com/anderson...erpole-sb-connectors

Why not just buy something along the lines of a Bluetti 180ac? it already meets all your needs and comes set up to do what you want. They have a variety of sizes to meet whatever needs you have. It seems like a tailor made solution to your request. Now if you want the satisfaction of building it yourself, then never mind my suggestion.

The Bluetti AC180 weighs 35 pounds and is not water resistant, so it's not particularily suitable for running a trolling motor. Based on Black's choice of box, his desire for weight savings, and that he never mentioned a need for AC power, it seems like running a trolling motor is a likely use.

quote:

Originally posted by ltz400:
Why not just buy something along the lines of a Bluetti 180ac? it already meets all your needs and comes set up to do what you want. They have a variety of sizes to meet whatever needs you have. It seems like a tailor made solution to your request. Now if you want the satisfaction of building it yourself, then never mind my suggestion.

Because a power station that large will be close to $1000.

Buying a battery, that box, a DC to DC charger, wire, and connectors will be closer to $500.
Also 10-15 pounds lighter.

If I need AC power I have an inverter that I can attach to the posts on the side of the box.

quote:

100ah LifePoe4 deep cycle battery

You don't say what you are actually trying to use this second battery for? Which to me affects the design in any number of ways.

You might look into the LiFEPo battery that is self heating in cold weather. Those batteries do not like freezing at all.

“32°F
Charging a Lithium battery in ambient temperatures below 0°C / 32°F must be avoided. The reason for this is it may potentially damage the battery and / or reduce its lifespan. The optimum ambient temperature for charging a Lithium battery is +5°C to +45°C / 41°F to 113°F.”

What kind of truck are we talking about? Suggest getting on a type specific forum and prepare to bust out the credit card... Seems like a lot of these newer vehicles are really restricted in this regards (ie 3rd gen Tacoma seems like it costs some serious bucks to do what your asking due to the CPU controlled [limited] charging system)

Its really none of my business what you choose to do or what you are using this system for but the numbers just are not adding up.
-Battle Born Batteries:
100Ah 12V LiFePO4 Deep Cycle Battery
Weight 31 lbs.
$925.00
-Newport Vessels Trolling Motor Smart Battery Box Power Center with USB and DC Ports
$65.00 on amazon
-inverter cost ?
-DC to DC charger
Leaptrend 60A 12V DC to DC Battery Charger for Lithium Lifepo4, AGM Batteries, 60 Amp DC-DC 12Volt Chargers in-Vehicle for Car, Marine, RV, Boat, Van, Travel Trailer, Off Grid with Flooded Gel Battery
$134.00 on amazon
-charge controller type, cost?
-Cables and wiring cost?
-solar panels type? And cost? And wiring?

Bluetti 180ac is $799.00 all in from amazon.
Am I missing something?

Battle Borns are the most expensive and heaviest you can buy.

A 26 pound, 100Ah Renogy can be purchased for under $500.

A 22 pound, 100Ah ExpertPower can be purchased for $350.

If you use a DC-DC charger that accepts input voltages from 8V - 18V, would you need a seperate charge controller for solar panels?

The Bluetti AC180’s 12v output is limited to 10amps. A small 45lb thrust trolling motor draws 40amps at max thrust and only draws under 10amps at the lowest speed.

And the AC180 is still not suitable for a wet environment without some sort of case which adds to its cost.