BEP twin engine voltage-sensing relays

D

Doryman

New member
On another boat manufacturer's mailing list, this was posted:

"There are those on this board that thought I was nutts for adding a better distribution center starting from the battery side. But the scenario that you described and the one that happened to me at night (in a shipping channel) made me realize It's kind of an accident waiting to happen. The reason the system isn't ideal is simple. Your console does NOT have fuses, rather, they have circuit breakers. So, when you get a dead short ABSOLUTELY ANYWHERE, it blows that unknown fuse near the battery. NOT the circuit breakers---they work on an increase of heat. NOT, a dead short to ground, like fuses do. If there was no fuse for the entire feed (sounds like an easy fix) then all that wire would get pretty hot before the CB would trip....THATs a fire hazzard. "

He replaced the factory 1-2-both-off switches with equipment like
THIS. You can see the installation HERE.

Does this approach have merit?

Warren
 
This is the system EQ Marine installed on our single engine C-D 22 (the Honda provided system made by BEP). The VSR and switches make a very versatile and fool proof system, but I don't know that they help when bolted fault occurs on any part of the system. The VSR is really to control battery charging and isolation of the two (or 3 or more) batteries. To protect against a hard fault I have a high capacity circuit breaker next to the BEP relay/switch combo. It protects the feed to the circuit breakers and fuses up front. But, a bolted fault could still trip the breaker, then it would be a trouble shooting exercise to find which breaker or fuse was out run by the main breaker. This is a tough situation to avoid without multiple feeds and redundant equipment.
 
I guess it's ok if you only have one battery. But if you have two, as I do, then that system that the factory installed does not do what they intended. The BEP systems, properly installed, should protect your starting battery from being discharged by a drain on your house battery. The system in your photo is for a single engine, two batteries. With two engines, I have noted that the level of charge, measured with a multimeter, is always identical in both batteries. This tells me that they are acting as parallels. The only way to prevent the starting battery from discharge, is to turn it's switch off. The plan was to wire all accessories to the house battery, and with the engines off, only the house battery would drain, even with both switches on. But that does not happen.....both batteries drain equally with both switches on (parallel switch off). One of these days I'll get around to rewiring it, but for now I'm careful to turn off the starting battery switch if I'm going to be using alot of house juice. I'm also very careful to turn off both batteries when the boat is not in use. Look a little further on the BEP website and you'll find the setup for twin engines/twin batteries.
 
On my single engine system the BEP setup does protect the starting battery from house loads. When the voltage falls to the set voltage (around 12.7 volts) on the paralleled batteries, the VSR opens (you can see the red LED go out on the VSR), separating the starting battery from the house battery. I have used the system for 3 days with the "starting" and "house" switches "on" without starting the engine and without any drain on the starting battery. The Wallas heated and cooked and the lights, radio and chartplotter were used at anchor for those 3 days on the house battery alone. When I turned the key, the engine started immediately and the VSR closed to parallel and charge the house battery, just like it is supposed to do. The paralleling switch is for emergency starting if the starting battery fails for some other reason.
 
OK, so it sounds like this BEP system provides an automatic way to protect the starting battery from being drawn down too low by house draw? That way you don't have to remember to turn off the starting battery when you're at anchor because it's all automatic, correct?

I'm not very conversant in electrical terminology. What is a "bolted fault"?

Thanks,
Warren
 
Any fuse or circuit breaker takes time to blow or trip. The higher the current, the less time it usually takes to happen. A bolted fault is simply the fault current that would occur if the positive and negative wires were "bolted" together at the fault location. this is the maximum fault current that could occur on any particular circuit. At that level, it is a race (in time) as to which protective device will open first. If the downstream device closest to the problem wins, then all of the remaining circuits continue to operate. This is what is supposed to happen. On the other hand, if the main fuse or breaker "wins" then the entire fuse or breaker panel will be out of service. This is NOT what you want to happen, but it can and does. The BEP devices have no effect on circuit protection. That is the job of the fuses and breakers. The BEP VSR is only there to separate the starting battery from any house loads so that the engine can always be started. Closing the parallel or both switch defeats this safety device. I never turn the start or house switches off once on the water, but never close the paralleling switch unless the starting battery were to fail for other reasons. Hope this helps to explain what some of the protective devices are doing for you.
 
Warren,
I believe that if you look at the installation photo in your second link, there appears to be a large fuse (under plastic dome, just below the fuse pannel).

