Adding a second battery

[Jim570]

Well another season is over and the rib is on the trailer and engine winterised and I'm starting to think about jobs that need doing before next year.

The boat is normally on a swinging mooring from April until October. I try and get out every week or so but with a young family that can be challenge so there are times when it sits for 4 weeks or so without running. I've never had problems with the battery until this year, but a couple of times this year I've found the battery flat (or at least too flat to start the engine).

I'm pretty sure the cause is a combination of the battery not having been properly conditioned over winter and the auto-bilge running whilst it's left.

We have a single battery and the auto-bilge is wired as permanent live even when the battery isolator is switched off!

I want to keep the auto-bilge free to run as much as it needs but without risking running down the starting battery. I also don't want to get too deep into too much re-wiring.

Having done a bit of reading, I think the simplest thing would to add a second battery and one of these:

https://marine-electricals.co.uk/product/bep-battery-distribution-cluster/#

As far as I can see, this would allow me to leave the boat with Battery 2 connected before switching to Battery 1 to start. Both batteries would change when underway.

I could presumably wire the Distribution Cluster in between the batteries and the existing isolator (from which everything takes its feed).

Anything else I should be thinking of?

[Pikey Dave]

Originally Posted by Jim570

Well another season is over and the rib is on the trailer and engine winterised and I'm starting to think about jobs that need doing before next year.



The boat is normally on a swinging mooring from April until October. I try and get out every week or so but with a young family that can be challenge so there are times when it sits for 4 weeks or so without running. I've never had problems with the battery until this year, but a couple of times this year I've found the battery flat (or at least too flat to start the engine).



I'm pretty sure the cause is a combination of the battery not having been properly conditioned over winter and the auto-bilge running whilst it's left.



We have a single battery and the auto-bilge is wired as permanent live even when the battery isolator is switched off!



I want to keep the auto-bilge free to run as much as it needs but without risking running down the starting battery. I also don't want to get too deep into too much re-wiring.



Having done a bit of reading, I think the simplest thing would to add a second battery and one of these:



https://marine-electricals.co.uk/pro...tion-cluster/#



As far as I can see, this would allow me to leave the boat with Battery 2 connected before switching to Battery 1 to start. Both batteries would change when underway.



I could presumably wire the Distribution Cluster in between the batteries and the existing isolator (from which everything takes its feed).



Anything else I should be thinking of?

That should do it, Blue Sea also do an “Add a Battery” kit, which is similar but more expensive. I’d also take the opportunity to check the existing wiring. Make sure it’s tinned copper strand, adhesive lined heatshrink crimps, adequately sized etc etc.

[Jim570]

Thanks, that is helpful!

[GuyC]

+1 on what PD says.

A lot of people wire their auto bilge pump to the battery side of the isolator. This means you can isolate the rest of the 'hotel' circuit but still have the auto bilge pump operational.

[Peter_C]

A 2nd battery is nice to have and a simple relay to isolate it works great, BUT a solar panel and regulator would still be needed to charge both batteries. The goal is that they remain at full charge therefore keeping them in top condition. Running a battery down past 1/3 charge kills them quickly.

[neil.mccrirrick]

My boat is on a pontoon from approx april to end Oct. No shore power available. I do have two batteries with the blue sea solution, however I've opted for an alternate solution to manage time away and rain etc

I've a cheap bilge pump wired to a battery on deck. The cheap pump is held down by a weight.

This allows all boat electrics to be off, I take the pump abd battery off before setting off for the day. When the stand alone battery goes flat its a, simple matter to take it home to charge and leave the boat on its built in bilge for that period



Sent from my AGS-L09 using RIB Net mobile app

[Iankristy]

This is meant in a friendly and helpful sense [emoji4]🤣
I might have misinterpreted your question but seems like your asking how can I make sure the bilge doesn’t drain my batteries so I can start the outboard when I get to the boat? First off if I had my rib in a swinging mooring I’d be at least every week if not twice a week needing to go check all ok. Secondly the bilge working is way more important than you being pissed off when you can’t start your outboard. Heavy rain will fill and destroy your boat with no bilge pump. Above [emoji115] advice about solar panels is where I would be focussing my attention. That and giving your boat more love[emoji23]

[ShinyShoe]

How critical it is to have the bilge pump working presumably depends on the effect of the bilge being full. For some boats that's a virtually sunk boat and flooded electrics etc. For some boats that's wet feet and maybe some manual bailing with a bucket.

But, inability to start the engine might equally be a serious issue if your bilge has then filled and you probably can't easily bring it ashore to sort...

I'd suggest a small solar is a good option but may not be enough if the bilge pump is going bananas. A second battery will add resilience. Personally an isolator switch just gets forgotten to be switched and so may not work for me. I'd look at a split charge relay e.g. https://www.ebay.co.uk/itm/284951168...mis&media=COPY

That will charge the second battery when your engine is running but disable the link when it stops. You'd connect the bilge pump to that (and probably better to be a leisure than a starter bat). You should be able to get a VSR with an override that will allow you to use the leisure to start in an emergency but I can't see one on eBay!

[Jim570]

Hi thanks for all the detailed replies.

The missing piece of information in my original post was probably that I have a self draining deck so the bilge doesn't get a huge amount of work. There is rarely a great deal of water in the bilge locker even after heavy rain which is one of the reasons I was surprised to have had battery problems this year.

I've never had a problem with the bilge running down the battery in previous years so I suspect the problem has been caused in large part by the battery having lost condition over winter.

Adding a second battery would add a bit of reliance hopefully.

I think solar panels might be a bit overkill given I've not had problems before this year and the bilge gets fairly light work, although if the leisure battery is getting run down too heavily I will need to rethink that I suppose!

I'll have a think about VSR vs manual switch. I like the simplicity of a manual switch and I'd like to think I'm pretty good at remembering stuff like this when leaving the boat.

It will be spring when I come to fit whichever solution I go for and I'll update then for the benefit of anyone searching this topic in future.

As for leaving the boat on the swinging mooring, I see what you're saying but it's sheltered spot. There are plenty of boats left on the surrounding moorings for months at a time by the second home owners etc. It's got two lines on to the mooring and I get out to it regularly and certainly if there is heavy weather coming in.

[GuyC]

Originally Posted by Jim570

I'll have a think about VSR vs manual switch. I like the simplicity of a manual switch and I'd like to think I'm pretty good at remembering stuff like this when leaving the boat.

I'm not sure about the BEP one but the Blue Sea Add a Battery kit has a few advantages over a simple manual switch. Whilst remembering to turn the batteries on / off at the beginning / end of the day is something you will still have to do, the auto charging relay will also combine the batteries for charging and isolate them for starting. I guess you can do this via a manual switch but the automation is pretty straight forward. Has anyone got any bad experiences of charging relays?

I was always slightly nervous about arriving after having not been to the boat for a few weeks to discover a flat battery so I bought myself a NOCO jump starter. So far it has been a £200 ornament in the back of the car.

[Pikey Dave]

Originally Posted by Jim570

Hi thanks for all the detailed replies.



The missing piece of information in my original post was probably that I have a self draining deck so the bilge doesn't get a huge amount of work. There is rarely a great deal of water in the bilge locker even after heavy rain which is one of the reasons I was surprised to have had battery problems this year.



I've never had a problem with the bilge running down the battery in previous years so I suspect the problem has been caused in large part by the battery having lost condition over winter.



Adding a second battery would add a bit of reliance hopefully.



I think solar panels might be a bit overkill given I've not had problems before this year and the bilge gets fairly light work, although if the leisure battery is getting run down too heavily I will need to rethink that I suppose!



I'll have a think about VSR vs manual switch. I like the simplicity of a manual switch and I'd like to think I'm pretty good at remembering stuff like this when leaving the boat.



It will be spring when I come to fit whichever solution I go for and I'll update then for the benefit of anyone searching this topic in future.



As for leaving the boat on the swinging mooring, I see what you're saying but it's sheltered spot. There are plenty of boats left on the surrounding moorings for months at a time by the second home owners etc. It's got two lines on to the mooring and I get out to it regularly and certainly if there is heavy weather coming in.

If you have a manual switch, both batteries will run down at the same rate when the switch is closed. I.e. if you’re out on the boat, engine off at anchor, instruments/radio/music on, the starter battery will be discharging at the same rate as the house battery. If you have a VSR, the VSR will automatically disconnect the starter battery from the house battery when the engine stops, or soon after when the voltage starts to drop. Paradoxically the VSR is the “simpler” of the 2, as it’s completely automatic & requires no human input.

[Peter_C]

Not a fan of manual switches myself, as it is one more thing to remember to switch on and off. Battery isolator/combiners are the solid state way and better than what a relay does, but either would be my choice. I had my Nautique set up with a Hellroaring isolator/combiner that worked great in that it was completely isolated, unless I turned a switch on to combine them, otherwise the batteries were never connected together. The second battery charged thru the isolator without the ability to back feed.
https://www.hellroaring.com/battery1.php

Letting a battery sit over winter will drop it to maybe half charge if it is in decent shape, and it should recover nicely with a charge. Actually if disconnected I would expect to barely see any loss in a few months of down time. Killing a batteries voltage completely destroys it immediately, and it will never hold as many amp hours ever again. Small solar panels are like $40 US dollars, with a charge controller, and the only true solution for keeping a moored boat battery alive. Hide the charge controller inside a hatch, and leave the solar panel out in the sun. If someone steals it you loose $20 *shrugs* You can do that 6 times before coming close to the cost of replacing an AGM battery. Heck I would probably throw the solar panel on and not put a second battery in. $40 vs $250 or more, and 10 minute installation time vs hours. Your call...

[GuyC]

Originally Posted by Peter_C

...out in the sun...

In the UK we struggle with that concept.

I think we are all advising from the same hymn sheet though.

[Pikey Dave]

Originally Posted by GuyC

In the UK we struggle with that concept.



I think we are all advising from the same hymn sheet though.

I think that most people don’t realise we’re on the same latitudes as Newfoundland[emoji848]

[Peter_C]

Originally Posted by GuyC

In the UK we struggle with that concept.

I think we are all advising from the same hymn sheet though.

I struggle with the concept of living where there is no sun

Living in a Mediterranean climate is awesome with sun and fun! Of course it is raining today...

Bought 4.5kw worth of solar panels for our house yesterday with hopefully less than a 2 year ROI which is $$$ in our pocket. Have used a solar panel in an Audi A4 I rarely drove to keep it charged.

[paintman]

Have we established how old your battery is?