Battery Protector, and high voltage load switchover

[Clivearmitage]

Hi. I'm looking for a (low voltage) battery protector for my 220Ah battery bank (on a split charge system).
I'd also like some way of diverting excess 12v power (when the batteries are full, but the solar/alternator are still providing power i.e.14V+?) to a fan/heater.
Unfortunately my solar controller doesn't have a ‘Load' output, but that's the support of functionality I'm trying to find for both the solar panel and the alternator (without replacing the solar controller).
Can anyone suggest anything.
Many thanks
Clive

 

[St3v3]

Have you seen this?

Solar water heating in Streetsleeper's motorhome

I have been working with Rae to design a circuit to heat up his hot water from solar energy. Because of the power system that Rae's motorhome now has installed, it has given us an interesting simple option that won't actually cost very much to implement. We need the following parts and some...

motorhomer.com

The Victron BMV will provide a low voltage alarm, and the relay contact talked about to power up your heater.

 

[Clivearmitage]

Have you seen this?

Solar water heating in Streetsleeper's motorhome

I have been working with Rae to design a circuit to heat up his hot water from solar energy. Because of the power system that Rae's motorhome now has installed, it has given us an interesting simple option that won't actually cost very much to implement. We need the following parts and some...

motorhomer.com

The Victron BMV will provide a low voltage alarm, and the relay contact talked about to power up your heater.

Thanks. Nice implementation, but i don't think that I need all of that system (the timing/delay bit).
Ok. I've had a quick look for a "battery monitor fitted with a programmable relay", but I can't find anything for those search terms.
Would another split charge relay between the leisure side of the current system and the "high voltage load" load work? That would have 2 split charging relays in the system.

 

[Clivearmitage]

Have you seen this?

Solar water heating in Streetsleeper's motorhome

I have been working with Rae to design a circuit to heat up his hot water from solar energy. Because of the power system that Rae's motorhome now has installed, it has given us an interesting simple option that won't actually cost very much to implement. We need the following parts and some...

motorhomer.com

The Victron BMV will provide a low voltage alarm, and the relay contact talked about to power up your heater.

The Victron BMV (and installation holder etc) comes in at a massive £150+. Are there cheaper options?

 

[wildebus]

Hi. I'm looking for a (low voltage) battery protector for my 220Ah battery bank (on a split charge system).
I'd also like some way of diverting excess 12v power (when the batteries are full, but the solar/alternator are still providing power i.e.14V+?) to a fan/heater.
Unfortunately my solar controller doesn't have a ‘Load' output, but that's the support of functionality I'm trying to find for both the solar panel and the alternator (without replacing the solar controller).
Can anyone suggest anything.
Many thanks
Clive

If you are looking for a way to disconnect loads from the battery when it goes down to a certain level, you could have a look at the Victron Battery Protect devices:

Victron Battery Protection

www.onboardenergydirect.co.uk

Red excess power useage, It is a nice idea, but ...
1) A Fan ... That will be using "solar power" anyway if the panels are capable of putting extra power into the battery at that time. The Solar Controller should be automatically increasing its output to supply additional power.
2) A Heater ... now THAT is the kind of load where you get really maximise the solar - but if the solar was able to deliver a lot more, the chances are you wouldn't want a heater on as it will be a nice warm day - at least a Space Heater.

A Water Heater makes the most sense to use the Power.
Streetsleepers system turns on the relay when the voltage hits a certain value and turns on the heater for a set-time.

I have my own system setup so the relay in the monitor switches on when the Battery hits a certain SOC percentage, and then the relay goes off again when the SOC drops to another lower percentage value. When the relay is on, the water heater is powered up.
More info is here - http://www.motorhomebuilder.com/threads/240ac-electric-hot-water-in-campervan.66462/
It works pretty well, but you do need some kind of SOC Battery Monitor with a built-in programmable relay, such as the Victron BMV ones in order for your automated system to both know you have potential excess power AND do something with it.
An alternative is the manual option ... use higher power devices during the day if the batteries are looking good and solar is harvesting well. Slow Cooker, Electric Hob for cooking instead of Gas, etc.


Ref later post:
Ok. I've had a quick look for a "battery monitor fitted with a programmable relay", but I can't find anything for those search terms.
The Victron BMV-701 will provide that

Would another split charge relay between the leisure side of the current system and the "high voltage load" load work?
How would that relay know when the Battery is full and you have excess power?