As Dennis notes, the VSR/ACR just isolate the engine start and house banks, and give no protection--so the two items are not really related.

As Dennis, I have large capacity breakers on each wire (except the wires to the builge pumps, engine start and Wallas) off each battery terminal block.

You want to avoid a direct short and the potential danger of fire--as well as keep the batteries up.

We just got back from a 3 day trip. We ran battery charger about 2 hours during this time--and that was co-incidental with running the water heater/microwave etc. We were running a freezer, as well as house lights, sterio, and anchor lights. Just before starting the engine, I check battery voltages (we have ARC's and transfer switchs self installed)--the engine start batteries were 12.7 volts. The "house battery" was 12.5 folts and the freezer bank was 12.6 volts (AGM's, so they read a bit higher than lead acid). I check battery voltage every 12 hours--to check and be sure that nothing is depleating batteries. (We have a single Blue Seas LED meter which measures 4 battery banks, one by one).
 
Notavot,

Did I hear you correctly saying not to close the parallel switch (that is turn it to the "OFF" postion) as this defeats the VSR safety feature. Could this be the reason that my two batteries always show exactly the same charge? I'm running two engines and two batteries, each engine wired to a seperate battery, with the house lights, electronics, etc. wired to the port engine battery, which is deep cycle type.

I was under the impression that you only opened the parallel switch to connect them both to one engine for an emergency start.
 
Sealife,

The only switches that should be "ON" in normal service are the "Start" and the "House" switches. The batteries will read identical voltage when the system is being charged, and the red light is showing on the VSR. The "parallel" or "emergency" switch should always be "OFF" unless you need to parallel the batteries to use both to start in an emergency. If the paralleling switch is "ON" at any other time, both batteries will be tied together, and will indeed read the same voltage and will discharge together, without saving the starting battery!

Dennis
 
So, then I'm not going nuts! I always have the parallel switch in the OFF position, reserving the ON position for an emergency start. However, any time I check the two batteries (without the engines on, and without any load), they both read identical. One time, I inadvertly left the battery switches on for over a week, and because the factory did not install an ON/OFF switch for the Autopilot, the LED panel remained on and the batteries were run down, both equally. If the BEP switches were rigged correctly, that should not have happened, the switch protecting the starting battery from depletion. I still think the factory is using the wrong setup for twin engines, twin batteries. The setup they are using, according to the BEP website, is for a single engine and two batteries. I have not had it rewired due to the complexity of all the wires and the expense, and just turn the starting battery switch off if running alot of house lights without the engines on. Another page on the BEP website shows the correct setup for twin engines, twin batteries.
 
I posted this once before, but I think it's worth repeating. The BEP emergency parallel switch connects the two batteries. I defy anyone to tell me why you would want to connect a good battery to a dead battery in an emergency situation.
The emergency parallel switch in Blue Sea ACR setup connects the loads.
That is really what you want, to isolate the dead battery, and connect all the loads to the good battery to get going.
I have the BEP unit, but have reconnected the jumpers on the back of it to do it the Blue Sea way. It just makes more sense.
 
The Emergency parallel switch works differently on the Single engine BEP Marine switch than it does on the Dual engine switch. One the single engine switch is parallels the House battery (or bank) and the Starting battery. On the dual engine switch it parallels the two Starting batteries only, the House battery is never available on the dual engine switch.

No loads (with the exception of the auto bilge pump lead and maybe the stereo always hot lead) should ever come off the batteries...any battery. The engine lead goes to the Engine switch (Port and Starboard in the case of twins) and ALL the house loads come off the House switch. Even with the ubiquitous 1-all-2-off switch no loads should be drawn directly from the batteries; the house loads should come off the Common stud.

The reason you parallel one good battery with the low one is because it's the same thing as using jumper cables on a car. It's easy and it works; if you can't connect one good battery to a low battery and have your engine start you need to get the engine fixed (we're NOT talking about large cold diesel engines here but rather easy to start small outboards), pretty much everything up through 90-hp can be hand-started so this should be a non-issue for 99.9% of cases. The Blue Seas ACR's we've used connect between the positive terminals of the House battery and Start battery; that's the same thing the BEP VSR does (or the two start batteries for the twin engine model). There are always lots of ways to do things; one should chose the solutions they're most at ease with if all the implications of each choice are understood.
 
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