Leisure battery connecting

[Tony Brooks]

1 hour ago, Peter Sloe roamin said:

As to the value of the calculations in the article, they make sense to me as someone who did a three year electronic engineering apprenticeship (a very long time ago but I believe the electrons still move the same way) and with a 100amp load the imbalance is startling. Of course most of us aren't pulling 100a most of the time but I di when I'm microwaving a ready meal and that's enough to make want to balance the load better. Thanks again for helping my thought process.

 

 

 

And if you are sensible you will only run a high current device when the engine is running so much of the load will be coming from the alternator(s) and probably comparitively little from the batteries so the interlinks are no or a minor part of the current path.

 

[Peter Sloe roamin]

On 25/08/2019 at 19:40, Tony Brooks said:

 

And if you are sensible you will only run a high current device when the engine is running so much of the load will be coming from the alternator(s) and probably comparitively little from the batteries so the interlinks are no or a minor part of the current path.

 

An update to my original question - and thanks to everyone for their input - after several instances when an apparent good state of charge dwindled away rapidly I put a voltmeter across each of the four batteries in turn and found batteries 1, 2 and 4 at 12.2v and no3 at 12.5v. That convinced me to make some changes so a few days ago the 4 x 115ah batteries were swapped for 4 x 130ah AGMs, the starter battery was moved to the end of the row, and the wiring was replaced so all loads are across the whole bank and the inter battery links are all the same length. Of course new batteries are always better than old ones but the extra capacity feels great.

[ditchcrawler]

25 minutes ago, Peter Sloe roamin said:

An update to my original question - and thanks to everyone for their input - after several instances when an apparent good state of charge dwindled away rapidly I put a voltmeter across each of the four batteries in turn and found batteries 1, 2 and 4 at 12.2v and no3 at 12.5v. That convinced me to make some changes so a few days ago the 4 x 115ah batteries were swapped for 4 x 130ah AGMs, the starter battery was moved to the end of the row, and the wiring was replaced so all loads are across the whole bank and the inter battery links are all the same length. Of course new batteries are always better than old ones but the extra capacity feels great.

And are you fully recharging them?

[WotEver]

15 minutes ago, ditchcrawler said:

And are you fully recharging them?

An excellent question. If ‘yes’ then how are you determining this?

[MtB]

2 hours ago, Peter Sloe roamin said:

after several instances when an apparent good state of charge dwindled away rapidly

 

As already landed upon, "apparent good state of charge", in what way "apparent"?

 

 

2 hours ago, Peter Sloe roamin said:

I put a voltmeter across each of the four batteries in turn and found batteries 1, 2 and 4 at 12.2v and no3 at 12.5v. That convinced me to make some changes so a few days ago the 4 x 115ah batteries were swapped for 4 x 130ah AGMs

 

I can't help but wonder why you concluded this was a good course of action. Those voltages just indicate three heavily discharged batteries and one moderately discharged. I'd have been looking at what was wrong with my charging system, before replacing them.

 

 

 

[Tony Brooks]

I suspect they are badly sulphated, that's all too often the answer to this type of thing and so back to insufficient charging and probably no day to day monitoring.

[Peter Sloe roamin]

3 hours ago, Tony Brooks said:

I suspect they are badly sulphated, that's all too often the answer to this type of thing and so back to insufficient charging and probably no day to day monitoring.

Well, a whole list of questions so -

 

1. I measured across each battery when it had no load - because I disconnected cables on one post - so I could see if there was an imbalance, and there was. I am a liveaboard so there is a continuous cycle of use and recharge, either from the 512w solar or from the engine alternator (100a).

 

2. I said 'apparent' good state of charge because I could only use the voltage indicated on an MT50 monitor unit. With no charging going on from the alternator or the solar I wold expect 12.6 - 12.7v to indicate a good state of charge and I used to see it quite often but in the last 3 months it became rarer.

 

3. Since I bought the boat two years ago I have tried to keep the non-charging voltage above 12.1v at all times, but over the last 3 months this was very difficult, in the morning it would be down to 11.8 or even 11.6v. In the winter of 2017-2018 the boat was left moored at a broker until I picked it up in mid-March and I suspect there was little or no charging of the batteries in that time which won't have helped their longevity, the old ones were at least 4 years old, perhaps older.

 

I had an electrician look over the system last year and the charger was OK then. He had me run the engine at 1100rpm for 3 hours and at the end the MT50 was showing 14.6v. I tried the same thing recently and only got to 14.3v. Because of the rewiring I got a professional in again to swap the batteries, test the starter battery, and check the system was working right for the AGM batteries and he gave it the thumbs up.

 

So far I don't use shore power at all but I'm aware I don't have built-in battery charging if the boat is plugged in to a shore unit so I am considering swapping out the 17 year old Sterling 3000w inverter for a combi inverter/charger with lower output, say 2000va, and add a proper monitoring unit like one of the Victron BMV range to give me a better idea of what is going on.

[WotEver]

A few points spring to mind...

 

6 minutes ago, Peter Sloe roamin said:

the old ones were at least 4 years old, perhaps older.

They’ve done well and even if well cared for would be approaching end of life. 
 

 

7 minutes ago, Peter Sloe roamin said:

at the end the MT50 was showing 14.6v.

At what current? Both voltage and current are required to determine charge status. 
 

8 minutes ago, Peter Sloe roamin said:

I am considering swapping out the 17 year old Sterling 3000w inverter for a combi inverter/charger with lower output

Pay less by only buying a charger and you also give yourself some redundancy. 
 

9 minutes ago, Peter Sloe roamin said:

add a proper monitoring unit like one of the Victron BMV range to give me a better idea of what is going on.

That would be a good move. 

[Tony Brooks]

59 minutes ago, Peter Sloe roamin said:

 and add a proper monitoring unit like one of the Victron BMV range to give me a better idea of what is going on.

 

A very good idea as long as you use current @14.4V plus to establish when to stop charging and rested voltage to establish when its vital to start charging ASAP but accepting every day is best. Simply ignore any % charge or such like scales.

 

In my view 12.1 rested voltage is too low to indicate time to charge. I would prefer 12.3.

 

 

[Detling]

A battery bank will easily reach 14.6 volts, and still be taking 20+ amps of charge, so maybe at 90% SoC.

If you stop charging then and do it repeatedly you are being very cruel to your batteries.  Get that ammeter sooner rather than later, before your new batteries get the sulks.  The Solar will help soon,  a quick blast with the alternator early morning, and the sun will finish the job over the rest of the day.