Charging

[Dr Bradley]

When I bought a Smartgauge, I could at last get some idea about the state of my battery bank, 5 x 110ah wet cell.The news wasn't good in that I must repeatedly taken them well below 50% and never charged fully, for the four months since I got the boat. With the knowledge gleaned from the Smartgauge I have (mostly) kept them above 50%. My only charging is from a 160amp engine alternator. It appears, again from Smartgauge, to be charging at around 13.8 volts. After 2 days cruising (about 6 hours per day) and very little consumption, the % I acheived was 94. Never previously got much above 80%.

 

Surely this is not enough. Is there any way to increase the voltage of the alternator?

 

Next is the rate of discharge. The main use of power is the computer, then a few halogen or LED lights. Sometimes I can be on the computer for hours (through an inverter) and the decline is only a few %. At other times 20 minutes can cause a reduction of 20%. I have even left the boat with all electrics switched off only to find a 15-20% reduction a few hours later.

 

Any ideas how this can happen?

 

 

Bemused of Sowerby. (think I'll change my boat name to that!)

 

 

PS Just checked, 20 minutes of the computer on has reduced the %charge of the batteries by 9%. Can this be true for a bog standard lap top?

[steelaway]

When I bought a Smartgauge, I could at last get some idea about the state of my battery bank, 5 x 110ah wet cell.The news wasn't good in that I must repeatedly taken them well below 50% and never charged fully, for the four months since I got the boat. With the knowledge gleaned from the Smartgauge I have (mostly) kept them above 50%. My only charging is from a 160amp engine alternator. It appears, again from Smartgauge, to be charging at around 13.8 volts. After 2 days cruising (about 6 hours per day) and very little consumption, the % I acheived was 94. Never previously got much above 80%.

 

Surely this is not enough. Is there any way to increase the voltage of the alternator?

 

Next is the rate of discharge. The main use of power is the computer, then a few halogen or LED lights. Sometimes I can be on the computer for hours (through an inverter) and the decline is only a few %. At other times 20 minutes can cause a reduction of 20%. I have even left the boat with all electrics switched off only to find a 15-20% reduction a few hours later.

 

Any ideas how this can happen?

 

 

Bemused of Sowerby. (think I'll change my boat name to that!)

 

 

PS Just checked, 20 minutes of the computer on has reduced the %charge of the batteries by 9%. Can this be true for a bog standard lap top?

 

 

Hi

 

After all your findings - I would definetly suspect a duff battery or battery's

 

Alex

[Keeping Up]

Surely this is not enough. Is there any way to increase the voltage of the alternator?

Gibbo produced this excellent little article on exactly that subject

[Billypownall]

When I bought a Smartgauge, I could at last get some idea about the state of my battery bank, 5 x 110ah wet cell.The news wasn't good in that I must repeatedly taken them well below 50% and never charged fully, for the four months since I got the boat. With the knowledge gleaned from the Smartgauge I have (mostly) kept them above 50%. My only charging is from a 160amp engine alternator. It appears, again from Smartgauge, to be charging at around 13.8 volts. After 2 days cruising (about 6 hours per day) and very little consumption, the % I acheived was 94. Never previously got much above 80%.

 

Surely this is not enough. Is there any way to increase the voltage of the alternator?

 

Next is the rate of discharge. The main use of power is the computer, then a few halogen or LED lights. Sometimes I can be on the computer for hours (through an inverter) and the decline is only a few %. At other times 20 minutes can cause a reduction of 20%. I have even left the boat with all electrics switched off only to find a 15-20% reduction a few hours later.

 

Any ideas how this can happen?

 

 

Bemused of Sowerby. (think I'll change my boat name to that!)

 

 

PS Just checked, 20 minutes of the computer on has reduced the %charge of the batteries by 9%. Can this be true for a bog standard lap top?

