Adding a second battery?

[Ovey]

Hi all, I've recently added a new fixed VHF and NMEA2K network to my boat. Consequently there's a bit more drain on the battery (not too bad if the engine is running). So I was wondering if it's worth adding a second battery and a 1-2-Both switch to avoid any potential embarrassing moments.

Has anyone else here added a second battery? What is required? Any idea on rough costs? What is involved? Is it a long job? Is it something I should consider doing myself, or something best left to the experts?

Thanks in advance for any input.

[paintman]

Depends on the available room.
I do carry two batteries, the second for precisely your reason. (My Mercury does come with a pull cord but I've never tried it & I'm not sure of my ability to pull start a 2-stroke V6!)
To change, I need to swap the leads from one battery to the other & I carry a correct sized spanner as part of the onboard spares kit. Its simpler than wiring them both in via a switch & you can put the spare wherever is convenient & safe.
So far I've never had occasion to use it & remove & recharge the batteries mid way during the main holiday (3 or 4 weeks duration). When not in use the batteries are off the boat & are trickle charged monthly.

[Lee argyle]

Run the engine on one, auxiliary systems on the second and a link switch in case either need a boost/ flat, simples

P.s. You can get intelligent charging systems that 'manage' the pair or just have them both charging when the engines are running

[Rokraider]

I am running 2 x Odyssey PC2150 Extreme 100 Amp Hour batteries. I have to spin over ba 6.0 litre old school Turbo diesel, that is a hefty lump. I have got both batteries in Parallel via a heavy duty cut off switch. Once the engine is running, it has a 65amp alternator charging and only draws enough current to keep the cut off solenoid activated. This works fine on that setup, probably a bit overkill on an outboard though. I have done the same on my Porter with a Suzuki 140 on the back. On that I have a pair of 70 amp hour batteries in parallel via a cut off switch. Only time I have had a problem is when I left it on a mooring for a week in torrential rain and the bilge pump was going overtime. It still started, but needed a charge.

[Poly]

How long do you ever sit bobbing around with the engine off and electronics on? How bigs the existing battery and what electronics do you have?

[Daniel]

Adding a second battery seams a no-brainer if you've the physical space. It's a requirement on a coded boat; which means it certainly isn't a bad idea !

Altering alternator wiring can be tricky, and that's what you need to do if you want to use an isolation diode. Technology has moved on.

The easiest thing is to add a second battery, a 1-2-both switch and a voltage sensitive relay which will charge batt 2 from batt 1 or visa-versa.

Total project price under £200 including a battery box.

It's essential up to you what you power from each battery. "Ballistic" had everything from the "1" or "2" depending on your switch selection. Handy being safe on the knowledge you had a 2nd fully charged battery to hand at all times.

There are various other configurations; the most common alternative to take whole "domestic" (GPS, VHF...) from batt "2" and leave batt "1" just for engine. You'll still need the voltage sensitive relay; and id highly recommend the 1-2-both switch too as it allows you to start the engine from either battery.

[Ovey]

Poly - I have a 75Ah leisure battery and I have Nav lights, Anchor light, Chartplotter (all on switches), a bilge pump (on a press+hold on/off/auto switch), VHF radio (running directly from the busbars but using it's front panel on/off/volume knob) and an NMEA2K network (permanantly powered once battery switched on). As you say, it's not an issue while running, and I'd like to think I turn it off when unattended (I'm usually pretty good at being anal in that respect!) but it's in case of the forgetful moment. At most it would be the chartplotter and VHF accidentally left on and the bilge pump in auto while at the beach during the day.

Daniel, thanks for the info. I would have space as my console is fairly roomy and has room for another battery box next to the one currently installed. I was thinking of rigging it (if possible, without having investigated fully yet) so that the whole setup can be powered as is currently set up with one battery for starting and domestics, but from a choice of 1, 2 or both with a 1-2-both switch. (I think this would be less wiring and hassles?).

Would anyone recommend moving the battery(ies) up onto a shelf of sorts? The current one is in a box on the bottom floor of the console at the moment.

[boristhebold]

Having two batteries with a single engine is definately a good idea, when I bought my boat I fitted a second battery and a simple switch to switch between the two, 3 months after that I had a battery fail on me when crossing the entrance to poole harbour outbound, my electronics went off and engine started to splutter and run very badly, having the second battery I simply switched and all was well.

