Best automotive replacement voltmeter gauges according to redditors

We found 58 Reddit comments discussing the best automotive replacement voltmeter gauges. We ranked the 20 resulting products by number of redditors who mentioned them. Here are the top 20.

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Top Reddit comments about Automotive Replacement Voltmeter Gauges:

u/Raptor01 · 13 pointsr/GoRVing

The 6v golf cart batteries from Costco or Sams Club are what people usually recommend. I have them and they work well.

Also, get one of these: Single best upgrade I've done to my trailer.

u/WageSlaveEscapist · 4 pointsr/vandwellers

Dangerous as is, the battery needs a large main fuse and a manual disconnect switch

Your inverter and fridge aren't fused.

10 gauge wire is not enough to run a fridge and an inverter I would suspect. Also, you might want to run the fridge and inverter on its own, proportionally sized fuse; that way the fuses don't have to be so massive, requiring less potential sparks and fire to blow the fuses. As it is, there's no fuse, and the inverter and fridge share the same cable; the most load hungry devices. That means the cable needs to be double thick from the battery to a bus bar, to the fridge and inverter. Otherwise you will have considerable voltage drop or possibly even melt your wires and cause a fire.

Same thing for the solar charge controller. According to this chart: you can only go 3.5 feet before you get more than 2% voltage drop with 10awg and 30amps - and it says that no more than 2% is acceptable. This might help:

Also I see no battery/amp meter. This is limited to 100a but you get the idea:

And brokedown is correct, you can't just leave different types of batteries always connected whenever the engine is on. You need to disconnect it either with a programmed ACR or manually.

u/GotMyOrangeCrush · 3 pointsr/MechanicAdvice

The first thing to do is get the alternator tested and ideally monitor the alternator output voltage with one of these.

Voltmeter you plug into cigarette lighter plug:

I would bet the alternator is failing and it's getting intermittent. Nissans tend to light up both the brake and alternator light when they lose power.

u/[deleted] · 3 pointsr/vandwellers

How about something like

If your not up to wiring something in.

u/jacco1995 · 3 pointsr/vandwellers

Ran an electrical system in my Subaru with an auxiliary battery charged off the alternator.

80 Amp isolator relay (switches charging on while car is running):

100AH 12V AGM battery:

2Ga Wire running the length from the Relay in the engine bay to the battery.

Kinda Extra things:
Kill Switch:
100A inline Fuse
Multimeter (read current voltage, Amperage, etc):

u/FightsWithFriends · 3 pointsr/VFR

I added a voltmeter. It's easy to glance at it from time to time just to make sure all is well with your charging system. One of these with USB outlets is very handy.

u/lookitsaustin · 3 pointsr/vandwellers

You're most welcome! I bought the following:

4x100W Panels

Panel Mounting

Solar Panel Connectors

Tool Crimper

Assembly Tool

Panel Connectors

Power Information

CTEK Charger

CTEK SmartPass

200ah AMG Battery

Fuse Block

300W Pure Sine Wave Inverter

LED Strip

Dometic 35 Fridge

I bought all these items with research into my solar needs and following the advice from here in the vandwelling subreddit and also information I gathered from Amazon. I am probably doing a bit of overkill on my solar setup but I thankfully have the money to do it and don't want to mess with adding anything later.

I will have to do research myself on how to combine the four panels into the battery but that will be a few weeks away so I haven't done much in that area. I do plan to buy 10GA wire from Lowes and use the crimping tool and connectors to form my own wiring harness so it will be clean looking. \

EDIT: Adding info.

u/Tim_The_Enchanter · 3 pointsr/GoRVing

Yeah might be a bum meter then.