I have just fitted a smartgauge and hope it proves OK. One wonders from what you have said whether yours is working correctly. Assuming that it is I fear these must me something amiss with your batteries. In any case 13.8 volts is not enough to charge them. I had similar problems with our new boat last year. This was cured by doubling the size of the cable from the alternator to the batteries from 25mm to 50mm. We were losing .4 of a volt along the way.

[PeterF]

With a charging voltage of 13.8V it would be worth your while considering an external regulator to increase the charging voltage. Read through the Smartgauge website and that clearly states there will be a good increase in charging rate if the voltage is increased. Also, is the alternator geared highly enough to actually deliver the full 160Apm, that may be worth checking from pulley diameters. If the engine pulley is twice the alternator pulley then you will probably not get full output. If it is 3 times you probably will.

 

I have a 150Amp alternator which is geared 3:1 and the voltage is typically 14.3 to 14.5V charging into 4 x 120Amp wet cells. I do not have an external regulator because the internal one runs at this higher voltage already and charges very well. I can get the batteries well charged in 4 hours running with charge current down to <20Amps.

[sueb]

Hitch your laptop to a maplins gizmo that connects to 12v. I don't know what the Maplins thingy is called but it converts 12v to 19v which is a lot better than converting 240v. Cost is in the region of £20

Sue

[alan_fincher]

Hitch your laptop to a maplins gizmo that connects to 12v. I don't know what the Maplins thingy is called but it converts 12v to 19v which is a lot better than converting 240v. Cost is in the region of £20

Sue

With the proviso that this has worked fine for 3 laptops previously used on board, but not my latest one, (Dell Studio). Unfortunately this announces that it is not connected to a proper Dell power supply, and will only run off what it has detected at reduced efficiency, without actually recharging the batteries.

 

It seems I'm forced to an inverter with this one, which is most frustrating!

[Dr Bradley]

I think Gibbos diode solution is probably beyond me. It is also talking about older alternators - mine is new. I am certainly thinking about a sterling alternator to battery charger. I believe this has a further advantage in that I can also feed in output from the second 70amp alternator.

 

The thought that my batteries may be duff certainly occurs. Though they are only 6 months old I have inadvertantly abused them - put that down to the learning curve and just one of the costs of fitting out a sailaway whilst living onboard.

 

Cables are 50mm and connected up in a manner Gibbo advocated on an earlier thread.

 

I have not checked the gearing of pulleys, would changing this be cheaper/easier/better than an external regulator?

 

I fully intend to go the Maplin route to run the computer from the 12 volt system, but haven't got round to it yet.

[chris w]

I have not checked the gearing of pulleys, would changing this be cheaper/easier/better than an external regulator?

These are two different issues.

 

The higher the charge voltage the better (up to 14.8v for wet lead acid batteries). Once the battery charges so that its terminal voltage reaches the applied voltage (say 14.8v), then you will get more current driven into the batteries at any particular engine revs (up to the maximum output from the alternator in amps) than you would at a lower voltage. The difference is striking. An increase from just 13.8v to say 14.2v (ie: 0.4v) will increase the charge current by as much as 30-40A (assuming the alternator is able to deliver the extra current). When I switch my alternator controller from off to on, the charge current from my alternator (nominally 80A on a 2:1 ratio) increases from 27A (off) to 55A (on). This is a voltage increase from 14.3v to 14.8v.

 

The higher the pulley ratio, the more current you will get out of the alternator at any particular engine revs. A 3:1 ratio or more will tend to give you the alternator's label-rated output, say 150A for a 150A rated alternator. A more typical 2:1 ratio will only give you about 70% or so of the rated output. Your "150A" alternator will only give you about 100A over a NB rev range.

 

Chris

Edited April 10, 2009 by chris w

[Justme]

Also ditch the halogens & use more LED's or low energy types. Your laptop should only be using about 3-5 amps at 12v nominal even if its charging a totaly flat battery & running the laptop. Have you changed the power settings on the laptop to give a longer battery life (at reduced slightly performance)?

 

Justme