12v battery low voltage disconnect

[GeorgeRa]

Originally Posted by booster

I am not certain the 150v rating would protect you, as it steps that down to run itself, I am sure, and without the voltage control the internals that should see 12v or so could see much higher even parallel, ours will run over 21v open circuit on the panels.

My panels are about 21V open circuit as well, you probably right that 150V rating could provide limited protection if there is no active charge controller circuit by 12V. I will make sure to turn them both on or off in the garage. Thanks for this inside.

Going on tangent, just noticed that there is spelling software installed on this site, great news.

[Roadtrek Adventuous RS1]

Originally Posted by booster

So are you saying that the Zamp has a low voltage battery cutout and you run the coach loads off it all the time, or was this just another off topic jaunt to talk about whatever of yours?


On topic a bit, I seem to remember a thread a bit ago where someone was wired up through the load side of the solar controller and there were some issues with it that showed up. I don't recall how it was resolved or if they just moved the loads.


Low voltage cutouts based on normal discharge use are very rare, I think, for lead acid systems. Many have a low voltage cutout tied to an inverter, but it just shuts off the inverter.

To the best of my knowledge..... this is a fully integrated system requiring nothing.... charge controller and battery shutoff means it will not overcharge the system...

I had this professionally installed by a mobile electronics shop who is a dealer for Zamp.... single source solution, zero maintenance.

Only need to worry about a rock or other object falling on the roof which could damage the panel....

I keep my rig parked outside in the driveway... plenty of sun.

[booster]

Originally Posted by Roadtrek Adventuous RS1

To the best of my knowledge..... this is a fully integrated system requiring nothing.... charge controller and battery shutoff means it will not overcharge the system...

I had this professionally installed by a mobile electronics shop who is a dealer for Zamp.... single source solution, zero maintenance.

Only need to worry about a rock or other object falling on the roof which could damage the panel....

I keep my rig parked outside in the driveway... plenty of sun.

Did you even bother to read the question or the title of the original OP question????


It is asking about A LOW VOLTAGE CUTOUT THAT WILL SHUT OFF THE BATTERIES IF THEY GET TOO LOW, it has nothing to do with the charging side of you solar, but some would have a shut off if connected to the load side. It has nothing to do with who installed it or if your van sits in the sun. READ WHAT IS ASKED AND ANSWER THAT, NOT OTHER STUFF.



Please, if you don't understand or bother to read the questions don't answer them claiming your systems do all that and more. You will mislead whomever asked the questions and put garbage information in the thread for all eternity to get confused by it.

[Roadtrek Adventuous RS1]

Originally Posted by booster

Did you even bother to read the question or the title of the original OP question????


It is asking about A LOW VOLTAGE CUTOUT THAT WILL SHUT OFF THE BATTERIES IF THEY GET TOO LOW, it has nothing to do with the charging side of you solar, but some would have a shut off if connected to the load side. It has nothing to do with who installed it or if your van sits in the sun. READ WHAT IS ASKED AND ANSWER THAT, NOT OTHER STUFF.



Please, if you don't understand or bother to read the questions don't answer them claiming your systems do all that and more. You will mislead whomever asked the questions and put garbage information in the thread for all eternity to get confused by it.

OK thanks.. I thought these were related... apparently NOT...

[ks@yvr]

I use a Blue Seas low voltage disconnect. You can set the low voltage limit you want in .2 volt increments. Works great and saves house battery. See https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[booster]

Originally Posted by ks@yvr

I use a Blue Seas low voltage disconnect. You can set the low voltage limit you want in .2 volt increments. Works great and saves house battery. See https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Those are nice units and would work fine. Be aware of the 65 amp limit though, as many alternator systems will be higher than that. Even the mid age AGM Roadtreks with a separator are at 80 amp breakers. The Blue Sea will have some surge capacity above rated, and likely would survive that much over for quite a while, but if you get up into the 100+ amp range it would likely overheat.

[michaelingp]

I watched the video of the Blue Seas disconnect on Amazon, and it's mostly concerned with keeping your house load from running down the van battery so the engine won't start. Most RV's have isolators or separators between the house and van batteries to protect against that.

So, I ask the experts here, can a device that only senses battery voltage really protect you from discharging your batteries too low? I had such a device once, and it wasn't useful. If I ran a heavy load (even briefly), the battery voltage would drop low enough to trip the disconnect. If I set the device to a low voltage (one of the Amazon comments says they set it to 11.3 volts), then a small load (like the detectors) would destroy the battery long before the disconnect tripped (I think your battery would be toast if its (almost) no load voltage remained at 11.3 volts very long).

Am I missing something?

