How do you know when to stop using electrical outlets?

[Nooooooooob1]

Going on a trip and need to charge speaker, GoPros, drone, phones, tablets, lights etc at camp.

Using the DC and AC outlets, how do I know when the vehicle’s battery is getting too low? Can the gauge be used for this? Can I simply hook up my multimeter to the battery and stop at a minimum voltage?

 

[linuxgod]

Indirectly you can monitor the voltage to estimate how drained your battery is. You'll want a multimeter as the little gauge in your dashboard does not have sufficient resolution. As to how low you can go before starting becomes a problem, I'm not sure but I'd definitely be concerned at 50% if not sooner, as you don't want to discharge a lead acid battery below 50% (and if it is discharged that far I don't know how many crank amps it's really producing)

You can also estimate your amp hour usage and work from there. I think @grinchy recently posted that the stock battery was something like 60Ah. So if your goal is to stay above 70% then you have 18aH to work with. Starting adding up your device draw and how long you use them and go from there (i.e. If your iphone battery is 2500mA and you charge it when it hits 20% you'll need to put 2A into it which means you now have 16A remaining).

 

[Nooooooooob1]

Indirectly you can monitor the voltage to estimate how drained your battery is. You'll want a multimeter as the little gauge in your dashboard does not have sufficient resolution. As to how low you can go before starting becomes a problem, I'm not sure but I'd definitely be concerned at 50% if not sooner, as you don't want to discharge a lead acid battery below 50% (and if it is discharged that far I don't know how many crank amps it's really producing)

View attachment 2676697

You can also estimate your amp hour usage and work from there. I think @grinchy recently posted that the stock battery was something like 60Ah. So if your goal is to stay above 70% then you have 18aH to work with. Starting adding up your device draw and how long you use them and go from there (i.e. If your iphone battery is 2500mA and you charge it when it hits 20% you'll need to put 2A into it which means you now have 16A remaining).

Amazing info. Thanks so much for the explanation!

 

[linuxgod]

Now that I've answered as best I could above I'm going to suggest a better option. Go buy a lithium jumpstart pack. Most of them have USB and other port options so you can charge devices right off it when the engine is off, and no worries about depleting the battery. I bought one of these since it was half the cost of the Noco:

Amazon product ASIN B08M41FX48
It's 73wH, which at 12V means it's about 6Ah. If you decide you want to use your vehicle battery to power devices, then the above is a good insurance policy in case you drain it too far...

FWIW if you are just charging devices and running LED lights and low powered speakers etc then either way you'll probably be fine. I have a 100Ah in my trailer, and we run the LED lights, fridge (propane but requires 0.5A), radio, water pump, and device charging and we only use maybe 10A overnight unless we all start taking showers or I run the heat.

 

[TeCKis300]

How are you using the outlets? Do you have a mechanism to enable their function without having ignition in the accessory mode? I ask, because accessory mode is a big draw in itself and it would be worth having some way to turn on outlets independent of the ignition.

To answer your question, easiest way is to use a cig lighter adapter that has a voltage readout. It's better resolution than the dashboard but also has its limitations. Particularly that there is some slight voltage drop at the cig lighter position, depending on draw. These readings always has the battery under some minor load so it's never completely precise (always a bit under) relative to the SOC table posted by @linuxgod. Mix in temperature as another variable. That said, measuring battery reserve is not a perfect science anyhow and it's best just as a general reference.

I would be comfortable running down to ~11.9V (with loads turned off) and having enough reserve to start the car. I personally would even go lower but that can start compromising battery life. Yes to the lithium jumper as always a great backup, if not for yourself but even others. Many also serve as a USB power bank.

 

[Nooooooooob1]

Right now I’m just using them as designed, with accessory power on. I’d love to make them always on or switched independent of ignition. My ideal project would be to replace the factory inverter with a 500w+ non-ignition dependent unit.
Good point with the readout though. I just ordered a hardwired unit from Amazon that I will mount in the dash to keep an eye on the voltage. I was going to just use my multimeter but that actually sounds like a huge PITA every time I want to see what the number is.

 

[1world1love]

Right now I’m just using them as designed, with accessory power on. I’d love to make them always on or switched independent of ignition. My ideal project would be to replace the factory inverter with a 500w+ non-ignition dependent unit.
Good point with the readout though. I just ordered a hardwired unit from Amazon that I will mount in the dash to keep an eye on the voltage. I was going to just use my multimeter but that actually sounds like a huge PITA every time I want to see what the number is.

I know you don't want to hear this, but you should consider getting a battery pack. Even a smaller one. Like Teckis300 says, accessory mode is a major draw and I managed to run my battery down in a remarkably short amount of time just charging things while setting up camp.

Also, the rear inverter is limited by the size of the wire going back there, so you may need to run a larger gauge in order to go to +500w, but if you do, you may consider going even higher than that.

At a minimum, I would get a jump starter like linuxgod recommends. Even if you do not charge things, it provides some peace of mind.

But a small GZ, Jackery, or other battery pack is a good investment as it also allows you to bring the power into camp.

 

[kcjaz]

I would suggest buying a simple battery tester like a Topdon. It’s manual but easy to use. FWIW, I used my Topdon last weekend to test my boat batteries. The voltage table @linuxgod provided above lines up pretty well. I had batteries with about 12.1 volts and the tester said 50% charged. Plenty to start the boat. I like the other data the test provides too though I have to admit, I don’t know how accurate any of it is.

