B2B and Battery Master

[Snelly]

Question regarding how a Renogy DC to DC and battery master work together. The other day, after only 2 days off grid, in full of sun, my vehicle failed to start. The battery master light was red and was warm. The green light on the Renogy b2b was flashing to indicate charging. I'm puzzled how the b2b and batter master work together as it feels as though the b2 b is feeding the lithium hab battery and the hab battery is feeding the vehicle battery via the battery master. The situation is the same today, after checking wiring and disconnecting the EHU although the engine did start today. As I'm moving tomorrow to 3 days without EHU I'm trying not to repeat the problem.

I have an Elddis 175 (2013) and have installed a 100ah ePever LifePo, with an ePever duo racer solar mppt charger, 2 x 100w solar, Renogy DC to DC and a battery master. The battery master is wired directly on to the Renogy b2b.

I have the b2b set to lithium non actuation mode. I do not have a control feed from the ignition as I don't have a smart alternator.

Is there something wrong with the set up? I realise diagnosis is difficult remotely but would value any advice about my setup. TIA.

 

[LithiumConvert]

You need a D+ signal to only activate the B2B when then engine is running.
Regardless of alternator type. Especially so, if you have solar.

The Battery Master is not the problem.

 

[AdrianChen]

Is your EPever Duo connected to the starter battery to charge it up?

If so it may be raising the start battery voltage sufficiently to start the B2B. The B2B will win!

As LithiumConvert says, a D+ signal to start the B2B would stop this happening.

 

[LithiumConvert]

Is your EPever Duo connected to the starter battery to charge it up?

Short term possible solution - disconnect it.

That may help.

 

[growly_bear]

I have a Renogy DCDC with MPPT, so slightly different. Mine also has a non stmart alternator. It is not connected to a D+. When I switch off the engine, the starter battery keeps passing current to the hab battery until the starter battery voltage drops to about 12.7. Connecting to a D+ does not alter this, and this is the reason that I've not fitted a battery master as it'll cause a charging loop.

As a start, I'd disconnect the battery master and watch the starter battery voltage and when it stops charging the hab battery...

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[LithiumConvert]

When I switch off the engine, the starter battery keeps passing current to the hab battery until the starter battery voltage drops to about 12.7. Connecting to a D+ does not alter this

The answer to that is to buy a good B2B on which the D+ signal works properly.

The Schaudt 121545, as fitted by Hymer, works well.
or Sterling Power.

 

[LithiumConvert]

As a start, I'd disconnect the battery master and watch the starter battery voltage and when it stops charging the hab battery...

Another very short term solution, whilst the good B2B is ordered and fitted.

 

[oldiesontour]

Many of the Renogy B2B with MPPT are dual Charge (ie they charge the SB and lb) from solar... something Renogy don't always advertise I asked their (un) help Email the first several replies made no sense but eventually got it passed up the chain. and got a tech Wiz who confirmed that it is dual charge

 

[growly_bear]

Another very short term solution, whilst the good B2B is ordered and fitted.

The OP is away from home...

 

[growly_bear]

The answer to that is to buy a good B2B on which the D+ signal works properly.

The Schaudt 121545, as fitted by Hymer, works well.
or Sterling Power.

The Renogy does however fit where I need it to. My solution is to fit a relay which disconnects the starter battery or wire the alarm/radio to the hab battery or fit an ablemail which is configurable. At the moment I'm monitoring my situation.

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[oldiesontour]

My original 30a and now my 50a Renogy with mppt both work exactly as they should,The 30a had LA batteries the 50a is on lipo..my only complaint would be if the solar is connected the engine charge is limited to 50%,not a major problem as I just switch the panels off if I need max engine charge

 

[growly_bear]

My original 30a and now my 50a Renogy with mppt both work exactly as they should,The 30a had LA batteries the 50a is on lipo..my only complaint would be if the solar is connected the engine charge is limited to 50%,not a major problem as I just switch the panels off if I need max engine charge

The later versions of the 50A have software which makes it adjustable, so there is now no need for a switch which is good

 

[oldiesontour]

The later versions of the 50A have software which makes it adjustable, so there is now no need for a switch which is good

Good move on Renogys part mine is around 18mths old so either It'll stick with the switch or may add an ignition powered relay

 

[Snelly]

Is your EPever Duo connected to the starter battery to charge it up?

