Charging your Leisure Batteries on the move.

[Flostravels]

Nice article. I read it all with interest. Here’s an idea. As I see it, the VSR is a simple and effective solution except for not dropping to maintenance charge voltage. How about switching in a high power diode (about .6V drop) in series with the supply when you get near the top voltage? At this point, the charger will be in CV mode and the current will be quite low. That would avoid overcharging. Haven’t fully thought this through but I think you would need to sense the voltage on the charger side.

 

[Flostravels]

Looking at the results again, it looks like the VSR is possibly a solid state relay (MOSFET) and hence the loss.
Looks like a case for a simple old fashioned relay with a sensor to control it - which could also give you the maintenance charge control as well (and a few other tricks if you wanted...)

 

[Okta]

Thank you @wildebus for all the testing and information. I note your comments about the B2B cutting back to maintenance voltages after 4 or 5 hours. In practice I don’t think this would be a problem because we all need to stop for fuel and comfort breaks more often than this. The B2B will reset as soon as the D+ feed stops and re-evaluate the state of charge when it reconnects. I have sized my B2B to recharge my daily useage in about 1 hour (you can do this with LiFePO4 but perhaps not lead acid). Another consideration is smart alternators which many vehicles now have to achieve Euro 6 emissions levels. A smart alternator will drop back to a maintenance voltage as soon as the engine battery is full, which is likely to be far sooner than the time needed for the leisure battery charging, a B2B overcomes this limitation.

 

[wildebus]

Thanks for the comments, Flostravels.
The loses on the VSR test were quite high considering it is - as far as I can tell, a basic electro-mechanical relay. I think this is more the cabling (on the VSR test I was using 16mm cable for a fair bit of the run. The test with the native multiplus uses 70mm cable for charger to battery as a comparison). But this was meant to be a pretty typical install, so VSR cabling was 16mm, B2B cabling was 10mm.

I will be making some adjustments to my setup in the next month or so in this area which will deal with the voltage level questions, and will have the following:
35mm cable from Starter Battery to VSR (upgrade from the 16mm)
A Cyrix 230A Combiner to replace the 140A VSR (The Victron Cyrix is a fancier more efficient VSR essentially but with more intelligence)
A Sterling Digital Alternator Regulator. This fits onto the standard alternator and essentially converts it to a 4-stage B2B but running at the full capacity of the Alternator (I bought this back in 2017 but not got round to installing it yet!)
I am toying with the idea of changing the alternator as well? The standard one is 90A, but there are 120A options also. Maybe just leave it and if it fails sometime then swap it for a bigger one?

(decided to instead of using the 25mm cable I have in stock to buy some 35mm cable today to use instead. Two reasons: reduced voltage lose (so less power loss) on the heavier cable; covers me in the event I end up upgrading to a much bigger alternator (which would be good within the limits of what charge the battery can safely take))

 

[wildebus]

Thank you @wildebus for all the testing and information. I note your comments about the B2B cutting back to maintenance voltages after 4 or 5 hours. In practice I don’t think this would be a problem because we all need to stop for fuel and comfort breaks more often than this. The B2B will reset as soon as the D+ feed stops and re-evaluate the state of charge when it reconnects. I have sized my B2B to recharge my daily useage in about 1 hour (you can do this with LiFePO4 but perhaps not lead acid). Another consideration is smart alternators which many vehicles now have to achieve Euro 6 emissions levels. A smart alternator will drop back to a maintenance voltage as soon as the engine battery is full, which is likely to be far sooner than the time needed for the leisure battery charging, a B2B overcomes this limitation.

Ref smart alternators, you are quite correct and I have had quite lengthy discussions with the owner of Ablemail about this topic and how it really complicates the whole split-charging scene. A smart alternator would preclude the use of a VSR entirely.

Ref the D+ feed comment. Not many B2Bs use the D+ signal any longer. They tend to use Voltage Sensing methods to turn on and off (same as a VSR), sometimes with the use of a control line to enable the B2B (like in the case of the Redarc, which has a control wire that is put to +12V to enable the controller, but the controller also needs a highr voltage to actually start)

The recharge speed on LiFePO4 is certainly a very big advantage it has to be said. Probably a bigger advantage then being able to draw more power out. Which B2B do you have (not that many support Lithium yet).

