Do VSR’s always charge in both directions?

[fredrussell]

My Durite VSR seems to work by taking power from the higher charge battery, and sending it to lower charge battery, which is obviously what it’s meant to do. It does this in either direction, so to speak. Is there such a thing as a ‘one way’ VSR?

 

[justanothersailboat]

A VSR is a relay so it's like an automatic switch, I wouldn't expect it to be directional.
I would expect a diode system (split charge diode) to be directional, but have to have some voltage loss (and hence limit the max voltage seen on the downstream side to a bit less than the max on the upstream)

 

[Refueler]

I always assumed as VSR requires 3 things ....

1. Power charging source
2. One battery that has sensing cable to it
3. Second battery that relies on VSR sensing #2 is charged and redirecting charge to #3

Never thought one battery charges or feeds another .... In fact I thought VSR would not work without #1 ??

But I could well be wrong. Sure Paul will tell all.

 

[PaulRainbow]

A dual sensing VSR is a relay, it just connects the two batteries in parallel. It does not take power from one battery to the other, as such, it simply allows the charging source to charge both batteries. The benefit over a standard relay is that the VSR only closes when one of the battery voltages reaches a set voltage and opens again when another set voltage is reached.

There is such a thing as a single sensing VSR, that only reacts to the voltages of one of the batteries, but these are rare these days. Not sure what would be the point of one.

 

[PaulRainbow]

I always assumed as VSR requires 3 things ....

1. Power charging source
2. One battery that has sensing cable to it
3. Second battery that relies on VSR sensing #2 is charged and redirecting charge to #3

Never thought one battery charges or feeds another .... In fact I thought VSR would not work without #1 ??

But I could well be wrong. Sure Paul will tell all.

That's a fair description of a single sensing VSR. Most now are dual sensing, so points 2 and 3 relate to either battery.

 

[fredrussell]

Cheers for replies. Here’s why I ask. In my camper van I have a normal lead acid engine battery, and a 100a/h lithium (LiFePo4) leisure battery. VSR sits between these two, connected by 4mm2 wire which is rated at 40amps @ 12v. At each end of this charging wire is a 30 amp fuse. It works fine - though I realise this is the ‘naughty’ way of charging a LiFePo battery, and a B2B charger is the ideal way. There’s a 200watt panel on the roof which charges the LiFePo. The VSR is for winter months charging of the LiFePo. I’ve noticed when engine is switched off, there’s an amp or so going from LiFePo to engine battery. I assumed this is because LiFePo battery is sitting at upwards of 13v, whereas lead acid engine battery is sitting at 12.7v or so. According to Durite’s blurb:

• The VSR makes (or cuts-in) at 13.3V and breaks (or cuts-out) at 12.8V.

 

[fredrussell]

I always assumed as VSR requires 3 things ....

1. Power charging source
2. One battery that has sensing cable to it
3. Second battery that relies on VSR sensing #2 is charged and redirecting charge to #3

Never thought one battery charges or feeds another .... In fact I thought VSR would not work without #1 ??

But I could well be wrong. Sure Paul will tell all.

I’m not 100% on this at all, but it’s my understanding that a VSR will operate without any power charging source. It just connects the two batteries if voltage of one reaches ‘cut in’ point, and voltage of other reaches a voltage low enough to trigger VSR to close. At least, that is what I think is happening with my setup…

 

[LittleSister]

Cheers for replies. Here’s why I ask. In my camper van I have a normal lead acid engine battery, and a 100a/h lithium (LiFePo4) leisure battery. VSR sits between these two, connected by 4mm2 wire which is rated at 40amps @ 12v. At each end of this charging wire is a 30 amp fuse. It works fine - though I realise this is the ‘naughty’ way of charging a LiFePo battery, and a B2B charger is the ideal way. There’s a 200watt panel on the roof which charges the LiFePo. The VSR is for winter months charging of the LiFePo. I’ve noticed when engine is switched off, there’s an amp or so going from LiFePo to engine battery. I assumed this is because LiFePo battery is sitting at upwards of 13v, whereas lead acid engine battery is sitting at 12.7v or so. According to Durite’s blurb:

• The VSR makes (or cuts-in) at 13.3V and breaks (or cuts-out) at 12.8V.

Yes, a dual sensing VSR (that's most of them, as Paul says) will keep the batteries connected until both drop below 12.8v.

Your Lithium battery will be charging your van battery (when the engine is off a solar panel not operating) until they both fall below 12.8v.