 

[1world1love]

See, my problem is that no matter what tester you get or how accurate it is, it requires you to remember to test and when it is too late, it is already too late. I am too forgetful for that.

You could try something like this:

Eagle Eye 12 Volt Low Battery Alert and Alarm - Batterysavers.com

The "Eagle Eye Low Battery Alarm" triggers when the battery drops below 11.9 volts. This is roughly 50% of the battery's capacity. The resting voltage for a 12 volt battery is actually 12.4 to 12.6 volts.The goal of the alert is to catch the battery before it goes too low and prevent battery...

batterysavers.com

Apparently it only draws .02 amps while active. It alarms at 12.01 volts which would make me nervous, but it is cheap and you can test it before you go.

 

[Dan Higgins]

Now that I've answered as best I could above I'm going to suggest a better option. Go buy a lithium jumpstart pack. Most of them have USB and other port options so you can charge devices right off it when the engine is off, and no worries about depleting the battery. I bought one of these since it was half the cost of the Noco:

Amazon product ASIN B08M41FX48
It's 73wH, which at 12V means it's about 6Ah. If you decide you want to use your vehicle battery to power devices, then the above is a good insurance policy in case you drain it too far...

FWIW if you are just charging devices and running LED lights and low powered speakers etc then either way you'll probably be fine. I have a 100Ah in my trailer, and we run the LED lights, fridge (propane but requires 0.5A), radio, water pump, and device charging and we only use maybe 10A overnight unless we all start taking showers or I run the heat.

A ”yes and amen” on the jump starter. I have used mine 3 or 4 times. Most recently because I used accessory mode too long and killed the battery. I now have one in my wife’s car and gave one to each of our sons.

 

[ArnieC]

I solved the accessory issue by running fused 8 gauge wire back to the trunk and terminating with an Anderson plug. When I want to run a fridge or sit somewhere camping for a few days I plug in a little box I built that has a few 12 volt outlets, a few USB outlets, an ARB plug for my fridge, a volt gauge, and a solar charge controller. When I am just commuting, I unplug the little box and put it on the shelf.

I have not found a need for 120VAC while camping, I do occasionally travel with a small 120V inverter that would charge a laptop and I have used it to charge some Milwaukee M18 stuff for my fans and lights as well.

We find that when we go camping the bulk of the time we do everything from the tailgate/trunk area and dont use the side doors much so it works out very well.

 

[RET2]

I solved the accessory issue by running fused 8 gauge wire back to the trunk and terminating with an Anderson plug. When I want to run a fridge or sit somewhere camping for a few days I plug in a little box I built that has a few 12 volt outlets, a few USB outlets, an ARB plug for my fridge, a volt gauge, and a solar charge controller. When I am just commuting, I unplug the little box and put it on the shelf.

I have not found a need for 120VAC while camping, I do occasionally travel with a small 120V inverter that would charge a laptop and I have used it to charge some Milwaukee M18 stuff for my fans and lights as well.

We find that when we go camping the bulk of the time we do everything from the tailgate/trunk area and dont use the side doors much so it works out very well.

I wander to get away from the tether of 120V.

 

[coleAK]

Don’t charge off your truck. A jump battery and something like this. For ~$100 you can get both and charge the items you mention forever.

Limited-time deal: [Upgraded]BigBlue 3 USB Ports 28W Solar Charger(5V/4.8A Max), Foldable Portable Solar Phone Charger with SunPower Solar Panel Compatible with iPhone 11/Xs/XS Max/XR/X/8/7, iPad, Samsung Galaxy LG etc. Amazon product ASIN B01EXWCPLC

 

[Mago]

If voltage goes below 12V you should stop.

 

[bronc076]

I solved the accessory issue by running fused 8 gauge wire back to the trunk and terminating with an Anderson plug. When I want to run a fridge or sit somewhere camping for a few days I plug in a little box I built that has a few 12 volt outlets, a few USB outlets, an ARB plug for my fridge, a volt gauge, and a solar charge controller. When I am just commuting, I unplug the little box and put it on the shelf.

I am totally stalking your previous posts right now looking for a picture of this setup.

I've considered building a small toolbox or ammo can with an AGM motorcycle battery and some USB ports and maybe a small inverter that I could plug into the truck and charge during the day when I'm driving, then bring into the tent to charge things at night. Would love to see your setup. If you have posted it somewhere can you point me to that.

Thanks!

 

[ArnieC]

I dont know if I ever posted a picture of it - its about as simple as can get. Just a small pelican case knockoff from Amazon, a 4-pin bulkhead plug for two sets of Anderson plugs (1x for the +12V feed from the battery, 1x for the feed from the optional solar) then a Blue Sea accessory panel with an on-off switch, voltmeter, and USB, Cigarette Lighter, and ARB outlets. Put my solar charge controller in the box too.

Next thing I am working on is basically the same thing but this time with 40Ah worth of AGM wheelchair batteries, all mounted in a bigger pelican case. Basically a poor mans solar generator, but built a little nicer because it will have an MPPT controller and be able to provide proper +12V to the fridge, something the Goal Zero lithium units struggle with.