 

[Asterix]

Hi Wildebus,just a question on the Redarc,as it has dual inputs would the graph be similar when charging from solar? I'd be interested to understand the reasoning for the low float charge,do let us know if they give a reply.

 

[nabsim]

The Votronic B2B’s use D+ but you can connect so it doesn’t. I wanted D+ to ensure it didn’t Kickin when the engine wasn’t running as I also charge my starter battery from my solar controller. Ibeleive discussions when I was looking at how to do it said D+ was the way to go but may be remembering wrongly. Not really anything to do with your main content.

 

[St3v3]

All really interesting David

What do you have your bmv set to for charged voltage etc.?

 

[wildebus]

The Votronic B2B’s use D+ but you can connect so it doesn’t. I wanted D+ to ensure it didn’t Kickin when the engine wasn’t running as I also charge my starter battery from my solar controller. Ibeleive discussions when I was looking at how to do it said D+ was the way to go but may be remembering wrongly. Not really anything to do with your main content.

D+ is the traditional way and ensures things are only switched on when the engine is running. Using an ignition-on signal to enable the charger can also be a valid way to avoid it coming on when charging the starter battery, but not always quite as ideal.
Sometimes voltage sensing system can be too clever for their own good! I bought a DRL (Daylight Running Light) kit for my VW T5 and it was very nice BUT it used voltage sensing for the "running" bit - so the lights would come on when the vehicle was stopped but starter battery was getting a charge from the Solar Panels! Had to add an extra ignition controlled relay to stop that.

 

[Okta]

Ref smart alternators, you are quite correct and I have had quite lengthy discussions with the owner of Ablemail about this topic and how it really complicates the whole split-charging scene. A smart alternator would preclude the use of a VSR entirely.

Ref the D+ feed comment. Not many B2Bs use the D+ signal any longer. They tend to use Voltage Sensing methods to turn on and off (same as a VSR), sometimes with the use of a control line to enable the B2B (like in the case of the Redarc, which has a control wire that is put to +12V to enable the controller, but the controller also needs a highr voltage to actually start)

The recharge speed on LiFePO4 is certainly a very big advantage it has to be said. Probably a bigger advantage then being able to draw more power out. Which B2B do you have (not that many support Lithium yet).

I have a Votronic VC1212-45 which includes 4x LiFePO4 profiles. The instructions recommend using the D+ signal for Euro 6 engines and smart alternators, rather than voltage sensing, presumably the voltage sensor would shut down the unit whenever the smart alternator reduced the voltage so not a good idea. The unit also has adjustable input and output power so that it can work alongside existing kit such as Electroblock and existing 50 Amp wiring. I agree with you that speedy recharging LiFePO4 is probably a bigger advantage than the draw current.

 

[wildebus]

Hi Wildebus,just a question on the Redarc,as it has dual inputs would the graph be similar when charging from solar? I'd be interested to understand the reasoning for the low float charge,do let us know if they give a reply.

I've never used the Solar side in fact so don't know the answer to that. I would assume so though.
My query with Redarc has been passed to their technical dept so waiting on them to get back to me.

All really interesting David
What do you have your bmv set to for charged voltage etc.?

Using the default setting of 14.4V. This does mean that something like direct Alternator charging will never make the BMV flag the bank as 100% as the voltage is too low (for that sort of reason I regard 99% as "full" for usage purposes. So my Water Heater is set to turn on when the BMV hits 99% rather than 100% for example)

 

[saxonborg]

My EBL99 controller states the following: Battery functions
6-cell lead acid or lead gel batteries, 55 Ah and above
Simultaneous charging of the starter battery and the living area battery via the alternator, parallel connection of the batteries via a cut-off relay - so would I be correct in assuming that adding a VSR unit would make no difference to the charging of the leisure batteries whilst running?