In my previous boat, conventional set up with (non-Lithium) domestic and engine start batteries (both AGM), and alternator connected to engine battery, after the engine was stopped, and with no current draw from either, the VSR would remain on (as I could see from indicator light) for some considerable time when the batteries were new. As the batteries got older, the time it stayed on reduced significantly, eventually only a few moments. Unlike in your situation, there would have been negligible flow between the the two batteries through the VSR in this state, as both batteries were at a more or less identical voltage.

I suspect you will need a more sophisticated charging arrangement if you wish to maintain one battery at a higher voltage than the other. A crude work-around would be to add a manual on/off switch in series with the VSR, so you could isolate the van battery. This will leave the solar panel charging the Lithium presumably 'domestic') battery, but not the van battery. If you forget to turn it on when running the van engine you will be charging the van battery only and not the domestic one.

I’m not 100% on this at all, but it’s my understanding that a VSR will operate without any power charging source. It just connects the two batteries if voltage of one reaches ‘cut in’ point, and voltage of other reaches a voltage low enough to trigger VSR to close. At least, that is what I think is happening with my setup…

The VSR does (in a normal set up) operate without any generating power source (e.g. alternator or solar panel). It does require power to operate, usually taken from one other of the batteries, but the VSR's power consumption is tiny, and in general use can be ignored.

 

[PaulRainbow]

Cheers for replies. Here’s why I ask. In my camper van I have a normal lead acid engine battery, and a 100a/h lithium (LiFePo4) leisure battery. VSR sits between these two, connected by 4mm2 wire which is rated at 40amps @ 12v. At each end of this charging wire is a 30 amp fuse. It works fine - though I realise this is the ‘naughty’ way of charging a LiFePo battery, and a B2B charger is the ideal way. There’s a 200watt panel on the roof which charges the LiFePo. The VSR is for winter months charging of the LiFePo. I’ve noticed when engine is switched off, there’s an amp or so going from LiFePo to engine battery. I assumed this is because LiFePo battery is sitting at upwards of 13v, whereas lead acid engine battery is sitting at 12.7v or so. According to Durite’s blurb:

• The VSR makes (or cuts-in) at 13.3V and breaks (or cuts-out) at 12.8V.

The reason that current is flowing from the LifeP04 to the LA is because the VSR is kept closed by the solar charge, that's a trickle charge going to the LA.

You do not want to keep the LifeP04 fully charged over Winter. Run it down to about 80% and turn the solar controller off.

If you feel the need to have the engine battery on charge over winter leave the solar on, but disconnect the LifeP04. Depending on the solar controller, you might want to lower the charging voltages for the Winter.

In normal, Summer use, i can't see why you want the batteries in parallel (VSR closed) all the time the Sun is shining. Let the solar look after the LifeP04, again, you don't want them sitting fully charged for long periods though. You'll likely want the alternator to put some charge into the LifeP04, so you can fit a normally open relay in the negative wire to the VSR and have this relay energised by the alternator charge warning lamp.

If your camper van has a smart alternator you should not use it as above, fit a B2B charger.

 

[PaulRainbow]

Regarding the VSR operating without a charging source, it doesn't need charging as such, it needs one of the batteries to be above the set point for closing the relay. But, without a charging source that set point will not be reached, unless the batteries were very recently charged and still have not fallen to the set point for opening the relay.

 

[VicS]

>
>
If your camper van has a smart alternator you should not use it as above, fit a B2B charger.

​

Durite 0-727-43 200A Smart programmable relay is designed to be used with the latest range of vehicles fitted with smart alternators and regenerative braking systems.
In addition, there are 9 available programmes allowing the user to set the charging/protection voltages to suit their requirements.
.

 

[Refueler]

That's a fair description of a single sensing VSR. Most now are dual sensing, so points 2 and 3 relate to either battery.

You know I have a strange switch arrangement on the latest 38 ... Engine battery main switch and separate domestic battery switch. Solar as far as I can tell feeds the Domestics as well as engine.

With the domestic batterys now knackered ... I noted that with engine running - both batterys charged .... but when engine not running - domestic batterys discharged with nothing coming from engine battery even when just off charge.

Before season launch - two new domestics will go on board ... at present the Victron is maintaining all .... and I will pay safe and not change the system ... it works and thats good enough for me.

Top battery is engine
Two batterys below are the paired domestics.

The split charge relay ... must investigate that further ...

Solar controller which I rep;laced with a chinese controller which gives med 2 USB and a digital display of whats going on !!

 

[fredrussell]

…I suspect you will need a more sophisticated charging arrangement if you wish to maintain one battery at a higher voltage than the other.

