Im setting up my truck to do some remote camping for two weeks. Going to be driving several hours each day. I will have a 300W panel on my room going through a 150/45 victron charger charging my 230AH battery. Now this should be fine for the small draws Im going to be using it for. However Im thinking about backup charging just in case I hit some cloudy days or whatever may happen. A DC to DC is out (don't want to run wires to my house battery in brand new truck). I do have an AC plug in the bed of my truck. The problem is its not powerful at all. I can only use it for 400W or 3.6A. I did find a Battery Tender brand charger/maintainer that works at 3A. Now I know it would take forever to fully charge a fully discharged battery. I just thought it would be nice getting a tiny bit more charging in for the hours IM driving. So my question is:
Can I have my victron 150/45 charging at the same time as a 3A battery charger? WOuld they compete or conflict each other? The Battery Tender is a plug and play, I cant adjust any of its charging parameters.
A Good Question.
1) Your battery pack has a Max Input Amperage it can take... Typically, a 230AH battery can discharge @ 1C (230A) for 1 hour but only take 0.5C or 115A Charge for 2 hours max. It is generally better to charge LFP between 0.2C to 0.4C but that also depends on the class of cells in the battery pack.
2) As long as you do not exceed max charge capacity, the charge input sources are irrelevant to a point. You can have Solar + AC(grid/genset)->DC or other combo's as long as they do not collectively go above 0.5C.
3) The GOTCHA !
As LFP charges, Internal Resistance increases (as expected) which in turn decreases the amount of amperage the pack will take. Your EndAmps/TailCurrent for a 230AH Battery is 11.5A. Once the battery drops to taking 11.5A, they are about 95% full and the final 5% is to be completed with FLOAT (Constant Voltage / Variable Current) to top off and balance out the cells internally.
When charging from Multiple Sources the voltage settings (profiles) need to be identical so that the chargers respect each other. This includes taking into account voltage losses between devices. To work that out, you need a Very Good MultiMeter with at least 2 decimal place accuracy. Check the voltage @ the device terminals and at the battery pack terminals to determine "the" loss on that line. Compensate for the losses on the settings. IE: If charging @ 14.0V at the device terminal, the odds are the battery is getting 13.8 or 13.9, so you would up the charger to 14.2 or 14.1 to compensate. Each charge device needs to be checked, they will vary because of the wiring.
NOTE: Differentials also exist when discharging ! Look at the Inverter Terminals Voltage & Battery Terminals when discharging only... you will likely see 0.1 or 0.2V difference... adjust your Low Volt Discopnnect etc to compensate for that or you may discharge deeper than is good.
I am Offgrid Residential.
I can (and have) charged my battery bank with multiple sources concurrently.
- EVO Inverter/Charger pushing 80A
- Solar Controller pushing 79A
- External AC to DC Supplemental Charger pushing 50A
for a total of 209A to my bank (1680AH)
Remember that Battery Packs in Parallel divide & share Load & Charge proportionately.
Most important is to keep a reasonable & respectable charging profile that is not excessive to get the most from your batteries. Charging over 3.5V per cells gains you nothing other than High Volt Disconnects which handicaps your pack.
Hope it helps, Good Luck.