 

[Clivearmitage]

If you are looking for a way to disconnect loads from the battery when it goes down to a certain level, you could have a look at the Victron Battery Protect devices:

Victron Battery Protection

www.onboardenergydirect.co.uk

Red excess power useage, It is a nice idea, but ...
1) A Fan ... That will be using "solar power" anyway if the panels are capable of putting extra power into the battery at that time. The Solar Controller should be automatically increasing its output to supply additional power.
2) A Heater ... now THAT is the kind of load where you get really maximise the solar - but if the solar was able to deliver a lot more, the chances are you wouldn't want a heater on as it will be a nice warm day - at least a Space Heater.

A Water Heater makes the most sense to use the Power.
Streetsleepers system turns on the relay when the voltage hits a certain value and turns on the heater for a set-time.

I have my own system setup so the relay in the monitor switches on when the Battery hits a certain SOC percentage, and then the relay goes off again when the SOC drops to another lower percentage value. When the relay is on, the water heater is powered up.
More info is here - http://www.motorhomebuilder.com/threads/240ac-electric-hot-water-in-campervan.66462/
It works pretty well, but you do need some kind of SOC Battery Monitor with a built-in programmable relay, such as the Victron BMV ones in order for your automated system to both know you have potential excess power AND do something with it.
An alternative is the manual option ... use higher power devices during the day if the batteries are looking good and solar is harvesting well. Slow Cooker, Electric Hob for cooking instead of Gas, etc.


Ref later post:
Ok. I've had a quick look for a "battery monitor fitted with a programmable relay", but I can't find anything for those search terms.
The Victron BMV-701 will provide that

Would another split charge relay between the leisure side of the current system and the "high voltage load" load work?
How would that relay know when the Battery is full and you have excess power?

Thanks for the Victron battery protector info. It looks good, and reasonably priced.

I don't want any water system in my van, because I do a lot of sub-zero locations, and I don't want frozen/burst pipes, so a water heater makes no sense for me. That's why I asked about the 12v bed warmer (winter) or the 12v fan (summer).

It's all about the extra energy.
Example 1. In the winter I drive my van (with a split charge system) to a ski resort which charges my leisure batteries. If it's a long drive they may be full before I reach my destination. In such a case (but not before) I would like to use the alternator power to run 12v bed warmer.
Example 2. In the summer I go walking, leaving my van in the blazing sunshine, which is great for the solar panel and therefore battery charge, but not great for the (very hot) interior of the van. When the batteries are fully charged, I would like the fan to come on, using the plentiful solar power.

The question about the second split charge relay was because I don't know if it will work. Did your comment mean that it wouldn't work (I've not heard of using 2 split charge relays in one system before), or that it would mean that the 12v bed warmer would be on before the batteries are 100% (on whenever the alternator was on)?

I realise that my requirements seem to be a bit unique (strange).

I'll look at a battery monitor with programmable relay output, but the BMV 700 price seems prohibitive to me (I've already got a basic battery monitor (without output) fitted.
Thanks
Clive

 

[wildebus]

Thanks for the Victron battery protector info. It looks good, and reasonably priced.

I don't want any water system in my van, because I do a lot of sub-zero locations, and I don't want frozen/burst pipes, so a water heater makes no sense for me. That's why I asked about the 12v bed warmer (winter) or the 12v fan (summer).

It's all about the extra energy.
Example 1. In the winter I drive my van (with a split charge system) to a ski resort which charges my leisure batteries. If it's a long drive they may be full before I reach my destination. In such a case (but not before) I would like to use the alternator power to run 12v bed warmer.
Example 2. In the summer I go walking, leaving my van in the blazing sunshine, which is great for the solar panel and therefore battery charge, but not great for the (very hot) interior of the van. When the batteries are fully charged, I would like the fan to come on, using the plentiful solar power.

The question about the second split charge relay was because I don't know if it will work. Did your comment mean that it wouldn't work (I've not heard of using 2 split charge relays in one system before), or that it would mean that the 12v bed warmer would be on before the batteries are 100% (on whenever the alternator was on)?

I realise that my requirements seem to be a bit unique (strange).

