Battery power

[KREW2]

Hi
I read on a post the other day that a twelve volt battery should display a reading of 14 volts on the ammeter. Having topped up both batteries with a trickle charge I have just put them back in, but they only show 12.6 volts on the guage, they are both 110 amp hour batteries. does this mean they are on the way out?
thankyou KW

 

[Talbot]

Your battery will only show the maximum 14.4 volts when being charged and at the last part of the charging cycle. your reading shows that the battery is abt 80% charged

I suspect that you are only using a car style battery charger, and this is why you are only getting to this state of charge. You can rally only achieve full chage by using a stepped charge system (= expensive marine charger)

 

[boatmike]

Not necessarily. If they have "rested" for a little while since you charged them and the charge was only a trickle charge as you said they may be OK. The test will be after you have run the alternator for a while. Then I would expect after a good boost that they should show about 13.5-14.5 volts assuming that they are flooded lead acid types. If they don't after you have run the engine for a couple of hours they are indeed probably getting old. Very often though they need a good boost to get rid of sediment sludge and "wake them up" trickle charging often does not do the job. Talbot's answer is also correct... Ideally you need a sterling or adverc or similar to get the max reading but 13.5 v should be achievable without.

 

[bobfrost]

I got myself one of these a couple of years ago.

http://www.tritex.com.sg/Electrical/REYA/Reya01.htm

It's kept plugged into the shore power on a permanent basis when not sailing and I've had no problems since. i.e. batteries ready to roll whenever I am.

I've got it mounted permanently in boat and plumbed into electrical system. There was some sort of boat show discount at the time and I think it was a good buy if for no other reason than avoiding the hassle factor of wires running everywhere from a car charger etc. etc.

 

[KREW2]

Many thanks I have a sterling charger on the boat, its on hard standing at the moment so I will put it on for a day and see how we go. I didn't realise a car charger was not up to the job. will the sterling charger do both batteries at once or will it be governed by the battery switch, also what reading should I expect to see on the ammeter whilst they are charging?
many thanks again
KW

 

[KREW2]

Thanks for the replies
I have a sterling charger on the boat so I will put it on for a day.Will it charge both batteries together or does it have to be controlled by the battery switch? also what reading should the ammeter show when charging? as you may gather my knowledge of things electrical is limited
many thanks again KW

 

[KREW2]

HI thanks for your tip
Unfortunatley I am not going to be on a marina this year, I am going onto a swing mooring, at least I wont have to wait 2 hours for the town bridge to open but shore power will be missed
regards KW

 

[silverseal]

Get a small solar panel. I have a 15 watt jobbie, and it has got the engine starter battery at 12.8 volts (110amp) and the two 110 domestics are at 12.4 volts - quite enough to power lights, radio and beer cooler.
None of my batteries have seen a land based charger since early 2003

 

[Talbot]

Sterling charger may be set up to do both battery banks or just one at a time, so you will need to check how it is wired. The voltage will depend upon which step in the charge cycle, but the specs for the charger should be available on their web site.

 

[William_H]

Some people seem to be completely baffled by the advertising blurb regarding smart chargers. Apart from the comment about hard charging stiring up the sediment which may be usefull a crude trickle charger should given time provide a complete charge. It is all about the compromise between fast charging which must be throttled back after the battery is nearly full to avoid overcharge boiling and damage versus a small charge which can be left on long term which will not do damage and in the process will fully charge the battery. A smart charger will try to do both by charging hard then finishing off with a small charge to get the complete fill. That is certainly usefull at times
Simple voltage regulated chargers as in engine generator or regulated charger will reduce the charge current as the voltage of the battery rises (the current being a function of the difference between the charging inherent voltage and the battery inherent voltage) so that there is usually some capacity not filled although again long term low charge rate will get more in.
The crudest of chargers where the AC is rectified but not smoothed has a unique charge pattern where the charge voltage is high for a small fraction of the AC cycle and therefore time. The bulk of the cycle only giving a lower voltage and hence current into a battery when the battery voltage is low. The effect is that it gives a high current when the battery is low reducing in current as the battery charges but not going to near zero current (as steady DC does) but continueing to push some current in on cycle peaks.
This current of course must be controlled or monitored to avoid large currents intio a full battery causing damage.
In answer to the poster's question provided the trickle charger has had long enough to do it's job the batteries may be fully charged. I think 12.6 volts is fine for a voltage reading under the circumstances. The real goodness of the batteries can only be determined by max discharge current as in engine starting and in testing the capability to provide power for a long period to his services. In other words if it does the job you need it to do then it is fine. He has a dual battery system to provide redundancy and he can and should often compare the performance of one battery against the other in service. KW don't worry about the voltage reading when checked no load after charging. You might find it more valuable to check the vokltage with all the lights turned on and again when the engine is crancking. just to be contrary olewill

 

[Anonymous]

You have already received a lot of good advice but do check whether the instrument you are measuring with is reasonably accurate (borrow a couple of friends' DMMs and check?). Also, might you have measured this voltage when there is a load - even a small load will affect it? Car-type radios and quite a lot of gear often ends up connected 24/7 on a lot of boats, even when the isolator is off.

12.6 volts across batteries that have been off charge for a while doesn't sound like a problem. Unless you are about to embark on a long passage away from civilization, I would be inclined to try them and see how you get on. You can always change them later.

 

[KREW2]

Thanks for all the advice I have learnt a lot about batteries and feel more confident about the condition of them. Lemain I hope your mast climbing went successfully it's the next job I have to do, (well not exactly I)

 

[Anonymous]

Thankfully I went away for a day and had a brainwave so I didn't need to get up the mast after all - the main had jammed into the mast and I couldn't get it fully out. I realised that I had had the boom too high - even a few degrees prevents it from coming out freely. However, it has served to warn me that my bosun's chair is not suitable and I need to address the issue. My chandlery is selling two types of BCs - both £60 - which seems high. We are going over to France in a few days, I hope, so I will have a look since I am going to buy the flares over there anyway.