Cloona
Well-Known Member
if i leave it connected up for a couple of weeks can it overcharge the battery and cause damage or a fire ?
solar panel trickle charging battery - will it blow up ....?
- Thread starter Cloona
- Start date
dunedin
Well-Known Member
Wired direct (!) or via what type of solar controller?
VicS
Well-Known Member
Mine is normally connected all summer........ no controller but its only a 5 watt panel
This year its been connected all winter too.
If the panel was any bigger I would use a controller of some sort or another
lpdsn
Well-Known Member
I think there's an oft quoted figure of something like 10%. e.g. 10W panel into 100Ah battery is the maximum without a controller. In reality though, hardly worth it as basic solar panel controllers are pretty cheap. Try looking on Amazon. The cost doesn't really rise until you're looking at an MPPT controller to squeeze a bit extra out of the panel.
Kelpie
Well-Known Member
Depends on the size and output of the panel, and the size of the battery.
Overcharging can boil off the electrolyte. To be completely safe, the panel should only keep pace with the self discharge of the battery.
I've always fitted a fuse in there somewhere, I don't know what the odds are of a panel shorting, but there is a lot of energy in a battery.
Overcharging can boil off the electrolyte. To be completely safe, the panel should only keep pace with the self discharge of the battery.
I've always fitted a fuse in there somewhere, I don't know what the odds are of a panel shorting, but there is a lot of energy in a battery.
RichardS
N/A
A 200W panel into a 50Ah battery = misery
A 5W panel into a 50Ah battery = happiness.
Richard
VicS
Well-Known Member
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AndrewL
Well-Known Member
This article disagrees and says that you always need a charge controller http://www.pbase.com/mainecruising/do_i_need_a_controller.
His tests showed that a 400Ah bank, once fully charged, only required 0.1 amps to maintain 14.4V.
His tests showed that a 400Ah bank, once fully charged, only required 0.1 amps to maintain 14.4V.
RobbieW
Well-Known Member
Reading a little further down the article it points out that the need for the controller is to keep the voltage down to a float level once the battery is full. I'm not sure if thats the point you're trying to make. 14.4 is not a float level, the 13.6 quoted in the article is a more recognised float voltage which is less likely to damage a battery if left applied long term. At least I hope not as its what I do, I have the luxury of a controller with user defined settings so when the boat is left the bulk/absorb modes are disabled.
RichardS
N/A
We've discussed that article before ...... and poo-poo'd it.
Take into account that the batteries are probably not 100% charged to start with, there is no or poor sun for 75% of every 24 hours Even during the "sun" period, there is probably no sun for 50% of the time, the batteries are self-discharging during all these "no sun" periods, the panels will operate below their rating for 99% of the time etc
No-one is saying that there won't be some slight electrolyte loss from open cell batteries at some times ..... but that's liveable with.
Richard
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Kelpie
Well-Known Member
Given that you can pick up a basic charge controller for under £20 I don't really see why anybody argues about this.
RichardS
N/A
So if I buy a simple 5W trickle charger panel for £15, you think it makes sense to buy a controller for another £20?
Richard
Kelpie
Well-Known Member
So if I buy a simple 5W trickle charger panel for £15, you think it makes sense to buy a controller for another £20?
Richard
I think it makes sense to spend £20 protecting a bank of batteries costing £80 each...
jac
Well-Known Member
That's the key thing for me. A cheap panel and controller will be less than the cost of 1 cheap battery. Also bear in mind that some panels have open circuit voltages ( max) of over 20 volts. Do you really want to be pouring that ( even at 5 W) into a fully charged battery. A nice cheap £20 controller will step that down to something appropriate
RichardS
N/A
So if I buy a simple 5W trickle charger panel for £15, you think it makes sense to buy a controller for another £20?
Richard
Assuming that answer is a "Yes" to my question, I'll have to abandon this thread and join the "battery suicide pact" along with the other million purchasers of 5W trickle charger panels.
Richard
jac
Well-Known Member
Assuming that answer is a "Yes" to my question, I'll have to abandon this thread and join the "battery suicide pact" along with the other million purchasers of 5W trickle charger panels.
Richard
But don't a lot of those only output about 13.5 - 14v. I would agree those would be fine. it's more the high voltage panels I would worry about
RichardS
N/A
Read my post #12 again.
That was the question put .... and it has been answered in the affirmative.
Richard
GHA
Well-Known Member
Doesn't really work like that - a 5W panel will have the same open circuit voltage as a similar design 100w panel, 21v ish?
It's the battery which pulls the voltage down as it charges.
And as the previous links show for a completely charged battery it doesn't take much current to push the voltage up to unhealthy.
With a 5w panel in the UK probably very unlikely but maybe possible if you've been motoring overnight or something and leave the boat on the sunniest day of the year.
VicS
Well-Known Member
I typically find with my unregulated 5 watt panel and 60 Ah leisure battery that the volts are up to about 18v. What detrimental effects have I failed to notice all these years?
jac
Well-Known Member
Similar design is the key part - Depends on the panel.
http://uk.farnell.com/raloss/sr5-36/solar-panel-5w/dp/1462491 - This one is 17.
http://uk.farnell.com/camdenboss/cbspgf-05/solar-panel-36-cell-0-26a-5w/dp/2565654 This one is nearly 20.
Such a small trickle charger though is only really of use on a engine starter battery to keep up with self discharge. It will be no real help on a large domestic bank.
From Richards description I was expecting a product that was specifically designed to trickle charge / float charge a battery. I was therefore expecting a product with a lower maximum voltage - i.e. fewer cells.
With a panel outputting a lower voltage / amperage I would agree - no point in a charge controller but for a larger one, it's not worth the risk of saving less than £20.
