Voltage Sensitive Relay vs Switch

[mitchell2345]

Hello,

Looking to upgrade my 1 battery system to a dual battery. Looking at various ways to accomplish this. So far i have three options

1. Hook up in parallel
2. use a switch
3. Use a relay/isolator.

I have narrowed down to 2 or 3 as these are def. better options. To me the relay seems like a better deal. Radio/accessories go off batt 2 motor off batt 1. When im driving both get charged and my starting battery is only used for starting.

The only thing I see the switch being better for is if my starting battery were to fail the switch would easily allow me to start off my accessory battery. But charging would be more of a hassle with a switch, right?

I have seem a combo switch+relay but I would rather not spend $150 on just the switches.

Here is the relay i am looking at: http://www.iboats.com/Charge-on-the...0616066--session_id.165286965--view_id.341867

Thoughts?

Thanks,
Mitchell

 

[mitchell2345]

Re: Voltage Sensitive Relay vs Switch

Also, Looking at the wiring diagram do I have to have the Batt Isolator on each batt?

http://www.bepmarine.com/media/product/pro4c27c7b7be03e.pdf

My wiring would look like this:

Really, to install the VSR all i would do is:
1. connect all grounds together (I don't have a buss bar so I would just use a 4 gauge wire to connect two negative terminals together and connect other black wires to one of the spokes)
2. move all Positive accessory wires to House Batt POS
3. Connect VSR to Positive spoke of the House and Starter Batt and connect it to a ground.

Look okay?

 

[Silvertip]

Re: Voltage Sensitive Relay vs Switch

Do you want the multiple point of failure shown in the diagram, or do want something, simple, inexpensive, as reliable as it gets and provides the ultimate in versatility which the switch provides. Once again, it is apparently thought that wiring for accessories absolutely MUST be connected ONLY to the HOUSE battery to have starting battery safety. Here is a dual battery switch diagram. How simple is that. The only rewire that is necessary is to connect the current fuse panel feed to the COM terminal on the switch. The only thing directly wired to any of the batteries would be an automatic bilge pump (best wired to the HOUSE battery). The switch allows you to start the engine from either or both batteries, either or both batteries can be charged when the engine is running, either or both batteries can run all of the accessories. You can't get more versatile than that. You DO NOT need to be constantly fiddling with the switch. Besides, you've not told us what accessories you have that have any chance of leaving you with a dead starting battery. Unless you have a killer stereo system or some other very high current draw items, you could set the switch to BOTH, start the engine and spend the entire day on the water with both batteries powering things, and being charged when you are under way. If you DO have a high current draw accessory and you tend to sit for hours at a time, set it to BAT 2. When ready to leave, see fi the engine starts. If it does (and it very likely will) leave it on BAT 2 and charge that battery while under way. Are ACR's better? Better for what? They cost more, less versatile. Do they work? Certainly? If you are switch challenged then an ACR is probably the ticket for you. But if you can operate a computer you should be able to figure out what the switch is doing for you.

 

[mitchell2345]

Re: Voltage Sensitive Relay vs Switch

I dont have a huge load. Just a regular 4 ch stereo with cd player + sat radio. We regularly float for 4-6 hours and get nervous about being stranded. We like to listen to it loud so we can hear in water. Im not sure how long my 1 batt will last and still start (i have gone 3 hrs so far. I like the idea of the VSR since i dont have to monkey with it but i can see the advantages of the switch. I just have to remember to change to a single battery when floating for extended periods of time.

I also was able to find a VSR for ~$40 so the switch vs VSR is really the same price.

Any other thoughts?

Mitchell

 

[Silvertip]

Re: Voltage Sensitive Relay vs Switch

You are still wrapped around the "switch fiddling" thing. In the scenario you just mentioned, why not set the switch to BAT 2 and go boating. Stop for as long as you like. If the engine doesn't start - THEN switch to BAT 1, or BOTH. It's really not that complicated. The switch is nothing more than a traffic cop for electricity going to and from the batteries. You could even set the switch to BAT 1, go boating and sit for as long as you like. Oh my gosh, now the starting battery is dead! Switch to BAT 2 and go boating. Just the opposite of the first scenario. Then there is scenario #3. Set the switch to BOTH. if you now run down BOTH batteries you have not told us the truth about what you have for accessories or you have one dud battery. Nothing is going to help you if you don't keep good batteries on your boat. I prefer manual control over leaving failure prone electronics to handle things for me.