[booster]

Originally Posted by michaelingp

I watched the video of the Blue Seas disconnect on Amazon, and it's mostly concerned with keeping your house load from running down the van battery so the engine won't start. Most RV's have isolators or separators between the house and van batteries to protect against that.

So, I ask the experts here, can a device that only senses battery voltage really protect you from discharging your batteries too low? I had such a device once, and it wasn't useful. If I ran a heavy load (even briefly), the battery voltage would drop low enough to trip the disconnect. If I set the device to a low voltage (one of the Amazon comments says they set it to 11.3 volts), then a small load (like the detectors) would destroy the battery long before the disconnect tripped (I think your battery would be toast if its (almost) no load voltage remained at 11.3 volts very long).

Am I missing something?

You are not missing anything at all, that is what can happen. Same thing with the low voltage cutouts for big inverters that shut themselves off from voltage drop, but they don't kill the entire system like a low voltage cutout would.


A lot depends on battery bank size and type and load sizes. Wet cells will be worse for voltage drop with load, small banks worse than big, and if you never have big loads is better.


I think I could easily see a system that use a low battery (voltage) cutout like shown set at a low load battery saving voltage, but with a manually controlled switch or relay around it for when actually camping when it is much less likely that you will miss that your battery is nearly dead.


The other option would be to control a big no power us bistable relay from a battery monitor like a Victron that has a SOC output relay if you set it that way. Of course the monitor itself would take some power so I don't know if you would want to shut that off with itself, or not, in long storage. It would work good for camping time as you need the monitor anyway, and would easily cover the accidental forgot the power on when we got home battery killing.

[ks@yvr]

We are using our Blue Sea low voltage disconnect on the house side of the circuit beyond the disconnect switch and the charge inverters. We have it inline with the house fuse panel so it shuts down the fuse-panel power to the lights, TV, DVD, furnace (the biggest draw) effectively automatically taking the camper systems offline before the battery drains too far. There is an override switch too but really no need to have to use for the house systems. The system battery charging options have been left as is (vehicle alternator, 110 V charge inverter, solar panels and disconnect switch); we are protecting the battery from being drained too far and our largest draw items are a 300 watt 12/110V inverter and the furnace fan which don't come anywhere near the max current draw of the disconnect device. The fridge is 3 way usually on gas but if it was set on 12V it would also run down the battery. We are using it to protect the battery from over discharging say at night or if away from unit and not monitoring properly before recharging from the alternator, shore power or generator. We have set our camper up to be pretty frugal on power draws so that we can boondock. We recently replaced our much smaller worn out house AGM battery with a larger quality 200 Ah AGM battery and wanted to make sure we don't over discharge it and having to prematurely replace the battery. The system is not overly fancy and wasn't intended for high current draw (say large inverter), was relatively inexpensive to setup and just works for us. It is a relatively simple inexpensive solution that I haven't seen mentioned on the RV forums and it works.

[GeorgeRa]

The Blue Sea Low Voltage Disconnect relay is only 65A and I think it is not bi-stable.

I am not sure about the value of low voltage disconnect for house batteries, just added complexity. During camping a good battery monitor should suffice, for long time parking disconnecting batteries is simple.
I use Intellitec manual bistable relay for years. Locating the remote in convenient location is important, on my previous RV I could reach it from outside though opened door, in my current van it is on the overhead cabinet at the sliding door.

I wouldn’t use Intellitec again, I am on the second one in the van, the first one failed. I often needed to turn it ON multiple times to latch. I replaced it with a new one, took old one apart, cleaned copper contacts so now I have a spare. See the pictures.

Blue Sea battery disconnect is using silvered contacts which are likely more immune to corrosion than grease coated copper on the Intellitec.

[booster]

We have been lucky to this point that our intellitec is still working well after a decade, but if we do have a failure we will certainly put in a better one, to. We have the Blue Sea one shown in the previous post to disconnect or alternator charging that can go to 300 amps, and it has worked very well.

[pcpowernet]

We have experienced roughly the same as RS1. In May we started our trip to Cincinnati with the Roadtrek. Engine light, limited restarts, so to the dealer for a three month long shop time. Took our car - 2017 GMC Acadia that is just as comfortable. A wash as far as trip expenses. The difference is in not having a bathroom all the time, not having to trek into a motel with your stuff every night, having a much better variety for breakfast than Holiday Inn Express breakfast every morning. The advantages of the car as RS1 relates are true, BUT, it also depends on what you would like to do on any one trip.
Needing a car at the destination is one requirement, such as needing to transport kids is just one. Camping at nice locations, not eating at restaurants for every meal or the convenience of just having a nice nap during the day are in favor of the RV.
I could go on, but it boils down to the particular trip goals, not just the expense.
We just took the CS Adventurous to Denver to our kid's new home. If we had to do it over we would have taken the car. Weather, cold temps, avoiding snow, etc., didn't make the RV trip as enjoyable as it would in the summer. It took 5 days for a car trip of 3 days.

