40 Watt Panel an dGolf Cart Batteies

[Bob Adkins]

I have a 40w panel, and a little Morningstar Sunguard controller charging a
115 Ah marine battery and a 25 Ah utility battery. It works just great. The
batteries stay topped off just lovely, and have recovered from an estimated
50% remaining charge on a couple of occasions.

Coincidentally, I will soon be needing a marine battery (for a boat) and a
utility battery (for a riding mower), and want to replace my trusty little
bank with a pair of 215 Ah golf cart batteries, in series of course.

What's conventional wisdom on GCB's and minimum PV panel size? Is there a
discharge percentage from which the GCB's can't recover without a hotter
charge?

While my usage should be very minimal (rarely below 80% remaining charge), I
may need to bleed my GCB's down to 50% on rare occasions. Think they'll
recover with a 40 watter? I do live in a sunny area at 30.5 Deg N.

Thanks,,,

-- Bob

 

[Ecnerwal]

I have a 40w panel, and a little Morningstar Sunguard controller charging a
115 Ah marine battery and a 25 Ah utility battery. It works just great. The
batteries stay topped off just lovely, and have recovered from an estimated
50% remaining charge on a couple of occasions.

While my usage should be very minimal (rarely below 80% remaining charge), I
may need to bleed my GCB's down to 50% on rare occasions. Think they'll
recover with a 40 watter? I do live in a sunny area at 30.5 Deg N.

If your _use_ does not expand, the fact that you can meet your current
load from the 40 watt panel indicates that the 40 watt panel should meet
your load with the GCBs, just with more headroom on the battery bank.
You're only going from 140Ah to 215Ah, so it's not like there's a huge
amount more self-discharge going on. If you discharge to 50% you'll need
(with no use) on the order of 32 hours of sun .vs. 21 hours of sun (for
the 140 ah bank at 50%) now for a recharge. Both are actually somewhat
more due to the imperfections of batteries, but that's the order of what
you need - 50% larger bank, same input, 50% greater time. If the bank
sits floating, the small panel can make enough voltage to equalize.

If your use is increasing, or would increase if it could, get more panel.

 

[Bob Adkins]

If your _use_ does not expand, the fact that you can meet your current
load from the 40 watt panel indicates that the 40 watt panel should meet
your load with the GCBs, just with more headroom on the battery bank.
You're only going from 140Ah to 215Ah, so it's not like there's a huge
amount more self-discharge going on. If you discharge to 50% you'll need
(with no use) on the order of 32 hours of sun .vs. 21 hours of sun (for
the 140 ah bank at 50%) now for a recharge. Both are actually somewhat
more due to the imperfections of batteries, but that's the order of what
you need - 50% larger bank, same input, 50% greater time. If the bank
sits floating, the small panel can make enough voltage to equalize.

If your use is increasing, or would increase if it could, get more panel.

No, usage is not increasing. I simply have an opportunity to rotate out my
batteries.

I know that's the way I would think things would work. But I thought I heard
somewhere that there was some point where a small panel could not bring a
larger battery back to full charge. Maybe I misunderstood.

Thanks for the nice reply Lawrence. I appreciate it!

-- Bob

 

[[email protected]]

Newsgroups: alt.energy.homepower


sunny area at 30.5 Deg N.
If your _use_ does not expand, the fact that you can meet your
current load from the 40 watt panel indicates that the 40 watt
panel should meet your load with the GCBs, just with more headroom
on the battery bank. You're only going from 140Ah to 215Ah, so it's
not like there's a huge amount more self-discharge going on. If you
discharge to 50% you'll need (with no use) on the order of 32 hours
of sun .vs. 21 hours of sun (for the 140 ah bank at 50%) now for a
recharge. Both are actually somewhat more due to the imperfections
of batteries, but that's the order of what you need - 50% larger
bank, same input, 50% greater time. If the bank sits floating, the
small panel can make enough voltage to equalize.
If your use is increasing, or would increase if it could, get more
panel.

First, information given me by Sandia National Labs battery tester is
that the Trojan T-105 golf cart battery may start out at 225AH for
the first couple of cycles, but it quickly stabilizes to a capacity
of 185AH.

Local (Albuquerque) battery store techie told me trickle charge rate
for these batteries is C/100 rate - 1.85A.

Your 40W panel should put out around 2.1 to 2.3A max. That's not
much over trickle. I'd want much more to do an equalizing charge.
Or to finish forming the plates on a new battery (mfr. only partially
does this any more). I want enough current to get the terminal
voltage up to 16V, IIRC 18V for forming.

I use a pair of T-105's in this trailer, about 9A max of PV panels,
through a Morningstar Prostar 30 controller. Overnight discharge is
around 30AH winter, 10AH summer, give or take.


Tom Willmon
near Mountainair, (mid) New Mexico, USA

Hello...Incontinence Hotline...Can you hold?

Net-Tamer V 1.12.0 - Registered

 

[Bob Adkins]

First, information given me by Sandia National Labs battery tester is
that the Trojan T-105 golf cart battery may start out at 225AH for
the first couple of cycles, but it quickly stabilizes to a capacity
of 185AH.

Local (Albuquerque) battery store techie told me trickle charge rate
for these batteries is C/100 rate - 1.85A.

Your 40W panel should put out around 2.1 to 2.3A max. That's not
much over trickle. I'd want much more to do an equalizing charge.
Or to finish forming the plates on a new battery (mfr. only partially
does this any more). I want enough current to get the terminal
voltage up to 16V, IIRC 18V for forming.

I use a pair of T-105's in this trailer, about 9A max of PV panels,
through a Morningstar Prostar 30 controller. Overnight discharge is
around 30AH winter, 10AH summer, give or take.

Thank you Tom. Good information!

I know it's a marginal situation, but worth a try. Reason I am concerned is
that my little controller can't take another PV panel. It's almost maxed out
with the single 40 watter. So if I need to add another panel, I will also be
forced to buy another controller.

When I get my GCB's, I'll zap them with a big charger. That should smack
them around enough to condition them for duty.

-- Bob

 

[[email protected]]

Newsgroups: alt.energy.homepower

Thank you Tom. Good information!
I know it's a marginal situation, but worth a try. Reason I am
concerned is that my little controller can't take another PV panel.
It's almost maxed out with the single 40 watter. So if I need to
add another panel, I will also be forced to buy another controller.

When I get my GCB's, I'll zap them with a big charger. That should
smack them around enough to condition them for duty.
-- Bob

Did you say your controller is a Morningstar Sun Guard? I have one,
rated at 4.5A. Yep, you're half way there.

Found another note: Battery tech gave C/20 for the charge finishing
(absorbtion) current. For the T-105 that would be 10A.

Ya know, these rating numbers are nice, but the systems seem to
seldom behave that way.


Tom Willmon
near Mountainair, (mid) New Mexico, USA

Net-Tamer V 1.12.0 - Registered