Sizing Genset to Battery Chargers

[Tkmork]

Hello to All,

I am curious on how to size a standby genset to a battery charger / battery bank configuration. The battery charger is rated at a 480VAC input and a max rated 90A that rectifies it to a 130V VDC output at a max rated 250A. The output is then tied into a DC bus that supplies various DC loads as well as the battery bank in which it is tied to. The battery bank is a 1783 Ah, 60 lead acid battery bank rated at 130V.

Do I merely size the generator in regard to the worst case scenario input to the battery charger itself? Or is there sizing requirements based on the intended loads off the DC bus as well as loads required when the battery bank is depleted? I ask this primarily because another individual before myself had sized the load requirement of the battery charger to be 170 kW which seems awfully large to me, but I may be mislead. Thanks.

 

[topgone]

Know your DC load first. You have to add these load amps to the charging amps to the batteries on a worst condition scenario.
Total charger amp rating = DC loads + battery charging amps max.

 

[SceneryDriver]

Know your DC load first. You have to add these load amps to the charging amps to the batteries on a worst condition scenario.
Total charger amp rating = DC loads + battery charging amps max.

DC load doesn't matter for generator sizing. The load on the generator can never be more than 480VAC at 90A, the rated input of the charger. You size the generator to the charger's input amps x 1.25 (continuous load), plus anything else you want to power from 480V at the same time.

If the DC loads discharge the batteries faster than the charger can recharge, installing a larger generator won't help. You're still limited by the capacity of the charger. If use-while-charging draws more than 90A, the charger becomes a DC power supply supplemented by the battery bank. Use-while-charging may require a larger charger that can supply the DC loads while still recharging the battery bank at a reasonable rate; only you can determine that based on your DC loads.



SceneryDriver