 

[wildebus]

My EBL99 controller states the following: Battery functions
6-cell lead acid or lead gel batteries, 55 Ah and above
Simultaneous charging of the starter battery and the living area battery via the alternator, parallel connection of the batteries via a cut-off relay - so would I be correct in assuming that adding a VSR unit would make no difference to the charging of the leisure batteries whilst running?

So sounds like your "split-charger" is simply a Relay to strap the starter and leisure batteries together.
This is exactly the same in function as a VSR. The only difference is that a VSR is turned on when a voltage hits a certain value whereas a standard relay is turned on by a control signal such as an ignition wire being activated or the D+ from the alternator going high.
Don't think adding a VSR would make any difference.

 

[saxonborg]

So sounds like your "split-charger" is simply a Relay to strap the starter and leisure batteries together.
This is exactly the same in function as a VSR. The only difference is that a VSR is turned on when a voltage hits a certain value whereas a standard relay is turned on by a control signal such as an ignition wire being activated or the D+ from the alternator going high.
Don't think adding a VSR would make any difference.

I should have added that my solar only charges the leisure batteries so would it be useful in this situation i.e when leisure batteries are full it will then connect to the starter battery?

 

[nabsim]

I should have added that my solar only charges the leisure batteries so would it be useful in this situation i.e when leisure batteries are full it will then connect to the starter battery?

Eric if your solar controller is a dual battery unit just cable the second output to the cable going out of the EBL to the starter battery, that’s how mine works.

Also regarding your earlier thread have a look at cable sizes, if like mine to EBL it will be undersize for maximum available current, doesn’t look like it was designed to pass all available current. When engine is running what volts do you see on control panel? I never saw above 13’s until I added my B2B

 

[saxonborg]

Eric if your solar controller is a dual battery unit just cable the second output to the cable going out of the EBL to the starter battery, that’s how mine works.

Also regarding your earlier thread have a look at cable sizes, if like mine to EBL it will be undersize for maximum available current, doesn’t look like it was designed to pass all available current. When engine is running what volts do you see on control panel? I never saw above 13’s until I added my B2B

I have a Victron controller Neil, it has only one set of battery terminals. Charging volts is certainly better than 13v need to check precise figure though.

 

[Okta]

Some B2Bs also have auxiliary charging for the engine battery e.g. Votronic 1212-45. It can be set to trickle charge the engine battery when an external charging source such as mains or solar is detected, giving priority to the leisure battery. In effect it can work in reverse, instead of charging leisure from engine it charges engine from leisure.

 

[saxonborg]

I should have added that my solar only charges the leisure batteries so would it be useful in this situation i.e when leisure batteries are full it will then connect to the starter battery?

Any comment on the this Wildebus, as I was thinking of ordering a Cyrix from On board Energy?

 

[wildebus]

Any comment on the this Wildebus, as I was thinking of ordering a Cyrix from On board Energy?

If you were to bypass the existing Relay and fit a Cyrix Combiner VSR then you would be charging both batteries from the Alternator AND both batteries from the Solar, so I would say it would be a definate plus.

Another popular option to do this kind of thing is the "Battery Master" but personally, I like the VSR route better.

One comment just to add in - combining the batteries using a relay is really only suitable when the batteries are similar in their charging profiles. If your solar controller is a smart controller and goes to say 14.4V on absorption and 13.8V on float (pretty typical), that needs to be ok for both Leisure AND starter battery (chances are it will be, but just adding this comment as a precaution)

 

[saxonborg]

If you were to bypass the existing Relay and fit a Cyrix Combiner VSR then you would be charging both batteries from the Alternator AND both batteries from the Solar, so I would say it would be a definate plus.

Another popular option to do this kind of thing is the "Battery Master" but personally, I like the VSR route better.

One comment just to add in - combining the batteries using a relay is really only suitable when the batteries are similar in their charging profiles. If your solar controller is a smart controller and goes to say 14.4V on absorption and 13.8V on float (pretty typical), that needs to be ok for both Leisure AND starter battery (chances are it will be, but just adding this comment as a precaution)

Thank you for the advice, could I just add the Cyrix to the existing wiring or would I need to make some changes in the Electrobloc?