Battery disconnect...or not?

[vlamgat]

I have my 2021 I-5 28SS with the Explorer package in the shop for the indefinite future and wondering what to do about the batteries?

Its too late to remove them because I stupidly assumed this would (at the most) be a 4 week job; and that it would in the interim be housed within range of a 15 amp outlet. But I did switch off both isolators and disconnected the I/C +ve lead to remove its draw down. But its still dropping the battery voltage (SoC) at a rate of 4% per day. Solar chargers are currently off because the regulators consume power in the absence of direct sunlight.

On a vehicle I would just disconnect the battery -ve lead and I believe this can be accomplished by disconnecting the -ve cable from the -ve bus attached to the front side of the battery box?

Does anyone have an alternative opinion?

[KRedburn]

I leave mine plugged in year round when in storage. Batteries have been kept fully charged.

[vlamgat]

But that's my point, I cannot access shore power and need to find a way to stop the incipient discharge.

[KRedburn]

using the 15amp plug in you may be able to shut off all 115v devices and leave the inverter/charger on. You will have to tell the inverter/charger to load share a 15amp input. This should be sufficient to maintain the batteries via trickle charge. This assumes your batteries are fully charged before cutting back input power to 15 amp.

you might be able to turn only the vehicle(chassis) disconnect off which will remove the parasitic draws from the chassis electronics.

[vlamgat]

As I wrote, I do not have access to 15 amps or any power for the indefinite wait time for parts to arrive. The vehicle is parked in the shop's outside lot.

So once again the question: how can one reduce the draw on the battery set to zero.
I have already disconnected the I/C which consumes 10 watts even when Disabled and Off.
I have switched off the Solar Controls which consume 5 Watts when the shunt is not linked to bluetooth.
And to repeat for the skimmers, does anyone have any experience of disconnecting the negative bus terminal for the batteries?

[Reverse_snowbird]

We don't have solar, so that's not an issue with us.

When we want to totally shut off the batteries, we have to disconnect the negative cable to the chassis battery and the negative cable to the house battery. The two batteries are always connected on our rig... I think it's a safety concern because we have electric steps.

We have a RAM Promaster chassis and there are electronics that are 'always on' unless the battery is disconnected... parking brake monitor being the major draw. Ram says to disconnect the negative cable if storing over 2 weeks.

Something similar might be happening in your rig. Of course, they're going to have to reconnect the batteries to work on it.

[vlamgat]

Originally Posted by Reverse_snowbird

We don't have solar, so that's not an issue with us.

When we want to totally shut off the batteries, we have to disconnect the negative cable to the chassis battery and the negative cable to the house battery. The two batteries are always connected on our rig... I think it's a safety concern because we have electric steps.

We have a RAM Promaster chassis and there are electronics that are 'always on' unless the battery is disconnected... parking brake monitor being the major draw. Ram says to disconnect the negative cable if storing over 2 weeks.

Something similar might be happening in your rig. Of course, they're going to have to reconnect the batteries to work on it.

I am proposing to follow the same logic except that I have 4 LiPo batteries. So was looking to get an insight as to whether the negative bus disconnect is optimum?

[DW_DX3]

Originally Posted by vlamgat

As I wrote, I do not have access to 15 amps or any power for the indefinite wait time for parts to arrive. The vehicle is parked in the shop's outside lot.

So once again the question: how can one reduce the draw on the battery set to zero.
I have already disconnected the I/C which consumes 10 watts even when Disabled and Off.
I have switched off the Solar Controls which consume 5 Watts when the shunt is not linked to bluetooth.
And to repeat for the skimmers, does anyone have any experience of disconnecting the negative bus terminal for the batteries?

I must be missing something here...why is using a 1/2in wrench on the negative terminal on the house batteries to remove the negative cable not an option? If you don't want draw on batteries, then disconnect the batteries. If the concern is draw on the chassis batteries then the battery shut off next to the driver seat solves that.

Also, note that most solar controllers, including Victron units, do not like solar panels driving current to them during the day for long periods of time without anywhere for the controller to send the current. It's best to disconnect the panels from the controller if the batteries are disconnected from the controller.

[Aussieguy]

Originally Posted by vlamgat

Solar chargers are currently off because the regulators consume power in the absence of direct sunlight.

what solar controller and how many panels have you got?

most controllers will only consume a very small amount (milivolts)
as long as there is no snow coverage
your solar should keep the batteries at least maintained.

