Battery charging times

[TwoBlocked]

Trying to find a chart, graph, calculation for determining how long it takes to charge a 110Ah lead acid battery from 50% charge to 90% charge.

Of course you fine folks are going to want to know more. This is for a gas field application. No utility power is available. Solar/battery is primary but sometimes needs help. The idea is to have a small standby generator come on when the batteries get down to 50% and boost them up to 90%. The load on the system is for running controllers, radio comms, solenoid valves, a small air compressor.

My concern right now is choosing a genny with a service schedule so that it need only be done once a year. That depends on the hours it runs, which depends on how long and how frequently the batteries need to be boosted with the genny, which depends on how long it takes to charge from 50% to 90%.

 

[retirede]

Do the math. 40% of 110 AH is 44 AH. So a charger with 1A output will take 44 hours, 2A, 22 hours, etc.

 

[TwoBlocked]

Do the math. 40% of 110 AH is 44 AH. So a charger with 1A output will take 44 hours, 2A, 22 hours, etc.

Does it really work that way? Like if I have a 100 amp charger... A charger reduces the amps as the volts increase.

 

[winnie]

For low charging rates, @retirede is correct.

For fast charging, you bump into voltage limits as you approach full charge. The time to charge will get strongly dependent on the capacity and smarts of the charger.

Without getting fancy, I think you are limited to about C/3 (meaning a 37A charger for your 110 Ah battery) and your 40% charge swing would take about 80 minutes.

If you get fancy ($$$) with the charger them the time could be even shorter, but that takes a charger that carefully recognizes end of charge conditions, cell balancing, etc.

Jonathan

 

[pv_n00b]

You are talking about the difference between a trickle charge (1-2A) and a 3 stage charger. Your bulk charge rate (50%-80%) is going to be higher and depend on the type of LA battery you have and how many recharges you want to get out of it. The 80 to 90% charge rate is the absorption charge rate. It is less than bulk so it takes much longer to get that last 10%. You need to determine the bulk and absorption charge rates for your particular application and then the math is that easy. This information will be available from the battery manufacturer.