How-To install DC-DC charger to replace VW Split Charge relay

[Art Vandelay]

Hi @Loz
Great instructions, thanks.
I'm planning on replacing both my leisure batteries at the same time and wondering if I can follow the basic principle of the 9 steps you have detailed.
I want to replace both leisure batteries at the same time but don't know what sequence I should be removing.
T5 2012 Cali SE

Steve

 

[Loz]

Hi @Loz
Great instructions, thanks.
I'm planning on replacing both my leisure batteries at the same time and wondering if I can follow the basic principle of the 9 steps you have detailed.
I want to replace both leisure batteries at the same time but don't know what sequence I should be removing.
T5 2012 Cali SE

Steve

yes the battery disconnection steps will count for your job as well.

 

[MattBW]

I was thinking if you ever fancied doing a little video sometime Loz, let me know. Something like changing leisure batteries I think would be useful for so many folks and I wager would be easier if someone else was filming it.

 

[a892374923874]

Looking to put solar on our Beach due to arrive next month. I would like:

1. MPPT tracker (ideally max voltage to work with 2x120W panels in series)
2. Charge leisure battery to 100% from solar and engine and keep it maintained.
3. Keep engine battery maintained (trickle)
4. Don't discharge the leisure battery to 80% as soon as the engine is started.
5. Nice to have:- Load shed once leisure battery becomes discharged to prevent damage.
6. Meter or App to show current, Amp hours, and voltage.

And ideally in one small box that fits in the space where the split charge relay is under the seat. Also conscious that this will be a brand new Beach, so a bit wary of messing with it too much and affecting the warranty!

I've seen 5 devices in this space at reasonable price (<£300 or so), but none do everything I want. Ablemail looks like it is nearly there, but doesn't maintain the starter battery.

I suspect 2 boxes will achieve all this, but not sure which combination would be best. Any suggestions much appreciated.

Cheers.

Requirement	Victron SmartSolar	Votronic MPP 250 Duo	CTEK D250SE	Redarc BCDC	Ablemail AMS12-12-30
1. MPPT tracker (ideally max voltage to work with 2x120W panels in series)	Y	Y	N (Max voltage 23V)	Y	Y
2. Charge leisure battery to 100% from solar and engine and keep it maintained.	Y	Y	Y	Y	Y
3. Keep engine battery maintained.	N	Y	Y	N	N
4. Don't discharge the leisure battery to 80% as soon as the engine is started.	N	N	Y	Y	Y
5. Nice to have:- Load shed once leisure battery becomes discharged to prevent damage.	Y	N	N	N	N
6. Display or App to show current, Amp hours, and voltage.	Y	Y	N (I think)	N	Y (maybe)
Nice to have:- Ability to have a different type of leisure battery from the starter battery	N	N	Y	Y	Y

 

[a892374923874]

Anyone any views or have I asked a stupid question?

 

[Joker 1299]

Anyone any views or have I asked a stupid question?

Talk to @Roger Donoghue he knows his stuff

 

[Loz]

Ablemail do a dc -dc with solar in but no monitoring.

I have the Redarc as above and the Victron for solar.

 

[Loz]

Anyone any views or have I asked a stupid question?

Sorry, your username made me think you were a spam advert so I ignored it.

Ablemail do a dc -dc with solar in but no monitoring.

I have the Redarc as above and the Victron with Bluetooth for solar, as that has a great monitoring app.

 

[Roger Donoghue]

Looking to put solar on our Beach due to arrive next month. I would like:

1. MPPT tracker (ideally max voltage to work with 2x120W panels in series)
2. Charge leisure battery to 100% from solar and engine and keep it maintained.
3. Keep engine battery maintained (trickle)
4. Don't discharge the leisure battery to 80% as soon as the engine is started.
5. Nice to have:- Load shed once leisure battery becomes discharged to prevent damage.
6. Meter or App to show current, Amp hours, and voltage.

And ideally in one small box that fits in the space where the split charge relay is under the seat. Also conscious that this will be a brand new Beach, so a bit wary of messing with it too much and affecting the warranty!

I've seen 5 devices in this space at reasonable price (<£300 or so), but none do everything I want. Ablemail looks like it is nearly there, but doesn't maintain the starter battery.

I suspect 2 boxes will achieve all this, but not sure which combination would be best. Any suggestions much appreciated.

Cheers.

Requirement	Victron SmartSolar	Votronic MPP 250 Duo	CTEK D250SE	Redarc BCDC	Ablemail AMS12-12-30
1. MPPT tracker (ideally max voltage to work with 2x120W panels in series)	Y	Y	N (Max voltage 23V)	Y	Y
2. Charge leisure battery to 100% from solar and engine and keep it maintained.	Y	Y	Y	Y	Y
3. Keep engine battery maintained.	N	Y	Y	N	N
4. Don't discharge the leisure battery to 80% as soon as the engine is started.	N	N	Y	Y	Y
5. Nice to have:- Load shed once leisure battery becomes discharged to prevent damage.	Y	N	N	N	N
6. Display or App to show current, Amp hours, and voltage.	Y	Y	N (I think)	N	Y (maybe)
Nice to have:- Ability to have a different type of leisure battery from the starter battery	N	N	Y	Y	Y

I've done a bit of reading on the "regen braking" etc (In brackets as its the alternator loaded up that is the "braking")

The alternator cuts out at around 12.4v when the engine is idling, to reduce load, and therefore emissions. This means that battery floats at around 80%.

