Battery Setup

[Kestrahl 6]

I have just sorted out our battery box's and have a battery monitor to install, I'm also thinking a change from the "1 both 2" switch to a BEP Cluster with VSR. We have 2 x 6V trojan house batteries 220AH and 1 x sealed start battery. Am I correct in assuming the VSR will charge the start and then when that is full charge the house? Or will it just charge both sensing from the start? I can't seem to find it explained all that well. Also attached a wiring diagram of what it will look like in simple terms, any opinions if this is setup is ok or not would be appreciated

[idlerboat 116]

Hi ya..

 

I am a little confused so rather than make it more complicated, this what i ended up with. (Took a lot of deep thunks to get there)

 

Two battery banks.

Alternater goes to engine battery.

Solar pannels through smart regulator goes to engine battery.

 

Wind generator goes to house battery.

 

Isolater, combiner is between the two banks. Charges engine battery first.....then lets through to house. Iso/combiner is a very low loss switching system, unlike the diode type.

 

1/2 or both is still there but only as a bypass for isolator/combiner.

(ie...if you need to start from house or use radio from engine).

 

The isolator combiner is across 1/2 on the 1/2 both switch.

 

All else dosnt matter. (amp meters, volt meters etc)

 

Becarefull with multiple power sources...one can stop the other from working, becuase one regulator will "see" the voltage and shut down its imput. That is why I have split the system.

 

Or you can go for a super duper (and expensive) total controller that manages everything...all imputs and outputs.

 

(try a google search for "hell roaring electronics'" (I kid you knot !) for some very good basic circuits.

cheers

[wheels 543]

This is why I like charge splitters. I am not a fan of VSR's. However, in your case a VSR could be a good way to go. VSR's are quite practicle in this situation where you are replacing a manual chang over switch.

For other situations,

There are several ways to do multi bank charging.

One way is two alternators. One large one for House charging and one smaller for start. Mechanically more complex, but once that is sorted, you have an excellent system.

Two is a charge splitter. The reason why a charge splitter in my opinion, is that either bank takes what it needs to get back to a full charge and then when both banks are equyal in charge they both raise voltage wise together. Not charge wise. In other words, you usually have two very different bank sizes and most often two very different battery types in those banks. So both banks have quite different needs. A VSR is OK, but one bank always takes a priority over the other. Which bank is more important for the priority charge???? Of course it depends on the situation. Small boat setups, that is not an issue. Large set ups with other systems like Genset, Inverter, Battery charger, Solar panels, Wind etc and so on, it may well be. All my charging, from all sources, go through a charge splitter so as all banks are continuosly topped up.

[Guest]

Could you pls clarify - by "charge splitter" do you mean Diode based splitter, or some other type?

 

If you mean Diode splitter, I also like them (no moving parts) and have one.

 

To overcome the diode voltage drop, I use a regulator sense wire connected to the house batt.

 

However, this does pose the question: if the house batt is full, the alternator will not attempt to quickly charge a severely depleted engine batt. Anyone have a view as to whether this is a valid concern in practice?

 

Thx

Karsten

[Marshy 30]

Cant see that being a huge problem really because if you get stuck out surely you can wire the house into parallel and start off that too?

[wheels 543]

Could you pls clarify - by "charge splitter" do you mean Diode based splitter, or some other type?

Thats the thing. There are two types. The old type that are simply diodes and the newer type that are a little more complex inside and do not have any voltage drop. The older diode type can easily be fixed for Voltage drop and I really don;t know why they don't do this as part of the unit. Simply put a Diode in the sense line. The exact same voltage drop is then catered for.

[Farrari 4]

 

To overcome the diode voltage drop, I use a regulator sense wire connected to the house batt.

 

However, this does pose the question: if the house batt is full, the alternator will not attempt to quickly charge a severely depleted engine batt. Anyone have a view as to whether this is a valid concern in practice?

 

 

A severely depleted start battery along with a fully charged house battery would only happen in rare circumstances I would have thought. I would be more worried about having a charged start and depleted house battery (more common) with the sense wire connected as you have it. The alternator is going to ramp up to full charge voltage and potentially overcharge your start battery.

 

I use dual diodes well along with a multi-step smart charger but the sense wire is connected to the start battery. This leads to the opposite problem where the smart charger will ramp down before the house battery is fully charged leading to longer charging times. I also have a 1/2/Both manual change over switch as an emergency backup for starting.

[Farrari 4]

I have just sorted out our battery box's and have a battery monitor to install, I'm also thinking a change from the "1 both 2" switch to a BEP Cluster with VSR. We have 2 x 6V trojan house batteries 220AH and 1 x sealed start battery. Am I correct in assuming the VSR will charge the start and then when that is full charge the house? Or will it just charge both sensing from the start? I can't seem to find it explained all that well. Also attached a wiring diagram of what it will look like in simple terms, any opinions if this is setup is ok or not would be appreciated

Here is a relatively simple explanation from the BEP site. VSR == Voltage Sensing Relay

When the engine is first started the relay is open and remains open until the start battery has reached a preset 13.7 volts for 12 volt systems and 27.4 volts for 24 volt systems. At the rated voltage the relay closes providing charge to both batteries (start and house). When the voltage drops below 12.8 volts (when the engine is stopped), the VSR disengages, separating the batteries.