Solar is usually connected to the battery before any disconnect and usually you do not disconnect the solar unless you are doing some maintenance on it.


you should be able to flip the disconnect and 99% of your house loads will be turned off.

The rest of the load is used to power things that have memory and don't consume a lot.
-----------------------------------------------------



Regulators??
do you have some other stuff added
OR maybe in the system to connect chassis and house ?
If the power consumption is in the BIM / BIRD / BCC turn that off for storage.

I'm not up to speed with all the motorhome charging circuits but would think that any parasitic loads would be small for the BIM / BCC

solar will easily replace that loss each day if there is sunshine.
-------------------------------------------------------------




ring up the shop and ask them how they intend to maintain the batteries.
you should tell them...... you disconnected the solar

[vlamgat]

Thanks for the answer and suggestions above. Unfortunately they are written from a perspective that gives no reference to the relatively unique installation on this coach. So most of them are just not do-able.

For example the batteries are mounted in a compartment under the entry steps and cannot be disconnected without removing them progressively to access the terminals of the ones mounted behind the removed batteries. But it does have what appears to be a negative bus and so my question really can get answered by a Dynamax person or someone who has a 28SS - will the disconnection of the bus remove all the negative power from the battery set.

There are 2 schools of thought on the Solar Controllers and both are "opinions" without fact: Its not good to leave solar controllers connected to batteries that are not being drained because LI batteries do not like being held at 100% SoC. Or- Its Ok to do this because the Victron Controllers know they are Li batteries and they will monitor the charge rate above a percentage suggested by some to be 95% (as calibrated for that installation) and prevent the top up charge.
But does the Controller use current when there is no solar energy as at night or indoors. I suspect they do but ??
Lastly as written several times, my problem is a storage period without shore power that is indefinite. The vehicle cannot be driven (no RAM parts available and the front is stripped) and there is no access to a power socket within 200 yards of where its parked.

[Aussieguy]

ahhh more details

lithium will not self discharge like lead acid ... most of the problems associated with battery storage is for Lead acid style.

your BMS will turn off (sleep) if the voltage decreases enough
once you get it back connect to a charging source to wake them up.

your Batteries won't self destruct if solar is left on ... otherwise there will be a whole bunch of really mad people out there.

it is suppose to be better for lithium to not store at 100% but the jury is still out
some say it is OK..... others say discharge to 50%.


but with the low rate of self discharge you can leave them unattended for quite some time...
if in doubt ...... consult your battery user manual



Biggest issue with lithium is not to charge them when they get at/below freezing.
so may be best to disconnect them if it is out in the cold.

[Aussieguy]

PS... solar controllers stop charging every day around sunset
so battery gets a rest every night.

[ppine]

Lithium batteries like to be stored at around half charge. Battery disconnect is a great idea.

[vlamgat]

lithium will not self discharge like lead acid ... most of the problems associated with battery storage is for Lead acid style. True, but there are many connections to these batteries that chew a few watts here and a few there and over 8-10 weeks or more that consumption adds up. Many reports on this forum and the FB page of people who have switched off their batteries and parked for the Winter only to find them so depleted in the Spring that they were damaged

your BMS will turn off (sleep) if the voltage decreases enough
once you get it back connect to a charging source to wake them up. True too, but I am trying to avoid getting them down to that point where they may need considerable time to be brought back to useable amperage. Time, which because of the use of the coach I may not have available other than to use it without 12v power.

your Batteries won't self destruct if solar is left on ... otherwise there will be a whole bunch of really mad people out there. This is true too but its not the 100% SoC that sunlight produces that concerns me but rather the lack of sunlight because of where its parked and therefore the wattage drag from the controllers. There are 2 of them and one could be disconnected and I am considering that.

it is suppose to be better for lithium to not store at 100% but the jury is still out
some say it is OK..... others say discharge to 50%. The OM is definitive about the need to store above 50 and below 100%. Only I cannot control when those events would occur. Ideally the BMS would manage that but until they introduce AI to the RV/Boat world, the process is binary.


but with the low rate of self discharge you can leave them unattended for quite some time...
if in doubt ...... consult your battery user manual Consulted the OM, first thing I did and I bleat about that often enough on this forum. Its vague, so I called CS who are trained hamsters and since there is no page on this subject in their playbook the answer I received is essentially what's in the OM and as I wrote above. Don't store at 100% as perpetual charging does not destroy them or cause them to catch fire as happened to the Boeing 787 and Airbus A350 (different chemistries) but it will shorten the life. How much, I asked. No idea said the hamster, as no one has tested this but its a "lot" which is why "we" advise against maintaining full charge. Same story with cell phones Li batteries BTW.