[GeorgeRa]

It seems as a car vs a B-van discussion deserves another thread so this battery disconnect thread stays on track.

[weather command]

Nice point you're trying to prove!! I can absolutely tell you that my class b bed is twice as nice as any hotel bed.....is it worth that much? Debatable? But, love the lifestyle...hotels 👎

[Rogerp]

Originally Posted by michaelingp

If you're looking for a manual disconnect then there are a number available. My old Roadtrek had one made by Intellitek. My new van doesn't have a disconnect, but it's easy to turn off all the devices that use power, except for the propane detector, for which you have to pull the fuse.

If you're looking for an automatic way to disconnect the battery when it was discharged too low, I think you may be disappointed. Even if you could get consensus of what "too low" means, it would be an expensive device to build since it would essentially have to determine how much energy you've pulled out of the battery since the last full charge.

Try $77.00 on Amazon for blue sky low voltage disconnect, at link below.
https://www.amazon.com/Blue-Sea-Syst...58639735&psc=1

There are lots of these devices depending on max amps it can switch.

[Ph0t0n]

Another option you might check out is this little guy...

https://www.victronenergy.com/batter...attery-protect

The BP-65 is only $40. They make 100A and 220A models as well.

I'm pretty sure that the Victron BMS isn't required for it to work, but not positive. I don't think it's bi-stable, but it uses a mosfet so it just barely sips current.

I understand the logic that says it's an overkill to install a low-voltage-disconnect if you have solar panels... and part of me subscribes to that theory as well, but there are some situations where a Low-Voltage Disconnect (LVD) could still come in handy.

For example, when I first bought my van, I didn't know that the fridge took so much energy that the batteries were unable to run the fridge overnight. Battery dead. Another example is that the solenoid that gets activated to let the alternator charge the house batteries failed without me knowing - while I was driving and running the fridge on DC. Battery dead. Another time I was up late working on my laptop and the laptop drained the house batteries down to 11.3v and without a low voltage alarm I didn't know it until the monitor flickered off. Not dead, but really close to dead.

The last two of those situations would have been fixed with a low voltage alarm. Since I wasn't in the van at the time, a low-voltage-disconnect is the only thing that would have saved the battery for the first situation.

So... is an LVD necessary... odds are that it's not... but then again... $500 to replace two AGM batteries can really ruin your day.

[markopolo]

The Victron battery protect doesn't look to be an easy install in many RV's because you can't pass charging current through it (fire risk if you try). It can only be used on the discharge side.

In many/most RV's, there's a dual use (both charging & discharging) wire connecting the battery to the converter/charger or inverter/charger so it can't be used on that wire.

It could be placed just before DC distribution as long as no back-feed charging is ever used post distribution such as a maintainer plugged into a 12V accessory outlet.

[Ph0t0n]

Ah, that makes perfect sense when you put it that way. I was wondering why I didn't see more mention of it in the forums. Thanks for the info markopolo.

[Nic7320]

You don't want a low voltage disconnect for a battery charger, because when you're in a low voltage condition, you need to charge the battery. But like anything else going to the battery, it should get a fuse, and that fuse can be used as a disconnect when working on the system.

Victron low voltage disconnect devices are very good, but only used for loads. They have a reverse pathway that DOES NOT DISCONNECT, known as a body-drain diode that exists in any MOSFET. The only way to eliminate the body-drain reverse pathway is to add an additional diode or a relay, at additional cost and loss of efficiency, so that is not often done.

[@Michael]

Originally Posted by markopolo

The Victron battery protect doesn't look to be an easy install in many RV's because you can't pass charging current through it (fire risk if you try). It can only be used on the discharge side.

Originally Posted by markopolo

It could be placed just before DC distribution as long as no back-feed charging is ever used post distribution such as a maintainer plugged into a 12V accessory outlet.

Originally Posted by Nic7320

Victron low voltage disconnect devices are very good, but only used for loads. They have a reverse pathway that DOES NOT DISCONNECT, known as a body-drain diode that exists in any MOSFET. The only way to eliminate the body-drain reverse pathway is to add an additional diode or a relay, at additional cost and loss of efficiency, so that is not often done.

I just installed one of the Victron battery protects, and will take note of the advice. It's the last device before the load center, so would only be an issue if I attempt to charge via an accessory outlet.