Battery separator for lithiums

[BobW9]

1) The dead separator under the hood is a Surepower 1315 which is bi-directional. With my situation, I am thinking all I need is a unidirectional replacement. I seriously doubt I'll ever be needing/wanting to start my engine from the house battery (although you never know ) What would you recommend? And if I do install a battery separator, should I add a DC-DC charger to avoid any potential problems with the lithium battery?

I don't know, but even if the Battleborn lithium batteries are okay with the alternator, I don't think it would charge them very quickly. I first got my B2B because on my first long drive in my Concourse after buying it, it took something over 12 hours to fully charge my two lead acid house batteries (which weren't that low). When I switched to a B2B, from that same level of depletion it charged them up in maybe 2-3 hours. Besides giving the batteries the charging cycle and voltage levels they need, the B2B also basically tricks the alternator into giving it more current for the house batteries. So even though my house lead acid had the same basic charging voltages as the engine battery, they were now being given more current and kept in the stage they needed to be in for best charging, even if the engine battery had the alternator giving it just 13.6V or 13.8V because it was full. It does this, for example, by acting to the alternator as if 13.6V is a voltage level that it can suck up at 25 amps, then converting that into maybe 14.6V to give the house lead acid maybe 18 amps (it raises the voltage, which lowers the current available to pass through a bit, and also has lost overhead in raising the voltage, e.g the B2B gets hot).

2) Behind the drivers seat is a Surepower 135001 LVD. I found the thread about bypassing or removing the LVD. I'm not sure what the LVD is doing for me at this point. Do you think I should be removing the unit or just leave well enough alone? (no harm, no foul)

Short answer: If the overhead switches are disconnected, then I'd guess the LVD is only ensuring that no more than 50 amps are coming through from the batteries to the distribution panel.

Details: Assuming the Victron Multiplus inverter you mention is the 2000 or something, it must be close to the batteries on a much larger wire than goes through the LVD? So that and the MPPT 100/50 must have their own wires direct to the house battery (with large fuses, hopefully!). Then the LVD is still probably being used for the distribution panel. That is assuming the wiring inside the coach was not messed with too much, and the main battery supply is still going through that wire to the panel - is there still a relatively thick red wire (I think it was a #8, though it might have been a #4, I can't remember) going though the LVD?

[Claude]

Appreciate your thoughts.

Item 1: I'm not familiar with the terminology, but I assume that a B2B is the same as a DC-DC charger. Correct? If so, does the B2B act like a separator and eliminate the need to purchase one, or do I need both? If the B2B can take care of it, can it be mounted under the hood where the separator is located, or does it need to be somewhere else? On other forums I've seen discussions about a battery isolation manager. Are these the same things?

Item 2: The wires going to the inverter are both relatively close to the battery (3 or 4 feet) and humongous (appear to be 2 gauge). Without doing some serious gymnastics, I can't make out where the wires attached to the LVD are coming from. Also, the 2 pole terminal (fuse?) next to the LVD have nothing attached to them...removed, no doubt by a previous owner. Since everything seems to work, I'll just let sleeping dogs lie.

Many thanks.

[BobW9]

Sorry - B2B stands for Battery to Battery charger, and yes, is another name for a DC-DC charger (unless there is some distinction I am unaware of). I have the Sterling BB1260 60 Amp model, which has a lithium setting.
https://www.sterling-power-usa.com/batt ... rgers.aspx

You do not need a separator when using the charger, at least not for my BB1260 (it has a delay to start charging, just like the separator does, to avoid adding strain on the alternator during engine start). Note that it is one-way, so with this in the circuit you can not jump start your engine using the house batteries. But for every lithium deep cycle battery I am aware of, you are not supposed to jump start an engine, anyway (it pulls too high an in-rush current and can damage the lithium batteries, their BMS, or at least lower their life, depending). This comes from the manufacturer of at least a few of the 12V 100AH batteries they now sell on Amazon (sometimes it is mentioned, others you need to contact them to find out).

The B2B chargers that I have seen are too large to fit under the engine, and often are not rated for that environment (I mean the ones that are large amps over 30A, not small trickle chargers). When I had my batteries in the lower battery compartment on my Concourse, I had the B2B in there. But I didn't have an inverter in there, like I think you do. Currently I have my batteries, B2B, and Solar chargers all inside the coach.

I'm not certain, but I think the battery isolation manager is just a bit fancier version of the regular 1314/1315 isolators almost all of us have/had.

I think the small 2 pole terminal fuse that is next to the LVD is a small auto-resetting fuse that was required in the circuit when all those other little wires go to the overhead switches. It is not part of the main power going through the LVD to detect low voltage and shut off the circuit. There is, however, another auto-resetting fuse like that under the frame, just in front of the battery compartment, inside a small white plastic housing. That is a 50 Amp fuse that is the main fuse for the battery, going to the distribution panel. It often gets corroded and bad after 15 or 20 years or more, and then causes intermittent issues.

[chin_k]

For unknown reasons, the toggle switches overhead above the drivers seat were all disabled/disconnected.

My guess it that the previous owner can' t get the Victron to work with the toggle switch like the LVD, so he/she removed it. The fact that the separator also did not work is even more of a motivation there.

If the Victron has the low voltage disconnect capability (I am sure all lithium has a battery management module built-in), you do not need the original LVD. Either leave it in place, or remove it. I am sure some people can make use of it, if you want to sell it on eBay, etc.

FWIW, I removed the separator and the LVD when I redo my DC system. I kept all the parts and documented the changes in case the next owner want to undo my work, but I seriously doubt that anyone will want to go back. Solar back in the days when it was built was so expensive that it make sense to let the alternator to charge the coach batteries, but with your solar addition, I think you better off saving the money.

[Claude]

Excellent information. I now have a plan. Many thanks to all who contributed to this thread.