I'll look at a battery monitor with programmable relay output, but the BMV 700 price seems prohibitive to me (I've already got a basic battery monitor (without output) fitted.
Thanks
Clive

Example 1: 12V Bed Warmer ... that is a very good use actually for excess power I have an electric blanket as well (240V) version and have to remember that (as an aside, my "excess power diverter" works by using the BMV Relay to then turn on a 240V relay which the Hot Water is plugged into. I could plug in my Electric Blanket into that instead of the Water Heater - a good idea, thanks)
Example 2: Why not just leave the fan on? If you think there will be plenty of solar power spare, that seems the best option.

The thing with both the above is you don't actually know if there is excess power, you are just assuming there is, but without a setup that is controlling a relay based on the SOC (such as a Victron BMV for example), you cannot have something coming on "when the battery is full" as the relay is a dumb device and doesn't know when the battery is full.
You can't go on voltage level as the battery is not fully charged when the battery hits 14.4V (or whatever your battery max is) - it just means the battery has hit Absorption charge mode (so maybe 80% charged?). The key part of the puzzle you are missing is a on/off based on Battery SOC - without that, it is all educated guesswork.

The alternator will be capable of putting out more current than the Battery can ever take in anyway, so if you turned on the Bed Heater when the engine was running then you don't have to worry about the state of charge of the battery at that time.
No reason why you can't have any number of relays that are activated by the engine, and one of those driving the Bed Heater. You need to work out a setup that allows you to chose to power the bed heater when driving, or when parked up (quite doable with bit of wiring).

 

[Clivearmitage]

Example 1: 12V Bed Warmer ... that is a very good use actually for excess power I have an electric blanket as well (240V) version and have to remember that (as an aside, my "excess power diverter" works by using the BMV Relay to then turn on a 240V relay which the Hot Water is plugged into. I could plug in my Electric Blanket into that instead of the Water Heater - a good idea, thanks)
Example 2: Why not just leave the fan on? If you think there will be plenty of solar power spare, that seems the best option.

The thing with both the above is you don't actually know if there is excess power, you are just assuming there is, but without a setup that is controlling a relay based on the SOC (such as a Victron BMV for example), you cannot have something coming on "when the battery is full" as the relay is a dumb device and doesn't know when the battery is full.
You can't go on voltage level as the battery is not fully charged when the battery hits 14.4V (or whatever your battery max is) - it just means the battery has hit Absorption charge mode (so maybe 80% charged?). The key part of the puzzle you are missing is a on/off based on Battery SOC - without that, it is all educated guesswork.

The alternator will be capable of putting out more current than the Battery can ever take in anyway, so if you turned on the Bed Heater when the engine was running then you don't have to worry about the state of charge of the battery at that time.
No reason why you can't have any number of relays that are activated by the engine, and one of those driving the Bed Heater. You need to work out a setup that allows you to chose to power the bed heater when driving, or when parked up (quite doable with bit of wiring).

Exaltée 1. The bed warmer is all wired up already, on a manual switch and optional duration timer. It's just a bit manual.
Example 2. So it seems like the answer is either spend £150+ on a battery monitor that knows when 100% SOC is and can trigger a relay at that point (seems expensive), or leave the fan on full time (seems inelegant).
Thanks

 

[nabsim]

Is this sort of thing any good for what you want?

Dump load relay

 

[St3v3]

Is this sort of thing any good for what you want?

Dump load relay

Wednesday is pub night sometimes, so I haven't looked too deep, but that seems to just be voltage triggered, which will drop as soon as you apply a load, so might not work too well.

 

[wildebus]

Exaltée 1. The bed warmer is all wired up already, on a manual switch and optional duration timer. It's just a bit manual.
Example 2. So it seems like the answer is either spend £150+ on a battery monitor that knows when 100% SOC is and can trigger a relay at that point (seems expensive), or leave the fan on full time (seems inelegant).
Thanks

it would be an expensive (around £120 though) relay if that is the only benefit you would get.
must admit I have a different route for my fan - I set the target temp and the fan speed adjusts automatically depending on how far away the actual temp is.
If you have no temperature controlled feature standard on the fan, you could actually add that externally and have the fan come up when the inside got too hot. That could be a worthwhile addition generally?

Is this sort of thing any good for what you want?

Dump load relay

Looks handy for as they say, "for example, only powering a heater if the battery is well charged." (as opposed to fully charged)

 

[Clivearmitage]

Is this sort of thing any good for what you want?

Dump load relay

I'll have a look of it. Cheers