However, when you are driving it increases to 18v to make up for the loss (so your SB should end up higher than 12.4v). Even so, it's a bodge in my mind.

As your LB is not being used anywhere near as much as your SB whilst driving (even with a fridge on) it should charge fully - i.e. Not just 80%. As each time the alternator flicks back up to 18v mode the LB will get it's fill.

When you turn the engine off, the split charging relay should disengage - which means your LB will not now drain from 100% down to match the possible 80% SB. With the relay disengaged (not energised) the SB and LB should be totally seperate.

Personally, if you are worried about your SB I'd do one of two things.

1) Fit a chunky Anderson connector to the LB, and make up a heavy gauge jump lead that can plug in behind the passenger seat, and hook up to the starter batt.

or

2) buy a dual battery MPPT like this:

https://www.amazon.co.uk/dp/B00JYBZG96/?tag=vwcalifornia-21

That's a dual MPPT charger - it charges the LB with MPPT, and when needed, lets up to 1 amp of PWM charge go to the SB.

You can then add an LCD display:

https://www.amazon.co.uk/dp/B01N69TRBS/?tag=vwcalifornia-21

The display is a bit pricey. I'm thinking of carrying these in stock. I had a bad batch of WRM chargers where a % packed up on 1st use so I've abandoned them. Didn't get a very helpful response from Western Co, the manufacturer.

I would not concern yourself over taking the SB to 100% and therefore running some imagined risk of overcharging from the "regen braking". The alternator is "smart" and won't pump power into a full battery. If it does, then that makes all starter battery chargers impossible to use on VWs with this bluemotion business.

 

[Loz]

@Roger Donoghue the problem is that when the alternator is switched to idle, then the current flows back from the leisure batteries across the simple split charge relay that VW still insists on fitting and why the DCD-DC charger is better for the T6.

 

[Roger Donoghue]

Ahhh. That's dumb! In which case I'd replace their relay with a voltage sensing relay, or, as you say, bypass it with a DC to DC charger.

 

[a892374923874]

Sorry, your username made me think you were a spam advert so I ignored it.

Ablemail do a dc -dc with solar in but no monitoring.

I have the Redarc as above and the Victron with Bluetooth for solar, as that has a great monitoring app.

Hi. Not a spam, I just try to use unique usernames on each forum so a search doesn't throw up all my hobbies!

Would there be a way of also maintaining the engine battery from solar using victron along with redarc or ablemail?

 

[Loz]

Hi. Not a spam, I just try to use unique usernames on each forum so a search doesn't throw up all my hobbies!

Would there be a way of also maintaining the engine battery from solar using victron along with redarc or ablemail?

you could use a Ctek smartpass..
I recently saw someone had used the "Load" output from the Vitcron to the starter battery

 

[clarinetbcn]

If your solar charger is only connected to the leisure batteries then it will not trickle charge the starter battery.

The whole point of Loz’s post is that since the Bluemotion setup keeps the starter battery at 80%, a charge of more than 80% of the leisure battery will always bleed back to the starter battery. Therefor, a trickle charge from the solar battery will go to both the starter and leisure battery once the leisure battery is charged over 80%. A solar panel converts a design flaw of the T6 into an unexpected advantage.

 

[Roger Donoghue]

The whole point of Loz’s post is that since the Bluemotion setup keeps the starter battery at 80%, a charge of more than 80% of the leisure battery will always bleed back to the starter battery. Therefor, a trickle charge from the solar battery will go to both the starter and leisure battery once the leisure battery is charged over 80%. A solar panel converts a design flaw of the T6 into an unexpected advantage.

When the engine is off, the relay should be open, and solar charging to the LB won't trickle to the SB

 

[a892374923874]

The docs for the Ablemail talk about an optional extra display and an add-on unit to enable trickle charging the engine battery. I'm in an email conversation with them on the details. I'll report back on the outcome next week.

Redarc seem to have a high end battery management unit which covers all the bases but it is >£1000.

 

[Sp0_0k]

Due to a litium mod, I have made some modifications on a Beach and most importantly added a hall sensor (non intrusive compared shunt)for measuring all current flows.
1) What surprised me, the leasure battery can get 60 even 70 amps charge. Do you have that on Ocean?
I suspect the flow is less due to double capacity on the leisure side (2 batteries) against main.
2) I never seen a back flow of charge as mentioned in topic.
3) I didn't find non 100% charging problematic in 4 years. More than that I didn't notice it to be claimed 80% anyway. After hours of driving I still see the current flow to leisure battery.

