Batteries and battery chargers

[Squeaky]

Good evening:

I live aboard in a marina and leave the battery charger on all the time or have in the past.

Our power went off this morning early and we have been without power all day. I turned off the fridge and all unnecessary switches this morning and noticed that the battery was showing around 12.4 volts and while using only the inverter to power my laptop watched it rather quickly go down to 11.9 volts.

I started the motor and ran it until the charge went up to 13.3 volts when I turned off the engine and the meter dropped to 12.7 volts in a few minutes. I have continued to use the laptop for past couple of hours and the reading is still 12.6 volts.

The voltage does not seem to be dropping at any where near as quickly as it did this morning.

The thought has just crossed my mind that maybe I should not leave the charger on at all times - have heard about "battery memory" when you consistently under charge batteries. Is it possible that I should be fully charging and discharging the battery instead of leaving it at full charge all the time?

Cheers

Squeaky

 

[sailorman]

wet cell batteries do not have a memory

 

[Squeaky]

Good evening:

Okay, that may not be a reason for not leaving the charger on all the time but is there any reason one way or another for doing or not doing so?

Cheers

Squeaky

 

[Stu Jackson]

How old are the batteries?

Generally, when the voltage drops with a significant load on, like your fridge, it indicates batteries nearing the end of their useful life, or they need to be equalized. Leaving them charging all the time introduces sulfation.

 

[Squeaky]

Good evening:

Batteries new in Jan 2010 - two 105 Amp Hour.

equalized. - meaning what????

Leaving them charging all the time introduces sulfation - is this good or bad?

What do others do in this situation - leave charger on all the time or on/off?

Cheers

Squeaky

 

[sailorman]

Good evening:

Batteries new in Jan 2010 - two 105 Amp Hour.

equalized. - meaning what????

Leaving them charging all the time introduces sulfation - is this good or bad?

What do others do in this situation - leave charger on all the time or on/off?

Cheers

Squeaky

goto the sterling site all info there

http://www.sterling-power.com/downloads.htm

 

[PORL]

Batteries

I would suggest to discharge then fully charge each time, this will prolong the life of the battery

 

[Squeaky]

Good evening:

I normally consider myself fairly good at finding needles in hay stacks but didn't manage to find the answer to my questions on the Sterling site. There is lots of information concerning their various products but ....

Cheers

Squeaky

 

[sailorman]

Good evening:

I normally consider myself fairly good at finding needles in hay stacks but didn't manage to find the answer to my questions on the Sterling site. There is lots of information concerning their various products but ....

Cheers

Squeaky

Bedtime reading

 

[NormanS]

Good evening:

I live aboard in a marina and leave the battery charger on all the time or have in the past.

Our power went off this morning early and we have been without power all day. I turned off the fridge and all unnecessary switches this morning and noticed that the battery was showing around 12.4 volts and while using only the inverter to power my laptop watched it rather quickly go down to 11.9 volts.

I started the motor and ran it until the charge went up to 13.3 volts when I turned off the engine and the meter dropped to 12.7 volts in a few minutes. I have continued to use the laptop for past couple of hours and the reading is still 12.6 volts.

The voltage does not seem to be dropping at any where near as quickly as it did this morning.

The thought has just crossed my mind that maybe I should not leave the charger on at all times - have heard about "battery memory" when you consistently under charge batteries. Is it possible that I should be fully charging and discharging the battery instead of leaving it at full charge all the time?

Cheers

Squeaky

I'm no expert, but you seem to have been abandoned, so here's my 2ds or 2ps worth.

Provided that your mains battery charger is of the modern multi-stage type, it's fine to leave it on all the time. What happens is that it is normally on "Float" which means that it is merely replacing the power that you are using from the battery. Every so often, possibly 24 hours, (?), the charger goes to a higher voltage, and gives the batteries a boost. this reduces any Sulfasion. Sulfasion is bad.

If your battery charger is the more basic garage type, it should not be left on all the time.

You have just been given the sum total of my battery charging knowledge.

 

[VicS]

Good evening:

I normally consider myself fairly good at finding needles in hay stacks but didn't manage to find the answer to my questions on the Sterling site. There is lots of information concerning their various products but ....

Cheers

Squeaky

maybe Sailorman was thinking about the FAQs http://www.sterling-power.com/support-faq.htm

As above though if you are leaving a charger on 24/7 it should be the multistage automatic type. One of those will charge at optimum rate at reduce to a float or maintenance charging mode once charging is complete. More powerful chargers will also have temperature sensors which will allow faster charging than those without.

