Batteries for Bespoke Navigation Solutions

[AMCD300]

This may have been covered before in other threads, however why, when so many people are now using iPads as supplementary or main navigation devices, are we not looking at fitting another rechargeable battery exclusively for their use?

I am sure there will be an implication to alternators/solar cells/wind turbines etc, making sure they are big enough to charge three batteries (engine start, domestic power and a separate iPad) but it makes sense to me that we could overcome many of the concerns wrt keeping iPads charged during normal 'quiet' sailing times with a stand-alone closed cell marine battery. Could you get away with a small solar cell to only charge the third battery while in use, relying on traditional power preservation and charging regimes to maintain the other two?

I haven't done any research regarding how long a common marine battery would last if only connected to the 5v charging socket on an iPad/mobile phone etc, however what do people think about the idea of augmenting our current batteries with a third purely for mobile devices?

Andy

 

[Mistroma]

I'm guessing that the low power drain is the reason that nobody bothers to add a dedicated iPad battery.

iPads have a 42.5W internal battery claimed to last ~10 hours and that's 4.25W or approx. 0.336 A drain from 12.5V battery. There will be small losses converting from 12.5V & to maintain the iPad battery, but nothing too significant.

A 110Ah battery would power an iPad for around a week (168 hours) to use 50% of capacity. Even dropping the domestic battery from 80%-50% would still give 100 hours use. Actual figures would probably be very much greater as battery capacity will be higher with low current drain.

The figures are all very approx. but I imagine that a flooded battery would need as much charging to make up for self-discharge as the iPad uses. Other battery types have much lower self-discharge rates but still doesn't sound like a great idea.

The same goes for other small handheld devices as they are designed to use very little power. Much better to add the power drain to the normal domestic battery.

 

[pvb]

Much better to add the power drain to the normal domestic battery.

Agreed. A dedicated iPad battery makes little sense. If the OP wants to add a battery, it would be better used as part of his domestic bank.

 

[Vara]

Agree with mistroma, as the leccy useage is so low, hardly worth adding an extra dedicated battery for it.
12v charging socket at the charttable is enough.

The ten hours battery life is enough for three days navigating with sensible use of auto sleep and by disabling all apps except the Nav one.

It does take 8 hrs to recharge from socket though. 10%~100%.

 

[Buck Turgidson]

I have a voltaic fuse solar panel with its own 16000 mAh battery. Only ever charge the ipad from that at home or out and about. Bit pricey and I didn't get it for sailing but rather trekking. I'll be testing it in the "marine environment" later this year on a 2 week sail. It looks like this and is easily attached to just about anything.

 

[AMCD300]

Thanks everyone for their answers - clearly having a good bank of domestic batteries is more use than a spare car battery in the bilge... I do wonder however, having seen the figures above, why one skipper I have sailed with had a problem with me plugging my iPhone into the 12v socket while we were underway? Each to their own, I suppose.

 

[AMCD300]

I have a voltaic fuse solar panel with its own 16000 mAh battery. Only ever charge the ipad from that at home or out and about. Bit pricey and I didn't get it for sailing but rather trekking. I'll be testing it in the "marine environment" later this year on a 2 week sail. It looks like this and is easily attached to just about anything.

Buck,

That looks like a serious piece of kit...but that was what I was talking about - a small, portable solar panel. Let us know how it works on board.

Andy

 

[pvb]

Bit pricey .....

$339

 

[AMCD300]

$339

Ouch........cheaper to take a new car battery

 

[Buck Turgidson]

Ouch........cheaper to take a new car battery

But eventually it will be flat and I can't carry one for very long. This is very light, clips onto my backpack and charges all day long, I then connect the ipad when I go to sleep and in the morning both me and the ipad are fully charged ;-) The battery will fully charge my ipad twice and it takes a day to fully charge the battery. It also charges my phone and camera and would charge my laptop but I don't take that wandering...

 

[AMCD300]

But eventually it will be flat and I can't carry one for very long. This is very light, clips onto my backpack and charges all day long, I then connect the ipad when I go to sleep and in the morning both me and the ipad are fully charged ;-) The battery will fully charge my ipad twice and it takes a day to fully charge the battery. It also charges my phone and camera and would charge my laptop but I don't take that wandering...

Nothing but common sense here. Move along..................

 

[William_H]

I'm guessing that the low power drain is the reason that nobody bothers to add a dedicated iPad battery.

iPads have a 42.5W internal battery claimed to last ~10 hours and that's 4.25W or approx. 0.336 A drain from 12.5V battery. There will be small losses converting from 12.5V & to maintain the iPad battery, but nothing too significant.

A 110Ah battery would power an iPad for around a week (168 hours) to use 50% of capacity. Even dropping the domestic battery from 80%-50% would still give 100 hours use. Actual figures would probably be very much greater as battery capacity will be higher with low current drain.

The figures are all very approx. but I imagine that a flooded battery would need as much charging to make up for self-discharge as the iPad uses. Other battery types have much lower self-discharge rates but still doesn't sound like a great idea.

The same goes for other small handheld devices as they are designed to use very little power. Much better to add the power drain to the normal domestic battery.

Ooooh see thread on inverters. I think you have omitted hours when you describe the battery as "42.5 watt. This would relate for a 5v battery as about 8 amp hours or for a 12v battery as 3.5 Amp hours. Quite reasonable for Lithium rechargeable batteries.
As already said for the oP question no need for a separate battery for recharging ipad etc. The only reason we have 2 batteries on a boat is to allow for isolation of engine start battery so we can't get stuck. If we do happen to flatten the domestic battery with an Ipad charge it is simple simply to start engine and recharge. If you have an outboard engine with pull start, a diesel with hand crank or no engine then one battery for everything is fine. good luck olewill

 

[Mistroma]

Ooooh see thread on inverters. I think you have omitted hours when you describe the battery as "42.5 watt. This would relate for a 5v battery as about 8 amp hours or for a 12v battery as 3.5 Amp hours. Quite reasonable for Lithium rechargeable batteries.
As already said for the oP question no need for a separate battery for recharging ipad etc. The only reason we have 2 batteries on a boat is to allow for isolation of engine start battery so we can't get stuck. If we do happen to flatten the domestic battery with an Ipad charge it is simple simply to start engine and recharge. If you have an outboard engine with pull start, a diesel with hand crank or no engine then one battery for everything is fine. good luck olewill

Yes, I was in a hurry and missed out the hour, but SWMBO was calling that lunch was overdue (so drop everything & run) . Well aware of diff. between energy and power so no need to get into any argument about that. I pretty much knew the answer to the OPs question and just quickly googled iPad specs. to get some figures. I didn't even bother to mention that iPad was 5V as it didn't really matter in grand scheme (working back to Amps.).

Conclusion still stands though: 42.5Wh spread over 10 hours is 4.25Wh. Plugging charger in to a 12.5V battery would therefore take around 0.36A (4.25/12.5) to just run the iPad continuously and keep its battery at original 100% level.

Anyway, I see that everyone is in agreement that it would be a waste to add a dedicated iPad battery.