PV connections to Batt

[Marauder]

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Hi Folks

I'm now back from latest venture, and new tasks surfaced for attention !

Latest dumb question:

If I connect PV panel to controller, and take output from controller, is it Ok to just split the output from controller and feed directly to the Hab AND Cab batteries both at the same time pls ??

Seems to me that's what should happen, but in my experience with MH there's often stuff that is not immediately apparent or obvious . . . .

All comments gratefully absorbed !
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[The Wino]

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Hi Folks

I'm now back from latest venture, and new tasks surfaced for attention !

Latest dumb question:

If I connect PV panel to controller, and take output from controller, is it Ok to just split the output from controller and feed directly to the Hab AND Cab batteries both at the same time pls ??

Seems to me that's what should happen, but in my experience with MH there's often stuff that is not immediately apparent or obvious . . . .

All comments gratefully absorbed !
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I think if you do that you will in effect connect the batteries in a way that will mean they balance so are both equally charged. If one fails it will take the other one out too and in winter you risk discharging your vehicle battery if the hab one gets low. There's also the possibility unless the connecting wires are very substantial of overloading them.
This assumes you mean just taking a wire to both batteries from one terminal. If you mean a controller with separate outputs to the two batteries that's fine.

 

[Derbyshire wanderer]

Not a good idea as effectively you are joining them together and therefore will discharge both together never mind the issues that could happen as the wire would likely be relatively light compared to the potential current draw between the batteries.

 

[Reallyretired]

You can get a controller that will feed both batteries through separate outputs and have settings for the share. For example mine is set for 30%vehicle battery 70% leisure. If either is fully charged all the output goes to the other.

 

[GeoffnDee]

You could connect the solar controller to the leisure battery and fit a Vanbitz battery master (which is easy to fit) which will take care of the starter battery also being kept charged up when parked.

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[Marauder]

You could connect the solar controller to the leisure battery and fit a Vanbitz battery master (which is easy to fit) which will take care of the starter battery also being kept charged up when parked.

Ok Thanks,

I have been reading these threads for more than a year, but it suddenly clicked when I saw the video on Vanbitz website !

All seems straightforward suddenly, so I think Ill get one & fit as recommended.

But whats difference between Vanbitz battery master and a 'B2B' unit ? Or are they essentially the same ?

 

[GeoffnDee]

Marauder ,They are not the same , a Vanbitz battery master will allow a one way trickle charge into the starter battery from your leisure battery , which will be being charged by the solar when parked. The B2B unit system involves engine alternator charging of the batteries.
The Vanbitz battery master is easy to fit , works well , and I think you can get a Fun member discount, using a code. (check the Fun discount forum).

 

[pappajohn]

If you split the solar output between both batteries it won't last longer than the first time you turn the key to start.
The starter will draw maybe 300amps shared between both batteries and the wire linking them will disappear in a puff of smoke

 

[autorouter]

A BatteryMaster does two things that a simple wire link doesn't. First, it restricts the current flow to a small trickle charge, preventing the huge current surge that pappajohn describes. Second, it has a diode (electrical one-way valve) that prevents backflow from the starter battery to the leisure battery, so if you run your leisure battery flat you can still start the engine.

Some solar controllers like the Votronics Duo are dual-output, and have a second output with built-in electronics to directly connect a starter battery safely.

 

[The Wino]

A BatteryMaster does two things that a simple wire link doesn't. First, it restricts the current flow to a small trickle charge, preventing the huge current surge that pappajohn describes. Second, it has a diode (electrical one-way valve) that prevents backflow from the starter battery to the leisure battery, so if you run your leisure battery flat you can still start the engine.

Some solar controllers like the Votronics Duo are dual-output, and have a second output with built-in electronics to directly connect a starter battery safely.

Theres also this

Votronic Standby Charger 12V https://amzn.eu/d/aIl2uhE

Which seems to do a similar thing in a more basic way.

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[Marauder]

Thanks for input folks,

I think my engine/EHU charges both batts, so what advantage is B2B over what I already have ?

I am easily bewildered, so the items on this page:
Amazon product ASIN B01MCRV17U
certainly bewildered me. Why does one company need to make so many gadgets, when the tasks involved seem essentially very simple ( ie keep the batts charged) !!!

 

[Marauder]

Amazon product ASIN B01MCRV17U

 

[Marauder]

why wont it let me post a link to the amazon page:
Amazon product ASIN B01MCRV17U?

 

[GeoffnDee]

I thought you wanted your solar system to also charge both sets of batteries ? The Vanbitz battery master , and other similar items , will do this in the most simple way.(The Vanbitz battery master works for me , but I do not know about the other types performance )
As has been said , you could also purchase and use a twin output controller to charge both sets of batteries from your solar panel.

 

[Raul]

Thanks for input folks,

I think my engine/EHU charges both batts, so what advantage is B2B over what I already have ?

I am easily bewildered, so the items on this page:
Amazon product ASIN B01MCRV17U
certainly bewildered me. Why does one company need to make so many gadgets, when the tasks involved seem essentially very simple ( ie keep the batts charged) !!!

They make them because there is a need for them.
Without B2B in winter or no ehu I will be stuffed. B2B is essential in those situations.

^{_{Subscribers  do not see these advertisements}}

 

[Marauder]

Yes,
but now that I have re-opened this can of worms in my head (again), I began wondering:
If I spend the cash on VanBM unit - maybe I could spend a bit more and get a MPPT.

currently I have 2x120 PV, each with it's own PWM. Also a cheapo power monitor to show charge rate. (only updates every 10 secs or so)

I would like a better way of showing the power throughput in real time - perhaps digital screen type
and going MPPT has it's own advantages

 

[The Wino]

Yes,
but now that I have re-opened this can of worms in my head (again), I began wondering:
If I spend the cash on VanBM unit - maybe I could spend a bit more and get a MPPT.

currently I have 2x120 PV, each with it's own PWM. Also a cheapo power monitor to show charge rate. (only updates every 10 secs or so)

I would like a better way of showing the power throughput in real time - perhaps digital screen type
and going MPPT has it's own advantages

I've got the Victron regulator that links to your phone by Bluetooth seems to work well. That being said I changed the battery to lithium this year so I can't asses the state of charge on the control panel anymore I just rely on the solar regulator going to float to tell me it's recharged.

 

[autorouter]

Thanks for input folks,

I think my engine/EHU charges both batts, so what advantage is B2B over what I already have ?

You probably now have a 'split charge relay', which is an electrically operated switch that connects the leisure battery to the starter battery/alternator when the engine is running, and disconnects when it stops.. The alternator sees the two batteries as one big battery, and charges them both. The alternator is designed to charge standard lead-acid starter batteries, but will make a reasonable job of charging most other types like gel or AGM.

If you are happy with the split charge relay, that's fine. But if there's a big bank of leisure batteries it can take a very long drive to fill them this way. That's why people fit a Battery-to-Battery (B2B) charger. It's a proper multistage high-power charger that takes power from the alternator in the same way that headlights, wipers etc take power. A B2B can charge at 30A, 60A or more, but you'd be lucky to get more than about 20A from a split charge relay.

Since the B2B doesn't charge the starter battery, it can be set up for the specific battery type of the leisure battery. A B2B is a good idea for a big bank of gels, and is more or less required for a lithium type.

Don't confuse a B2B (high-power charger for leisure battery) with a BatteryMaster which works in the opposite direction. It is a low-power trickle-charger that charges the starter battery from the leisure battery when the engine isn't running.

 

[Ingwe]

Hopefully not poaching this post but one question arises to me: if the B2B charger charges only the leisure battery when the engine’s running i.e. from the alternator, is it solely the alternator that will charge the starter battery (leaving aside a Battery Master or similar device)? I’d wrongly assumed that, when the engine is running, the B2B also charged the starter battery.
Every day’s a school day for me!

 

[Tombola]

Hopefully not poaching this post but one question arises to me: if the B2B charger charges only the leisure battery when the engine’s running i.e. from the alternator, is it solely the alternator that will charge the starter battery (leaving aside a Battery Master or similar device)? I’d wrongly assumed that, when the engine is running, the B2B also charged the starter battery.
Every day’s a school day for me!

no the b2b will charge the battery its outputs are connected to, (leisure) then yes, the alternator will only charge the cab battery.
BUT the alternator is also powering the b2b really, as the b2b is usually connected and takes its power from the cab battery.(that is being replensished by the alternator).

the battery master just operates on its own when evrything is switched off, and trickles to the cab battery from the leisure as long as the leisure is a certain voltage higher than the cab. In turn the leisure is kept topped up by the solar.

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[Marauder]

That's why people fit a Battery-to-Battery (B2B) charger. It's a proper multistage high-power charger

Ok Thanks

it's beginning to make more sense now.

So if i lag out some cash for the vanbitz thing, might as well pay a bit more and go MTTP.

And the B2B idea makes even more sense if I go to AGM Hab Batts. ( current HB's are approaching 10 years old)

Which B2B is recommended ?
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