Smart battery isolator

Hi everyone, I need some advice for me and my girlfriends van build project. Especially on the electrical side of things:

We’re thinking of getting solar panels also with a smart battery isolator. Unless a battery isolator is enough alone. this is were we need help.

The question is how fast does a battery isolator charge the batteries?

We will need 110Ah per day, mainly for a 50W fridge and charging phones and other electronics.

I was thinking about getting a 150 to 200Ah battery bank (lithium batteries btw, would like your opinion on that too). But how much driving would be needed to fill them up from 20% to 100%? (just to give us a rough idea of if its possible or not)

We would use a 140 to 150Amp smart isolator.

Thanks in advance !!

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Greetings & Welcome!

110ah per day is a LOT. In comparison, I use 40-50ah per WEEK.

An isolator needs to have a high enough capacity to cover your alternators output, but in the end, it’s your alternator that determines the charging capacity, not the isolator.

If your expected usage is accurate, I would suggest 300ah of lead acid deep cycle batteries. I get mine at junk yards for ~$20 each. My last one lasted over 7 years, with isolator charging only and no solar.

For 300ah of batteries, 600 watts of solar would be an absolute minimum because short winter days, or cloudy/rainy/snowy days severely limit the effectiveness of solar. I have a $99 gas inverter generator and a $29 battery charger for a backup plan instead of solar, and even with solar, I wouldn’t be caught dead without my generator. Depending on Mother Nature can be extremely problematic.

I also recommend that everybody should be set up to survive without any power. I have lights, heat, cooking, and refrigeration that are totally independent of my vans power system. Combined with the option of my generator, I feel pretty prepared. I have been totally snowed in for several weeks at a time, and was stranded for nearly a month when a bridge got washed out. Being prepared has it’s rewards… I try to keep at least a months worth of canned food on board at all times, including canned or smoked meats that don’t need refrigeration, then I always use the oldest, and replace them with newer when I go shopping. That way nothing ever ages out. You can even get canned bread. (I like B & M Brown Bread)


"Tis the season... To make bank selling Christmas Trees!" ~Van_Dweller

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van_dweller, do you have a refrigerator?


Not any more, I switched back to a cheap, efficient, convenient, and reliable, non-powered, upright, front opening, portable ice chest.

In the past I’ve had just about every type fridge out there. The 3-way and the dorm fridges were okay, the 12v compressor fridges sucked and cost me a fortune to buy, then even more in lost food, when they died sometimes within a year, and repair + shipping cost more than a new one even if they were still under warranty. A TOTAL RIP OFF! CHEAP CHINESE JUNK SOLD AT HIGH PRICES!

In a typical year I spend maybe $50-$60 on ice. I usually get a big block for 99¢ and that lasts for a little over a week in the summer and even longer in the winter. Occasionally I have to pay $1.99 for it. I go shopping once a week anyway, so picking up ice isn’t even out of my way. I keep the ice in a separate container beside my food, so my food always stays dry. If I need to add a freezer for a longer outing, I add a regular ice chest and $5.00 worth of dry ice, which last nearly a month. In that scenario, the freezer freezes gallon jugs for my ice chest, so I can stay out for about 5 weeks. If I need longer, I load up a tank and make my own dry ice in a collapsible block sized mold for up to 6 months. With this set up, if anything goes wrong, it is clearly my own fault, and not equipment failure.


"Happy Holidays!" ~Van_Dweller

For the isolator charging batteries it really depends on the type of battery. I am a novice but they way I understand it is you have say 190 amp alternator (this is what I have). Basically your alternator is capable of putting out that many amps. This could be totally wrong but I feel it is capable of putting that many amps back in over the course of an hour. If the it is the same as pulling them back out. That part I’m still not clear on.

You batteries however can only take so much depending on their type and I do not know those numbers, but I do know it is considerably lower than 190. It could be 4 amps it could be 20 but it’s certainly not 190 or the max 150 or your isolator. I read that lithiums at near 20% depth of discharge could suck up the entire 190 amps so you may want to be sure you buy the correct size isolator and be sure you have it fused correctly as well.

Either way an isolator is nice to have and that is all we have ever used. Do not start you van and leave it idle in order to simply charge your battery. That is mega bad for you engine. Definitely invest in some type of battery monitor so you can see what is going in and out and be secure in what power you have. I have OCD and if I didn’t have a monitor I’d have my meter out all day trying to figure out amps based on voltage which at best is really just a rough guess. Renogy and Vectron both have decent monitors.


I don’t generally use any meters myself. I have low battery cut-offs on both my starter battery and my house battery. That prevents over discharging them, and the regulator on my alternator prevents over charging them. I do have an old analog induction style ammeter that I can hold against the cable to tell me incoming or outgoing amps at any given time, but it’s more for troubleshooting than actual monitoring.

I wouldn’t be caught dead though without my $99 gas generator & $29 battery charger for a backup plan. Their normal use seems to be helping others, but peace of mind for my own possible needs is priceless.


"Happy Holidays!" ~Van_Dweller