You can get something super cheap just to keep a better eye on things.

u/user865865 · 3 pointsr/microgrowery

Nice work, this is like a bigger, better version of my light with 1' Q strips and a mix of spectrum. I also oversized mine some, 150 watts total in a 2'x2', and have it so I can turn on and off each group. I'm using just regular switches for the groups and I have to adjust the pot manually to keep the power where I wanted it using one of these to measure. Did you go a more advanced route? I'm working on upgrading and controlling everything via an arduino and using relays to turn the light groups on/off and for autowatering and a digital potentiometer for the % power.

I finished one grow with my light at full power in flower, but ~40 watts are side lighting, 10 watts per corner. My light is only around 10"-12" from the tops, and the side lights are only a few inches away. I didn't see any big advantage to the side light, I'm not sure if I'm going to keep them, but I'm using them again this grow. Maybe I'll move 2 up top and keep 2 low and see what the different sides look like.

I'm curious to try to learn more about if this is wasted energy and if so, how to tell

u/agtwork · 3 pointsr/GoRVing

Hi there,

I had this exact setup for over a year while I lived in a camper while going to school. They were nice enough to just let me park in the school's parking lot. Not sure they knew I was living there, but whatever.

Anyway, I had a BP 150W panel and two 6V deep cycle golf cart batteries hooked up in series to an automotive inverter. I also got a voltage isolator hooked up between the truck's alternator and the rig batteries. This allowed me to charge all the batteries without letting any voltage difference wreck the battery I use to start the truck.

My uncle is a sheet metal worker, and came up with a way to mount the panel flat on the roof and make it permanent and water proof.

Everything was controlled by a SunSaver 20 solar controller. I hooked up the house lights to the rig's built in 12v transformer in parallel to the solar panel.

I also bought an altoid tin voltage display and hooked that up. I could then keep an eye on how much I was using to make sure I could scale it back or feel safe with an all-night gaming session on my laptop without worrying about frying my batteries.

Anyway, I figured out based on my usage that I could run the batteries for about 11 hours before reaching redline voltage.

Connections between batteries and the line from the alternator to the controller was all 00 gauge wire. and 10AWG everywhere else.

If all you're hooking up is a 12V water pump, you can hook the leads for it directly up to the solar controller's hot bus. You might also consider breaking the hot bus out so you have more places to attach 12v appliances, like a fan.

u/tchmnkyz · 2 pointsr/PowerWheelsMods

Parts list:

Motor and drive train combo: 2 x 550 30000RPM Gearbox with 12V Motor,Electric Motor with Gear Box for Kids Electric Cars and Motorcycles High Speed RS550 Drive Engine Match Children's Ride on Cars

Transmission to wheel adapter: Transmission Gear External Gear Accessories Connect Gearbox Motor and Wheels for Kids Powered Ride-Ons, 550 Gearbox Accessories Kids Ride On Car Replacement Parts E

Variable speed controller: RioRand 7-80V PWM DC Motor Speed Controller Switch 30A

Connectors: Amass 10 Pair XT60H Bullet Connector Plug Upgrated of XT60 Sheath Female & Male Gold Plated for RC Parts ...

Spade connectors: Supco T1112 Quick Disconnect, High Temperature, 12-10 Gauge, 1/4" Female Tab (Pack of 15)

Battery terminal:

Voltage meter: MICTUNING MIC-VM DC 12V LED...

Note: no affiliate links. All straight links!!!

This all started off with my wife saying that Lightning was a little too slow! I said no problem I got this.

So my first step was to investigate what was the best way to go about this. After a while of researching the best way, I realized that they are more or less oversized versions of my rc cars that I race. With that in mind I was able to do everything.

I started the conversion using just one of the motors. This was so I could make sure I was mentally doing it all right. While the transmission was close to the stock one, it was not a exact fit. I ended up having to trim away some extra plastic and make the opening larger.

Now that the motor and trans is in for the right side I had to start looking at the wiring. The wiring that is in there stock was 18 gauge and while technically will handle the 18v I wanted to be sure we did not melt any wires. I swapped it out one by one using the same 12 gauge wire I use in my RC cars.

The first wires I did was the battery connector. I found the connectors online and used a epoxy putty to make the socket. This ensures the connection is good to the battery.