Really, that’s the nub of the issue. I’ve been looking at B2B chargers this afternoon and they seem to have come down in price a bit so that’s probably the answer.

 

[PaulRainbow]

Durite 0-727-43 200A Smart programmable relay is designed to be used with the latest range of vehicles fitted with smart alternators and regenerative braking systems.
In addition, there are 9 available programmes allowing the user to set the charging/protection voltages to suit their requirements.
.

But how do you set anything with LA and LifePo4 in parallel ?

 

[PaulRainbow]

You know I have a strange switch arrangement on the latest 38 ... Engine battery main switch and separate domestic battery switch. Solar as far as I can tell feeds the Domestics as well as engine.

With the domestic batterys now knackered ... I noted that with engine running - both batterys charged .... but when engine not running - domestic batterys discharged with nothing coming from engine battery even when just off charge.

Before season launch - two new domestics will go on board ... at present the Victron is maintaining all .... and I will pay safe and not change the system ... it works and thats good enough for me.

Top battery is engine
Two batterys below are the paired domestics.

The split charge relay ... must investigate that further ...

The relay is just that, a relay, not a VSR. Most likely energised by the charge warning/excitation connection on the alternator, hence it only works when the engine is running.

 

[VicS]

The split charge relay ... must investigate that further ...

The relay in your picture is not a VSR . It is just a 12 volt 75A relay

Energised somehow when the engine is running to charge the domestic battery from the engine alternator in parallel with the engine start battery.

.

 

[PaulRainbow]

The relay in your picture is not a VSR . It is just a 12 volt 75A relay

Energised somehow when the engine is running to charge the domestic battery from the engine alternator in parallel with the engine start battery.

.

See post #15

 

[Refueler]

The relay in your picture is not a VSR . It is just a 12 volt 75A relay

Energised somehow when the engine is running to charge the domestic battery from the engine alternator in parallel with the engine start battery.

.

I did not say it was VSR .... I know its a solid state relay. I can read the label without Googling it.

I posted in response to Pauls explanation .... which made me think about setup put in by Toro Yard in Sweden for previous owner.

 

[William_H]

Cheers for replies. Here’s why I ask. In my camper van I have a normal lead acid engine battery, and a 100a/h lithium (LiFePo4) leisure battery. VSR sits between these two, connected by 4mm2 wire which is rated at 40amps @ 12v. At each end of this charging wire is a 30 amp fuse. It works fine - though I realise this is the ‘naughty’ way of charging a LiFePo battery, and a B2B charger is the ideal way. There’s a 200watt panel on the roof which charges the LiFePo. The VSR is for winter months charging of the LiFePo. I’ve noticed when engine is switched off, there’s an amp or so going from LiFePo to engine battery. I assumed this is because LiFePo battery is sitting at upwards of 13v, whereas lead acid engine battery is sitting at 12.7v or so. According to Durite’s blurb:

• The VSR makes (or cuts-in) at 13.3V and breaks (or cuts-out) at 12.8V.

I imagine the VSR has sensing within the box from both battery connections. What you really want is sensing only from the car battery and alternator. This might be difficult to modify the VSR you have. It is the mismatch of lithium and LA with different resting voltage that is causing it to fail to release on engine stop.
If it were possible to adjust to voltages at which the VSR operates and releases this might solve your problem. May not be possible. In which case try to find a VSR with single battery sensing. Might be hard.
Other wise you are stuck with needing to disconnect the system when the car stops. A switch. or maybe a relay operated from the oil pressure sender on engine. Either add in series or replace the VSR with relay.
I assume the lithium battery has a built in charge controller to permit it to be charged from alternator. ol'will

 

[VicS]

I did not say it was VSR .... I know its a solid state relay. I can read the label without Googling it.

I posted in response to Pauls explanation .... which made me think about setup put in by Toro Yard in Sweden for previous owner.

I don't believe it is a solid state relay. Perhaps you should Google the number to find out what it is for sure.

I imagine the VSR has sensing within the box from both battery connections. What you really want is sensing only from the car battery and alternator. This might be difficult to modify the VSR you have. It is the mismatch of lithium and LA with different resting voltage that is causing it to fail to release on engine stop.
If it were possible to adjust to voltages at which the VSR operates and releases this might solve your problem. May not be possible. In which case try to find a VSR with single battery sensing. Might be hard.
Other wise you are stuck with needing to disconnect the system when the car stops. A switch. or maybe a relay operated from the oil pressure sender on engine. Either add in series or replace the VSR with relay.
I assume the lithium battery has a built in charge controller to permit it to be charged from alternator. ol'will

A switch (or relay) in the negative connection will disable the VSR.