After that I installed what I would recomend a Bep Marine 716 switch cluster with a voltage regulator. The idea is one battery becomes the engine start battery and the other battery feeds the electronics etc, so you switch both on, in an emergency you can use the juice from both by switching both to run together, the voltage regulator part simply looks at the batteries and determins which one needs charging and does so automaticaly. That way one batt doesnt drain the other. I also ran a cable to my console with a small led light so i could easily see when the charging was going on as there is a monitor feed from the unit.

Have a look for Bep Marine 716 clusters and info on the internet, worth the investment.

Top tip, buy a decent crimper for both the batt terminals and the other terminals. Also consider if your boat is on the water for long periods of time consider rigging your auto bilge pump if you have one to a permanent on batt supply with a simple switch, that way when you have finished boating for the day you simply turn off the main battery switches on the cluster but turn on a small switch for perm supply to the auto bilge pump so that the only thing that is on is the auto bilge pump and no power is being supplied any where else, that is what I did using the auto bilge pump switch on my console switches and using a perm fused power block in the console for the feed.

[Rokraider]

Originally Posted by Ovey

Poly - I have a 75Ah leisure battery and I have Nav lights, Anchor light, Chartplotter (all on switches), a bilge pump (on a press+hold on/off/auto switch), VHF radio (running directly from the busbars but using it's front panel on/off/volume knob) and an NMEA2K network (permanantly powered once battery switched on). As you say, it's not an issue while running, and I'd like to think I turn it off when unattended (I'm usually pretty good at being anal in that respect!) but it's in case of the forgetful moment. At most it would be the chartplotter and VHF accidentally left on and the bilge pump in auto while at the beach during the day.

Daniel, thanks for the info. I would have space as my console is fairly roomy and has room for another battery box next to the one currently installed. I was thinking of rigging it (if possible, without having investigated fully yet) so that the whole setup can be powered as is currently set up with one battery for starting and domestics, but from a choice of 1, 2 or both with a 1-2-both switch. (I think this would be less wiring and hassles?).

Would anyone recommend moving the battery(ies) up onto a shelf of sorts? The current one is in a box on the bottom floor of the console at the moment.

You need to keep the centre of gravity in mind when you start raising something heavy like batteries.

[Ovey]

Thanks for that Boris - that looks a simple(ish) solution that seems to tick all the boxes. Do you have any wiring diagrams at all, or did you get those from the net too?

[Ovey]

That was something I had thought of Rokraider, but what is best - two batteries on the deck in battery boxes, or two batteries raised off the deck? I'm in two minds there.

Obviously the boxes aren't waterproof once the water gets to the top of the box, but the console is sealed up to about the same height too (obviously not sealed above the level of the hatch into the console). Raising the batteries does lift the COG up, but is it worth doing in order to give the batteries a bit more protection?

The chances are that I'll be out in mild to good weather with the boys so not likely to fill the boat, however there will be the occasional chance to play when I get a chance - but I'm still not likely to be doing silly things.

[Rokraider]

On my Porter I have them under the drivers seat inside the seat box. They are mounted on a wooden frame on the deck to keep them in place, with straps keeping them in place. Not had any problems with water ingress yet and I take it out in lumpy conditions often .

[Poly]

Originally Posted by Ovey

Poly - I have a 75Ah leisure battery and I have Nav lights, Anchor light, Chartplotter (all on switches), a bilge pump (on a press+hold on/off/auto switch), VHF radio (running directly from the busbars but using it's front panel on/off/volume knob) and an NMEA2K network (permanantly powered once battery switched on). As you say, it's not an issue while running, and I'd like to think I turn it off when unattended (I'm usually pretty good at being anal in that respect!) but it's in case of the forgetful moment. At most it would be the chartplotter and VHF accidentally left on and the bilge pump in auto while at the beach during the day.

So why do you believe you would be less likely to forget to switch to a single battery than switch off?

If we assume its not raining hard and the boat is not shipping lots of water then the bilge pump isn't running without being on manual.

