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Old 03-12-2008, 12:30   #1
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Voltage Sensitive Relay

As part of an electrical upgrade, I am installing a new alternator, battery combiner etc. and switches. The Duo Charger has been recommended which I understand is like the Echo Charger which I am generally familiar with. In place of these I have also had recommended a BEP Marine VSR (which can be supplied as part of a new battery switch panel. The manufacturer says:

The Voltage Sensitive Relay (VSR) allows two batteries to be
charged at the same time. When the engine is started and the
start battery reaches 13.7 volts, the VSR engages, allowing two
battery banks (start and house) to be charged simultaneously.
When the voltage drops below 12.8 volts (eg the engine is
stopped), the VSR disengages, separating the batteries.
This system eliminates the possibility of draining the start
battery and protects sensitive electronic equipment powered
from the house battery from harmful engine start up spikes.

Has anyone had experience with the BEP VSR. My understanding is that either batteries can act as a host at any given time depending on their state of charge which is not true of the echo charger. Is anyone aware of any drawbacks with this product? Many thanks.
Nyssa
Sydney Australia
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Old 03-12-2008, 12:51   #2
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VSR can not be used with external smart regulators, (read BEP website) as regulator needs to read battery voltage before it starts working and with a VSR this will be the start battery
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Old 03-12-2008, 14:16   #3
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It sounds like the West Marine (aka Yandina) "Battery Combiner". No big shakes, it just combines two batteries with a relay once alternator has brought the first battery has reached nominal voltage, and then separates the two when charging stops.

The problem is, if your regulator is trying to control charge voltage--which battery does it get to sense? So you wind up making compromises. If you are starting from scratch, there are alternators with dual outputs, each separately sensed and regulated, from folks like Balmar. That's a rational way to control two separate batteries. (As opposed to two large battery banks--they're not sized for that.)
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Old 03-12-2008, 16:44   #4
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I have used combiners before with success although not the one from BEP (I have had some great equipment from BEP - they are now part of Marinco).

You do need to have the combiner sense the same battery bank that is being charged.

One problem can occur if the 2nd battery bank is quite big or your alternator is quite small such that when the relay closes the 2nd bank draws down the voltage so much that the relay immediately opens again. This can cause the relay to cycle and you don't get anywhere. I didn't have this problem.

A second disadvantage is that the charge regulator will keep charging at a high bulk or absorbtion rate until the 2nd bank is charged. This could be an excess charge for the first bank that was partly charging before the relay closed. This shouldn't be a problem if the batteries are not heavily discharged.

The combiners definitely want the same type of battery for both banks since the batteries are being hooked together. The duo charge and the echo charger have their own voltage regulators and can do different types of batteries.

The biggest advantage is that the combiners handle much more charge current than the echo or duo chargers. They are also inexpensive.

I'm always a little confused between combiners, echo-charge, and isolators. It seems like we have more ways to solve a problem than we should need - and each solution is imperfect.

The same could perhaps be said of anchor designs.

If someone understands this better please correct me.

Carl
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Old 03-12-2008, 17:02   #5
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Quote:
Originally Posted by CarlF View Post
The combiners definitely want the same type of battery for both banks since the batteries are being hooked together. The duo charge and the echo charger have their own voltage regulators and can do different types of batteries.

The biggest advantage is that the combiners handle much more charge current than the echo or duo chargers. They are also inexpensive.
Carl
Just going through this stuff myself. The duo charger has its own setup where it will charge a different TYPE of battery than is feeding it and will pass through up to 30amps. The echo has to be charging the Same type of battery as is feeding it the power and I think it max charge is 15amps (may be 20).
Duo charger is the way I'm going.

Extemp.
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Old 03-12-2008, 17:41   #6
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I have a yandina combiner 150. For two years, I used it to combine house and starting banks while charging. Worked fine. According to yandina's website, charging current flows to the discharged battery, not the charged battery, so there is no issue with batteries in different charge states. They have a pretty good faq section:
Combiner Information

Brett
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Old 03-12-2008, 18:57   #7
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too much science

I must say I feel rather lost in this thread.
The solutions I know are :
  1. a diode block that isolates the two / three batteries and has the alternator output as the input to the block, the output being the individual batteries.
  2. A (cheap) 70 A automotive relay getting its excitation from the alternator and making a contact that parallels the 'other' battery to the motor battery.
This is the inexpensive solution offered by my trusted electrician, George, when the diode block failed in my 'other' yacht. George is above making a profit from my misfortune by selling me a fresh diode block. He likes beating the system as much as I do.

