Small battery and suitable solar charger

C

Colin Brown

Member
Joined
1 Sep 2020
Messages
25
Visit site
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
 
A Car Battery trickle charger ... there are many Solar trickle charge panels and they do not need a controller. Any Halfords or similar Car Accessory shop will have something ... Panel is about 20cms square .....

Ally that to a reasonable sized SLA Alarm battery ... they can be had from about 3A/hr up to about 20A/hr .... or a small Lead Acid used on a Lawn Tractor ...
My ex Soviet Speedboat used to have a 7A/hr SLA House alarm battery - I just clipped a 10W Solar panel to it ... actual output ? probably averaged 5W ... no controller ...
After years - I then swapped the SLA for a battery I took out of one of my cars ... and that same Solar panel looks after that ..

You could of course get a LiIon battery pack and a Programmable charger for the price of that 50A/hr battery you had ! But it is not advisable to use Solar to charge such ... unless you buy a purpose designed setup.
 
Last edited:
If the depth sounder is your only on board device I’d buy the smallest 12v LiFePo battery I could find and just take it home once a year and charge it. Depth sounders use very little power. Lithium batteries have very limited ‘fade’ - much less than lead acid anyway - and really won’t require a regular top up from solar.
 
Colin Brown said:
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
Click to expand...
What is your budget?

Cheap as chips is sealed lead acid with cheap (£20) solar panel and controller.

Gel or AGM deep cycle battery bit more expensive.

I like the idea of the LiFePo battery but don’t know enough about them. Do they really last so long without charging?

I do like to have a means of charging on board.
 
My llittle 21fter runs on a pack of 18650 cells 4 lots of 3 in series. Runs radio 25w nav lights and internal light. None used much seems to last all season. Charged with a 3s charge control board. ol'will
 
Refueler said:
Oh Dear - so going into shop and buying a 100 A/hr battery is meaningless .....

Forgive me for explaining that 8 A/hr means battery can provide 8 amps for 1 hour at rated voltage ... shocking revelation !!

And anyway - my post wasn't for you - it was a comment to 'Will H' .....
Click to expand...
No that’s not what that means. Ah is amps times hours so 8Ah means 8A for one hour or 4A for two.
What you wrote means amps per hour which is utterly meaningless since Amps is an instant reading. You could measure Ah/h which would indicate how many Ah are being generated or consumer per hour. In theory A/h would be a measure of rate of change in Amps being used or generated but I can’t think of a use-case.

Either way, you’re using the wrong term and my post was helpful so that people reading the forum understand what to look for when buying and speccing a system. You can’t buy batteries rated in A/hr you have to buy Ah rated ones.

I’m aware your post wasn’t to me. Mine was to you though. It wasn’t a personal attack it was pointing out an error in your post in the hope that you learn something.
 
lustyd said:
No that’s not what that means. Ah is amps times hours so 8Ah means 8A for one hour or 4A for two.
What you wrote means amps per hour which is utterly meaningless since Amps is an instant reading. You could measure Ah/h which would indicate how many Ah are being generated or consumer per hour. In theory A/h would be a measure of rate of change in Amps being used or generated but I can’t think of a use-case.

Either way, you’re using the wrong term and my post was helpful so that people reading the forum understand what to look for when buying and speccing a system. You can’t buy batteries rated in A/hr you have to buy Ah rated ones.

I’m aware your post wasn’t to me. Mine was to you though. It wasn’t a personal attack it was pointing out an error in your post in the hope that you learn something.
Click to expand...

Ha Ha ..

So your first two lines agree - then you ramble on ...

Well done .. I'm sure everyone really understands now ...

I don't know everything - far from it - but "hope that you learn something." - I throw back at you as insulting and totally uncalled for ..

Just so others know why I posted the 8 A/hr ... or 8 Ah to please him ...

Guy quoted "My llittle 21fter runs on a pack of 18650 cells 4 lots of 3 in series" many 18650 cells - I use a lot of them as well as the 21 versions ... are of about 2000 mA/hr or slightly more capability ... therefore 4 x that gives the total capability of 8 A/hr ..... or as dear ol Lustyd has understood - 8A for one hour at the rated voltage ... (He's really making a silly point about the addition of the '/' and 'r' to the Ah ... )

Bl***y dangerous place this forum init !!
 