I then proceeded to replace wires in the harness one by one till they were all replaced. Once it was all setup stock it was time to add in the speed controller. This allows me to turn the speed down (by adjusting the voltage.) I put it online between the battery and the rest of the wire harness. I did it here because it was not able to handle flipping the polarity for reverse. (Popped a fuse finding that out lol. )

Once this was wired up I was able to add in the “fuel gauge”. I put it in what is the “gas cap” on the car. This is a simple dc voltage meter. Nothing fancy here.

Once all that was wired. I needed to make a “Y” splitter for the motors. I know this puts them in parallel all the time and down the road I might change that but for now just forward and reverse was good enough.

Since this car was a single drive motor previously I had to completely make a new hole for this second motor. This was a bit simpler then making room for the first motor.

One thing to note on wiring the second motor. You will want to do it in reverse of the first one as it is spinning the opposite direction of the first motor.

After this was done they only thing I did was relocate the dial for the speed controller from on the speed controller to on the back of the car under the rear fender. This was so I can adjust it without having to remove the seat to adjust it. One thing I may still add is a master power switch. I know this car has one but due to positioning I had to put the battery meter before that switch.

One thing that is still a work in progress is I bought a mltoys brake reduction system. The problem is I was not sure which wire it should go to. This is not the typical plunger switch gas peddle. It is a 6 poll rocker switch. Once they get back to me with that I will get it installed so it is not as jerky on starts and stops.

u/MangoMan6 · 2 pointsr/electricians

Usually that's the case. But for this specific amp meter it needs to be on the ground. I tried it the normal way, and it would just give gibberish readings. It's really bizzare.

A bunch of the reviews are complaining about it

I think the ampmeter works by measuring the voltage change over a fixed resistance.

Edit: Just tested. Anything after the shunt isn't measured. There's probably some sort of correcting it does to take into account the load after the shunt. Probably so it doesn't measure itself. I dunno.

Edit 2: it's included wiring diagram

u/partybarge12 · 2 pointsr/popups

Ac meter: bayite AC 80-260V 100A BYT-VAEM-034 Digital Current Voltage Power Energy Analyzer Meter Ammeter Voltmeter with Open-close Current Transformer Split Core CT

Dc meter: bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt

u/mandreko · 2 pointsr/Multicopter

If it's useful, I too just got started, and built a similar drone. When it came to charging, I had to read a ton of stuff. Here's what I did (all non-referral Amazon links. you may find cheaper on banggood if you want to wait forever):

ISDT Charger

12v Power Supply

Balance Charger

To connect these up, it may be useful to have some extra XT60 plugs since the power supply won't have XT60, and neither does the balance charger.

With these optional parts, I was able to make a nice looking (and more safe) charger from the power supply, along with a 3d print available here


Power plug

I found this to be a pretty fun project, and wasn't as expensive as some options I saw on HobbyKing or everywhere else. To be fair, it wasn't the cheapest option either.

u/Marz_Barz · 2 pointsr/beetle

Qunqi 12V DC Digital Voltmeter + Dual USB Charger Power Socket + cigarette lighter Three Hole Panel For Boat Car Phone Tablet W/ Wire

u/SoberBrent · 2 pointsr/CarAV

I made a Boombox out of a pair of coaxials I had laying around


spectrum analyzer


solar panel

buck converter

battery mount

I have a surplus of m12 tool batteries as well as some coaxials laying around I figured I’d make a portable speaker

With solar panels most output well over 18 volts. Which is fine for that amplifier but not for the battery. With a buck converter it takes it down to a more useable voltage for the lithium batteries.
If you wanted to run something like this on grid power you would need something like this I had planned on getting a 12 volt power supply like the one here later for home use but since with one 9AH lithium battery I have well over 12 hours of listening before the battery needs to be recharged/ swapped out.