For a liveaboard a charger also designed to deliver power for onboard systems as well as for battery recharging would be a sensible choice.

 

[Playtime]

This link has just been posted on Scuttlebutt. If you've got the time to read it, there's lots of good stuff about DC systems and batteries.

It might even answer your question.

 

[sailinglegend420]

This link is of no use to the OP who probably needs more basic help. Also Mr Sterling's link has been critised by many on these forums. He is totally wrong about his general critiscm of Gel and especially AGM batteries. He should know better, so should those who suggest him!

Squeaky said he ran his engine until the voltage got up to 13.3v and then fell back to 12.7v. With a multi stage charger the voltage should get up to 14.4 or 14.8 and then fall back to a float level of 13.2 volts. This should mean the batteries are fully charged, but this can take many hours of engine running.

His computer probably takes more amps than the fridge so he shouldn't be surprised that the volts went down, especiall since running the engine could not have fully charged the batteries.

Some battery basics:

Use a multi stage charger.

Try and fully charge the batteries at least once a month on shore power.

Never discharge below 50% of maximum capacity. Find a way to measure this accurately - a digital voltmeter or Battery monitor is a must have. Check with your battery manufacturer what the voltage is for 50% discharged, and remember this is the "open circuit" voltage with no load. This is usually 12.2 volts which is only 0.6 volts below the fully charged open circuit voltage. This is why a digital voltmeter is best. No load is often difficult to achieve as there is always something drawing current, and this open circuit voltage must be when the battery has been allowed to "rest" for an hour or maybe more depending on the battery type. You could trying letting the batteries volts go down to 12.0 volts and then disconnect just one battery buy lifting the EARTH lug, and leave it and see what open circuit voltage this comes back to - it should come back to about 12.2volts. If you have easy access then over a few days do the same on all batteries to make sure all are working the same. Often one will pull down all the others. You can then decide that at a current draw of say 4 amps I can let my batteries go down to 12.0 volts when I must then recharge.

Never mix battery types, i.e. Wet and Sealed.

Always replace all the batteries at the same time otherwise old ones will drag down the good new ones.

 

[Squeaky]

Good morning:

Thanks for all the replies - I think I have my answer and guess I was not doing anything wrong as my charger is the multi-stage type.

Surprised to discover how much power the computer takes.

Cheers

Squeaky

 

[Playtime]

This link is of no use to the OP who probably needs more basic help.

I thought the first part of the article in the link was directly relevant (Depth of Discharge).

However, I agree that some of the material was maybe a bit advanced. I'll admit, I didn't read it all.

 

[macd]

Surprised to discover how much power the computer takes.

I've seen a modern laptop, whilst both running and re-charging, drawing 8 amps. My fridge never draws more than 3. Whenever my batteries run down appreciably, it's invariably due to prolonged computer use. Older laptops (I have a 12 year old Toughbook dedicated to nav) are much less power-hungry.

As to the advice of always replacing an entire bank of batteries as a unit, there have been several posts from knowledegeable people who've replaced one of a bank with no ill-effects. If I remember correctly, this was always when the failed battery was only of moderate age, say no more than two years or so. On this basis the "always replace all" dictum seems to be sound general advice but not absolute.

 

[sailinglegend420]

...........there have been several posts from knowledegeable people who've replaced one of a bank with no ill-effects........

There are lots of "experts" in this field but when the likes of Mr Stirling and Mr Nigel Calder have exactly opposite views on subjects like AGMs then that can only confuse everyone.

Replacing only one battery "with no ill effects" is quite possible - partly because you may never see the "ill effects". What is likely to happen is that the old batteries will slowly drag down the capacity of the new ones, so shortening their life.

Consider the worst case scenario where the old batteries have lost a lot of their capacity. Fully charge all batteries and then draw say 10 amps for an hour, then check the open circuit voltage of both old and new batteries. The old ones may be a lot lower than the new ones. When you reconnect all batteries the old will significanlty drag down the battery bank voltage. This is the time to throw out the old ones.

If you always just replace one at a time you will always be playing this game. If you throw out the old and just run on the new till they fail, then you can replace them all at the same time.

 

[Monique]

This link has just been posted on Scuttlebutt. If you've got the time to read it, there's lots of good stuff about DC systems and batteries.

It might even answer your question.

Glad my posted link is helping someone already...

Isn't it what this forum is all about???

Woo hoo my 500th post. A helpful one at that...