OT: Solar charging an array of batteries

[xena]

Not electric bike related, but you guys seem to know a lot about batteries!

I have a solar panel down the yard, 150w I think, which does a cracking job of charging the 12v battery I use for the electric fence. I have a charge controller etc on it.

I have a collection of 12v batteries that I used to charge at home and take down the yard. Could I use these in an array off the solar panel to get loads of Ah capacity (I'm thinking lights in the stables!), or would the less healthy batteries adversely affect the health of the better batteries?

TIA

 

[Jonno14]

I think you are right, The older batteries will drag down the better batteries. Plus you can't really charge more than 2 or 3 at a time from a solar panel as you may overload the charging relay. Best advice is to install LED bulbs which do not use as much current from your battery. For further battery advice go to the following site: https://batteryuniversity.com/learn/

 

[vfr400]

Here's what I'd do. After charging each one, leave it for half an hour, then measure the voltage. Any that remain at 12.6v or above are OK to put in parallel.

The number of batteries in parallel has no affect on the panel or charge controller.

I agree about the LED lights, they use a fraction of the power of incandescent lights for the same light output.

 

[Jonno14]

If you are connecting several batteries in parallel, then it is important to to connect the charging leads as follows: Negative lead to the first battery negative pole, and Positive lead to the last battery positive pole. This will ensure that each battery receives the same potential charging voltage.

 

[Jonno14]

It is also important to only connect batteries of the same type and capacity together to ensure compatibility during charging.

 

[xena]

Thanks both, very useful info. I have a few car batteries, a truck battery and a smaller battery. If they're significantly different capacities (or health) I suppose I can use them as backups rather than in the main array. I'll have to do some nice easy swappable connections, and also fit a DP isolator between the solar panel and charge controller so I don't blow the controller up when I'm disconnecting the batteries!

I have a selection of 12v LED bulbs and floods that I can use, tho I tend to do most stuff by head torch currently, so I won't be fully reliant on them!

 

[vfr400]

If you are connecting several batteries in parallel, then it is important to to connect the charging leads as follows: Negative lead to the first battery negative pole, and Positive lead to the last battery positive pole. This will ensure that each battery receives the same potential charging voltage.

That's not right. It's putting them in series, which will push the battery voltage higher than the charge voltage, so no charging can happen. If it's a 12V charge controller, it'll be set to around 14.4v, so only one battery in series. The rest have to go in parallel.