Edit: also using this to monitor solar output

u/Vic_Rattlehead · 2 pointsr/motorcycles

With an older bike like that, who knows if any manufacturers rated amperage output is going to be accurate anymore. This is what I did on my 95 CB1000 when I got it all wired up.

The first thing you're going to want to do, before you start adding any electronics at all, is make sure that your rectifier/regulator is doing what it's supposed to. The best way to test that is use a voltmeter to measure the voltage across the battery terminals when the bike is off. Ideally, you should see a voltage greater than or equal to 12.6 volts. Next, start the bike, and measure voltage at the terminals again. You should see a voltage somewhere right around 14 volts plus or minus a couple tenths of a volt. If your "running" voltage is lower than this, you may want to look at the health of your rectifier/regulator.

At this point, if everything looks good, you can start adding on to the bike! To start, you will need a "sense" wire to tell when the bike is running, a fused connection back to the battery terminals so that if something fails, your bike doesn't catch on fire, and a way to distribute the power to multiple devices. There are a bunch of great aftermarket devices that do all this in one package, but they are generally a bit expensive. If you make something yourself, please make sure you do lots of research so you don't burn your bike down. Hell, you should probably do research anyways.

Just make sure that whatever you are adding, you're not causing the running voltage of the bike to drop too far below 14, which would signify the regulator isn't able to keep you fully supplied. Even if everything looks good at first, extended riding may expose failures or weakness as circuits heat up, heatsinks saturate, and old, soft wiring insulation decides it doesn't want to insulate quite so well anymore. Just make sure that you check your system voltage every once in a while, and you should be fine. You could probably mount something like this on your handlebars if you're particularly paranoid

Happy farkling, and feel free to ask questions!

u/dougmc · 2 pointsr/radiocontrol

With this device, probably not, though you could try delivering all the voltage to the inputs for the first cell and see what happens. (And note -- it might fry.)

Buy a new multimeter -- the $3 ones at Harbor Freight Tools work just fine for this.

You could also buy a few of these, or something similar -- these will measure anything from 4.5 volts to 30 volts. There's lots of variations of these, and some are small enough and use so little power that you could easily mount them into your planes and other devices as built-in voltage meters.

u/looperplanes · 2 pointsr/stratux

I mounted one of these with doubled sided tape right below the cig lighter ... put ring terminals on it with a 1A or 2A inline fuse - one goes to airframe one goes to positive post on cig lighter. Easy peasy.

Take it off at annual if you have a dick bag IA - but mine has gone through check rides and annuals with no problem. Guy even commented - "that's nice".

u/CaptSnap · 2 pointsr/skoolies

First, You need to add up all the energy youre going to use in an average day. This is critical and no one else can really do it for you.

Theres a couple of ways to do this. You can buy a kill-a-watt meter and plug a power strip into it and then run everything you would want to run in a day off of it. This is it on amazon It will tell you how many watts everything has used.

Or you can go to a solar calculator on the web.....type in all the things you will use and what their rated wattages are. If you dont know them you can find them ..usually...on a label on the back near the power supply of each appliance. Or just google and use the larger number of their examples. Type in their wattage and how long you will use them. This too will tell you how many watts youre likely to use during a day.

Second, you need to size your solar array and your battery bank.

Lets say in your calculations you find that you use 2000w a day (2kw) that would be about 60kw a month if you want to compare it with your electric bill (which is pretty low but not unrealistic since you arent using a/c or any large appliances). For solar panels the math is pretty simple. If you get 4 hours of direct sunshine you would need 500w of solar panels to get your 2000w for the day under ideal conditions and assuming no loss. (never plan for ideal conditions and never assume zero loss but you get the idea) If you think youre going to get 8 (youre not) then you just need 250w....and so on.

You will probably never achieve this, I would shoot for 60% more solar on the bus than you think need on paper. For this example I would do my best to get 750 to 800 watts of panels. It is fair complicated and very build specific to try and calculate how much loss you will incur in your wiring and in panel placement. Since you can only have two panels the simplest and most elegant solution is to just buy panels that cover as much of the space as you have left as possible.

