voltage sesitive relays

[cagey]

more advice please
following earlier recommendations I've decided to rehash my batteries. I have: 1 x 70 amp Engine start, 2 x 110 amp domestic all 12v, charged by a 50 amp alternator through a sterling reg and a splitter diode.
I would like to add an extra 1 x 110 amp domestic and would like the opinions about fitting a VSR, how to wire it in,what to do with the diode and any other thoughts you may have, perhaps a different approach. My boat lives on a swinging mooring and we dont need to motor that much, so recharging is limited." magic wand time please "
Thanks
Keith

 

[pvb]

The VSR will replace the splitter....

The VSR will replace the splitter diode. The output from the alternator will go direct to the starter battery (instead of to the input terminal of the splitter diode). The old connections from the splitter diode to the two battery banks are discarded. The VSR is wired between the two battery banks - be sure to use heavy cable for this. Note that VSRs are usually uni-directional, so you need to ensure that the sensing side is connected to the start battery. The extra domestic battery is simply wired in parallel with the 2 existing batteries. The Sterling sense wire can remain where it is.

What will then happen is that, after starting the engine, the start battery will recharge and (when it gets to a certain voltage) the VSR will close, allowing all the batteries to charge together. When you turn the engine off, the VSR opens and isolates your start battery from the domestics.

 

[Anonymous]

Going for the extra batteries is very wise for a cruising yachtsman, especially on a swinging mooring, but with only a 50A alternator and low usage of the engine, you are going to find yourself short of charging capability. Solar panels are almost a 'must have' to keep those batteries in good condition. If you don't get them up to 100% charge for four or five hours every few days the batteries will deteriorate irreversibly. Assuming that you have sized your batteries for the sort of load you want to run, then your solar panel(s) will have to be of a good size - consider a 100W panel. Another approach would be to use a small petrol generator plus a smaller solar panel - say 50W panel. The Honda range are a dream but they are pricey. If you search on the forums here you will find recent threads discussing bargain generators. There are different opinions about the safety of running small petrol generators - in my view they are perfectly safe if you use them safely /forums/images/graemlins/smile.gif

I haven't mentioned wind generators - the truth is that I have never heard anyone bemoaning solar panels but the same cannot be said of wind.

 

[William_H]

If you find the splitter diodes work OK at present using the smart regulator then it would seem a shame to change things. The new battery could simply be connected in paralell with the existing domestic batteries however if you want it to be discharged isolated from both the domestic and engine battery then connect it to the domestic or engine battery via a VSR to have the new battery charged. PVB's arrangenment proposed will require a VSR with at least 3 isolated battery connections. If it only has 2 battery connections you would be no better off than at present.
Regarding solar I use solar on my yacht on swing mooring because I don't use a motor and have no other charger. But it is with a small battery and 2 watt panel. Solar are good if you want to leave the boat unattended for long periods and keep batteries healthy but would be very big and expensive to provide real power. I reckon you might find that the engine generator is the best arrangement, stick with it. You need to use the boat for a few seasons to find your personal boating patterns to find the right answer but don't rush in to wind or solar. regards olewill

 

[brianhumber]

I would agree it will be a struggle IMHO to keep all those lead plates fully charged. I was on a SM in Itchenor and found it difficult to keep 2 dom and 1 engine batt charged ( mostly I do Xchannel overnighters) so I removed 1 dom and problem solved itself using the engine just to and from say east head to the SM.

All I have is simple on off switches being adverse to complication, this suites me but then I still nav using only log, depth, pen and paper, the GPS and radar only being switched on if I am bored or vis is bad. Simple cheap £65 Van batteries last about 5/6 years doing this, I put any new ones on the 'engine' side and swop the old engine one onto the nominal 'dom' side. Its a matter of not running them down and strict self displine in useage. The price of batteries had not gone up since I bought RH in 95 but last years raw materials hike due China buying up everything has changed that for this year.

 

[Anonymous]

[ QUOTE ]
I would agree it will be a struggle IMHO to keep all those lead plates fully charged. I was on a SM in Itchenor and found it difficult to keep 2 dom and 1 engine batt charged ( mostly I do Xchannel overnighters) so I removed 1 dom and problem solved itself using the engine just to and from say east head to the SM.

[/ QUOTE ]I think the issue for cagey is that he wants more electricity for lifestyle or nav kit - that's why he wants the extra 110Ah battery. He knows that it will be a challenge - as he put it, "magic wand time". On a swinging mooring in Cornwall, I'm not sure how he is going to keep 330Ah of domestic battery charged if the capacity is in use. Suppose he is 50% discharged, he has to provide 165Ah net, assuming a charge efficiency of 85%, that makes nearly 200 Ah gross. i.e. his alternator running flat out at 50A for four hours. Most alternators get hot and tail off so he probably won't get 50A for long, anyway. (the Sterling does not overcome the temperature effect of the alternator). If he wants to use the capacity he is asking for, I can't think of a viable alternative to an extra large solar panel and petrol generator - unless he wants to run the main engine for hours, which is an option, I suppose.

 

[pvb]

VSRs don\'t have 3 outputs...

Sorry, Will, I obviously didn't explain very clearly. Cagey's question, as I believe he originally put it, was that he wanted to add a third domestic battery, and use a VSR rather than a splitter diode. He would still only have 2 battery banks - a starter (1 battery) and a domestic (3 batteries in parallel). VSRs are simply an easy no-loss way of connecting the two banks for charging. There's some info on VSRs here on the Merlin Equipment website.

 

[halcyon]

Re: VSRs don\'t have 3 outputs...

Not an advert, but we make them for upto four battery banks, plus other functions.

Brian

 

[pvb]

That\'s useful to know...

