dumb dumb talk re: safe battery resting voltage

[stevewilson]

I have a couple of interstate GC2 golf cart batteries wired up as my house bank. I have, ever since I owned them, been in the habit of not taking them below 12.5v (resting).  I recently ran into somebody who scoffed at me and indicated that that was overkill, so I was wondering if I am being overly cautious and costing myself useful hours of electricity.

What is the correlation in resting voltage vs charge state?

For what it's worth, my batteries top out around 12.8v. Flashing between 12.8 and 12.9 ony charge controller display. 


Thoughts?

[Blacktank]

welcome to the site,how about an intro thread so people can say hi?

the people in the know will reply shortly

for me,my comforts are more important than a battery,so live like you want and if you run out of juice get more battery,it's only money,right?

[justjim]

The deeper you cycle a battery the fewer cycles it will yield.

[stevewilson]

Jim,

I understand that in principle, but where is the balance? I spent a couple of hundred bucks on these batteries and I would like them to last as long as is reasonable, but if I'm only taking 20% of their capacity then I feel like I'm needlessly depriving myself.

[sternwake]

I do not fear deep cycling, as much as I fear not being able to reach full charge.

If I do not expect to be able to reach full charge the next day, then I will try to not consume as much much juice.

GC-2's, take then to 12.2v without worry, just dont leave them there for extended periods, and recharge to full whenever possible, as soon as possible.

No need to baby them, just dont deliberately leave them discharged or think recharging them only to 85% on a regular basis is good enough.

[justjim]

Jim,

I understand that in principle, but where is the balance?  I spent a couple of hundred bucks on these batteries and I would like them to last as long as is reasonable, but if I'm only taking 20% of their capacity then I feel like I'm needlessly depriving myself.

There is no balance, it just is a reality. Batteries are disposable as in they all wear out. You can get more to keep the cycle lower but really you are spending as much keeping them going twice as long with lighter cycles as if you replaced them original pair when it wears out. The only difference is upfront cost and the weight and space the bank takes up.

Golf cart batteries have the thickest plates of the lead acid batteries and give the most cycles at any level of discharge.  A peek at the manufactures page will show that they too give fewer cycles the deeper they are discharged. Even Lithium do this.

Sternwake is right, keeping them properly charged will give you the maximum number of cycles no matter what depth of discharge. If the battery is rated for 500 cycles at 50% then keeping it taken care of gives you the best chance to see those 500 cycles or the 1000 cycles at only 20%. (just numbers kids)

So use your battery the way you wish you could for a while and see what the resting voltage vs the reduced use voltage is and see how many cycles both would give you. The difference may not be worthy of the sacrifice.

[rvpopeye]

X2 Stern^

It's a little more complicated than just resting voltage but after some experience , it can be helpful.  
(A specific gravity tester is the holy grail to find fully charged point.)

Use a little more and see if they charge fully the next day ,,,,repeat.

>>>>>>The idea is to use less than the charging system can replace in a (typical average) day.<<<<<<<

The angle of the sun and clouds and shading can make a big difference......

After a time , you get a better idea of the amount you can use and still get back to full charge .

Not rocket science but sometimes it seems like it   .

[Ticklebelly]

If you talk to people who have (own) golf carts, you might be able to get real world info on how far they regularly discharge their batteries. Even a course golf pro may be a source of information. I know some folk at a local golf club and their battery management routine is simply to connect to a charger at the end of 18 holes. I have no information on what life they get out of the battery packs but I think that the manufacturers of golf cart batteries would design for such a pattern of use as I described.

I have never subscribed to the hysteria over cycles as a predictor of life and am currently trying to see out 2 Six year old AGMs as I convert totally to Lithium. As some have suggested, full charge as often as possible is the goal of my battery management routine.

[ratfink56]

Welcome stevewilson and Ticklebelly.