Though I like the idea of dc-dc to taking it slowly (30amps) and not loading the alternator and cold engine too much, but I suspect most of that burst charge current is flowing from engine battery anyway.

Does it affect battery health?
Again after 4 years, and we live in a van almost 5 months nonstop in a year. (daily almost full leisure battery drain) it is starting to decline, but still holds decently. And that is roughly ~600 cycles, which is considered almost max for lead acid.

What I kinda like in stock system is fast charge. With 60-70 amps you refresh the battery pretty fast even on idle.

My current solution is 3kwh extra lifepo4 removable battery. Charges from alternator on a manual switch via universal dc dc charger at 1-30amps desired.
Lets me decide if I want not to load alternator/engine much in specific conditions.
That charger makes the most important thing of balancing the lithium cells which is the major concern with technology.
It solves the problem with engine battery as well. Can charge it from leisure battery and more importantly identify issues by measuring battery resistance and showing exact ah loaded, etc.
Funniest thing, this is all accomplished by a 100eur hobby dcdc charger that can charge any battery type there exists. It is just not marketed for overpriced automotive industry

 

[rod_vw]

@Sp0_0k I'm interested in the make and model of your dc-dc charger please.

 

[Sp0_0k]

Yes you could do this, however, if the cranking battery is very flat, the current inrush would probably blow the 80amp fuse.

Which is kinda true vice versa but doesn't happen with flat leisure battery.
80 amps fuse doesn't mean it blows on 79 instantly. Might hold 100 for minutes or blow on 60 if too hot

 

[Sp0_0k]

@Sp0_0k I'm interested in the make and model of your dc-dc charger please.

Turnigy Reaktor.

 

[Lightning]

Turnigy Reaktor.

It would be great if you could sketch a circuit schematic. How much did your battery cost?

 

[Sp0_0k]

Depends on desired capacity. I built from winston cells ~200ah 800eur or so.
Don't even have a schematic. Not using bms because charger controls and balances on each charge.
The only hassle was a long sick lead of cables directly from leisure battery (extra fuses), which was initially after getting fed up with cig light sockets.
Charger goes from leisure battery/alternator and permanently connected to lifepo4 mains and balance leads.
Litium has a shunt with wireless display for monitoring capacity and loads. Battery perfectly sits in a storage box 2seat beach, weighs 22kg
It is not automated which I actually decided to leave as it is. Forces to manualy check cells health.
Really hate fully automated BMS solutions, when some cheap circuit fries expensive cell.
Added a 12v heating mat, cos you better not charge lithium below 0'c.

 

[Lightning]

Depends on desired capacity. I built from winston cells ~200ah 800eur or so.
Don't even have a schematic. Not using bms because charger controls and balances on each charge.
The only hassle was a long sick lead of cables directly from leisure battery (extra fuses), which was initially after getting fed up with cig light sockets.
Charger goes from leisure battery/alternator and permanently connected to lifepo4 mains and balance leads.
Litium has a shunt with wireless display for monitoring capacity and loads. Battery perfectly sits in a storage box 2seat beach, weighs 22kg
It is not automated which I actually decided to leave as it is. Forces to manualy check cells health.
Really hate fully automated BMS solutions, when some cheap circuit fries expensive cell.
Added a 12v heating mat, cos you better not charge lithium below 0'c.

Thanks. So you just connect your charger to the original AGM battery? It sounds like a simple solution to increase capacity.

 

[Sp0_0k]

Yep easy as that. When engine running it gets directly from alternator, when stops (start/stop) annoying, it keeps charging from agm.
You can set any min input voltage from 9v in charger when to shut down to protect the source (agm).
All these RC hobby things are hundred times smarter and cheaper than automotive hyped stuff.
Can easily modify as well.

2kw litium with bms and auto charger will easily cost you 3-4k eur

 

[Sp0_0k]

Another simple thought hit me.
This simple isolator solution could be both good and bad.
If it simply hard connects both leisure and engine batteries on a cranck, you might be loading the engine battery even more.
If you were camping and lets say dropped leisure batteries to 11,8 (close to empty) but your engine bettery has kinda enough juice to cranck, you might not start. Because there is a surge of current drawn from engine battery not just to starter but to leisure batteries, and it can easily be 100-200 amps spike extra load on engine battery. 80amp fuse will definitely handle those extra short term.

If you were camping on a hookup and leisure batteries are full. You might be actually helping the engine to start. More attempts can actually help as more cuurent will flow to a lower voltage battery (in this case engine one)
As far as I am aware there is no circuitry (diode) preventing currency going back.

In theory the hard switch that connects leisure and engine without ignition would help with lots of engine failed starts. Just turning it for 5-10 minutes would throw enogh current to engine battery. And just switch it off on a start.
I never jump start cars but throw a dcdc charger asking owner to wait 10-15 mins. Putting just 5-10ah could be enough for start and you actually doing battery a favour making next own start easier.