This way the batteries were isolated at rest and paralleled when the alternator had output.

Now I think of it a diode was put in the relay coil line to make sure it only worked when the alternator was working. This is what we want, isn't it?

Hope someone can benefit (save lots of $$$) from this.

I would surely apply this solution to my Erato if her diode block ever fails.
Not very likely after 17 years of testing but stranger things happen at sea.
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Old 04-12-2008, 03:24   #8
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Quote:
Originally Posted by Nauticatarcher View Post
VSR can not be used with external smart regulators, (read BEP website) as regulator needs to read battery voltage before it starts working and with a VSR this will be the start battery
Could you provide a link, as I didn't read it that way?

Excerpted from the VSR Instruction sheet:

“... Note: When using a VSR in conjunction with a high performance voltage regulator (eg Next Step Regulator) the regulator sense wire must go to the same point as the sense for the VSR ie the start battery...”

At:
http://www.bepmarine.com/store/web/C...-125A_Inst.pdf

And:
Voltage Sensitive Relays - BEP Marine
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Old 04-12-2008, 04:47   #9
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Quote:
Originally Posted by skipperaris View Post
I must say I feel rather lost in this thread.
  1. a diode block that isolates the two / three batteries and has the alternator output as the input to the block, the output being the individual batteries.
Drawback of this is that the diode block will give you a 0.6 Volt voltage drop.

Skiljerelä

A link to a swedish site, but I think you'll be able to make out the basics from looking at the draeings. This is the system I use, just a simple relay to separate the batteries. Manufactured by Bosch, costs $100.

At work, I modified a weather station to run on solar power. It has two panels that charges a group of batteries, there's a voltage controlled relay that switches to a non rechargeable battery group if the main group drops too low. This is to protect the main group and allow it to be properly recharged. I used this https://www1.elfa.se/elfa~ex_en/b2b/catalogstart.do?tab=catalog relay. Price $60. It would also separate two battery groups but allow simultanious charging if set up correctly.

/Hampus
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Old 04-12-2008, 08:57   #10
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Question Voltage drop

Quote:
Originally Posted by Hampus View Post
Drawback of this is that the diode block will give you a 0.6 Volt voltage drop.

/Hampus
Yes Hampus you are absolutely right.
All I can say is this is how the boat was from the beginning. I did not add the isolator.

In fact I was running my motor just now to charge my batteries and out of curiosity I used my multimeter and discovered that indeed the voltage drop was 0.6 V for two batteries (starting and emergency) and a little over 1 V for the Service battery in use. I wonder if the diodes are on the way out or was it perhaps that the Service battery was drawing more current as it was very low to start with.

I will have to measure this again when the battery is in a better condition but maybe someone can shed some light?
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Old 04-12-2008, 09:13   #11
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Aris-
A blocking (isolation) diode can be of several types, each will have slightly different voltage curves. And, remember that your meter may not be all that accurate at low voltages.
Typically an isolation diode has a voltage drop of around 0.6-0.7V during full rated power--for whatever rating was used--but that drop may lessen as the power being drawn lessens, i.e. as the battery charges up.

You can of course add a similar or matching diode in the "voltage sense" line of the regulator, so the regulator sees the same diode drop that the charging output sees, and compensates for it. Personally I'd rather use a "battery combiner" relay than an isolation diode.
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Old 04-12-2008, 10:19   #12
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Thanks hellosailor

I agree with all you say but if you saw its arrogant large digit display you would not doubt my meter.

Also my blocking diodes are in an encapsulated physical block so I might be excused to think they are all the same or at least were all the same to start with.
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Old 04-12-2008, 14:21   #13
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Quote:
Originally Posted by GordMay View Post
Could you provide a link, as I didn't read it that way?

Excerpted from the VSR Instruction sheet:

“... Note: When using a VSR in conjunction with a high performance voltage regulator (eg Next Step Regulator) the regulator sense wire must go to the same point as the sense for the VSR ie the start battery...”

At:
http://www.bepmarine.com/store/web/C...-125A_Inst.pdf

And:
Voltage Sensitive Relays - BEP Marine
I stand corrected, when I looked at installing one about 4 yrs ago they said it should not be used with smart reg, now they are saying OK as long as they share same sensing point which if it is start batterry will mean Reg will be driven off start batterry voltage not house bank, which will probably give wrong output for optimum charging of House bank, i see they now have dual sensing VSR which is a new product and is probably way to go
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