Epic solar boat adventurer - deep cycle battery performance

I put my sweet looking battery to the test today to see what would happen running the motor at half speed.

Fresh looking isn't it.

I decided to run it on speed 3 of 5 to see what kind of range I might get without any sun.

I should get around four hours of full sun in spring on the mighty River Murray on a fine day.

Or so I'm reliably informed.





Much of the country on the lower half of the river is effectively desert so there should be plenty of sunny days.


As I move further upstream (to the right) the weather will get more and more overcast. The beginning of the river is in dairy cow country I think. The middle (shown here) is more like that kind of country that's good for growing a goat... maybe even two goats. A few meters either side of the river is nice (in an Australian kind of way), but this is a very, very old land, and this river has dug out a trench to run through so it could ignore the vast parched land surround it and just on with doing it's own thing.

 I have no idea what that being upstream will mean to my levels of sunshine at this stage.

But I wont be in any hurry, so I don't really care.

Today's test involved running the motor, and writing down some numbers every half hour. I also turned the motor off for a minute, then wrote down some more numbers.

Minutes	1	30	60	90
Amp Hours	less than 1	8.71	16.14	23.29
Volts under load	11.7	11.44	10.94	10.36
Volts after 1 minute rest	12.4	12.22	12.06	11.9

After the test I waited an hour and the voltage had bounced back to 12.31v.

I turned it on for another 10 minutes and the voltage dropped rapidly to where it was before the hour long rest.

Final numbers after the additional 10 minutes were 10.36v under load, 12v after a minute rest, and 26.54 amp hours used.

I think what all this means is perhaps my battery might be good enough. I'm hoping to keep it almost full all the time with only a small amount of use for a little light.

That should put me within range of humans for 80% of my journey, but there will be a few sections where I might not see people for a few days.

To be honest, I have no idea. 

I hope I don't die!


120 Things in 20 years hopes I don't die.

Epic solar boat adventurer - Stress testing my old battery

I've had this big old deep cycle battery for years, and I don't know enough about it so I thought I'd learn some stuff.

It's a conventional, unsealed, 100ah lead acid, deep cycle thing.

At least I think it's 100ah. That's the kind of thing you'd think someone would emboss onto the side rather than adding it as a stamp. That and the voltage.

At least they went to the trouble of embossing the + and - marks.

So with this kind of battery, it seems they don't mind being run down as much as, say... a car battery might. Car batteries hate it when they are run down, and it shortens their lives in a big way.

A deep cycle battery (also called a flooded battery apparently) is a bit more forgiving, but they still see damage with every bit of use. The lower you allow the voltage to get before recharging, the less charge cycles you get from them before they need replacing. 

As I understand it, 11.8v is considered "empty", but that's at rest 6 hours after you stop using it.

I need to know what "empty" is when I'm cruising along drawing 20 amps or 35 amps (that being the amount of juice the motor pulls from the battery at speeds 4 and 5 of 5.

So my education for today turned into more questions than answers. It looks like it's business as usual.



120 Things in 20 years thinks the Internet might not know something I need to know.