 

[dwparker99]

Re: Voltage Sensitive Relay vs Switch

I don't have experience with either the manual switch or the automatic ACR/VSR. However, I agree with Silvertip, the versatility of the switch makes it a no-brainer choice for me. I like the idea of being able to choose which or whether both batteries carry the load and which or whether both get the charging current. Under normal conditions either will work. Under abnormal conditions, the switch gives way more options.

 

[glenn property of pam]

Re: Voltage Sensitive Relay vs Switch

i have thought about simular set ups for changing the lights on the boat so they automatically switch between batteries depending if the engine is running or not. your drawing links the batterys and unless you install a choke thats going to cause a major problem as the batterys will ballance and that will exceed the max amps of most relays. a 3 way relay with common being connected to the radio and n/c to the house battery and n/o to the starter battery would work if energized by the ignition switch (outboard) or alt (inboard).
if you want to connect the batteries via a relay/switch for the purpose of charging neither of the ideas is realy ideal. most relays can not handle the current if one battery was flat and the switch can not be changed once the engine is started with out causing a voltage spike that might fry the stereo (they make auto transfer chargers that choke the ampage and only transfer if the starter battery is fully charged) i still prefer the switch as it can also be used as a battery disconnect and emergency starting system which is worth the cost no matter what else you decied to add and like silver likes to point out... simple works best when your out on the water

 

[glenn property of pam]

Re: Voltage Sensitive Relay vs Switch

i looked at the relay after i posted and yep that would work but it does mention fast cycling not anti-cycle like the more expensive units. still think the switch is worth the money. says up to 125amps with 140amp max .....thats will require some heavy wire and im wondering what the speakers will sound like while its rapidly switching.......
im going to go with 50/50 on this as it realy needs fuses in case one battery drops a cell or shorts.

 

[bruceb58]

Re: Voltage Sensitive Relay vs Switch

I suggest getting a switch and the ACR.
http://bluesea.com/category/78/79/productline/overview/329

My switch is pretty much set to just one battery or off. The other battery is the backup which always gets charged with the ACR. You don't have to worry about forgetting what the switch is set to as long as its not on "both".

Its such a no brainer to get the ACR.

 

[EricJRW]

Re: Voltage Sensitive Relay vs Switch

I suggest getting a switch and the ACR.
http://bluesea.com/category/78/79/productline/overview/329

My switch is pretty much set to just one battery or off. The other battery is the backup which always gets charged with the ACR. You don't have to worry about forgetting what the switch is set to as long as its not on "both".

Its such a no brainer to get the ACR.

For something like that, how do you determine if your motor can charge both batteries at the same time? I thought it would switch between batteries for charging... I guess not.

I've been looking at the switch idea for a long time. Presently I have a trickle charger attached to my boat, and a small DPST switch that I flip to charge (top up) one battery or the other. I'd also like to draw from either (or both) batteries via a switch, as presently they are isolated.

Eric

 

[bruceb58]

Re: Voltage Sensitive Relay vs Switch

For something like that, how do you determine if your motor can charge both batteries at the same time? I thought it would switch between batteries for charging... I guess not

It just combines the two, just like throwing a battery switch to both.

 

[EricJRW]

Re: Voltage Sensitive Relay vs Switch

It just combines the two, just like throwing a battery switch to both.

Can the boat's charging circuit handle two batteries in parallel? I realize this will depend on the motor, but I'm curious if this creates a load the motor was not designed for.

PS. Sorry for the thread hijack.

 

[bruceb58]

Re: Voltage Sensitive Relay vs Switch

If its an outboard motor with a 10A charging output, probably not but its not going to load the motor anymore than the output of the alternar or charging circuit can put out.

Here is a scenario that may happen. One battery connected to the engines charging circuit is just slightly discharged and another battery is a lot more discharged. The engine starts and the ACR sees the threshold voltage reached and the ACR connects the battery. If the load of the deeper discharged battery drops the charge voltage below the threshold, the ACR will disconnect. The process of connect/disconnect may be repeated many times until the deeper discharged battery starts getting enough charge into it that that the alternator keeps up with the charge requirement.