Charging multi-battery system

:grr

I'm trying to get my stall shifter to work off solar. I have a 10 watt .7a panel connected in parallel to three batteries; 2 12 volt and 1 6 volt. All three batteries are new.

The batteries are not fully charging on the solar panel. I can connect the shifter to a battery charger and fully charge the batteries, I get approx 3.5 hours of non-continuous use (running the motor full out) before needing to recharge the batteries.

When I use the solar panel to charge the batteries, they never fully charge. I've left the system sitting in the sun for two days, and it was getting approx 8 hours of good sun light. I get approx 1 hour of use this way.

Fully charging the batteries on a charger and then using solar to maintain still does not work. I get approx 5 hours of non-continuous use before having to connect to the battery charger.

Is the panel large enough or is it something in the way it's wired that's preventing the charge?

• Super Moderators Posts: 26,666 admin
Re: Charging multi-battery system

I assume that a stall shifter is something like this?

So, several issues/questions...

A 10 watt solar panel is very small--Hardly enough power to run a transistor radio or a night light. I would assume a shifter would take something like 100-300 watts to run properly. Yes, you can connect storage batteries to a solar panel, store up the energy from 5 hours of sun, and then run a 300 watt load for:

10w * 5 hours * 60 min/hour / 300 Watts = 10 minutes per day...

Not sure how you are connecting two 12 volt and one 6 volt battery together... And the solar panel has to have a higher output voltage than the maximum charging voltage + charge controller voltage (for a 12 volt battery, your solar panel would need to be rated ~17.5+ VDC Vmaxpower).

Unless your shifter uses much less power than I thought and/or your batteries are quite small--The 10 watt panel is about the right size to maintain the charger of your batteries for long term storage--and not large enough to really give you much usable power for a mechanical piece of equipment.

In any case, this is full of guesses on my part... More details would be helpful (how much power/current/voltage required by the shifter and how long you need to run it every day).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 7,224 ✭✭✭✭
Re: Charging multi-battery system
jtwiss wrote: »
:grr

I'm trying to get my stall shifter to work off solar. I have a 10 watt .7a panel connected in parallel to three batteries; 2 12 volt and 1 6 volt. All three batteries are new.

<snip>

Is the panel large enough or is it something in the way it's wired that's preventing the charge?

1) You need a MUCH, much, larger panel.

2) You cannot mix voltages, remove the 6v battery from the system

3) What BB said !
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

• Posts: 6,290 admin
Re: Charging multi-battery system

Yeah, these guys are telling you the truth.
Unfortunately,what many sellers don't tell their customers, a 10 watt panel is nothing more than a battery maintainer, about enough power to keep the battery from going dead over time due to it's own internal losses. Not enough power to charge anything much more than some little toy type battery, and even some "toys" have some pretty heavy duty batteries that a 10 watt panel can't properly charge.
And, you must never connect a 12 volt battery in parallel with a 6 volt battery! The 12 volt batteries will discharge into the 6 volt battery, trying to equalize the voltages. Very serious and potentially dangerous problems can result.
You did come to the right place though to ask your questions. The guys here may not give you the answer you wanted to hear, but they won't steer you wrong.
Good luck
Wayne
• Posts: 6,290 admin
Re: Charging multi-battery system

Yep - exactly like that -- It is a Brockwood stall shifter and I love it, I just want to make it solar. The panel needs to be 1'x2'. Is it possible to get 100 -300 watt panel that small? or am I going to have to set something up and then connect the shifter?
• Posts: 6,290 admin
Re: Charging multi-battery system

Thanks for the heads up on the 12 volt and 6 volt batteries not playing nicely together. And I'd much much rather hear the truth.
• Solar Expert Posts: 5,090 ✭✭✭✭
Re: Charging multi-battery system

You could however add a second 6volt battery in series with the first, and then parallel the two sets together. You will run into some trouble however if the batteries are of significantly different sizes/amp hour ratings, ages etc.

Icarus
• Super Moderators Posts: 26,666 admin
Re: Charging multi-battery system

jtwiss,

You really need to define the electrical load... Voltage (range), current, AC/DC, how much it is used, etc...

You can connect a solar panel to a motor (done all the time with solar powered wells)--however, a power on demand type system probably would be better supplied with a battery (only do the work when the sun is shining?).

Once you decided on a battery--then you need to go the whole route--how much power, how much sun, charge controller type, battery size/type, fusing, what do you do during winter (alternate AC charger), if the load is a 120 VAC 60Hz device--then adding an inverter, etc.

Not trying to avoid or make the project overly complex--but if you want this to last more than a few months as a toy--you really need to look at the whole project requirements (not that there is anything wrong with learning through mistakes--but if you can avoid wasting money while learning, most people are happier).

Building a solar/battery power cart can be a fun project and very useful (a couple people here have done this before). Say this stable is too far to run power--you might want to design the solar system to provide task lighting and power for clippers, etc. too...

But, because solar is highly variable (location, weather, seasons, etc.)--understanding the limitations and requirements would be helpful too (generator backup, something you can haul back home to recharge when needed during the winter, etc.).

Does this help?

-Bill

PS: Our host has a very practical layout for their web store (panels, charge controllers, panels, inverters, etc.)... Once you know how much power you need, then it is quite easy to start to size/price the system.
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset