Connecting battery charger to 2banks

[Escapade]

Hi, i did recently buy a Bavaria 35 exclusive (1997) equipped with Calira Panel 420 and battery charger Calira LG 727.
To my surprise the schematic of the panel (see attached picture) shows only connection to the house bank and not to the engine battery
The engine battery is only charged by the alternator.
Is this setup common to other bavaria models?
What is the best way to occasionaly charge the engine battery in winter time without starting the engine?
Just put it in parallel to the house bank or fitting a Battery combiner?
Cheers

[Yngmar]

You can fit a VSR (Voltage Sensing Relay, around £40) that will bridge the banks if a charging voltage is sensed and separate them if not. This is probably the most common solution these days. Alternatively you can also fit a B2B (Battery to Battery) charger that will trickle charge one from the other. This is typically a bit more expensive and charges slower. It is mostly fitted if the battery banks have different chemistry so require different charging regimes.

[Escapade]

Thank you Yngmar
That is what the local chandler is proposing, a Cirix 80A by Victron.
Do you have experience with that sort of component? Are VSR reliable?
If for any reason it fails to disconnect the two banks there may be the risk of having both flat and be unable to start the engine.
Is this a real risk, or am I excessively worried?

[Yngmar]

VSRs are widely fitted on a lot of boats and no cause for concern. If they fail, they tend to fail the other way, i.e. they stop combining batteries rather than leave them combined. Victron is generally very good quality and the Cyrix-CT seems to have a nice feature set over a simple VSR. Would go with that.

[Lyra]

While you can fit some kind of a permanent solution as advised above you can go the simple way of holding a pair of regular car battery jumper cables - in case of need simply connect between the banks. You actually need only one cable as the minus is common to both banks - this is my setup.
If you are only concerned about the self discharge over long periods of non use than another option is a very small (say ~5W or even less) 12V solar panel - just connect it via a diode to the battery. At this panel size compared to battery capacity there is no need for a charge controller. This s what I did when had to leave the boat ashore over winter in Greece - placed it over the cockpit hatch with a thin cable an alligator clips to the batteries.

[Escapade]

Thanks Yngmar and Lyra for the useful advices.
Happy new year.

[Jeff Jones]

Hi. During the summer I upgraded my house batteries, in doing so I wanted to look after the new batteries 2x150Ah properly and to get the best charging out of the VP engine alternator.

The factory fitted diode splitter drops (loses) 0.7v across the diode meaning you never get a full charging voltage across the batteries (even with a Alternator sensing wire connected yellow wire on VOLVO PENTA)...so I removed the diode splitter and installed a VSR, which works great. Its a fit it and forget it piece of kit.
(The old diode splitter is blue with 3x red wires shown in the last photo).

The VSR only 'Switches In' (closes) when the voltage is above 12.7v, above this the starting and house batteries are combined for charging from a single charger (shore) or engine alternator or even solar charger..

Once the voltage drops below 12.7v the VSR opens and disconnects the two battery banks.

I made some changes to the attached circuits, in that the isolators for each of the batteries are connected directly to each battery + terminal, that way I can isolate each battery even when the battery voltage is above 12.7vdc.

There is a emergency shorting switch to combine the battery banks should the starting battery be flat (yellow switch).

I hope this helps

[Escapade]

Thank you jeff jones.
From your schematic I understand the engine alternator feeds the engine battery first and when voltage is above 12.7 the VSR connects the engine battery with the house battery.
Do you also have a battery charger connected to the mains?
If yes, does it feed the house battery first and when voltage has reached the pre-set treshold the VSR connects both batteries?

[Jeff Jones]

Hi Escapade. your welcome.

I am on a swing mooring, so only tie up at a jetty once every few months to do the tanks and give the house batteries a good top up.

I do have a shore power charger which is connected to the engine battery, but my understanding of the VSR its bi-directional.
ie, if it see's above 12.7 on either battery it closes to link them together - so in reality when charging the engine battery the charge voltage will nearly always above the 12.7vdc unless a battery is really drained or in a poor state.

I point to note, since installing it I have got in the habit - once I turn the engine off I also turn off the engine battery isolator.
Because, After charging from any source the battery volts stay higher than 12.7 for quite awhile and after watching the battery monitor I noticed current flowing from the engine battery (70Ah) into the house bank (300ah).

This I GUESS is because the cranking battery was fuller than the house bank and the batteries were trying to equalise themselves. ie the cranking battery with a higher SOC trying to charge the house batteries with a lower SOC (state of charge)

Without going into a long explanation - Batteries when connect to a power source will only draw the current they required to replace the charge taken out - so the Lead Acid cranking battery is charge back up quite quickly, were as my house AGM's take alot longer, but because I mainly charge from my engine alternator I make sure that I only run the engine long enough to replace the AHrs taken out of the house bank.

