Deep Cycle 12V Battery

[multiweb (Marc)]

What would you recommend? Need to draw 4-6Ah max for 10 hours.
Thanks for any pointers

[davewaldo]

I find Glass matt batteries (AGM) to be the most economical deep cycle battery. They are no spill like a gel, but much less fussy to charging.

There was a thread a little while ago about batteries and someone posted a link to a home business that sold solar equipment and batteries. They had good quality batteries at good prices if I remember correctly.

Perhaps do a search and see what you can find.

I have an 30AH AGM battery battery I got from Battery World, its awesome!

From what I was told, deep cycle marine batteries are worth about 200-300 full discharge cycles. Whereas a good AGM is worth 600+.

I think you would want a 100ah battery (50% more than required). Or perhaps make a battery box with 2x 50ah batteries.

There are some good battery box designs on this forum if you do a search.

Good luck

Dave.

[gb_astro]

Those AGMs are heavy!!!!
Make sure you can lift it if you need to travel.

gb.

[multiweb (Marc)]

After a bit of reading on the matter I'm picking up a 75Ah AGM battery tomorrow. Also buying a 4 stages charger. From what I heard there's no point deep cycling something that wasn't designed for it and any lead acid car battery or marine will eventually die faster, so it's worth spending a bit more initially and go for the long run. Thanks for the links and info guys.

[davewaldo]

gb is right, that will be a VERY heavy battery... but a great one by the sounds of things!

[MrB (Simon)]

Originally Posted by multiweb

What would you recommend? Need to draw 4-6Ah max for 10 hours.
Thanks for any pointers

Is that 4-6Ah max(0.4-0.6A for 10 hours)
or 4-6A max for 10 hours (40-60Ah)?

If the former you'll only need a smaller battery, say 20Ah,
if the latter, the 100Ah mentioned is bang-on.

Get the largest you can afford and can comfortably move around, as the deeper you discharge the shorter the life of the battery.
SLA's lasting 20+ years is not uncommon if looked after and shallow discharged.

The following is an indication of what effect Depth Of Discharge will have on cycle life...
(!! Manufacturer dependant(Energystore shown), check your manufacturer's data-sheet)
4,000 cycles @ 10% DOD
3,800 cycles @ 20% DOD
3,500 cycles @ 30% DOD
2,500 cycles @ 50% DOD
1,500 cycles @ 80% DOD
(your 75ah battery @ 6A x 10h discharge = 80% DOD.... actually deeper because the 75Ah rating is likely at standard 20hour rate(3.75A x 20h), just to complicate things!!)

[multiweb (Marc)]

You're absolutely right. Later on I'll probably need to run two in parallel. For now I'm going to run the laptop off the AGM and the mount + camera off the two celestron power tanks [2x17Ah]. See how I go for the night next week-end. I reckon the laptop IS the drain.

Originally Posted by MrB

(your 75ah battery @ 6A x 10h discharge = 80% DOD.... actually deeper because the 75Ah rating is likely at standard 20hour rate(3.75A x 20h), just to complicate things!!)