Voltage Sensitive Relay – Problems?

[changeman]

Have just fitted a Durite 24v 140a VSR across my 2 leisure banks.
This replaces the switch assembly I previously used to direct the charge from my solar panels to my 2 leisure banks.
On the face of it a simple job. 2 terminals (main and auxiliary) connected to the positive terminal on each battery bank and an earth lead connected to battery earth.
I also connected my solar positive from the controller to the main terminal.
The principle seems to be that when one bank reaches 27.4v the relay cuts in and connects the two banks, allowing charge to flow to the lesser charged bank. The relay cuts out at 25.6v.
Simples… except that it does not work that way.
I find that this morning, the fully charged auxiliary bank is taking around 2 amps and the discharged main bank reads zero amps. Then the sun shines through and delivers more than 27.4v to the auxiliary bank, the relay cuts in for a second or two and then delivers 20 amps to the main bank. Hoorah!
However, this drops the voltage on the auxiliary bank and the relay cuts out. Back to square 1.
So, much clicking on and off of the relay as the sun comes and goes and almost a complete lack of charge to the place where I need it most.
Plus, I am nervous at the thought of providing a connection across two battery banks and, when I originally talked to Durite technical about the unit, their man said that the drawback of such a unit was the on/off chatter of the relay during winter charging, which was likely to reduce battery life by about one season.
Questions:
Have I misinterpreted the connections?
Is the unit faulty?
Is it just not appropriate for solar panels?

Regards
Chris

 

[jwilson]

Have just fitted a Durite 24v 140a VSR across my 2 leisure banks.
This replaces the switch assembly I previously used to direct the charge from my solar panels to my 2 leisure banks.
On the face of it a simple job. 2 terminals (main and auxiliary) connected to the positive terminal on each battery bank and an earth lead connected to battery earth.
I also connected my solar positive from the controller to the main terminal.
The principle seems to be that when one bank reaches 27.4v the relay cuts in and connects the two banks, allowing charge to flow to the lesser charged bank. The relay cuts out at 25.6v.
Simples… except that it does not work that way.
I find that this morning, the fully charged auxiliary bank is taking around 2 amps and the discharged main bank reads zero amps. Then the sun shines through and delivers more than 27.4v to the auxiliary bank, the relay cuts in for a second or two and then delivers 20 amps to the main bank. Hoorah!
However, this drops the voltage on the auxiliary bank and the relay cuts out. Back to square 1.
So, much clicking on and off of the relay as the sun comes and goes and almost a complete lack of charge to the place where I need it most.
Plus, I am nervous at the thought of providing a connection across two battery banks and, when I originally talked to Durite technical about the unit, their man said that the drawback of such a unit was the on/off chatter of the relay during winter charging, which was likely to reduce battery life by about one season.
Questions:
Have I misinterpreted the connections?
Is the unit faulty?
Is it just not appropriate for solar panels?

Regards
Chris

I have not used a VSR with solar panels, or a 24v system, but on the installation I had on a 12v system it worked perfectly, but that was with an engine alternator kicking voltage up from 12-ish to 14-15 as soon as the engine started. I think your very low charge from solar panels is just - only just - triggering the relay, and as you say dropping out again as the load of a not-charged battery comes on and lowers the voltage. I suspect a VSR might not be ideal for this job.

 

[maxi77]

I think this is regretably a characteristic of using a vsr. In a camper van I used one to control power to the thermoelectric fridge and I would get similar cycling as the battery voltage dropped when the engine stopped. I don't think there is any problem with the relay, when the relay closes battery 2 sucks in as much power as it can effectively dropping the voltage of battery 1 to a point where the relay opens. The process continues till some charge is obtained in 2 so that the power drawn does not drop the voltage enough to open the relay. If the state of charge of battery 2 is low and the available charging current is also low this may be some time. Perhaps someone with electronic design experience could suggest a circuit to hold the relay closed for some time to allow the voltage in battery 2 to rise naturally to a level sufficient to keep the relay closed naturally or at least to reduce the cycling.