Biggest issue with lithium is not to charge them when they get at/below freezing.
so may be best to disconnect them if it is out in the cold. Even this is 'instruction" is part of a previous Li battery generation requirement. You may have noticed but none of the Happy Campers who have used their coaches for winter sports are commenting on the steps they take to avoid charging their batteries when the ambient is below freezing. This was such a big problem on the B787 that the batteries could not start the APU when the temperature was below 45F during certification in 2007. This problem has largely gone away because the batteries have sensors that limit the charge they absorb at freezing and below and in fact heat themselves above the critical case temperatures as needed. However in the process deplete their charge. Yet another issue of leaving them unattended in Winter for lengthy periods.

Leading me to conclude that there are only 2 viable options: leave the solar controllers connected and keep the SoC as high as possible irrespective of the risk of depletion. Then rely on the BMS to cut off at a high enough voltage to leave sufficient SoC to power the battery heaters;
Or pull the negative from the battery set if I can confirm anyone else's experience of doing that by disconnecting the bus rather than the downstream cable which is unreachable with almost no clearance to get a wrench on the clamps.

[Aussieguy]

if the shop is nearby go and disconnect the battery
take the battery(s) home with you
if the shop can put on temporary power when they finally work on it.


before you disconnect ... if you have an inverter and a big power user such as a heat-gun or a hair dryer or two Use the inverter + some high loads to drain some of your battery.
estimate it.. to get 50% depletion (unless you got a shunt/ meter or bluetooth)
you don't have to be exact...

----------------------------------------------------------------------
seams like you got most of the normal daily running stuff worked out
just go rescue the batteries if you feel they need it.

In general they say 6 months is OK for storage
after that charge them back up to 100% and allow to balance.
then put away again if you are real unlucky and they haven't finished.

[Larry-NC]

Originally Posted by vlamgat

As I wrote, I do not have access to 15 amps or any power for the indefinite wait time for parts to arrive. The vehicle is parked in the shop's outside lot.

So once again the question: how can one reduce the draw on the battery set to zero.
I have already disconnected the I/C which consumes 10 watts even when Disabled and Off.
I have switched off the Solar Controls which consume 5 Watts when the shunt is not linked to bluetooth.
And to repeat for the skimmers, does anyone have any experience of disconnecting the negative bus terminal for the batteries?

Umm...you don't have to disconnect the negative terminal to EACH battery.

You only have to disconnect the ONE CABLE that goes from the battery bank to the rest of the vehicle.

It's okay to leave the batteries connected to each other.

[vlamgat]

Originally Posted by Larry-NC

Umm...you don't have to disconnect the negative terminal to EACH battery.

You only have to disconnect the ONE CABLE that goes from the battery bank to the rest of the vehicle.

It's okay to leave the batteries connected to each other.

So answering my question: ok to disconnect from the bus and leave all the other negative cables connected? I have tried to determine whether the cable leading off the bus is the one that goes to the power distribution board but my multimeter does not have a long enough cable and I need to go buy about 30 feet of 10- or 12-gauge wire to create an extension that will reach to the board.

Isn't this fun and all because I assumed a truck driver used his mirrors.

[DW_DX3]

Originally Posted by vlamgat

multimeter does not have a long enough cable and I need to go buy about 30 feet of 10- or 12-gauge wire to create an extension that will reach to the board.

Your MM extension does not need to be that heavy a gauge of wire even for that length of run. In the case of measuring amperage to check for draw, most meters are rated to 10A passthrough current. But you are checking for much smaller draws already. If measuring for voltage on devices once the cable is disconnected, then the wire diameter matters less. A roll of speaker wire laying around would do in either case.

[vlamgat]

Originally Posted by DW_DX3

Your MM extension does not need to be that heavy a gauge of wire even for that length of run. In the case of measuring amperage to check for draw, most meters are rated to 10A passthrough current. But you are checking for much smaller draws already. If measuring for voltage on devices once the cable is disconnected, then the wire diameter matters less. A roll of speaker wire laying around would do in either case.

That makes sense, especially as the +ve cable from the battery to the in I/C is disconnected and the distribution power switch is OFF. In theory, the draw should be zero but others who have tried this still found a large enough draw down over months to cause the BMS to trigger.

[Aussieguy]

hate to complicate things but what about the chassis battery it needs to be maintained/stored too?
it preferably use a maintenance charger .


.