Small Solar Maintenance Charger Advice Pretty Please [emoji120]

G’day NP.com.au Team,

Hoping for some advice please on happy/safe usage of anyones experienced purchase of small solar maintenance chargers?

Needing to purchase a couple for 12v batteries around the property on contraptions that have slight parasitic drain occuring.

Did purchase a cheapo version years ago for a diesel dam pump and found its battery swollen/cactus after checking some months later.

Assuming the cheapo ones regulator thingymebob failed and destroyed a $200 battery so hoping for that to not happen again :-(

Many thanks
Mark



Sent from my iPhone using Tapatalk

Quote:

---

Originally Posted by MB

G’day NP.com.au Team,

Hoping for some advice please on happy/safe usage of anyones experienced purchase of small solar maintenance chargers?

Needing to purchase a couple for 12v batteries around the property on contraptions that have slight parasitic drain occuring.

Did purchase a cheapo version years ago for a diesel dam pump and found its battery swollen/cactus after checking some months later.

Assuming the cheapo ones regulator thingymebob failed and destroyed a $200 battery so hoping for that to not happen again :-(

Many thanks
Mark



Sent from my iPhone using Tapatalk

---

I bought one from Jaycar years ago, have always had I plugged in to my camper never caused issues with the batteries and I think it's probably been around for about 10 yearshttp://www.nissanpatrol.com.au/forum...2020/10/63.jpghttp://www.nissanpatrol.com.au/forum...2020/10/64.jpg

Sent from my SM-G965F using Tapatalk

You would only need a small panel as pictured by rustynail and if your worried about the regulator get the smallest VictronConnect regulator .
That way you can check on the battery's last 30 days of data using your phone if your in Bluetooth range , no need for a multimeter .

I do like the sound of that Thanks Rob, Welcome Back Old Mate!


Sent from my iPhone using Tapatalk

Look up / Talk to Low Energy Developments Marko mate.
They have various small sized panels for various purposes and fittings , chargers etc... They know solar !
All my solar needs go there.

Sent from my Pixel 3a XL using Tapatalk

If the panel max output is below one amp (say you have a 10 watt panel) and a battery above about 70 amp hours just hook the panel straight to the battery.

The internal resistance of the battery acts as a load and effectively regulates the panel as good or better than a separate Reg.

I have small panels/ no reg direct to Battery on my water feature pump (5 watt to 30 AH battery), maint. charging my boat (20 watt to 2 x 90 AH) and some garden lighting .

The rule of thumb is 1:100 IE 1 amp Panel current per 100AH of battery capacity (IMHO that is conservative and I work on less) but using that ratio a standard 10 watt panel of 0.6 amp max current into 60 AH lead acid battery doesn't need any form of Reg

Some great advice, thank you kindly Gentlemen [emoji106][emoji106]


Sent from my iPhone using Tapatalk

Confirming did the old ‘Jaycar Click & Quick Collect’ for a couple of Rusty_Nails & PeeBees phone advice panels on the way home from work.
http://www.nissanpatrol.com.au/forum...2020/10/74.jpg
http://www.nissanpatrol.com.au/forum...2020/10/75.jpg
20W/1.15A direct onto the tractor battery (Lead Acid 160 RC Minutes) if I understand everyone’s thankful advice should loosely convert hopefully to 100+AH safely?
http://www.nissanpatrol.com.au/forum...2020/10/76.jpg
Will look towards a third flash bluetooth type remote version for dam pump down in the valley once time & money permits thanks heaps again Gentlemen [emoji106][emoji106]


Sent from my iPhone using Tapatalk

I wouldn't connect any panel straight to a battery without a regulator - at night time the current flows the other way.

solar panel ==> regulator ==> battery

Rule of thumb is to pick a regulator that is 125% the short circuit current/Isc of the solar panel (in offgrid use).

The Isc of your 20W panel is 1.21A so would require a regulator that is at least 1.5A

Cheap PWM regulators are basically just a voltage sensing switch which usually cut out around 14.6v and are "okay" for small jobs (10-20w for maintenance). Such regulators can be had for around $10-$15 a piece.

Good quality PWM regulators (Epever/morningstar/projecta/etc) are durable and usually do a 3-stage charge (bulk/absorption/float) and have preset charging parameters for different battery types (sealed/gel/wet). When used correctly they will keep your batteries good for many years. They will set you back around $40-$60.

If you're looking on ebay, many PWM regs are mislabled as MPPT. If what's being advertised appears to be physically small and around $15, they're not MPPT (MPPT is not something you need to worry about for what you want to do).

Quote:

---

Originally Posted by pollenface

snip... I wouldn't connect any panel straight to a battery without a regulator - at night time the current flows the other way.

---

Pls excuse the snip.

That is what the "blocking diode" is for, to prevent reverse current flow when the sun isn't shining.

Also, a PWM Reg will reduce the effective rating of the panel by about 1/4 to a 1/3rd.

Panel direct to battery is very common in many standby applications.
For example there are no regs on all of the small maintenance charging panels you see for vehicles that you sit on the dash and plug into the ciggy lighter
It is also why most Panels under 20 watts come with alligator clips and not MC style solar connectors.
The battery voltage on my boat sits at approx 12.8 off charge and rises to 12.9 when the panel is in full sun.

Effectively the battery is appearing as a huge capacitive load to the panel and in practical use the system will perform better than a PWM reg system with the non-regulated panel output running close the the max power knee of the performance curve IE max current output so almost like it has an invisible MPPT Reg.

BUT... the Panel output has to be such that the load of the fully charged battery still draws a current flow so as long as you don't put too large a panel in place and the panel has a blocking diode it should have no noticeable adverse effect to the battery life.

I do, however, totally agree that a panel without a blocking diode won't work as desired and once you get up in solar panel power to battery capacity past a certain point you have to use a Reg.