 

[VicS]

Have just fitted a Durite 24v 140a VSR across my 2 leisure banks.ly to reduce battery life by about one season.
Questions:
Have I misinterpreted the connections?
Is the unit faulty?
Is it just not appropriate for solar panels?

Regards
Chris

Why not connect the VSR and the solar panel to give priotity to the bank most needing recharging, the discharged main bank?

 

[pvb]

Why have two leisure banks? Wouldn't one bigger bank be more efficient?

 

[xeitosaphil]

I have 2 x 110Ah batteries wired in Parallel as one bank for Domestics. The 100w Solar panel is wired to this bank and alternator wired to 110Ah Engine Start Battery. There is a Bi Directional VSR between both banks.

Alternator charges engine first then domestic via VSR link. Solar charges domestic bank first then engine Via VSR link.

No chatter experienced at all ever - VSR is a Merlin on a 12v system

 

[pmagowan]

Why have two leisure banks? Wouldn't one bigger bank be more efficient?

Yes, I don't understand this at all.

 

[VicS]

Why have two leisure banks? Wouldn't one bigger bank be more efficient?

How do you measure the efficiency to determine if this is so. How do you define the efficiency for that matter.

 

[HunterWanderer]

A VSR is used between the dedicated engine starter battery and a bank of domestic batteries to prevent the discharging of the starter battery whilst the engine is not running.

The solar charge controller output should just be connected directly to the domestic bank without a VSR.

 

[halcyon]

Have just fitted a Durite 24v 140a VSR across my 2 leisure banks.
This replaces the switch assembly I previously used to direct the charge from my solar panels to my 2 leisure banks.

What size are the two banks ? connect solar power to the higher capacity / most used bank and then top up the lower demand via the VSR, may limit your problem.

The alternative would have been to monitor the charge current to the second bank, then if the voltage dropped but charge to the bank remained, the VSR would stay engaged. If the current direction reversed ( discharge from second bank ) and the voltage was low the VSR would drop out.

Brian

 

[JumbleDuck]

It's a well known issue with VSRs when you have a fairly small supply and the secondary bank wants a lot of current. One answer, as others have said, is to feed the more discharged battery first, if you know which it will be. I use a dual- battery solar controller and a Durite VSR with a switched earth so it is only active when the engine is running.

 

[pvb]

How do you measure the efficiency to determine if this is so. How do you define the efficiency for that matter.

The larger the battery bank, the lower the depth of discharge for a given usage. Minimising depth of discharge prolongs battery life. Larger banks also accept charge more readily.

 

[VicS]

The larger the battery bank, the lower the depth of discharge for a given usage. Minimising depth of discharge prolongs battery life. Larger banks also accept charge more readily.

But you suggested that one large bank would be "more efficient" than two smaller banks.

The questions were how do you define, and measure, the efficiency of a battery bank.

 

[Caladh]

I have 2 x 110Ah batteries wired in Parallel as one bank for Domestics. The 100w Solar panel is wired to this bank and alternator wired to 110Ah Engine Start Battery. There is a Bi Directional VSR between both banks.

Alternator charges engine first then domestic via VSR link. Solar charges domestic bank first then engine Via VSR link.

No chatter experienced at all ever - VSR is a Merlin on a 12v system

I have exactly the same set-up as this and it works without issue. When I originally came to wire up the solar's I spoke to Merlin who advised NOT connecting the solar's to the VSR but go direct to the house batteries.

 

[xeitosaphil]

I have exactly the same set-up as this and it works without issue. When I originally came to wire up the solar's I spoke to Merlin who advised NOT connecting the solar's to the VSR but go direct to the house batteries.

+1

Solar Panel charge to Morning Star Pro Star regulator, then direct to the House Battery with fuse at battery. works really well. Both battery banks charged individually or together, but also both isolated at 12.8v

 

[pvb]

But you suggested that one large bank would be "more efficient" than two smaller banks.

The questions were how do you define, and measure, the efficiency of a battery bank.

One large bank is more efficient, as it will accept charge more readily. To measure the increase in efficiency, it would be necessary to run some tests in controlled conditions, with a decent Ah measuring device.

 

[JumbleDuck]

One large bank is more efficient, as it will accept charge more readily.

