Small battery and suitable solar charger

[Refueler]

All good points, but for what OP and Will (above) are after, lower amp output of higher capacity 18650 cells need not be an issue. Samsung currently up to 3500 mAh but at 8a max discharge rate - versus 20a rate of a 2500 mAh cell.

Samsung 35E 18650 3500mAh 8A Battery

Fine .. evolution is ongoing ... my post was purely as comment based on Will's already stated.

With short duration and low demand on output - they are an excellent solution ... easy to hide away in a hole behind the radio etc ... easy to charge up once correct charger obtained ... and not expensive.

A depth sounder is in mA 's .... a VHF radio on full 25W is only incl losses less than 2.5A .....

BUT note that 18650 / 21xx cells are available in 3.3v and 3.6v nominal values ............ the 3.6v being the better for here .. giving a full charge value of 4.2v ..

 

[lustyd]

Something I've been thinking about but not done much investigation into, is to use a vehicle Lithium starter pack battery instead of a large lead acid. I have a Jeanneau Sun 2000 that has very limited power requirement, just Tacktick instruments like you. I have a power pack in the garage for general use on cars and motor bike. Cost me about 100 euros if I remember correctly. Small, lightweight, can be taken home easily for charging or charged in the car, but as I say, I've not done any power calculations yet. Might be worth considering.

More important would be chemistry, make sure it’s LiFePo4 for safety.
If you also have a radio (both VHF and car type radio) that may use a decent amount of power over a weekend

 

[PaulRainbow]

Hi I have a Beneteau 21 with depth sounder provided via my Tacktick. This is the only draw on a battery on board I am looking for a small light weigh battery and a solar charger to leave on board. This will replace my current 50ah leisure battery that weights a ton, well 20 kgs
Suggestions please

Small battery £16.20 Yuasa NP7-12 Industrial VRLA Battery

Small solar panel less than a tenner on Ebay.

Simple, cheap, no carting batteries back and forth etc.

 

[Colin Brown]

EcoWorthy do a good range of LiFePO batteries. Much lighter in weight than lead acid. ECO-WORTHY: Solar Panel Kits & Lithium Battery &DIY Solar Power System

While this is no doubt the Rolls Royce system, has anyone had experience with much lower outputs, say a 4ah battery and a reasonably priced charger
Thank you for the Eco - worthy equipment but it seemed geared up for much larger insulations

 

[Muddy32]

Slight drift.
Log/depth on, so little drain on a 105 Ahr Battery on a 10-12 hr crossing to Channel Isles.
But what about the use of a ST 1000 Autohelm.
Will I need to run the engine at some point?

 

[Refueler]

Slight drift.
Log/depth on, so little drain on a 105 Ahr Battery on a 10-12 hr crossing to Channel Isles.
But what about the use of a ST 1000 Autohelm.
Will I need to run the engine at some point?

I've usually assumed a rate of 1A average over the use ... as it will cycle the draw depending on how well you trim the boat ... how often it has to correct / apply helm etc.

I have read figures of similar Tillerpilots demanding from near zero at idle up to 40W in heavy use ... with 10 - 15W as average.

Taking the 12v supply ... that means anywhere from idle few mA's up to ~4A if pressed.

Safety margin of 50% - that means your 100AH battery is good for about 2 days at average 1A .... but if pressed - 1/2 day at 4A

Shoot me if wrong !

Edit : My AH2000 did give a good days sailing before the two 90 A/hr batts threw their hands in ... now I get about 4hrs - but the batts are ****** !! I never had to consider longer than that really - because a) boat has a solar panel of about 50W on foredeck. b) engine would be on for tricky navigation spots ....
Given that - I would be happy enough just to replace the two 90 A/hr batts ... which power instruments / tillerpilot .. nav lights etc. Would be nice to have more capacity - but battery boxes are max'd to those 90's and I am not going to Lithium yet ..