Panels also are never as efficient as they are the first year. If you size perfectly this year in a year or two you will be undersized.

For batteries you have to consider amp hours. Watts are amps * volts. Batteries are usually 12 v. Lets continue our example that you use 2000w a day and want to have enough reserve power to cover a full day. 2000w at 12v is 167 amps. An amp hour is one amp or one hour. We can take our 167 amps and know that you need 167 amp hours because youre using it over time. Im oversimplifying but thats the smallest amp/hour rating that will suffice. A good rule of thumb is to never drain lead acid batteries below 50% so now you need a 330 amp hours battery bank at the minimum. As an example that means you would need between 3 and 4 of these For lithium ion I think its 80% so thats 210 amp hours of lithium ion.

Your battery will never be as good as it is the first week so in a year's time neither of these banks will provide enough reserve energy if you just do the minimum required right off the bat. You will have to overbuild to account for this or add later.

If you want to work backwards then its a little less elegant. Lets say your coffee maker is 5 amps but its rated at 110 V thats 550 watts. Lets assume you use it for 15 minutes so thats ~138 watt hours. Your inverter will need to draw (138 watts divided by 12 V) about 11.5 amp hours out of your battery. If you have a 100 ah battery bank, that gives you 50 ah effective use...that 15 minutes of coffee making just used over 20 percent of your battery.

Charging your house batteries off the alternator can be very simple. This is what I used Put a switch in the cab and run a wire to the small terminal. When the small pole is energized it will connect the two larger poles. Wire one pole to one battery bank and the other pole to the other battery bank, use thick wire for the large poles 2/0. When the small pole is not energized the two poles will not be connected. When you want one bank to charge the other bank turn your switch on. When you want one bank to not drain the other bank, turn your switch off.

Im partial to this brand but you may find a cheaper one.

There are dozens of gauges that will tell you your battery voltages. Here is one example if you have everything wired correctly when you flip your switch to connect your two battery banks you should see their voltages come together.

u/ontheleftcoast · 2 pointsr/TeardropTrailers

This is the meter, hookup is pretty easy. bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt

u/Shortysprinter · 2 pointsr/vandwellers

This style of meter is useful.

Just run each component individually to get current draw. Cannot vouch for accuracy but numbers I've measured match product specs, so there's that.

u/Thatguybehindglass · 1 pointr/MechanicAdvice

I have a cigarette lighter voltage meter.

No idea how much amp draw there is. Im also not familiar with a lot of this. Wish I could provide more information.

I run my stereo mainly driving. But I occasionally park and blast it to show off. When I turn it all the way up the voltage drops too about 9 or so. Of course I don't let it run for long, as that can cause damage to speakers.

According to my cigarette volt meter, my battery stays steady at 14 volts unless I turn it all the way up. But I usually only turn it up to 15-25. (max being 62) and that drops it to around 13-13.9 volts.

u/VE7DAC · 1 pointr/amateurradio

Hello from across the strait! Victoria here.

No worries, here are the parts I used:

Fuse Box
[Switches (available in other colours, look at the similar items)] (
12V Lighter Ports
Battery Charger (external)

I snagged the last battery charger they had in stock for $50, looks like the price available now is significantly higher. I'd recommend shopping around. Everything else is a basic part, and of course could be easily replaced. Just make sure your switches are rated for the amperage you're going to draw from them, and that the fuses are rated the same or less than the load you put on.

Best of luck, and don't forget to post your build when you're done!

u/NYCvanMan · 1 pointr/vandwellers

This is what i use to monitor my power usage. It has an alarm feature that goes off when you hit a predetermined/adjustable voltage level.

bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt

u/chasw98 · 1 pointr/GoRVing

Look at this one also. Voltmeter.

u/unisonnn · 1 pointr/electricians

Btw, i did buy this device with my system to monitor battery levels and draw.

u/rypajo · 1 pointr/overlanding

Fridge consumption should be way under that. It sits idle most of the day. The 5.5a is a max rate I believe. At the bottom of this article, they address it a bit.