Why? Someone else is claiming on a parallel thread that two smaller batteries will charge faster than one large battery of the same capacity, which would appear to be precisely the opposite claim ...

Efficiency? Amp-hours per kilogramme, maybe, or amp-hours per pound (sterling) or perhaps even amp-hours per pound per annum for the TCO enthusiasts.

 

[pvb]

In this thread, the OP said he has two leisure banks. I took this to mean that he has two banks of batteries, all of which are dedicated to domestic use. I can't see the logic in this. What's the point? If all the batteries are combined in one large bank, it's simpler, cheaper (no VSR), and ultimately more efficient. It is an undeniable fact that larger battery banks can absorb charge more readily than smaller banks. It's also undeniable that, for a given usage, a larger bank will suffer a lesser depth of discharge - and it's the depth of discharge which ultimately wrecks batteries.

 

[VicS]

One large bank is more efficient, as it will accept charge more readily. To measure the increase in efficiency, it would be necessary to run some tests in controlled conditions, with a decent Ah measuring device.

Why? Someone else is claiming on a parallel thread that two smaller batteries will charge faster than one large battery of the same capacity, which would appear to be precisely the opposite claim ...

Efficiency? Amp-hours per kilogramme, maybe, or amp-hours per pound (sterling) or perhaps even amp-hours per pound per annum for the TCO enthusiasts.

In this thread, the OP said he has two leisure banks. I took this to mean that he has two banks of batteries, all of which are dedicated to domestic use. I can't see the logic in this. What's the point? If all the batteries are combined in one large bank, it's simpler, cheaper (no VSR), and ultimately more efficient. It is an undeniable fact that larger battery banks can absorb charge more readily than smaller banks. It's also undeniable that, for a given usage, a larger bank will suffer a lesser depth of discharge - and it's the depth of discharge which ultimately wrecks batteries.

There may be practical advanatges of having one large battery bank rather than two smaller ones `but a battery is storage device and efficiency can only mean one thing. Namely the fraction, or percentage, of the energy input that is recoverable as output

I have no idea what the percentage efficiency of a lead acid battery is but suppose it is 90%. That would mean for every 10 joules of energy input 9 would be recoverable as output.

If this applies to one battery then it will apply to a second identical one connected in parallel with the result that for every 20 joules input to the pair 18 would be recoverable as outpu,t 9 from each. 18 is still 90% of 20! No increase in efficiency

 

[halcyon]

In this thread, the OP said he has two leisure banks. I took this to mean that he has two banks of batteries, all of which are dedicated to domestic use. I can't see the logic in this. What's the point? If all the batteries are combined in one large bank, it's simpler, cheaper (no VSR), and ultimately more efficient. It is an undeniable fact that larger battery banks can absorb charge more readily than smaller banks. It's also undeniable that, for a given usage, a larger bank will suffer a lesser depth of discharge - and it's the depth of discharge which ultimately wrecks batteries.

One bank may be engine start to maintain a clean supply for electronics, common on mobo to use a large bank to start one engine and supply domestic, starter noise on electrics a problem, so two banks. One bank may be wheelhouse or VHF bank, so two banks, one may be bow bank for winch or bowthruster, so many reasons for two battery banks.

What we do not know is bank size, loading or use, we could draw 20 amp from 100 amp hour bank 1, 40 amp from 200 amp bank 2, or 60 amp from the 300 amp hour combined bank and reach the same levels. If you have no reason for two banks, then 1 large bank is the answer, but until the three questions are answered no firm conclusion is possible.

If you combine batteries into very large bank you start looking at charge issues ( alternator size ) and battery replacement, the need to change whole bank for one faulty battery.

All have there pros and cons, you can use both options, say if a large inverter is fitted. It is possible to have one large bank that supplies all domestic power and inverter, but in extreme case of excessive inverter loading the bank can be split to maintain supply to critical equipment and limited or no supply to inverter from remaining section. Similar can be done for bridge or VHF supply where in normal use and charging you have one big bank, but in critical cases you have two banks and charge as VSR.

Lots of ways to have feet in both camps.

Brian