That's useful to know, any info available on t'interweb? Are the outlets isolated?

 

[cliff]

[ QUOTE ]
more advice please
following earlier recommendations I've decided to rehash my batteries. I have: 1 x 70 amp Engine start, 2 x 110 amp domestic all 12v, charged by a 50 amp alternator through a sterling reg and a splitter diode.
I would like to add an extra 1 x 110 amp domestic and would like the opinions about fitting a VSR, how to wire it in,what to do with the diode and any other thoughts you may have, perhaps a different approach. My boat lives on a swinging mooring and we dont need to motor that much, so recharging is limited." magic wand time please "
Thanks
Keith

[/ QUOTE ]Not withstanding the info on VSRs, I would seriously look at changing the alternator to something like 90A (or even 125A if you have room for the larger frame). Unfortunately neither your bio nor your post gives any information on the engine fitted.
----------

 

[pvb]

That\'s maybe a bit OTT...

Think that's maybe a bit over the top, Cliff. Even with 330Ah of batteries, Cagey will be unlikely to achieve any more than 50A charging current, regardless of how big his alternator is, unless he replaces his batteries with expensive AGM types.

According to previous posts, his Sigma has a Volvo 2003 engine, and these use a small-case alternator with a single 2" foot. It would be feasible to fit a higher output small-case alternator, but anything over 80 or 90A would need a double V-belt drive, and this would be difficult if his engine is fresh-water cooled, because the V-belt also drives the water pump.

A bigger alternator would only make real sense if he also increased the size of his domestic bank. As I've said before, once you've got a smart regulator, the next most cost-effective improvement you can make to a boat's electrical system is simply to add battery capacity.

 

[Anonymous]

Re: That\'s maybe a bit OTT...

[ QUOTE ]
As I've said before, once you've got a smart regulator, the next most cost-effective improvement you can make to a boat's electrical system is simply to add battery capacity.

[/ QUOTE ]I agree, but only if the batteries get fully charged and equalised at least every few days. It will be impossible for cagey to manage that if he doesn't add some charging other than the engine alternator.

Alternatively he could spend one night in every three in a marina - before we had all the liveaboard comforts we always used to do that to enjoy showers, shopping, etc. He would need to size his charger to cope with the charging and providing the house load overnight, though. He will probably need 30A, maybe 40A.

 

[roger]

Sterling 3 way splitter diodes

Just adding another battery is perhaps done most simply by substituting a 3 way for the 2 way diode splitter. I have a 3 way Sterling - it works. It quite large though. I dont know if Cagey has a much increased power need or is just getting security by splitting up his battery supply end. Various recent posters have indicated that small petrol generators are available pretty cheaply. Solar panels would have to be pretty large to cope with the demand other posters have suggested.

 

[pvb]

Equalisation...

This equalisation business has always intrigued me. I only have an old 25A mains charger, with no fancy settings. I never leave it connected to shorepower (indeed I rarely connect it to shorepower). So I've never knowingly equalised my batteries. But they still seem to work fine. Which makes me wonder whether equalisation is as necessary as it's sometimes claimed.

 

[pvb]

That\'s not the best way...

That's not the best way to wire extra batteries. They shouldn't be isolated. For maximum efficiency, extra batteries should just be added in parallel to the domestic bank, so you end up with one big domestic bank. The bigger the bank, the longer it'll last (because individual batteries' depth of discharge will be less for a given load).

 

[Anonymous]

Re: Equalisation...

[ QUOTE ]
This equalisation business has always intrigued me. I only have an old 25A mains charger, with no fancy settings. I never leave it connected to shorepower (indeed I rarely connect it to shorepower). So I've never knowingly equalised my batteries. But they still seem to work fine. Which makes me wonder whether equalisation is as necessary as it's sometimes claimed.

[/ QUOTE ]All you are trying to do in 'equalisation' is to apply a high enough potential to ensure that all the cells get a full charge. Normally this means around 14.4 volts to be safe. Ordinary 'Halfords' type chargers actually provide this potential on the top of each half-cycle, so when the battery is charged the final time on charge is actually equalising the cells. So it doesn't surprise me that you have no problems provided you don't let the cells overcharge and provided you don't expect the fastest safe charging rate.

 

[Anonymous]

Re: That\'s not the best way...

[ QUOTE ]
That's not the best way to wire extra batteries. They shouldn't be isolated. For maximum efficiency, extra batteries should just be added in parallel to the domestic bank, so you end up with one big domestic bank. The bigger the bank, the longer it'll last (because individual batteries' depth of discharge will be less for a given load).

[/ QUOTE ]I totally agree with one caveat - make sure you have the means to quickly isolate a faulty battery from the bank. This could be switches or just make sure that your leads are long enough to cut out one battery and make sure that the required spanners are ALWAYS available. Oh, and don't drop a spanner between the terminals!

 

[TheoSr]

Spanner in the works?

For my batteries a 13mm spanner is all I need. So i have wrappend the complete spanner exept the working end in PVC tape. Sooner or later I'm going to let the spanner slip and the tape will then save my day. The spanner has its place near the batteries.
Keep smiling,
Theo

 

[halcyon]

Re: Sterling 3 way splitter diodes

But with a standard diode splitter your still loosing around 10% of your alternator output warming the boat. With a relay this is nill, and if a suitable size solar panel is fitted to the service battery, this can charge all the batteries on the boat.

Brian

 

[Anonymous]

Re: Spanner in the works?

[ QUOTE ]
For my batteries a 13mm spanner is all I need. So i have wrappend the complete spanner exept the working end in PVC tape. Sooner or later I'm going to let the spanner slip and the tape will then save my day. The spanner has its place near the batteries.

[/ QUOTE ]Excellent idea - I'll do that without delay, thanks for the idea.