In theory, the solar should be more than enough I think. I think I am going to buy a meter or two so I can measure amp draw from the accessories and another to measure panel production. I wish there was a unit that just displayed both but I don't see one.

u/c00ki3znkr34m · 1 pointr/AskElectronics

Okay, would this do it?

Attached in the same way like you recommended?

Also, I have no idea how much current will come out of this thing. Is there any drawback to getting a larger one?

u/gybemeister · 1 pointr/SolarDIY

I have an Outback Flexnet DC in my main system and a Victron BMV 700 on a second smaller system. I would suggest you buy a Victron BMV 712 Smart (1) which comes as an all inclusive package with all that you need to install it. This one also has Bluetooth which makes it super cool with charts on your phone. If you are on a tight budget you can go for their simpler non bluetooth ones. Mine cost around 100 GBP a few years ago. There is also a 15-ish GBP option in Amazon but I don’t know how well it works (2).

The Victron comes with a shunt which you connect to the battery bank negative pole and you connect the inverter and the controller to the other terminal of the shunt. You want to make sure that nothing else is connected to the negative pole of the battery so that all energy crosses the shunt. Then the monitor itself is connected to the shunt (it comes with full instructions). You want to make sure you do this after fully charging your batteries.
A monitor gives the correct state of charge of your bank which is miles better than guessing from the battery bank voltage.

u/SVKissoon · 1 pointr/vandwellers

Ive found this on Amazon:

Anyone have thoughts on this? Ive you read the reviews, in reference to van power, they're generally positive.

u/B0NK3R5 · 1 pointr/electronics

Cool. For batteries, I found this

There's shipping, but still substantially cheaper than

Even though that would be 4 more AH.

I am also looking at this just because

u/CumFairy · 1 pointr/CarAV

Are you talking something like this?

u/GarThor_TMK · 1 pointr/carmods

You could get something like this to just split the outputs, but if you actually want to mod your car I think you are actually looking for something like this or this...

Not terribly sure what your dash looks like, or which button panels are available to tap into, but that's probably where I'd start... >_>

The wife has something like this in her car, but I kinda hate it 'cause it takes up one of the cupholder slots... >_>

u/creekyoffgrid · 1 pointr/SolarDIY

There are a bunch of devices like this. For ac and dc. Amaz, ebay, etc

My solar controller gives me the data via the web. I use one of the above for monitoring what goes to the inverter. i could put in a ac ammeter. hmmm. Probably will at some point.

you would put one between your solar controller and batteries ... and another between battery and inverter.

not sure how to send the data to the web.

u/chriz3268 · 1 pointr/vandwellers

Good stuff, thank you all. One more question though, regarding the battery monitor, in order to monitor the discharge rate and not go below 50%, do I need a victron BMV-700 ($150) or can I just use this bayite meter:

u/soloxplorer · 1 pointr/CascadianPreppers

Something to consider with a PVC shower, is supplementing your heat. Best way I've found to do so is to use a heating element like this one and couple it with a temp controller. This runs off 12v DC so you'd have to take into account electrical capacity, but I figure I could run that while on the move so the vehicle alternator takes the load, or from an onsite generator if you're in a fixed location.

Disclaimer: I have not run this yet, I'm still in the planning phases of a PVC shower. This was found through research.

u/drumking15 · 1 pointr/microgrowery

bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt

That's what I used. I disassembled my power cord where it meets the wires coming out of the power supply. I had the current ring between the power wire. Was pretty simple to do and it keeps track of current and power and total power used.

You'll be surprised that the dial to output won't be linear.

u/Soap-ster · 1 pointr/electronic_cigarette

Thank you for putting so much time in for me. You have answered my questions! I can now finish buying the stuff I need, and get to building!

