Sterling power management

[Kassia]

Hi, we have just bought a boat with a Sterling power management system. I read somewhere a while back that you should not allow your batteries to drain past a certain point. If that's right I wondered if any one knows what point that is? We charge our batteries by the engine and have been using the engine a lot while cruising but I want to make sure we charge them enough when moored anywhere. Also probably a really stupid question but am I right in thinking Ah stands for amp hours, so if it says 114Ah does that mean we have 114 hours?! The batteries are all a bit of a mystery to me but I want to make sure we look after them. . .

[BEngo]

Hi, we have just bought a boat with a Sterling power management system. I read somewhere a while back that you should not allow your batteries to drain past a certain point. If that's right I wondered if any one knows what point that is? We charge our batteries by the engine and have been using the engine a lot while cruising but I want to make sure we charge them enough when moored anywhere. Also probably a really stupid question but am I right in thinking Ah stands for amp hours, so if it says 114Ah does that mean we have 114 hours?! The batteries are all a bit of a mystery to me but I want to make sure we look after them. . .

 

 

It's a good idea not to take the batteries below about 50% of their capacity. All discharge causes internal damage and shortens life and 50% is a reasonable compromise between usage and life.

 

It's also a good idea not to leave batteries partly discharged, if you can. This causes sulphation which reduces the useable capacity.

 

Have a good look at Gibbo's smartgauge site Smartgauge- this has some good explanations of the technical aspects, including what an Ah actually is. Ah does stand for Amp-hours, but having 114 of them only means that you could put a 1 Amp load on for at least 114 hours when the battery would be 'flat'. If you put a 20 Amp load on the battery it would last just under 5 hours till 'flat' but if you put a 40 A load on it would last well under 3 hours till 'flat'. The amps needed by a load is the Watts it uses divided by 12 (or 24 if you have a 24 Volt boat)

 

If the 114 Ah The power management system says is correct (the smartgauge site will tell you why this is not likely to be true) and the batteries are fully charged at the time then you should not use more than 57 Ah or your batteries will be below 50%. This is approximately a 5 Amp load for 12 hours or a 10 amp load for about 5 hours. If the batteries are less than full at the time then you should not take them below about 50% of their full capacity.

 

The batteries' full capacity when new is usually marked on them, but this decreases with time and usage, so it is hard to be precise about what the actual useable capacity of a battery bank is.

 

N

[bottle]

Another site with some answers: http://www.batteryfaq.org/

[ditchcrawler]

Hi, we have just bought a boat with a Sterling power management system. I read somewhere a while back that you should not allow your batteries to drain past a certain point. If that's right I wondered if any one knows what point that is? We charge our batteries by the engine and have been using the engine a lot while cruising but I want to make sure we charge them enough when moored anywhere. Also probably a really stupid question but am I right in thinking Ah stands for amp hours, so if it says 114Ah does that mean we have 114 hours?! The batteries are all a bit of a mystery to me but I want to make sure we look after them. . .

If your Sterling unit is the same as ours it is telling you that you or somebody has taken 114 Ah out of the batteries and not put it back. The problem is you have no idea if its true or when it happened. It could be that the previous owner took 90 out every day and only put 85 back. That way every day they would have added 5 to the deficit. The number should count down towards zero as the batteries charge but it will never go below zero. So if it was reading 10 Ah and you ran the engine all day the reading wouldn't pass the zero mark, even if you were putting in 5 amp per hour all day.

 

At what point did you read the 114 Ah before or after a days engine running?

[OldGoat]

Hi, we have just bought a boat with a Sterling power management system. I read somewhere a while back that you should not allow your batteries to drain past a certain point. If that's right I wondered if any one knows what point that is? We charge our batteries by the engine and have been using the engine a lot while cruising but I want to make sure we charge them enough when moored anywhere. Also probably a really stupid question but am I right in thinking Ah stands for amp hours, so if it says 114Ah does that mean we have 114 hours?! The batteries are all a bit of a mystery to me but I want to make sure we look after them. . .

 

 

114 hours is meaningless unless you know what the starting figure is. I'd guess you migh have 50 amp hours left

 

There is documentation on the Sterling site

clicky here and select the items you want, both bruchure and instruction manual

but it says pretty much what has bee said here.

 

According to Mr. Sterling it's not a lot more than an amp hour counter, which can be a bit of a chocolate teapot if you don't make adjustments:-

1. Not all the amps put into a battery will be converted into useful electricity. The efficiency is about 80% not 100% as implied by the documentation

2. You should NEVER run your batteries as low as 50% capacity. A more workable figure might / should be 70 or 60% (experts will advise)

3. As your batteries age the capacity decreases markedly - but I don't know how you allw for this loss of efficiency.

 

Bummer, innit

- a lot more complicated than first appears. I suppose if you take 40% of what the meter says, you'd be reasonably safe.

 

 

I fully accept that my suggestions will be challenged!

[Kassia]

Thank you all for this, I think like you say the amp hours is a bit missleading. We are now trying to focus more on the Volts showing rather than the Amp hours. our inverter seems to scream at us if it drops to 10V (only happened once). We will generaly run the engine a couple of hours in the eve maybe but I am also trying to do a deeper longer charge when we are around all day. Its all a bit new but thats part of the learning curve and joys of living on a boat isnt it!

[by'eck]

Thank you all for this, I think like you say the amp hours is a bit missleading. We are now trying to focus more on the Volts showing rather than the Amp hours. our inverter seems to scream at us if it drops to 10V (only happened once). We will generaly run the engine a couple of hours in the eve maybe but I am also trying to do a deeper longer charge when we are around all day. Its all a bit new but thats part of the learning curve and joys of living on a boat isnt it!

 

Amp hours shouldn't be confusing. One amp hour is the quantity of electricity used when you draw one amp of current for one hour - two amps for 30 minutes is the same quantity if that helps.

 

Amp hours abbreviated to Ah, is the measurement used to define battery capacity. A battery will therefore have an Ah rating. This will probably be only valid when new though, since their available capacity can decrease quite dramatically as they age or are misused.

 

For this reason and not fully re-charging them after use, your battery monitor readings may become useless after a while with the shunt based system you have, particularly the charge remaining and state of charge figures.

 

The voltage displayed when there is no drain or charge taking place should always give a good indication of state of charge of the batteries though (but not their possibly diminished capacity).

 

Normal lead acid leisure batteries should ideally never be discharged below half of their capacity (although less is better) before being fully re-charged. This is equivalent to between 12.1 and 12.2 volts measured after a resting period following any charge or discharge.

[smileypete]

Thank you all for this, I think like you say the amp hours is a bit missleading. We are now trying to focus more on the Volts showing rather than the Amp hours. our inverter seems to scream at us if it drops to 10V (only happened once). We will generaly run the engine a couple of hours in the eve maybe but I am also trying to do a deeper longer charge when we are around all day. Its all a bit new but thats part of the learning curve and joys of living on a boat isnt it!

Couple of tips to consider:

 

When away from shoreline try for a long charge as you say at least once a week until charge current drops to quite a low level. How low? Well if there's say 3 leisure batts of 110Ah try to wait for 6 amps or less.

 

When using charge from the batts, if little or no loads are connected the batt voltage should stabilise to 12.2V or more after 10-15 mins, otherwise it's probably a good time to recharge.

 

Also consider a Smartgauge batt monitor if often away from a shoreline and to make things a lot simpler.

 

cheers, Pete.

~smpt~