 

As I understand it, VSRs are better used where the start and house batteries are matched. This is rare with a smaller cruising vessel because you would normally have a lower capacity crank battery (High Cranking Amps) and one or more high capacity deep cycle batteries for the house.

 

One of the problems you can get with VSRs is an oscillation state (The VSR clicks in and out repeatedly). When the crank battery reaches the sensing threshold (BEP == 13.7V) while charging the two batteries will be connected together. The discharged house battery will then drag the charge voltage down, potentially below the disengage voltage threshold so the VSR will disengage. This will in turn bring the crank battery up to above the sense threshold and the cycle will start over again until finally you get enough charge into the house battery.

 

The other issue I see with dissimilar batteries is that charge rate/voltage when the batteries are connected together is either going to be too high for the smaller crank and too low for the bigger house battery(s) so it's a lose/lose.

 

Your other options are split charging (a single alternator connecting to dual battery banks via MOSFETs or Diodes (less efficient), dual alternators or one of these.

 

Or you can go for a super duper (and expensive) total controller that manages everything...all imputs and outputs.

 

Personally I would prefer the split charging using MOSFETs with a multi-step charger (sense on crank) because there is so little to go wrong.

[wheels 543]

Firstly, you can not safely charge two unequal banks of batteries. So a 1/2/both switch is bad. Not to mention the issues you can have if you leave it connected to both while draining the House bank, or if you have a failing bank.

 

Charge splitters are an isolator to the battery banks. In simpole terms, the banks can not "see" each other. But the Alternator can "see" both banks. A battery that is low in charge, draws more current.So when the Alt is producing power the flatter bank will take the greater charge. Once that bank reaches the level of the other bank, then both banks accpet and equal amount of Alt output current. And if you look at that from a slightly different angle, an already charged battery therefore will not be over charged.

The sense wire normally connects to the House battery as that is the bank that tends to be cycled the lowest. Once both Banks are equal, they both accept an equal share of charge current till fully charged.

Of course, the down side is when you have a failing bank upsetting the balance. But that is the same case for all scenarios apart from a seperate Alt for each bank.

 

Normally the VSR has a wide latching voltage difference. It swithces on at 13.7V and off at

12.8V. So unless you have a very sad bank, it should not oscillate. They are good for small setups where you want to protect your start battery at all costs. But yes, they are a problem with differing bank types or sizes.

 

Another way to go is an Echo charge. These devices were made specificaly to charge a second battery when mounted some distance away from the others, for anchor winch duty. In this situation, the winch battery is mounted in the bow near the winch and a small set of wires run form the echo charge, instead of big expensive battery leads running all the way up to the bow. The Echo charge is a 12V to 12V charger. So it uses the 12V of the bank being charged by the Alt to charge the next bank. Of course, there can be negatives with that as well like it is charging the other bank all the time. So some of your house bank would be going into charging the start bank all the time.

[Marshy 30]

What about the other option of a second alternator? Seperate charging circuits completely with the option of a fail safe spare setup? Most boats carrying that sort of gear have motors big enough to run a second alternator or is that a recipe for disaster?

[wheels 543]

Yep, said that at the top.

[Marshy 30]

Ah jeez wheels ya got me again! good work!

[Kestrahl 6]

Thanks for the reply's, as I can see it a second alternator would be ideal, however I have no space for another alternator.

 

The VSR doesn't sound 100% ideal for my setup, its doing 220AH house and 720cca start if I remember correctly. Although not quite as bad as it would be with a bigger house bank, or a high output alternator external reg.

 

Wheels do you have any brands or links to charge splitter's you could recommend?

 

Good reply Farrari.

[wheels 543]

A second Alt is an expensive addition. Wave goodby to a good chunk of a grand at the least. Substantially more if it is not an easy straight forward install.

Remember that the start bank is CCA (Cold cranking amps), which is what the bank can deliver in terms of current to the Starter motor, Not what the actual storage is. But on the other hand of that, you only use a small few amps starting in most situations and so charging back up is normally only minutes, not hrs like a House bank.

There are several splitters around. Go for the new generation of splitters that have no voltage drop. Plus they often have a special connection on them for the sense wire and an LED that shows the Alt is actually charging. The advantage of no lose, is that on mine, i split the Solar, Wind and mains Battery charging also. So both banks keep topped up.

[Fusion 0]

Blue sea Splitter or SI-Series Automatic Charging Relay

Is great here is a list why I choose this one

 

1 It is dual sensing so will go both ways. Alternator on the start battery bank. or Solar and Wind Gen on the House bank. Once either bank gets over 13.0V it combines but it has very good protection based on heavy current draw and is rated up to 120Amps.

 

Combine (after 30 sec.) @13.6V @ 12V DC

Combine (after 90 sec.) @ 13.0 V @ 12V DC

Open (after 10 sec.) @12.35V @ 12V DC

Open (after 30 sec.) 12.75V @ 12V DC

Open High 16.0V @ 12V DC over voltage protection

 

2 It has an ignition switch wire as well and disconnect when you hit the starter. This is cool as some times I had the Chart plotter and Autopilot reset. Not an issue when you are at anchor but on a long sail I would fire up the engine for a charge and everything would reset.

 

3 Remote LED output indicates relay state. On when combined

[Guest]

Just checking - the mentioned "new generation" charge splitters with no voltage drop; I assume they would be using relays to pass/block current, instead of diodes.

 

Is anyone aware of a zero-voltage drop splitter using solid state components (mosfets or whatever) instead of relays to switch current?