William_H said:
My llittle 21fter runs on a pack of 18650 cells 4 lots of 3 in series. Runs radio 25w nav lights and internal light. None used much seems to last all season. Charged with a 3s charge control board. ol'will
Click to expand...
That’s clever. Did you make it yourself?

But won’t three of them only give you 4.2 Volts x3=12.6 Volts?

That’s fine as long as the voltage does not drop much. If if drops too much you won’t be able to use the radio, which might be important.

But with such a small pack you may be able to keep it fully charged virtually all the time via solar panels and wind turbine?

When flat each cell goes to about 3.7 V doesn’t it? Does the radio stop transmitting at 11.1Volts?
 
Dear William, I can’t edit my last post to you at 19:45 hours UK time until it passes moderation but I also meant to ask (without getting into the amp hour argument):

How many amp hours do you calculate that you get from the pack?

I looked up specs, but the amp hours quoted for those cells vary wildly depending upon which site I look at.
 
Cerebus said:
Dear William, I can’t edit my last post to you at 19:45 hours UK time until it passes moderation but I also meant to ask (without getting into the amp hour argument):

How many amp hours do you calculate that you get from the pack?

I looked up specs, but the amp hours quoted for those cells vary wildly depending upon which site I look at.
Click to expand...
Yes I made it up myself in a small plastic box. Each 18650 is rated at 2.2 AH so 4x will give 8 AH. The 3s controller sits inside the box. NB 2 perhaps 3 aH seems to be the realistic max for 18650 lithium cells. Any claim by Chinese suppliers of more is suspect and in fact some sources provide really poor cells. (ultrafire) I fitted a small vbolt meter on front via a switch. I love some Chinese stuff. The radio seems perfectly happy on l;ow voltage. Obviously some less power than 25w but not noticeable range reduction. I could charge it with a solar panel which I used to use on Nicad battery but now find it easier to take it home for recharge. ol'will
 
William_H said:
Yes I made it up myself in a small plastic box. Each 18650 is rated at 2.2 AH so 4x will give 8 AH. The 3s controller sits inside the box. NB 2 perhaps 3 aH seems to be the realistic max for 18650 lithium cells. Any claim by Chinese suppliers of more is suspect and in fact some sources provide really poor cells. (ultrafire) I fitted a small vbolt meter on front via a switch. I love some Chinese stuff. The radio seems perfectly happy on l;ow voltage. Obviously some less power than 25w but not noticeable range reduction. I could charge it with a solar panel which I used to use on Nicad battery but now find it easier to take it home for recharge. ol'will
Click to expand...
Excellent. Thank you
 
18650 cells can be in various capacity's .... from about 1200mA/h ... to about 2500 mA/h ..... and as Will says - quotes higher than that are suspect. If actually higher - then the output rate suffers .....

Like NiMh - if you have high capacity - the max amp out rate is reduced ...

Such a pack as Will has - can be charged at home and it will have extremely low Self Discharge ... but if mains power is available at mooring - a User Programmable Hobby Charger such as Skymax / Imax etc can charge such pack quickly and efficiently...... or plug the charger into the car ciggy outlet and it will charge there while driving to / from the boat !
 
You could also opt for one of those 299 Wh powerstations. Those are a nice all in one package that charges phones, has an oldschool 12V car/cigarette lighter socket and have a 600 watt inverter for 230v ac. They come shipped with a 100 watt solar panel for about 255 euros from Ali express. Im thinking to fit my Hunter Formula One with one as all in one portable power solution.
 
Refueler said:
18650 cells can be in various capacity's .... from about 1200mA/h ... to about 2500 mA/h ..... and as Will says - quotes higher than that are suspect. If actually higher - then the output rate suffers .....
Click to expand...
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
 
Last edited:
Colin Brown said:
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
Click to expand...
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.
 
You must log in or register to reply here.

Share this page

Top