If so it may be raising the start battery voltage sufficiently to start the B2B. The B2B will win!

As LithiumConvert says, a D+ signal to start the B2B would stop this happening.

That's a thought. I will try connecting the D+ and see if it helps as the Mppt is indeed charging the vehicle battery as well. But I guess we are assuming that linking the D+ will not only activate the b2b when ignition is on, but also deactivate it when it's off? I had assumed the b2b will only turn on when the alternator is running as it is meant to have a sensor for this. The Renogy manual says no need to connect D+ for this reason.

 

[Snelly]

I have a Renogy DCDC with MPPT, so slightly different. Mine also has a non stmart alternator. It is not connected to a D+. When I switch off the engine, the starter battery keeps passing current to the hab battery until the starter battery voltage drops to about 12.7. Connecting to a D+ does not alter this, and this is the reason that I've not fitted a battery master as it'll cause a charging loop.

As a start, I'd disconnect the battery master and watch the starter battery voltage and when it stops charging the hab battery...

But the battery master is what is meant to trickle charge the vehicle battery, which is where the problem was.

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[AdrianChen]

That's a thought. I will try connecting the D+ and see if it helps as the Mppt is indeed charging the vehicle battery as well. But I guess we are assuming that linking the D+ will not only activate the b2b when ignition is on, but also deactivate it when it's off? I had assumed the b2b will only turn on when the alternator is running as it is meant to have a sensor for this. The Renogy manual says no need to connect D+ for this reason.

Perhaps the sensor is start battery voltage based?

 

[Snelly]

Many of the Renogy B2B with MPPT are dual Charge (ie they charge the SB and lb) from solar... something Renogy don't always advertise I asked their (un) help Email the first several replies made no sense but eventually got it passed up the chain. and got a tech Wiz who confirmed that it is dual charge

The Renogy b2b is just that - I have a separate epever moot controller which is, itself, dual output - one for vehicle battery and the other adjustable for lifepo.

 

[Snelly]

Perhaps the sensor is start battery voltage based?

I think it's meant to sense the rise in voltage when the alternator is working. As you said, maybe the solar controller is giving it a false input and turning it on.

 

[oldiesontour]

The Renogy b2b is just that - I have a separate epever moot controller which is, itself, dual output - one for vehicle battery and the other adjustable for lifepo.

So does the Renogy see battery voltage rise due to epever and therefore start pulling power from SB to lb ?

 

[Snelly]

So does the Renogy see battery voltage rise due to epever and therefore start pulling power from SB to lb ?

That's the current theory so going to try a D+ connection which, I hope, will ensure the Renogy doesn't pull power when engine is not running.

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[CAB96]

Disconnect the Epever MPPT from the Starter.

The battery master will take care of the Starter, you don't need both trying to do it.

 

[Driventemple]

There is a big difference between ignition control and proper D+. The B2B should not be working if the engine is not running.

 

[Snelly]

There is a big difference between ignition control and proper D+. The B2B should not be working if the engine is not running.

Unfortunately it is still working. Just played around with the D+ which I have taken from the B pillar converter's box. Started the engine and switched off. The Renogy b2b continues to charge the leisure battery (flashing green light). The D+ voltage shows 1.4v when engine off. Thought it would show 0v.

 

[Snelly]

Disconnect the Epever MPPT from the Starter.

The battery master will take care of the Starter, you don't need both trying to do it.

I put the battery master in to cover keeping the vehicle battery charged when I'm in store as this is a barn so no solar. Perhaps I should just connect it only when in store but don't want the vehicle battery to drain again.

 

[Driventemple]

The D+ voltage shows 1.4v when engine off. Thought it would show 0v.

Where are you getting D+ from? The True D+ signal is actually Negative so you need to incorporate a relay to convert that to a positive signal.

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[growly_bear]

Unfortunately it is still working. Just played around with the D+ which I have taken from the B pillar converter's box. Started the engine and switched off. The Renogy b2b continues to charge the leisure battery (flashing green light). The D+ voltage shows 1.4v when engine off. Thought it would show 0v.

fred_jb i remember you playing with s renogy and using D+. Yours kept on charging too after engine switch off didn't it?

 

[fred_jb]

fred_jb i remember you playing with s renogy and using D+. Yours kept on charging too after engine switch off didn't it?

