I have ordered a Orion-Tr Smart DC-DC 12/12V charger. I need to charge a small 10Ah 12V AGM battery. But when I tried to configure the maximum charge current, I realized that it is not possible to limit the max charge current on this model.
Can somebody tell me if it is ok to charge this small AGM battery with 20A or is there another product to charge it from the 24V service battery?
Hi @dloy,
It’s a valid concern.
Your battery will have a maximum specified charge current in its data sheet. Excessively exceeding that will void the batteries warranty, and probably reduce its life.
In the best case situation you have a charger that can be current limited appropriately for the battery you are using, for an AGM battery, a 0.1C rating or roughly 10% of the batteries Ah capacity in Amps is a very safe industry standard charging rate.
What actually happens in reality is that the DC to DC charger will not always provide its full charging current, but it will probably provide over what that battery specifies if it is charging from being flat.
The battery voltage will rise very quickly, and the battery will charge very quickly, and reduce its service life. Generally speaking the slower you charge an AGM battery, the longer it will last, but that 0.1C rating is usually a safe spot. Some can take more if they are good quality.
If you are just keeping the battery charged, and not doing deep discharge/recharge cycles, then it’s fine to use that bigger charger. As the target voltage is reached the current will be reduced, and in the float stage it will just trickle in.
So that’s a lot to say it really depends on how you are using it if this is charger is ok or not.
Hello,
thank you for all the good input. I am keeping the charger battery of a gas engine dinghi charged when not in use. Probably the 20A will never be seen, but I am a bit hesitant since the charger wiring is not speced for 20A. I found an MPPT 100/20 in my stock. It seems to be the perfect match for my application.
- It supports AGM
- It supports 12V batteries
- I can limit the maximum charge current to 3A
- It has VE.direct that gives me Modbus access for the management system
If nobody disagrees I will go with this handy product.
Thanks for all your support,
Dietmar
Hello Dietmar,
you can’t use an mppt as dcdc charger, they can only be used on solar panels.