I'm going to leave out the voltage switch and simply have it display the voltage when the trigger is pressed. If I find a display small enough, I'm going to try to find a 6 pin connector and have the display on the hand-held box. I found a great price on nylon sleeving HERE. I'm not sure what size, I'll need, so I'm going to buy the 1/4in and the 1/2 in.

As for the display, I think THIS will do.

u/david4500 · 1 pointr/OpenPV

> I'll order the screen and magnets from Amazon: OR

> those screens... I think they're too big.

u/suspire · 1 pointr/SolarDIY

Battery Meter. Ive been toying with making one of these for a friend after I finish upgrading my camper. Someone else may be able to offer some more insight.

u/Wipples · 1 pointr/leaf

Funny thing is I use to have to test my 12v battery with my old ICE car (Alternator problems) Heres a link to one →

u/sillycyco · 1 pointr/firewater

You want mating socket and plug, the two you have there are not matching.

This controller is a bit nicer and it is cheaper. It comes with a box as well. I'd add in an ammeter as well, so you can see what power you are running at.

u/tatertom · 1 pointr/vandwellers

Sort of. There's sort of a progression going on. It's a good idea to ensure you can cut the power between the two manually as a safeguard.

I used this
last time with a fuse on each battery, and just kept the accessories live to the house battery full-time. Turned it on when I wanted to charge or the odd case of boosting my starter battery from the house. Dead-simple hook up, I just had to pay attention to when I should have it on or not. Mostly cut it on before I start the vehicle, watch the dash voltmeter to know when everything's charged, then cut it off before I start using the house without the motor running.

I'm getting this one next time to replace the one above. I'll have the common on the accessories, and be able to run them off of the starter, the house, or both. "both" would also be used to charge the house off the alternator, and I'll have it there almost all the time, with the addition of a VSR (below). It also has an "off", in which nothing is connected to anything. You'd still want to wait until the engine is running to re-charge a dead house battery, and switch it to only "2" to keep from draining the starter battery, unless you install one of the next two items.

This makes a nice addition wired right alongside either switch. Tells you how much juice each battery has.

To keep everything 100% un-screw-up-able, this is going to go between my starter battery positive and my new manual isolator switch in back. If either side gets to charging voltage, it will connect to the other side. That means the alternator will always charge the starter battery, but also charge the house battery AND if I connect a charger to the house battery (like a generator or plugging in to shore; solar that fits on a van would take several days to charge a battery from dead to van-crankable), then it will automatically charge and maintain the starter battery, too. Neither can drain the other past the point it wouldn't crank the van.

Charging relays are much cheaper than a VSR, and are automatic in a more rudimentary way. This will do the job fine for most cases, and is a little less expensive than a VSR. The big lugs on it hook up just like the two on the VSR above, except it's not automatic - you hook the small poles up to stuff to tell it when to connect the big lugs. The small positive goes to the other, smaller wire going into the alternator, only allowing it to connect if the alternator is charging. The small negative can go straight to the large negative, but I'd run it through a small switch in the dashboard somewhere (and the other side of that switch back to the large negative lug) to allow me to disable charging house battery off the alternator. it's a decent blend of manual and automatic control, with a relatively tiny price tag. This pretty much needs to go under the hood, though, whereas the VSR could actually go in the power center or under the hood. Remember that either would go on the 4 gauge between starter battery and rear isolator, if present; it's the longest fat-wire in the whole system. some people skip the manual isolator switch altogether, and just go with a VSR or charging relay.

Only because I happen to have one of the first switches linked here already, I'd install it between the large lugs of the VSR or charging relay, to bypass it manually. If I didn't already have one, I'd just count on using a set of jumper cables to do that in the rare case I should need to turn that switch on.

u/DidYouReadThatThing · 0 pointsr/CarAV

Oh haha uh any shit off eBay would work but not very accurate or a name brand like autometer has a digital round meter.