Yes, but when I first installed this it only ran for a short time until the starter battery settled down to less than the trigger voltage, which I think is 12.7V, as it was sometimes a little higher than that immediately after a run.

The situation is now different in that I have installed a small dedicated solar panel and MPPT controller for the starter battery which is keeping that at a bit higher voltage. I think the only reason that is not triggering the B2B is that the recent sunny weather is keeping the leisure battery at 100% so the B2B is not operating to charge it, though in that situation it will switch to sending power to the starter battery rather than taking power from it.

Things will be different on our forthcoming trip when we will be using much more power such that the leisure battery is not always at 100%. Before we leave I will reinstate the relay to disconnect the starter battery from the B2B when a D+ signal is not present, but will bypass this with a diode to allow B2B to starter charging to still happen if the leisure battery is full.

Incidentally, the engine running signal from the B pillar converter's wiring needs to be used to operate a relay which switches an ignition sourced 12V, also available in the B pillar wiring, in order to get the correct D+ signal, in the form expected by most other devices.

 

[growly_bear]

Yes, but when I first installed this it only ran for a short time until the starter battery settled down to less than the trigger voltage, which I think is 12.7V, as it was sometimes a little higher than that immediately after a run.

The situation is now different in that I have installed a small dedicated solar panel and MPPT controller for the starter battery which is keeping that at a bit higher voltage. I think the only reason that is not triggering the B2B is that the recent sunny weather is keeping the leisure battery at 100% so the B2B is not operating to charge it, though in that situation it will switch to sending power to the starter battery rather than taking power from it.

Things will be different on our forthcoming trip when we will be using much more power such that the leisure battery is not always at 100%. Before we leave I will reinstate the relay to disconnect the starter battery from the B2B when a D+ signal is not present, but will bypass this with a diode to allow B2B to starter charging to still happen if the leisure battery is full.

Incidentally, the engine running signal from the B pillar converter's wiring needs to be used to operate a relay which switches an ignition sourced 12V, also available in the B pillar wiring, in order to get the correct D+ signal, in the form expected by most other devices.

Thanks for that Fred. Hopefully it will help the OP.

 

[Snelly]

Yes, but when I first installed this it only ran for a short time until the starter battery settled down to less than the trigger voltage, which I think is 12.7V, as it was sometimes a little higher than that immediately after a run.

The situation is now different in that I have installed a small dedicated solar panel and MPPT controller for the starter battery which is keeping that at a bit higher voltage. I think the only reason that is not triggering the B2B is that the recent sunny weather is keeping the leisure battery at 100% so the B2B is not operating to charge it, though in that situation it will switch to sending power to the starter battery rather than taking power from it.

Things will be different on our forthcoming trip when we will be using much more power such that the leisure battery is not always at 100%. Before we leave I will reinstate the relay to disconnect the starter battery from the B2B when a D+ signal is not present, but will bypass this with a diode to allow B2B to starter charging to still happen if the leisure battery is full.

Incidentally, the engine running signal from the B pillar converter's wiring needs to be used to operate a relay which switches an ignition sourced 12V, also available in the B pillar wiring, in order to get the correct D+ signal, in the form expected by most other devices.

Thanks Fred. Sorry for delay in replying as I'm travelling at present. Did you have a battery master installed as well? I have now disconnected mine until I get home and have time to investigate further, as I suspected there was a loop being created. You say the b2b "though in that situation it will switch to sending power to the starter battery rather than taking power from it." I thought the b2b only works one way? I am still struggling to fully understand what is happening.

 

[fred_jb]

Thanks Fred. Sorry for delay in replying as I'm travelling at present. Did you have a battery master installed as well? I have now disconnected mine until I get home and have time to investigate further, as I suspected there was a loop being created. You say the b2b "though in that situation it will switch to sending power to the starter battery rather than taking power from it." I thought the b2b only works one way? I am still struggling to fully understand what is happening.

I have an Ablemail which is a battery master type device, though can be configured to only transfer power if your preset volyage conditions of the two batteries are met.
.
They don't all do this, but the Renogy 50A combined B2B and MPPT controller that I fitted will send spare solar generated power to the starter battery if the leisure battery is full. It uses the same connection for this that it uses to take power from the starter battery/alternator in B2B mode when the engine is running.

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