Is This Schematic a good design/application ?

[Cody1944]

Good Morning,
I am a licensed electrician, old school, and I am just now getting actively involved with batteries, inverters etc.
Would anyone like to take a look at this schematic? Is there a better way to connect the charging unit?
I am operating the batteries separate from each other, when one depletes I open that circuit and close the second one.
Will Batt 1 charge correctly if I plug in the charger ? Will Charging voltage flow to Batt 2 while Im using it ?
Thank You
Cody

 

[Lucien Nunes]

You don't mention what chemistry these batteries use - I am going to assume regular lead-acid batteries but please clarify if not. Both batteries will charge if both switches are closed, as they will then be in parallel. It's not ideal to hook up two batteries in very different states of charge to one charger, as the charging program might not provide a full charge to the low battery as it will be misled by the terminal voltage being raised by the full battery. Conversely, the full battery might be slightly overcharged during the equalise stage of charging the low one. It is best to connect the charger directly to one battery at a time, or use two chargers.

If possible, it is also normally better to discharge both batteries at the same time rather than one after the other. If they both start out equally charged, each battery will see only half the inverter current, which allows the internal chemistry to function more efficiently. Especially at fast rates of discharge, you will then get slightly more total run-time before they are both depleted. Discharging both batteries half-way and then recharging both puts less strain on them than discharging one all the way before recharging, so you would see a modest increase in lifespan too.

 

[Cody1944]

You don't mention what chemistry these batteries use - I am going to assume regular lead-acid batteries but please clarify if not. Both batteries will charge if both switches are closed, as they will then be in parallel. It's not ideal to hook up two batteries in very different states of charge to one charger, as the charging program might not provide a full charge to the low battery as it will be misled by the terminal voltage being raised by the full battery. Conversely, the full battery might be slightly overcharged during the equalise stage of charging the low one. It is best to connect the charger directly to one battery at a time, or use two chargers.

If possible, it is also normally better to discharge both batteries at the same time rather than one after the other. If they both start out equally charged, each battery will see only half the inverter current, which allows the internal chemistry to function more efficiently. Especially at fast rates of discharge, you will then get slightly more total run-time before they are both depleted. Discharging both batteries half-way and then recharging both puts less strain on them than discharging one all the way before recharging, so you would see a modest increase in lifespan too.

Hello Lucien
Good Information,
These are Lithium Ion Batteries. 23ah each


Thank You
Cody

 

[DPG]

As above, a charger will not be able to correctly charge two batteries connected simultaneously.

 

[Cody1944]

As above, a charger will not be able to correctly charge two batteries connected simultaneously.

According to the manufacturer, parallel connected is required

 

[DPG]

According to the manufacturer, parallel connected is required

But not with one flat battery and one partially charged surely?

 

[Lucien Nunes]

Batteries are often connected in parallel, but they tend to remain that way for life, or at least for multiple complete charge/discharge cycles, so that they are in the same state of charge and have the same requirements to complete their cycles. It will work, I am just saying that you might not get optimum performance from charger or batteries that way. Li-ion accepts faster discharge than lead-acid without significant loss of usable capacity.

 

[Sparkgap]

Lithium ion chargers will not charge if the battery voltage drops below a certain minimum voltage. There are ways of getting them to do so, usually by connecting another charged battery in parallel for about 15 secs, but you have to be careful as they can get quite warm due to the high current flow.