The VHF uses relatively little when not transmitting. Probably < 0.5A
The chartplotter - a quick look suggested ~ 0.5 A is probably a reasonable guess although a really big one with a sounder etc might be using a bit more when the backlight is on - but if the screen is lit you are more likely to notice it.
Nav/anchor lights won't normally be on when you are at anchor.
I don't think the NMEA network itself will have any appreciable current draw on the timescale we are discussing.

So you are probably using at most 1A at a time. If we can assume that you arrive at the beach with a fully charged battery, and are worried it might drop below 50% you'd expect to be able to sit there for 37 hrs! So not a big worry. Even if you left the nav lights on and the bilge pump running you'd comfortably have 5+ hrs before you were at risk of an issue.

Now people do report issues with battery systems so I'd consider if your investment would be better served:
- making sure you have a good quality battery isolator and it is fitted somewhere that is protected from water ingress.
- having a way to bypass the switch if you need to (they are one of the main points of failure)
- having a way to monitor battery charge and charging (and a routine to monitor it).
- knowing how (and practicing) pull starting the engine (possible on even some of the biggest beasts)
- if its not possible then consider is a small jump start pack in a locker is more flexible.

Now if you were running bait wells or fridges at anchor etc then I'd be looking at a twin battery set up.

[Ovey]

Good points there, and well worth thinking about Poly!

You're right, I am just as (un?)likely to forget the battery switch as I am the panel switches, so maybe the act of switching off isn't the thing that is the most concern (especially when you break it down to the numbers as you have, which gives me a better peace-of-mind if I should leave anything on while at the beach or wherever).

I do have a good quality battery isolator fitted (a BEP isolator switch) and this is inside the console at a height probably above a swamp-line, so hopefully this shouldn't fail. (The battery box would flood before the switch got wet).

I have a short length of battery cable in my onboard toolbox which should allow me to jury-rig something if the need arises.

As for monitoring charge, the only thing I have is the battery voltage level indication on the Yamaha engine guages - I can see it jump from around 12.4V up to 13.8V when the engine starts, but there's no dedicated charge indication as such.

Jump starting is the thing that would make me question myself. I think I'll investigate how to jump my Yam F115AETL (the manual states you can, but doesn't tell you how; it also tells you there's a pull cord in the cowling but there isn't (not sure if there was when new)).

I must admit, so far the boat has been a great starter - first time every time - but the thoughts of a second battery were for the "what if" scenario. It does sound as though (barring a completely failed battery) I might not need one.

[boristhebold]

Originally Posted by Ovey

Thanks for that Boris - that looks a simple(ish) solution that seems to tick all the boxes. Do you have any wiring diagrams at all, or did you get those from the net too?

The 716 cluster came with instructions, plus I also downloaded something from the Bep marine website which helped, always helps mapping it out on paper before you begin. I will see if I still have the downloads and will send to you.

[boristhebold]

Originally Posted by boristhebold

The 716 cluster came with instructions, plus I also downloaded something from the Bep marine website which helped, always helps mapping it out on paper before you begin. I will see if I still have the downloads and will send to you.

here it is, the horizontal cluster version.

[boristhebold]

and this link maybe useful, someone who put online some stuff when they were doing a wiring project.

BEP 716/Documentatiion - Bluewaterpirates Albums

[Ovey]

Thanks for that Boris, I'll have a look and decide whether it's something I'm going to do or not (based on other advice on this thread). But I appreciate you digging the info out for me!

[Searider]

Ovey,

The simplest and most reliable way is to fit one of the BEP clusters.

I have this on my boat and it's perfect.

I run off either one battery or the other battery. Once the engine has started it will begin to be charged. Once it's voltage has risen to a set level the voltage sensing relay closes and the second battery then starts to charge.
The in service battery is always powered up as we keep the boat afloat on a mooring.
On the few occasions that the bilge pump has flattened the battery its been a simple task to switch that battery off and switch the spare on.

Periodically (every couple of weeks) I will swap over to the second battery and use that as the primary for a while.

has worked for me as the secondary battery is always fully charged.

[Ovey]

Thanks Searider. I think the thing that is putting me off is getting the time to do it at the moment (and the expense of doing it close to Christmas). I like the idea of having redundancy for the battery though, so it's probably something that I will get round to doing.