Using Load connection to charge 2nd battery

[ReGult51]

Hello. Apologies if this has been covered prior....

I have The Kid charge controller charging my house battery, that supplies constant power to a 12v fridge. 245w panel keeps this battery charged all the time, reaching full charge prior to noon. I also have a secondary aux battery (OEM supplied) to power other accessories, such as 12v Maxxair fan. This battery is charged by the vehicle alternator. Over time, when the vehicle isn't run often, the charge level of the secondary aux battery will run down.

Since I have extra power that the solar panel is supplying but unused, I was thinking if there's a way to use the Load connection from The Kid to supply power to the secondary aux battery.

Love to hear anyone's thoughts on whether/how this could work.

Thanks.

[ClassicCrazy]

Are they  both the same kind of batteries ?

Maybe you can use Diversion or PWM Divert modes of the load . I have not used any of these.
I am wondering how the voltage to the second battery would be regulated , but if the load voltage is the same as your main charged battery maybe it would work okay. You could set the current to the load low enough that it wouldn't ever over charge the battery on the load.

But I am wondering if you would want to use a relay to isolate the two batteries somehow. There may be a problem if they are not isolated from each other because I remember people having issues if the grounds between load and PV go into the Kid wrong.

So perhaps someone else knows. 

Larry

[tecnodave]

CC and reGult51

I'm thinking that will be problematic as the kid monitors current using the negative lead. The second battery negative does not return to ground thru the kid so it won't know how much current......it would not see any current thru the diversion port as the current does not return there.

td

[ReGult51]

Thank you for the replies. Answers/Some thoughts:

- They are both different batteries. The Kid charges and monitors (via Whizbang) the 8D AGM battery. The 2nd Aux battery is a 95Ah (non-AGM) battery that was installed by Mercedes as part of a Sprinter van option package, along with the isolation relay. This battery is monitored by a Xantrex Linklite battery monitor and is charged when the vehicle is running.
- Looking further through the The Kid manual, I'm thinking the best mode for the Load is "Float On," so that when the 8D battery enters float charging mode that The Kid will divert solar energy to the Load.
- Initial thoughts may be to use a smaller charge controller (6-20 amp limit) that the Load from The Kid supplies. The smaller charge controller monitors the 2nd Aux battery charge and will modify charging profile appropriately based on battery level. Using The Kid Load Amp limit function, I could match that to the charge controller amp limit.

It seems like that should work, but perhaps I'm missing something so any thoughts would be helpful.

Thanks.

[ClassicCrazy]

Give it a try , probably won't hurt anything.

Since the load voltage is tied to the primary battery voltage, you may not even need a second charge controller since as the second battery comes up close to the same voltage as the primary battery it won't be accepting much current anyway and won't go higher in voltage than the primary battery I think.

Larry

[thanasis]

Hi ReGult51, I have a 2006 T1N with a very similar setup as yours in terms of batteries and solar. I have been thinking of the possibility of charging the sprinter aux battery from the PV via the Kid, as you have. Would you mind sharing the results of your try. My AGM battery is located in the back of the van under the bed, and so is the Kid. 
   Thanks
   Thanasis
PS. Are you on the http://sprinter-source.com/ forum?

[eraeco]

I used the PWM Divert function and it works perfectly for surplus water heating. I don't think you can use any of the load functions for a second battery, the problem is that it may draw more than 30 A from the load output, so the load fuse will trip. You must not connect any load of more than 30 A to the load output.