When charging at the jetty I generally stay over night to allow the '4stage' mains charger to properly recharge the batteries.
Once completed I always notice it has put back in more Ahrs than the battery monitor says we've used in total.

At the moment I am happy with my charging set up, but I planned to add a solar charger too so I wouldn't need to go to the jetty to top off the house batteries..am still trying to decide on which flexibly panels to use? and were best to place them.

All the best, Regards Jeff

[Escapade]

Thank you for the explaination.
I am becoming more confident on the use of a VSR.
Perhaps i will also add a switch to combine both batteries in case of need (as you did) instead of using a car joker cable.
Cheers

[Salty]

I fitted an emergency start crossover switch on my B36 some years ago to comply with an apparent requirement for my charter boat (as it was at the time) to be fitted with such system. The arrangement was as posted at :-

http://bavariayacht.org/forum/index.php/topic,1921.msg11853.html#msg11853

[Escapade]

Thank you Salty
My batteries are located under the starboard settee as it is in your boat. See picture.
I could then install the switch exactly where you have it and keep the key in the chart table, as I will connect the batteries only in case of emergency start.
Cheers

[Salty]

You're welcome, but for what it's worth, the system was fitted in 2010 just after I bought my boat and to my knowledge it has never ever been used. Sort of belt and braces really as the only time I needed starting power and didn't have it was when my boat was ashore in winter. A replacement battery was just a ten minute drive away, such that in under an hour the old battery was out, a new one purchased, installed and ready to go for the following weeks launch date. But it's nice to know the system is there should the need arise.

[Yngmar]

Perhaps i will also add a switch to combine both batteries in case of need (as you did) instead of using a car joker cable.

No need - if you read the description of the suggested Victron VSR, it already includes this functionality.

[MarkTheBike]

Hi all,

I've read the Victron Cyrix info sheet and a VSR seems like a good idea, but what are the implications (if any) of having one in a 'standard' Bavaria setup (i.e. alternator + splitter + charger + batteries)? I don't have solar or wind power and my charging tends more towards shore power (leisure only) than motor. Should I, a) get one?, and b) set the leisure pair as Battery 1 (87)? They are the ones I use most so to me it makes more sense to charge them fully then top up the starter. Or doesn't it work that way? Would the Victron interfere with the splitter in any way? Any thing else I should be aware of?

Cheers

[Jeff Jones]

Hi Mark.

Before doing my upgrade, I did a lot of research about house batteries types AGM's LiPO4s etc there optimum charging methods and also how we use in practice both draining and charging..

if you mainly charge from shore power your current set up should work fine, as long as you use a good 4 stage charger.
The main difference is that the VSR would be installed close to the batteries, you would need to disconnect the splitter and change the connection of the 3 red wire on the splitter. But that's about it.

FYI
As an electrical engineer, I didn't like the Bavaria charging method which was a compromise and it wasn't charging the batteries efficiently from the engine.

I made the change when I upgrade my VP engine (with a bigger 115A) alternator and also increased the house battery bank upto 300Ahr

The splitter diode will not pass current back from one battery to the other - so check which battery your charger is connected to.
With a diode splitter current will only flow one way..with a VSR is flows both ways (a simple switch)

A VSR is used to replace the diode splitter so to combine and disconnect the two battery banks based on there voltage >= 12.7 (full battery volts)

The VSR doesn't have a voltage drop across the switch (a diode splitter loses 0.7v in splitting the voltage via a diode).
This 0.7vdc loss is important because when an alternator producing 14.5v - the batteries would only get 13.8v which is not enough to properly bulk charge the batteries (the bulk charge voltage setting is slightly different for wet lead acid, AGM's or other battery chemistries)
The alternator manufacturers tried to compensate for this loss by using a yellow sensing wire so that the voltage produced by the alternator was 0.7v higher + what every volts drop there was because of the cable length.

if you want to discuss it on the phone, feel free to PM me.
Jeff

[MarkTheBike]

Hi Jeff

Many thanks for the info. Sounds like it'll be a good idea so I'll order one but won't have time to fit for a few weeks. I still have the original Calira charger (can't remember the model offhand) and had that tested a couple of years ago, which is working fine. There's still a few questions I have but your post has filled in a lot I didn't know. I hadn't appreciated the significance of the voltage drop, which raises the question why splitters are fitted rather than VSRs? I also note your comment about the yellow wire. I don't remember seeing one (MD2030D/2001) but will have a closer look next time I'm down there. PM sent...

Cheers