10W solar panel on a 50Ah cranking battery Regulator needed?

[Avocet]

Hi All,

"Asking for a friend"... (no, really)!

He has a 50Ah cranking battery and a 110 Ah leisure battery. He was going to get a couple of 10W solar panels and leave one connected to each battery over the winter to keep them topped up. I think the leisure battery will be fine with that, but was wondering about the smaller cranking battery. Would that be OK with a 10W panel permanently connected, or does he need a regulator too?

 

[garymalmgren]

Winter= not much sun.
10 watts = not many watts.
No need for a regulator.

However they (non MPPT type) are very cheap, so why not fit them?
You get USB outlets built into the regulator

PWM Solarregler 12V/24V Auto. 30A20A10A LCD Batterie PV Zelle Panel Ladegerät Regler Lampe 100W 200W 300W 400W 500W - AliExpress 13

 

[William_H]

Far more reliability without a regulator. Just hook it up. Fuse at the battery end of wiring. ole'will

 

[VicS]

Hi All,

"Asking for a friend"... (no, really)!

He has a 50Ah cranking battery and a 110 Ah leisure battery. He was going to get a couple of 10W solar panels and leave one connected to each battery over the winter to keep them topped up. I think the leisure battery will be fine with that, but was wondering about the smaller cranking battery. Would that be OK with a 10W panel permanently connected, or does he need a regulator too?

There are a couple of "rules of thumb" regarding this.

If the size of the panel , in watts, exceeds 10% of the battery capacity, in Ah, a regulator is required.​

​

Panels over 10 watts should always have a regulator.​

On this basis the 50 Ah battery/10 watt panel combination should have a regulator but in wintertime probably not necessary.
I have found that a 5 watt panel will easily keep a small battery charged without needing a regulator.

 

[Neeves]

Hi All,

"Asking for a friend"... (no, really)!

This sentence, or one like it, is posted every so often, or at least occasionally

Why do people ask a mate to pose the question on their behalf. Joining YBW is free, its easy to join, unless you are banned. The forum benefits from a varied membership and depends on people, with diverse views, to contribute. If you run a commercial activity in conflict with Forum rules - you need to be discrete.

So....why?

Jonathan

 

[andsarkit]

A 10W panel will produce a maximum of about 5Ah per day in summer. Halve this for less winter daylight hours and halve again for less sunshine and reduce again for imperfect orientation. This will bring it down to less than 1Ah per day which is an average of about 40mA. A Victron MPPT controller draws about 25mA and will waste most of the output although a simple PWM controller will used less standby current.
You will be fine on the smaller battery in winter with a direct (fused) connection. Just check the voltage regularly especially on a sunny day and ensure it is not much above 14V. When I did this with a 30W panel feeding 2 x 100Ah batteries I found the batteries sat at about 13.6V throughout the winter. If you find the voltage starts to get too high you can always change the orientation of the panel to a less favourable direction. (I split the charge with Schottky diodes so I didn't have to directly parallel the two batteries and the lowest battery would take most of the charge.